Study On Effect Of Grinding 18CrNiMo7-6 Gear Steel In High Speed Grinding On Residual Stress

In recent years,high-speed grinding technology development and research are attentioned and favored for many scholars.High-speed grinding technology of high-efficiency high-quality processing,not only for the defense industry,electricity,railways and other industries to provide difficult processing technology,but also plays an important role in improving the accuracy,reliability and life of mechanical products.In addition,according to the saloman curve,high speed/ultra high speed grinding can cross the hot groove,and reduce the grinding heat incoming workpiece,generated from the grinding area.So as to avoid or reduce the grinding burn of workpiece surface,and to produce residual compressive stress processing surface,and improve the fatigue strength of parts.18CrNiMo7-6 is a raw material for manufacturing important parts such as gears and shafts.It is widely used in aerospace,because of its good mechanical properties and mechanical properties,widely used in aerospace,electricity,petrochemical,machinery and other industries.It is important to study the effect of different high speed grinding parameters on the residual stress and microstructure of the gear material 18CrNiMo7-6,which is of great significance to improve the surface integrity and service life of the workpiece.In this thesis,the relationship between high speed/ultra high speed grinding technology and surface integrity of 18CrNiMo7-6carburized quencher gear steel was discussed,especially focus on residual stress.By designing a reasonable High-speed grinding test program and surface integrity testing program,to obtain the best combination of grinding parameters for the gear surface integrity and research on fatigue life to provide data support.The main contents of this thesis are as follows:(a)Design a single factor experimental program for 18CrNiMo7-6 by using the high-speed grinding process: Grinding parameters in the setting,the wheel speed changes in the range of 60 ~ 160 m/s,table speed of 2 ~ 6m/min,a grinding depth of 10 ~ 50?m.(b)The metal grinding mechanism is studied,and the finite element model of single particle grinding is established.The three-dimensional elasto-plastic finite element method and the Power Law standard model of finite element software are used to simulate and analyze the different effect of cutting speed and cutting depth on residual stress of specimen.(c)The microstructures and grain size of the workpiece after high-speed grinding were studied.The microstructure of the specimen after grinding was composed of tempered martensite,small granular carbide and a small amount of retained austenite.And the core consists of low-carbon martensite and granular bainite.The reason of the change of residual stress is analyzed by the metallographic study,which provides the basis for the indirect analysis of the influence of high speed grinding on the residual stress.(d)The effects of different grinding parameters on the residual stress of 18CrNiMo7-6surface and layer depth are analyzed.The experimental and simulation results show that the influence of grinding wheel speed on residual stress is the biggest,and the depth of grinding and the speed of the table are less.The maximum residual compressive stress is obtained at V_s = 120 m/s.The optimum grinding parameters are:V_s = 120 m /s,V_w = 4m/min,a_p = 0.02 mm.