2 114 500 en - (02)
Published by:
Bucyrus HEX GmbH Dept. 2470 – Documentation D-44149 Dortmund, Karl-Funke-Straße 36 Tel. +49 (0) 231 922-4340 Fax +49 (0) 231 922-5340 www.bucyrus-hex.com
TABLE OF CONTENTS
Foreword .................................................................................................................................. 1 Safety ........................................................................................................................................ 1 1.
Fund Fundam amen enta tals ls 1.1
Loads on structural elements .............................................................................................................. 2
1.2
Types of loading .................................................................................................................................. 2
1.3
Material behaviour under different loads .............................................................................................. 4
1.4
Notches Notches in comp compone onents nts
1.5
2.
3.
1.4.1
Mechanical notches .............................................................................................................. 5
1.4.2
Metallurgical notches ............................................................................................................ 6
1.4.3
Shape-induced notches ........................................................................................................ 6
1.4.4
Notch effects ........................................................................................................................ 8
1.4.5
Practical experience ............................................................................................................ 9
Avoiding Avoiding notch notches es 1.5.1
Grinding drag lines ............................................................................................................ 10
1.5.2
Grinding tools .................................................................................................................... 10
1.5.3
Run-off tabs ........................................................................................................................ 11
1.5.4
Attaching auxiliary elements .............................................................................................. 12
1.5.5
Ends of ribs ........................................................................................................................ 13
1.5.6
Undisturbed flow of forces .................................................................................................. 13
1.5.7
Ribs and stiffeners .............................................................................................................. 14
1.5.8
Welding technique .............................................................................................................. 15
1.5.9
Welding of "tempering beads" ............................................................................................ 16
1.5.10
Buffering of weld edges ...................................................................................................... 16
1.5.11
Welding sequence .............................................................................................................. 17
Planning Planning of repair repair and reinforcin reinforcing g work for steel steel compo component nents s 2.1
Causes of damage ............................................................................................................................ 18
2.2
Preparatory measures ........................................................................................................................ 18
2.3
Scope Scope of repair repair work 2.3.1
Scrapping of components .................................................................................................. 19
2.3.2
Temporary repair ................................................................................................................ 19
2.3.3
Permanent repair ................................................................................................................ 21
2.4
Precautionary examinations .............................................................................................................. 22
2.5
Detection Detection of cracks cracks and and othe otherr defec defects ts 2.5.1
Examination for surface cracks with the dye-penetration test ............................................ 22
2.5.2
Examination for surface cracks with the magnetic powder test .......................................... 22
2.5.3
Ultrasonic testing ................................................................................................................ 22
2.5.4
O&K standards for testing procedures ................................................................................ 22
Repair Repair weldin welding g techni technique ques s 3.1
Gouging out and welding of cracks .................................................................................................... 23
3.2
Cracks Cracks in hub conn connectio ections ns 3.2.1
Cr C racking along the center of the seam .............................................................................. 25
3.2.2
Sharp, exactly radial crack along the unchamfered edge .................................................. 26
TABLE OF CONTENTS 3.3
Welding on of a metal cylinder by the back-step technique ................................................................ 27 3.3.1
3.4
3.5
3.6
Cracks in box-type sections................................................................................................................ 29 3.4.1
Opening of box-type sections ............................................................................................ 30
3.4.2
Removing parts of a chord plate by flame-cutting .............................................................. 30
3.4.3
Backing strips .................................................................................................................... 33
Recommended Recommended groove shapes for manual manual welding with electrodes 3.5.1
Butt joints ............................................................................................................................ 34
3.5.2
T-joints ................................................................................................................................ 35
WORKING WORKING SEQUENCE SEQUENCE FOR WELD SEAMS SEAMS 3.6.1
3.6.2
3.7
4.
Butt welds .......................................................................................................................... 36 3.6.1.1
V-butt weld........................................................................................................ 36
3.6.1.2
Double-V butt weld .......................................................................................... 36
3.6.1.3
V-butt weld with backing strip .......................................................................... 37
T-joint.................................................................................................................................. 37 3.6.2.1
T-joints (fig. 53), accessible from 2 sides ........................................................ 37
3.6.2 .2..2
T-jo -joints with backing strip (fi (fig. 54), accessible from 1 side .............................. 37
Closing of working working openings, renewal of component component areas 3.7.1
Closing a working opening ................................................................................................ 38
3.7.2
Closing a web-plate opening .............................................................................................. 39
3.7.3
Replacing a chord-plate section ........................................................................................ 42 3.7.3.1
Salient chord plate ............................................................................................ 42
3.7.3.2
Recessed chord plate ...................................................................................... 45
3.7.3.3
Possible causes of damage to chord plates .................................................... 47
3.7.3.4
Repair of a boom with a salient chord .............................................................. 48
Reinfo Rei nforci rcing ng of steel steel compon component ents s 4.1
5.
Working sequence .............................................................................................................. 27
Reinforcin Reinforcing g plate plates s 4.1.1
Dimensions ........................................................................................................................ 49
4.1.2
Shapes of reinforcing reinforc ing plates .............................................................................................. 51
4.1.3
Welding slots ...................................................................................................................... 52
4.1.4
Fitting of reinforcing plates.................................................................................................. 53
4.1.5
Weld seams of T-joints ...................................................................................................... 53
4.2
Shaping plates for repairs .................................................................................................................. 54
4.3
Reinforcin Reinforcing g by shap shape e improveme improvements nts 4.3.1
End of ribs .......................................................................................................................... 55
4.3.2
Open sections/closed sections/ closed sections .......................................................................................... 55
4.3.3
Reinforcing Reinforci ng by build-up welding .......................................................................................... 56
4.3.4
Improvement Improvement of curved sections in ribs .............................................................................. 57
Materials, Materials, filler filler metals metals for welding welding 5.1
Materials in welded components ........................................................................................................ 58 5.1.1
5.2
O&K component materials .................................................................................................. 59
Filler metals metals for for O&K welded compone components nts depending depending on partner partner materials materials and welding techniques ...................................................................................................................... 62
TABLE OF CONTENTS
6.
Heat Heat treat treatme ment nt of materi materials als 6.1
Preheating for tacking, welding, gouging and flame-cutting flame-cutt ing .............................................................. 64
6.2
Hot bending of plates ........................................................................................................................ 69
6.3
Hot straightening of plates .................................................................................................................. 69
6.4
Stress-relief annealing annealing of steel componen components ts ...................................................................................... 69
6.5
Stress-reli Stress-relievin eving g of stee steell comp componen onents ts 6.5.1
Warming of components .................................................................................................... 70
6.5.2
Peening of weld seams ...................................................................................................... 70 6.5.2.1
Method of peening ............................................................................................ 70
6.5.2.2
Peening tools .................................................................................................... 71
6.6
Treatment of filler metals .................................................................................................................... 72
6.7
Temperature monitoring .................................................................................................................... 72
7.
Cold bending of plates .................................................................................................. 73
8.
Buil Buildd-up up weld weldin ing g 8.1
9.
Addition Add ition of missin missing g / worn-out worn-out mate material rial 8.1.1
Build-up welding in drill holes ............................................................................................ 74
8.1.2
Build-up welding on worn-out threads ................................................................................ 75
8.2
Correcting of componen componentt shapes to improve the flow of forces .......................................................... 76
8.3
Build-up welding as a protection protecti on against wear .................................................................................. 76
Wear Wear prote protecti ction on (hard(hard-fac facing ing)) 9.1
Fundamentals .................................................................................................................................... 77
9.2
Build-up welding of wear protection layers ........................................................................................ 77
9.3
9.4
9.2.1
Build-up welding patterns .................................................................................................. 78
9.2.2
Special hints ...................................................................................................................... 79
Filler Filler me metal tals s 9.3.1
For buffer layers ................................................................................................................ 79
9.3.2
For hard-facing layers ........................................................................................................ 79
Repair Repair of build-up build-up welds welds 9.4.1
State of wear ...................................................................................................................... 80
9.4.2
Identification of buffer and hard-facing layers .................................................................... 81
9.5
Repair of cracks in build-up welds ...................................................................................................... 82
9.6
Welding on wear-resistant steel plates or steel strips
9.7
9.6.1
Arrangement Arrangement of plates/strips .............................................................................................. 83
9.6.2
Bending of strips ................................................................................................................ 87
9.6.3
Working instructions .......................................................................................................... 87
9.6.4
Filler metals ........................................................................................................................ 87
Welding of plates or strips with wear-resistant coatings 9.7.1
9.8
Working instructions .......................................................................................................... 88
Welding Welding of wear-resis wear-resistant tant stud studs s 9.8.1
Working instructions .......................................................................................................... 89
TABLE OF CONTENTS
9.9
Welding cutting edges onto digging tools of excavators 9.9.1
Working sequence .............................................................................................................. 90
9.9.2
Welding sequence (fig. 39) and filler metals ...................................................................... 90
10. Repair of cast-iron components by welding 10.1 Spheroidal-graphite Spheroidal-graphite cast iron 10.1.1
Hot welding ........................................................................................................................ 92
10.1.2
Cold welding ...................................................................................................................... 92
10.2 Flaky-graphite cast iron 10.2.1
Hot welding ........................................................................................................................ 93
10.2.2
Cold welding ...................................................................................................................... 93
10.2.3
Repair of componen components ts with the "interlock" technique.......................................................... 94
11. Touching up paint coatings in repair areas ................................................................ 95
Appendix Comparison: old designation - new designation ................................................................ 96 Part nos. for filler metals........................................................................................................ 96 Conversion from foot (Fuß) and inch (Zoll) to metric measure .......................................... 99 Conversion for units of length .............................................................................................. 99 Temperature Temperature units and conversion formulas ...................................................................... 100 Hardness - strength comparisen ........................................................................................ 101
GENERAL
Foreword
Safety
In spite spite of prope properr desig design, n, perfec perfectt stress stress analy analysis sis,, meticulous manufacturing, attentive maintenance and responsib responsible le operatio operation, n, dam damage age to parts parts of building building machines mach ines and mob mobile ile indu industria striall han handlin dling g equi equipmen pmentt cannot always be completely avoided. Normal wear in areas subject to mecanical or abrasive action must always be reckoned with.
Always observe the accident prevention rules and safety regulations.
Experience in the early detection of damage and the causes thereof, the choice of appropriate repair measures and consisten consistent, t, workmanli workmanlike ke execution execution contricontribute to a high availability of construction machines.
•
Before beginning with welding, gouging, hot and cold bending and heat treatments, the person in charge of the repair must be familiar with the material of the component. The present Technical Handbook has been compiled from many useful hints supplied by welding experts as well as from experience gathered in the field of welding. They contribute to the proper planning and execution of repair and reinforcing work. It is taken for granted that the personnel in charge of this work possesses the required expert knowledge. Moreover, it is important to take the particulars of the respective case of damage into consideration. This latest edition of the Technical Handbook "Welding for maintenance and repair" SN 2 114 500.00 is a revise revised d and and upda updated ted versio version n and and tak takes es accoun accountt of EN standards. Some sections have been supplemented or added. For this reason, only the instructions in this edition should be observed for welding work.
Work Work on recip recipien ients ts conta contain ining ing or havin having g concontained substances •
•
that are combustible combustible or susceptible susceptible to stimulate combustion, that may be the cause of explosions and and which develop develop noxiou noxious s gases, fumes, fumes, mists or dusts during handling
must must only only be carrie carried d out out under under expert expert superv superviision and by experienced and specially qualified persons. Depres Depressur surize ize all circui circuits ts and compon component ents s (e.g. (e.g. pipeli pipelines nes,, cooler coolers, s, hydrau hydraulic lic oil tank, tank, comcompressed-air receivers) before opening them. For fitting and removing removing of working working equipment equipment or of components thereof, or for fitting and removing of units •
make sure sure that the machine machine and its equipment equipment are secur secured ed agains againstt unint unintent ention ional al and ununauthorized authorized starting. Place the working working equipequipment ment on the the grou ground nd so that that it cann cannot ot move move when mechanical mechanical or hydraulica hydraulicall connection connections s are opened or released.
•
make make sure sure that that equipm equipment ent or compon component ents s to be fitted, removed or brought into another position are secured against unintentional moving, ing, slidin sliding g or droppi dropping ng by means means of liftin lifting g tackle or suitable suspensions and supports.
Person Persons s workin working g at a consid considera erable ble height height must must be equi equipp pped ed with with a safet safety y harn harnes ess s to prev preven entt them from falling. If - for the execution of work - helpers, such as marshallers, are needed, it is essential to fix the responsibi responsibilities lities of the individual individual helpers beforebeforehand and to observe these responsibilities during the work in order to avoid any conflict of competence in safety matters. Make sure that all tools, lifting appliances, sling gear, supports and other auxiliary devices are in a safe and reliable state of operation. For further hints see para. 2.2 "Preparatory measures".
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FUNDAMENTALS 1.
1.1 1.1
Fundamentals
Load Loads s on struc structu tura rall eleme element nts s
Structural elements may be subject to different loads.
1.2 1.2
Typ Types of load loadin ing g
Loads (tensio Loads (tension n and com compre pressi ssion on forces) forces) may act upon the structural element as static or mainly static (fig. 2), pulsating (fig. 3) or alternating loads (fig. 4). Pulsating and alternating loads may occur either as continuous or as shock loads.
Forces practically never act as individual forces but mostly in combination (fig. 1).
Fig. 2 +F Tension O O-F Compression
Fig. 1
Loads on structural elements produced by forces acting simultan simultaneous eously ly and from diffe different rent directions directions are difficult to assess by computation.
Fig. 3
Modern computing methods nevertheless permit the determin dete rminatio ation n of stress stress mag magnitu nitudes des and concentra concentra-tions.
Fig. 4
2
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FUNDAMENTALS
The followin following g illust illustrat ration ions s (figs. (figs. 5 and and 6) give give an exampl exa mple e of differ differen entt typ types es of loads loads act acting ing on the boom boom of an exca excava vato tor. r. The The boom boom is stre stress ssed ed fo for r tension.
•
During During the "digg "digging ing"" cycle, cycle, the boom boom stretch stretches es out. The lower chord plate is subject to tension and the upper chord plate to compression.
•
During the "lifting" cycle, the boom is compressed. compressed. Now, the upper chord plate is subject to tension and the lower chord plate to compression.
This This me mean ans s that that the the load loads s act act alte altern rnat atel ely y on the the boom.
Fig. 5
Fig. 6
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FUNDAMENTALS 1.3
Materi Material al behavio behaviour ur under under differ different ent loads loads
The mechanical mechanical stresses stresses adm admissib issible le with regard to the operating safety of a structural element (N/mm2) vary for the same material under static and alternating loads (fig. 7).
The The reason reason for this this ma mater terial ial behavio behaviour ur lies lies in the gradual weakening of the cohesive forces along the grain boundaries, and, at a later stage, in the occurrence and increase of disturbances in the microstructure (fig. 8).
Fig. 8
1
Shows an an idealized idealized material material microstructure microstructure under alternating load. The material experiences elastic deformation along the sliding planes at the grain boundaries. The sliding planes present no disturbances.
2
Permane Permanent nt elastic deformatio deformation n leads to shifting shifting of material grains along the sliding planes where the first disturbances appear.
3
The disturbe disturbed d areas widen widen as the frequency frequency of elastic deformation increases.
Fig. 7
The admissible mechanical stresses are clearly below the values for tensile strength indicated in the standards. The example shows a rolled steel EN 10025 S355J2G3, with thicknesses _ > 3 mm _ < 100 mm.
4
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FUNDAMENTALS 1.4 1.4
Notch Notches es in comp compon onen ents ts
These notches may, however, also have other mechanical causes (fig. 10 and 11), such as:
All areas where the ideal flow of forces in a component is disturbed are qualified as notches.
steel stamping figures, chisel marks, marking tool lines, damage by lifting chains.
From their occurrence and their effect on the component 3 different types of notches have to be considered: -
1.4.1 1.4.1
mechanical notches metallurgical notches shape-induced shape-induced notches
Mechan Mechanica icall notche notches s
Mechanical notches may occur during welding in the weld seam (fig. 9).
Fig. 10
Fig. 11
1
Steel stamping figures
2
Chisel marks
3
Marking tool lines
4
Notches due to lifting chains
Fig. 9
1 Undercut 2
Incomplete joint penetration
3
Porosities in the weld deposit
4
Incomplete fusion
5
Grinding drag lines
6
Drop-through at the root
7
Underbead crack
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FUNDAMENTALS Mechanical notches lead to stress concentrations (fig. 12).
Due to their properties, these areas, however small they may be, show a different behaviour under loading which, in turn, leads to elon elongati gation on impe impedime diments nts and material constraints. The occurrence of metallurgical notches can be kept to an accep acceptab tably ly low level level by apply applying ing optim optimize ized d welding and heat-treatment heat-treatment techniques. The effect of existing metallurgical notches, e.g. those tho se produc produced ed by imp improp roper er weldi welding, ng, can also also be mitigated by a stress-relieving and annealing procedure.
1.4.3
Shape-indu Shape-induced ced notches notches
Shape-induced notches depend on the structural design and lead to stress concentrations caused by the diversion of lines of forces (fig. 14). Fig. 12
2
Inadequate Inadequa te penetration of root root
4
Incomplete fusion
Thes These, e, in turn turn,, lead lead to an en enla larg rgem emen entt of th the e notches. This procedure may repeat itself and eventually lead to fracturing of the component. Mechanical notches are mainly produced during the manufacture, but later on also during the utilization of the machine (traces resulting from use). Mecha Me chanic nical al not notche ches s can be detec detected ted by visua visuall inspection spection or by non non-des -destructi tructive ve testing and then be repaired.
1.4.2 1.4.2
In many cases, shape-induced notches are moreover locate located d in heat heat affect affected ed zon zones es with with me metal tallu lurgi rgical cal notches. Shape-in Shap e-induce duced d notch notches es can be largely largely reduced reduced by choosing an appropriate design. For all practical purposes, they have to be reduced to such an extent that the negative influence exerted by them on the endurance strength of the structural element remains insignificant.
Metall Metallurg urgical ical notche notches s
Metallurgical notches are caused by thermal influence on the material; i.e. always at or around weld deposits (fig. 13).
Fig. 13 Fig. 14
The heat applied by welding leads to zones presenting different metallurgical and mechano-technological prope properti rties es dep depen endin ding g on the their ir distan distance ce to the heat heat source.
6
1
+ 2
Hardness distribution curve
Shape-induced Shape-induc ed notche notches s can be subsequentl subsequently y eliminated by changes in shape.
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FUNDAMENTALS Examples (fig. 15): a + b: ina inade dequa quatel tely y exe execut cuted ed butt-w butt-weld eld joints joints bebetween structural elements of different thicknesses.
An ideal and yet cost-saving solution for the distribution of forces is the butt-weld joint where the plate thickness thickness difference difference is reduced reduced by cham chamferin fering g in a 1:4 ratio (fig. 16).
c: better joint. For relati relativel vely y sma smallll thickn thickness ess variat variation ions s of the two plates, the joint such as realized in example c) can be sufficient.
Fig. 16
The forces should be able to flow as disturbance-free as possible through the part of the structural element that can be analysed. Lines of forces should not, however, traverse auxiliary elements (fig. 17).
Fig. 15
Fig. 17
The welds used for fastening such auxiliary elements are mostly overestimated as they cannot absorb the forces prevailing in components
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FUNDAMENTALS 1.4.4 1.4.4
Notch Notch effec effects ts
Depen Dependin ding g on the their ir sha shape, pe, notch notches es have have diffe differen rentt notch or influencing factors.
Possible Possible notc notches hes (mechani (mechanical cal and meta metallurg llurgical) ical) in the seams of butt-weld joints:
The influence of notch factors on the fatigue strength of a component is shown in the graph (fig. 18).
For a notch factor of "O", practically the only effects to be expected are from metallurgical notches.
Fig. 18
Location and shape of curves W, O, 1, 2, 3 and 4 refer to: material:
EN 10025: S355J2G3
no. of load cycles:
2 ˙ 10 6 (2 million) i.e. of high fatigue f atigue strength
group of stress intensities: small, medium and and high stresses with approx. the same frequency
8
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FUNDAMENTALS 1.4.5 1.4.5
Practi Practical cal experi experienc ence e
In orde orderr to lowe lowerr the the weig weight ht of comp compon onen ents ts,, dedesigners often resort to materials with higher strength value values s and and to pla plates tes of lower lower thickn thickness esses es with with no changes to the shape of the component. In this respect it should not be overlooked, however, thatt the sta tha stabil bility ity of the structu structural ral ele elemen mentt only only dedepends pen ds on the ge geome ometric trical al dim dimens ension ions s and the modulus of elasticity E of the material. E is basically the same for an S690Q and an S355J2G3. This means that a comp compone onent nt consisting consisting of thin thinner ner plates plat es is subject subject to stronger stronger deformation deformations s and thus loses loses some of its service service propertie properties. s. Moreover Moreover,, the effects of notches on the strength of the materials are increased. High-stren High-strength gth fine fine-grai -grained ned structural structural stee steels ls such as S690Q S690 Q offe offerr adva advantag ntages es over ordinary ordinary fine fine-grai -grained ned structural steel S355J2G3 only in cases of static or predomin predominantl antly y static static load loading ing and reduced reduced notch notching ing (fig. 19). With the strength of the material increasing, the susceptibility of structural steel elements to notching becomes greater. For mac machin hines es sub subjec jectt to altern alternati ating ng loa loads ds an and d equipped with notched structural steel elements it is therefore recommended to use an S355J2G3.
