SIMULATION OF NI 3 AL-BASED ALLOY AND INVESTMENT CASTING ROCESS OF ITS THIN WALL ARTS Zhan Xi-e, Cao X, Lo He-li, Fen Di, Li Shan-pin Cenral Iron and Seel Research Insie, Hih Temperare Maerial Research Insie, Beijin, China ABSTRACT: The casabili is poor o prodce hin all comple casins of he Ni 3 Al-based allo b inesmen casin. In eneral, sch as incomplee mold fillin and ho ears defecs appear commonl. In his paper, phsical parameers of Ni 3 Albased allo are obained b eperimens and simlaions sin Jmaro sofare, and casin process of hin all pars is opimied b he simlaion of hea ransfer, flid flo and sress calclaion sin rocas sofare. Throh simlaion, a differen lo emperare porin echnolo is applied o improe he qali of casins and ain confiraion is opimied o increase fillin abili and decrease ho earin endeniosness. Keords: Ni 3 Al-based allo; Thin all pars; hsical parameers; Inesmen casin; Simlaion Inrodcion The casin processin of hin all pars is he essenial and ren echnolo of deelopin aiaion, space, elecron and insrmen indsr for sain eih and ener [1]. Thin all casins of Ni 3 Al-based allos hae achieed idel se becase of lih eih, hih srenh and hih oidaion resisance a hih emperare. Inesmen casin in acm is he acceped sandard processin in prodcin he Ni 3 Al-based allos. Hoeer, he processin of hin all casins of Ni 3 Al-based allos is er difficl. Man defecs ofen occr sch as incomplee mold fillin and ho ears. Comper simlaion of casin is becomin more sinifican noadas []. Defecs like porosi, shrinkae, disorion, nder fillin, cold shs, as enrainmen, rblence, mold erosion and ho ears can be idenified in adance and correc measres can be aken in he desin sae iself [3]. Casin simlaion as firs applied o prodce eqiaed inesmen casins in he earl 1980s [4]. I has ron rapidl ih increasin sophisicaion of comper hardare and sofare. There are los of casin simlaion sofares noadas. In he meanime, hermodnamic modelin ools for eplorin he eqilibrim and phase relaionships in comple maerials hae become increasinl sed in acal indsrial pracice [5]. This paper ill demonsrae he applicaion of rocast and Jmaro sofare in he casin process of hin all casins of Ni 3 Al-based allos o opimie he casin process. The oal of his sd as he improemen of he casin process sin he sofare rocast, hich is ailored o casin simlaion and soles he hea ransfer problem b he finie elemen mehod (FEM). Jmaro sofare (Jaabased Maerials roperies sofare) is a ne comper proram and sed o calclae he hermo-phsical properies of Ni 3 Al-based allos. Tha is er helpfl o kno ell ih ha maerial and prepare he daa for casin simlaion. 3-101
MATERIAL CALCULATION Thermo-phsical and phsical properies are an imporan par of maerials science, pariclarl a he presen ime hen sch daa is criical inp for ne sofare prorams dealin ih process modelin. Some of hose daa of Ni 3 Al-based allo e sed lised as follos are achieed b esin. Densi (a room emperare): 7.9/cm 3 Melin poin: 130-1357 Epansion coefficien: Table 1 Epansion coefficien of Ni 3 Al-based allo emperare( ) epansion coefficien (10-6 -1 ) 5~ 5~ 5~ 100 00 300 5~ 5~ 5~ 5~ 5~ 400 500 600 700 800 1.39 1.3 1.56 13.74 13.916 14.413 14.893 15.473 Hoeer, mos of hermo-phsical properies are er difficl and epensie o es pariclarl a hih emperare. Therefore, e can obain hose daa b he aid of comper calclaion sch as Jmaro sofare. Fi.1 o Fi.6 are some of hose daas a differen emperare. Fi.1 Thermal condcii Fi. Yon s modls 3-10
Fi.3 oisson s raio Fi.4 Liqid iscosi Fi.5 Specific hea Fi.6 Densi CASTING SIMULATION Usin he commercial sofare rocast carried o he comper simlaions of he mold fillin process. The simlaion process is as follos. Mahemaical model The fillin and casin of liqid meal is he flo process in he comple mold ih resis and free srface and he hea ransfer process ih he mold [6]. Tha phsical process follos conseraion of mass, momenm and ener. Liqid meal is assmed o incompressible and iscos liqid and he rblen flo is inored. 1) Mass conseraion eqaion [7] ( ) ( ) ( ) here is densi, is ime,,, is he componen of eloci of,, direcion. ) Momenm conseraion eqaion (Naier-Sokes eqaion): = 0 (1) 3-103
3-104 ( ) ( ) ( ) ( ) = μ () ( ) ( ) ( ) ( ) = μ (3) ( ) ( ) ( ) ( ) = μ (4) here is pressre,,, is he componen of rai of,, direcion, μ is dnamic iscosi. 3) Ener conseraion eqaion ( ) ( ) ( ) ( ) S T λ T λ T λ T C T C T C T C = (5) here C is he hea capaci, T is emperare of liqid, λ is he hea condcii of liqid, S is he hea sorce. 4) Volme fncion eqaion (Free srface conrollin eqaion) ( ) ( ) ( ) = 0 F F F F here F is he olme fncion. Solid modelin and mesh eneraion Three-dimensional eomer of ae confiraion is compleed b sin commercial sofare Solidorks shon as fire 7. I is conenien and fleible in drain solid models. Oin o smmer, half of he ae confiraion is modeled. Then, srface mesh is eneraed b sin ro/enineer sofare, becase i has ecellen connecion ih casin simlaion sofare named rocast. Mesh eneraion is a er imporan par in he casin simlaion. Finall, srface mesh is acceped in rocast and olme mesh is finished. Becase i is inesmen casin, he ceramic mold is a shell, approimael 7mm hick, ha srronds he casin eomer. The amon of finie-elemen canno be oo mch, hich ma inflence he calclaion speed and canno be oo lile, hich ma inflence he calclaion precision. When he mesh eneraed shon as fire 8, i is hen read for he applicaion of bondar condiions.
