Metallographic structure: tempered martensite + carbides + retained austenite, in which the content of retained austenite is large, the size of carbides is uneven, and some particles are larger, and the large carbides also have edges and corners. Cr12MoV steel belongs to ledeburite steel. Although the large eutectic carbon compounds have been crushed during forging, the particles are still large and unevenly distributed. These coarse and angular carbides reduce the strength and strength of the punch. toughness. When the punch is subjected to a relatively high load during work, fatigue cracks are easily generated at the junction between the corners of the block carbide and the matrix, and develop upward along the longitudinal direction. It can be seen that the early failure of the punch is mainly fatigue fracture, and fatigue fracture The source of fatigue is mainly at the junction between the edge part and the middle part of the carbide and the matrix. Only through the forging process and heat treatment process to change the shape of the bulk eutectic carbide to improve the strength and toughness of steel. In addition, there is more retained austenite in the structure after quenching and tempering, and its content is about 30% or more, which makes the mold hardness insufficient and wear resistance insufficient. Because the punch for punching silicon steel sheet requires a sharp cutting edge, once the cutting edge is blunt during the punching process, the punched hole will produce burrs, so the punch has a slightly obtuse angle during use and must be sharpened. The length of the punch is shortened while the blade is being sharpened. When the length of the punch is reduced to a certain extent, it is scrapped, so the life of the mold is not long.
