What is vacuum heat treatment processing technology?

Principle, characteristics and application of vacuum heat treatment processing technology

It mainly refers to the new heat treatment technology combining vacuum technology and heat treatment technology, among which, the vacuum environment of vacuum heat treatment refers to the atmosphere environment lower than one atmosphere 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 refers to all and part of the heat treatment process in the vacuum state, vacuum heat treatment can achieve almost all the conventional heat treatment can be involved in the heat treatment process, but the quality of heat treatment is greatly improved.

Compared with the conventional heat treatment, the vacuum heat treatment processing technology can simultaneously achieve no oxidation, no decarburization, no carburizing, can remove the phosphorus chip on the surface of the workpiece, and has the effect of degreasing and degassing, so as to achieve the effect of surface brightness and purification.

1. Application of vacuum heat treatment processing technology

Actually, vacuum heat treatment processing technology abroad application earlier, vacuum research of Hays companies in the United States and Japan in 1968, has developed the vacuum quenching oil and water-based quenching medium, thereby, vacuum quenching technology in heat treatment industry gets rapid development, from a single chamber furnace to combined fleet, from the general development to the high pressure gas quenching vacuum hardening, vacuum water quenching, vacuum carburizing and carbonitriding and multivariate altogether permeability, etc.

After decades of efforts in China, vacuum furnace manufacturers in the design, manufacturing level and quality have been greatly improved, with domestic vacuum equipment to replace imported vacuum equipment from abroad gradually increased, thus reducing the use of unit production costs, so that the application of vacuum heat treatment rapidly expanded.

2. Process principle of vacuum heat treatment processing technology

According to the characteristics of metal phase transformation in vacuum, the thermodynamics and kinetics of solid phase transformation do not change in the vacuum with a difference of 0.1MPa from the atmospheric pressure. In the process of vacuum heat treatment, the principle of solid phase transition under atmospheric pressure and the data of various types of microstructure transformation under atmospheric pressure can be referred to. At the same time, under the action of vacuum degassing, the physical and mechanical properties of metal materials can be improved. When heated in the vacuum state, the surface elements of metal workpiece will evaporate. The metal can achieve the vacuum degree required by oxidization-free heating and the surface purification effect to achieve less oxidization-free and less desorption.

3. Characteristics of vacuum heat treatment processing technology

(1) advantages of vacuum heat treatment processing

Vacuum heat treatment processing is a non-oxidized heat treatment technology with wide application, which keeps pace with controlled atmosphere, and is also one of the main indicators of the advanced degree of the current heat treatment production technology. Vacuum heat treatment can not only achieve no oxidation, no decarburization of steel, but also can achieve no pollution and less distortion of the workpiece, so it also belongs to the clean and precise production technology category. At present, it has become an irreplaceable advanced technology in mold production.

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

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

(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 quench in atmospheric pressure and pressurized gas. The research and development of this type of equipment is a comprehensive, interdisciplinary and involves many fields of science and technology.

The application prospect of vacuum heat treatment for die materials is very great. Most 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 adopted. At present, the pressure of true air quenching in the world has been increased from 0.2mpa and 0.6mpa to 1-2mpa and even 3MPa. Therefore, the gradual increase of cooling gas pressure in high-pressure gas quenching vacuum furnace is an important development trend.