With the development of science and technology in recent years, the technology application of mould industry is also rising. Mold enterprises have been focusing on improving the metallurgical quality of die steels. After years of efforts and exploration, at present, the main metallurgical production departments at home and abroad are committed to improving the metallurgical quality of die steels mainly in the following aspects:
1. Smelting quality is widely used for high quality mould steel. It is widely used in the process of furnace refining, vacuum treatment, vacuum smelting, powder injection treatment, electroslag remelting, reducing the content of harmful elements, oxygen, hydrogen and inclusions in steel, and trimming the chemical composition and pouring temperature. Electroslag remelting can also effectively improve the macrostructure and density of steel and improve the isotropism of die steels. Experiments in some domestic production plants show that the lateral impact toughness of 4Cr5MoSiV1 steel produced by EAF is only 31% in the longitudinal direction. Through the 4Cr5MoSiV1 steel after electroslag remelting, the lateral impact toughness can be equal to 70% in the longitudinal direction and 1 times higher than that in the longitudinal direction. For the special requirements of the die steel, the powder high speed steel and the powder high alloy die steel produced by the powder metallurgy process can better improve the structure and properties of the steel.
2. On the basis of guaranteeing a certain forging ratio, forging and rolling process can be used to upsetting the long forging and cross rolling process as much as possible in order to improve the isotropic of the die material. In order to reduce the processing allowance and improve the utilization of material, it is widely used in precision forging machine, fast forging water press and high precision continuous rolling mill to provide high precision steel for mould manufacturing.
3. Heat treatment of heat treatment and fine processing and rolling material should be treated with controlled atmosphere or vacuum heat treatment to avoid oxidation decarburization. Some plastic mould steel and hot working die steel should be pretreated by metallurgical sector. For some high demand hot die materials, the metallurgical sector should be prepared in advance by Metallurgical departments to remove the coarse carbide and chain like carbides in the steel, and to obtain fine and uniformly distributed carbides to further improve the properties of the steel, especially the isotropic property. According to some foreign reports, some hot working die steels have produced high quality and high direction die steel through electroslag remelting, multi direction forging (rolling) and microstructure refinement, and the lateral impact toughness can be equal to more than 90% in the longitudinal direction. Many steel mills have named the brand names for the steel produced by this process, such as the ISODISC of Austria Bole steel plant, the ISOTROPY of the Hitachi Metals Ltd, the MICROFINE of the Japanese high weekly steel company, and so on, and many metallurgical production departments of our country are also committed to this work. In addition, considering the metallurgical quality of each part of the steel, we should pay attention to the choice of the main working face (such as the cavity or blade) to close the surface of the steel. In general, the surface of the steel is a relatively clean part of the steel, and the core of the steel is a relatively concentrated area of the low times defects of the steel; especially in the area. The eutectic carbide heterogeneity of the steel in the center section will be 2~3 higher than that on the surface. Also, the direction of the main load bearing of the mold is best consistent with the direction of deformation of the steel so as to reduce the adverse effect of anisotropy of the steel on the die.
4, thermal conductivity is also one of the main performance indexes of die steels, especially for some hot working die steels and plastic mould steels. The mold steel with good thermal conductivity can quickly pass the heat produced in the processing and the heat from the workpiece to be processed to avoid overheating on the working surface of the mold to improve the working conditions of the mold. For some thermoplastic forming dies and some die casting moulds, in order to speed up the production rhythm, the workpiece is quickly cooled and removed to improve the productivity. In order to solve this problem, some die materials, such as high strength copper alloy and high strength aluminum alloy, are sometimes used to improve the thermal conductivity of steel.
5. In order to shorten the manufacturing cycle of mould, the mold manufacturing department should choose fine materials and products, such as fine steel after peeling, cold drawing or grinding, through rough processing, finishing, even finishing and tempering. The mold manufacturing department can use these fine materials and products for a little processing to be assembled with standard mold bases. It can not only effectively shorten the mold manufacturing cycle, adapt to the needs of the mold use department, but also because the previous stage of the production of fine materials and products is high efficiency and mass production in the metallurgical plant, which can reduce the cost of production and improve the utilization of materials.
Other factors that should be considered for the rational selection of die steel should be considered in the selection of die steel. In addition to the conditions and requirements of the mold, the main properties of the mould must be taken into consideration, especially the main properties of the die steel must be adapted to the requirements of the use conditions of the mould, and the price and the pass of the selected die steel must be considered. Use sex. Generally, when the production is large and the size of the mold is small, the share of the die steel in the mold manufacturing cost is very small. The price of the die steel can not be considered as the main consideration, and the more advanced and applicable mould steel can be chosen as far as possible. For the large or more simple mold, because the cost of the die steel will take a larger share in the total cost of the mold, it is possible to select the lower price die steel according to the batch production of the workpiece, or to choose the mould steel with low price in the mold body, and in the key parts of the mold, such as the die steel. An inlaid or surfacing side at a cavity or edge.