Welding of Dissimilar Joints The subject of welding technology is both extensive and complex if one takes into consideration all the mixed metal welds possible between the most varied types of steels. It is practically impossible to cover every individual combination of materials. This is undoubtedly one of the main reasons why there are hardly any appropriate standards and codes for dissimilar metal welds. As a result of the situation described the enquiries received in practice by the customer service department for welding technology are very often related to the problems surrounding mixed metal welds. As a consequence of this, basic general rules were drawn up in the form of rough guidelines which contain notes, recommendations and precautions for the selection of filler metals and the compilation of a welding technology. However, basic rules such as these can only be considered valuable if they can be translated into practice with adequate expertise and a basic knowledge of metallurgy. Generally speaking it should be noted that in many cases when joining different materials it is not possible to select the best possible filler metals and welding conditions for each individual partner material. It is therefore necessary to find suitable compromises. Selection of the filler metal must be considered as an essential criterion in the fabrication of mixed metal welds. This selection must be made so that where possible the weld metal arising should not be too hard, brittle and susceptible to cracks allowing for dilution with the different materials. In very simple terms, no new and thus indefinable accidental alloy that might consequently require additional considerations may come into being when the weld metal melts on the component. The weld metal properties which exist in the pure weld metal must be retained in principle despite dilution with the different base metals. The following section highlights in very broad outlines guidelines for the selection of filler metals and suitable welding technology when fabricating mixed metal welds. In this case the structure is only rough since it only deals with groups of materials with examples of type of steels.
Basic Rules for the Selection of Filler Metals for Dissimilar Welds
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General basic rules can only be considered valuable if they can be translated into practice with adequate expertise and a basic knowledge of metallurgy. The large selection of differently alloyed steels within the individual alloy groups and the mixed metal welds possible between steels from different alloy groups make it practically impossible to consider every individual combination of materials in the following section. For this reason it is only possible to specify filler metals for the various material combinations in the form of a rough structure, i.e. only by narrowing down to types steel or groups of steel. The drawback to this method is a certain degree of inaccuracy as it is not possible to take account in each case of different influencing factors that are important in the selection of suitable filler metals. Therefore the recommendation of a filler metal does not claim to be exhaustive. In case of doubt it is recommended that you consult the manufacturer. Recommendations are available for the following material combinations: combinations: Mild Steel – Mild Steel Mild Steel – High Temperature Steel Mild Steel – High Strength Steel Mild Steel – Cryogenic Steel Mild Steel – Tempering Steel Mild Steel – Chromium Steel Mild Steel – Austenitic Steel High Strength Steel – High Strength Steel High Strength Steel – Austenitic Steel Cryogenic Steel – Cryogenic Steel Cryogenic Steel – Austenitic Steel Tempering Steel – Tempering Steel Tempering Steel – Austenitic Steel Austenitic Steel – Austenitic Steel
Austenitic Steel – Chromium Steel Austenitic Steel – Heat Resistant Steel Nickel Base Alloy – Nickel Base Alloy Nickel Base Alloy – Mild Steel /High Temperature Steel / High Strength Steel /Cryogenic Steel / Tempering Steel Nickel Base Alloy – Chromium Steel / Austenitic Steel / Heat Resistant Steel Manganese Steel – Mild Steel Manganese Steel – Austenitic Steel Grey Cast Iron – Mild Steel Grey Cast Iron – Austenitic Steel High Temperature Steel – Austenitic Steel High Temperature Steel – High Temperature Steel
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Mild Steel – Mild Steel
