Effect of Cryogenic Treatment of Tool Electrode on the Performance Parameter in Electrical Discharge Machining of JIS443CT - A Review

Transcription

1 Effct of Cryognic Tratmnt of Tool Elctrod on th Pformanc Paramt in Elctrical Discharg Machining of JIS44CT - A Rviw Manoj Ravindra Ahir Rao, Rajndra S. Dalu M. Tch. (Production Engining) Scholar, Govnmnt Collg of Engining, Amravati, Maharashtra, India Prof & Had, Dpartmnt of Mchanical Engining, Govnmnt Collg of Engining, Amravati, Maharashtra, India Abstract Th corrct slction of manufacturing conditions is on of th most important aspcts to tak into considation in th majority of manufacturing procsss particularly, in procsss rlatd to Elctrical Discharg Machining (EDM).Th principl of Elctrical Discharg Machin (EDM) also calld lctro discharg spark osion machining is basd on th osion of mtals by sparks discharg. Mtals ar asy to machin by using non-traditional machining such as Elctric Discharg Machin (EDM). But, during EDM, with th workpic, vn th tool wars out. This tool war is not dsird as it changs th tool gomtry. To ovcom this obstruction, cryognic tratmnt is carrid out for tool matial bfor machining. Th machining formancs of th procss ar concludd in tms of Matial Rmoval Rat (MRR), Tool War Rat (TWR) Surfac Roughnss valus. In this pa, th finding of th litatur rviw on Effct of cryognic tratmnt of tool lctrod on th formanc paramt in EDM has bn prsntd. Indx Tms Elctrical Discharg Machining, Cryognic Tratmnt, MRR, TWR, SR. I. INTRODUCTION Elctrical discharg machining (EDM) is a nonconvntional machining procss is found to b mor conomical during th machining of advancd alloys composit matials. It works on th principl of osion of matial from th work pic with controlld rptitiv sparks producd by th DC puls gnator. Th origin of lctrical discharg machining gos back to 77, whn English scintist Josph Pristly discovd th osiv ffct of lctrical dischargs. In 94, Sovit scintists B. Lazarnko N. Lazarnko had th ida of xploiting th dstructiv ffct of an lctrical discharg dvloping a controlld procss for machining matials that ar conductors of lctricity. With that ida, th EDM procss was born. Th Lazarnkos fctd th lctrical discharg procss, which consistd of a succssion of dischargs mad to tak plac btwn two conductors sparatd from ach oth by a film of non- conducting liquid, calld a dilctric. Th Lazarnkos achivd a form of immortality with this circuit, which today bars thir nam. Today, many EDMs us an advancd vsion of th Lazarnko circuit.. Principl of EDM Elctrical Discharg Machining (EDM) is a controlld mtal-rmoval procss that is usd to rmov mtal by mans of lctric spark osion. In this procss an lctric spark is usd as th cutting tool to cut (od) th workpic to produc th finishd part to th dsird shap. Th mtal-rmoval procss is formd by applying a pulsating (ON/OFF) lctrical charg of high-frquncy currnt through th lctrod to th workpic. This rmovs (ods) vy tiny pics of mtal from th work pic at a controlld rat. Fig.. shows th lctric stup of th Elctric discharg machining. Th tool is mad cathod work pic is anod. Whn th voltag across th gap bcoms sufficintly high it dischargs through th gap in th form of th spark in intval of from of micro sconds. And positiv ions lctrons ar acclatd, producing a discharg channl that bcoms conductiv. It is just at this point whn th spark jumps causing collisions btwn ions IJIRT 4647 INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN TECHNOLOGY 7

