NGHIEN CUfU-TRAO Ddi U'NG DUNG P H A N M £ M C O M S O L M PHdNG QUA TRJNH NUNG C A M U'NG D^N TRANG T H A I B A N L N G C O A PHOI HE HOP KIM NHOM TRONG CONG NGHE TAO HJNH THIXOFORMING THE APPLICATION COMSOL SOFTWARE TO SIMULATE THE INDUCTION HEATING PROCESS TO ALUMINIUM ALLOY'S SEMISOLID STATE IN THIXOFORMING PROCESS NguySn Vinh DyS Trinh VSn Quoc^ Luu Phwong Minh' 'Sd Khoa hpc va Cdng nghe TR Hd Chi Minh ^Trudng Dai hgc Su pham Ky thuat TP Ho Chi Minh 'Trudng Dai hgc Bach Khoa TPHd Chi Minh Ky thudt Thixoformingyeu cdu gia nhiet phdi din trgng thdi bdn long truac tao hinh cho nhiet duac phdn bo dong deu trin todn bg thi tich cua vgt nung Td chuc ti vi cua phoi CO dgng cdu vd co ti le pha ran- long theo mong mudnphdn bd deu Trong qud trinh nung, mgt sd hien tuang vgt ly se ldm dnh huong den tinh chdt bdn long cua phdi Trong nghiin cicu ndy, nhom tdc gid su dung phuang phdp ly thuyet truyin nhiet, phuang phdp so kit hgp vai phuong phdp mo phong bdng phdn mem comsol di xdc dinh chiin lugc nung din trgng thdi bdn long Cdc kit qud dat duac ldm ca sa toi uu qud trinh thuc nghiem vd tiet kiem thai gian kiem tra cheo cdc tinh todn bang phuang phdp so, tir di ldm tien de cho viec phdt triin cong nghi a mice cong nghiep vd tdi lieu tham khao cho viic ndng cao hieu qud phuc vu cho cdc nghien cim linh vuc nung cdm ung noi chung vd tao hinh vgt lieu a trgng thdi bdn long noi rieng Tfr khoa: Ky thudt thixoforming, nung cdm img, phuang phdp so, phdn mem mo phong comsol ABSTRACT Thixoforming technique requires casting metal alloys when they are partial liquid and partial solid before the material flow into the die cavity under pressure, the temperature distribution must be uniform within the billet at the end of heating, in order to obtain a good microstrucre In this papers, the authors use theoretical heat transfer, numerical method and combine with the Comsol software simulating method to confirm and suggest strategies for practical process aiming to save re-inspecting time of the calculation process by numerical method This is the basis to develop technology at industrial level and create basic premises in raising the application effects for studies of induction heating (in general) and thixoforming techique (in particular) Keywords: Thixoforming technique, induction heating, numericalmethod; the Comsolsimulating software ^ ISSN 0866 - 7056 TAP CHf CO KHf VIET NAM, Sd nam 2015 www.cokhivietnam.vn NGHIEN CUfU-TRAOD6I G I O ! THIEU Ky thuat tao hinh vat lieu mdi eo ten la tao hinh vat lieu d trang thai ban long da dugc bit diu va phat triin bdi Giao su Merton C Flemings ~ Vien Ky thuat Masasuchet, Hoa Ky Trong nhilng nam gin day, ky thuat tao hinh da dugc bit diu thuong mai hda dua vao san xuit cong nghiep So vdi cac phuong phap tao hinh truyin thdng d hang thai chay Idng hoan toan, thi kim loai tao hinh d hang thai ban long dugc dieu khien den hang thai nua dac va nua Idng nham cho ddng chay cd dp nhdt cao han suot qua hinh tao hinh do chat luang vat due cung cao hon vi vay khac phuc dugc tinh hang quan hong vat due Cdng nghe naycho chat lugng be mat vat due tdt, kha nang chiu keo cao, rd be mat d miic thap, vat diic CO td chuc te vi tot, tiet kiem dugc nang lugng hong qua trinh tao hinh, dac biet doi vdi nhiing san pham doi hdi dung sai kich thudc nho [1-6] Ky thuat tao hinh vat lieu d trang thai ban long CO