NUMERICAL SIMULATION OF KEYHOLE S DYNAMIC VARIATION IN CONTROLLED PULSE PAW PROCESS

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1 i 47 Ξ i 8 X Vol.47 No R 8. i fi ACTA METALLURGICA SINICA Aug pp Ωffls PAW rχψwßn vν%.* /'-,(+ (vrt~+-ffiffoρπff$w g(pjξ ffi, QK "! 9BI efl`9+j (PAW ':L, h rz(+jm2t1fia, zψλr7 5U,h μ1±b fia':. P2 9B PAW ψ1nw2wtflfgpbgfw, 9'ΠY+jn>χBb %Z1, b#+h rzbg p, Ω4+= (h }wh"μ_5w /I=h 2 fibν. +jn>lsih 2ffl 9BRYLbfiA':wt+flF R&. wt+ 9B PAW μ»πφ, Φ@+I <z ZbflFΠYp$. }Ξt 9BI, efl`9+j, h, t1fia, flfgp &ρy ff TG456.2 fiffio»ffi A fi#m ( NUMERICAL SIMULATION OF KEYHOLE S DYNAMIC VARIATION IN CONTROLLED PULSE PAW PROCESS SUN Junhua, WU Chuansong, QIN Guoliang Key Lab for Liquid Solid Structure Evolution and Materials Processing (Ministry of Education, Shandong University, Jinan Correspondent: WU Chuansong, professor, Tel: ( , wucs@sdu.edu.cn Supported by National Natural Science Foundation of China (No and Specialized Research Fund for the Doctoral Program of Higher Education (No Manuscript received , in revised form ABSTRACT During the controlled pulse key holing plasma arc welding (PAW, keyhole shape and size change with the welding current dynamically, and undergo variation of the establishing expanding contracting closingπprocess. Numerical analysis on such dynamic variation process of keyhole shape and size can provide insight into the process mechanism and basic data for optimizing the process parameters. In this study, a three dimensional transient model is developed to conduct numerical simulation of welding temperature field, weld pool geometry, and keyhole shape and size in controlled pulse PAW. The keyhole shape and size are computed by analyzing the force action on the weld pool surface, and two situations are considered to deal with partial keyhole and open keyhole. The dynamic variation features of three dimensional keyhole shapes in weld pool in a pulse cycle are numerically calculated. Experiments are conducted to validate the numerical simulation result of key holing duration. KEY WORDS controlled pulse key holing, plasma arc welding, keyhole, dynamic variation, numerical simulation J qfffia:,k (PAW %Kψ, naff, ; "HfflN*Ax,k, 3_WK4flM!!ρcff ffi^. ' n3j PAW Λ, flffic,kν /ffi G6, floxi, K-^ffν 3K4flMcV*ffffi. H,BμJ q PAW cν /ffif[, Φ,»»:C PAW ν (O3Λ$:Cn3cHGx, 3:C]eΞ * #Vbifi GvcI /ffie j%ff fikxcfi GvcI _W ]D my : , ]wfi my : g: t : + >, T, 1979 S, %ff DOI: /SP.J X, 2 Dey, l6±! K 1 0 K 2 [1,2], ffν fl! kh»k,kkμr, 5fflfffia:,kν x0,k (;csqv. Zfi,»»:CJ PAW cν /ffih }, ~ao?0i SZv:Cn3 u2flb. H,iΩ»»:CJ PAW cν Iχ, ±_[ν χb, yω-ffiffighqpß o? i :Cn3cu2 flb(;xuq*±z, F`»Oν 8`]cHGffi. J^! } [3 6] Hfi< ΞJ c:culk:,k k3xu,ffig±z. 3J q PAW k3cffighqλ C, VΩfi< ' n3 PAW Φ7,h}c } [7 13], C?!< :C PAW,kk3c }ffl_. #m

