Research On Mechanism Of Ultra-high Speed Milling Of Hardened Steel

Hardened steel is widely applied in manufacture of the die and mould because of its remarkable advantage of good wear resistance and long life.But it is the high hardness and intensity of hardened steel that gives cause for low productivity,speedy wear of tool and high cost of its traditional machining,so it is not more applied.Ultra-high speed milling(UHSM) is a kind of advanced manufacturing technique with high productivity and accuracy.Traditional machining process of hardened steel is rough machining - semi-finishing - heat treatment - grinding.As compared with it,advantage of UHSM of hardened steel is obvious.The developed countries have made much progress in researching on mechanism of UHSM and application of UHSM technique.The ultra-high speed milling machine and machining center has successfully be applied for industrial production.However,our progress is comparatively laggard in this field,So we must work more hard to promote our progress in researching on mechanism of UHSM and application of UHSM technique.Following experimental scheme is used in our study.â‘ Cutter:carbide ball nose endmill.â‘¡Milling mode:down milling,without cutting fluids.â‘¢Cutting condition:spindle speed(10000-24000rpm),the depth of cut(0.01-0.1mm), the feed(0.1-0.15mm/r).â‘£Workpiece material:Hardened Cr12 steel(HRC63-64).In this paper by means of large numbers of experiments we makes scientific researches on influence of cutting condition(cutting speed,the depth of cut and the feed) on cutting force when ultra-high speed milling hardened Cr12 steel.The empirical formula of cutting force when ultra-high speed milling hardened Cr12 steel is established on the basis of experimental data.Influence of single cutting parameter on workpiece surface roughness is analyzed,and by means of the orthogonal test method influence degree of diverse cutting parameters on the workpiece surface roughness is compared.According to new phenomenon of chip our opinion on chip formation mechanism when ultra-high speed milling hardened Cr12 steel is put forward.The following conclusion can be drawn from the study of this paper:â‘ Lesser cutting force and lower workpiece surface roughness is notable advantage of ultra high-speed milling hardened steel,but the reasonable cutting condition must be chosen according to the practice engineering condition to proportion productivity to cost on the premise of ensuring the surface quality.â‘¡When Ultra-high speed milling hardened steel the macrostructure of chip is very small granule,but the microstructure of chip is sawtooth from the Scanning Electricity Microscope(SEM) photo whose teeth space(the width of Adiabatic Shear Bond) is relative to cutting condition(cutting speed,the depth of cut and the feed),which indicates that sudden change of local stress within chip causes plasticity deformation of cut layer metal that is mainly shearing slippage.This is the typical adiabatic shear.This paper is worthy for researching of UHSM mechanism and application of UHSM technique.