Research On Machined Surface Integrity And Cutting Parameters Optimization Of Forged Steel Piston

The emission standard of China VI puts forward more stringent requirements on piston material,technology and processing quality of engine pistons.42CrMo steel is widely used in forged steel pistons because of its superior comprehensive properties.In this thesis,by using finite element method and cutting experiment,the influence law of cutting parameters(cutting speed v,feed rate f,cutting depth ap)on the surface integrity,friction and wear properties of the external cylindrical turning and pin hole boring of forged steel piston was studied,and cutting parameters were optimized.Based on ABAQUS software,a two-dimensional cutting simulation model of 42CrMo forged steel piston turning was established,and the single-factor method was used to study the influence law of cutting parameters on cutting force,cutting temperature and residual stress.The effectiveness and accuracy of the simulation model were verified by experiments.The results show that the cutting force increases significantly with the increase off and ap.The trends of surface residual tensile stress and cutting temperature with cutting parameters are basically the same,and both of them increase significantly with the increase of v.The orthogonal turning and boring experiments of 42CrMo steel were carried out,and the influence law of cutting parameters on the surface integrity of forged steel piston turning and pin hole boring were studied.The cutting parameters were optimized with the objective of reducing surface roughness and surface residual tensile stress.The results show that the influence and significance off on the surface roughness are the highest,and the surface roughness increases obviously with the increase off.The influence and significance of v on surface residual stress and work hardening degree are the highest,and both of them increase significantly with the increase of v and f.The heat dissipation and chip removal conditions of the boring hole are poor,as a result,the influence and significance of v on the integrity of the boring surface are greater,the quality of the boring surface is relatively poor.Friction and wear experiments on turning and boring surfaces were carried out,and the influence law of cutting parameters on the friction and wear properties of machining surfaces was studied in combination with the integrity of the machined surfaces.The results show that with the increase of v,the microhardness of the machined surface increases.Proper work hardening is beneficial to reduce the friction coefficient and wear quantity,which improves the wear resistance of the machined surface.with the decrease of f,the roughness of the machined surface decreases,the friction coefficient decreases,and the wear quantity increases.Combined with the influence law of cutting parameters on the surface integrity,friction and wear properties,the optimal cutting parameters for 42CrMo forged steel piston turning are obtained as follows:v=300m/min,f=0.04mm/r,ap=0.1mm.The optimal cutting parameters for pin hole boring are as follows:v=120m/min,f=0.02mm/r,ap=0.05mm.