| At present,China's high-end equipment manufacturing technology is far from the advanced level of foreign countries.About 80%of high-end key parts are imported,which seriously affects the development of China's high-end equipment industry.To change this phenomenon and solve the stuck neck problem,it is necessary to eliminate the existing"forming"manufacturing,surpass the surface integrity manufacturing,innovate anti-fatigue manufacturing theories and technologies,and quickly realize technology promotion and application in manufacturing enterprises.Grinding is the last process of precision machining,which can not only ensure the required dimensional accuracy of the workpiece,but also obtain better surface integrity.The surface integrity of the workpiece mainly includes several aspects such as surface morphology,surface residual stress,surface hardness and microstructure,which are the basis for evaluating the fatigue-resistant manufacturing process.However,if the inherent grinding temperature during grinding is not controlled,it will lead to rapid wear of the grinding micro-edge and inaccurate dimensional accuracy of the workpiece,especially when the temperature exceeds a certain critical value,the surface of the workpiece will appear residual tensile stress,surface hardness reduction,and so on,the results directly affect the performance of the workpiece.Therefore,studying the grinding temperature and the surface integrity of the workpiece during the grinding process is of great significance for achieving high surface integrity grinding.18CrNiMo7-6 alloy steel has good mechanical properties and mechanical properties after carburizing and quenching,and is widely used in high-end equipment industries such as aviation,shipbuilding,and high-speed rail.In this thesis,the dry cylindrical plunge grinding test method is used to explore the influence of grinding parameters on the grinding temperature and surface integrity(mainly surface residual stress)of 18CrNiMo7-6 carburized and quenched steel.The main research content and conclusions are as follows:(1)The infrared thermal imager was used to measure the temperature.The test plan for measuring the emissivity value of the sample surface is designed,and the emissivity value of the workpiece surface during the grinding test is determined to be0.1.(2)Designed a single-factor test plan for 18CrNiMo7-6 dry cylindrical plunge grinding:in the dry grinding process,the transverse feed per revolution of the workpiece has a great influence on the grinding force and grinding temperature,while the workpiece speed has a small influence on them.The grinding temperature is related to the tangential grinding force.With the increase of the transverse feed,the tangential grinding force increases,and the temperature of the workpiece surface rises rapidly at first and then increases slowly.(3)The relationship among grinding parameters,grinding force,grinding temperature and surface residual stress was studied and analyzed.Grinding force and grinding temperature play opposite roles in the process of residual stress formation.Grinding temperature is the main factor of surface residual tensile stress.There is a temperature threshold during grinding,and when the workpiece temperature exceeds this threshold(about 340°C),residual tensile stresses will occur on the surface.The higher the temperature,the greater the residual tensile stress.(4)Dry grinding can be used for small-feed finishing(v_s=32 m/s,_wn=80 r/min,f_r?0.2 mm/min),which can not only introduce residual compressive stress on the surface of the workpiece,but also obtain a lower surface roughness value,and has a small effect on the hardness of the surface. |
PDF Full Text Request