2 lctrons crating a channl of plasma. A suddn drop of th lctric rsistanc of th prvious channl allows that currnt dnsity rachs vy high valus producing an incras of ionization th cration of a powful magntic fild. Th momnt spark occurs sufficintly prssur dvlopd btwn work tool as a rsult of which a vy high tmatur is rachd at such high prssur tmatur that som mtal is mltd odd. Such localizd xtrm ris in tmatur lads to matial rmoval. Matial rmoval occurs du to instant vaporization of th matial as wll as du to mlting. Th moltn mtal is not rmovd compltly but only partially. Figur.: Working principl of EDM [] As th potntial diffnc is withdrawn, th plasma channl is no long sustaind. As th plasma channl collaps, it gnats prssur or shock wavs, which vacuats th moltn matial forming a crat of rmovd matial around th sit of th spark. Plasma passag occurring xciting incras of tmatur mak us to rmov matial. Matial rmoval taks plac bcaus of on th spot vaporization of th mtallic particl as wll as owd to mlting procss. Th mltd particl is not withdrawn altogth, howv just partly. By mans of th potntial diffnc is drawn th plasma passag is no long continud. As th plasma passag brakdown, it producs prssur forc or shock wavs, which clars th moltn matial by flushing mthod making a dprssion of rmoving matial all ov th plac of th spark. Cryognic procssing, originally dvlopd for aospac applications, has bn usd for yars to improv th protis of mtals. Many fantastic claims hav bn mad as to th dgr of improvd formanc achivd by cryognic procssing. Practitions claim that protis such as war rsistanc can b improvd by factors of two, thr, or compard to traditional hat tratmnt. Oth claims improvd dimnsional stability, incrasd hardnss or shifts in rsonant vibrational frquncy of cryognically tratd matial. Som claims hav bn validatd by rsarch, many hav not. Howv, th us of cryognic procssing is growing. Cryognic Tratmnt (CT) is th procss of trating matial to cryognic tmaturs in ord to sk nhancd strss rlif stabilization, thby improvd war rsistanc. Th scintific community gnally dfins cryognic tmaturs as tmaturs blow 5 C. Howv, this is, admittdly, an artificial up limit; tmaturs usd prsntly in cryognic tratmnt ar gnally 85 C. CT of tool matial appars favorabl sinc cryognically tratd matial corrsponds to long part lif, improvd fatigu lif (lss failur du to cracking), improvd thmal protis (incras in thmal conductivity), btt lctrical protis including lss lctrical rsistanc (incras in lctrical conductivity), rducd cofficint of friction, lss crp walk, improvd flatnss, asinss of machining. Gnally, th parts can b cryognically tratd ith by (i) Shallow Cryognic Tratmnt (SCT) or by (ii) Dp Cryognic Tratmnt (DCT) (). During cryognic tratmnt th part componnt is immsd into th liquid nitrogn (LN) for spcifid tim duration (). During DCT, th tmatur is gradually rducd to 84 C at a cooling rat of C/min th part componnt is kpt in th cryognic procssor contain for about 4 h durations. Th tmatur is thn gradually raisd to th room tmatur again. Th parts ar thn tmd und similar conditions to incur strss rlif. By conducting th cool-down cycl in gasous nitrogn, tmatur can b controlld accuratly, thmal shocks to th matial ar avoidd... Cryognic Tratmnt (CT) IJIRT 4647 INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN TECHNOLOGY 8

