Process Modeling of Short-Circuiting GMA Welding and Its Application to Arc Sensor Control

Transcription

1 UDC : Proc Modling of Shor-Circuiing GMA Wlding nd I Applicion o Arc Snor Conrol Shinji KODAMA* 1 Yuomo ICHIYAMA* 1 Yuyuki IKUNO* 2 Norimiu BABA* 2 Abrc Th mhmicl modl of g ml rc (GMA) wlding, focuing on horcircuiing rnfr, i dvlopd. Fir, modl of hor rc wlding i propod, bd on prviou rpord modl of pry rc wlding. Thn, h propod modl pplid o h high pd ocilling GMA proc, nd h hor-circuiing dynmic i invigd. Numricl clculion rul rvld h hor-circuiing rgulrly occur boh ocilling dg ocilling frqunci clo o hlf h r of hor-circuiing undr non-ocilling condiion. Th finding indic h h rc nor propri improvd by ing h ocilling frquncy o hi vlu. 1. Inroducion In g ml rc (GMA) wlding, h wlding wir ilf rv h lcrod. Sinc h lcrod wir i mld by h rc h nd rnfrrd o moln pool in h form of ho dropl, i mling chrcriic influnc h currn nd volg chrcriic in h rc wlding ym. Vriou modl for rc wlding ym hv bn dvlopd, minly o nlyz h wir-mling phnomnon. Lnwich 1) nd Hlmoy 2) drivd wir-mling chrcriic formul bd on h pry rnfr condiion undr which h mod of ho-dropl rnfr biliz. Mruo l. 3) drivd h opimum currn condiion by pplying hi o puld rc wlding. Uhio l. 4, 5) nlyzd h dynmic mling chrcriic of wir nd buil modl for h rc wlding ym king ino ccoun h powr upply rponivn (inducnc, c.) nd h chng in orch high du o i wving in h groov. Thi modl, in priculr, h bn pplid o nlyz h prformnc of rc nor nd h hlpd blih h foundion for xclln rc nor ym, uch h high pd roing rc wlding proc 6). On h ohr hnd, in GMA wlding, no only pry rnfr condiion r widly mployd, bu lo hor-circuiing rc condiion wih rlivly mll currn. Shor-circuiing rc wlding i h minrm in high-pd wlding of hin h or ovrhd poiion wlding of lin pip. Howvr, bcu of h complicd proc in which hor-circuiing nd rc gnrion r rpd inrminly, hr r fw ppr on hor-circuiing rc wlding 7). Bid, in hor-circuiing rc wlding, i i difficul o diinguih bwn h chng in wlding currn/volg du o hor-circuiing nd ho du o chng in poiionl rlionhip bwn h groov nd lcrod wir. Undr hi condiion, hr i h concrn h h ccurcy of m rcking of rc nor would dclin. Thrfor, wih h im of br undrnding h wlding phnomn, n mp w md o dvlop modl for hor rc wlding on h bi of prviou rpord modl for pry rc wlding. In ddiion, by pplying h nwly dvlopd modl, n nlyi w conducd on h hor-circui bhvior in h high-frquncy ocilling GMA proc o nbl dicuion of h guidlin on opimizion of rc nor propri. Th vribl ud for h modl r hown h nd of hi ppr. 2. Modling of Arc Wlding Sym 2.1 Spry rnfr modl Concrning h pry rnfr condiion, mny udy rul hv bn rpord. In hi ppr, rfrnc i md o h mhmicl modl 4) dvlopd by Uhio l. king ino ccoun h dynmic * 1 Sl Rrch Lborori * 2 Nippon Sl Enginring Co., Ld