hai hudng eong nghe: Rheoforming va thixoforming Khae vdi phuang phap rheofomiing la di tir trang thai long xudng trang thai ban long, phuang phap thixoforming dl tii hang thai ran den ban long Ky thuat tao hinh theo thixoforming ddi hdi nung phdi ban dau trudc nham tao mdt cau tnic tot vdi ti le phan ham pha Idng khoang 40-50% Nhiet nung phai dugc kiem soat mdt each chinh xac nham dat den sy dong deu ve nhiet hen toan bd the rich vat lieu Trong pham vi nghien eiiu eiia bai bao nay, nhdm tac gia sir dyng phuang phap nung cam ung phyc vu cho qua hinh chuan bj phdi ban dau, day la phuang phap duge sir dung phd biln, dac biet la hong quy trinh tao vat lieu d trang thai ban long vi phoi dugc nung khdng tiep xiic tryc tilp vdi nguon nhiet Nung cam ling cd uu dilm sach, thdi gian nung nhanh va dac biet nguin nang lugng dau vao dugc kiem soat de dang Tuy nhien, nung cam ung co nhuge dilm co hmi la nhiet hen toan bg thi tieh vat lieu khdng ddng diu hieu ling be mat, hieu ung dau cudi (hieu ling ket thiic xay d giai doan cudi qua trinh nung), hieu ling dien hi, mgt hong nhihig yiu td anh hudng den qua trinh nung Muc tieu ciia nghien eiiu la de chien lupc nung hgp ly va mgt nhilng cdng cy hd h g giup cho ket qua nghien ciiu kha thi la ket hgp phuang phap tinh toan qua hinh nung bang phuang phap s6 va kiem tra cheo bang phuang phap mo phdng sir dung phan mem comsol - day la phuang phap duge cac nha nghien ciiu sii dung phd bien, ciing la ly ma md hinh hoa va md phdng so qua trinh nung cam ling duge cae chuyen gia quan tam va phat trien [6-7] Hinh 1.1: Phdi nung trgng thai hdn long NOI DUNG NGHIEN CUtJ Trong nung cam ling, gia tri eua mat dong dien tdi da la d tren bl mat eua ehi tiet va se giam mdt each nhanh chdng nd di sau vao ben hong tam Hien tugng dugc gpi la hieu ung be mat Do hieu ling be mat nen nen hau het ngudn nhiet deu tap trung len be mat cua chi tiet Khoang 86% nhiet lugng duge eung cap d lop be mat va dupe ggi la chieu sau thim, chieu sau se giam tan sd tang dd de dam bao dp chenh nhiet dp toan bp thi tich cua phoi nung, vl the de giam thilu tii da hieu dng be mat va tdi uu thdi gian nung, nhom tac gia su dung chien lugc nung viia gia nhiet va vua lam nguoi dong thdi tren be mat cua phdi nung va su dung tin sd nung 20 KHz de khao sat su thay ddi nhiet dp giiia tam va be mat phdi ISSN 0866 - 7056 TAP CHf CO KHf VIET NAM, S6 nam 2015 i\ww.cokhivietnam.vn NGHIEN CUfU-TRAO B I Trong qua hinh tim chien lugc tren, nhdm tac gia su dung phuang phap sd dl tinh toan, uu diem cua phuang phap sd la phan rich toan hpc dl tim ldi giai ciia qua trinh la rit chat che, khai niem vat ly va logic suy luan rat rd rang, nghiem dugc bieu diln dudi dang ham sd nen thi hien rd rang mue dg anh hudng cac nhan td din su phan bd ciia trudng nhiet dp Ngoai ra, uu diem cua phuang phap sd la chd nd ed the giai quyet dugc cae van de truyen nhiet thyc te ma cac phuang phap khac khdng lam dugc, ddng thdi theo dung lugng cua may tinh, tdc tinh toan tang cao thi pham vi ung dung phuong phap sd, quy md; Toe va dp chinh xac tien trien rat nhanh nen no da trd mdt phuong phap hihi hieu de giai cac bai toan dan nhiet phuc tap hong ky thuat Va de giai bai toan truyen nhiet hen, nhdm tac gia su dung phuong phap sai phan hiiu ban, su dung tri nhiet dp gan dung tai cac diem nut (ling vdi khong gian va thdi gian xet) cua phan tl (phin td) dl