Banh Tien Long vd Dig Tap chi KHOA HOC & CONG NGHE 118(04): 157- 162
KHAO SAT C H A T LlTONG B)E MAT KHUON DAP C O M O DONG C O RV125 DU'OC GIA C O N G BANG PHU'ONG PHAP XUNG DIEN
Banh Tien Long', Ngo Circmg^ Nguyen Huu Phan^"' Trudng Dgi hqc Bach ichoa Ha Noi 'Trudng Cao dang Kinh te - Ky thudt - DH Thai Nguyen
TOMTAT
Gia cong bang tia lira dien (EDM) la phuang phap dugc sii dung pho bien de gia cong cac be mat CO hinh dang phuc tap hoac cac Ioai val lieu dan dien c6 do cimg, do ben rat cao. Do phuang phap nay sir dung nang lugng nhiet rat cao dupc tao ra boi cac tia lira dien de boc tach vat lieu nen topography va cau tnic ciia ldp be mat sau gia cong bang EDM khac vdi khi dugc tao ra bang cac phuong phap gia cong truyen thdng. Bai bao nay trinh bay khao sat ve chat luong cua Idp be mat khuon dap co mo dgng co R V I 2 5 dugc lam bang thep SKD6I sau gia cong EDM vdi dien circ Cu va dung dich dien moi la dau qua cac thong so: tri so nhap nho, do cung te vi, cau tnic te vi va su thay doi thanh phan hoa hoc ciia ldp be mat.
Tu khoa: EDM. nhdp nhd be mdt. do cirng le vi lap be mat, cdu mic te vi ldp kim loai he mat.
thdnh phdn hda hoc cua ldp be mgl.
DAT VAN DE
Gia cdng bang tia iua dien (EDM) la phuang phap gia cong khdng truyen thdng dugc iing dyng rpng rai nhat trong nganh gia cdng khudn mau [I]. Phuang phap nay su dung ngudn nang Iugng nhiet cao ciia cac tia lira dien xuat hien trong khe bd gitra phdi va dung cu (dien cue) de lam ndng chay va bay hai val lieu can gia cdng [4]. Lfu diem noi bat ciia phuang phap la gia cdng dugc cac chi tict lam bang cac vat lieu dan dien vdi do ben, dp Cling bit ky va cd hinh dang be mat rat phuc tap nhu: kliudn ren, khudn dap, cac chi tiet trong nganh hang khdng, cac chi tiet chiu tai trpng ldn va nhiet do cao [3]. Cac van de nhu:
rung dpng, iing sual ca hpc, tieng on cung khong xual hien trong sudl qua trinh gia cdng do khdng cd su tiip xiic giiia phdi va dung cu.
Tuy nhien, phuang phap nay ciing tdn tai mot sd nhugc diim nhu: chit Iugng be mat gia cong thap (nhap nhd bi mat Idn, ca ly hda tinh Idp v^t lieu bi mat thay ddi, xuat hien nhiiu vit mil li vi tren bi mat...), nang suat gia cong khdng cao va bi gidi ban ve kha nSng ung dung.
Teh 098378S844
Mdt sd kcl qua nghien ciiu da cbi ra rang ldp be mat ctia chi tiet sau gia cdng bang phuang phap lia lua dien dugc chia thanh nhieu ldp:
Ldp bien trang, Itip trung gian, ldp nen do su tac dpng nhiel ciia cac tia lira dien gay ra [11].
