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Vacuum heat treatment is a new type of thermal vacuum technology and heat treatment technology combining processing technology, vacuum vacuum heat treatment which refers to below atmospheric pressure atmosphere, including low, medium and high vacuum vacuum vacuum and ultra high vacuum, vacuum heat treatment practice also belongs to the controlled atmosphere heat treatment. Vacuum heat treatment is carried out in all parts of the heat treatment process under vacuum. Vacuum heat treatment can achieve almost all the heat treatment processes that conventional heat treatment can involve, and the quality of heat treatment is greatly improved. Compared with conventional heat treatment, vacuum heat treatment can achieve no oxidation, no decarburization and carburizing. It can remove phosphorus from the surface of the workpiece and degrease and degassing, so as to achieve the effect of surface bright purification.

 

Performance characteristics and key technologies of 2. die vacuum heat treatment

 

Vacuum heat treatment is a technology for metal parts to be quenched and cooled in oil or gas when the metal parts are heated in a vacuum or after a vacuum, and they are then heated through an inert gas. Due to the fact that the workpiece is basically non oxidized during vacuum heat treatment and the steel parts are not decarburization, the ventilation and convection heating mode can also make the heating uniform, reduce the temperature difference between the surface and the heart, and thus reduce the distortion. At present, it has become an indispensable and preferred heat treatment process for high quality tooling. What is more valuable is that vacuum heat treatment does not produce any substances that pollute the environment in the production process, which is generally recognized as a category of cleaner production technology. It is no exaggeration to say that the vacuum heat treatment has become the main symbol of the current advanced heat treatment production technology. The main characteristics of the development of vacuum heat treatment are convective heating, high pressure gas quenching, low pressure carburizing, ion carburizing, acetylene carburizing and so on.

 

Vacuum heat treatment technology is a new heat treatment technology developed in recent years, it has the characteristics that it is urgently needed in mold manufacturing, such as to prevent oxidation and decarburization heating, vacuum degassing or degassing, eliminating hydrogen embrittlement, good surface quality, little deformation, excellent mechanical properties, no pollution pollution-free, high degree of automation and a series of advantages, so as to improve the material (parts) plasticity, toughness and fatigue strength. In recent years, the technology of vacuum heat treatment has developed rapidly in China. It has the characteristics that are urgently needed in the mold manufacturing.

 

After vacuum heat treatment, the parts have little distortion and high quality, and the process itself is flexible and harmless. The vacuum heat treatment is not only a special alloy heat treatment of the necessary means, but also in the general engineering with the heat treatment of steel is also used, especially the tools, molds and precision coupling parts, after vacuum heat treatment service life has greatly improved than the general heat treatment. For example, the life of some moulds after vacuum heat treatment is 40 to 400% higher than that of the original salt bath, and the life of many tools can be increased by about 3~4 times. Besides, vacuum heating furnace can work at high temperature, and the workpiece can keep clean surface, so it can accelerate the adsorption and reaction process of chemical heat treatment. Therefore, some chemical heat treatment, such as carburizing, nitriding, chromizing, boriding, and multicomponent co impermeable, can get a faster and better effect.

 

The factors such as slow heating in vacuum and small temperature difference inside and outside of the parts determine the small deformation of the parts caused by the vacuum heat treatment process. The successful development and application of computer simulation technology in heat treatment process make the intelligent heat treatment of die possible. Due to the characteristics of small batch (even single piece) and multiple varieties, and the requirement of high heat treatment performance and no waste, the intelligent heat treatment of mould is necessary. The developed countries, such as the United States and Japan, have developed rapidly in the field of vacuum high pressure gas quenching, which is mainly aimed at the mold.

 

The development of vacuum heat treatment technology in China should meet the needs of industrial development and technological progress, combined with China's national conditions, should focus on the development of advanced vacuum heat for much-needed processing technology, the key technology of vacuum heat treatment of the main priority: high pressure gas quenching vacuum heat treatment technology and intelligent control system with low temperature convective heating and grading isothermal quenching function; continuous vacuum heat treatment production line and intelligent control system; vacuum cleaning technology; vacuum nitriding technology; vacuum carburizing in soot pollution, too sharp seepage problems; system of vacuum heat treatment process of various typical die steel; high efficiency vacuum heat treatment furnace.

 

Development and application of 3. die vacuum heat treatment

 

Generally speaking, a specific space full of less than atmospheric pressure is called vacuum. If we usually heat and heat preservation process of general heat treatment in negative pressure atmosphere, it is vacuum heat treatment. Vacuum heat treatment technology has excellent comprehensive mechanical properties and a series of outstanding advantages. It has been a hot spot in the development of international heat treatment technology for many years. In the process of hot working, the combination of traditional heat treatment and modern vacuum technology, computer technology and automation technology constitutes an advanced vacuum heat treatment technology.

 

The main application of the vacuum heat treatment of die is vacuum oil cooling quenching, vacuum air cooling quenching and vacuum tempering. In order to maintain the excellent characteristics of vacuum heating such as workpiece, such as mould, the selection and formulation of coolant and cooling process is very important. For the mold working face which is no longer machined after heat treatment, vacuum tempering, especially vacuum quenching of workpiece (mold), can be done after quenching. It can improve mechanical properties related to surface quality, such as fatigue performance and surface light.