2 1062 u ν } fl i 47 Ξ 7c»»:CJ PAW mν, ylφ7[k(; N o? i u2uhcffighq }.»Q:(±Zi οcxc&w4[2, c$i s[cu2flbhq,»»:cj PAW Λ :CSZMi cu2flb (;xuffig±z. 1 ψuπfi»»:c PAW Λ, -ffi3 Sc,kn3$s, Tfl ffao?j ν`o>, ±_ΞXC,k χ C8s, ;Λfffl ffaa0 2 :C/s8co> o?a<qk, ±_-c,k8s [1,2].»»:C PAW!2k3, M#,ΦψCci MnH*lc$ x y z uiffi[, q@ 1 /Ω.,k(;kL F±Λ ;H [14] ( T ρc p t v T 0 x = ( x k T x + ( k T + y y ( k T + q v (x, y, z, t (1 z z ΦM, ρ HAx, C p H k, T HOx, t HΛ[, v 0 H, k%x, k Hk 6, q v (x, y, z, t H7Jk,. c$][c fl fl PAW (;3lc7Jk,± 'HΦ q v (x, y, z, t fiffighqcfl^. ff5^»»:c PAW N*AxfflxMMN,Φ!V~μ c3l, - ffiξχad7 + 7 ce2φ7jk,hφ.,kn3 -ffi»»szv:cn3, οm,,kn:c!kkο6 Q(t =ηui(t fffiλ[szflbc*ffi, [M η fin :kk6, U fin:n, I(t fi!2,kn3. k, Ξν`6xΛf, x* (0 z c -ffiχad7 q v (x, y, z, t = 6 ( 3m 1Q(t a f bcπ π exp 3x2 3y2 a 2 b 3z2 f 2 c 2 (x 0, 0 z c 6 ( 3m 1Q(t a rbcπ π exp 3x2 a 3y2 2 r b 3z2 2 c 2 (x <0, 0 z c (2 ]* (c <z c + h -ffi 7k, q v (r, z, t = ( exp 3r2 r 0 z 2 9e 3 m 2 Q(t πh(e 3 1(r 2 e + r e r i + r 2 i (c <z c + h (3 ΦM, a f, a r, b 0 c fiχad7k,c7j±'/ffi; r e 0 r i fi 7k,c7J±'/ffi; h fi 7k,cfflx; m 1 0 m 2 ±!fiχad7k,0 7k,8!cN* ±ffi. 3»»:CSZM,,kn33 G= yλ [7, o?ho>, ]-s8j ; [,kn3o G qcl6d<egλ, i <<fli, D^ν2; ;Λ, o?ψho>f*±o~[2yb. ] SZΦ, s8 mci "QΩxρ(; [1].,ko?3fffia:& Q &0ψC9&cß;hffi] ψcfls, Ii s8; "ai,kn3cflb±_ξφ ν YE. οm, o?ψcflst60i s[a`afl, yωff5o?c Lo>0ho> 2 Ocο [15]. 3Lo>cο],,ko?H! cψψc, ψc flsλ;h fl, O p a ρgϕ λ = γ (1 + ϕ2 x ϕ yy 2ϕ x ϕ y ϕ xy +(1+ϕ 2 y ϕ xx (1 + ϕ 2 x + ϕ 2 y 3/2 (4 Φ (4 c-ff8`fifls^7co? 7Jff=& Ω ϕdxdy =0 (5 ΦM, p a fifffia:&; ρ fiax; g fiq&x%x. ϕ fio?xψccs[*ffi (ϕ x = ϕ/ x, ϕ xy = 2 ϕ/ x y; λ fi Lagrange 4ffi; γ fiψc9&; Ω fio?xψc/ 8cf'. Lo>cο], o?ψc]ψflsß7h> sφc i. o?cxψcs[*ffi ϕ, ~fii cs[*ffi. 3ho>cο],,ko?Ωx ] 2 cψψc, ψcflsλ;h p a ρgϕ λ = γ (1 + ϕ2 x ϕ yy 2ϕ x ϕ y ϕ xy +(1+ϕ 2 y ϕ xx (1 + ϕ 2 x + ϕ 2 y 3/2 (6 Fig.1 ff 1 I efl`9+jψμ? Schematic sketch of key holing plasma arc welding (K PAW system ρg(ψ + H+λ = γ (1 + ψ2 xψ yy 2ψ x ψ y ψ xy +(1+ψ 2 yψ xx (1 + ψ 2 x + ψ2 y 3/2 (7