Chat lugng san pham sau gia cdng bang EDM dugc danb gia qua cac dac tmng cua ldp be mat gia cdng nbu nhap nhd, kich thudc va sir phan bd ctia cac vet niit te vi, irng suat du tren ldp be mat [2]. Rat nhicu cac thdng sd cong nghe anh hudng den ldp be mat sau EDM thdi gian xung, cudng do dong dien xung, dien ap xung, su phan cue, vat lieu dien cue, dung dich dien mdi, ndng dp cac hat phoi trong dung mdi va kich tbudc dien cue [3]
Anh budng ciia cac thdng so cdng nghe cd tac ddng rat Idn den kha nang lam viec cua chi liet gia cdng nhu. do ben moi, dp ben an mdn va kha nang cbiu mai mdn [4] Jaharah va cac cpng su da ngbien cim anh hudng ctia cudng dp ddng phdng tia lua dien, thdi gian phal xung va ihdi gian ngirng phat xung den tdc dd mdn dien cue Cu, den ldc do boc tach val lieu va nhap nhd be mat gia cdng ciia thep SKD61 [6] Shabgard va cac cpng su da nghien ciiu ve anh buang ciia cudng do ddng phdng tia lira dicn va thai gian phai xung den cac ihdng sd dac trung ldp be mat gia cdng ciia thep SKD6I (nhap nho be mat, chieu day 157
Banh Tien Long vd Dtg Tap chi KHOA HOC & CONG NGHE 118(04): 157-162 ldp bien trang, chieu sau ldp bj tac ddng nhiet
do) sau EDM vdi dien cue Cu [7]. Boujelbene va cac cgng su da nghien ciiu ve anh hudng ciia cudng do ddng dien xung tmng binh va nang lugng xung den chieu sau, dp ciing, mit te vi, cau tnic va thanh phan hda hpc cua cac Idp tren be mat thep X200Crl5 va 50CrV4 sau EDM vdi 2 loai vat lieu dien cue la Cu va Grafit [5]. Hau het cac nghien cim da cdng bd duac thuc hien trong dieu kien phdng thf nghiem vdi dien cue cd kich thudc nhd, hinh dang be mat dan gian.
Thep SKD61 lit loai thep cd dp ben tiep xuc tot, do ben nhiet tdt va do ciing cao do do dugc sii dung rdng rai de lam cac khudn chiu tac dong cua nhiet dp cao nhu: khudn ren, khudn keo, khudn diic [8] Cu, Cu-W, Gr, W la nhiing loai vat lieu dugc sii dung de lam dien cue do co do dan dicn tdt, dp mdn dien cue nhd va dal duac chat lugng gia cong cao [9], Trong sd cac vat heu tren Ihi hien nay Cu va Gr la hai loai vat lieu duac sir dung pho bien ban ca.
Bai bao nay trinh bay khao sat ve chat lugng be mat khudn dap cd md dgng co RV125 dugc lam bang thep SKD61, gia cong bang EDM vdi dien cue Cu va dung dich dien mdi la dau. Cac thdng sd chat lugng be mat da dugc khao sat gdm. tn sd nhap nhd, do cung te vi, cau tnic te vi va su thay doi thanh phan hda hoc cua Idp be mat Thi nghiem dugc lien hanh tai Cdng ty TNHH Nha nudc mpt thanh vien Diesel Sdng Cdng - Thai Nguyen.
NOl DUNG NGHIEN ClTU Dieu kien thi nghiem Mdy vd sa do thi nghiem
May thi nghiem: May xung dien CNC- EA600L ciia Hang JSEDM-JL\NN MECHINERY & ELECTRIC INDUSTRIAL CO LTD-TAIWAN.
- Sa dd thi nghiem the hien tren Hinh 1, qua trinh phan cue khi gia cong la phan cue thuan (dien cue (-), phdi (+))
Vgt lieu thi nghiem
- Vat lieu phdl la thep SKD61(TC JIS - Nhat Ban), nhiet luyen dat do ciing HRC = (48-^52). Thanh phan hda hpc va cac tinh chit CO, li cua thep SKD61 dugc cho d bang 1 va bang 2
Dong
D * C
•
ch difn moi — L.;
: z : : r ;
vmm~i
- -T-.z:
cJ^ t j Hinh \.Saddgia cong bdng tia lira dien
Bang 1. Thdnh phdn hoa hoc theo % trong lugng ciia thip SKD6}
C Mn Si Cr Mo V P S 0,35 0,40 1,00 5,15 1,3 1,0 <0,03 <0,01
Bang 2, Cdc tinh chdt ca, li cua ihep SKD6I Khoi Nhiet ^ . . . Do Nhiet lu-ong dung • t. Modul dan
do neng neng „ . dan hoi nhiet
"C Kg/d J/kg. 0^•;_;_"••" N/mm' W/m.