Fig. 19
Location and shape of curves W, O and 4 refer to: In this context, notches resulting from marks left by usage have to be considered as well.
material:
S355J2G3, S690Q
no. of load cycles:
> _ 2 ˙ 10 6 (2 million)
group of stress intensities: small, medium and and high stresses with approx. the same frequency
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FUNDAMENTALS 1.5.2 1.5.2 1.5 1.5
Grind Grinding ing tools tools
Avoi Av oidi ding ng notc notche hes s Grinding wheel on angle grinder (fig. 21):
If notches in a component are avoided altogether or if their acuity (notch factor) is reduced, the admissible stresses (N/ (N/mm2) can be increased. In such case, the life of the component increases and damage s can be largely largely avoided.
1.5.1 1.5.1
Only suitable for the rough removal of material. Not suitable for low-notch finish with controlled grinding grooves . direction of grinding
Grindi Grinding ng drag drag lines lines
Grinding grooves transverse to the main direction of load are dangerous mechanical notches. Grinding grooves transverse t o the direction of loading (fig. 20) should therefore be avoided during grinding.
Fig. 21
Grinding stone (fig. 22): Suitab Suitable le for grind grinding ing of weld weld surfac surfaces, es, weld weld ends and plate edges. Should be used at least for finishing.
Fig. 22 Fig. 20
This rule cannot be observed if grinding wheels are used for the work. Under these circumstances, manual reworking with emery paper may be required. It is therefore recommended to use grinding stones at least for the finishing pass.
10
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FUNDAMENTALS 1.5. 1.5.3 3 Grinding stone (fig. 23): Suita Suitable ble for grind grinding ing in com compo ponen nentt areas areas of difficult access.
RunRun-of offf tabs tabs
Mechanical stresses reach their highest value at the edges of components. Defects in the weld which are caused, for instance, by arc strikes or end-of-weld craters in edge zones shou should ld be avoi avoide ded. d. The The weld weldin ing g groo groove ve mu must st be completely filled along the edges of components.
Fig. 23
Steel milling cutter (fig. 24): Suitable for rounding off small radii.
Fig. 25
For this purpose, the weld seam has to be extended by ca. ca. 50 mm usin using g runrun-of offf tabs tabs (fig (fig.. 25). 25). In this this case, arc strikes and end-of-weld craters are located in the extended part of the groove. The cross-section of the run-off tabs used depends on the shape of the welding groove. Fig. 24
After welding, the run-off sections are to be removed by flame-cutting and the surfaces to be finished by proper grinding. For such work, the grinding instructions given under 1.5. 1 should be followed.
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FUNDAMENTALS 1.5.4
Attaching Attaching auxiliary auxiliary elements elements
To protect the base element it may be required to work out alternative methods of fastening (fig. 28).
For the fas fasten tening ing of auxil auxiliar iary y ele eleme ments nts no weldi welding ng should be carried out in the edge zones of structural elements subject to high stresses. The welds should end at a well-defined distance from the edge of the component. Arc strikes and end-of-weld craters should be located as far away from the component edge as possible (figs. 26 und 27).
Fig. 28
Examples:
Fig. 26
•
Faste Fastenin ning g of pipe clamps clamps on a very very sma smallll base element.
•
Stirrups Stirrups for pipes, lamps, cables cables and similar fixtures tures faste fastened ned without without welding welding on the high highly ly stressed bottom chord.
Fig. 27
12
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FUNDAMENTALS 1.5.5 1.5.5
Ends Ends of ribs ribs
The ends of ribs ribs on hig highly hly stress stressed ed struct structura urall ele ele-ments must taper off "gently" and be surrounded by a boxing weld.
1.5.6 1.5.6
Undist Undisturb urbed ed flow flow of of forc forces es
Auxiliary elements - in this case a crane eye - must be shaped in such a way that the lines of force are not disturbed or even interrupted.
Fig. 30
Interr Interrup uptio tions ns in the flow flow of forces forces produc produce e stress stress concentrations and lead to cracks (fig. 31).
Fig. 29
The welder must position himself and the component in such a way that the boxing weld can be carried out without arc strikes and end-of-weld craters. The weld weld interf interface ace areas areas mu must st be abs absolu olutel tely y free free from notches. This can only be achieved by grinding (fig. 30).
Fig. 31
Recommendation: Cut off the the eyes after after assembly. assembly. Grind the surfaces smooth and clean.
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FUNDAMENTALS 1.5.7 1.5.7
Ribs Ribs and stiffen stiffeners ers
Ribs, stiffeners and similar parts on components must be welded with endless seams if the components are subject to pulsating or alternating loads (fig. 32).
Fig. 32
Interruptions in the weld seams are not recommended, even if they facilitate the assembly of the component (fig. 33). Tri-directional states of stresses in weld-seam crossings ing s are con consid sidera erably bly less less dan danger gerous ous for the structural structural elements elements than defective defective or even missing boxing boxing welds welds in the gaps. They represent represent pote potentia ntiall starting starting poin points ts for fatig fatigue ue fractures. fractures. Too large gap gaps s may lead to damage by "softening-up" the component corner, even if the weld is otherwise faultless.
14
Fig. 33
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FUNDAMENTALS 1.5.8 1.5.8
Weldin Welding g techniq technique ue
The effects of metallurgical notches can be considerably alleviated alleviated by appl applying ying a proper proper hand handling ling technique during welding.
Maximum bead or pass widths: Solid wire: Wire Ø 0,8 1,0 1,2 1,6
When repairing components by welding, the stringer bead technique must be used (fig. 34).
Width 8,0 10,0 12,0 16,0
Rod electrodes: Rod Ø 3,2 4,0 5,5
Width 8,0 10,0 12,0
The weld start points for multipass welding must run in terra terrace ces s (fig (fig.. 35) 35) or casc cascad ades es (fig (fig.. 36). 36). This This is essential if faults due to arc strikes or end craters are to be avoided on one line in the various passes. Illustrations: Fig. 34
The advantages of the stringer bead technique are: • Reduced Reduced heat input (joule/cm (joule/cm)) per welding welding bead. bead. The heat-affected zone (HAZ) in the base material remains remains very narrow, resulting resulting in a meta metallurg llurgical ical notch with minimum notch action. Heat input: (J/cm) = I x U x 60 v I = current intensity (A) U = voltage (V) v = welding velocity (cm/min) • •
Each welding welding bead bead is tempered tempered by the overweldoverwelding with the next bead. The weld pool can be well controlled, with good penetration at the weld edges, edges, avoidance of weld pool pool pre-flow (cold welding), welding), avoidance of poor poor fusion. -
Fig. 35
Fig. 36
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Page 15 Page 15
FUNDAMENTALS 1.5.9
Welding Welding of "tempering "tempering beads" beads"
The weldin welding g of "temp "temperi ering ng bea beads" ds" provid provides es a sub sub-stantial improvement in the mechanical-technological charac cha racter terist istics ics of the weld me metal tal both both in the cover pass pass and in the heat-aff heat-affect ected ed zon zone e (HAZ) (HAZ) close close to the surface.
1.5.10 Buffering Buffering of of weld edges edges The formation of heat-affected zones (HAZ) is vital to the durab durabili ility ty of the weld, weld, esp especi eciall ally y when when weldin welding g materials with a high carbon equivalent.
The aim must be: •
a narrow narrow heat-affected heat-affected zone (HAZ), (HAZ),
•
a min minimu imum m reduct reduction ion in the streng strength th of the material and of the heat-affected zone (HAZ),
•
a sligh slightt increa increase se in hardn hardness ess at the transiti transition on between the heat-affected zone and the base material.
This aim is largely achieved by so-called buffering of the weld edges prior to weld- joining. For buffering purposes, welding is done with the lowest possible heat input (J/cm). Fig. 37
Explanations of Fig. 37:
•
Weld the bufferi buffering ng with rod electrod electrodes es of the type suited to the base material.
•
Diameter of rod electrodes: 3.2 mm. mm.
•
Preheat the base material, material, depending depending on type. type.
In this this tem temper pered ed weld me metal tal,, an ide ideal al ma mater terial ial structure with improved expansion and toughness characteristics is induced with a negligible loss of strength.
•
Weld in stringer bead bead technique. technique.
•
Check the inter-pass inter-pass temperature temperature of the materials materials accordingly.
If necessary, the cover pass can be be ground down.
•
If run-off tabs are are present at the the weld ends: ends: buffer beyond the start point as far as the end of the run-off tabs.
•
Clean Clean the finished finished buffering buffering thoroughly thoroughly befo before re overweldi overwe lding ng.. (Slag (Slag residu residues es on the con contac tactt line line from one bead to the next).
•
Start the weld-joining weld-joining without intermediate intermediate cooling cooling of the component.
•
Beads 6 and 7 are are the "tempering "tempering beads".
•
The welding welding of beads beads 6 and 7 re-heats re-heats the weld weld metal of beads 1 and 3 / 4 and 2 respectively. The metal is tempered.
•
•
The following details must be observed when buffering:
When 2 separate components or fragments are to be joined by welding, buffering should be done prior to assembly in the most favourable welding position for both parts. Assembly of the warm parts must be scheduled before the heating, e.g. with an appropriate device.
16
2 en - (0)
FUNDAMENTALS 1.5.11 Welding Welding sequen sequence ce
When welding weld crossings, the welding sequence drawn below must be observed (fig. 38).
Definition: Stipulating in which direction a joint is to be welded and in what sequence several joints are to be welded. Explanation of drawing:
Presetting the welding sequence allows the following to be determined: •
The componen componentt must be kept as stress-reliev stress-relieved ed as possible. Delays due to the effect of welding stresses must be accepted.
•
The The com compo pone nent nt mu must st be kep keptt as dim dimens ension ionall ally y stable as possible. Intrinsic stresses in the component, resulting from the welding, must be accepted.
When repairing components by welding them, it will gener generall ally y be nec necess essary ary to kee keep p the com compo ponen nentt dimensionally mensionally stable.
2 en - (0)
Fig. 38
To avo avoid id defec defects ts and thu thus s to preven preventt me mecha chanic nical al notches, weld crossings in the edge zone of components must not have any arc strikes or end craters.
Page 17 Page 17
PLANNING OF REPAIR AND REINFORCING WORK 2.
Planni Planning ng of repair repair and reinfo reinforci rcing ng work for steel components
In pla planni nning ng the repair repair and reinfo reinforce rceme ment nt of ste steel el components, the first step should be to determine the precise extent and the causes of damage and then to fix and to carry out the appropriate measures. Reinfo Reinforce rcemen mentt witho without ut pla planni nning ng lea leads ds to new new dadamage.
2.1 2.1
•
In practi practice, ce, repair repair,, recons reconstru tructi ction on or reinfo reinforci rcing ng work work ma may y only only be carri carried ed out out by expe experi rien ence ced d welders. welders. A welder welder hold holding ing a certificat certificate e in accoraccordance with EN 287-1 135 P BW W03 t20 PC SS mk already already fulfils fulfils the basic qualificatio qualification n requirerequirements.
•
If possible, possible, welding welding is to be done in a workshop workshop which which is equi equipped pped with the nece necessary ssary tools and lifting gear.
•
If welding welding work has has to be carried out out on site, the component must be protected against atmospheric influences such as rain, snow, dew, wind, etc. This can be achieved, for example, by a tarpaulin used as a working tent.
•
Clea Cleanl nlin ines ess s at the the plac place e of work work is of utmo utmost st importance.
•
When Whe n dismant dismantlin ling g the com compon ponent ent,, all built-o built-on n parts, particularly those with articulations, must be removed from the component.
Caus Ca uses es of dam damage age
The causes of damage may be manifold. Dimensioning Dimensioning errors
•
Incorrect estimation of the potential stresses and load cases. Dimensioning and design errors. Unsuitable construction materials.
(Example: Tri-Power pin and and linkage). Manufacturing Manufacturing errors
•
Mechanical Mechanical and metallurgical notches. Measuring errors. Mixing up of materials. Material defects.
Hose and pipe connections opened opened in dismantling dismantling the component as well as open holes and casings should be closed carefully in order to prevent the penetration of dirt.
•
The The com compo ponen nentt to be repair repaired ed is to be clean cleaned ed properly, particularly those parts of the component on which work is to be carried out.
•
Weld grooves grooves and surfaces surfaces for fillet fillet welds must be completely cleaned down to the bare metal.
•
Pain Paintt coat coatin ings gs and and prim primin ing g coat coats s mu must st not not be welded over.
•
Lubricants Lubrica nts mus mustt be com comple pletel tely y remove removed d from bearings in order to prevent them from liquefying under the effect of heat and flowing into the weld area.
•
Machined Mach ined surfaces, surfaces, pins, pins, bea bearings rings,, piston piston rods, rods, electrica electr icall com compo ponen nents, ts, etc etc.. mus mustt be protec protected ted against weld splashes and grinding dust by covering them with non-combustible materials.
•
Befor Be fore e carryi carrying ng out weldin welding g on assem assembli blies es containing containi ng electron electronic ic comp compone onents, nts, all conn connector ectors s must be unplugged.
Wrong operation of the machine
•
Wrong handling due to lack of experience. Wrong use due to an overestimation of the machine’s capabilities. Using the machine for activities for which it is has not been designed. •
•
Accidents Accidents during transport, relocation or operation, e.g. accidents caused by falling rocks when working in quarries.
2.2 2.2
Prep Prepar arat ator ory y meas measur ures es
To restore the machine’s availability independent of the cause of damage, it is essential to fix the appropriate working procedure.
Example: Example: In hydraulic hydraulic excavato excavators rs equi equipped pped with the the PM PMS S syste system, m, all all conn connec ecto tors rs mu must st be ununplugged from the load-limit regulator (PMS box).
Important prerequisites for the execution of repair and reinforcing work: •
18
Repai Repair, r, recon reconstr struct uction ion or reinfo reinforci rcing ng work work on structural steel elements of construction machines may be supervised only by experts with sufficient experience in the design and construction of dynamically stressed componen components. ts. In cases of doubt, please address the O&K aftersales service which can refer the problem to the respective specialized departments, if required.
•
Prior to welding welding on components components remaining remaining on the the machine, the starter batteries must be disconnected. ed. Discon Disconne nect ct first first the negat negative ive and and the then n the positive positive terminal! terminal! After the work, reconnect reconnect first the positive and then the negative terminal.
•
Before welding, welding, the type and and the properties of the material involved must be determined.
•
Use only those those weld filler filler metals metals that are suitable suitable for the base metal concerned. 2 en - (0 )
PLANNING OF REPAIR AND REINFORCING WORK 2.3 2.3
Scop Scope e of repa repair ir work work
The most suitable procedure to be followed in a case of damage is shown in the diagram below. After damage has been reported, one of the 3 following decisions is to be taken (fig. 1).
2.3.2 2.3.2
Tempor Temporary ary repair repair
The component must be repaired immediately in order der to ma maint intain ain the ma machi chine ne’s ’s ava availa ilabil bility ity,, e.g e.g.. bebecause the machine is used for a job with fixed time limits (fig. 2). In spit spite e of bein being g a ma matt tter er of urge urgenc ncy, y, temp tempor orar ary y repairs must nevertheless be performed carefully in order to avoid new damage.
Fig. 1
2.3.1 2.3.1
Scrapp Scrapping ing of compo componen nents ts
The damage has reached such an advanced stage thatt a prope tha properr repair repair is eithe eitherr tec techn hnica ically lly no lon longe ger r feasible or linked with extremely high costs. The limit for this decision is not a fixed one. Whereas at home and in most industrialized countries the decision cision to scrap scrap is tak taken en relati relativel vely y early early,, it ma may y be necessary in other countries to carry out the repair because the procurement of a new part is difficult for various reasons and sometimes even impossible. The reasons for this situation may lie, for example, in the lack lack of foreig foreign n exchan exchange ge,, in hig high h custom customs s dutie duties, s, long delivery periods and extended standstill periods for the machine. Relatively low wage costs can also be a reason in favour of the repair.
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Fig. 2
Page 19 Page 19
PLANNING OF REPAIR AND REINFORCING WORK The following rules must be observed: Cracks must be be stopped by drilling when they are still relatively short (fig. 3). This measure ensures a reduction in the crack propagation speed. It does not, however, constitute a repair. •
One possibility of finding the end of a crack consists in non-destructive testing for cracks by means of one of the well-known methods such as ultrasonic testing, dye-pene dye-penetrati tration on test, magnetic magnetic powder powder test or X-ray testing. After drilling, the stopper hole can be examined for persisting cracks. •
Long Lon g cracks cracks shou should ld be imme immediat diately ely gouged gouged out and welded, welded, even if the marginal marginal cond conditio itions ns are unfavourable.
The area of damage must be subjected to permanent inspection. In case of a failure of the repair weld, the measure described has to be repeated. •
Do not weld reinforcin reinforcing g elements elements onto dam damage aged d areas. They not only make no sense, but moreover over cove coverr up the the area area of dama damage ge and and ma make ke permanent permanent checking impossible. Another possibility is that the area of damage may widen and thus make proper repair at a later time impossible.
Fig. 3
It is particularly important to find the actual end of the crack. Depen Dependin ding g on the their ir sta starti rting ng point point,, cracks cracks ma may y tratraverse the component along curved lines (fig. 4).
Fig. 4
A
+ B
C
incorrectly stopped by drilling drilling
20
correctly stopped by drilling
2 en - (0)
PLANNING OF REPAIR AND REINFORCING WORK 2.3.3 2.3.3
Perman Permanent ent repair repair
-
A simple examinati examination on of the material consists consists in com compa parin ring g its hardn hardness ess to tha thatt of kno known wn materials.
-
The The wall wall thick thickne ness ss of shee sheets, ts, cast cast-st -stee eell or forged pieces can be controlled and compared to the dimensions contained in the drawings.
-
In case of pe persisting rsisting doubt, doubt, the com component ponent can can be subjected to a new analysis carried out by a neutral institution.
-
In difficult cases, it is advisable advisable to make use of the servic services es of a lab labora orator tory y if, for exa examp mple, le, precise precise mat materia eriall ana analyse lyses, s, hardnes hardness s curves curves and an appraisal of the material’s microstructure and surface are required. In certain cases, the expertise of an independent laboratory may also be required in order to clear up liability matters.
•
In each phase of the work, all advantages at hand should be made use of.
Fig. 5
Even so-called "trivial matters" may be of decisive importance for the success of a repair.
If a decision in favour of a permanent repair of the damaged dama ged component component is take taken n (fig. 5), the following following rules are to be observed: •
The The repair repair work work mu must st be sub subjec jectt to superv supervisi ision on and the phases in which inspections are to take place be determined beforehand.
The The cau cause se of damag damage e mu must st be determi determine ned d and and eliminated if it can be traced back to design or manu ma nufac factur turing ing defic deficien iencie cies. s. To deter determin mine e the cause of damage, the following simple measures will often be sufficient: -
Person Personal al exp experi erien ence ce and com compar pariso ison n with damage patterns in similar components.
-
Visual Visual inspection inspection of the area of damage with with the the aim aim of find findin ing g th the e caus causes es fo forr th the e crac crack k starti sta rting ng poi point, nt, such such as mec mecha hanic nical al not notche ches, s, missing weld seams, insufficient root penetration, etc.
-
A workm workman anlik like e repair repair giving giving a high high fatig fatigue ue strengt strength h exp expect ectanc ancy y mus mustt be proper properly ly pla planne nned d and carefully executed on the workshop level.
Visual Visual appraisal appraisal of the fractured fractured surfaces surfaces with the aim of finding the crack starting point by means of the bench marks. Moreo Mo reover ver,, the struct structure ure of the fractu fractured red sursurface allows conclusions to be drawn with regard to material quality.
2 en - (0)
It is advisable to explain the theoretical reasons for the repair measure to the craftsman carrying out the work as he will then develop a feeling of responsibility for a successful achievement of the repair. •
In case of damage damage caused by design design failures failures or overloading, it may be necessary to reinforce the component after the repair. Important note Important note:: The reinforce reinforcemen mentt plan planned ned must make sense and its positive effects be justified by means of an analysis. Badly planned reinforcing measures are useless, expensive, do not offer real safety, increase the weig weight ht of the the comp compon onen entt and and ma may y impe impede de its its functions. Moreover, they do not look very nice.
Page 21 Page 21
PLANNING OF REPAIR AND REINFORCING WORK 2.4 2.4
Preca Precaut utio iona nary ry exami examina nati tion ons s
In the field of medi medical cal treatment, treatment, precautio precautionary nary examination amin ations s are stan standard dard practice. Doctors teach us that a disease, if discovered in its early stage, can be cured by a simple operation, whereas in an advanced stage, help often comes too late. The regular inspection of construction machines, for example, is also a kind of precautionary examination and part of the VBG guideline 40. Inspection procedure and follow-up measures: •
Cleaning of the machine.
•
Visual inspection inspection of critical component component areas. Recording of all findings.
•
Contactin Contacting g the manu manufactu facturer rer for a discussio discussion n of the inspection results.
•
Planning and execution execution of n necessary ecessary repairs. repairs.
