What is vacuum heat treatment

It mainly refers to the new heat treatment technology combining vacuum technology and heat treatment technology. Among them, the vacuum environment of vacuum heat treatment refers to the atmosphere environment lower than one atmospheric pressure, including low vacuum, medium vacuum, high vacuum and ultra-high vacuum. Therefore, vacuum heat treatment actually belongs to atmosphere controlled heat treatment.

Vacuum heat treatment means that all and part of the heat treatment process are carried out in vacuum state. Vacuum heat treatment can achieve almost all the heat treatment processes that can be involved in conventional heat treatment, but the quality of heat treatment is greatly improved.

Compared with the conventional heat treatment, the vacuum heat treatment processing technology can realize no oxidation, no decarburization and no carburization at the same time, and can remove the phosphorus chips on the surface of the workpiece, and has the function 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 technology has been applied earlier in foreign countries, but after decades of efforts in China, vacuum furnace manufacturers have made great improvement in design, manufacturing level and quality. Domestic vacuum equipment is gradually replaced by imported vacuum equipment, thus reducing the production cost of the user and rapidly expanding the application scope of vacuum heat treatment 。

2. Process principle of vacuum heat treatment processing technology

According to the characteristics of phase transformation of metals in vacuum, the thermodynamics and kinetics of solid-state phase transformation do not change much in vacuum, which is only 0.1MPa away from atmospheric pressure. In the process of vacuum heat treatment, the principle of solid-state transformation at atmospheric pressure and the data of various types of structure transformation at atmospheric pressure can be used for reference. At the same time, under the action of vacuum degassing, the physical and mechanical properties of metal materials can be improved. When heated in vacuum, the elements on the surface of metal workpiece will evaporate. The vacuum degree required for the metal to realize the non oxidation heating, the surface purification function, and the realization of less non oxidation and less non removal.

3. Characteristics of vacuum heat treatment processing technology

Vacuum heat treatment is a non oxidation heat treatment technology which is widely used in parallel with controllable atmosphere. It is also one of the main signs of the advanced level of heat treatment production technology. Vacuum heat treatment can not only achieve no oxidation and decarburization of steel parts, but also achieve no pollution and less distortion of workpieces. Therefore, it belongs to clean and precision production technology. At present, it has become an irreplaceable advanced technology in tooling production.

According to the experience at home and abroad, the distortion of vacuum heat treatment is only one third of that of salt bath quenching. It is of great significance to study the vacuum heating method and the distortion law of various materials and parts with different complexity under various cooling conditions, and simulate them with computer. During vacuum heating, atmospheric pressure or high pressure air cooling quenching, the air flow uniformity has a great influence on the hardening effect and quality dispersion of the parts. It is of great significance for improving the furnace structure to study the air circulation in the furnace by means of computer simulation.

Modern vacuum heat treatment furnace refers to a cold wall furnace which can heat components in vacuum and then quench them in oil or in atmospheric pressure and pressure gas. Research and development of this type of equipment is a comprehensive, interdisciplinary work involving many scientific and technological fields.

The application prospect of vacuum heat treatment of die material is very big. At present, most die steel is heated in vacuum and then cooled and quenched in gas. In order to obtain satisfactory mechanical properties on the surface and inside of the workpiece, it is necessary to use the technology of vacuum high pressure gas quenching. At present, the pressure of vacuum gas quenching in the world has increased from 0.2MPa, 0.6MPa to 1-2mpa or even 3Mpa. Therefore, the gradual increase of cooling gas pressure of high pressure gas quenching vacuum furnace is an important development trend.