•" K '/m
20 7,80 460 500 7.64 550 600 7.6 590
Nhiet do hoa 16I1S 1454°C
0,52 215.10' 24,30 0.86 176.10' 27.70 0,96 165.10' 27.50 Nhiet 46 hoa rjn. 131S'C Vat lieu dien cue la ddng dd (Cu), cac dac tinh cua Cu dugc the hien trong bang 3.
- Hinh dang va kich thudc dien cue dung cu la am ban ciia be mat can gia cdng va dugc mo ta d hinh 2.
Hinh 2. Hinh ddng dien circ dung cu
Banh Tien Long vd Dtg Tap chi KHOA HOC & CONG NGHE 118(04). 1 5 7 - 1 6 2 Bang 3. Dgc tinh ky thudt cua Cu
P § c tinh k ? t h u a t Chi so 1
2 3 4 5 6
D Q dan nhiit (W/m."K) Nhiet dp nong chay (°C) Kh6i lirong ricng cr 20''c (g/Cm') Nhiet do s6i(°C)
Nhiet dung rieng (Cal/g."C) Ha so bien dang nhiet (xlO^C ')
380,7 1083 8,9 2595 0.092 17 Dung dich diin moi
Dung dich dien mdi la d a u bien the ( E L E C C T R O L ) v d i d^c tfnh k y thuat cho d B a n g 4.
Bang 4. Ddc tinh ky thugt ciia ddu biin the
" T T Dac tinh kT thuat Chi so Ty trong a 2 0 X (max) (kg/1) Nhiet do chay coc kin (min) ("C) Nhiet dp dong dac (max) ("C) Dien ap danh thung (min) (KV) Do nhdt dong hoc d 40''C(max) (cST)
He so ton that dien moi (max) 0,89 140 -30 45 16,5 0,005 Cdc thong so cong nghe
Cac thdng sd c d n g n g h e gia c d n g d u g c lay theo so lieu ma C d n g ty T N H H N h a n u d c mpt ihanh vien Diesel S d n g C d n g - Thai N g u y e n dang ap d u n g irong san x u a t ( B a n g 5).
Bang 5. Cdc thong so cong nghg gia cong CuoTig do dong di^n xung 4,5A Thdi gian xung
Thoi gian ngirng xung Dung dich dien moi Phan cue Thai gian gia cong Dien ap khe hd
ISOps 2)AS Dau bien the
Thuaii l h 3 5 ' 5 2 "
45V Phuang phdp ddnh gia
Y)() n h i p nhd hi mat d u g c d o b a n g may do bien dang kiSu dau dd tiep xtic SJ-400 (Hang M I T U T O Y O - J A P A N ) , hinh thai be mat dugc khao sal b§ng each c h u p anh ircn may hian vi dien tii quel J S M 6 4 9 0 ( H a n g J E O L - JAPAN); cau tnic ii vi Idp k i m loai b e m^t dugc khao sat b ^ n g each c h u p anh mat cat ngang ciia hk mat gia c d n g tren may hicn vi quang hgc Axiovcrt 4 0 M A T ( H a n g C A R L ZEISS - G E R M A N ) ; dp c u n g i6 vi i d p b£ m a t
d u g c d o b a n g m a y d o d o ciing te vi Indenta M e t I I 0 6 ( H a n g B U E H L E R - U S A ) . K E T Q U A V A T H A O L U A N
Cdu true vd do cung te vi cdc lap theo mdt cat ngang
D p Cling te vi sau gia c d n g d u g c khao sat theo chieu sau l d p b e mat. T h a n g d o d u a c su dung de do la thang H V 0 , 0 0 5 va do theo p h u a n g v u o n g goc vdi be mat mau vdi tai trgng d a m xuyen la 50 gam.