•
Stockpiling of damage-prone damage-prone componen components. ts.
•
Stockpiling of wearing wearing parts.
2.5
Detecti Detection on of cracks cracks and other other defect defects s
4.
Spray Spray white white develo developer per (O&K-S (O&K-SN N 552 302) onto onto the area. Any cracks then become visible as small, red line lines s on a whit white e back backgr grou ound nd.. The The exte extent nt of "bleeding" and the waiting time allow conclusions to be drawn as to the depth of the crack. Wipe off the developer with a cleaning cloth.
2.5. 2.5.2 2
Exam Examin inat atio ion n for for surf surfac ace e crac cracks ks with with the the magnetic powder test
The magnetic powder test is suitable for the detection of crac cracks ks on the the surf surfac ace e of the the ma mate teri rial al and and for for cracks not deeper than 2 mm below the surface. The component is first magnetized and then sprayed with a liquid containing very fine iron particles (as fine as dust). The iron particles settle along the cracks and make them visible.
2.5.3 2.5.3
Ultras Ultrasoni onic c testin testing g
The ultrasonic test can be used for the detection of defects inside materials of more then 10 mm thickness and in weld deposits. Ultrasonic testing can only be performed by qualified testers. Qualifi lifica cati tio on:
Cert Certif ific icat ates es U 1 an and d U 2 of the "Deutsche "Deutsche Gesellsch Gesellschaft aft zur zerstorungsfreien ¨ Pr¨ufung" (DGZFP)*.
Cracks and other defects in plates, forged and caststee steell parts parts can can be dete detect cted ed with with th the e help help of te test st procedures:
2.5.4
2.5.1 2.5.1
Detail Detailed ed inform informati ation on on tes testin ting g proced procedure ures s can be found in the following O&K standards:
Exam Examin inat atio ion n for for surf surfac ace e crac cracks ks with with the the dye-penetration test
O&K standards standards for testing testing procedure procedures s
07 47 04, part 1 The dye-penetration test is the simplest procedure to detect cracks in the surface of the material. 1.
Carefully Carefully clean clean the the area area to be tested tested..
2.
Spray Spray red pen penetrat etration ion fluid (O&K-SN 1 044 915) onto the area and allow it to take effect for 5 to 10 minutes.
3.
Remo Remove ve red red pene penetr trat atio ion n flui fluid d with with a spec specia iall cleaner (O&K-SN 552 304).
Dye-penet Dye-penetratio ration n test, mag magneti netic c powder test
07 47 01, sheet sheet 1 Ultrasonic testing of welded welded joints 07 47 01, sheet sheet 2 Ultrasonic testing of cast-steel cast-steel and forged parts. The The O&K sta stand ndard ards s are ava availa ilable ble from from O&K DortDortmund mu nd,, Stan Standa dard rds s Dept Dept., ., in Engl Englis ish h or in Ge Germ rman an (please state desired language). * (German Society for Non-Destructive Testing)
22
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REPAIR WELDING TECHNIQUES 3.
Repa Re pair ir weld weldin ing g tech techni niqu ques es
The repair of a structural component by welding require quires s workin working g met metho hods ds which which do not not have have to be applied when the steel component is manufactured. Many of the methods represented have been developed lop ed on the basis basis of numer numerou ous s ind indivi ividu dual al exp expereriences and are field-proven.
3.1 3.1
Goug Gougin ing g out out and and weld weldin ing g of crac cracks ks
The method best suited for gouging out of cracks is the so-called "ARC-AIR procedure" (fig. 1). Fig. 2
A
Visible crack
B
Damage at the grain boundaries boundaries
If the the crac crack k is acce access ssib ible le from from both both side sides s in outoutof-pos of-positi ition on work, work, goug gouging ing sho should uld first first sta start rt on the lower side (fig. 3) with the depth of the groove being approx. 1/3 of the material thickness.
Fig. 1
An arc is struck between a carbon electrode and the material to be removed, and a jet of compressed air directed towards the arc blows away the molten base metal. For part part nos. nos. of "ARC-A "ARC-AIR IR carbon carbon ele electr ctrod odes" es" see Appendix. Another gouging method consists in gouging with oxy-gas or with grooving electrodes. It is important to start gouging at the end of the crack and to proceed towards the edge of the component. Proceedin Proceeding g in reverse reverse order may enlarge the crack due to thermal effects. It can be taken for granted that the crack has already progressed along the grain boundaries of the material where it cannot yet be detected visually or by other test procedures (fig. 2). Gouging should therefore not start at the end of the crack but shortly before the crack begins. For gouging, preheat the cracked area (cf. 6.1). After thermal gouging, the weld groove is to be reworked by grinding.
Fig. 3
Weld this side first. The crack is then gouged out from the more easily access accessibl ible e uppe upperr side side down down to the sea seam m alread already y welded from the lower side. As a final step, the weld is finished on the upper side (fig. 4).
The The surfa surface ces s mu must st be clea cleane ned d down down to th the e bare bare metal. 2 en - (0)
Page 23 Page 23
REPAIR WELDING TECHNIQUES
If this procedure is not respected, it may happen that areas of material between the cracks break away and that the gaps thus produced cannot be closed. The same applies to long cracks where gouging out and and weldin welding g sho should uld equa equally lly be done done ste step p by ste step. p. (fig. 6).
Fig. 4
So-called So-called "weld-pool "weld-pool backing backing strips" strips" shou should ld not be used used if weld weldin ing g from from both both side sides s is poss possib ible le,, as a backing strip in the root area of the weld represents a mechanical notch (shape-induced notch).
Ramified cracks Ramified Ramified cracks shou should ld be goug gouged ed out and welded welded step by step (fig. 5).
Fig. 6
During cooling of the partial welds, the surrounding cold areas prevent excessive welding shrinkage and distortion of the component.
Fig. 5
24
2 en - (0 )
REPAIR WELDING TECHNIQUES 3.2 3.2
Crac Cracks ks in hub hub conn connec ectio tions ns
Fig. 7 shows the connection of a hub to a box-type section which is accessible only from one side.
A possible cause cause is a broken broken fillet-weld backing. Counter-measures: Gouge out the crack carefully (fig. 9). Weld the gouged joint (fig. 10). Gouge out the web plate (2) in the area of the fillet-weld backing round the hub (1) and down to its collar (fig. 10). Weld the gouged joint (fig. 11).
Fig. 7
1
Hub
2
Web plate
3
Square-edge Square-edge butt joint
4
Fillet-weld backing, welded welded before before closing of the box-type section.
Fig. 9
The weld is characterized by a fillet-weld backing on the outer edge and the chamfered web plate. The following defects may occur:
3.2.1
Cracking Cracking along the center center of the the seam seam (fig. (fig. 8)
Fig. 10
Fig. 11 Fig. 8
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Page 25 Page 25
REPAIR WELDING TECHNIQUES 3.2.2 3.2.2
Sharp, Sharp, exactl exactly y radial radial crack crack along along the unchamfered edge
A possible cause is a lack of fusion in the unchamfered edge of the joint (see arrow in fig. 12).
Fig. 14
Fig. 12
Counter-measures: Gouge out the crack carefully (fig. 13). Weld the gouged groove (fig. 14).
Fig. 13
26
2 en - (0)
REPAIR WELDING TECHNIQUES 3.3
Welding on of a metal tal cyl cylinder by by the the back-step technique
3.3.1 3.3.1 1.
The follow following ing exa examp mple le descr describe ibes s the weldin welding g of a machined cylinder onto an undercarriage.
Workin Working g sequen sequence ce
Posit Position ion and and align align the cylind cylinder er in accord accordanc ance e with the drawing. Tack the cylinder solidly on the outside and carry out a dimensional check after tacking.
Welding by the back-step technique can always be employed where as distortion-free a weld as possible is required. This applies to circumferential seams as well as to longitudinal longitudinal seams. Fig. 15 shows how to execute the weld between the web plate of the cylinder and the base plate.
Fig. 17
2.
Weldi We lding ng of the 1st pass pass from from the inner inner side side of the cylinder (fig. 17). For this work use rod electrode Ø 3.20 mm. Weld in accord Weld accordan ance ce with with the backback-ste step p proceprocedure, step length: approx. 250 mm
Fig. 15
A
Outer side of cylinder
B
Inner side of cylinder
Fig. Fig. 18 show shows s an exam exampl ple e for for the the back back-s -ste tep p technique.
Welding is carried out in the normal operating position. Welding position: horizontal Correct Correct position positioning ing of the electrode electrodes s avoids avoids defe defects cts from incomplete fusion (9, fig. 16) at the web plate edges.
Fig. 18
Fig. 16
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Page 27 Page 27
REPAIR WELDING TECHNIQUES 3.
Grind Grind weld joint clean working working from the cylinder cylinder outside. Remove any slag residues from the 1st pass and completely grind out any cracked tack welds.
5.
Complete the the joint on the cylinder inside inside (fig. 20). Rod Rod elect electrod rode e 5th 5th and and 6th pass: pass:
Ø 4 or 5 mm.
Weld seams as described under 4.
Do not weld over cracked tack welds!
Fig. 20 Fig. 19
6. 4.
Weld the full full seam on the cylinder cylinder outside. outside. The example in fig. 19 shows a cylinder wall thickness of 15 mm. For other plate thicknesses, the buil buildd-up up of the the weld weld has has to be plan planne ned d and and executed accordingly. Rod electrode 2nd pass: Rod ele electro ctrode de 3rd and and 4th pass: pass:
There e mu must st be no unde underc rcut uts, s, weld weld me meta tall 6.1 Ther pores, arc strikes, end craters, spatter particles, slag, etc.
6.2 Carry out a dye-penetration test of the surface face whic which h mu must st be abso absolu lute tely ly free free from from cracks.
Ø 3.20 mm Ø 4 or 5 mm
Weld all beads in the back-step procedure and stag stagge gerr star starti ting ng and and end end poin points ts of each each new new layer.
Clean the weld seams seams and check check for defects. defects.
7.
Check the dimensions. dimensions. Irregularities Irregularities in the plane plane of the cylinder flange must not be levelled by the applicat app lication ion of hea heatt (danger (danger of distortion distortion due to weld-induced weld-induced residual stresses).
Example:
28
2 en - (0)
REPAIR WELDING TECHNIQUES 3.4 3.4
Crac Cracks ks in boxbox-ty type pe secti section ons s
Gouging and welding of cracks only from the outside cannot be recommended. recommended. Welding without backing strips usually leads either to an incomplete filling of the root area or to a dropthrough at the root (fig. 21).
Fig. 21
In both both cases, cases, the mechan mechanica icall notch notches es in the root area will lead to the formation of new cracks. Welding on backing strips introduced through the joint can equally not be recommended (fig. 22). Fig. 22
The backing strips will not come to rest properly on the base metal. Flashes and slag residues on the under-side cannot be removed. The result resulting ing me mecha chanic nical al not notche ches s will will cau cause se new damage.
2 en - (0)
Page 29 Page 29
REPAIR WELDING TECHNIQUES 3.4.1
Opening Opening of box-type box-type sections sections
If the the crac crack k is acce access ssib ible le only only from from one one side side,, an access opening has to be created from the second side. This can be done by opening the component in areas not subject to high stresses (figs. 23 and 24).
Practical hint: Ribs Ribs are are ofte often n visi visibl ble e on the the reve revers rse e side side of the the plates. Especially on painted surfaces they are clearly visible. Gouge out the crack first from the inside (over 1/3 of the plate thickness) and weld. Continue on the outside and then reclose the box-type section.
3.4.2 3.4.2
Removi Removing ng part parts s of a chord chord plate plate by by flameflamecutting
Figures 25 to 30 show how a box-type section can be op open ened ed in a way way whic which h do does es no nott affe affect ct the the remaining parts of the component. The section (1, fig. 25) of the top chord (2) is to be removed.
Fig. 23
Fig. 25
Cut a pilot hole in the chord plate (2, fig. 26) behind the web (3) with a flame (4). Flame-cut in longitudinal direction and as closely as possible to the web plate. Cutting Cutting must be carried carried out without without producin producing g drag lines in the web plate. Fig. 24
In larger larger com compon ponen ents ts the there re may also also be openi openings ngs allowing access to the interior of the component. The size of access openings is approximately 500 mm x 500 mm. If the internal structure of the component is unknown, it is advisable to contact the design department. A drawing showing the location of possibly existing stiffening ribs inside the box-type section should be at hand. Otherwise it may be necessary to cut out small spyholes in order to find out the areas in which repair openings of sufficient size can be created. Fig. 26
30
2 en - (0)
REPAIR WELDING TECHNIQUES
Sever the remaining strip of the chord plate (5, fig. 27) by flame-cutting from the inside.
Fig. 27
Flame-cu Flame-cutt the welding welding cham chamfer fer required required for welding welding the new chord plate section (fig. 28).
Cutting as in fig. 30 leads to unnecessary damage of th the e web web plat plate e (3, (3, fig. fig. 30) 30) (5 = dama damage ged d area area / flame-cut area).
Fig. 30
Welding on backing strips Opening Open ings s cut into into com compon ponen ents ts in order order to gain gain access to the under-side during the welding of cracks must be carefully reclosed in a workmanlike manner. Weldin Welding g of the compon component ent is carrie carried d out out from from one one side on backing strips (fig. 31).
Fig. 28
Make the transverse cut in the chord plate by proceeding from the web plate towards the center and not - as shown in fig. 29 - from the center towards the web plate (3). Fig. 31
The geometry of the weld and the welding sequence shown are to be carefully observed. Only then can a welding seam with a relatively low root notch factor be expected. It goes without saying that the root notch factor of such a welding seam has to be compatible with the selected component area. This must be examined before opening the component.
Fig. 29
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Page 31 Page 31
REPAIR WELDING TECHNIQUES
The same app applie lies s bas basica ically lly also also to the weldi welding ng of T-joints (fig. 32).
Fig. 34 Fig. 32
The same working method can also be employed if plates plat es of diffe different rent thicknesses thicknesses are welded welded (figs. (figs. 33 and 34).
If the joint joint is large largerr tha than n requir required, ed, weldin welding g sho should uld start with a build-up weld on one of the seam edges in order order to avo avoid id excess excessive ive transv transvers erse e shrink shrinkag age. e. After depositing the build-up weld, the gap between the seam edges can be completely closed (fig. 35).
The method shown in fig. 33 is, no doubt, the better solution. Chamfering of the thicker plate in a 1 : 4 ratio.
Fig. 33
The welding joint must in no case be too narrow, as the planned welding sequence can otherwise not be observed.
32
Fig. 35
This applies equally to the welding of T-joints with too large a groove. 2 en - (0 )
REPAIR WELDING TECHNIQUES 3.4.3 3.4.3
Backin Backing g strips strips
Backing strips are mostly made of flat steel 30 x 6 or 25 x 4 (fig. 36).
Fig. 37
Fig. 36
Backing strips for non-linear weld seams are flamecut out of pla plates tes with with the corres correspo pondi nding ng thickn thickness ess (fig. 37) or welded together from pieces of flat steel (fig. (fig. 38). 38). The The joints joints (fig. 38) mu must st be welde welded d and and ground from both sides.
Fig. 38
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Page 33 Page 33
REPAIR WELDING TECHNIQUES 3.5 3.5
Reco Re comm mmen ende ded d gro groov ove e sha shape pes s for for manu manual al welding with electrodes
For repairs or welding work carried out in the field, the following following weld groove groove conf configur iguratio ations ns shou should ld be preferred. These These groove groove con config figura uratio tions ns can be em emplo ployed yed for plat plate e thic thickn knes esse ses s up to 30 mm mm.. The The dime dimens nsio ions ns shown in the drawings are applicable up to this thickness. For gas metal-arc welding, the weld preparation angle can be reduced to 45 o. For greater greater plat plate e thickness thicknesses, es, the weld preparation preparation angles must be reduced so as to leave a maximum opening width of abt. 30 mm. Except for the sharpedge edge seam seam,, all all groov grooves es shou should ld be goug gouged ed out, out, ground and counter-welded, if possible.
3.5.1 3.5.1
Fig. 41
Butt Butt join joints ts
Recommended weld groove shapes: -
V-butt weld (fig. 39) Double-V butt weld weld (fig. 40) Single-bevel butt weld weld (fig. 41) Double-bevel Double-bevel butt butt weld (fig. 42) 42) Square-edge Square-edge butt butt weld (fig. 43) 43)
Fig. 42
Fig. 39
Fig. 43
Fig. 40
34
Welding technique
Symbol EN 24 063
Opening angle ß
E
111
60
MAGM
135
45
Solid wire
136
45
2 en - (0)
REPAIR WELDING TECHNIQUES 3.5.2 3.5.2
T-jo T-join ints ts
Recommended weld groove shapes: -
Single-bevel butt weld weld (fig. 44) Double-bevel Double-bevel butt butt weld (fig. 45) 45) Square-edge Square-edge butt butt weld (fig. 46) 46)
Fig. 45
Fig. 44
Fig. 46
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Page 35 Page 35
REPAIR WELDING TECHNIQUES 3.6 3.6
WORK WORKIN ING G SEQU SEQUEN ENCE CE FOR FOR WELD WELD SEAMS
3.6.1 3.6.1
Butt Butt weld welds s
+
easily accessible side
-
poorly accessible side
3.6.1.2 Double-V Double-V butt weld (fig. 49) Seam accessible from 2 sides
3.6.1.1 V-butt weld (fig. 47)
Fig. 49
A
Joint prepared
B
Joint welded overhead
C
Root gouged out
D
Seam welded
Fig. 47
A
Joint prepared
B
Joint welded
C
Root gouged gouged out from the under-side under-side
D
Root capped
Doub Doublele-V V butt butt weld weld (fig. (fig. 50). 50). Seam Seam access accessib ible le from 2 sides after turning of the component
V-but V-buttt weld weld (fig. (fig. 48). 48). Seam Seam access accessib ible le from from 2 sides after turning of the component
Fig. 50
Fig. 48
A
Joint prepared
B
Joint welded
C
Plate turned, root gouged gouged out
D
Root capped
36
A
Joint prepared
B
Root welded
C
Plate turned, root gouged gouged out
D
Seam welded
2 en - (0 )
REPAIR WELDING TECHNIQUES 3.6.1.3 V-butt weld with backing strip
3.6. 3.6.2 2
V-butt V-butt weld with backing strip 25x4 (fig. 51). Seam accessible from 1 side
3.6.2.1 T-joints T-joints (fig. 53), accessible from 2 sides
Fig. 51
T-jo T-join ints ts
Fig. 53
A
Backing strip attached
A
Web and chord chord plates plates tacked tacked
B
Joint prepared prepared and 1st root bead bead welded welded
B
Single-bevel Single-bevel weld deposited
C
2nd root bead welded
C
Root gouged out
D
Seam welded
D
Seam welded
V-butt V-butt weld with backing strip 30x6 (fig. 52). Seam accessible from 1 side
3.6.2.2 T-joints with backing strip (fig. 54), accessible from 1 side
Fig. 52
Fig. 54
A
Weld-backing strip attached
A
Backing strip welded
B
Joint prepared
B
1st root bead welded
C
Joint gouged out (grinding) (grinding)
C
2nd root bead welded
D
Seam welded
D
Seam welded
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Page 37 Page 37
REPAIR WELDING TECHNIQUES 3.7 3.7
Clos Closin ing g of of work workin ing g ope openi ning ngs, s, ren renew ewal al of of component areas
Openings (fig. 55) should be as small as possible but as large as necessary in order to allow the unimpeded use of tools.
Weld seams [2] and [3] alternately and use the socalled "back-step procedure" for the long seams. Back-step welding:
Experi Experien ence: ce: Op Open ening ings s 300 300 mm lon long g and and 200 200 mm high are normally sufficient.
3.7.1 3.7.1
Closin Closing g a workin working g open opening ing
Weld seam [4] in the same way as seam [1].
Fig. 55
The following example (fig. 55) is suitable for plate thicknesses up to 25 mm. Fig. 56 shows a backhoe stick. The diagram of moments clearly shows the areas of highest loads and thus of greatest stresses. Seam [1] is therefore the seam that lies in the area of high chord stresses. Weld seam [1] from the middle outwards to the left and and right right to the mid midpo point int of the corne cornerr curvat curvature ures. s. Finish upper beads or passes approximately 15 mm befor before e reachi reaching ng the end end of the und underl erlyin ying g bea bead d or pass. Allow the completed weld seam to cool down to approximately + 50 oC.
38
Fig. 56
2 en - (0)
REPAIR WELDING TECHNIQUES 3.7.2 3.7.2
Closin Closing g a web-pl web-plate ate openi opening ng
Fig. 59
4. Fig. 57
1.
At the web-plate web-plate (2, (2, figs. 57 + 58), chamfer chamfer the edge edges s to be welde welded d with with app approx roxima imatel tely y 10o. Width b of the chamfer in reldition to the plate thickness can be seen in fig. 70, page 42.
Prepare backing strip (3) from flat steel 30 x 4 bent on edge or burn out of 4 mm thick plate. Do not tack-weld backing strips from flat-steel bars for lack of cover at the rounded corners. Attach Atta ch backing backing strip (3) to the web plate plate (2) by means of screw clamps (fig. 60). Do not tackweld weld but but rath rather er weld weld with with a 3 mm fill fillet et seam seam running all around (fig. 61).
