With the development of science and technology in recent years, the technical application of the mold industry is also constantly improving. Mold companies have been focusing on the research of ways to improve the metallurgical quality of die steel. After years of hard work and exploration, at present, major metallurgical production departments at home and abroad are committed to improving the metallurgical quality of die steel mainly in the following aspects:

　　1. Smelting quality For high-quality mold steel, external refining, vacuum treatment, vacuum smelting, powder spraying treatment, electroslag remelting and other processes are widely used at home and abroad to reduce the harmful elements, oxygen, hydrogen and inclusions in the steel. Content, fine-tuning of chemical composition and pouring temperature. Electroslag remelting can also effectively improve the low-magnification structure and density of steel, and improve the isotropy of mold steel. The tests of some domestic manufacturers show that the transverse impact toughness value of 4Cr5MoSiV1 steel produced by electric arc furnace is only equivalent to 31% of the longitudinal direction, and the transverse impact toughness value of 4Cr5MoSiV1 steel after electroslag remelting can be equivalent to 70% of the longitudinal direction. Improve more than 1 times. For mold steel with special requirements, powder high-speed steel and powder high-alloy mold steel produced by powder metallurgy process can better improve the structure and performance of steel.

　　2. Forging and rolling process On the basis of ensuring a certain forging ratio, upsetting-extending forging and cross-rolling processes are adopted as much as possible to improve the isotropy of the mold material. In order to reduce the machining allowance and improve the utilization rate of materials, precision forging machines, fast forging hydraulic presses, and high-precision continuous rolling mills are widely used in production to provide high-precision steel materials to meet the needs of mold manufacturing.

　　3. Heat treatment and finishing heat treatment of forged and rolled materials should adopt controlled atmosphere or vacuum heat treatment to avoid oxidation and decarburization. Some plastic mold steels and hot work mold steels should be pre-hardened by the metallurgical department. For some demanding hot work die materials, the metallurgical department should carry out microstructure refinement treatment in advance to eliminate coarse carbides and chain-like distributed carbides in the steel, and obtain fine and uniformly distributed carbide structures to further improve the steel. Various properties, especially isotropy. According to some foreign reports, some hot work die steels are processed through electroslag remelting-multidirectional forging (rolling)-microstructure refinement to produce high-quality and high-isotropic die steels, and their transverse impact toughness values ​​can be comparable More than 90% in the vertical direction. Many steel mills have named trade names for the steel produced by this process, such as ISODISC of Austria Bole Steel Works; ISOTROPY of Japan Hitachi Metals Corporation, MICROFINE of Japan High Frequency Steel Corporation, etc. Many metallurgical production departments in my country are also working on this work. In addition, considering the metallurgical quality of each part of the steel, when manufacturing the mold, attention should be paid to make the main working surface of the mold (such as the cavity or blade) close to the surface of the steel; because in general, the surface of the steel is a relatively clean part of the steel , and the center of the steel is the area where the low-magnification defects of the steel are relatively concentrated; especially in the large-section ledeburite steel, the eutectic carbide inhomogeneity of the central part of the steel will be 2 to 3 grades higher than that of the surface part. In addition, the main load bearing direction of the mold should preferably be selected to be consistent with the deformation direction of the steel, so as to reduce the adverse effects of the anisotropy of the steel on the mold.

　　4. Thermal conductivity Thermal conductivity is also one of the main performance indicators of mold steel, especially some hot work mold steel and plastic mold steel. The mold steel with good thermal conductivity can quickly dissipate the heat generated during processing and the heat from the workpiece to avoid overheating of the working surface of the mold and improve the working conditions of the mold. For some thermoplastic molding molds and some die-casting molds, in order to speed up the production rhythm, it is hoped that the pressed workpiece will be cooled and demolded quickly to improve productivity. In order to solve this problem, some mold materials with better thermal conductivity than steel are sometimes selected. Such as High-strength copper alloy, high-strength aluminum alloy, etc.

　　5. Fine material and productization In order to shorten the manufacturing cycle of the mold, the mold manufacturing department should choose the fine material and products as possible when purchasing mold steel, such as fine steel that has been peeled, cold drawn or ground, and rough processed , Finishing, and even finishing quenched and tempered modules. The mold manufacturing department can use these fine materials and products to be assembled with standard mold bases after a little processing. It can effectively shorten the mold manufacturing cycle and meet the needs of the mold user department. Because the production of fine materials and products in the previous stage is produced in high-efficiency and mass-produced metallurgical plants, it can reduce production costs and improve material utilization.

　　Other factors that should be considered in the reasonable selection of mold steel When selecting mold steel, according to the use conditions and requirements of the mold, in addition to the above factors must be considered, especially the main properties of the mold steel must be compatible with the use conditions of the mold. It is also necessary to consider the price and versatility of the selected mold steel. Under normal circumstances, when the batch of workpieces produced is large and the size of the mold is small, the share of mold steel in the mold manufacturing cost is very small, and the price of mold steel can not be used as the main consideration index, and you can try to choose more advanced applicable mold steel. For large or extra-large molds with relatively simple shapes, since the cost of mold steel will account for a larger share in the total cost of the mold, it is possible to choose lower-priced mold steel or mold body according to the batch size of the workpiece produced. Low-cost mold steel, and in the key working parts of the mold, such as the cavity or cutting edge, the high-grade mold steel is inlaid or surfacing by inserting blocks or surfacing welding, which can not only improve the service life of the mold, In addition, the cost of materials can be reduced. The versatility of mold steel is also a factor that must be considered when selecting mold steel. Generally, the amount of mold steel is not large, and there are many varieties and specifications. In order to facilitate the purchase and preparation of materials in the market, the versatility of materials should be considered. In addition to special requirements, mass-produced general-purpose mold steel should be used as much as possible. Because the technology of general-purpose mold steel is relatively mature, there are more accumulated production processes and experience in use, and the performance data is relatively complete, which is convenient for reference in the design and manufacturing process. In addition, the selection of general-purpose mold steel can facilitate procurement, material preparation and material management.