(e.g. S235JR with S355J2G3) In practice non-alloy steels of different strengths are joined relatively often. Essentially, in the case of mixed metal welds such as these, only the mechanical property data of the base metals are in the forefront of considerations. Normally filler metals that correspond to the strength properties of the softer base metal are used. However, it should be noted in this case that non-alloy weld metal deposits barely fall below yield point values of 400 N/mm 2 and tensile strength values of 500 N/mm 2 due to the finegrain microstructure. microstructure. Naturally the choice of coating, flux and powder type must be made depending on the welding procedure to be used allowing for the wall thickness and component stiffness. With increased stiffness and application of stress to a component it is advisable to use basic filler metals and consumables whose metallurgically pure weld metal together with low hydrogen contents ensures high resistance to cracking. Mild St eel – High Temp eratu re Steel
(e.g. P235G1TH with 13CrMo4-5) Depending on the material combination, non-alloy filler metals or high-temperature high-temperature resistant filler metals should be used whereby the latter have a lower alloy content than the high-temperature resistant material of the combination. combination. With a few exceptions high-temperature resistant steels are air-hardening and therefore require special heat input during welding or subsequent postweld heat treatment. The recommendation regarding this contained in VdTÜV code of practice 451-82/1 should be taken into consideration. Mild Steel – High Stren gth Steel
(e.g. S235JR with S460N) The filler metal is usually matched to the softer base metal. In the case of great discrepancies between the strength properties of the two materials (e.g. S235JR with S690Q) a filler metal whose strength is between the values of the two base metals should be considered. Mild St eel – Cry og enic S teel
(e.g. S235JR with 14Ni6) If a cryogenic steel exhibits up to 3.5 % Ni, it is possible to use both non-alloy filler metals and filler metals of the same or similar composition to the base. With Ni contents between 5 and 9 % austenitic or nickel-based filler metals should be used. If one of the materials is an austenitic Cr-Ni steel then mainly fully austenitic filler metals of similar composition to the base should be used. Mild Steel – Temp erin g Steel
(e.g. S235JR with 42CrMo4) Tempering steels have only limited weldability, and types with a higher C content should not be used in c o d . welded structures. They require special heat input during welding and postweld heat treatment. s t n Depending on the material combination, non-alloy or low-alloy filler metals should be considered the i o J r weld metal of which undergoes an increase in strength due to carburisation from the base metal. a l i m In exceptional cases where postweld heat treatment is not possible, it may be beneficial to use austenitic i s s i Cr-Ni filler metals. D t a M . H b m G a i r t s u A k i n h c e t ß i e w h c S r e l h ö B ©
Mild Steel – Chro miu m Steel
(e.g. S235JR with X12Cr13) Both ferritic and martensitic Cr steels require special heat input during welding and subsequent annealing. As a result the use of nickel-based alloys should be considered (depending on the conditions of use). Austenitic over-alloy filler metals may also be used if subsequent annealing is not possible and the temperature during use is limited to max. 300°C. Mild Steel – Au stenitic Steel
(e.g. S235JR with X4CrNi18-10) X4CrNi18-10)
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When joining steels with very different chemical compositions there is a complex metallurgical problem which it appears can essentially only be solved by compromise. Over-alloy austenitic filler metals should be used. The most crucial criterion of mixed-metal joints such as these is the choice of filler metal. It must be made allowing for dilution with the different base metals so that the weld metal produced is neither martensitic nor fully austenitic. However, the latter is unavoidable when using nickel-based filler metals. In very simple terms no new and therefore indefinable random alloy may arise on fusing the weld metal to the component that would of necessity give rise to additional considerations being taken into account. The weld metal properties as are present in the pure weld metal deposit must be retained in spite of dilution with the base metal. The main function of filler metals is to enable fabrication of a crack- free and ductile weld between the ferritic constructional steel and the austenitic material. The Schaeffler diagram serves as the most important aid in the selection of filler metals. For the purposes of weld metal properties care should be taken to keep dilution as low as possible. The use of nickel-based filler metals is necessary in the case of postweld heat treatments or operating temperatures above 300°C otherwise embrittlement or carbon diffusion must be reckoned with. High St rengt h Steel – High Strength Steel
