Study On The Cutting And Disrepair Mechanism Of The Difficult-To-Machine Material 3Cr-1Mo-1/4V Steel

This paper studies the difficult-to-machine problem of the cutting tools which cuts the main part of the large chemical engineering equipment high-pressure hot wall hydro-processing reactor—cylinder materials (3Cr-1Mo-1/4V steel). It is a subtask of the research, which is financial supported by Key Research Fund of Heilongjiang Province of China. Because this material has super toughness, high heat intensity and the heat resistance, during the spot machining, the chip breaking is difficult, cutting tools adhere fracture down badly and the machining efficiency is low.In order to deal with the adhering and fracture of cutting tools, based on combining lab and spot experiment, we study on the selection of the cutting tools material and the adhering and fracture mechanism of the cutting tools which were used to cut 3Cr-1Mo-4V steel.A group of contrast cutting experiment for different types of hard alloy cutting tools of which discontinuous cutting the 3Cr-1Mo-1/4V steel was done. By comparing the adhering fracture outline and the size of fracture range, tools materials adapted to cut such workpiece materials was optimized. Based on the first selected 12 kinds of hard alloy cutting tools, many optimization experiments of the insert materials were done. At last the YG546 and M2 were deemed to the best materials to cut such workpiece materials.Using SEM, we have observed the low and high multiple adhering fracture outline on the surface of the hard alloy cutting tools and analyzed its microstructure and composition after the cutting experiment. The adhere fracture mechanism of cutting tools in the process of discontinuous cutting was studied. We found that bigcutting force, high cutting temperature and the interaction between the Fe, Cr, Mo of the workpiece materials elements and hard alloy adhering element Co are the most key factor when the hard alloy cutting tools cuts 3Cr-lMo-l/4V steel, so the serious adhering phenomena occur. In fact the cause of adhere mechanism is the diffusion between the elements of the cutter and workpiece as well as the re-crystallization.Otherwise, the diffusion of atoms and subsurface fracture can influence the adhering fracture in a certain condition.In order to prevent the adhering fracture of hard alloy tools in the cutting process, we can improve the cutting behavior and avoid the adhering temperature, select the cutters with coat and grooves, and select cutters with super-fine grains materials. So to improve the capability of the cutter, reduce the adhering fracture, prolong the cutter life, and improve the produce efficiency.