2 chrcriic of wir mling. Fig. 1 how h quivln lcricl circui for ypicl GMA wlding mploying powr upply hving conn volg chrcriic, nd quion (1) hrough (9) rprn i mhmicl modl. Equion (1) nd (2) r h rlionl xprion of orch high L nd orch volg U. Thy r xprd by h um of h wir xnion componn nd rc componn. L = L + L (1) U = U + U (2) Arc volg U i xprd by h following rlionl xprion of wlding currn I nd rc lngh L. U = U 0 + R I + E L (3) Th following quion (4) xpr volg drop U h wir xnion, nd h vlu of U cn b clculd from wir rinc R during currn conducion xprd by quion (5). U = R I (4) Th vlu of R i obind n ingrd vlu long h wir lngh by uing h Joul hing wigh J z poiion Z on h wir dfind by quion (6) ( Fig. 1) nd rlionl xprion r (J ) of z J z nd rinc vlu. L R = r J z dz (5) 0 J z = I 2 τ dτ z / V f Fig. 1 Equivln lcricl circui for GMA wlding (Rf.4) (6) Equion (7) i h rlionl xprion of h quivln lcricl circui for GMA wlding. In h lf-hnd id of h quion, U, K nd L dno no-lod volg, inrnl rinc nd powr upply inducnc, rpcivly. R c I nd U in h righ-hnd id rprn powr cbl volg drop nd orch volg, rpcivly. U K I L di = R d c I + U (7) Equion (8) rprn h moun of vriion of wir xnion lngh L h i xprd h diffrnc bwn wir fding pd V f nd wir mling pd V m. A hown in quion (9), h vlu of V m i obind h funcion of wlding currn I nd Joul hing wigh J L h ip of h wir xnion 4). In quion (9), A dno h cofficin of rc hing in wir mling, nd B dno h cofficin of Joul hing. dl = V d f V m (8) V m = AI 1 BJ (9) L 2.2 Shor-circuiing rnfr modl An mp w md o dvlop hor-circuiing rc modl uing h pry rc modl. In h pry rc modl, i w umd h ho dropl would b coninuouly rnfrrd from h wir ip o h b ml mling pd V m. In h c of hor-circuiing rc, howvr, i i conidrd h ch ho dropl grow h wir ip during rc gnrion, hrby horning h rc lngh nd cuing h dropl o b rnfrrd o h b ml in h horcircuid. Thrfor, dicuion nud wih rgrd o h horcircuiing rc in wo diffrn priod h opn-rc priod nd h hor-circuiing priod hown in Fig. 2. In ddiion, inc i w ncry o conidr h ho dropl h wir ip, wir xnion lngh L w dividd ino unmld wir lngh L nd dropl lngh L m. L = L + L m (10) Equion (11) hrough (16) rprn h clculion modl for h opn-rc priod. I w umd h ll h moln ml would urn ino dropl h ip of h wir. Th moln pool profil (dprion, c.) w lf ou of conidrion. Equion (11) xpr h iniil condiion of dropl lngh. On h umpion h ch dropl would b complly rnfrrd o h b ml during h hor-circuiing priod, dropl lngh L m h inn, i, which n rc i gnrd w umd o b zro. L m i =0 (11) Th condiion for rc gnrion i givn by h following qu- Fig. 2 Schmic rprnion of hor circuiing rnfr mod

3 ion. Whn L bcom grr hn orch high L, h hor-circuiing priod bgin. L L (12) A i vidn from quion (10), L i drmind by h rliv r of chng of L nd L m. Thu, dl = dl + dl m (13) d d d L i givn by h following quion. To obin V m, quion (9) pplicbl in h opn-rc priod w dircly pplid. dl = V d f V m (14) Dropl lngh L m h wir ip w dfind by h following quion (15) nd (16). Nmly, L m w dcidd by muliplying R m, h vlu of which w obind by uming h h ip of wir hving cro-cion r S would urn ino phricl dropl hving rdiu R m whn mld mling pd V m, by conn which rprn h dropl hp. 4 3 πr 3 m = S V m τ dτ (15) i L m = α R m (16) Th dropl hp dpnd on h hilding g, wlding poiion, c. Whn n 80% Ar + 20% CO 2 hilding g, which rdily nd