(e.g. S355N with S460N) In the case of mixed-metal welds between normalised and annealed high-tensile fine-grained constructional steels one should again orient oneself to the softer steel grade with regard to strength when choosing the filler metal. In the case of partner materials with very different strength properties (e.g. S355N with S690Q) consideration should be given to a filler metal whose strength lies between the two base metals. Otherwise a high jump in strength directly in the weld area could represent an additional weak spot in the component depending on the stress conditions in practical use. Special requirements, requirements, e.g. with regard to low-temperature ductility, must also be taken into account when choosing the filler metal. Due to the huge number of steel grades in existence it is barely possible to provide a concrete assignment of filler metals allowing for all the material combinations possible. Furthermore, this method of proceeding would severely compromise clarity. High St rengt h Steel – Au stenitic Steel
(e.g. S460N with X4CrNi18-10) X4CrNi18-10) Over-alloy austenitic filler metals should be used. Nickel-based filler metals should be used in the case of operating temperatures over 300°C and postweld annealing. Cryo genic Steel – Cryog enic Steel
(e.g. S225NL with 14Ni6) Filler metals must be specified allowing for the required level of low-temperature ductility. Normally for mixed-metal joints with steels up to 3.5 % Ni a filler metal that corresponds to one of the two partner c o d . metals is adequate. s t n i (possibly also nickel-based) filler filler metals should be considered considered for nickel contents contents of 5 and 9 % o Austenitic (possibly J r respectively. a l i m Material combinations with austenitic Cr-Ni steels are joined using fully austenitic filler metals with a i s s i similar alloy composition to the base or nickel-based filler metals. D t a M . H b m G a i r t s u A k i n h c e t ß i e w h c S r e l h ö B ©
Cryo genic Steel – Au stenitic Steel
(e.g. 14Ni6 with X4CrNi18-10) Filler metals must be specified allowing for the required level of low-temperature ductility. Consideration Consideration should be given to predominantly predominantly over-alloy fully austenitic filler metals. Temperin g Steel – Temperin g Steel
(e.g. 25CrMo4 with 42CrMo4) Tempering steels are only weldable to a limited extent; weldability deteriorates as the C content or alloy content increases. They require special heat input during welding as well as postweld annealing. There are hardly any filler metals with the same alloy composition as the base. Selection is made according to the specified strength properties taking into account the heat treatment necessary. In many cases the This document is subject to change without notice – page 3 of 7 - For updates see www.boehler-welding.com.
practical conditions of use allow the employment of softer filler metals as a result of which it is mainly nickel-based types that are used. The use of austenitic Cr-Ni filler metals may only be taken into consideration on condition that it is not possible to perform postweld heat treatment. Temperin g Steel – Au stenitic Steel
(e.g. 42CrMo4 with X4CrNi18-10) X4CrNi18-10) Limited weldability and necessary postweld heat treatment require the use of nickel-based filler metals, with the result that the procedure of cladding the edges, annealing and only welding thereafter is to be preferred where possible. Austenitic over-alloy filler filler metals may also be used but only where it is not possible to perform annealing and in this case an operating temperature of max. 300°C may not be exceeded. Au steni tic Steel – Au stenitic Steel
(e.g. X4CrNi18-10 with X6CrNiMoTi17-12-2) It is recommended that the filler metal be chosen in line with the chemical composition of the partner material with the higher alloy. Au stenitic Steel – Chro miu m Steel
(e.g. X4CrNi18-10 with X12Cr13) Only use over-alloy austenitic filler metals under certain conditions. Both ferritic and martensitic Cr steels have only limited weldability. They require special heat input during welding and postweld heat treatment. The specification of austenitic filler metals must therefore be made allowing for their tendency towards embrittlement and in certain cases may necessitate the use of nickel-based filler metals. Annealing treatments treatments may also adversely adversely affect the properties of austenitic austenitic steels. The weld weld edges of the chrome steel should therefore be clad with two layers and then annealed; the joint should only be welded thereafter. Au stenitic Steel – Heat Resistant Steel