Fig. 60
After welding welding the fillet seam, clean the contact surface for the cover plate by removing all traces of weld spatter (arrow, fig. 61).
Fig. 58
2.
Gouge out out the longitudinal longitudinal seams between between chord plate (1) and web plate (2) over a distance of approximately 100 mm (fig. 58).
3.
Attach Attach backin backing g strip strip (3, fig. fig. 59), 59), but onl only y to the web-plate edges.
Fig. 61
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Page 39 Page 39
REPAIR WELDING TECHNIQUES 5.
Prepa Prepare re cover plate plate (5, fig. 62) for the repair repair open opening ing.. For For this this purpo purpose, se, use a new plate plate of the the same same thic thickn knes ess s and and cham chamfe ferr as show shown. n. Width (b) can be seen in fig. 70, page 42.
Fig. 62
6.
Atta Attach ch cove coverr plat plate e (5, (5, fig. fig. 63) 63) and and chec check k fo for r perfect weld joints. The cover plate must be in full-face contact with the backing strip. In case of distortions due to welding, the backing strip has to be straightened.
Press Press cover cover pla plate te (5, fig. fig. 64) again against st backi backing ng strip by using screw clamps. In workshops, this can be done with box-type section widths of up to 1.5 m.
Fig. 64
If the use of screw clamps is not possible, the cover cover pla plate te sho should uld be fas fasten tened ed by so-cal so-called led "hold-do "hold-down wn strips" (6, fig. 65). Attach the hold hold-down strip (6) to the web plate (2) with a fillet weld. Fix the cover plate (5) by driving wedges (7) between plate and strip. After welding of the cover plate, remove holddown strips by flame-cutting. Grind welded areas smooth and clean. Do not knock off hold-down strips with a hammer.
Fig. 63
Fig. 65
40
2 en - (0)
REPAIR WELDING TECHNIQUES 7.
Weld on on cover plate (fig. (fig. 66).
Fig. 66
Fig. 67
It is essential to observe the welding sequence shown. The symbols used have the following meaning:
Weld seam [1] approximately to the midpoint of the corner curvature. Place the first bead exactly betwe between en cover cover pla plate te (5) and and backi backing ng strip strip (3). (3). The upper bead must end approximately 15 mm befo before re the the end end of th the e unde underl rlyi ying ng bead bead.. Afte After r welding of seam [1], the cover plate may shrink. Procee Proceed d by weldin welding g sea seams ms [2] and and [3]. [3]. Ma Make ke sure that the seams inte interlock rlock properly properly with the ends of seam [1] (prepare by grinding). Weld the other ends through to the chord plate. The end of seams [2] and [3] at the chord plate are to be ground as shown in fig. 66, so as to obtain the same same shap shape e of the the weld weldin ing g join jointt as th the e one one between web and cover plate. Finish Finish the sequ sequence ence by welding welding seam [4]. The ends of welds [2] and [3] must not come to lie against aga inst interruption interruptions s or starting starting points of seam [4]. [4]. If possi possible ble,, weld weld sea seam m [4] with with con contin tinuo uous us stringer beads from one end to the other. Finish by grinding the surfaces of seams [1], [2], and [3] flush with the adjacent plates (fig. 67).
2 en - (0)
Page 41 Page 41
REPAIR WELDING TECHNIQUES 3.7.3
Replacing Replacing a chord-plat chord-plate e section section
1.
3.7.3.1 Salient chord plate
Chamfer welding bevels at 10o. Width b (fig. 69) can be read from fig. 70 below.
PLAT PLATE E THIC THICKN KNES ESS St
CHAM CH AMFE FER R WIDT WIDTH Hb
8 10 12 15 20 25 30 35 40 45 50
2,0 2,0 2,5 3,0 3,5 4,5 5,5 6,5 7,0 8,0 9,0
In a box-type section with 2 web plates (fig. 68), a chord-plate section is to be replaced by a new one.
Fig. 70
2.
Work out the long longitudi itudinal nal seams seams between between web plate (2, figs. 68 + 69) and chord plate (1) over a length of approximately 100 mm from the point at which the new piece is to be fitted.
Fig. 68
Fig. 71
Fig. 69
42
2 en - (0)
REPAIR WELDING TECHNIQUES 3.
Attach Attach backing backing strips (3, 4, figs. figs. 72 + 73) at the two remaining ends of the chord plate (1). Fit the plates properly and without any gaps.
5.
Weld We ld the the back backin ing g stri strips ps (3, (3, fig. fig. 75) 75) with with fill fillet et seams to the web plates (2).
Fig. 75 Fig. 72
6.
Tack-weld Tack-weld backing backing strips strips (4, fig. 76) to the outer outer side of web and chord plates.
Fig. 73
For the backing strips (3,4) use flat steel 25 x 4 mm.. Fit backi mm backing ng strip strip (3) exactly between between the two web plates (2). Adapt external backing strips (4) to the joints of the web plates (2) and allow them the m to ext exten end d ou outwa twards rds by ap appro proxim ximate ately ly 30 mm.
4.
Fig. 76
7.
TackTack-wel weld d run-of run-offf tab tabs s (5, fig. 77) to backi backing ng stri strips ps (4). (4). Cf. Cf. also also the the sect sectio ion n "End "Ends s of butt butt welds".
TackTack-wel weld d bac backin king g strips strips (3) bet betwe ween en the web plates pla tes.. If distor distortio tion n occurs occurs due to weldin welding g (fig. (fig. 74), the backing strips have to be straightened.
Fig. 77
Fig. 74
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Page 43 Page 43
REPAIR WELDING TECHNIQUES 8.
Fit the new new piece of chord chord plate (6, (6, fig. 78). The old piece of chord plate previously removed must not be used again. Make sure that the new piece of plate rests properly on its support.
10. Weld in the new piece of chord plate by strictly observing the welding sequence shown (fig. 80). The symbols have the following meaning:
Seam [1]
-
transverse seam in the area subject subject to high chord-plate chord-plate stress stresses. es. Weld Weld sea seam m com com-pletely.
Seam Seams s [2] [2] + [3] [3]
-
weld weld long longit itud udin inal al seam seams s in the directio direction n ind indicat icated ed by the arrows.
Seam [4]
-
weld tra transverse seam completely.
Seam Seams s [5] [5] + [6] [6]
-
weld weld long longit itud udin inal al seam seams s in the directio direction n ind indicat icated ed by the arrows.
Fig. 78
9.
Weld the Weld the two two fill fillet et seam seams s (fig (fig.. 79) 79) as show shown, n, without interruptions and without any tack points.
Weld seams [1] and [4] with stringer beads and continue the weld onto the 50 mm long run-off tabs (4). Remove the run-off tabs after welding with a clean cut.
Fig. 79
The surfaces of the transverse seams must be ground clean and flush with the adjacent plates. Work out properly the longitudinal seams in the area of the transverse seams. The grinding drag lines must run parallel to the longitudinal lines of force. force. If possible possible,, the transverse transverse seam seams s shou should ld be subsequently subjected to ultrasonic testing. Practical hint: In welding the longitudinal seams [2] [3] [5] and [6] there must be no welding starts or stops in the area of the transverse seam (backing strip).
Fig. 80
44
2 en - (0)
REPAIR WELDING TECHNIQUES 3.7.3.2 Recessed chord plate
2.
The following example shows how to fit a new recess cessed ed piec piece e of chor chord d plat plate e by weld weldin ing g it into into a box-type section with 2 web plates (fig. 81).
Work out longitudin longitudinal al seams between between web plate (2, fig. 83) and chord plate (1) over a distance of approximately 100 mm beyond the cutting edge of the chord plate.
Fig. 83 Fig. 81
Working sequence:
3.
Attach Atta ch backing backing strips strips (3, figs. 84 + 85) to the two remaining ends of the chord plate (1). For the backing strip (3) use flat steel 25 x 4 mm. Fit in backing strip (3) properly and without any gaps between the two web plates (2).
Fig. 82
1.
Chamfer Chamfer welding welding bevel bevel at 15o. Width (b, fig. 82) can be taken in fig. 70, page 42. Fig. 84
2 en - (0)
Page 45 Page 45
REPAIR WELDING TECHNIQUES 5.
Weld We ld in new new piec piece e of chor chord d plat plate e by stri strict ctly ly observing the welding sequence shown (fig. 87). As to the welding of the seams, cf. 10 on page 44.
Fig. 85
4.
Tack backing backing strips strips (3) between the web plates plates (fig. 85 + 86). If there is any distortion due to welding, the backing strips have to be straightened.
Fig. 87
Fig. 86
46
2 en - (0)
REPAIR WELDING TECHNIQUES 3.7. 3.7.3. 3.3 3 Possible Possible causes causes of damage damage to chord chord plates
Reason for the damage:
The followin following g fau faults lts ma may y occur occur in cho chord rd pla plates tes of box-type sections:
There are non-metallic inclusions from the pool (segregati regation on def defect ects), s), distri distribut buted ed ove overr the entir entire e pla plate te dimension, at the centre of the plate.
1.
Measures:
Transv Transvers erse e cracki cracking ng
The chord plate may crack open transverse to the component in the chord plate.
The plate cannot be repaired by welding. For durable repairs, the damaged plate must be replaced. It is to be assumed that areas of the plate not not yet cracke cracked d open open would would eve eventu ntuall ally y also also crack crack open as a result of the dynamic stress on the component.
3.
Longi Longitud tudina inall cracki cracking ng
The chord plate may crack open in longitudinal direction tion of the the comp compon onen entt para parall llel el to the the edge edge of the the plate (fig. 90).
Fig. 88
Reason for the damage: Expansion of the component obstructed by non-optimally dimensioned or welded componentt elem componen elements ents such as bea bearing ring blocks, blocks, ribs, reinforcing plates etc.
Measures: The com compo pone nent nt can alm almost ost always always be repair repaired ed by welding. welding. For a durable durable repair, the comp compone onent nt must be open opened ed to allo allow w th the e weld welds s in th the e comp compon onen entt areas subject to maximum stress to be capped.
2.
Plate Plate part partin ing g
The The plat plate e ma may y crac crack k open open almo almost st exac exactl tly y at th the e centre of the plate, as shown in the diagram (fig. 89).
Fig. 90
Reason for the damage: The component is not adequately stable. The chord plate is deformed under changing loads, resulting in material distortions at the weld/chord plate transition.
Measures: The chord plate cannot be repaired by welding. For a durable repair, the plate must be replaced in the cracked area. The new plate must be thicker than the cracked one to reduce deformation to a tolerable level.
Fig. 89
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Page 47 Page 47
REPAIR WELDING TECHNIQUES 3.7.3.4 Repair of a boom boom with a salient salient chord
3.
The The top top chor chord d of the the boom boom is crac cracke ked d (arr (arrow ows, s, fig. 91).
Repair Repair the dam damage age inside the box-type box-type section and in the side walls.
4.
Weld on new top chord (fig. (fig. 93). Increase Increase plate thickness by 5 to 10 mm.
1.
Remove support eye (1, fig. 91).
Fig. 93 Fig. 91
2.
Remo Remove ve top top chor chord d in th the e area area of da dama mage ge (fig. 92). Recommendation: Remove Remove the curved section of the top chord completely.
5.
Weld support support eye back back in place place (fig. 94). 94). Machining of the severed parts is generally not requir required ed if fittin fitting g and and weldin welding g are carrie carried d out out carefully.
Fig. 94 Fig. 92
48
2 en - (0)
REINFORCING OF STEEL COMPONENTS 4.
Reinfo Rei nforci rcing ng of steel steel compon component ents s
•
The reinforcement of components by welding can be done in the following ways: •
Covering Covering up a damaged damaged area after repair repair by reinforcing plates, with the aim of reducing the mechan chanic ical al stre stress sses es (N/m (N/mm m2) in the repair area.
•
Elimina Eliminating ting deficiencie deficiencies s cau caused sed by cha change nges s in shape,, e.g shape e.g.. the proble problema matic tic case case of "op "open en secsections/ tions/clo closed sed sectio sections" ns",, sha shape pe of stiffen stiffening ing ribs, ribs, configuration of frame corners, etc.
•
Eliminat Eliminating ing deficienci deficiencies es by mea means ns of chan changes ges in shape by build shape build-up -up weldi welding, ng, e.g e.g.. on castcast-ste steel el parts.
Thickness of reinforcing plates The thickness of reinforcing plates should be max. 60 % of the thickness of the plate to be reinforced (fig. 2).
The necessity of a component reinforcement should, if possible, have been proved by a simple analysis. 4.1 4.1 Rein Re info forc rcin ing g plat plates es Fig. 2
4.1.1 4.1.1 Dime Dimens nsio ions ns • Length of reinforcing reinforcing plates The ends of reinforcing plates are places where metallurgic metal lurgical al and shape shape-indu -induced ced notch notches es occur which may lead to damage by the concentration of stresses (Part A, fig. 1). •
An analysis shows that thicker reinforcing plates cannot be connected to the plate to be reinforced as the the weld weldin ing g seam seams s requ require ired d woul would d be too too large. Thicker Thicker plat plates es moreover moreover lead to large large shap shape-ine-induced notches and make the component heavier than is really necessary. Width of reinforcing plates In stee steell comp compone onents, nts, stresses are often highest highest nearr the edg nea edges. es. The reinfo reinforcin rcing g pla plate te sho should uld therefore be as wide as the plate to be reinforced (A, fig. 3).
Fig. 3 Fig. 1
Reinforci Reinforcing ng pla plates tes sho should uld therefor therefore e be dime dimennsioned in such a way that they end in areas with low basic stresses (Part B, fig. 1).
2 en - (0)
Page 49 Page 49
REINFORCING OF STEEL COMPONENTS For practical reasons, reinforcing plates of less than 8 mm thic thickn knes ess s can can not not be cham chamfe fere red. d. In such such cases, the reinforcing plate (B, fig. 3) must be narrower to leave enough space for a fillet weld. The upper edges (arrow, fig. 3) of the plate to be reinforced and of the reinforcing plate should not be melted away.
50
2 en - (0)
REINFORCING OF STEEL COMPONENTS 4.1.2
Shapes Shapes of reinforcing reinforcing plates
Reinforci Reinforcing ng plat plates es shou should, ld, if possible possible,, have simple shapes with straight edges (figs. 4 + 5). To relieve the transverse seams of stresses, welding slots should be provided (fig. 4).
Small pla Small plate te strips strips,, flat-st flat-stee eell or wide wide flat-st flat-stee eell bars, bars, can be more easily fitted and bent (fig. 5).
Fig. 6
Fig. 4
Another possibility possibility consists in welding on strips of plate. In this case, the longitudinal seams must be welded continuously.
Non-linear plate shap shapes es (figs. 7 + 8) are difficult to manufacture and do not offer any advantages with regard to the distribution of forces.
Advantages: The edge zones, where high stresses normally prevail, are reinforced. Another advantage is the reduction of weight (fig. 5).
Fig. 7
Fig. 5
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Page 51 Page 51
REINFORCING OF STEEL COMPONENTS
Fig. 10
The The weldin welding g sea seams ms in the welding welding slots slots are ideal thrust connections between the reinforcing plate and the plate to be reinforced. Circular welding holes are disadvantageous (fig. 11):
Fig. 8
4.1.3 4.1.3
Weld Weldin ing g slots slots
In addit addition ion to the welding welding sea seams ms alo along ng the outer outer edge edges, s, the the seam seams s in in weld weldin ing g slot slots s are are equa equall lly y inten intended ded to enh enhan ance ce the con conne necti ction on of reinfo reinforci rcing ng plates (figs. 9 and 10).
Fig. 11 Fig. 9
Finish the ends of the slots by drilling stopper holes (fig. 9). Slot width = 2 x plate thickness (fig. 9).
The The part parts s of the the seam seam tran transv sver erse se to the the line lines s of forces cannot bear any loads and can therefore not be considered for analysis. The reinforci reinforcing ng plat plate’s e’s cross-secti cross-section on is strongly strongly reduced. The hole edges are subject to stress concentrations.
52
2 en - (0)
REINFORCING OF STEEL COMPONENTS 4.1.4
Fitting Fitting of reinforcin reinforcing g plates
studs have been removed must be carefully prepared by grinding before the slot is welded.
Reinforcing plates should be in full-face contact with the the plat plate e to be rein reinfo forc rced ed,, i.e. i.e. th they ey shou should ld lie lie as closel closely y as possi possible ble against against the base base pla plate. te. The air gap should, if possible, be nil. For relatively small components and thin plates, the reinfo reinforci rcing ng pla plates tes sho should uld be squ squee eezed zed again against st the base plate by means of screw clamps (fig. 12).
Fig. 12
For larger components and thicker plates, the reinforcing plates should be held in place by wedges (fig. 13). This is, however, only possible at the edges of plates. Welding and cutting of the wedge holders must be done properly. Never knock off wedge holders with a hammer.
Fig. 14
4.1.5 4.1.5
Weld Weld seams seams of T-join T-joints ts
Reinforcing plates in T-joint areas should be welded in such a way that a connection between all 3 plates is formed (fig. 15).
Fig. 13
The central area of plates can be pressed into position by means of bolting (fig. 14). This is particularly recommended for large plate sections. The studs can be favourably placed near the welding slots. After tack-welding, tack-welding, the welded-on welded-on stud stud may only be knocked off. The area in the base metal where the 2 en - (0)
Fig. 15
Page 53 Page 53
REINFORCING OF STEEL COMPONENTS 4.2 4.2
Shap Shapin ing g plate plates s for for repa repair irs s
•
The plates needed for repair repair or reinforce reinforcement ment purposes can be shaped in different ways.
Rolling (Fig. 18): cold shaping; no problems to be expected after shaping.
Proble Problems ms which which ma may y arise arise in the differ differen entt sha shapin ping g methods: • Edge folding (Fig. 16): 16): cold shaping; observe minimum bending radius; watch watch for long longitu itudi dina nall cracki cracking ng in th the e bend bendin ing g area.
Fig. 18 •
Fig. 16 •
Multi-edge bending (Fig. 19): 19): cold shaping: cracking at the lines where the tools act on the plate edges is to be expected; chamfer plate edges approx. 2 x 2 mm at top and bottom after multi-edge bending.
Pressing (Fig. 17): cold or warm shaping; with cold shaping, observe minimum bending radius diu s and and watch watch for longi longitud tudina inall cracki cracking ng in the bending area.
Fig. 19
Fig. 17
54
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REINFORCING OF STEEL COMPONENTS 4.3
Reinfo Rei nforci rcing ng by shape shape impro improvem vement ents s
4.3.1 4.3.1
End End of ribs ribs
Areas where overlapping overla pping takes place should be ground smooth (fig. 21).
The terminal section of ribs ending on highly stressed parts of components is to be shaped as shown in fig. 20. This applies equally to ribs of minor importance.
Fig. 21
Make sure that the welding seam as such is not ground off.
4.3.2
Open sections/clo sections/closed sed sections sections
The moment of torsion resistance of a closed section is appro approxim ximate ately ly 500 500 tim times es greate greaterr tha than n tha thatt of an open section of otherwise similar dimensions. This leads to stress peaks in the zone of transition from the opened to the closed section. These peaks are cau caused sed by defor deformat mation ion imp imped edime iments nts and con con-straints (fig. 22).
Fig. 20
t mm
a mm
h mm
o
R mm
e mm
L1 mm
L2 mm
6
4
6
10
60
20
30
12
8
4
6
10
60
20
30
12
10
4
6
10
80
20
30
12
12
5
8
10
100
20
40
14
15
6
9
10
120
30
50
18
20
8
12
10
160
30
60
22
26
8
12
10
180
30
70
22
30
10
15
10
200
30
70
28
Fig. 22
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T
Torsional moment
O
Open section
G
Closed section
Page 55 Page 55
REINFORCING OF STEEL COMPONENTS
Therefore, it is required to have a gradual transition from the open to the closed section (fig. 23).
4.3.3
Reinforcing Reinforcing by build-up build-up welding welding
The effects of notches in steel components can be eliminated or at least mitigated by build-up welding. Such work presupposes expert planning and careful workmanship (fig. 24).
Fig. 23
The area of transition is to be welded around continuously. Fig. 24
56
2 en - (0 )
REINFORCING OF STEEL COMPONENTS 4.3.4
Improvemen Improvementt of curved sections sections in ribs
Fig. 25 shows a rib contour with too high stresses in the marked area.
Fig. 25
To impr improv ove e this this situ situat atio ion, n, weld weld on a plat plate e of th the e same sam e thickn thickness ess (fig. (fig. 26) 26) and obser observe ve the weldi welding ng sequence as represented in the cross-section.
Subsequently, a new and better contour can be produced duce d by flam flame-cu e-cutting tting (fig. 27). In doin doing g so, make sure that the torch guidance unit is absolutely stable.
Fig. 27
1
Flame-cut here
Grind flame-cut edge smooth and work out the new contour (fig. 28).
Fig. 26
1
Weld joint prepared
Fig. 28
2
First side welded
2
3
Back of first side gouged to sound sound metal
4
Second side welded
5
Faces of welds ground smooth
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Grind here
Reworking facilitates the gradual and continuous flow of component forces.
Page 57 Page 57
MATERIALS, FILLER METALS FOR WELDING 5.
