Tag Archive Introduction of mould making process

Introduction of mould making process

  1. Smelting quality for high-quality die steel, the processes of out of furnace refining, vacuum treatment, vacuum smelting, powder injection treatment and electroslag remelting are widely used at home and abroad to reduce the contents of harmful elements, oxygen, hydrogen and inclusions in the steel and fine tune the chemical composition and pouring temperature. By ESR, the macrostructure and density of the steel can be effectively improved, and the isotropy of the die steel can be improved. The tests in some domestic factories show that the transverse impact toughness of 4Cr5MoSiV1 steel produced by electric arc furnace is only 31% of the longitudinal impact toughness. After ESR, the transverse impact toughness of 4Cr5MoSiV1 steel is 70% of the longitudinal impact toughness, which is more than doubled. For the die steel with special requirements, the P / m high speed steel and P / m high alloy die steel can better improve the microstructure and properties of the steel.
  2. On the basis of a certain forging ratio, upsetting drawing forging and cross rolling should be adopted as far as possible to improve the isotropy of die material. In order to reduce machining allowance and improve material utilization, precision forging machine, fast forging hydraulic press and high-precision continuous rolling mill are widely used to provide high-precision steel to meet the needs of mold manufacturing.
  3. For heat treatment and finishing of forged and rolled products, controlled atmosphere or vacuum heat treatment should be adopted to avoid oxidation and decarburization. Some plastic die steel and hot work die steel should be pre hardened by Metallurgical Department. For some hot working die materials with high requirements, the Metallurgical Department should refine the structure in advance to eliminate the coarse carbides and chain carbides in the steel, and obtain fine and uniform carbides, so as to further improve the various properties of the steel, especially the isotropy. According to some foreign reports, some hot work die steels are produced with high quality and high directivity by electroslag remelting, multi-directional forging (rolling) and microstructural refinement. The transverse impact toughness can be equal to more than 90% of the longitudinal impact toughness. In addition, considering the metallurgical quality of various parts of steel, attention should be paid to make the main working face of the mold (such as cavity or edge) close to the surface of steel; because in general, the surface of steel is the clean part of steel, while the center of steel is the area where the macrodefects are concentrated; especially in the large section ledeburite steel, the center part is the center part The inhomogeneity of eutectic carbide in steel is 2-3 grades higher than that on the surface. In addition, the main load bearing direction of the die should be consistent with the deformation direction of the steel, so as to reduce the adverse effect of the anisotropy of the steel on the die.
  4. Thermal conductivity thermal conductivity is also one of the main performance indicators of die steel, especially some hot work die steel and plastic die steel. Mold steel with good thermal conductivity can quickly transfer the heat generated in the processing and the heat from the workpiece, avoid overheating on the working surface of the mold, and improve the working conditions of the mold. For some thermoplastics forming dies and some die-casting dies, in order to speed up the pace of production, it is hoped that the pressed workpieces can be cooled and demoulded quickly to improve productivity. In order to solve this problem, sometimes some die materials with better thermal conductivity than steel are selected, such as high-strength copper alloy, high-strength aluminum alloy, etc.