Mold heat treatment is an important process to ensure mold performance. It has a direct impact on the following properties of the mold: 1, the manufacturing precision of the mold: uneven transformation of the structure, incompleteness and excessive residual stress caused by heat treatment, resulting in deformation of the mold after heat treatment, assembly and mold use, Thereby reducing the accuracy of the mold, and even scrapped. 2, the strength of the mold: improper heat treatment process, heat treatment operation is not standardized or the state of heat treatment equipment is not intact, resulting in the strength (hardness) of the treated mold can not meet the design requirements. 3, the working life of the mold: the unreasonable structure caused by heat treatment, excessive grain size, etc., leading to major properties such as mold toughness, hot and cold fatigue performance, anti-wear performance, etc., affecting the working life of the mold. 4, the manufacturing cost of the mold: as the intermediate process or the final process of the mold manufacturing process, the cracking, deformation and poor performance caused by the heat treatment, in most cases will make the mold scrapped, even if it can be used through repair, it will Increase working hours, extend delivery time, and increase mold manufacturing costs. It is the heat treatment technology that has a very close relationship with the quality of the mold, which makes these two technologies promote each other and improve together in the process of modernization. What kinds of heat treatment technologies are there now? First, the surface treatment technology of the mold: In addition to the reasonable cooperation of the mold with sufficient strength and toughness, the surface performance of the mold is on the working performance and service life of the mold.
It is important. The surface treatment technology of the mold is to systematically change the morphology, chemical composition, microstructure and stress state of the mold surface by surface coating, surface modification or composite treatment technology to obtain the desired surface properties. At present, most of the applications in mold manufacturing are nitriding, carburizing and hardening film deposition. Because the nitriding technology can form a surface with excellent performance, and the nitriding process has good coordination with the quenching process of the die steel, and the nitriding temperature is low, there is no need for intense cooling after nitriding, and the deformation of the mold is extremely small, so the mold is Surface strengthening is the earliest and most widely used nitriding technique. Second, the pre-hardening technology of the mold material: Since the 1970s, the idea of pre-hardening has been proposed internationally, but due to the rigidity of the machine tool and the constraints of the cutting tool, the hardness of the pre-hardening cannot reach the hardness of the mold, so The research and development of hardening technology is not much invested. 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 1980s, the proportion of pre-hardened modules used in plastic molds in industrialized countries in the world has reached 30%. Third, the vacuum heat treatment technology of the mold: Vacuum heat treatment technology is a new type of heat treatment technology developed in recent years. Its characteristics are urgently precision mold manufacturing needed in mold manufacturing, such as preventing heating oxidation and non-decarburization. Vacuum degassing or degassing to eliminate hydrogen embrittlement, thereby improving the plasticity, toughness and fatigue strength of materials (parts). Factors such as slow vacuum heating and small temperature difference between the inside and outside of the part determine the deformation of the parts caused by the vacuum heat treatment process. The main application of mold vacuum heat treatment is vacuum oil quenching, vacuum gas quenching and vacuum tempering. In order to maintain the excellent characteristics of vacuum heating of workpieces (such as molds), it is very important to select and formulate coolants and cooling processes. The mold quenching process mainly uses oil cooling and air cooling. For the working face of the mold which is no longer machined after heat treatment, vacuum tempering is used as much as possible after quenching, especially vacuum hardened workpiece (mold), which can improve the mechanical properties related to surface quality, such as fatigue performance, surface brightness, Corrosion resistance, etc.
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