3 Tabl. Normal boiling points of common cryognic fluids Cryogn (K) ( o C) ( o R) ( o F) Mthan Oxygn Nitrogn Hydrogn Fig..: St up for cryognic tratmnt of th tool lctrod... History Cryognics in [] is th scinc of production ffcts of vy low tmaturs. It is clar from th abov dfinition that, in th studis of cryognics lowst tmaturs blow th frzing of wat (o C) to b considd. Howv, Prof. Kamlingh Ons of th Univsity of Lidn in th Nthls first usd th word in 894 to dscrib th art scinc of producing much low tmaturs. H usd th word in rfnc to th liqufaction of mannt gass such as oxygn, nitrogn, hydrogn, hlium. Oxygn had bn liqufid at 8oC. Ov th yars th tm cryognics has gnally bn usd to rf to tmaturs blow approximatly 5oC. According to th laws of thmodynamics, th xists a limit to th lowst tmatur that can b achivd, which is known as absolut zo. Molculs ar in thir lowst, but finit, ngy stat at absolut zo. Absolut zo is th zo of th absolut or thmodynamic tmatur scal. It is qual to 7.5 oc or of. In tms of th Klvin scal th cryognic rgion is oftn considd to b that blow approximatly K (-5oC). Th common mannt gass rfrd to arli chang from gas to liquid at atmosphic prssur at th tmaturs shown in Tabl, calld th normal boiling point (NBP). Such liquids ar known as cryognic liquids or cryogns []. Hlium Absolut zo Untill th nd of 96s, attmpts mad to form CT with th rsults of cracking componnts. Th cryognic tratmnt systm dvlopd by Ed Busch in th lat 96s lat improvd by Pt Paulin with a tmatur fdback control on cooling hating rats allows to form ffctiv crackls. CT until vy low tmaturs subsquntly, th rsarch about CT has bn validatd during th 98s by th first rqust in machin tools [4,5]. Latt with rsarch dvlopmnt, computizd tmatur control systms hav bn dvlopd to gt cracklss cryognic tratd componnts to achiv maximum bnfits [6-9]. NASA ngins w th first to notic th ffcts of cold tmaturs on matials. Thy noticd that many of th mtal parts in th aircraft that had rturnd back from th cold vacuum of spac cam back strong than thy w bfor flight. II. LITERATURE REVIEW Litatur rviw provids th s for th prsnt study. It works as guid to run this analysis. Som survy on rsarch pas rquir to dlibat in this rviw pa connctd towards Elctrical Discharg Machining. From th radings out in ths pas thsis is mostly concnd through th EDM sttings such as th discharg currnt, applid voltag, puls on tim, puls off tim, duty cycl, tc. in what way ths paramt will affct th machining outputs lik MRR, Ra, TWR tc. In this rviw pa sarch fw slctd rsarch pa rlatd to EDM with ffct of mtal MRR, TWR, surfac roughnss (SR) workpic matial, IJIRT 4647 INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN TECHNOLOGY 9

4 w ar broadly classifid all th pa in to fiv diffnt catgory, i.. pa rlatd to matial rlatd workpic or tool, Cryognic tratd lctrod, comparativ study on cryognic tratd nontratd workpic lctrod, som pa rlatd to Effct of multipl discharg rst of th pa rlatd to Cryognic tratd procss.. Matial Rmoval Rat (MRR) Wo rk Elc Y pic trod Aut MRR a hor Mat Mat r ia ial l This pa rports on an ximntal 8 Kup pan Gill Sing h Yild iz t al Inco nl 78 Ti 64 6 by lliu m- p p C- p invstigation of small dp hol drilling of Inconl 78 using th EDM procss Th MRR incrass with th incras in pak currnt, duty factor lctrod spd []. MRR of DCT workpic is lss than th MRR for nontratd workpic for min 6 min drilling tim, but for long durations of drilling (9 min, min, 5 min, 8 min) th trnd is rvsd []. - % incras in matial rmoval rat of cold cryognic tratd workpic. Currnt is th most ffctiv paramt affcting th MRR. In th cas of using tratd work pics, MRR incrasd avagly by about Sriv asta va Pan dy Ah mad Laji s Mat hai V.J.,Vag hla R.V., Dav M grad high sp d stl Inco nl 78. Stai nls s stl (SS 4) p p p 9% with cold tratmnt by about % with cryognic tratmnt according to data mans. It should b notd that MRR diffncs btwn EDM of non-tratd, cold-tratd cryognically tratd B-Cu work pics ar incrasd rmarkably by incrasing working currnt []. MRR incrass with th incras in discharg currnt This could b du to an incras in discharg ngy with incras in discharg currnt, which improvs th rat of mlting vaporation. Also it can b sn that MRR dcrass with th incras in puls-on tim initially but aft a ctain valu of puls-on tim, it incrass []. Thy hav concludd that th pak currnt is th most influnc paramt for achiving high MRR whil for puls duration it shows insignificant for improving MRR [4]. Matial rmoval rat incrass with incras in currnt puls ON tim irrspctiv of th cryognic tratmnt condition applid on th tool [5]. IJIRT 4647 INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN TECHNOLOGY

