Keywords: heat, treatment, mold heat treatment, precision, strength, working life, manufacturing cost, heat treatment, mold, vacuum heat treatment,

Mold heat treatment technology

　　Mold heat treatment is an important process to ensure the performance of the mold. It has a direct impact on the manufacturing accuracy of the mold, the strength of the mold, the working life of the mold, and the manufacturing cost of the mold. Since the 1980 s, the rapid development of international mold heat treatment technology is the field of vacuum heat treatment technology, mold surface strengthening technology and mold material pre-hardening technology. 　　vacuum heat treatment technology for molds

　　vacuum heat treatment technology is the 1 new type of heat treatment technology developed in recent years. its characteristics are exactly what are urgently needed in mold manufacturing, such as preventing heating oxidation and decarbonization, vacuum degassing or degassing, and eliminating hydrogen embrittlement, thereby improving the plasticity, toughness and fatigue strength of the material (part). Factors such as slow vacuum heating and small temperature difference between inside and outside of the part determine the small deformation of the part caused by the vacuum heat treatment process.

　　The main applications in vacuum heat treatment of molds are vacuum oil cooling quenching, vacuum gas cooling quenching and vacuum tempering. In order to maintain the excellent characteristics of vacuum heating of workpieces (such as molds), the selection and formulation of coolant and cooling processes are very important. The mold quenching process mainly uses oil cooling and air cooling. For the die working surface that is no longer machined after heat treatment, vacuum tempering is used as much as possible after quenching, especially the workpiece (die) of vacuum quenching, which can improve the mechanical properties related to surface quality, such as fatigue performance, surface brightness, corrosion resistance, etc.

　　The successful development and application of computer simulation technology for the heat treatment process has made it possible for the intelligent heat treatment of the mold. Due to the small batch (even single piece), multi-species characteristics of mold production, as well as the high requirements for heat treatment performance and the characteristics of not allowing waste products, the intelligent heat treatment of the mold becomes necessary. Foreign industrial developed countries, such as the United States, Japan, etc., in the vacuum high-pressure gas quenching, the development is also very fast, mainly for the target is also mold.

　　The surface treatment technology of the mold

　　In addition to the reasonable coordination of the matrix with sufficiently high strength and toughness, the surface performance of the mold is very important to the working performance and service life of the mold. The surface treatment technology of the mold is a systematic engineering that changes the shape, chemical composition, structure and stress state of the mold surface through surface coating, surface modification or composite treatment technology to obtain the required surface properties. At present, the main applications in mold manufacturing are nitriding, carburizing and hardened film deposition. Br/>
　　because nitriding technology can form a surface with excellent performance, and the nitriding process has good coordination with the quenching process of die steel, at the same time, the nitriding temperature is low, no intense cooling is required after nitriding, and the deformation of the die is extremely small, so the surface strengthening of the die is earlier and most widely used.

　　Mold carburizing is to improve the overall strength and toughness of the mold, that is, the working surface of the mold has high strength and wear resistance. Hardening film deposition technology is currently more mature CVD, PVD. The mold has been coated with hardened film technology since the 1980 s. Under the current technical conditions, the cost of hardened film deposition technology (mainly equipment) is relatively high, and it is still only used in some precision and long-life molds. If the method of establishing a heat treatment center is adopted, the cost of coating hardened film will be greatly reduced. If more molds adopt this 1 technology, the overall level of mold manufacturing in our country can be improved. 
　　pre-hardening technology for mold materials

　　the idea of pre-hardening has been put forward internationally since the 1970 s. however, due to the constraints of the rigidity of processing machines and cutting tools, the hardness of pre-hardening cannot reach the use hardness of molds, so the research and development investment in pre-hardening technology is not large. With the improvement of the performance of machine tools and cutting tools, the development of pre-hardening technology for mold materials has accelerated. By the 1980 s, the proportion of pre-hardening modules used in plastic mold materials in developed countries has reached 30% (currently above 60%).

　　In terms of pre-hardening technology of mold materials in my country, it started late and has a small scale, and it cannot meet the requirements of domestic mold manufacturing. The use of pre-hardened mold materials can simplify the mold manufacturing process, shorten the mold manufacturing cycle, and improve the mold manufacturing accuracy. It is foreseeable that as processing technology advances, pre-hardened mold materials will be used for more mold types.

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