Research On The Efficient, Low-cost And High Resolution Processing Technology On Metallic Mold Surface

A novel low-cost and highly efficient technology in metallic mold processing is investigated. Electropulsing-assisted cutting processing technology and the surface nanocrystallization layer of 45 steel induced by electropulsing-ultrasonic surface treatment(EUST) are proposed, which improve the surface mechanical properties. We preliminary discuss the mechanism of acceleration of grain refinement and improvement of plasticity by electro-pulse.First, it’s introduced a new special mold steel XGY55 C with improved cutting performance. By further study of cutting temperature, cutting force and tool wear, we analyzed the cutting performance of both the new mold steel XGY55 C and traditional mold steel S50 C. The research result shows that the new mold steel has better cutting performance than traditional mold steel S50 C in following aspects: lower surface temperature of chips, smaller principle cutting force, and less tool wear. Herein, the new mold steel XGY55 C can be used as a better type material for the mold industry.Second, electropulsing is introduced into the cutting process for quenched and tempered 45 steel, which is a novel method to improve the material machinability compared with the conventional cutting process. The effects of electropulsing on cutting performances, microstructure evolution, and surface qualities of 45 steel rods were studied. The results indicate that electropulsing is benefit for the cutting process in 3 aspects as follows:(1) reducing the principal cutting force, surface microhardness and surface roughness of the machined sample dramatically;(2) improving machining efficiency and prolonging the life of cutting tools;(3) decreasing the thickness of rheological layer which was usually caused by work hardening in the cutting process. The morphology and microstructure of the cutting chips showed that the length of the chips increased significantly with the increase of the current density. The advantage of electropulsing is that it can improve the plastic deformation capability as well as increase the lubricating property between specimen and the cutting tool.Finally, the effect of high-energy electropulsing-ultrasonic surface treatment(EUST) on the surface properties and the microstructure evolution of C45E4 steel were investigated. Compared with the ultrasonic surface treatment(UST), the finer microstructure was obtained by EUST. The results of EUST indicate that the impact depth of the surface strengthened layer is increased by 40% to 700 μm. The average grain size of the surface nanocrystallization layer is reduced to 30 ~ 50 nm. The surface roughness of the C45E4 steel is reduced to 0.25 μm, and the surface microhardness is dramatically enhanced to 460 HV. The improvement of microstructure and micro-hardness at ambient temperature is likely attributed to the acceleration of atomic diffusion and the enhancement of plastic deformation ability in the surface strengthened layer under the influence of electropulsing. Due to the electropulsing-assisted ultrasonic strengthening effect, the surface nanocrystallization in this ultrafast procedure is noticeably enhanced.