5 4 5 H.K. Rav al H.K.,An d Ds ai K.P. Sing h Abb as Rag hu Kul win d Din Hig h Car bon Hig h Chr omi um WC 6 WC 9 EN stl H tool stl Grap hit Grap hit p tung stn Som incrmnt is rportd in Matial Rmoval Rat (MRR) in all th thr typs of alloy stls aft cryognic tratmnt but in cas of WC 6, it is comparativly lss affctd []. Thy had conclud that th optimizd paramts for th EDM procss for th graphit lctrod both th work pics in common for MRR ar currnt A, voltag V, duty factor 4, for surfac roughnss ar currnt A, voltag 5V duty factor.significant incras in MRR had bn obsvd on cryognically tratd work pic at most of th lvls MRR incrass with th incras in pak currnt for both lctrod, but MRR is mor with th 5 sh cryognic tungstn (CuW) lctrod as compard with th tungstn lctrod [6]. Cryognic tratd lctrod is Bst In this study, for R.T lctrod, th Cop hani machining rat slowly gaiv incrass. At high Bras lan voltag, larg s discharg taks plac in gasous zon rsulting in impaird matial rmoval [7]. Matial Rmoval rat ar critical paramt in EDM. Sinc cryognic tratd tool has a significant positiv ffct on this paramt, it can b rcommndd that cryognically tratd lctrod givs bst rsult in matial rmoval rat.currnt is th most ffctiv paramt affcting th MRR. Tool War Rat (TWR) Y a r 9 Aut hor Ab dul kar m Wor k pic Mat ial titani um alloy (Ti- 6Al- 4V) El ctr od Ma ti al TWR Thy obsvd that it was possibl to rduc lctrod war ratio up to 7% by lctrod cooling. Th cooling ffct of liquid nitrogn improvs thmal conductivity of th lctrod matials thby minimizing hat trappd in lctrod. As a rsult, mlting vaporization of lctrod matial IJIRT 4647 INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN TECHNOLOGY

6 Ab dul kar m Gill Sin gh titani um alloy (Ti- 6Al- 4V) Ti 646 minimizs, thus, war rat of lctrod is rducd [8]. Thy obsvd that it was possibl to rduc lctrod war ratio up to 7% by lctrod cooling. Th TWR incrass with th currnt puls on tim. It mans that high currnt long puls duration rsults in high TWR. Also, TWR dcrass as puls off-tim incrass from 4μs to 5μs. But as puls offtim incrass to 6μs, a sharp incras is obsvd in th TWR during machining without lctrod cooling as against sharp rduction in th TWR during th EDM with lctrod cooling by liquid nitrogn. Th gap voltag rsultd in a gradual rduction in TWR for th two conditions during EDM procss [9]. Tool war rat of lctrod is lss whn drilling DCT Ti 646 alloy workpic as compar to tool war rat of nontratd tool []. Yil diz Sriv asta va Pan dy Ku mar byl lium - p M grad high sp d stl Inco nl 78 C- TWR was incrasd by about 5% btwn A 5 A working currnts. Howv, th was a dcras about 4% in EWR btwn μsc 8 μsc puls durations Tool war rat w found to b low in ultrasonic assistd cryognically coold lctrod as compard to convntional EDM for th sam st of procss paramts Th shap of th lctrod has also bn masurd it was found that th shap rtntion was btt whn cryognically coold lctrod as compard to convntional EDM procss []. Thy found that both TWR WR ar minimum with th us of cryognically tratd lctrod. This may b du to incras in war rsistanc, hardnss, toughnss, improvmnt in thmal lctric protis of th lctrod aft cryognic tratmnt [].. Whn thmal conductivity incrass, th local tmatur IJIRT 4647 INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN TECHNOLOGY