o cu pry rnfr, or downwrd wlding poiion i dopd, i i conidrd h h dropl will k on n longd form. In hi ppr, hrfor, i i umd h = 3 nd h h dropl lngh i 1.5 im h phricl dropl lngh umd in quion (15). Equion (17) ~ (19) rprn h clculion modl for h horcircuiing priod. Whn rc lngh L i umd o b zro, dropl lngh L m i drmind by h r of chng of h orch high, h wir fding pd nd h wir mling pd. dl m = dl V d d f + V m (17) During hor-circuiing, h wlding currn incr nd dropl ncking i nhncd. I i conidrd, hrfor, h h Joul hing of h wir xnion govrn h mling of h wir 8). Thrfor, h vlu of V m w ind during hor-circuiing whil king ino ccoun only h influnc of Joul hing hown in quion (18). V m = B 1 R I 2 (18) Dropl ncking ply n imporn pr in h hor-circuiing rnfr proc. Bcu of hi, h influnc of hor-circui currn nd dropl iz on h dropl ncking formion hv bn udid 9). On h ohr hnd, dropl lngh L m whn h orch i ocilling i influncd no only by h dropl growh (incr in dropl wigh) du o Joul hing, bu lo by h chng in orch high du o orch ocillion. I i conidrd, hrfor, h whn h orch pproch ihr of i ocillion nd, L m horn du o dcr in orch high nd ncking of h dropl i rrind. On h ohr hnd, h orch i dincd from h ocillion nd, L m incr, nhncing h dropl ncking nd horning h horcircuiing rnfr im. Thrfor, rm of promoion of hor-circuiing rnfr, h qur of wlding currn w ud nd L m hown in quion (19). I w umd h h hor-circuiing rnfr would nd whn h ingrd vlu of hir produc in h priod from h im, i, whn h hor-circuiing bgin rch h prcribd vlu. i I τ 2 L m τ dτ β (19) Th murd hor-circuiing im w pproximly 3 m. In ordr o rproduc hi hor-circuiing im, h vlu of w fixd Modl-bd Anlyi nd Dicuion on Arc Snor Prformnc Uing h hor-circuiing wlding modl dcribd bov, udy w conducd h condiion for occurrnc of hor-circuiing du o ocillion of h orch by mn of numricl nlyi pplying diffrnc clculu. Th uni im ud for h clculion w 0.5 m nd h clculion rul obind in 1 o 3 wr vlud. I h bn confirmd h h rul of clculion in 1 or mor rch ionry. Th prmr for rc chrcriic nd wir mling chrcriic wr dcidd bd on h vlu givn in rfrnc mril 4-7). A h condiion for h hor-circuiing rc, V m = 83.3 mm/, U = 22.6 V nd orch high L = 18 mm h cnr of ocillion wr ud. Avrg wlding currn nd vrg orch volg wr umd o b 190 A nd 17.9 V, rpcivly, nd hor-circuiing frquncy, N o, wihou orch ocillion w umd o b 80 im/. Fig. 3 how h clculd wlding currn nd orch volg wvform wihou ocillion of h orch. A h m im h hor-circuiing r, h volg bgin o drop hrply nd h currn bgin incring. Th currn coninu incring for h hor-circuiing priod, h i, h priod for which h condiion of quion (19) i m. Th r which h currn incr dpnd on h inducnc of h wlding powr upply. Th mllr h inducnc, h highr i h r of currn incr nd hnc, h horr bcom h hor-circuiing priod. I hould b nod h h moun of incr in volg during h hor-circuiing priod i omwh mllr hn in h cul wlding phnomnon. Thi i bcu h incr in wir rinc du o ncking formion i xcludd from conidrion. Whn h hor-circuiing priod nd, n rc occur, cuing h volg o incr hrply nd h currn o r dcring lowly. During h opn rc priod, h volg drop lowly h rc lngh dcr du o growh of h dropl. A dcribd bov, by uing h hor-circuiing wlding modl, i i poibl o rproduc h dynmic wlding phnomnon wihin Fig. 3 Simulion rul of orch volg nd wlding currn