Lop bien Irang
Hinh 3. Cdu true ldp mdt cdt ngang thep SKD6]
sau EDM (ASTM E407)
Bang 6. Chieu ddy ciia cdc lap be mdt bi thay doi Lop khao sat
Ldp bicn trang
Chieu day (um) Lap chuyen tiep 6.2UI3,33 Bang 7. Dd cimg theo chieu sdu lirp be mat gia cdng Chieu sau
do (^m) Do cimg
(HV) ,13 632.63 652.27 643,30 Ket qua khao sat cau tnic va d o cirng le vi cac ldp theo mat cat ngang (Hinh 3, Bang 6 va Bang 7) cho thay:
- L d p b e mai ctia t h e p S K D 6 I sau gia c o n g tao thanh 3 l d p (Idp bien trang, .ldp trung gian va ldp n e n ) , dp ciing te vi cua cac ldp rat k h a c nhau
- L d p bidn trang la ldp d u a c hinh thanh tir val lieu bl n d n g chay, bay hai ma khdng bi dung dich dien mdi cudn di nen da ket linh Ien be mat gia cdng L d p nay cd chicu day kha ldn (6,21 -^ 24,06) |im, dp c u n g tc vi thap 459,27 H V va xuat hien nhieu vel nirt te vi. Cac dac diem nay da lam do ben mon va dp ben moi ciia be mat khudn giam manh
Banh Tien Long vd Dtg Tap chi KHOA H O C & CONG N G H E 118(04): 157-162 - Ldp trung gian dugc hinh thanh tu vat lieu
bi nung ndng den trang thai bien doi cau tnic va pha. Ldp nay cd chieu day nhd han Idp bien trang nhimg do ciing te vi cao han vat lieu nen kha nhieu 648.13HV va xuat hien it nut te vi, vi vay cd anh hudng tdt den kha nang Iam viec cua khudn dap.
Thdnh phan hoa hoc ciia l&p be mat Ket qua phan tich thanh phan hda hpc d ldp be mat (ldp bien trang) ciia thep SKD61 sau gia cdng bang EDM cho d Bang 8 va Hinh 6.
Bang 8. Thdnh phdn hda hgc cua bien trdng Thanh
p h i n C Mn Si V Cl Mo Cu
Trirffc gia c6nfi (%)
0,40 0,47 0,98 0.83 4,89 1,15 0.00
Sau gia cong 13,76
(%)
0.4 1.00 0.80 5,15 1.40 0,32
- Ham lugng C trong ldp be mat tang len la do diu bien the dudi tac dgng ciia tia liia dien da bi cracking tao ra cac bon xam nhap vao.
Hinh 4 chi ra rang nguyeo td C xam nhap vao ldp be mat phoi ton tai dudi dang cacbit Fe7C3 va mac ten xit FcjC. Tuy nhien do ciing ciia ldp be mat van thap ban ldp nen, dieu nay dugc giai thich la do td chiic ldp nay cd cau tao dang xdp.
Nhdp nho va hinh thdi be mat gia cong: , - Nhdp nho be mat
Ket qua do (vdi chieu dai chuan do la Smm, sd lan lap la 3 lan tren moi mau thi nghiem, ket qua la gia tri trung binh cgng cua 3 lan do):Rz= (21,83 ^31,36) Jim.
Vdi yeu cau ky thuat cua be mat khuon dap phai cd tri sd nhap nhd Ra = 0,63p.m thi sau gia cdng bang EDM can cd them phucmg
phap gia cdng tinh bd sung. ^ - Hinh thdi be mat gia cong ^,,
Hinh 4, To chuc cdc pha hinh thdnh tren bi mat gia cdng Bang 8 cho thay:
- Thanh phan hda hpc Idp be mat ciia thep SKD6I da thay ddi dang ke sau gia cdng:
xuat hien nguyen td Cu (0,32%) va ham lugng C tang Ien rit ldn (8.84% -;- 15.18%).