Materi Materials als,, filler filler metals metals for weldin welding g
5.1
Materi Materials als in welded welded compon component ents s
Before welding, gouging, warm or cold bending and heat treatments, treatments, the person person carrying carrying out the repair must be familiar with the material of the component. At least the following information should be available: -
strength class state of heat heat treatment chemical chem ical analysis analysis referenc reference e data data;; carbon carbon equivalent material thicknesses
The repair measures to be carried out depend essentially on the above data.
The material properties cannot be determined by simple simple hardn hardness ess measur measureme ements nts or even even by a spark test. Such testing methods lead to wrong conclusions. After this, the filler metals suited to the materials can be select selected ed.. For the select selection ion of filler filler me metal tals, s, the perso person n carryi carrying ng out the repair repair sho should uld see seek k adv advice ice from the manufacturer of the machine or the supplier of filler metals. Recommendations can also be found in the catalogues of the filler metal manufacturers. The materials used by O&K for welded components and their suitable filler metals are listed on the following pages.
These can be found in drawings and parts lists. The operator of a machine can obtain the required information from the manufacturer, e.g. from O&K. In case of scheduled repair work, the type of material can also be determined in a materials testing laboratory.
58
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MATERIALS, FILLER METALS FOR WELDING 5.1.1 5.1.1
O&K compon component ent materi materials als
Materials for welded components in O&K construction machinery and mining equipment
Plate
Plate
Stan Standa dard rd desi design gnat atio ion: n: Trade name: Delivery specification:
EN 1002 10025 5 - S275 S275JR JRG2 G2 (ex. (ex. St37 St37-2 -2)) -
EN 1002 10025 5 - S355 S355J2 J2G3 G3 (ex. (ex. St52 St52-3 -3)) LV 2 293 157
Desc Descri rip ptio tion of ma mate teri ria al
Fine ine-gra -grain ine ed stru struct ctu ural ral ste steel weldable normalized killed
Fine ine grain rained ed stru struct ctu ural ral ste steel weldable normalized double killed
Heat Heat treat treatme ment nt stat state: e:
norm normal aliz ized ed or in an equi equiva vale lent nt stat state e atta attain ined ed by norm normal aliz izin ing g roll rollin ing g
Mechanical and technological properties (reference values): Tens Tensil ile e stre streng ngth th Hardness Yield ield stre trength Elongation Impact energy
Rm Rm B.H.N. Rel Rel A Av
N/mm N/mm2 B.H.N. N/m /mm m2 % Joule
Chemical composition:
340 - 470 œ 140 _ > 265 _ > 2 6 > _ 27 J ISOISO-V V + 20oC
490 - 630 œ 190 _ > 345 > _ 22 > _ 27 J ISOISO-V V - 20oC
EN 10025, table 3
Processing characteristics: Welding:
Highly suited; cf. 1.5.8 and 6.1.
Highly suited; cf. 1.5.8 and 6.1.
Warm bending:
Possible at temperatures between 400 and 850 oC.
Possible at temperatures between 400 and 850 oC.
Cold bending:
Possible, but observe DIN 18800, Part 1.
Possible, but observe DIN 18800, Part 1.
Additional information about material; valuable for practical repairs:
Used only for subordinate welded components. Not used in load-bearing load-bearing components.
Abt. 95 % of of the load-bearing load-bearing components are made of this material.
Filler metals
See page 61
See page 61
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Page 59 Page 59
MATERIALS, FILLER METALS FOR WELDING
Plate
Plate
Plate
DIN EN 101 10113-2 13-2-S46 -S460N(e 0N(ex.St x.St E460 E460)) EN 100 10037 37 - S690Q S690QL(ex L(ex.St .St E690 E690))
Wear plat plate e 500 500 HB LV 2 270 270 002
Fine-g Fine-grai raine ned d struct structura urall ste steel el
Fine-g Fine-grai raine ned d hig high h stren strength gth structu structural ral steel weldable quenched and tempered
Fine-grained Fine-grained structural steel high strength weldable quenched and tempered
Normalized or in an equivalent state induced by normalizing rolling
quenche que nched d and temp tempered ered in fluid
quenche que nched d and temp tempered ered in fluid
550 - 720 210 460 17 _ > 40 J ISO-V - 20 oC
790 - 940 ~ 300 _ > 690 > _ 16 > _ 27 J ISO-V - 40 oC
1550 ~ 450 - 540 _ > 1300 > _8 > _ 20 J ISO-V - 10 oC
See DIN EN 10113-2
See EN 10037
See manufacturer’s instructions
Welda Weldable ble;; see 1.5 1.5.8 .8 and 6.1
Readil Readily y welda weldable ble;; see 1.5 1.5.8 .8 and 6.1
Possible at temperatures between 400 and 850°C Possible, but observe DIN 18800, Part 1
Not possible without postweld quenching and tempering Possible by rolling
Welda Weldable ble as wear wear protec protectio tion; n; preheating to + 100°C Not possible
Used mainly for hubs on equipment for construction machinery
Used by O&K for wear-prone parts, e.g. excavating tools, blades, wearing edges
Wearing plates welded onto excavating tools
See page 61
See page 61
See page 61
weldable normalized
60
Possible with very large radius by rolling (plate thickness)
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MATERIALS, FILLER METALS FOR WELDING
Materials for welded components in O&K construction machinery and mining equipment
Cast steel
Standard designation:
GS-52.3V) SEW 685 - GS-21Mn5V (ex. GS-52.3V)
Trade name: Delivery specification:
LV 2 102 375
Cast steel
DIN 17205 - GS - 25 CrMo4V CrMo4V IIII SEW 520 - GS - 18 NiMoCr36V SEW 520 - GS - 22 NiMoCr56V ESCO - cast steel
Description of material
Cast steel weldable quenched and tempered
Cast steel
Hea Heat tre treatm tme ent sta state: te:
quenche nched d and te temp mpe ered red in flu fluid
quenche nched d and temp tempe ered red in flu fluid
Mechanical and technological properties (reference values): Tens Tensil ile e stre streng ngth th Hardness Yield ield stre trength Elongation Impact energy
Rm Rm B.H.N. Rel Rel A Av
N/mm N/mm2 B.H.N. N/m /mm m2 % Joule
Chem Chemic ical al comp compos osit itio ion: n:
480 - 620 ~ 180 _ > 340 _ > 2 0 > _ 35 J ISOISO-V V - 50oC SEW SE W shee sheett and and O&K O&K inst instru ruct ctio ions ns
850 - 1000 ~ 300 _ > 750 > _ 10 > _ 27 J ISOISO-V V - 20oC See See ma manu nufa fact ctur urer er’s ’s inst instru ruct ctio ions ns
Processing characteristics: Welding:
Readily weldable. See 1.5.8 and 6.1 Re Readily weldable. See 1.5.8, 1.5.9 and 6.1
Warm bending: Cold bending: Additional information about material; valuable for practical repairs:
Together with plate St 52-3 in plate/cast steel composite constructions
Adapters, corner corner blades; blades; almost all cast wearing parts
Filler metals
See page 61
See page 61.
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Page 61 Page 61
MATERIALS, FILLER METALS FOR WELDING 5.2 5.2
Fille Fillerr metal metals s for for O&K O&K weld welded ed compon componen ents ts depend dependin ing g on partn partner er materi materials als and weldi welding ng techniques
Part nos. for filler metals are listed in the appendix.
Material 1 Designations Standard Delivery instruction
Material 2 Designations, standards and delivery instructions as for Material 1
Gas-shielded welding EN 24063: 135 Standard designations Trade names
Arc welding EN 24063: 111 Standard designations
S235JRG2 DIN EN 10025
S235JRG2 S355J2G3 GS-21Mn5V S460N
EN 440: G 38 4 M G3Si1 AWS A5.18: E 70S-6 EN 439: M21 (shielding gas) (ex. DIN 8559: SG2)
EN 499: E 38 2 RA 22 AWS A 5.1: E 6013
S355J2G3 DIN EN 10025 oder LV 2 293 157 (ex. St52-3)
S355J2G3 GS-21Mn5V S460N S690QL GS-25CrMo4V II GS-22NiMoCr56V GS-18NiMoCr36V ESCO cast steel, blade Wear plate 500 HB
EN 440: G42 4 M G4Si1 AWS A5.18: E 70S-6 EN 439: M 21 (ex. DIN 8559: SG3)
EN 499: E 38 4 B 42 AWS A 5.1: E 7018 (ex. DIN 1913: E 5154 B 10)
S460N DIN EN 10113 Part 2 (ex. StE460)
S460N S690QL GS-25CrMo4V II GS-22NiMoCr56V GS-18NiMoCr36V Wear plate 500 HB
DIN 8575: SG CrMo1 AWS A5.28: ER 80S-G EN 439: M21
DIN 8575: ECrMo1 B 20 AWS A 5.5: E 8018-C1
S690QL DIN EN 10037 (ex. StE690)
S690QL GS-25CrMo4V II GS-22NiMoCr56V GS-18NiMoCr36V Wear plate 500 HB
EN: not standardized Trade names: UNION NiMoCr NiCrMo 2,5-IG AWS A 5.28: ER 110S-G EN 439: M21
EN 757: E 69 5 Mn2NiCrMo B 42 AWS A 5.5: E 110-18M
GS-21Mn5V SEW 685 and LV 2 102 375 (ex. GS-52.3V)
GS-21Mn5V S355J2G3 S460N S690QL
EN 440: G 42 4 M G4Si1 AWS A 5.18: E 70S-6 EN 439: M21 (ex. DIN 8559: SG3)
EN 499: E 38 4 B 42 AWS A 5.1: E 7018 (ex. DIN 1913: E 5154 B10)
GS-25CrMo4 GS-25CrMo4V V II and modifications DIN 17205 and LV 262 480
GS-25CrMo4V II
EN: not standardized Trade names: UNION NiMoCr NiCrMo 2,5-IG AWS A 5.28: ER 110S-G EN 439: M21
EN 757: E 69 5 Mn2NiCrMo B 42 AWS A 5.5: E 110-18 M
GS-22NiMoCr56V and modifications SEW 520
GS-22NiMoCr56V
EN: not standardized Trade names: UNION NiMoCr NiCrMo 2,5-IG AWS A 5.28: ER 110S-G EN 439: M21
EN 757: E 69 5 Mn2NiCrMo B 42 AWS A 5.5: E 110-18 M
GS-18NiMoCr36V SEW 520
GS-18NiMoCr36V
EN: not standardized Trade names: UNION NiMoCr NiCrMo 2,5-IG AWS A 5.28: ER 110S-G EN 439: M21
EN 757: E 69 5 Mn2NiCrMo B 42 AWS A 5.5: E 110-18 M
ESCO cast steel Adapter
S690QL
EN 440: G 42 4 M G4Si1 AWS A 5.18: E 70S-6 EN 439: M21 (ex. DIN 8559: SG3)
EN 499: E 38 4 B 42 AWS A 5.1: E 7018 (ex. DIN 1913: E 5154 B10)
ESCO cast steel Corner blade
S690QL
EN: not standardized Trade names: UNION NiMoCr NiCrMo 2,5-IG AWS A 5.28: ER 110S-G EN 439: M21
EN 757: E 69 5 Mn2NiCrMo B 42 AWS A 5.5: E 110-18 M
(ex. St37-2)
62
(ex. DIN 1913: E 4332 AR7)
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MATERIALS, FILLER METALS FOR WELDING Examples of the meaning of designations of filler metals for welding:
Rod electrode
EN 499 : E 38 4 B 4 2 Design. of welding pos.; here: all positions except vertical-down weld Code no. for type of current; here: direct current Code letter for coating; here: basic Code no. for minimum impact energy; here: _ > 47 joules at - 40°C (100°F) Code no. for minimum yield strength; here: R el = > _ 380 N/mm2 Code letter for welding technique; here: arc welding, 111 Number of European Standard European Standard Former designation: DIN 1913: E 5154 B 10
Welding wire
EN 440 : G 42 4 M G4Si1 Code no. for chemical composition of weld metal Code letter for inert gas; here: mixed gas EN 439: M 21 Code no. for minimum impact energy; here: _ > 47 joules at - 40°C (100°F) Code no. for minimum yield strength; here: R el = > _ 420 N/mm2 Code letter for welding technique; here: metal-inert-gas (MIG) method, 135 Number of European Standard European Standard Former designation: DIN 8559: SG 3
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Page 63 Page 63
HEAT TREATMENT OF MATERIALS 6.
Heat He at trea treatm tmen entt of mate materi rial als s
The repair repair of ste steel el com compon ponen ents ts often often requir requires es the use of heat. The instructions on the input of heat with regard regard to the materials materials and working methods methods used are to be observed.
6.1 6.1
Preh Prehea eatin ting g for for tacki tacking ng,, weld weldin ing, g, gou gougi ging ng and flame-cutting
Preheati Preheating ng for tacking, tacking, welding, welding, joining joining and flame flame-cutting is necessary for two main reasons: • It prevents prevents heat from dissipa dissipating ting too fast fast from the heat-affe hea t-affected cted zone zone.. The prolonge prolonged d cooling cooling time achieved prevents the formation of hard and brittle structural states. Moist Mo isture ure is dried dried out in the welding welding area. area. The The • penetrat pen etration ion of detriment detrimental al hydrogen hydrogen and oxygen oxygen via the arc into the liquid weld pool is avoided.
Influence of wall thickness and of weld joint When preheating components for welding, the quantity of heat to be applied depends on the dimensions of the component and on the weld joint.
Fig. 2
Butt joint (Fig. 3) Heat dissipation two-dimensional. Rapid heat dissipation due to large component crosssections.
T-joint (Fig. 1) Heat dissipation three-dimensional. three-dimensional. Very rapid heat dissipation due to large component cross-sections.
Fig. 3
Butt joint (Fig. 4)
Fig. 1
Heat dissipation two-dimensional. Gradu Gradual al heat heat dissip dissipati ation on due to sma smallll com compon ponen entt cross-sections.
T-joint (Fig. 2) Heat dissipation three-dimensional. three-dimensional. Gradu Gradual al heat heat dissip dissipati ation on due to sma smallll com compon ponen entt cross-sections.
Fig. 4
64
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HEAT TREATMENT OF MATERIALS
Prevention of hardness peaks The formation of structural states which are undesirable due to being too hard and brittle is avoided by preheating.
The preheating temperature depends primarily on the material, the shape and thickness of the component, the welding technique and the climatic influences. During repair work, it is absolutely essential to observe the temperatures specified in the following list. In case cases s of doub doubt, t, the the comp compan any y carr carryi ying ng out out the the welding must consult a specialized welding engineer from the relevant O&K plant via the O&K After-Sales Service about necessary preheating temperatures to ensure that the repair work is properly done.
Fig. 5
1
Hardness, non-admissible* non-admissible*
2
Hardness, admissible*
3
Hardness in base material, heat-affected, without preheating
4
Hardness Hardness in base material, material, heat-affecte heat-affected, d, with preheating
5
Weld metal
6
Base material, not affected affected by heat heat
7
Hardness series
HV Hardness *
depe dependi nding ng on ma mater terial ial
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Page 65 Page 65
HEAT TREATMENT OF MATERIALS Preheating and interpass temperatures; heating-up and cooling-down rates when repairing by welding •
Non-all Non-alloye oyed d structura structurall steels in normal normalize ized d state as per DIN EN 10025 10025 or LV 2 293 157, such as S355J2G3 (ex. St52-3) and S235JRG2 (ex. St37-2).
Max. heating-up rate, reference value Min. preheating temperature for tacking and welding: Wall thicknesses < 25 mm Exceptions: - Component temperature below +20°C - Ambient temperature below +10°C - Component wet, moist or dewy Wall thicknesses > _ 25 mm Max. interpass temperature during welding: All wall thicknesses thicknesses Min. preheating temperature for flame-cutting and gouging: Wall thicknesses _ > 80 mm Max. cooling-down rate, reference value: All wall thicknesses thicknesses •
+ 20°C
(70°F)
+ 100°C + 100°C + 100°C + 100°C
(210°F) (210°F) (210°F) (210°F)
+ 250°C 250°C
(480°F) (480°F)
+ 100°C
(210°F)
+ 50°C/h 50°C/h
(120°F/h) (120°F/h)
+ 50°C/h
(120°F/h)
+ 20°C + 100°C
(70°F) (210°F)
+ 250°C 250°C
(480°F) (480°F)
+ 100°C
(210°F)
+ 50°C/h 50°C/h
(120°F/h) (120°F/h)
High-s High-stre trengt ngth h fine-g fine-grai rain n steels steels quenched quenched and temper tempered ed in fluid fluid as per SEW 090, part 1, such such as S690Q and S690QL (ex. StE690).
Max. heating-up rate, reference value Min. preheating temperature for tacking and welding: Wall thicknesses < 80 mm Wall thicknesses _ > 80 mm Max. interpass temperature during welding: All wall thicknesses thicknesses Min. preheating temperature for flame-cutting and gouging: Wall thicknesses _ > 80 mm Max. cooling-down rate, reference value: All wall thicknesses thicknesses
66
(120°F/h)
Hot-rolled Hot-rolled products products made of weldable weldable fine-grain fine-grain structural structural steels as per DIN EN 10113, part 2, such as S460N (ex. StE460). StE460).
Max. heating-up rate, reference value Min. preheating temperature for tacking and welding: Wall thicknesses < 25 mm Wall thicknesses _ > 25 mm Max. interpass temperature during welding: All wall thicknesses thicknesses Min. preheating temperature for flame-cutting and gouging: Wall thicknesses _ > 80 mm Max. cooling-down rate, reference value: All wall thicknesses thicknesses •
+ 50°C/h
+ 30°C/h
(90°F/h)
+ 100°C + 150°C
(210°F) (300°F)
+ 220°C 220°C
(430°F) (430°F)
+ 100°C
(210°F)
+ 30°C/h 30°C/h
(90°F/h) (90°F/h)
2 en - (0 )
HEAT TREATMENT OF MATERIALS
•
Wear Wear plates plates 500 HB as per O&K delivery delivery instruc instructio tion n 2 270 002, such as HAR HARDOX DOX 500, DILLIDU DILLIDUR R 500V, XAR 500.
Max. heating-up rate, reference value Min. preheating temperature for tacking and welding: Wall thicknesses < 20 mm Wall thicknesses > _ 20 mm Max. interpass temperature during welding: All wall thicknesses thicknesses Min. preheating temperature for flame-cutting and gouging: All wall thicknesses thicknesses Max. cooling-down rate, reference value: All wall thicknesses thicknesses •
+ 30°C/h
(90°F/h)
+ 100°C + 150°C
(210°F) (300°F)
+ 220°C 220°C
(430°F) (430°F)
+ 100°C 100°C
(210°F) (210°F)
+ 30°C/h 30°C/h
(90°F/h) (90°F/h)
Steel castings castings with a high impact impact strength at low temperature, temperature, quenched quenched and tempered, tempered, with good weldability weldability as per SEW 685 and LV 2 102 375, such as GS-21Mn5V (ex. GS-52.3V). GS-52.3V).
Max. heating-up rate, reference value Min. preheating temperature for tacking and welding: All wall thicknesses thicknesses Max. interpass temperature during welding: All wall thicknesses thicknesses Min. preheating temperature for flame-cutting and gouging: Wall thicknesses > _ 80 mm Max. cooling-down rate, reference value: All wall thicknesses thicknesses
+ 30°C/h
(90°F/h)
+ 100°C 100°C
(210°F) (210°F)
+ 250°C 250°C
(480°F) (480°F)
+ 100°C
(210°F)
+ 30°C/h 30°C/h
(90°F/h) (90°F/h)
•
Heat treated treated steel casting for castings castings as per DIN 17205 and LV 262 480, such as GS-25CrMo4 GS-25CrMo4V V II and modifications.
•
High High-st -stre reng ngth th steel steel casti casting ng with with good good welda weldabi bilit lity y as per per SEW SEW 520 520 and and LV 943 943 661, 661, such such as GS-22NiMoCr56V and modifications.
ESCO steel castings as per ESCO specifications. Max. heating-up rate, reference value Min. preheating temperature for tacking and welding: All wall thicknesses thicknesses Max. interpass temperature during welding: All wall thicknesses thicknesses Min. preheating temperature for flame-cutting and gouging: All wall thicknesses thicknesses Max. cooling-down rate, reference value: All wall thicknesses thicknesses
•
2 en - (0)
+ 30°C/h
(90°F/h)
+ 150°C 150°C
(300°F) (300°F)
+ 220°C 220°C
(430°F) (430°F)
+ 100°C 100°C
(210°F) (210°F)
+ 30°C/h 30°C/h
(90°F/h) (90°F/h)
Page 67 Page 67
HEAT TREATMENT OF MATERIALS
Preheating procedure: For preheating purposes, the heat must be applied at a hea heatin ting-u g-up p rate rate of 30 to 50° 50°C/h (90 to 120° 120°F/h F/h). ). This can be done by one of the following methods: •
•
•
Electric heating mats If the fastening elements for the heating mats have have to be weld welded ed to th the e comp compon onen ent, t, th the e welding areas must be locally preheated. After removal of the fastening elements, the welding areas must be ground to eliminate any microcracking in the component material. Gas jets Gas jets must be applied to the component in such a way that there is no risk of the component being locally overheated. It may be necessary essary to protec protectt the com compo pone nent nt from from ove overrheating by using heat buffer plates. Gas burners G as as b ur ur n e err s m us us t b u rrn n w i th th a g en en t le le , low-o low-oxyg xygen en flame flame.. The The gas flame flames s mu must st not not contact the component because of the risk of local local ove overhe rheatin ating. g. The com compon ponent ent mus mustt be protec protected ted from from ove overhe rheati ating ng by using using heat heat buffer plates.