4 h hor-circuiing priod. 3.1 Shor-circuiing dynmic in high-frquncy ocilling GMA proc Tking ino conidrion h xprimnl rul, n nlyi w conducd on h hor-circuiing dynmic undr ocillion of h orch in h groov. Fig. 4 how h rlionhip bwn ocilling orch poiion X in h groov nd orch high L. Th chng of L w dcidd bd on h umpion h h rc would prd bou 3 mm for groov wih roo gp of 5 mm. Nmly, i w umd h muul inrfrnc bwn h rc nd groov wll would occur whn X > 1.0 mm, cuing L o dcr by 1.5 mm ch ocillion nd ( X = 1.5 mm). Th ocilling orch poiion w xprd by h impl hrmonic moion of ocillion widh W nd ocillion frquncy f hown in quion (20). X = W /2 in 2π f (20) Fig. 5 how h murd nd clculd orch volg wvform orch ocillion frqunci of 10, 40 nd 50 Hz. In h digrm howing h murd wvform, iming (L, R) boh nd of h orch ocillion r indicd on h uppr horizonl xi. I cn b n h boh h murd nd clculd wvform how imilr rnd. Whn f = 10 Hz, hor-circuiing occur vrl im h im h h orch pproch ihr of i ocillion nd, bu h hor-circuiing poiion i no limid o h ocillion nd. Whn f = 40 Hz, hor-circuiing occur rgulrly ihr ocillion nd. Whn f = 50 Hz, h hor-circuiing phnomnon do no follow h orch ocillion nymor, lhough h poiion which hor-circuiing occur i limid o ihr ocillion nd. Fig. 6 how h rlionhip bwn ocillion frquncy nd h r of hor-circuiing. I cn b n h h clculion rul gr wll wih h xprimnl rul. Nmly, whn f i in h rng 30 o 45 Hz, h hor-circuiing frquncy N i wic h vlu of f. Ech im h orch ocill in h groov, h wir pproch h lf nd righ groov wll onc. I i conidrd, hrfor, h whn h ocillion frquncy nr hlf of h hor-circuiing frquncy wihou orch ocillion, h dropl i rgulrly rnfrrd h lf nd righ groov wll. Whn f < 30 Hz, h vlu of N i Fig. 4 Torch high vriion during orch ocillion in groov Fig. 6 Rlionhip bwn orch ocilling frquncy nd numbr of hor-circuiing Fig. 5 Comprion bwn xprimnl rul nd imulion rul of orch volg hiory

5 much lrgr hn wic h vlu of f. In hi c, i i conidrd h h dropl grow bfor h wir pproch ihr groov wll, cuing hor circui o occur frqunly, rgrdl of h ocilling orch poiion. Whn f i incrd o 50 Hz or mor, i bcom difficul for hor circui o occur ihr of h orch ocillion nd nd h vlu of N dcr from wic h vlu of f. Whn f i in h rng 75 o 90 Hz, h vlu of N pproch h of f. In hi c, i i conidrd h hor circui occur onc in ch ocillion cycl, h i, hor circui cn occur ihr ocillion nd. 3.2 Opimizion of ocillion frquncy for rc nor Th rc nor i chnology for m rcking conrol by ning nd fding bck h chng in h wlding currn or orch volg cud by ocillion of h orch. I h bn widly mployd undr pry rnfr condiion in which h wlding phnomnon i bl. Undr hor-circuiing condiion, by conr, i h ldom bn ud. Wih low-frquncy ocilling condiion of vrl Hz which i commonly ud, hor circui occur rgrdl of h ocilling orch poiion. In hi c, hr i h fr h ny chng in currn/volg du o