arameers and bondar condiions hsical parameers hae been described in he aboe maerial calclaions. Bondar condiions mainl refer o hea ransfer coefficien beeen liqid meal and shell and hea ransfer coefficien beeen shell and enironmen. In addiion, radiaion ms be considered becase of ho mold in inesmen casin. Iniial condiions To processin parameers, e choose reasonable ale accordin o maerial iself and inesmen casin process. The porin emperare e choose is abo 1480, he iniial shell emperare e choose is abo 600. Fi.7 Gae confiraion Fi.8 Volme mesh RESULTS AND DISCUSSION From casin simlaion, emperare fields, flid fields, sress disribion, shrinkae and man oher resls can be shon. Incomplee mold fillin and ho ears are mos familiar defecs in he casin of hin-all pars, so e onl see he mold fillin process and emperare drop process. Fillin capaci The fillin process is shon as fire 9. From he simlaion resl, e can see his ain confiraion is reasonable for fillin o his hin all pars. When he 3-105
flid flos o he hin all par, is emperare decreases er lile. Therefore, incomplee mold fillin can be aoided. Fi.9 Fillin process Temperare fields The emperare field is shon as fire 10. From he simlaion resl, e can see ha in some pars of he hin all casin solidif mch faser han hose pars ha are near he ae rnner. Ths, he pars ha solidif laer old prodce a ensile force in shrinkae process. The hin all par is onl 1mm hick, and i can endre lile force. Therefore, ho ears ma appear in he pars ha solidif earlier as shon in Fi.11. Fi.10 Temperare field Fi.11 Ho ears To improe his ae confiraion, ho ears ms be aoided. Therefore, i is beer o keep he solidif ime differs no so mch in he hole hin all pars. Some 3-106
ribs are added in he eak pars o aoid ho ears shon as fire 1. From he simlaion shon as fire 14, e can see he emperare field ends o be nearl niform. In he acal casin, ho ears are eliminaed. Fi.13 Improed ae confiraion Fi.14 Temperare field of improed ae confiraion Conclsions 1. Throh combinaion of maerial calclaion and es, he phsical properies of Ni 3 Al-based allos are obained. Tha is imporan for he sd of maerial iself and casin simlaion.. Mesh eneraion, bondar condiions, iniial condiions and oher facors are er imporan o he speed and precision of casin simlaion. 3. Incomplee mold fillin and ho ears defecs appear commonl in he hin all casins. From simlaion resls, he casin parameers e choose are reasonable for mold fillin. Hoeer, he former ae confiraion is no siable o aoidin ho ears. Ribs are added in he eak pars o aoid ho ears. REFERENCES 1. NIYAMA Eiske e al., Some basic research for hin-all casin echnolo, Jornal of Maerials rocessin Technolo 63(1997) 779-783.. S.Slaiman, A.M.S. Hamoda, Modelin and eperimenal inesiaion of solidificaion process in sand casin, Jornal of Maerials rocessin Technolo 155-156(004) 173-176. 3-107
3. Casin Simlaion, hp://.inds-sa.com/pro-simpics/casinsim.hml. 4. John S. T e al., An Ineraed rocedre for Modelin Inesmen Casins, JOM 47(10) (1995)64-68. 5. N.Sanders, Z.Go e al., MODELLING THE MATERIAL ROERTIES AND BEHAVIOUR OF Ni-BASED SUERALLOYS, TMS (004)849-858. 6. K.Raindran, R.W.Leis, Finie elemen modelin of solidificaion effecs in mold fillin, Finie Elemens in Analsis and Desin 31(1998) 99-116. 7. J.A.Dani, Solidificaion Modelin: Sas and Olook, JOM. December (000)18-1. 3-108