7 Ah ma d Laji s Mat hai V..,Va gh lar. V.,Da v H.K,Ra val H.K.,A nd Inco nl 78. Stain lss stl (SS 4) ris would b lss du to fast hat conductd to th bulk of th tool thus lss tool war [5]. Thy hav concludd that th long puls duration usd may improv th EWR but affct advsly whn high pak currnt is usd [4]. Whn thmal conductivity incrass, th local tmatur ris would b lss du to fast hat conductd to th bulk of th tool thus lss tool war [5]. 5 R. Tha nig aiv lan Cop Bra ss. Surfac Roughnss (RA) Y a r Auth or Work pic Mat rial Elct rod Mat rial Th cryognic tratd lctrod shows significant improvmnt in TWR. TWR for lctrod is found to incras up to half way in th bginning but thn starts dcrasing with furth incras in voltag. Th cryognic tratd brass lctrod producs low TWR compard with oth lctrods Th cryognic tratd lctrod improvs th TWR by 4 tims compard to lctrod at puls on tim of 5μs, currnt of A voltag of 7V [7] SR Ds ai K.P. Sin gh Ab bas High Carb on High Chro miu m WC 6,W C 9 Gra phit Th bst improvmnt in Tool War (7.%) is rportd by WC 9 followd by HCHCr (47.%) thn WC 6 (.7%) []. 9 Abdu lkar m t al titani um alloy (Ti- 6Al- 4V) p 8% improvmnt in surfac roughnss with cooling by liquid nitrogn. Thy hav also concludd that th currnt puls puls on tim ar most significant paramts which affct to surfac roughnss Th high tmatur during th EDM rducs th thmal conductivity of th IJIRT 4647 INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN TECHNOLOGY

8 Gill Sing h Ti 646 p lctrod matial th hat gnatd during th procss cannot pass asily through th lctrod. This rsults in mlting vaporization of lctrod matial. But during cryognic cooling, th low tmatur of liquid nitrogn cools th lctrod rducs its mlting vaporization rsulting in smooth surfac of th lctrod with a uniformly distributd sparks. This rproducs a btt surfac of th workpic [8] Th roughnss valus for DCT Ti 646 alloy workpic ar lss as compard with th non-tratd workpic on both th bas of th blind hol as wll as sid walls, irrspctiv of th drilling tim. So th surfac finish producd on th DCT Ti 646 alloy workpic is btt than th nontratd workpic. Ovall, Surfac roughnss incrass as w go for long Yildi z t al Sriva stava P y L. Liqi ng, S. Ying ji Math ai V.J., Vagh la R.V., Dav H.K., byll iump r M grad high spd stl Incon l 78. Stainl ss stl (SS 4) C- p p p p durations of drilling for both th work pics []. Surfac roughnss is affctd by currnt puls duration, roughnss incrass with th currnt puls on tim in all th cass. Th diffncs btwn rsults of cold cryognically tratd work pics ar ngligibl []. Surfac roughnss incrass with discharg currnt up to 6 A thn slightly dcrass for all th procsss []. Surfac Roughnss improvmnts w.7% 4% for runs with pak currnts of 9A A no significant ffct of cryognic tratmnt has bn obsvd on improvmnt of surfac quality of th workpic [5] IJIRT 4647 INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN TECHNOLOGY 4