orch ocillion would b mikn for h vriion cud by hor circui. By lcing uibl ocillion frquncy undr high- frquncy ocillion condiion, i bcom poibl o limi h poiion which hor circui occur o h ocillion nd only. Thi i xpcd o rduc h vrinc in d for m rcking conrol. According o h rul of n nlyi of rc nor niiviy uing h frquncy rpon mhod 10), h rc nor niiviy o boh wlding currn ignl nd orch volg ignl incr in h ocillion frquncy rng in which h orch ocillion frquncy i bou hlf of h hor-circuiing frquncy wihou ocillion. Thu, whn i com o pplying n rc nor undr hor-circuiing rnfr condiion, lcing h opimum ocillion frquncy i n ffciv mn of implmning highly ccur conrol. 4. Concluion A nw GAM wlding proc modl, modl for hor rc wlding w dvlopd bd on h xiing modl for pry rc wlding. In ddiion, by pplying h nw modl, n nlyi w conducd on h hor-circuiing dynmic in high-pd ocilling GMA proc nd dicud guidlin on h opimizion of rc nor propri. Thi rc nor chnology h bn inroducd in h uomic lin pip wldr MAG-II 11) for groov cnr rcking nd ocillion widh conrol nd h provd ffciv in improving h quliy of nrrow-groov, ll-poiion wlding. Li of ymbol Symbol of pry rnfr condiion A : Arc hing cofficin of wir mling, 0.22mm A B : Joul hing cofficin of wir mling, A 2 E : Elcric fild inniy in rc column, 0.7 Vmm 1 I : Wlding currn, A J : Joul hing wigh of wir xnion, L A2 J : Joul hing wigh h locion z of wir xnion, z A2 K : Slop of h U-I chrcriic of powr ourc, 0.02 L : Arc lngh, mm L : Wir xnion lngh, mm L : Inducnc of circui, H L : Torch high (L + L ), mm R : Elcric rinc of rc column, 0.03 R : Rinc of wlding powr cbl, c R : Rinc of wir xnion, r (J z ): Rinc of uni lngh of wir xnion funcion of J z, J z mm : Tim of imulion, U : Arc volg, V U : Conn componn of rc volg, 16V o U : Volg drop cro wir xnion, V U : Equivln oupu volg of powr ourc in h of I = 0, V U : Wlding volg (U + U ), V V : Wir fding r, mm f V : Wir mling r, mm m : Tim, Symbol of hor-circuiing rnfr condiion B : Joul hing cofficin of wir mling hor-circuiing, mm A 2 1 L : Dropl lngh, mm m L : Wir xnion lngh of no-mling pr, mm N : Numbr of hor-circuiing wih ocillion, N : Numbr of hor-circuiing wihou ocillion, o R : Rdiu of dropl h uppod phricl hp, mm m S : Cro cionl r of wir, mm 2 : Tim whn i h hor-circuiing i brokn, i : Tim whn i h hor-circuiing i rd, i α : Cofficin of dropl lngh, 3 β : Cofficin of hor-circuiing im, 200 Symbol of orch ocillion f : Ocilling frquncy in groov, Hz W : Ocilling widh, 3mm X : Ocilling poiion, mm Rfrnc 1) Lnwich, A.: Wld. J. 37(8), (1958) 2) Hlmoy, E.: Confrnc on Arc Phyic nd Wld Pool Bhvior. London. 1979, p ) Mruo, M. l.: J.Jpn.Wld.Soc. 3(1), (1985) 4) Uhio, M. l.: J.Jpn.Wld.Soc. 14(1), (1996) 5) Uhio, M. l.: J.Jpn.Wld.Soc. 14(1), (1996) 6) Nomur, H. l.: J.Jpn.Wld.Soc. 4(3), 18-23(1986) 7) Uhio, M. l.: J.Jpn.Wld.Soc. 15(2), (1997) 8) Hir, Y. l.: J.Jpn.Wld.Soc. 22(2), (2004) 9) Hrmn, dn Oudn: Sci. Tchnol. Wld. Joining. 3, (1998) 10) Kodm, S. l.: Sci. Tchnol. Wld. Joining. 11(1), 25-32(2006) 11) Nkmur, S. l.: Shinniu Giho. (382), 48-52(2005)