What is vacuum heat treatment processing technology?

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What is vacuum heat treatment processing technology? Mainly refers to a new type of heat treatment technology that combines vacuum technology and heat treatment technology. Among them, the vacuum environment in which vacuum heat treatment is located refers to an atmosphere environment below one atmosphere, including low vacuum, medium vacuum, high vacuum and ultra-high vacuum, etc. Therefore, vacuum heat treatment actually belongs to atmosphere controlled heat treatment.

Vacuum heat treatment means that all and part of the heat treatment process is carried out in a vacuum state. Vacuum heat treatment can realize almost all heat treatment processes that can be involved in conventional heat treatment, but the quality of heat treatment is greatly improved.
Compared with conventional heat treatment, vacuum heat treatment processing technology can achieve no oxidation, no decarburization, and no carburization at the same time. It can remove phosphorous chips on the surface of the workpiece, and has the functions of degreasing and degassing, so as to achieve the effect of surface bright purification.

1. Application of vacuum heat treatment processing technology

In fact, vacuum heat treatment processing technology has been applied earlier in foreign countries. In 1968, the United States and Japan successively developed vacuum quenching oil and aqueous quenching medium. As a result, vacuum quenching technology has developed rapidly in the heat treatment industry, from single-chamber furnaces to The multi-combination machine group has developed from general vacuum quenching to high-pressure gas quenching, vacuum water quenching, vacuum carburizing, vacuum carbonitriding and multi-component co-infiltration.

In my country, after decades of hard work, vacuum furnace manufacturers have greatly improved their design, manufacturing level and quality. The replacement of imported vacuum equipment with domestic vacuum equipment has gradually increased, thus reducing the production of users. The cost has rapidly expanded the application range of vacuum heat treatment.

2. Process principle of vacuum heat treatment processing technology

Utilizing the disguised characteristics of metals in a vacuum state, the thermodynamics and kinetics of solid-state phase transitions will not change in a vacuum within 0.1 MPa of atmospheric pressure. When formulating the vacuum heat treatment process regulations, it can be based on the principle of solid phase transition under normal pressure, and can refer to the data of various types of tissue transformation under normal pressure. At the same time, under the action of vacuum degassing, the physical and mechanical properties of metal materials can be improved. When heating in a vacuum state, the surface elements of the metal workpiece will evaporate. The metal realizes the vacuum degree required for oxidation-free heating, and the surface purification effect realizes less oxidation and no loss.

3. the characteristics of vacuum heat treatment processing technology

(1) Superiority of vacuum heat treatment processing
Vacuum heat treatment processing is a non-oxidation heat treatment technology with a wide range of applications that keeps pace with the controllable atmosphere, and it is also one of the main signs of the advanced degree of current heat treatment production technology. Vacuum heat treatment can not only achieve no oxidation and no decarburization of steel parts, but also achieve no pollution in production and less distortion of workpieces. Therefore, it also belongs to the category of clean and precise production technology. At present, it has become an irreplaceable advanced technology in the production of molds.

(2) The distortion of the workpiece in the vacuum heat treatment process is small
According to domestic and foreign experience, the amount of distortion of workpiece vacuum heat treatment is only one third of that of salt bath heating and quenching. It is of great significance to study the vacuum heating methods of various materials and parts with different levels of complexity and the distortion laws under various cooling conditions, and to simulate them with a computer, which is of great significance for the promotion of vacuum heat treatment technology. During vacuum heating, atmospheric pressure or high-pressure air cooling, the uniformity of airflow has a great influence on the hardening effect and quality dispersion of parts. The use of computer simulation methods to study the law of air circulation in the furnace is of great significance for improving the structure of the furnace.

(3) Use vacuum heat treatment furnace
Modern vacuum heat treatment furnace refers to a cold-wall furnace that can perform vacuum heating of components, and then quench in oil or in atmospheric pressure and pressurized gas. The research and development of this type of equipment is a comprehensive, interdisciplinary work involving many scientific and technological fields. The application prospects of vacuum heat treatment for tool and die materials are great. Most tool and die steels are currently heated in a vacuum, and then cooled and quenched in a gas. In order to obtain satisfactory mechanical properties on the surface and inside of the workpiece, vacuum high-pressure gas quenching technology must be used. At present, the air pressure of vacuum gas quenching has increased from 0.2MPa and 0.6MPa to 1-2MPa or even 3MPa in the world. Therefore, the gradual increase of the cooling gas pressure of the high-pressure gas quenching vacuum furnace is an important development trend.

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