9 Rava l H.K., And Dsai K.P. Sing h Abba s High Carbo n High Chro mium WC 6 WC 9 Grap hit Th bst improvmnt in surfac finish (57.6%) is rportd by WC 6 followd by WC 9 (4.4%) thn HCHCr (4.5%) []. Tool war as wll as surfac finish of th workpic aft machining ar critical paramts in EDM. Sinc cryognic tratmnt has a significant positiv ffct on both ths paramts, it can b rcommndd that cryognically tratd alloy stls can b fficintly machind through EDM III. CONCLUSION From litatur rviw it is undstood that cryognic tratmnt has a significant positiv ffct on th formanc of EDM. Obsvation mad from litatur rviw is as dscrib blow Application of Cryognic tratmnt to EDM is also on of fficint procss for improving th output paramts of EDM procss lik MRR, TWR surfac roughnss It is obsvd that major work has bn concntratd on cryognic tratmnt of tool. Maximum improvmnt is achivd whn cryognic tratmnt is applid for 4 hours. Mostly graphit ar usd as lctrod. Th rviw of litatur indicats that th is limitd publishd work on th ffct of variation in currnt, puls on tim whn cryognic tratmnt is applid to only tool or tool workpic both. This study shall b carrid out in cryognic tratd tool & workpic during EDM. REFERENCES [] Kumar S, Batish A, Singh R, Sing TP. A hybrid Taguchi artificial nural ntworkapproach to prdict surfac roughnss during lctric discharg machining oftitanium alloys. J Mch Sci Tchnol 4;8(7):8 44. [] Patil PI, Tatd RG. Comparison of ffcts of cryognic tratmnt on diffnt typs of stls: a rviw. IJCA procdings on intnational confnc in com-putational intllignc (ICCIA ) ;9: 9. March. [] National Institut of Stards Tchnology, Bould, Colorado Publishd in: Th MacMillan Encyclopdia Of Chmistry, Nw York, [4] Baldissa, P.; Dlprt, C. Effcts of dp cryognic tratmnt on static mchanical protis of 8NiCrMo5 carburizd stl. Matials Dsign 9,, [5] Barron, R.F. Cryognic tratmnt of mtals to improv war rsistanc. Cryognics 98,, [6] Mazur, J. Invstigation of austnit martnsit subjctd to vy low tmaturs. Cryognics 964, 4, 6. [7] Gordon, P.; Cohn, M. Th transformation of rtaind austnit in high spd stl at sub atmosphic tmaturs. Transactions of th ASM 94,, [8] Yaff, M.J. Wid us of cryognic qunching sn. Aviation Wk/Spac Tchnology 967, 86, [9] Nordquist, W.N. Low tmatur tratmnt of mtals. Tooling Production Magazin, 95, 7, 7. [] Kuppan P, Rajadurai A, Narayanan S. Influnc of Edm Procss Paramts in Dp Hol Drilling of Inconl 78. Th Intnational Journal of Advancd Manufacturing Tchnology. 8 Jul ;8(- ):74-84 [] Gill ss, singh j. Effct of dp cryognic tratmnt on machinability of titanium alloy (ti-646) in lctric discharg drilling. Matials manufacturing procsss. may 8;5(6): [] Yildiz y, sundaram mm, rajurkar kp, nalbant m. Th ffcts of cold cryognic IJIRT 4647 INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN TECHNOLOGY 5

10 tratmnts on th machinability of byllium alloy in lctro discharg machining.. [] Srivastava v, py pm. Pformanc valuation of lctrical discharg machining (dm) procss using cryognically coold lctrod. Matials manufacturing procsss. jun ;7(6):68-8. [4] Ahmad s, lajis ma. Elctrical discharg machining (dm) of inconl 78 by using lctrod at high pak currnt puls duration. In iop confnc sis: matials scinc ngining (vol. 5, no., p. 6). Iop publishing. [5] Mathai vj, vaghla rv, dav hk, raval hk, dsai kp. Study of th ffct of cryognic tratmnt of tool lctrods during lctro discharg machining.. [6] Singh k, kumar d. To study th ffct of tungstn cryognic tungstn lctrod on matial rmoval rat during lctrical discharg machining of h tool stl at straight polarity. Intnational journal of mchanical ngining robotics rsarch. 5 jan ;4():4 [7] Thanigaivlan r, arunachalam r, natarajan n. Study on influnc of lctrods in lctric discharg machining. Rcnt patnts on mchanical ngining. 5 aug ;8():6-7. [8] abdulkarm s, khan aa, konnh m. Rducing lctrod war ratio using cryognic cooling during lctrical discharg machining. Th intnational journal of advancd manufacturing tchnology. 9 dc ;45 (- ):46-5. [9] abdulkarm s, ali khan a, konnh m. Cooling ffct on lctrod procss paramts in dm. Matials manufacturing procsss. may 8;5(6):46-6. [] Dhananchzian m, kumar mp. Cryognic turning of th ti 6al 4v alloy with modifid cutting tool insts. Cryognics. jan ;5():4-4. [] Singh o, abbas m. To study th output paramt of non-traditional machining of cryognically tratd work pic.. IJIRT 4647 INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN TECHNOLOGY 6