Journal of the Brazilian Society of Mechanical Sciences Print ISSN 0100-7386
J. Braz. Soc. Mech. Sci. vol.22 vol.22 n.3 Campinas 2000 doi 10!1"#0$S0100-7386%00000030000%
A Quality and Cost Approach for Welding Process Selection César Rezende Silva Valtair Antonio Ferraresi Américo Scotti &aculdade de 'n(enharia Mec)nica! *ni+ersidade &ederal &ederal de *,erl)ndia! !P! !P! "#3! 38.00-#0%! *,erl)ndia! M/ ascottiecanica!ufu!,r
The aim of this work was to propose, apply and evaluate a methodical approach to select welding processes in a productive environment based on market requirements of Quality and Costs. A case study was used. The welds were carried out in laboratory, simulating the joint conditions of a manufacturer and using several welding processes !"A#, $TA#, pulsed $TA#, $"A# with C% & and Ar based shielding gases and pulsed $"A#. 'or Quality analysis geometrical aspects of the beads were considered and for Cost analysis, welding parameters and consumable prices. Quantitative indices were proposed and evaluated. After that, evaluation of both Quality and Costs was done, showing to be possible to select the most suitable welding process to a specific application, taking into account the market conditions
of a company. Keywords: Quality, costs, cost sensibility, process selection, welding
Introduction 2he rise of coetition has led any coanies to ay ore attention in their ar4ets in order to attend the roerly! 2he first ste is to 4no5 5ell the ar4et in 5hich the coany stands deterinin( ar4et reuireents 5hat and ho5 uch9 in ters of rice uality roduct di+ersity deli+ery confidence etc! Besides it is necessary to choose the ost suita,le fa,rication rocess to a secific situation aon( the 5eldin( considerin( technical and econoical +ia,ility! 2he e:istence of a (reat nu,er of 5eldin( rocesses in the ar4et 5ith their +ariances alternatin( direct and ulsed currents etc!9 a4es the ,est rocess choice for a secific situation difficult! ;ence an e+aluation ethod that hels this tas4 is +ery iortant to the final results of any coany ar4et strate(y! < corehensi+e and recise analysis to select correctly a 5eldin( rocess in real situations is +ery hard and cole: ,ecause of any +aria,les in+ol+ed!
<> is the ,est in =uality and the rocess >B> is the ,est in osts! 2here are iniu reuireents of =uality and osts that need to ,e deterined and reached for each case in order to ,e coetiti+e! 2hese reuireents deend ainly on the i: ,et5een roduct and ar4et of the coany! In fact the ,est rocess 5ill ,e that one that resents the ,est o+erall erforance! ?ne can say that the 5eldin( =uality is related to the ,ead and the heat affected zone ;<@9 characteristics
enclosin( resence of defects surface finishin( satterin( crac4in( orosity de(ree of enetration e:cessi+e reinforceent etc!9 echanical rorieties stren(th tou(hness hardness etc!9 and cheical coosition! =uality is a relati+e roerty! 2o descri,e =uality in a uantitati+e 5ay is a hard tas4! < (ood or ,ad =uality is a function of the reuireents for a articular alication! Aeldin( osts see at first (lance to ,e a ore easura,le roerty! ;o5e+er they in+ol+e a (reat nu,er of coonents such as 5eldin( e:ecution rocess selection ersonnel trainin( oint desi(n euient definition$settin( and e+en fa,rication siulation! 2he deterination of 5eldin( osts reuires to consider 5eldin( araeters and rices of consua,les la,or euient etc!! ?ne ust (i+e close attention to the rele+ant coonents of osts durin( the deterination and control$reduction of the! Siilarly to =uality a tar(et for lo5 osts deends on the articular alication! '+en considerin( the secificity of each coany and its 5elded roducts ost analysis ,ased on a (i+en 5eldin( condition is relati+ely achie+a,le! 2here are inclusi+ely soft5ares for this urose! ;o5e+er the introduction of the =uality concet in an o+erall analysis ,rin(s a ne5 challen(e$ersecti+e to 5eldin( rocess selection aroaches! 2herefore in this 5or4 a ne5 aroach of =uality and osts o+erall analysis is roosed accordin( to ar4et reuireents to select the ,est 5eldin( rocess for a coany that 5ishes either to chan(e or to introduce ne5 fa,rication rocesses!
