Study On The High-speed Milling Experiment And Parameter Optimization Of Hardened Die Steel Cr12MoV

Hardened die steel Cr12 Mo V(60HRC)is widely used in automobile die manufacturing because of its strong wear resistance and good hardenability.However,in the process of milling,there are some problems,such as large milling force,high milling temperature,easy tool wear and breakage,and the quality of machining is not easy to guarantee.In order to provide theoretical guidance for production practice,it is necessary to further study the cutting mechanism and parameter optimization.In this paper,based on the high speed milling experiment and parameter optimization of hardened die steel Cr12 Mo V(60HRC),the change of cutting deformation,cutting force,cutting temperature and surface quality with cutting parameters were analyzed,and the optimized process parameters were given.The main contents and conclusions are as follows:(1)The formation mechanism and change of saw-tooth chip were analyzed.The formation mechanism of saw-tooth chip and the change rule of chip shape with cutting parameters were analyzed according to the observation results of super field microscope and metallographic microscope.The saw-tooth degree,saw-tooth spacing and saw-tooth frequency are quantitatively analyzed,and the empirical formula of saw-tooth degree is fitted.The results showed that the saw-tooth chip was caused by adiabatic shear.With the increase of milling speed and feed rate per tooth,the degree of saw-tooth gradually increases.With the increase of milling speed and feed rate per tooth,the saw-tooth spacing increases gradually.With the increase of milling speed,the saw-tooth frequency increases,while with the increase of feed rate per tooth,the saw-tooth frequency decreases.(2)The average cutting force and its frequency spectrum were analyzed.The law of milling force changing with milling parameters is studied.The spectrum of milling force is drawn by fourier transform and compared with saw-tooth frequency.The empirical formula of milling force is established by quadratic response surface method.The results show that the milling force decreases with the increase of milling speed and increases with the increase of feed per tooth and milling depth.Through the analysis of milling force spectrum,it is found that the trend of saw-tooth frequency in high-speed milling is the same as that of milling force frequency,which indicates that saw-tooth chip is a main factor causing milling force fluctuation.The error of the formula is smaller than that of the actual value,and the formula is effective.(3)The milling temperature was studied.The law of milling temperature changing with milling parameters was studied.The empirical formula of milling temperature is established by quadratic response surface method,which is verified by comparison with experimental results.The results show that the milling temperature increases with the increase of milling speed,feed per tooth and milling depth.The fitting result of the empirical formula was good,which meets the actual needs of the project.(4)The surface roughness was measured and analyzed.The variation law of surface roughness with milling parameters is studied.The empirical formula of surface roughness is established by quadratic response surface method and verified.The results show that the surface roughness decreases with the increase of milling speed and increases with the increase of feed per tooth and milling depth.The maximum error of the empirical formula was 11%,which could meet the needs of practical engineering.(5)The optimization of milling parameters was studied.The milling speed,feed per tooth and milling depth were taken as the optimization variables.The minimum milling force,minimum milling temperature,minimum surface roughness and minimum saw-tooth degree were taken as optimization objective.The multi-objective optimization of milling parameters was carried out by genetic algorithm,and the optimized milling parameters were given.