Research Of Electropulsing-ultrasonic Machining On 20Cr Steel For Mold

In this paper,a new type of high efficiency and low cost machining process is proposed for the problem of poor surface performance of 20Cr carburized steel mold components.Electrotempering treatment technology is proposed,then the metal surface is treated by electropulsing-assisted turning process?EP-TP?and electropulsing-ultrasonic surface rolling process to improve the surface properties of the metal.First,the electrotempering treatment can make the sample surface temperature rose to 200?within 2min.From the later processing effect,electrotempering technology is expected to replace the traditional tempering process.Thereby greatly improving the heat treatment efficiency.Secondly,the effect of EP-TP on the surface properties of 20Cr carburizing steel was studied.RMS current density of Ra 0.56 A·mm^-2 with a frequency of 500 Hz,the surface roughness reaches the minimum value of Ra 0.88?m,which decreases by 26.7%compared with the ordinary turning process?OD-TP?specimen.The main cutting force is 91 N at the RMS current density of 0.91 A·mm^-2,with a frequency of 500 Hz,which is a reduction of 24.3%compared with the OD-TP specimens.The microhardness reaches the minimum value of 694 HV,which is a decrease of 8.3%compared with the OD-TP specimen.Electropulsing can effectively reduce the degree of tool wear to extend the life of the tool.Current Joule thermal effect and electro-plastic effect together play a role in promoting dislocation movement,enhancing the plastic deformation capacity of the material,releasing the processing stress,making the cutting process more smoothly and improving the processing quality.Finally,the effect of electropulsing-ultrasonic surface rolling process on the strengthening of 20Cr carburizing steel surface was studied.Electropulsing-ultrasonic surface rolling process can significantly improve the hardness of the sample surface and electropulsing can increase the depth of the interaction layer of ultrasonic rolling.Compared with the ultrasonic rolling technology,the depth of the interaction layer of electropulsing-ultrasonic surface rolling process increased from 100?m to near 200?m.The roughness of the surface of the sample treated by electropulsing-ultrasonic surface rolling process was reduced to 0.31?m,which was 74.6%lower than that of the original cutting sample.In the friction-wear test,it can be seen that as the wear distance increases,the wear on the surface of the sample after electropulsing-ultrasonic surface rolling process is the smallest,and the wear coefficient is more stable,indicating that the wear resistance is significantly improved.