Effects of high pressure coolant on machinability of steels

Abstract

I-ligh production machining aLhigil culling speed and iCed rate generates lurge heat and high culling lemperature. which shortens the tool life and deteriorate, tile job qllality. Thi" problem becomes more aelile wh~n thcjob; nrc difficllh to macbin~ and arc to be lIsed under Jynamic loadillg. The conventional culling fluids nrc not that effcctive in ,uch high production machining parlicularly in continuous cultlng of mutcrials Iikc stcels. Further lhe convcntional culling fluids ure nol ~nvironll1entally friendly. The di,po~al of lhc culling tluid; oli.cn lead; LOlocal water pollution and soil contaminution. Recycling and rcu,e of convcntional cutting l1uids also lcad to otbcr problem,. M~cbining of sof\. ,t,cky ~lld dllctil~ l1l~lC";"I,yidd, long conllllUOUScbips and rapid tool wear due 10 inctrLcLcnl action of lh~ CUllingl1ui<l,.In lhe pre,cnl decade, with il1er~asedcnvironmental awareness, the re,carchcrs are striving to devclop environment fricndly machining tcchnology; one such t~chnology is to u,c cutling oil wilh high-pressure. The bCl1er,t,of reduction in macbining tcmperatllfe arc significant rcduction in culling force and Iced force. The b~nct,ts of high-presslIre coolant are dcpend~nt on tbc proeess paramcter, and the tool g~ometry. 'I'be rolc of application of high-pressure eool~nt jet on machinabilily of three dilkrcnt steels (C-60 ;ted, 17CI'NiMo6 slcel and 42CrM04 \!ecl) by two different uncoated earbide i",crt; (SNMG 120408 and SNMM 120408) have been extensively ,tudied in lenm of mechanics and mechanism or chip formation, c\ming zone temperature, pattern and extent ofwol wear and it, growth "ith m~ehinlJlg time "long with l11~chihed sUl'fa~equality in eompOfl.wnto dry and wetlllaehining. xX A high-pr~ssur~ coolant jd wns impinged Gil the rake face of the cutting tool through a "pecL,II)' dcsigned and devcloped noulc. Application of high_pre»ure coolunt jet showed significant effect on chip formation, culling zone temperature and clLuing forces. Expectedl)', compared to dry and wet machining, 1001 "ear under high-pres;UI'c coolant Inachining dccrcascd, c,pccialiy under moderate cutting 8peed-fced comhimtion through ~Qntrol Qf ClLttingzone lcmpemlUl'c, cutting fOl'ccs, favorable chip-tool intcraction and retcmioll of cutting edge ,harpncss. S.,M studics of thc worn out ins~rts revcaled that th~ nOlching and grooVing, Wll;ch are vcry detrimental and may caW,e prcmature and catastrophic faillLre of the culling tools, are remarkably reduced by high-pressurc coolant jet. The present high-pre >sure coolant ;ystem increa,ed tool life by 30% to 75% whcn turning C-60 steel by SNMG in;CI't and 80% to 140% when machining by SNMM insert, Tile suri'ace qU"lity of the machined ,urfa~e imprQvcd po"ibly duc to 1e1o,crdumage of the C11(!ingtool no,e. In ordcr to implemcnt the high-pressure cQo[ant machining technology, an analyticalmodd for cutting temperature has been developed. It is fmmd that ac~orJing to the ,elccted cutting condilions in the model-bascd comparisons, the prcdicted cutting tcmperalllrc under high pressure coolant conditions is rcduccd as higb as about 18% eomp~red with tho"~ in dJ)' culling.