Study On The Surface Integrity Of 18CrNiMo7-6 Steel In Hard Turning

The rapid development of superhard materials makes hard cutting as a new processing method known to people.Its main processing object is hard to process materials such as hardened steel.Compared with precision grinding technology,hard cutting technology has the advantages of high efficiency low cost,strong environmental protection,and has a broad development prospect in practical application.As an important index of surface integrity system,surface roughness and surface residual stress have a great influence on the fatigue life of workpieces,so it is of great significance to study the influence of cutting variables on surface roughness and surface residual stress in hard turning.In this paper,the influence of cutting variables on residual stress and cutting force is explored by simulating the process of turning 18crnimo7-6 carburizing steel with CBN tool in hard state.The single factor process test of hard state turning is designed,and the influence of cutting variables on three-dimensional surface roughness parameters S_a,S_z,S_q,S_sk and S_kuis studied.The distribution of residual stress along the depth direction and the table of cutting variables are determined The influence rule of the maximum residual stress.The results are as follows:?1?Based on metal cutting finite element software Advant Edge FEM is used to simulate the hard turning process.The results show that:the maximum residual stress on the surface of the machined part increases with the increase of the feed rate,first increases with the increase of the cutting speed and then maintains stability,and the influence of the cutting depth on it is small;the main cutting force increases with the increase of the feed rate,first decreases and then maintains stability,and then increases in proportion with the increase of the cutting depth;back The change trend of the direction force with the cutting variable is consistent with the main cutting force.?2?The results of three-dimensional surface roughness analysis show that t he cutting variables have great influence on S_a,but have little influence on S_z,S_q,S_sk and S_ku;S_a increases with the increase of feed speed;S_a has no obvio us regularity with the increase of cutting speed and back draft;when v_c=31m/min,a_p=0.10mm,v_f=5mm/min,the minimum S_a is 0.16?m.?3?In hard turning process,residual compressive stress can be introduced into the workpiece.The residual stress increases to the maximum value along the depth direction,and then gradually decreases to the stable value.The maximum residual stress is in the depth range of 0?30?m from the surface,and the maximum residual stress first decreases and then increases with the increase of the feed speed;when the cutting speed is low,the maximum residual stress increases rapidly with the increase of the cutting speed;when the cutting speed is greater than 39m/min,the stress value tends to be stable;the maximum residual stress remains stable with the change of the back draft,when v_c=31m/min,a_p=0.10mm,v_f=5mm/min,the maximum residual stress is-671.22MPa.