(e.g. X4CrNi18-10 with X12CrNi25-21) X12CrNi25-21) Mainly filler metals that correspond in respect of the alloy to the high-temperature resistant partner material should be used. Nickel B ase Allo y – Nickel B ase Allo y
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(e.g. Alloy C 625 with Alloy C 22) Each combination of materials must be considered separately separately with regard to the choice of filler metal. The filler metal should correspond in respect of the alloy to the partner material with the better ductility properties. For higher corrosion stress conditions the filler metal should be matched to the higher Moalloy base metal or should be over-alloy welded if necessary. Nickel B ase Allo y – Mild Steel /High Temp erature Steel / High Str ength Steel /Cryo /Cryo genic Steel / Te m p er i n g S t ee l
(e.g. C 276 with S235JR /13CrMo4-5 /S460N /14Ni6 /42CrMo4) There is a whole series of nickel-based filler metals with different alloys available for mixed-metal joints such as those referred to above. In many cases a filler metal of the same or similar composition to the nickel-based parent metal is used. Nickel B ase Allo y – Chro miu m Steel / Aus tenitic Steel / Heat Heat Resistant Steel
(e.g. C 276 with X12Cr13 /X4CrNi18-10 /X12CrNi25-21) The conditions of use should be taken into consideration when choosing the filler metal. Normally a filler metal corresponding to or of similar composition to the nickel-based alloy is used. Mang anes e Steel – Mild Steel
(e.g. X120Mn12 with S235JR) The use of austenitic Cr-Ni filler metals with increased Mn content or over-alloy types is recommended. Mangan ese Steel – Au stenitic Steel
(e.g. X120Mn12 with X4CrNi18-10) X4CrNi18-10) This document is subject to change without notice – page 4 of 7 - For updates see www.boehler-welding.com.
Austenitic filler metals metals with increased increased Mn content or over-alloy over-alloy types are recommended. recommended. Grey Cas t Iron – Mild Steel
(e.g. GGG-40 with S235JR) Only cold cast iron welding may be taken into consideration. The filler metals are of different composition to the base metal and are Ni-Fe-based. Grey Cast Iron – Au stenitic Steel
(e.g. GGG-40 with X4CrNi18-10) Only cold cast iron welding may be employed. Either Ni-Fe-based types or Cr-Ni-based types with increased Mn content are used. High Temperatu re Steel – Au stenitic Steel
(e.g. 13CrMo4-5 with X4CrNi18-10) Only use over-alloy austenitic filler metals under certain conditions. Nickel-based filler metals should be used in the case of operating temperatures over 300°C and postweld annealing. With the exception of the non-alloy grades and 16Mo3, high-temperature steels are air-hardening. In certain cases this necessitates postweld annealing in addition to suitable heat input during welding and therefore the use of nickel-based nickel-based filler metals. Annealing treatments may adversely affect the properties of austenitic steels. Therefore, where possible the welding edges of the high-temperature material should be clad and subsequently annealed; only then should the joint be welded. High Temperatu re Steel – High Temperatu re Steel
(e.g. 13CrMo4-5 with 11CrMo9-10) Each combination of materials must be considered separately with regard to choice of filler metal and heat treatment. Generally speaking a filler metal corresponding to the partner material with the lower alloy is chosen. Unless there is an overlapping annealing range, the postweld heat treatment represents a compromise between the optimum annealing temperatures of the materials concerned. The recommendations contained in VdTÜV Code of Practice 451-82/1 must be taken into account. Recommendations for suitable filler metals and optimum heat treatment Base Material Combination
c o d . s t n i o J r a l i m i s s i D t a M . H b m G a i r t s u A k i n h c e t ß i e w h c S r e l h ö B ©
)
Filler Metals
Stick Electrodes FOX SPEM FOX EV 47 FOX EV 50 FOX DMO Kb or Ti
P235G1TH P255G1TH
16Mo3
P295GH
16Mo3
FOX EV 47 FOX EV 50 FOX DMO Kb or Ti
P310GH
16Mo3
FOX DMO Kb or Ti
P235G1TH P255G1TH
13CrMo4-5
FOX EV 47 FOX EV 50 FOX DMO Kb or Ti
16Mo3
13CrMo4-5
FOX DMO Kb or Ti
16Mo3
10CrMo9-10
FOX DMO Kb or Ti
13CrMo4-5
10CrMo9-10
FOX DCMS Kb
14MoV6-3
13CrMo4-5
FOX DCMS Kb
annealing 2) temp.
