Machined Surface Integrity In Turning 42CrMo Steel

42CrMo steel has good mechanical properties and mechanical properties,so it is widely used in the field of communication vehicles,aerospace and other equipment manufacturing.As 42CrMo is a difficult to machine material,grinding is usually used for the final finishing of high strength steel.There are many disadvantages in grinding,such as difficult to machine parts with complex shape,low efficiency and using a lot of cutting fluid,etc.Nowadays,due to the development of hard cutting technology,for the final finishing of high strength steel,more and more hard cutting is used to replace grinding.There are many advantages in using hard cutting technology,such as good surface quality,high processing efficiency,"green and clean" and so on.Therefore,this paper aims at turning 42CrMo steel to explore the influence of various factors on the machined surface integrity.The orthogonal experiment was carried out to explore the optimal cutting parameters to obtain good machining surface integrity.The order of significance of the three cutting parameters on the machined surface micro-hardness of 42CrMo steel is feed rate,cutting depth and cutting speed.The influence of cutting parameters,cutting depth and feed rate on the machined surface integrity was investigated by single factor control test.The experimental results show that in order to optimize the machined surface roughness of 42CrMo steel,the larger the cutting speed is,the better.On the premise that the machining efficiency will not be too low,the lower the cutting depth and feed value,the better.The increase of cutting speed,cutting depth and feed rate will lead to the increase of residual stress on the machined surface of 42CrMo steel.The surface residual stress is residual tensile stress.The distribution of residual stress is in the range of 50MPa?350MPa.The results show that when the number of machining steps increases from single to two,the surface roughness presents a downward trend and the surface quality is improved.When the number of machining steps continues to increase to three,the surface roughness increases.The micro-hardness of machined surface decreases first and then increases with the increase of machining steps.The residual stress of machined surface first increases and then decreases with the increase of machining steps.The residual stress of machined surface varies from 100MPa to 350MPa.The influence of different tool wear on the surface integrity was studied by contrast test.The experimental results show that when the cutting speed v=200m/min,the machined surface roughness first decreases,then increases,and finally decreases slightly with the increase of tool wear.When the cutting speed is v=200m/min or v=250m/min,the degree of hardening of the machined surface increases with the increase of tool wear.Based on the theory of material mechanics,mechanical vibration and heat conduction,the variation of cutting force and cutting heat with tool wear is explained theoretically.