thay the cho su phan bd nhiet dp lien tuc thyc te vat the, dem nghiem ham sd phan bd nhiet dp lien tyc chuyen hda nghiem ciia tri nhiet dp t^i cac diem nut, thdng qua each se dem vin dl giai phuong trinh vi phan din nhiet chuyen giai he phuang trinh dai sd tai cac diem mit cua phan to Do dd, phai chia nhd vimg xem xet bai toan, thiet lap he phuong trinh dai s6 nhiet dp t^i cac phan td va giai, la ndi dung chii yeu eua phuang phap sd [8] MO HINH HOA VA MO PHONG SO V^T LY CUA QUA TRINH NUNG CAM ITNG 3.1 Md hiuh hoa va giai bai toan toi ini b^ng phirong phap C G M (Coujuntion Gradient Method) Chi tiet dugc nung bdi cum thiet bi cd dae tinh ky thuat: Dien ap vao 220V, cdng suat 3Kw, tan sd nung dao dgngtul5KHz-25KHz « Mo hinh vat ly cua qud trinh nung cam ung - Phdi nung la hgp kim nhom A356, hinh try cd dudng kinh 80 mm, chieu cao la 50 mm, dupe dat theo phuang thang dung (Hinh 3.1), ngudn nhiet ben hong dupe tao nhd su cam ling dien tir de dam bao dupe ty le pha ran va pha Idng la 45 - 50% thi phdi nung dugc gia nhiet din 585°C Hinh 3.1: Md hinh vgt ly sit dung cho qud trinh nghien cuu b Hffp kim A356 Do tinh chat vat ly ciia phoi nhom A356 cd khoang nhiet dp chuyin trang thai tii dong dac sang long hoan toan tuong ddi Idn, khoang 65*'C nen rat ling dung de tao hinh phoi nung d hang thai ban Idng dd hong nghien ciiu hap kim Nhom A356 dupe sir dung de tien hanh cac nghien ciiu va hgp kim cd phan hoa hge nhu sau: g- 3.1 Thdnh phdn hod hgc ciia hgp kim Nhdm A356 [11] Si 6,59 Fe 0,01 Cu 0,12 Mn 0,005 Mg 0,39 Zn 0,005 Ti 0,005 ISSN 0866 - 7056 TAP CHf CO KHI VIET NAM, Sd nam 2015 www.cokhivietnam.vn NGHIEN CUTU-TRAODC!)! Nhiet ma phdi hpp kim Nhdm A356 dat Dieu kifn bien: din trang thai ban Idng f = 50% la khoang 583^ 585°C theo nghien ciiu cua nhieu tac gia [11] • Tair=0: k—= dr Bdng 3.2: Tinh chat vat ly cm hgp kim NhdmA356 [H] Tair=R: Nhiet dp Dong chay, "C Nhiet dp dong dac, °C Nhiet dung rieng cua vat lieu (J/kg°C) Dp dan nhi?t ciia vat lieu (W/m °C) Khoi luong rieng ciia chi tijt (kg/m') 615 555 0,454.T(»C) +904,6 0,04.T("C)+153,1 -0,20ST ("O + 2680 *" qi„^,('):,'=hi6n lugc nung c4n tinh toan timg thoi diem nung, [W/m^] o Dieu ki^n ban dau: Tai zH): k— = Taiz=H: k £ = qaii,„j,^i„ + q^,^^ dz c Mo hinh todn cua qud trinh nung cam ung Mo hinh toan eiia qua trinh nung cam ling kim loai ban Idng gdm phin: k ^ = qbic«.i+ qii„,„4,(t) Chung ta se tien hanh toi uu hoa ca hai bai toan gia nhiet va lam nguoi thong qua vi$c - Phuang trinh truyin nhiet - Cac dieu kien bien: Day la su phdi hgp xac dinh G(t) va q{t) Ca hai ham dSu phai thoa gida phuong trinh truyin nhiet, phuong trinh man dieu kien sau: huyen nhipt ddi luu va phuang trinh biic xa q(t) - Cac dieu kign ban dau Phuang trinh truyen nhiet chiSu theo r B^ g'*i quySt bai toan tdi uu tren thi va theo z (r, z: la bien): phuong phap CGM la mot phurnig phap duoc nhom tac gia dS xuit, phuong phap CGM la mgt - mtP^"™? phap lap thuooig Suae cac nha nghi6n "' 'SI CUU ling dung boi vi no khong chi CO tinh hi?u Hay: q^^ cao ma dac trung tu hieu chinh cua 18/ W\ a / aTx ST ''^""'™ phuang phap ma hudng lap g6m gradi-.-.^k(r).r.-j+ ^.[k(I).r.-j + Qjj,„^ = p(T).Cj(D.- ent cua ham muc tieu theo biSn s6, cong them mgt dai lugng dieu chinh dua tren huong lap Vai: truoc, Cu th^: Q MrmnB- *^S"™ •*>?' bcH ttong thict bi tao ra, [W/m=] G""(t)=G«(t)+P"P"(t) Qbi.>„.g = GCt) X e-^