GTAW/GMAW GTAW/GMAW EML 5 EMK 6 EMK 7 – EMK 8 DMO-IG DMO Kb-FD, DMO Ti-FD EML 5 EMK 6 EMK 7 - EMK 8 DMO-IG DMO Kb-FD, DMO Ti-FD EML 5 EMK 6 EMK 7 – EMK 8 DMO-IG DMO Kb-FD, DMO Ti-FD EML 5 EMK 6 EMK 7 – EMK 8 DMO-IG DMO Kb-FD, DMO Ti-FD DMO-IG DMO Kb-FD, DMO Ti-FD DMO-IG DMO Kb-FD, DMO Ti-FD DCMS-IG DCMS Kb-FD DCMS-IG
SAW EMS 2 EMS 3 EMS 2 Mo
°C 530-600
EMS 2 EMS 3
530-580
EMS 3 EMS 2 Mo
530-580
540-600
EMS 2 Mo
550-620
EMS 2 Mo
570-620
(EMS 2 CrMo)
650-720
EMS 2 CrMo
680-720
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Base Material Combination
)
Filler Metals
Stick Electrodes 14MoV6-3
10CrMo9-10
FOX CM 2 Kb
14MoV6-3
X20CrMoV12-1
10CrMo9-10
X20CrMoV12-1
FOX DMV 83 Kb FOX 20 MVW FOX CM 2 Kb or FOX NIBAS 70/20 or FOX NiCr 70 Nb FOX DMV 83 Kb FOX 20 MVW FOX DMO Kb or Ti
17 MnMoV 74 15 NiCuMoNb 5 11 NiMoV 53
20MnMoNi4-5
P235G1TH P255G1TH 16Mo3 13CrMo4-5 P235G1TH P255G1TH 16Mo3 13CrMo4-5 P235G1TH P255G1TH 16Mo3 13CrMo4-5
22 NiMoCr 37
GP240GH
22Mo4
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°C 690-730 670-720 700-750 680-730 700-750 530-590
DMO-IG DMO Kb-FD, DMO Ti-FD
EMS 2 Mo
530-590
FOX DMO Kb or Ti
DMO-IG DMO Kb-FD, DMO Ti-FD
EMS 2 Mo
550-600
FOX DMO Kb or Ti
DMO-IG EMS 2 Mo DMO Kb-FD, DMO Ti-FD DCMS-IG EMS 2 CrMo DCMS Kb-FD DMO-IG EMS 2 Mo DMO Kb-FD, DMO Ti-FD
530-590 530-59 0
P235G1TH P255G1TH 16Mo3 13CrMo4-5 P235G1TH P255G1TH 16Mo3 13CrMo4-5 P235G1TH P255G1TH
FOX DMO Kb or Ti
FOX DMO Kb or Ti
DMO-IG DMO Kb-FD, DMO Ti-FD
EMS 2 Mo
580-640
FOX EV 47 or FOX EV 50
EMS 2 EMS 3
560-620
16Mo3
FOX DMO Kb or Ti
EMS 2 Mo
560-620 560-62 0
16Mo3
FOX DMO Kb or Ti
EMS 2 Mo
560-620
13CrMo4-5
EML 5 EMK 6 EMK 7 DMO-IG DMO Kb-FD, DMO Ti-FD DMO-IG DMO Kb-FD, DMO Ti-FD DMO-IG DCMS-IG DCMS-IG DCMS Kb-FD DMO-IG DMO Kb-FD, DMO Ti-FD DCMS-IG DCMS Kb-FD
EMS 2 Mo EMS 2 CrMo EMS 2 CrMo
560-620 560-62 0
EMS 2 Mo
640-700 640-70 0
EMS 2 CrMo
640-700 640-70 0
EMS 2 CrMo
670-720 650-730
CM 2-UP
670-720
(CM 2-UP)
680-730
22Mo4
21 CrMoV 511
FOX DMO Kb or Ti FOX DCMS Kb FOX DCMS Kb
G17CrMo5-5
16Mo3
FOX DMO Kb FOX DCMS Kb
G17CrMoV5-11
13CrMo4-5 10CrMo9-10 14MoV6-3 13CrMo4-5 10CrMo9-10
FOX CM 2 Kb
14MoV6-3
FOX DMV 83 Kb FOX CM 2 Kb