- Sir cd mat cua nguyen td Cu trong ldp be mat la do vat lieu dien cue (Cu) trong qua trinh xung da bi tac ddng nhict ciia tia lua dien lam ndng chay va bay hai xam nhap vao.
Hinh 5. Anh be mgt phoi sau EDM a) Hinh thdi be mat gia cong b) Hinh dang cdc hat tren be mat
160
Banh Ticn Long vd Dtg Tap chi KHOA HOC & CONG NGHE 118(04)- 157-162 Ket qua d Hinh 5 cho diay:
- Be mat sau gia cdng la tap hgp cac vit ldm va nhieu hat hinh cSu bam dinh tren hk mat, day la 2 yeu to tao ra do nhin hi mat gia cdng thap
- Dudng kinh, chieu sau va su phan tan cac vet ldm khdng deu ma nguyen nhan la do tia Ilia dien dugc tao ra trong qua trinh xung khdng lien tuc va nang Iugng cua cac tia khdng deu.
- Trong qua trinh xung mgt phan vat lieu ciia dien cue va ciia phdi bi ndng chay, bay hai ddng thdi bi dung dich dien mdi lam ngugi nhanh va tao ra sue cang mat ngoai nen hinh thanh cac hat hinh cau. Cac hat nay khdng dugc dung dich dien mdi cudn di ma bam dinh tren be mat gia cdng.
a) b) Hinh 6. Anh cdc vit nirl ti vi tren be mat phdi a) Anh phdn bo vet nirt trin be mat gia cong b) Chieu sdu cua cdc vel nut tren lap bi mdt Hinh 4 cho thdy:
- Tren be mat gia cdng xuat hien nhieu vet nurt li vi vdi mat do ldn (Hinh 6a), cd chieu sau phat trien theo hudng vudng gdc vdi be mat gia cong va xap xi bang chieu day idp bien
trang (Hinh 6b). Day la dang khuyet tat cd anh hudng khdng tdt den do ben mdn va do ben mdi cua khudn.
- Cac vet te vi mil xuat hien la do nang lugng nhiet cua cac tia lua dien khi gia cdng lam ldp be mat phdi bi nung ndng tdi nhiet dp rat cao va dugc lam ngupi nhanh bdi dung dich dien mdi.
KET LUAN
Mdt sd nhan xet dugc nit ra tir ket qua khao sat chat lugng ldp be mat khuon dap cd md dpng ca RV125 lam bang thep SKD61, gia cong bang EDM vdi dien cue Cu va dung dich dien mdi la dau:
- Ldp bten trang la ldp ngoai cung, d Idp nay ton tai nhieu vet mil te vi, co dp ciing nhd han ldp tnmg gian va Idp nen nen day la Idp se anh hudng khong tot den klia nang lam viec cua khudn. Vi vay sau khi gia cong bang lia lita dien can linh loan Iugng du hgp ly de nguyen cdng gia cong tinh tiep theo dam bao lay di loan bd ldp bien trang tren be mat khudn
- Bi mat gia cdng co tn sd nhap nho ldn, xuat hien nhieu vet mil te vi cd nguyen nhan tir viec chgn gia tri cac thong sd cong nghe chua hgp ly [11], vi vay can cd nhirng nghien ciiu tiep tbeo dc tim ra tri sd cac thdng so cdng nghe hgp ly hoac tdi uu.
- Val lieu dien cue Cu xam nhap vao be mat gia cdng tao ra ca sd dc tiep tuc nghien ciru ung dung phuang phap EDM trong cdng nghe phu be mat nham nang cao chat luang be mat bang each su dung cac loai val lieu dac biet (TiC,WC,Ti ..).
Banh Tien Long vd Dtg Tap chi KHOA HOC & CONG N G H E 118(04): 1 5 7 - 162 T A I L I E U T H A M K H A O
[1]. F. L. Amorim, W. L. Weingaertner, Die- Sinking Electrical Discharge Machining of a High-Strength Copper - Based Alloy for Injection Molds, Technical Editor. Alisson Rocha Machado (2004).P.I37-144.
