What is vacuum heat treatment processing technology? It mainly refers to a new 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 atmospheric pressure, 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 the heat treatment processes involved in conventional heat treatment, but the heat treatment quality is greatly improved.

Compared with conventional heat treatment, the vacuum heat treatment technology can realize no oxidation, no decarburization, and no carburization at the same time.

1. Application of vacuum heat treatment technology

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

After decades of efforts in my country, vacuum furnace manufacturers have greatly improved the design, manufacturing level and quality, and the use of domestic vacuum equipment to replace imported vacuum equipment has gradually increased, thereby reducing the production of users. Cost, the scope of application of vacuum heat treatment rapidly expanded.

Second, the process principle of vacuum heat treatment technology

Taking advantage of the phase transformation characteristics of metals in a vacuum state, the thermodynamics and kinetics of solid-state phase transformation do not change in a vacuum that is only 0.1 MPa away from atmospheric pressure. When formulating the vacuum heat treatment process specification, the principle of solid-state phase transformation under normal pressure can be completely based on, and the data of various types of microstructure transformation under normal pressure can be completely referenced. At the same time, under the action of vacuum degassing, the physical and mechanical properties of metal materials can be improved. When heated in a vacuum state, elements on the surface of metal workpieces will evaporate. The vacuum degree required by the metal to achieve non-oxidative heating, the surface purification effect, and the realization of less and no oxidation and less dehydration.

3. Characteristics of vacuum heat treatment processing technology

(1) Advantages of vacuum heat treatment

Vacuum heat treatment processing is a non-oxidative heat treatment technology with a wide range of applications and a controllable atmosphere, and it is also one of the main symbols of the advanced degree of heat treatment production technology. Vacuum heat treatment can not only achieve no oxidation and 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 tool and die production.

(2) The distortion of the workpiece in the vacuum heat treatment process is small

According to domestic and foreign experience, the distortion amount of workpiece vacuum heat treatment is only one third of that of salt bath heating and quenching. It is of great significance to promote the vacuum heat treatment technology to study the vacuum heating methods of various materials and parts of different complexity and the distortion laws under various cooling conditions, and simulate them with computers. During vacuum heating, normal pressure or high pressure air cooling quenching, the uniformity of airflow has a great influence on the quenching effect and mass dispersion of parts. It is of great significance to improve the structure of the furnace to study the air circulation law in the furnace by means of computer simulation.

(3) Using a vacuum heat treatment furnace

Modern vacuum heat treatment furnaces refer to cold-wall furnaces that can perform vacuum heating of components and then quench in oil or quench in atmospheric and pressurized gas. Research and development of this type of equipment is a comprehensive, interdisciplinary work involving many fields of science and technology.

The application prospect of vacuum heat treatment of tool and mold materials is very large. Most tool 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 air quenching has been increased from 0.2MPa, 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.