21CrMoV5-1-1 X8CrNiNb16-13
FOX DMV 83 Kb FOX NIBAS 70/20 FOX NiCr 70 Nb FOX DMV 83 Kb FOX 20 MVW FOX NiCr 70 Nb FOX NIBAS 70/20 FOX CM 2-IG FOX NIBAS 70/20 FOX NiCr 70 Nb
X20CrMoV12-1
GX22CrMoV12-1
GTAW/GMAW GTAW/GMAW SAW DCMS Kb-FD CM 2-IG (CM 2-UP) CM 2 Kb-FD DMV 83-IG 20 MVW-IG CM 2-IG or (CM 2-UP) NIBAS 70/20-IG or NiCr 70 Nb-IG DMV 83-IG 20 MVW-IG 20 MVW-UP DMO-IG EMS 2 Mo DMO Kb-FD, DMO Ti-FD
FOX DMO Kb or Ti
FOX DCMS Kb 15 MnMoNiV 53
annealing 2) temp.
14MoV6-3 14MoV6-3
FOX DCMS Kb
DCMS-IG DCMS Kb-FD CM 2-IG CM 2 Kb-FD DMV 83-IG CM 2-IG CM 2 Kb-FD DMV 83-IG NIBAS 70/20-IG NiCr 70 Nb-IG DMV 83-IG 20 MVW-IG NiCr 70 Nb-IG NIBAS 70/20-IG DMV 83-IG NIBAS 70/20-IG NiCr 70 Nb-IG
530-590
650-720
670-730
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Base Material Combination
)
Filler Metals
annealing 2) temp.
Stick Electrodes GTAW/GMAW GTAW/GMAW SAW °C FOX DMV 83 Kb DMV 83-IG 680-730 FOX NIBAS 70/20 NIBAS 70/20-IG FOX NiCr 70 Nb NiCr 70 Nb-IG 21CrMoV5-1-1 FOX DMV 83 Kb 20 MVW-IG 670-730 FOX NIBAS 70/20 NIBAS 70/20-IG FOX NiCr 70 Nb NiCr 70 Nb-IG X20CrMoV12-1 X20CrMoV12 -1 FOX 20 MVW FOX NIBAS 70/20 NIBAS 70/20-IG FOX NiCr 70 Nb NiCr 70 Nb-IG X8CrNiNb16-13 FOX NiCr 70 Nb NiCr 70 Nb-IG FOX NIBAS 70/20 NIBAS 70/20-IG Use subject with reservations. Before selection please consult your next BÖHLER representative and give exact description of service conditions and requirements. The material recommendations have been chosen in a way to ensure that the relevant filler metal is lower alloyed and thus tougher than the base metal. The annealing temperatures have been chosen in a way to ensure that the lowest Ac1 temperature of the two materials involved is not exceeded. The annealing time depends on the relevant work piece thickness; it has to be at least 15 minutes for thicknesses of 15 mm, at least 30 minutes for thicknesses of 15-20 mm and at least 60 minutes for thicknesses above 30 mm. For work pieces of low thicknesses a medium annealing ti me should be chosen, whereas in thick-walled components the surface should be reach a temperature within the upper range. 14MoV6-3
() 1) 2)
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