Ceterination of Aeldin( =uality
e:ressed as uantitati+e indices as follo5in( 5hose terinolo(y is ,ased on 5eldin( reresentati+e literature
5here p is the 5eld enetration K t is the oint thic4ness K r is the ,ead reinforceent K w is the ,ead 5idth K ! is the satterin( rate 4($hK is the deosition rate 4($hK ' elect is the co+ered electrode fusion rate 4($hK "iel is the initial ass of the co+ered electrode ,efore 5eldin( (K "fel is the final ass of the co+ered electrode after
5eldin( (K t arc is the arc duration tie sK ' wire is the 5ire fusion rate 4($hK φ is the 5ire diaeter K f wire is the 5ire feed rate $inK γ is the steel density 7!8" : 10-3 ($39 " fcp is the final ass of the test late after 5eldin( (K " icp is the initial ass of the test late ,efore 5eldin( (K and de is the deosition efficiency FK! 2a,le 1 resents the =uality criteria adoted for the 5eldin( assessent!
Ceterination of Aeldin( osts 2here are any o,ecti+es to ha+e 5eldin( osts calculated!
used for ,ud(et ela,oration and$or for coarison and selection of 5eldin( rocesses! Machado 1##"9 states that osts deterination can ,e used for coosin( sale rice helin( ta4e decisions a,out a roduct fa,rication oortunity deterinin( the necessary in+estent +olue for an oeration redictin( odifications o5in( to fa,rication scale chan(es esta,lishin( the rinciles to ileent a cuttin( ost ro(ra and ro+idin( assistance to a 5eldin( rocess selection! In the resent case osts 5ill ,e used as a ,alancin( araeter durin( selection of the ost suita,le 5eldin( rocess! 2he osts can ,e ,ased on estiate +alues estiations of aount of 5eld to ,e deosited9 or on actual +alues aount in fact reached in e:eriental tests9! In this 5or4 the actual deosited aount 5as used! 2he reason for that is that the used oint a ,utt 5eld oint 5ith no (roo+e and (a a4es difficult to estiate the aount of 5eld to ,e deosited! It is iortant to oint out that e+en in case of (roo+ed oints each rocess ay deosit different hei(ht of reinforceents isconductin( calculations! 2herefore to aly the aroach for rocess selection 5eldents of test lates ,ecae necessary siulatin( real cases! 2he coosition of osts ta4es into account aterials electricity la,or and euient! Indirect osts 5ill not ,e considered since they are aro:iately the sae in ters of coarison! 2hus T#C - "C 9 :C 9 ;C 9 ;)C #9
5here T#C is the 2otal Aeldin( osts "C is the Material ost :C is the a,or ost ;C is the 'uient ost and ;)C is the 'lectrical Po5er ost!
2he roosed atheatics euations to the deterination of each ter of the 2otal osts T#C 9 are resented in 2a,le % for all 5eldin( rocesses under e+aluation 5here de reresents the deosition efficiency that is the rate ,et5een the 5eld ass deosited and the elted ass of the consua,leD fop indicates the oeratin( factor or duty factor9 that is the rate ,et5een the runnin( arc duration tie and the total 5eldin( tieD ee is the electrical efficiency of the euient that is a factor relatin( inut and outut o5er and o5er factor and )m is the onthly roduction of 5eld (i+en ,y the nu,er of hours 5or4ed in a onth 176 h9 ultilied ,y the oeratin( factor fop9 and ,y the deosition rate 9! &or the deosition rate 9 and the deosition efficiency de9 deterinations 's!6 and 8 5ere used resecti+ely!