[2]. Bu"lent Ekmekci. Residual stresses and white layer in electric discharge machining(EDM), Applied Surface Science 253 (2007). P. 9 2 3 4 - 9240
[3]. H.T. Lee, F.C. Hsu, T Y. Tai, Study of surface integrity using the small area EDM process wilh a copper tungsten electrode. Mater Sci. Eng, A364(2004), P. 346-356 -»
[4] C A . Huang, F.Y. Hsu, S.J. Yao, Microstructure analysis of the marlensilic stainless steel surface fine-cut by the wire electrode discharge machining (WEDM), Mater.
Sci. Eng. A371 (2004), P. 119-126.
[5]. M Boujelbene, E. Bayraktar, W. Tebni, S.
Ben Salem, Influence of machining parameters on the surface integrity in electrical discharge machining. Archives of Materials Science and Engineering, Volume 37(2009), P.l 10-116.
[6] A.G. Jaharah, C G. Liang, S.Z. Wahid, M.N.
Ab Rahman, C H. Che Hassan, Performance of S U M M A R Y
I N V E S T I G A T I O N O F S U R F A C E P E R F O R M A N C E O F T H E R O C K E R D I E M O L D R V 1 2 5 ES E L E C T R I C A L D I S C H A R G E M A C H I N I N G
Banh Tien L o n g ' , Ngo Cuong^, Nguyen H u u Phan^*
'Hanoi University of Science and Technology. Hanoi, Vietnam , 'College of Economics and Technology • TNU Electrical discharge machining (EDM) is a well-established non-conventional machining process, used for manufacturing geometrically complex or hard and electrically conductive materia! parts thai are extremely di fficult-to-cut by other conventional machining processes. In EDM, the mechanism for removing material primarily mms electrical energy into thermal energy through a series of successive sparks between the electrode and the work piece in a dielectnc fluid. Therefore topography and microstracture of an EOMed surface is complex and generally differs markedly from that lo produce by conventional machining processes. This article presents the result ofthe investigation of surface performance of rocker die mold of the SKD61 hot work tool steel (surface roughness, surface microscopic hardness, microscopic structure of the surface layer, chemical composition of the surface layer) after electrical discharge machining with Cu electrode in oil dielectric
Key words: EDM, surface roughness, microscopic hardness, microscopic structure, chemical composition, dielectric.
Ngdynluiuhar 13/3/2014. Ngdy phdn bien- 15/3/2014. Ngdy duyet ddng: 25/3/2014 Phdn bien khoa hoc: PGS TS VU Ngoc Pi - Tnrdng DH Ky thugt Cong nghiep - DH Thdi Nguyen
copper electrode in electical discharge machining (EDM) of AISI HI 3 harden steel. International Joumal of Mechanical and materials engineering (UMME), Vol3(2008), N o . l , P. 25-29.
[7]. M.R. Shabgard, M. Seyedzawar, S. Nadimi Bavil Oliaei, Influence of input parameters on characteristics of EDM process. Journal of Mechanical engineering Volume.
[8]. K.H. Ho, S.T. Newman, State of the art electrical discharge machining (EDM), Intemational Joumal of Machine Tools &
Manufacture, 43 (2003), P. 1287-1300. "^
[9]. J.P.Kruth, L. Stevens, L. Froyen, B. Lauwers, Sludy on the while layer of a surface machined by die-sinking electro-discharge machining, Annalsofthe CIRP, 44(1995), P. 169-172.
[10], L. C. Lee, L. C. Lim, V. Naryanan, V. C.
Venkatesh. Quantification of surface damage of tool steels after EDM, Intemational Joumal of Machinery Tools &Manufacture, 28 (1987), P 359-372.
[11]. Sanjeev Kumar, Rupinder Singh, T.P. Singh, B.L. Sethi, Surface modification by electrical discharge machining: A review, Joumal of Materials Processing Technology, 209 (2009), P.
3675-3687.
Tel- 09S37S3SH 162