3 i 8 X *±=d : 8A PAW &9gffls0ff@afiEFO 1063 ;dφ (6 0 (7 c-ff8`h ϕdxdy ψdxdy =0 (8 Ω 1 Ω 2 ΦM, ψ fio?]ψccs[*ffi (ψ x = ψ/ x, ψ xy = 2 ψ/ x y, ψ» -ffi *iffi[ x y z, iffi* lm#fffia:,λt`%ν`]ψccfl; H fiν `6x; Ω 1 0 Ω 2 fio?x ]ψc/8cf'. #ho>o?, i!> (i ~xi#ν`6 x 0s8J (i ~xf#ν`6x 2Ocο, ϕ fi i cs[*ffi, ~ ψ ljfio?c]ψcs[*ffi. Φ (4 0 (6 M p a -ffiχa+±'cfffia: & [12], ψc9&fioxc*ffi [16]. -fficßs8`h ϕ(x, y =0,T T m (Uppersurface (9 ψ(x, y =0,T T m ( lower surface (10 HqM,,.ck 6 k0ψcuk[ffifiox c*ffi [14]. 2 zx 0ffi»KpJ»KΛ;Nßs8`xuffiuB, "a-ffihρφ1± Φ. "ffi FORTRAN &Λρ;, :( kl Λ;cer, S'E!2,kOx3. Y o?e_, -ffilo>cο]co?ψcflsλ;n[ß s8`, i s[xuer Φ^:Cn3Λ[cfl B,,ko?x (flv, [,ko?±_ho>7, -ffi ho>8`]co?ψcflsλ;nßs8`, i U xuer.»qm-ffic»»:cn3fiλ[c*ffi, ο~n:kμr0fffia:&fffiλ[&zflbc, x ~:(S'e`co?0i fffiλ[u2flbc. ; Λ, ff5s'yx0s'%x, -ffi2flc (V, ( }NpW;d (8`. H,5fflS'yx, d 100 mm 60 mm 6 mmc S'f'?± ΞΠ/D. 3o?f MOx4xhffl, -ffi D?±, D [ fi 0.2 mm. 3= S'(;M, -ffifiqλ[( s. 3 μ$λο±~ fl "ffi/c$ck,hqni S'Hq, 6mm 6&xflffl`»»:CJ PAW Λi cu2flb( ;xu,ffigs'. ν 8`H: n:n 21 V,,k% mm/min, ffia 3*H 3 L/min, ff; 3*H 20 L/min,»»:C PAW ν /ffi]ψ 1. -ffixρν 8`Φ7»»:C PAW ±Ψ, :(ffi -M[<Fg,kn30K±n o.. ±Ψ _, 3 ß: 9.0 s :CSZM cxχ(;qω. οm, g t=9.0 s C7c :CS Z,»»:C PAW o? i xuffig±z,»»: Cn3$sΩν@q@ 2 /Ω. [M t 1 t 4 Λ[yH Gn3hffiΛ[, t 4 t 9 Λ[yHn3»»]ely. g ff#»»:cn3 SZM&;Λffici s[xus', q%q@ 3 /Ω. ψ@ 3 Mi 3&; ΛffictJs[fl ΨE, 3 :CSZM,,ko? cs[0@p,kλ[ (n3 &zflb; o?3fffi a:& ψc9&0q&cß;hffi], i ff3u2fl B. 3 Gn3hffiZ[ (t 1 t 4,,ko?&zflV" fnr^ho>[2, i ffc&zflv, "a3 t 3 Λ ffi 7Φ s8j, 3 t 4 " 3 Gn3hffiqff7$ffiΦ fli; ψ#kχv,,k o?3 Gn3hffiqff7"?!$ffifli, ~fi3 G n3fhgn3ye(; (t 4 t 8 Mc t 6 ΛffiR^fV G71Uafli, ;fiοh»q3i cs'(;mhff 5,i οcxc&w4,?!;λff5i οcxck W4, / #i s[?!7_ekχvcfib; 3 t 5 Λffii Φ ν2, 7Uafli; 3HGn3hffiZ[ (t 8 t 9, o?0i vuafli, "a3hgn3hffiq 4 ΩE, :CSZMi x z 0 y z ncc p 1 9B PAW μ».fl Table 1 The welding process parameters in controlled pulse K PAW I P I B t P t B t C I K1 I K2 K 1 K 2 A A s s s A A Note: I P peak current, I B background current, t P peak current duration, t B background current duration, t C pulse period, I K1, I K2 transition currents at the end of current respectively stages with slope of K 1 and K 2, respectively, K 1, K 2 descending slope in the two current descending stages as show in Fig.2 ff 2 9B+jm2#rΨμ? Fig.2 Schematic of controlled pulse welding current waveform (t 1 t 9 are the special times selected for keyhole shape calculated

4 1064 u ν } fl i 47 Ξ Fig.3 ff 3 sih rz2? 2.Ψffl 9BRYL( ZbfiA Evolution of 3D keyhole during a pulse cycle corresponding to different times as shown in Fig.2 at t 1 =9.1 s (a, t 2 =9.45 s (b, t 3 =9.475 s (c, t 4 =9.85 s (d, t 5 =9.88 s (e, t 6 =9.9 s (f, t 7 =10.05 s (g, t 8 =10.25 s (h and t 9 =10.4 s (i

5 i 8 X *±=d : 8A PAW &9gffls0ff@afiEFO 1065 ff 4 ffl 9BRYLh x z / y z mbbfia Fig.4 Evolution of keyhole shape during peak current period (a, b and current decreasing period (c, d (a, c section of x z plane (b, d section of y z plane flb. ψ@fl], 3 Gn3hffiΛ[y, i Λ[^ 7!,s8 6V J c(;, 3 t 3 ΛffiΦ R ^J [2 (@ 4a 0 b; 3n3»»]ely, i Λ[Ua-i, O t 5 ΛffiΦ ν2 (@ 4c 0 d. i C hj=φ [2cΛ[yH t 3 t 5, ß s. 3»» :C PAW ±Ψ(;M, ffi AM1101 q CCD zeiu zν` ffi0i OΞSΦ ^Ξν2 c u2flb(;, Uz%xH@D 30 >. fl:(%i ffmjce$ffivzi [2, [o?j Λ, i ffce$ffi %5X, ψem#ν` Cc i WCCJ %5X, [i ν2λ, i ffce$ ffih 5 ΩE, Ci ffe$ffiλ[cflb. ψ@flb, i 3 :CSZMJ=J [2cΛ[H s, ψes'q%%±ψq%r ±fl -ffiξχad + 7 e2φ7jk,hq, 0ffi, ko?cψcflsλ;,»»:cfffia:,k(;m ff 5 Bh?dbd#fl( ZbfiA Fig.5 Variation of the pixel numbers in the backside keyhole images ci u2flb(;xu,s', q%ψe3»»: Cn3SZM, i!ξs8 6V -i ν2 c!λflb(;,»q q,k8`]j=j Λ[cS 'q%h s, ±Ψ0*q%H s, S'q %%±Ψq%Ψ2-.

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