Temperature measuring Measuring points for measuring the preheating temperature and the interpass temperature. Key: • • •
Tv = preheating temperature Tz = interpass temperature t = thickness of component component
Preheating temperature Measurin Mea suring g poin point: t:
4 x t measu measured red from the centre centre of of the weld.
Measurin Mea suring g time time::
before befo re tacking tacking and welding. welding.
Interpass temperature Measu Me asurin ring g point point::
30 mm besid beside e the ce centr ntre e of the weld or 30 mm beside the centre of the last bead
Measu Me asurin ring g tim time: e:
not not less less than than 2 min minute utes s after after arc welding.
In all heati heating ng proced procedure ures, s, the com compo ponen nentt mu must st be covered with insulant mats to prevent excessive heat dissipation into the environment. The cooling-down process after welding must not be accelerated with compressed air, draughts or water. The weld area must cool down gradually, depending on material (see data) at a rate of 30 to 50°C/h (90 to 120°F/h) to room temperature RT = 20°C (70°F). For cooling-down purposes, the components must be covered with insulant mats.
Important: For technical and economic reasons it is advisable to carry out repair welding with a duration cove coveri ring ng mo more re than than one one shif shiftt with with th the e nece necess ssar ary y preheating and controlled cooling-down continuously, i.e. in one working operation (day shift - night shift etc.) If the welding is done only during the day shift, for example, careful cooling-down to RT and heatingup to the prescribed preheating temperature must be assured.
68
Fig. 6
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HEAT TREATMENT OF MATERIALS 6.2 6.2
Hot Hot bend bendin ing g of plat plates es
Under the influence of heat, steel loses the mechanotechnological properties that it possesses in the cold state. This characteristic can be used for hot bending. The ideal hot-bending temperature lies between 800 and 850oC (1470 - 1560oF) when the material is in the state of red heat.
6.4 6.4
Stre Stress ss-r -rel elie ieff annea anneali ling ng of of steel steel comp compoonents
For practical repairs, stress-relief annealing is hardly ever necessary. If a component is to be stress-relief annealed after repair or reinforcing, some fundamental rules are to be observed. Details of the process are to be discussed with the annealing workshop before annealing. annealing.
In practical practical repairs, only normaliz normalized ed plate qualities, qualities, such such as S27 S275JR 5JRG2 G2,, S35 S355J2 5J2G3, G3, can be treate treated d by hot bending.
•
Quenched Quenc hed and and tem temper pered ed ste steel el pla plates tes can onl only y be treated by cold bending or at temperatures between 400oC (750oF) and 550oC (1020oF).
Machi Ma chine ned d surfac surfaces es are to be mea measur sured ed befor before e and after the annealing process. Distortion due to annealing is to be reworked.
•
Machined Machi ned surfaces surfaces are to be protec protected ted before before annealing against the formation of scale by applying suitable protective coatings.
•
For pressure compensatio compensation n purposes, purposes, hollow sections tions are to be provid provided ed with with drill drill holes holes befor before e annealing takes place. Hole diameter 4 mm.
•
Annealing parameters:
Quenche Quen ched d an and d temp tempere ered d ste steel el plate plates, s, such such as o S690Q, would be overdrawn at abt. 800 C (1470oF) and lose their mechano-technological properties. This would require requenching and retempering which is hardly practicable in field repairs. Normalize Normalized d or que quenche nched d and tempered tempered stee steell plate plates s must by no means be treated by cold bending in a temp temper erat atur ure e rang range e of abt. abt. 100 100 to 350 350 oC (21 (210 o 610 F), as in this this so-cal so-called led blu blue-h e-hea eatt tem temper peratu ature re range the material is brittle and tends to the formation of cracks in the bending area.
6.3 6.3
Hot Hot stra straig ight hten enin ing g of plat plates es
Plates can be straightened in a cold and warm state. In cold straighte straightening ning,, the defo deformin rming g forces forces required required are exerted from the outside by means of tools, such as presses or rolls. Hot straighte straightening ning makes use of the interaction interaction produced by the local input of heat: Elong Elongati ation on of the ma mater terial ial in the warmed warmed-up -up area, area, upsetting of the warm material at the transition to the cold cold area, area, shrink shrinkag age e of the warmed warmed-up -up area and and straight stretching by internal stresses.
-
Annealing Anneal ing tempera temperatur ture e for norma normaliz lized ed mat materi eri-o o o als 580 C + 20 C (1080 + 70 F)
-
Anneal Ann ealing ing tempera temperatur ture e for quenche quenched d and tempered materials 30oC (90oF) below tempering temperature. This value can be taken from the releva relevant nt sta stand ndard ards s or the ma mater terial ial certif certif-icates. As a rule, the annealing temperature is 530 to 550 oC (990 - 1020oF). - Heat Heatin ing g and and cool coolin ing g shou should ld take take plac place e at a rate of around 50 oC/h (120oF/h). The furnace may be at a temperature of 150oC (300oF)when the component is inserted. It can be opened after cooling when the temperature is 150oC (300oF). Final cooling can then take place in calm air.
-
The holdi holding ng time at anneal annealing ing temper temperatu ature re in the furnace should be 2 min. per mm of wall thickness, but not less than 1 h.
The The ma mate teri rial al shoul should d be warm warmed ed up to red red heat heat if efficient straightening is to be achieved. Here Here again again the ma mater terial ial quality quality is to be tak taken en into into consideration. Only normalized plates can be bent in a hot state without the loss of mechano-technological properties. In hot hot bend bending ing of que quench nched ed and and tem tempe pered red pla plates tes,, quality losses in the heated areas must be reckoned with.
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HEAT TREATMENT OF MATERIALS 6.5
Stress Stress-re -relie lievin ving g of steel steel compo componen nents ts
As a stress-relief annealing of repaired componen components ts is feasible only in rare cases and as machined surfaces fac es ma may y lose lose the their ir dim dimen ensio siona nall accura accuracy cy in the annealing process, it is necessary to take other measures for the reduction of stresses.
6.5.1 6.5.1
Warmin Warming g of compon component ents s
One means of reducing high local internal stresses, which may occur, for example, after build-up welding or weld seam repairs, consists in stress relieving of the component area concerned. The area area around around presum presumed ed stress stress con concen centrat tration ions s must be heated up to 250 to 300°C (480 to 570°F). Electric heating mats, gas jets or gas burners can be used as sources of heat. Heating up must be done at a rate of approx. 30°C/h (90°F/h). For simply simply designe designed d comp componen onents ts with a wall thickness of less than approx. 25 mm, a retaining period of 3 h is sufficient. For more compact components with wall thicknesses of more than approx. 25 mm, a retaining period of 5 h is necessary. Cool Coolin ingg-do down wn mu must st be done done at a rate rate of appr approx ox.. 30°C/h (90°F/h).
6.5.2 6.5.2
Peenin Peening g of weld weld seams seams
Shrinkage Shrinkage impe impedime diments nts produced produced during during cooling cooling of the weld sea seam m may lead to hig high h intern internal al stresse stresses s (tensile (tensile stress) stress) and to cracks. cracks. Unimpede Unimpeded d shrinking shrinking may produce produce mate material rial defo deformati rmations ons (angular (angular shrinkshrinkage). Both these undesired conditions can be remedied by peening.
6.5.2.1 Method of peening Peening is performed after completion of a weld pass which may also consist of several weld beads. Peening of individual beads of a pass is not allowed. During During pee peening ning,, the temperature temperature of the weld seam o should be below 200 C (390°F/h). Except for root and cover cover passe passes, s, all weld passe passes s are to be peen peened. ed. Before peening, all traces of slag and spatter on the weld seam are to be removed. removed. Inad Inadmissi missible ble elevations, tions, notch notches es and pores are to be prope properly rly elimieliminated. The peening chisel has to be run two to three times over the same area of the weld seam at a speed of abt. 100°cm/m 100°cm/minut inute. e. Peen Peening ing must not produce produce any sharp sharp notc notches, hes, grooves and mate material rial overlaps overlaps.. The surface of the weld pass is to be uniformly treated by peening.
The component must be covered with insulant mats throughout the heating-up process. The temp temperatu erature re diffe different rential ial in the comp componen onent, t, e.g. between between high-volume high-volume and comp compact act areas areas and thinwalled, ribbed areas must not exceed 50°C (120°F).
70
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HEAT TREATMENT OF MATERIALS 6.5.2.2 Peening tools Peen Peenin ing g is to be carr carrie ied d out out by me mean ans s of comcompres presse sedd-ai airr oper operat ated ed rive riveti ting ng hamm hammer ers s and flat flat chisels with suitably shaped cutting edges. The riveting hammers must be of handy shape and equipped with a throttle valve to reduce the impact rate. The hammers must be equipped with a chisel guide in the direction of impact. The edges of chisels should have shapes such as shown in fig. 7 and be hardened.
Fig. 7
Material
Chisel
Riveting hammers
Yiel Yield d stre streng ngth th Widt Width h of No. No. of stro stroke kes s of weld cutting edge per min. material b N/mm2
mm
450 to 530
23
600 to 700
18
Table 1:
1700 _ + 10 %
Leng Length th without tool
Pist Piston on Ø Stro Stroke ke Air Air concon- Press Pressur ure e length sumption
mm
mm
mm
l/min.
bar
270 to 325
25 to 30
50 to 100
350 to 550
6
Impa Impact ct force N 300
Technical data of suitable riveting hammers. The width of chisels depends on the yield strength of the weld metal.
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HEAT TREATMENT OF MATERIALS 6.6 6.6
Trea Treatm tmen entt of fille fillerr meta metals ls
Filler Filler me metal tals, s, such such as rod ele electr ctrode odes, s, weldin welding g wire wire coils, coils, weldin welding g powder powder and and weldi welding ng rods, rods, mu must st be stored so as to prevent them from deteriorating. This is only possible in heated rooms at abt. 30°C (90°F) and a relative humidity of below 50 %. The packages must remain closed until the material is used. Unused filler metals must be repacked and brought back into the storage room. Why is this necessary? •
Coatin Coatings gs of rod electrod electrodes es or weldin welding g powder powders s used for submerged-arc welding are hygroscopic, i.e. they absorb ambient humidity. Without protection, these materials get moist or even wet. During welding, the hydrogen and oxygen contained in the water penetra penetrate te into into the weld met metal al and and make it brittle.
Rod ele electr ctrod odes es from from new or alrea already dy opene opened d packpackages ages mus mustt be redrie redried d and and sto stored red in a heate heated d box box until they are used.
Rust, a chemical compound of iron and oxygen, introduces duces unwan unwanted ted am amoun ounts ts of oxyge oxygen n into into the weld weld metal, with the result that the material gets brittle. Corroded Corroded welding wire cont contamin aminates ates the wire guid guide e tubes. tub es. This lea leads ds to an earli earlier er wear wear of the these se ele ele-ments. Corroded Corroded welding wires and welding welding rods therefore therefore have to be discarded.
6.7 6.7
Temp Temper erat atur ure e moni monito tori ring ng
For tem temper peratu ature re mon monito itoring ring during during hea heatt treatme treatment nt processes, the following equipment is recommended: •
Electrical temperature probes: These are easy to handle and provide an exact tempe tem perat rature ure reading reading on an analo analog g or a digita digitall display.
Manufacturers of rod electrodes issue instructions for redrying. •
Manufacturers of rod electrodes issue instructions for redrying.
Adherent thermometers: thermometers: Thermometers with an analog display, which are attached with magnets to the component.
Reference values for electrodes with coating type B: 2h at 350°C (660°F) 3h at 250°C (480°F) 4h at 200°C (390°F) Ther There e is ofte often n a fail failur ure e to ta take ke th this is tire tireso some me but but necessary action. Assistance is now offered by the manufacturers manufacturers of rod electrodes. The rod ele electro ctrodes des are sup supplie plied d in site-res site-resista istant, nt, moisture-impermeable moisture-impermeable special packs.
•
Temperature-indicating Temperature-indicating crayons: These crayons are used to make a mark on the component to be heated. When the desired temperature range is reached, the colour of the mark changes. In principle, this procedure is very simple. It requir requires, es, howev however, er, som some e exp experi erien ence ce with with the crayons to perceive the changing of the colour.
Redrying and keeping warm are no longer necessary if the the rod rod elec electr trod odes es are are used used with within in 8 hour hours s (1 working working shift) of the pack bein being g open opened. ed. Hydrogen Hydrogen content < 5 ml/100 g weld metal. One box (package (package)) therefore therefore contains contains a num number ber of individual packs suitable for use by one welder. The rod electrodes are vacuum-packed firmly together in shrink film. Single rods must not be movable if the packaging is intact. Prior to opening the pack, it must have been brought to the ambient temperature at the application site. Wet rod electrod electrodes es mu must st be des destro troyed yed.. In spite spite of redrying they can never again be used for welding. •
72
Wet welding welding wires wires or welding rods rods are subject to corro corrosio sion. n. The The cop coppe perr coati coating ng of offe fers rs on only ly a temporary protection against corrosion.
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COLD BENDING OF PLATES 7.
Cold Cold bend bendin ing g of plat plates es
Plates can also be treated by cold bending. In cold bending, it is important to observe the minimum admissible bend radii in order to avoid cracks at the edges of the bending areas. The bend radii can be taken from the relevant standards for the different plate materials.
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They depend on the thickness of the plate and the direct direction ion of rollin rolling. g. The min minimu imum m bend bend radii radii transtransverse to the direction of rolling are more favourable than those in the direction of rolling. The minimum bend radius is also influenced by the welding suitability in the bending area. Due to grain coarsening and the ensuing embrittlement of the material during heating after excessive cold bending, the minimum bend radii in accordance with DIN 18800, Part 4, must be observed.
Page 73 Page 73
BUILD-UP WELDING 8.
Buil Buildd-up up weld weldin ing g
The purposes for which build-up welding can be used are manifold. Build-up welding constitutes an important aid in repair practice.
8.1
The welding sequence depends on the hole diameter and the possibility of handling the component (figs. 2 and 3).
Additi Addition on of missin missing g / worn-o worn-out ut materi material al
The additio addition n of ma mater terial ial may be nec necess essary ary due due to wear, deformation, distortion or handling errors during machining. Like Like any oth other er weldin welding, g, build build-up -up weldin welding, g, too too,, requires proper planning of the welding technique and meticulous execution of the practical work. The mech mechano ano-tech -technolo nologica gicall propertie properties s of the weld metal are to be adapted to the requirements of the base metal.
8.1.1
Build-up Build-up welding welding in drill holes
Before carryi Before carrying ng out out build build-up -up weldin welding, g, the worn-o worn-out ut drill hole is to be enlarged by approximately 4 mm (2 mm cutting depth) either on a horizontal boring machine or by manual grinding. This is necessary if the new surface of the drill hole is to coincide coincide after build-up build-up welding welding and machining machining with the homo homogen geneous eous weld meta metall dep deposit osit and not with the relatively hard heat-affected zone.
Fig. 2
The build-up weld must have a sufficient thickness so as to obtain a "clean" drill hole surface.
Fig. 3
For smaller diameters it is common practice to weld the beads parallel to the hole’s longitudinal axis. In large holes, the weld metal can be deposited as a continuous, spiral-welded bead.
Fig. 1
The individual working steps are shown in fig. 1:
1
worn-out hole
2
hole enlarged by drilling
3
steel rings rings tacked to component component as run-off tabs
4
build-up weld
5
run-of run-offf tab tabs s remove removed d and and hole hole machine machined d to finished size
74
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BUILD-UP WELDING
Fig. 4 dem demonstr onstrates ates the recommen recommended ded welding sequence by means of a practical example. Hole (B) of a shovel stick is to receive a new surface by build-up welding. After welding the lower half of the hole, the stick is turned over.
8.1. 8.1.2 2
BuildBuild-up up weldin welding g on worn-o worn-out ut thread threads s (fig. 5)
Fig. 5
Fig. 4
Before carryi Before carrying ng out out build build-up -up weldi welding, ng, the worn-o worn-out ut damaged thread must be cut away on a lathe. The diameter of the shank is to be abt. 4 mm less than the core diameter. Run-out grooves are to be provided in order to ensure that the new contours are located in the homogeneous area of the weld metal. The shank has to be prolonged with a backing strip on which the individual weld beads are to end. If possible, build-up welding is to be performed on a device with which the component can be rotated. The shank can be produced by machining.
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Page 75 Page 75
BUILD-UP WELDING 8.2 8.2
Corr Correc ecti ting ng of of comp compon onen entt shap shapes es to imimprove the flow of forces
Shape-induced notches detected in steel components can be removed by build-up welding.
8.3 8.3
Build Build-u -up p weld weldin ing g as a prot protec ecti tion on agai agains nstt wear
Component surfaces subject to heavy wear can be protected by welding on wear-resistant materials. For details see chapter 9 "Wear protection".
This requires particularly careful work in order not to produce even more detrimental metallurgical notches removing the shape-induced shape-induced notches. Example: Taper between thick and thin plate in the edge zones of the component (fig. 6).
Fig. 6
The surfaces must be ground absolutely smooth and clean, and all grinding drag lines must run parallel to the lines of force.
76
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WEAR PROTECTION 9.
Wear Wear prot protec ecti tion on (har (hardd-fa faci cing ng )
9.2
9.1 9.1
Fun Fundam damenta entals ls
Wear-prone areas are protected by the application of a wear-resistant weld overlay.
Component surfaces subject to strong wear can be given a protection by welding wear-resistant material onto these surfaces. The nee need d to provid provide e wear-p wear-prot rotect ection ion sho should uld be known before the machine is put into operation. If the component is to be hard-faced after putting into operat ope ration ion,, the wear-p wear-prot rotect ection ion mu must st be app applie lied d in time, tim e, i.e. i.e. bef before ore the base base mat materi erial al itself itself begin begins s to show sho w signs signs of wear. wear. A com compo pone nent nt with with worn worn loa loaddbearing elements can no longer be protected properly against wear. The wear protection is not durable, but is also subject to wear and tear. Due to the particular metallurgical prope properti rties es of the hardhard-fac facing ing mat materi erials als,, the rate rate of wear is, however, considerably reduced. The wear wear protec protectio tion n system system mus mustt be regula regularly rly inspected and carefully maintained. It is therefore advisable to provide for regular reworking during machine standstill periods or for a timely replacement of worn-out components. Rework Reworking ing of use used d com compo ponen nents ts can the then n be perperformed in a workshop where more time is available.
BuildBuild-up up weldin welding g of wear wear protect protection ion layers layers
Depen Dependin ding g on the conditi condition ons s of use use,, the choice choice is between a weld metal of high toughness and good impact resistance on the one hand and greater surface hardness on the other. Another important factor to be considered for reworking is the material’s suitability for being welded out of position. An excellent weld metal for this purpose is one containing chromium, tungsten and niobium carbides embedded in a tough matrix and offering at the same time good resistance to abrasive wear and sufficient resistance to impact. Such weld metal has a cumulative hardness of abt. 59 to 61 HRC. For higher values of impact strength, it is advisable to choose another weld metal with a lower hardness of abt. 54 to 56 HRC. The The hard hard and and not very tou tough gh weld weld metal metal tends tends to form form hairl hairline ine cracks cracks on its surfac surface e which which are proproduced by surface stresses (fig. 1).
An attentive and well-trained repair staff can contribute consider considerably ably towards towards achievin achieving g high mach machine ine availability. In the following chapters several wear protection systems are discussed. The question of which system is to be applied applied can be answe answered red only by tak taking ing the specific conditions of use into account. A good decision can be taken only by weighing up and evaluating the advan advantag tages es and and disad disadvan vantag tages es of the syssystems.
Fig. 1
In order to prevent the cracks from running through into the base material, a so-called buffer layer must be provid provided ed for in case case of com compo pone nents nts sub subjec jectt to alternating or pulsating loads. Areas subject to particularly high stresses, such as the side side cut cuttin ting g edge edges s of excava excavatin ting g too tools, ls, sho should uld even be protected by 2 buffer layers (fig. 2).
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Page 77 Page 77
WEAR PROTECTION As to the arrangement arrangement of the welding spots, it is important to take account of the direction of flow of the medium causing the wear (fig. 5).
Fig. 2
The hard-facing build-up weld must always lie exactly on the buffer layer in order to avoid the risk of cracks in the base metal (fig. 2).
Fig. 5
Incorrect Incorr ect placing placing of the spots ma may y lea lead d to scorin scoring g between the rows of spots.
Criss-cross pattern. The criss-cross pattern is to be applied on smaller surfaces subject to high wear. On a criss-cross pattern, soft loading material can be deposite dep osited d in the inte intermed rmediate iate spaces and thus provide vide an extr extra a wear wear prot protec ecti tion on for for the the base base me meta tall (fig. 6).
Fig. 3
9.2.1
Build-up Build-up welding welding patterns patterns
Spot pattern. The spot pattern is suitable for large areas areas which which are subject subject to a relati relativel vely y low risk of wear (fig. 4).
