Vacuum heat treatment

Vacuum heat treatment is a comprehensive technology combining vacuum technology and heat treatment, which means that all and part of the heat treatment process is performed under vacuum. Vacuum heat treatment can realize almost all heat treatment processes, such as quenching, annealing, tempering, carburizing, chromizing, nitriding. In the quenching process, gas quenching, oil quenching, nitrate quenching, and water quenching can be achieved. Compared with the following advantages.

1. Non-oxidation, non-decarburization and non-carbon increase have a good protection effect on the interior and surface of the workpiece;
Oxidation causes the metal surface to lose its metallic luster, surface roughness increases, and accuracy decreases, and the oxide scale on the steel surface is often the source of quenching soft spots and quench cracking. Oxidation reduces the strength of steel parts and other mechanical properties. Decarburization refers to the phenomenon that the surface carbon content of the steel decreases when it is heated.

Generally, oxidative decarburization of steel is performed simultaneously. Due to the oxidation of the decarburized layer, the reduction of carbon content will significantly reduce the quenching hardness, wear resistance, and fatigue performance of the steel.

In vacuum heat treatment, because the metal is heated under a certain degree of vacuum, the workpiece is prevented from contacting with oxygen. The workpiece is not oxidized and decarburized, and a bright surface and good heat treatment quality can be obtained. When a reduction reaction occurs, no carbon increase occurs.

2. Improve the overall mechanical performance, degassing and promote the purification of metal surfaces;
Vacuum has a clear degassing effect on liquid metals, and it also has a good exclusion effect on dissolved gases in solid metals. The most harmful gas in the metal is hydrogen. When vacuum heating is used, the hydrogen in metals and alloys can be quickly reduced to the lowest level, eliminating hydrogen embrittlement, thereby improving the plasticity, toughness and fatigue strength of the material, and improving the overall mechanical properties of the workpiece. When metals and alloys are heated in vacuum, if the degree of vacuum is lower than the decomposition pressure of the corresponding oxide, this oxide will decompose, and the formed free oxygen will be immediately discharged out of the vacuum chamber, which will further improve the quality of the metal surface and even make The surface reaches the activated state and plays a role of purification.

3. Small deformation of the workpiece;
Generally speaking, the processed workpiece is heated by heat radiation in the furnace, the temperature difference between the inside and outside is small, and the thermal stress is small. Therefore, the deformation of the parts treated by the vacuum heat treatment process is small. At the same time, the workpiece is heated under vacuum and quenched under vacuum. It is automatically completed. , Avoiding the handling of the workpiece in the air in the hot state (although the salt bath treatment and the atmosphere protection treatment are heated in an anaerobic environment, but the quenching is still completed in the air or a quenching medium containing oxygen molecules), reducing artificial processing deformation . For example, the rolling wheel made of Cr12MoV is vacuum heat treated and salt bath treated. The vacuum heat treatment has 70% less deformation than the salt bath, and the product qualification rate is high.

4. It can reduce the volatility of gold elements in the workpiece;
Vacuum heat treatment can be heated and vacuum quenched in a controlled atmosphere, thereby reducing the volatility of gold-containing elements in the workpiece and ensuring the quality of heat treatment of the workpiece.

5. Others;
The vacuum heat treatment furnace has high thermal efficiency and can achieve rapid heating and cooling; the stability and repeatability are good. The working environment is good, the operation is safe, and there is no pollution and pollution.