':eriental Procedure 2o e+aluate the roosed aroach a case study 5as ta4en! In this case dred(in( ies are anufactured ,y ,utt 5eldin( %--thic4 lain car,on steels! 2herefore 5eldin( test lates 5ere reared usin( sheets of lain car,on steel
diensions of %"0 : "0 : % ! &or oint confi(uration a tyical oint alied ,y the anufacturer of dred(in( ies 5as used ,utt oint 5ith no root oenin( 5eldin( on the flat osition denoinated ,y the <erican Aeldin( Society
/as 2un(sten
?% shielded /as Metal
Pulsed /as 2un(sten
Pulsed /as Metal
&or the =uality analysis +isual insection of the ,eads 5ere alied alon( all their e:tensions aiin( to find defects such as crac4s orosities and undercuts! In addition the (eoetric araeters 5 and r9 of t5o trans+erse sections of each ,ead 5ere easured ,y a couterized ia(e analysis syste! &or that the seciens 5ere cut off fro the test lates (round and cheically etched 5ith an iodine-,ased rea(ent! &or the ost ter calculations current +olta(e 5eldin( seed 5ire feed seed and (as flo5 5ere set and$or onitored! Aeldin( ties and initial and final ass of the test lates 5ere also easured ,y chronoeter and a di(ital scale9!
esults and Ciscussion 2a,le 3 sho5s the set$onitored 5eldin( araeters of each rocess! It is iortant to oint out that these +alues re(ard acceta,le conditions yet not otiized araeter otiization 5as not in the scoe of this 5or49! Aith the data fro 2a,le 3 and 's!.9 "9 69 79 and 89 the &elect &wire ! and de +alues 5ere calculated and are resented on 2a,le .!
=uality
If a araeter selection otiization of each rocess is not considered otiized araeters could lead to different results9 and one concentrates only on the o,ecti+es of the 5or4 the follo5in( o,ser+ations can ,e e:tracted fro 2a,le " 2he SM
2he /2
2he P/M
2he /M
&i(ure 1 sho5s the ,ead trans+erse sections roduced ,y the /M
ost
shieldin( in 5hich these t5o coonents 5ere resonsi,le for ore than 80F of the osts e:cet for the P/2
2hen a +isual analysis of the lots is eloyed to assess the si(nificance of the factor +ariations sensiti+ity9! 2he ore si(nificant the factor the ore attention is needed in order to (et a cost otiization i!e! si(nificant reduction of 2otal Aeldin( osts! &i(ure 3 sho5s the analyses of sensiti+ity for the /M
Process Selection Based on =uality and osts 2he aroach roosed in this 5or4 for 5eldin( rocess selection uses a ,alance ,et5een =uality and ost! <lyin( this aroach to find the ost suita,le 5eldin( rocess for the (i+en roduct the results ha+e sho5n that considerin( =uality only ,oth /M
In relation to osts the /M
onclusions &ro the roosed aroach and systeatics resented for the 5eldin( rocess selection ,ased on the ,est (lo,al erforance of =uality and ost analyses in this case alied to 5eld thin sheets of car,on steel9 it is ossi,le to conclude that 2he selection of the ,est 5eldin( rocess is ossi,le to a certain industrial acti+ity considerin( the ,est (lo,al erforance of =uality and osts accordin( to ar4et reuireents of the coany! 2he rocedure utilized in this 5or4 sho5ed to ,e a suita,le tool to this aiD
2he authors 5ish to than4 C
eferences Aeldin( ;and,oo4 - Qol!1 Aeldin( 2echnolo(y> 8th 'd! /uide for the Qisual Insection of Aelds> ustos nos rocessos de solda(e> In Aainer '! Brandi S!C! R de Mello &!C!;! Solda(e rocessos e etalur(ia 'd(ard Blucher Brazil cha!11 !..#-.61! in4s K IIA$IIS 1#8. >/eoetrical Cefects in Aeldin( in the Aorld Qol!%% No!1$ % !3."%! in4s K IS? "817 1##%!>! in4s K Machado I!/! 1##" >< 'conoia da Solda(e> 2he Procedure ;and,oo4 of 1%th! 'd! incoln 'lectric *S
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a,cdoain!co!,r