Fig. 6
Fig. 4
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WEAR PROTECTION Full-face build-up welding Relati Relativel vely y sma smallll areas areas sub subjec jectt to heavy heavy wear wear are hard-faced by a full-face build-up weld. This ensures full-face protection of the base material (fig. 7).
9.3.2 9.3.2
For hard-f hard-faci acing ng layers layers
originall Only Only for gravit gravity y positi position on weldin welding, g, e.g. origina hard-facing in the workshop:
Wire electrodes: DIN 8555 : MF 10 - GF - 60 - RT filler wire Ø 2 mm O&K SN 970 133 Reference analysis: C
Cr
Nb
Si
Mn
5.0
22.0
7.0
0.5
0.7
%
Rod electrode DIN 8555 : E 10 - UM - 60 GRZ Ø 5 mm x 450 mm O&K SN 583 471 Reference analysis: Fig. 7
9.2.2 9.2.2 •
•
•
Speci Special al hint hints s
Before Bef ore carrying carrying out out build build-up -up welding welding,, the base base materials are to be preheated depending on their material properties. During welding, welding, the interpass interpass temperature temperature is to be o o kept below 250 C (480 F). Build-up welding welding should should be used only only for the proprotect tectio ion n of base base ma mate teri rial als s with with a hard hardne ness ss not not exceeding a B.H.N. of abt. 300. Due to the welding heat introduced, build-up welding on base materials of greater hardness causes microst microstruc ructur tural al transf transform ormati ations ons in zon zones es of the material close to the surface, with the result that hardness diminishes considerably. considerably.
Another consequence is the formation of high internal stresses in the base material. Only tough base materials can deal with these internal stresses, such as materials with a max. B.H.N. of 300 .
9.3 9.3
Fill Filler er metal etals s
9.3.1 9.3.1
For buffer buffer layers layers
Rod electrodes: EN 499: E 38 2 RA 22 AWS 5.1: E 6013
C
Cr
Nb
V
Mo
W
5.0
22.0
8.0
1.5
8.0
2.5
%
For out-of-position welding, e.g. subsequent hardfacing in the field: Rod electrode: DIN 8555 - E 6 - UM - 60 P basic-type coating alloyed core wire O&K SN 1 939 533 Trade name: EA 600 Kb : VALCO D¨usseldorf usseldorf Reference analysis: C
Cr
Si
Mn
0.5
6.0
1.3
1.3
%
Key: R Z P UM MF GF T G
= = = = = = = =
rust-proof heat-resistant impact-re -resistant coated metal me tal-ar -arc c weldi welding ng with with filler filler wire wire flu flux-fi x-fill lle ed high high-t -tem empe pera ratu ture re resi resist stan antt ab abrasi rasio on-re -resist sista ant
Wire electrodes: EN 440: G 3 Si 1 AWS 5.18: ER 70 S-6
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Page 79 Page 79
WEAR PROTECTION 9.4 9.4
Repa Re pair ir of buil buildd-up up weld welds s
State of wear 2 (fig. 9)
Worn-out build-up welds must be repaired by rewelding, if required. Rewelding should be performed as long as remaining parts of the buffer layer are still visible. Befo Before re rewe reweld ldin ing, g, a surf surfac ace e crac crack k te test st has has to be carried out. It is absolutely essential to gouge out any cracks in the base metal or the buffer layer before welding is performed. Cracks should never be overwelded!
9.4.1 9.4.1
State State of wear wear Fig. 9
The The repa repair ir me meas asur ures es to be ta take ken n depe depend nd on th the e material’s state of wear.
•
The hard-facing hard-facing layer layer is completely completely worn out.
State of wear 1 (fig. 8)
•
The buffer buffer layer is almost worn out.
Repair measure: Weld 1 new buffer layer and 2 new hard-facing layers.
State of wear 3 (fig. 10)
Fig. 8 •
The hard-facing hard-facing layer layer is almost worn out.
•
The buffer buffer layer is still fully fully intact. Fig. 10
Repair measure: Weld 2 new hard-facing layers. •
Hard-f Hard-faci acing ng and and buffe bufferr layers layers have have been been com com-pletely abraded down to the base metal.
Repair measure: Weld 1 new buffer layer and 2 new hard-facing layers.
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WEAR PROTECTION State of wear 4 (fig. 11)
9.4.2
Identificati Identification on of buffer buffer and hard-facing hard-facing layers
The following are hints to identify the individual layers of build-up welds: The existence of remaining parts of the hard-facing can be identified by grinding (fig. 12).
Fig. 11 •
Hard-faci Hard-facing ng and buffer buffer layers are partly partly worn out or broken off.
Repair measure: The remainders of hard-facing have to be removed by ARC-AIR gouging (cf. page 23). Fig. 12
Never knock off remaining parts of the hard-facing layer. Flying fragments may cause injury!
The sparks produced by grinding a hard-facing layer are are dark dark red. red. They They fly fly away away in a line linear ar path path and and almost without branching.
The gouged gouged-ou -outt area area is to be ground ground smooth smooth and and clean before welding 1 new buffer layer and 2 new hard-facing layers onto the base metal.
A buffer layer consisting of an austenitic, i.e. corrosion-resi sion-resistant stant,, weld material can be recognize recognized d by the bright colour of the grinding sparks. If the buffer layer consists of a ferritic weld metal, the grindi grinding ng spa sparks rks are light light red. red. They They branch branch out and and spatter (fig. 13).
Fig. 13
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Page 81 Page 81
WEAR PROTECTION 9.5 9.5
Repa Re pair ir of crac cracks ks in buil buildd-up up weld welds s
Damage Damage conf configura iguration tion:: The crack in the comp componen onentt lies in the area of the build-up weld (fig. 14).
Gouge out the crack in the base metal properly and in accord accordan ance ce with with sta stand ndard ard practi practice ce (cf. pag page e 23) 23) and weld (fig. 16).
Fig. 16 Fig. 14
5
Run-off tab
1 Crack 2 Hard-facing 3
Base metal
4
Cracked zone
Restore the cover over the repair zone by welding the buffer and hard-facing layers (fig. 17).
First, First, remove remove the hardhard-fac facing ing in the cracke cracked d area area completely (fig. 15). The hard-fa hard-facin cing g layer layer can be remove removed d only only by the ARC-AIR procedure.
Fig. 17
Fig. 15
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WEAR PROTECTION 9.6 9.6
Weld Weldin ing g on on wear wear-r -resi esist stan antt stee steell pla plates tes or steel strips
For For weldin welding g ont onto o curved curved surfac surfaces es with with very very great great radii, the strips should be abt. 100 x 400 mm and equally arranged in a staggered pattern (fig. 19).
Wear-resistant plates or strips with Brinell hardness numb number ers s of up to 500° 500°C C an be weld welded ed onto onto th the e surfaces to be protected.
9.6.1
Arrangemen Arrangementt of plates/strip plates/strips s
For weldin welding g ont onto o pla plane ne surfac surfaces, es, the wear wear pla plates tes should have a size of abt. 200 x 300 mm and be arranged in a staggered pattern (fig. 18).
Fig. 19
The strips must not be deformed. The gap caused by the curvature of the underlying metal should, if possible, be the same on both sides (fig. 20).
Fig. 18
The plates plates mu must st be in perfec perfectt con contac tactt (i.e. (i.e. withou withoutt any gap, if possible) with the surfaces to be protected. If the plates are greater than recommended and if their contact with the surface is insufficient, they are susceptible to cracking or fracturing under compressive or impact loads. Fig. 20
The stresses produced by pressing the plates against the surface may lead to the formation of cracks in the weld seams. Observation of the recommended plate size moreover allows allows partially partially worn-out worn-out areas areas to be repaired repaired more easily.
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The spacing between the plates or strips should not be too large (fig. 21), so that loading material can fill the spaces between the plat plates, es, thus protectin protecting g the weld seams against wear.
Page 83 Page 83
WEAR PROTECTION For a spacing of the plates as a function of the plate thickness see fig. 21.
Fig. 21
t
= 10 mm 15 mm 20 mm
a =
6 mm 8 mm 10 mm
b = 20 mm 25 mm 30 mm
The welds in the flow direction of the medium wear substantially faster than welds positioned transverse to them (fig. 22).
Fig. 23
The side blades of bucket front sections and backhoes can be protectd with wear strips. These strips must be made in one piece. They must end in an area with low working stresses (Fig. 24).
Fig. 22
Narrow areas, e.g. at side walls (arrow, figs. 22 and 23) of bucket fronts and backhoes should therefore be fitted with interrupted strips. • Tran Transv sver erse se join joins s or slot slots s are are fill filled ed in with with th the e medium, forming a self-protection for the welds. • The slipping slipping of the medium medium is interrupted interrupted by the joins or slots. The medium rolls, reducing the wear. Circular weld openings should be avoided, as experience shows that the opening fail to fill in. Large parts of the weld and of the plate metal are subject to wear.
84
Fig. 24
Make long, tapering build-up welding at the ends of the wear strip. Grind Grind transi transitio tions ns from from weld weld me metal tal to base base ma mater terial ial notch-free.
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WEAR PROTECTION
The welds in longitudinal direction of the strips must be protected in their layout. Possible layouts:
1.
3.
The welds are are severely susceptible susceptible to wear. The The layout is not recommended (fig. 25).
The welds welds are optimally protected. The The layou layoutt of the wear wear strips strips is recom recommen mende ded d (fig. 27).
Fig. 27 Fig. 25
2.
The The welds welds are suscep susceptib tible le to wear wear as the excavating device moves back. The cutting edge is substantially widened. The penetration resistance is increased (fig. 26).
4.
This layout layout is recommended recommended only only if the side side walls are also fitted with wear plates. The welds are then protected from wear (fig. 28).
Fig. 28
Fig. 26
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Page 85 Page 85
WEAR PROTECTION
The gaps between the plates of the 1st row must be closed by build-up welding. If this is not done, the wear plates in the 2nd row behind the gaps may close (become joined up).
The welds for fixing the plates and strips consist of soft weld metal which is not resistant to wear. This is necessary due to the types of material used in the base body and the wear plates. Welds positioned in flow direction in particular should theref the refore ore be given given a "ha "hard" rd" cover cover to protec protectt the them m from excessively rapid wear.
Fig. 29
Explanations of fig. 29:
1
Direction of flow of medium
2
Fillet welds
3
Hard-faced deposit
Fig. 30
Explanations of fig. 30:
86
1
Metal plate, base material, material, e.g. S690Q S690Q
2
Wear plate, hardness: ca. 500 500 HB
3
Wear plate, plate, hard hard layer on soft carrier material material
4
Weld metal, soft
5
Weld metal, soft, buffer pass
6
Weld metal, hard, hard-faced deposit
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WEAR PROTECTION 9.6.2 9.6.2
Bendin Bending g of strips strips
Strips of a material with a B.H.N. of max. 400 can be worked by cold bending and adapted to curved surfaces (fig. 31).
Fig. 31
However, bending must be done on a bending roll and not on an edging press. Due to bending radii and spring action, bending by gradual edging would lead to cracks on the side of the wear plate subject to tension. Worn-out plates and strips must always be replaced in time. Rema Remain inin ing g piec pieces es of th the e wear wear plat plate e ma may y not not be remo remove ved d by wedg wedgin ing g (fig. (fig. 32), 32), unle unless ss a notc notch h is grou ground nd into into the the weld weld seam seam in orde orderr to crea create te a predetermined predetermined breaking point. The cutting areas must be ground smooth and clean and be free from cracks.
9.6.3 9.6.3
Workin Working g instru instructio ctions ns
•
Plates Plates with Brinell Brinell hardness hardness numbers numbers exceedin exceeding g 300 must not be treated by hot bending or hot straightening.
•
Plates Plates and strips must not be welded welded onto highly highly stressed component edges.
•
Plates Plates and strips strips mu must st be fasten fastened ed to the base base material with a continuo material continuous us fillet fillet weld running running all around. Tack-welding is not sufficient.
•
"Soft" "Sof t" filler metals metals are used for welding. welding. This applies also to the top pass of the fillet weld.
•
The The base base mat materi erial al must be preheat preheated ed in accoraccordance with the mate dance material rial qualities, qualities, at least, least, however, to abt. 100oC (210oF).
•
For For thickn thickness esses es up to 20 mm mm,, the wear wear pla plates tes must be preheated to at least 100 oC (210oF). For thicknesses of 40 mm, a preheating temperature of 200oC (300oF) is required.
•
The interpass interpass temp temperatu erature re during welding must not exceed 250 oC (480oF).
9.6. 9.6.4 4
Fill Filler er metal metals s
Rod electrodes: EN 499: E 38 4 B 42 AWS 5.1: E 7018 Wire electrodes: EN 440: G4 Si 1 AWS 5.18: ER 70S-6
Fig. 32
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Page 87 Page 87
WEAR PROTECTION 9.7 9.7
Weld Weldin ing g of pla plate tes s or stri strips ps wit with h wear wear-r -reesistant coatings
Plates or strips of S275JRG2/S355J2G3 with a previously welded wear-resistant coating with a hardness of up to 58 HRC HRC ma may y also also be weld welded ed ont onto o th the e surfaces to be protected. The plate thickness depends on the size of the excavating tool. If the recommended plate thicknesses are used, the spaci spacing ng be betwe tween en the the pla plates tes sho shoul uld d be 15 mm (fig. 33).
Fig. 35
9.7.1 9.7.1 •
The strips must be attached attached by cont continuo inuous us fillet welds of a = 6 mm thickness running all around.
•
"Soft" filler metals metals are used for welding welding (cf. 9.6.4). 9.6.4). This applies also to the top pass of the fillet weld.
•
Strips Strips must not be welde welded d ont onto o hig highly hly stressed stressed component edges. component
•
The The base base mat materi erial al must be preheat preheated ed in accoraccordance dan ce with the mate material rial qualities, qualities, at least, least, however, up to abt. 100oC (210oF).
•
The strips are normally normally not not preheated. preheated. Exceptio Exceptions: ns: Compon Component ent and amb ambient ient temperatemperao o tures tures are below below 20 C (70 F) and and the the stri strips ps are are moist.
•
With regard regard to the base metal, metal, the interpa interpass ss temperature perature during welding must not exceed 250oC (480oF).
•
Worn-out strips must be be replaced in time. Remain Remaining ing pieces pieces of the strips strips ma may y not not be removed mo ved by wedgin wedging, g, unles unless s the weld weld sea seams ms are notched notc hed by grinding grinding in order order to create create predeterpredetermined breaking points. Cf. also fig. 32.
•
The The cut cuttin ting g areas areas must must be groun ground d smo smooth oth and clean and be free from cracks before new strips are welded on.
•
The prefabr prefabricate icated d strips can can be cut with a plasma torch. torch. If this this is not not possi possible ble,, the base ma mater terial ial must be cut by grinding or gouging, and the hard layer be broken.
Fig. 33
Plate thicknesses: e.g. A
B
C
13 19 25
8 13 19
5 6 6
The plates or strips should be abt. 100 x 400 mm and arranged in a staggered pattern (fig. 34).
Fig. 34
The strips must not be bent. They can nevertheless be welde welded d onto onto curved curved surfac surfaces es with with large large radii radii if their central part rests on the base metal and if the gap at the long sides of the strips is relatively small and of equal size on the right and left sides (fig. 35).
88
Workin Working g instru instructio ctions ns
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WEAR PROTECTION 9.8 9.8
Weld Weldin ing g of wear wear-r -resi esist stan antt stud studs s
Studs of wear-resistant materials can be welded onto the surfaces to be protected. Studs of differ Studs differen entt sizes, sizes, sha shape pes s and and hardn hardness ess are available from dealers specializing in these articles.
Process desription (fig. 36) •
The The stud studs s are are fast fasten ened ed to the the weld weldin ing g devi device ce together with the ceramic weld backing. The ceramic ramic backi backing ng ring ring con confin fines es the weld weld poo pooll and and protects it against external influence.
•
The The arc is ignited ignited by pullin pulling g the stud away from from the component surface, whereby parts of the stud and of the base metal are melted.
•
The stud is is pressed into the liquid weld pool. After cooling the stud is completely welded to the base metal.
Welding procedure: Initial contact capacitor-discharge capacitor-discharge stud-welding This type of welding requires high-current power supplies.
Before welding it must be checked whether the power supply available on site has sufficient capacity for weld finishing.
9.8.1 9.8.1
Workin Working g instru instructio ctions ns
•
The studs should should be placed placed as closely together together as possi possible ble.. The The distan distance ce betwe between en stu studs ds is deter deter-mined by the size of the ceramic backing ring. Close Close spa spacin cing g of the stu studs ds ens ensure ures s tha thatt forces forces acting on the studs are distributed more evenly to an as large large number number of stu studs ds as possi possible ble,, thu thus s reducing the danger of stud fracturing.
•
Depending Depending on the material material quality, quality, the base metal metal must be correspondingly preheated, at least, however, to 100 oC (210oF).
•
Studs must not be be welded onto componen componentt edges or component radii.
For instructions on the procedure as well as on studs and and too tools, ls, the use userr is adv advise ised d to con contac tactt spe specia cialis listt firms. Stud welding has proved a successful wear protection procedure worldwide. Reweld Rewelding ing of single single studs broken broken out out of the base base material cannot be recommended. In most cases, the breaking point in the base metal cannot be ground as smooth as required.
Fig. 36
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Page 89 Page 89
WEAR PROTECTION 9.9 9.9
Weld Weldin ing g cut cutti ting ng edge edges s ont onto o dig diggi ging ng tool tools s of excavators
Prefa Prefabr bric icat ated ed cutti cutting ng edge edges s (1, (1, fig. fig. 37) 37) of high high-streng strength, th, tem tempe pered red ste steel el can be welde welded d to the excavating cavating tool (2) as a wear-prot wear-protectio ection n mate material rial with good cutting capability.
To facilitate fastening and welding, the excavating tool should be placed with its blade in a vertical position. For weldin welding, g, prehea preheatt bla blade de cut cuttin ting-e g-edge dge and replacing part to 150 oC (300oF).
9.9. 9.9.2 2
Weld Weldin ing g metals
seq sequence ence
(fig (fig.. 39) 39) and and
fill filler er
Fig. 37 Fig. 39
9.9.1 9.9.1 •
Workin Working g sequen sequence ce
The contour contour of the worn-out worn-out cutting cutting segment segment is to be cut straight by means of a flame torch. Before flame-cu flam e-cuttin tting, g, prehea preheatt to 50oC (120 (120oF). Grind Grind flame-cut edges down to the bare metal.
•
Make a replacing replacing part with the help help of a template. template. Material:: wear-resi Material wear-resistan stantt temp tempered ered stee steel; l; preshaped, available e.g. from the O&K spare-parts service.
•
For cutting out the contour contour and for chamfering chamfering the weld weld groove grooves, s, prehe preheat at the ma mater terial ial to 50 oC (120oF). Grind the weld groove surfaces smooth down to the bare metal.
•
Attach replacing part (fig. 38).
Weld first the root and 1 interpass from one side using soft filler metals.
Filler metals (soft) for root and 1st interpass Rod electrodes EN 499: E 38 4 B 42 AWS 5.1: E 7018 7018 Wire electrodes EN 440: G4 Si 1 AWS 5.18: ER ER 70S-6 Grind out the root pass from the other side and weld 2 layers as on the other side. Finish the remaining weld with filler metals adapted to the the ma mate teri rial al of the the cutt cuttin ing g edge edge (cf. (cf. page page 90). 90). Weld stringer stringer bead beads; s; inte interpas rpass s welding welding temp temperatu erature re o o max. 250 C (480 F). Work alte Work altern rnat atel ely y on both both side sides s in orde orderr to avoi avoid d distortion of the replacing part.
Fig. 38
90
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WEAR PROTECTION Filler Filler metals metals (hard (hard)) for inter interpas passes ses and cover cover passes Rod electrodes EN 757: E 69 5 Mn2NiCrMo B 42 AWS 5.5: E 11018 - M Trade names Thyssen: Kjellberg-Esab: Oerlikon:
SH Ni 2 K 100 OK 75,75 Tenacito 75
Wire electrodes not yet standardized Trade names Thyssen: Boehler:
Union Ni Mo Cr Ni Cr Mo 2,5 - IG
The seam ends at the transition to the tooth holders must be ground smooth and clean (arrows, fig. 40).
Fig. 40
The entire welding area must be allowed to cool down slowly after completion of the weld. Cover up with glass wool. Never cool with water or jets of compressed air.
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Page 91 Page 91
REPAIR OF CAST-IRON COMPONENTS 10.
10.1 10.1
Repair Repair of cast-iro cast-iron n component components s by welding Sphero Spheroida idal-g l-grap raphit hite e cast cast iron iron
Basically Basically 2 meth methods ods requiring requiring different different amou amounts nts of work can be app applied lied.. Though Though requiring requiring the greater amount of work, hot welding mostly yields the better results.
10.1.2 Cold welding welding Weldin Welding g is carrie carried d out out with with filler filler me metal tals s of differ differen entt compositions to the base metal. If the work is carried out out in a workma workmanl nlike ike manner, manner, the weld weld me metal tal obobtaine tained d corres correspo ponds nds to the B-qua B-qualit lity y level level in accoraccordanc dance e with with the the VDG VDG Code Code of Prac Practi tice ce N 60. 60. The The weld diffe differs rs in its mech mechanoano-tech technolo nologica gicall propertie properties s from the unwelded material, although in most cases the weld fulfil fulfils s the requirem requirement ents s for a given given use use.. Such requirements have to be defined for each special case.
10.1.1 Hot welding welding
Welding recommendations:
Weldin Weld ing g is carr carrie ied d out out with with th the e fill filler er me meta tall of th the e same composition as the base. If the work is carried out out in a workma workmanli nlike ke man manne ner, r, the weld me metal tal obobtaine tained d corres correspon ponds ds to the A-qua A-qualit lity y level level in accoraccordanc dance e with with the the VDG VDG Code Code of Prac Practi tice ce N 60. 60. The The mechano-technological properties of the weld deposit are identical to those of the unwelded material.
•
Keep the weldin welding g current current as low as possible, possible, so thatt the hea tha heat-af t-affect fected ed zon zone e remain remains s extreme extremely ly narrow.
•
Preheati Preheating ng tempe temperatur ratures es of up to 400oC (750oF) have a strengthening effect on the welded joint.
•
The The weldin welding g areas areas must be clean clean down to the bare metal.
For welding, it is required to preheat the workpiece to 600oC (1100oF). After welding, the component must be subjected to normalizing at 900 oC (1650oF).
•
Because Because of this requiremen requirement, t, the procedure procedure can be virtually excluded for field repairs. Moreov Moreover, er, the com compon ponent ent is sub subjec jected ted to great great amounts of heat, so that the dimensional accuracy of machined surfaces can no longer be guaranteed. For repairs requiring this type of welding, it is always advisabl advisable e to cont contact act a comp company any specializing specializing in this field of welding repair, because only these companies have have the neces necessar sary y equip equipme ment nt for prehe preheati ating ng and and normalizing as well as for handling hot components.
•
Rod electrodes: DIN 8573 - Typ E NiFe - 1 - BG 23 AWS 5.15: E NiFe - C1 Electrodes - Ø 3.20 mm O&K SN 8 432 629 Weld short short stringer beads beads and provide for interpass cooling.
Normalization after welding is not required. After grinding, the welded area should be checked for cracks by means of the dye-penetration test. Cold Cold weldin welding g by ine inexpe xperie rience nced d welde welders rs may yield yield poor results. It is therefore advisable to contact specialized companies for this work as well.
92
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REPAIR OF CAST-IRON COMPONENTS 10.2 10.2
FlakyFlaky-gra graphi phite te cast cast iron iron
Here again, 2 methods requiring different amounts of work can be app applied lied.. Though Though requiring requiring the greater amount of work, hot welding mostly yields the better results.
10.2.1 Hot welding welding Welding is carried out with a filler metal of the same composition as the base metal. If the weld is carried out in a workmanlike manner, the weld deposit obtained taine d correspon corresponds ds in its mech mechanoano-techn technolog ological ical properties to those of the unwelded material. For welding, the component must be partly or completely preheated to 650 oC (1200oF). As the fluidity of the weld metal is very high, the welding area as such must be confined by backing devices. Because Because of this requiremen requirement, t, the procedure procedure can be virtually excluded for field repairs. Moreov Moreover, er, the com compon ponent ent is sub subjec jected ted to great great amounts of heat, so that the dimensional accuracy of machined surfaces can no longer be guaranteed. For repairs requiring this type of welding, it is always advisabl advisable e to cont contact act a comp company any specializing specializing in this field of welding repair, because only these companies have have the neces necessar sary y equip equipme ment nt for prehe preheati ating ng and and normalizing as well as for handling hot components.
10.2.2 Cold welding welding Welding is carried out with weld filler metals of different compositions to the base metal. If the weld is carried out in a workmanlike manner, the weld metal obtained differs in its composition from the base material terial and pos possess sesses es oth other er mec mechan hano-te o-techn chnolo ologica gicall prope properti rties es tha than n the latter latter.. A homo homogen geneo eous us welde welded d joint between base metal and filler material cannot be expected.
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Therefore, it is not possible to restore all the component’s original material properties. Microstructural changes in the edge zones and high internal stresses cannot be avoided. Due to inevitably high structural structural hardenin hardening, g, microcrack microcracking ing cann cannot ot be excluded.
Welding recommendations: •
Keep Keep the welding welding curren currentt as low as possi possible ble in order to keep heat application to a minimum.
•
The temperatu temperature re in the workpiece workpiece should should not exceed 70oC (160oF)in an area directly adjacent to the weld.
•
Rod electrodes: DIN 8573 - type E NiFe AWS 5.15: E NiFe - C1 Electrodes - Ø 2.5 mm. O&K SN 8 432 648
•
Always Always weld short stringer stringer beads beads in a staggered staggered pattern.
•
In order order to reduce reduce shrinka shrinkage ge and thu thus s intern internal al stresses in the component, the beads should be slightly extended before cooling by hammering.
Cold Cold weldin welding g sho should uld only be carrie carried d out on flakyflakygraphite graphite cast-iron cast-iron comp compone onents nts if it is abso absolutel lutely y indispensable. It is advisabl advisable e to cont contact act speciali specialized zed companies companies to carry out this work.
Alternative recommendation: For the repair of flaky-graphite cast-iron components another ano ther procedu procedure re can be successful successfully ly app applied lied,, i.e. the so-called "interlock" method. Repair Repair by mea means ns of the "interlo "interlock" ck" me metho thod d can be carried out only by special firms. For details see paragraph 10.2.3.
Page 93 Page 93
REPAIR OF CAST-IRON COMPONENTS The holes are drilled by means of a template. The rema remain inin ing g me metal tal betwe between en the the drilldrill-ho holes les is reremoved by chipping.
10.2.3 Repair of componen components ts with the "interlock" "interlock" technique The repair repair of cast-i cast-iron ron com compo pone nents nts by weldin welding g is often not possible if the repaired area is subject to the action of forces.
•
So-called "interlocking bars" are then then inserted into these joints (fig. 2).
For this this reason reason,, a tec techn hniqu ique e has has been been devel develop oped ed where cracks or fractures are repaired by "interlocking". Such repair is carried out by means of mechanical tools only and requires no welding. This This proced procedure ure represe represents nts nev neverth erthele eless ss a use useful ful complementary complementary technique to welding. Interlocking can be used to join fragments or, if required, newly made replacing pieces of another material, e.g. of cast steel or plate steel.
Process description: •
The The com compo pone nent nt is prepa prepared red by drilli drilling ng rows of holes on both sides and across the fracture line (fig. 1).
Fig. 2
These bars are made of a steel material which can be deformed and solidified by hammering. •
The bars are inserted into the joints in layers, layers, with every eve ry single single layer layer being being hamm hammere ered d in pla place. ce. In the proces process, s, the interl interlock ocking ing bars bars are mo mould ulded ed exactly to the shape of the joints. This ensures that also the rear areas contribute to the load-bearing capability of the bars.
•
The substitute substitute cross-sectio cross-section, n, i.e. the number number of bars, can be calculated from the ratio of the material strength values of grey cast-iron and steel.
Fig. 1
94
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TOUCHING UP OF PAINT COATINGS IN REPAIR AREAS 11.
Touching Touching up paint coatings coatings in repair repair areas
All damaged or partly removed coatings of the component must be touched up after completion of the weld. This applies to areas in which -
welding has been been carried carried out, out,
-
addition add itional al reinforcing reinforcing plates have been fitte fitted d or inserted,
-
coatin coa tings gs have have been been damag damaged ed by the therma rmall (e.g. (e.g. straightening, preheating) or mechanical (e.g. lifting gear) action.
The The dama damage ged d area areas s of th the e comp compon onen entt are are to be cleaned by mechanical procedures, such as brushing, grinding or scraping. Surface purity: St 3 in acc. with DIN 55 928, Part 4, supplement supplement 1. The degree of purity required by this standard can be achieved only by thorough cleaning. The repaired area is then to be touched up with 2 coats of paint, a priming and a finishing coat. The priming coat must ensure that the metal surface is covered up with a sufficient overlap. In the same way, the finishing coat has to sufficiently overlap the priming coat.
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Page 95 Page 95
APPENDIX Comparison
Old designation
New designation
Materials DIN 17100: St37-2 DIN17100; St52-3 DASt DASt-d -dir irec ecti tive ve 01 011 1: StE StE69 690 0 LV 976752: GS-52.3V Swed Swedis ish h Stee Steel: l: HARD HARDOX OX 500 500
EN 10025: S275JRG2 EN 10025: S355J2G3 SEW SE W 69 690 0 Pa Part rt 1: S6 S69 90Q LV 2102375; GS-21 -21 Mn5V (as (as per SEW 685) LV 2270 227000 002: 2: wear wear plat plate e 500H 500HB B
Filler metals for welding DIN 1913: E4332AR7 DIN 1913: E5154B10 DIN 8559: SG2 DIN 8559: SG3 DIN 8529: 8529: EY6 EY697 975Mn 5Mn2Ni 2NiCrM CrMoB oB
96
EN 499: E38 2 RA 22 EN 499: E38 4 B 42 EN 440: G3Si1 EN 440: G4Si1 EN 757 757:: E69 5 Mn2 Mn2NiC NiCrMo rMoB B 42
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APPENDIX Part nos. for filler metals The filler metals listed below can be obtained from the O&K spare-parts service. For orders, please quote part no., quantity and designation of the filler metal required.
Rod electrodes Standard designation
Dimensions (mm)
Part no. for 1 pack
EN 499: E 38 2 RA 22
Ø Ø
4.0 x 450 5.0 x 350
1 367 155 0 583 352
EN 499; E 38 4 B 42
Ø Ø Ø Ø
2.5 x 250 3.2 x 450 4.0 x 450 5.0 x 450
0 583 320 0 425 080 0 425 081 0 425 079
EN 757: E 69 5 Mn2NiCrMoB42
Ø Ø Ø
3.2 x 350 4.0 x 450 5.0 x 450
2 115 741 2 115 742 0 583 344
DIN 8555-E10-UM-60 GRZ DIN 8555-E6-UM-60 P
Ø Ø
5.0 x 450 3.20 x 450
0 583 471 1 939 533
DIN 8573 E NiFe 1 BG 23
Ø Ø
2.5 x 250 3.2 x 350
8 432 648 8 432 629
DIN 8575 E CrMo1B 26
Ø Ø Ø
3.2 x 350 4 4..0 x 350 5.0 x 350
1 009 270 0 583 341 0 583 354
Remarks
2. Rod electrodes, vacuum-packed Standard designation
Dimensions (mm)
Part no. for 1 vacuum pack
EN 499 E 38 4B 42
Ø 2.5 x 250 Ø 3.2 x 450 Ø 4.0 x 450 Ø 5.0 x 450
1 465 519 1 465 520 1 465 521 1 465 522
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Remarks
Page 97 Page 97
APPENDIX
3. Wire electrodes Standard designation DIN 8555-MF 10-GF 60-RT EN 440: G3 Si 1 EN 440: G4 Si 1 DIN 8575: SGCrMo1 Wire electrode (not yet standardized)
Dimensions (mm)
P/N for 15 kg coil
Ø 2.0 Ø 1. 2 Ø 1. 2 Ø 1.2 Ø 1.2
0 970 133 0 986 861 0 061 147 0 249 785 8 708 592
Remarks
Fa. Thyssen: Union NiMoCr oder Fa. Bohler: ¨ NiMoCr 2.5-IG
4. Carbon electrodes for "ARC-AIR Procedure" Standard designation
Dimensions (mm)
Part no. for 1 pack
Carbon electrode
Ø 5.0 x 300 Ø 6.0 x 300 Ø 8.0 x 300
0 589 076 0 788 314 0 530 884
98
Remarks
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APPENDIX Umrechnung von foot (Fuß) und inch (Zoll) in Meter Conversion from foot (Fuß) and inch (Zoll) to metric measure 1 in (inc (inch) h) = 25,4 25,4 mm (gen (genau au)) 1 in (inch) = 25,4 mm (exact)
1 ft (foo (foot) t) = 12 in = 304, 304,8 8 mm
Beis Beispi piel el:: 4 ft 2 in = 1,27 1,27 m Example: 4 ft 2 in = 1,27 m
in +0
+1
+2
+3
+4
+5
+6
+7
+8
+9
+10
+11
m
m
m
m
m
m
m
m
m
m
m
m
ft
0
0.0 0.0254 0.0 0.05 508 0.0 0.07 762 0,1 0,10 016 0,1 0,12 270 0,1 0,15 524 0,1 0,17 778 0, 2032 0,22 ,2286 0,2 0,25 540
1
0,30 0,3048 48 0,330 0,3302 2 0, 0,35 3556 56 0,381 0,3810 0 0, 0,40 4064 64 0,431 0,4318 8 0,45 0,4572 72 0,482 0,4826 6 0.50 0.5080 80 0.533 0.5334 4 0.55 0.5588 88 0.58 0.5842 42
2
0,60 0,6096 96 0,635 0,6350 0 0, 0,66 6604 04 0,685 0,6858 8 0, 0,71 7112 12 0,736 0,7366 6 0,76 0,7620 20 0,787 0,7874 4 0,81 0,8128 28 0,838 0,8382 2 0,86 0,8636 36 0,88 0,8890 90
3
0,91 0,9144 44 0,939 0,9398 8 0, 0,96 9652 52 0,990 0,9906 6 1. 1.01 0160 60 1.041 1.0414 4 1.06 1.0668 68 1.092 1.0922 2 1,11 1,1176 76 1,143 1,1430 0 1,16 1,1684 84 1,19 1,1938 38
4
1,21 1,2192 92 1,244 1,2446 6 1, 1,27 2700 00 1,295 1,2954 4 1, 1,32 3208 08 1,346 1,3462 2 1,37 1,3716 16 1,397 1,3970 0 1,42 1,4224 24 1,447 1,4478 8 1,47 1,4732 32 1,49 1,4986 86
5
1.52 1.5240 40 1.549 1.5494 4 1. 1.57 5748 48 1,600 1,6002 2 1, 1,62 6256 56 1,651 1,6510 0 1,67 1,6764 64 1,701 1,7018 8 1,72 1,7272 72 1,752 1,7526 6 1,77 1,7780 80 1,80 1,8034 34
6
1,82 1,8288 88 1,854 1,8542 2 1, 1,87 8796 96 1,905 1,9050 0 1, 1,93 9304 04 1,955 1,9558 8 1,98 1,9812 12 2.006 2.0066 6 2.03 2.0320 20 2.057 2.0574 4 2.08 2.0828 28 2,10 2,1082 82
7
2,13 2,1336 36 2,159 2,1590 0 2, 2,18 1844 44 2,209 2,2098 8 2, 2,23 2352 52 2,260 2,2606 6 2,28 2,2860 60 2,311 2,3114 4 2,33 2,3368 68 2,362 2,3622 2 2,38 2,3876 76 2,41 2,4130 30
8
2,43 2,4384 84 2,463 2,4638 8 2, 2,48 4892 92 2.514 2.5146 6 2. 2.54 5400 00 2.565 2.5654 4 2.59 2.5908 08 2,616 2,6162 2 2,64 2,6416 16 2,667 2,6670 0 2,69 2,6924 24 2,71 2,7178 78
9
2,74 2,7432 32 2,768 2,7686 6 2, 2,79 7940 40 2,819 2,8194 4 2, 2,84 8448 48 2,870 2,8702 2 2,89 2,8956 56 2,921 2,9210 0 2,94 2,9464 64 2,971 2,9718 8 2,99 2,9972 72 3.02 3.0226 26
10
3.04 3.0480 80 3.0734 3.0734 3. 3.09 0988 88 3, 3,12 1242 42 3, 3,14 1496 96 3, 3,17 1750 50 3,20 3,2004 04 3,22 3,2258 58 3,2 3,251 512 2 3,27 3,2766 66 3,30 3,3020 20 3,32 3,3274 74
11
3,35 3,3528 28 3,3782 3,3782 3, 3,40 4036 36 3, 3,42 4290 90 3, 3,45 4544 44 3, 3,47 4798 98 3.50 3.5052 52 3.53 3.5306 06 3.5 3.556 560 0 3.58 3.5814 14 3,60 3,6068 68 3,63 3,6322 22
12
3,65 3,6576 76 3,68 3,6830 30
3, 3,70 70
0,27 ,2794
3, 3,73 7338 38 3,75 3,7592 92 3,78 3,7846 46 3,81 3,8100 00 3,83 3,8354 54 3,86 3,8608 08 3,88 3,8862 62 3,91 3,9116 16 3,93 3,9370 70
Umrechnung von L¨angen - Maßen Conversion for units of length La¨ nge Length
in
ft
yd
1 inch (Zoll)
1
0,0833
0,0278
1 foot (Fuß)
12
1
0,3333
0,00019
1 yard
36
3
1
1 statute mile (Landmeile)
63 360
5 280
1 UK nautical mile (engl. Seemeile)
72 960
1 cm 1m
2 en - (0)
m il e
cm
m
2,54
0,0254
0,00016
30,48 30
0,3048
0,00057
0,00049
91,44
0,9144
1 760
1
0,86842
1609,3
6 080
2 026,7
1,15151
1
1 853,2
0,3937
0,0328
0,0109
39,370
3,2808
1,0936
0,00062
UK n mile
0,00054
1
0,01
100
1
Page 99 Page 99
APPENDIX Temperatur - Einheiten und Umrechnungsformeln Umrechnungsformeln Temperature Temperature units and conversion formulas Einheiten Units
Umrechnung in Conversion into
Benennung Nomenclature Kurzzeichen Symbol
o
K
C
o
R
o
F
1
(K-273.16o)
4/ 4/5 5 (K-2 (K-273 73.1 .16 6o)
9/5 9/5 (K-2 (K-273 73.1 .16 6o)+32o
C+273.16o
1
4/5 o C
9/5 o C+32o
o
5/4 o R+273.16o
5/4 o R
1
9/4 o R+32o
o
5/9 (oF-32o)+ 273.16o
5/9 (oF-32o)
4/9 (oF -32o)
1
Kelvin
K
Celsius
o
Reaumur ´ Fahrenheit
C
R F
o
Beis Beispi piel el::
Umre Umrech chnu nung ng von von
Examp Example: le:
Conver Conversio sion n from from
o
R in o C : o C = 4/5 o R
Die Grundeinheit der Temperatur Temperatur ist Kelvin (K). The fundamental temperature temperature unit is the Kelvin (K). Als Formelzeichen Formelzeichen wird T verwandt. The symbol used is the T. Die ebenfalls benutzte absolute Temperatur degree (Grad) Rankin errechnet sich zu The likewise used Rankine temperature scale for absolute temperatures is related to K as follows:
100
o
Rank = 9/5 K.
2 en - (0)
APPENDIX
Hardness - strength comparisen Vickershardness HV kp/mm2
Brinellhardness HB kp/mm2
Tensilestrength
80 85 90 95 100
80 85 90 95 100
270 290 310 320 340
105 110 115 120 125
105 110 115 120 125
130 135 140 145 150
Vickershardness HV kp/mm2
Brinellhardness HB kp/mm2
Tensilestrength
36.4 42.4 47.4 52.0 56.4
360 370 380 390 400
359 368 376 385 392
1210 1240 1270 1290 1330
37.0 38.0 38.9 39.8 40.7
360 380 390 410 430
60.0 63.4 66.4 69.4 72.0
410 420 430 440 450
400 408 415 423 430
1360 1390 1410 1440 1470
41.5 42.4 43.2 44.0 44.8
130 135 140 145 150
440 460 480 490 500
74.4 76.4 78.4 80.4 82.2
460 470 480 490 500
45.5 46.3 47.0 47.7 48.3
155 160 165 170 175
155 160 165 170 175
520 540 550 570 590
83.8 85.4 86.8 88.2 89.6
510 520 530 540 550
49.0 49.6 50.3 50.9 51.5
180 185 190 195 200
180 185 190 195 200
610 620 640 660 680
90.8 91.8 93.0 94.0 95.0
560 570 580 590 600
52.1 52.7 53.3 53.8 54.5
205 210 215 220 225
205 210 215 220 225
690 710 730 750 760
95.8 96.6 97.6 98.2 99.0
610 620 630 640 650
54.9 55.4 55.9 56.4 56.9
230 235 240 245 250
230 235 240 245 250
770 790 810 830 840
19.2 20.2 21.2 22.1 23.0
660 670 680 690 700
57.4 57.9 58.4 58.9 59.3
255 260 265 270 275
255 260 265 270 275
850 870 880 900 920
23.8 24.6 25.4 26.2 26.9
720 740 760 780 800
60.2 61.1 61.9 62.7 63.5
280 285 290 295 300
280 285 290 295 300 30
940 960 980 990 1010
27.6 28.3 29.0 29.6 30.3
820 840 860 880 900
64.3 65.0 65.7 66.3 66.9
310 320 330 340 350
31 3 10 320 32 330 340 350
1050 1080 1120 1150 1180
31.5 32.7 33.8 34.9 36.0
920 940
67.5 68.0
2 en - (0)
Rockwellhardness H R B HR C
N/mm2
Rockwellhardness HRB HRC
N/mm2
Page 101 Page 101
NOTES
102
2 en - (0)
