Vacuum carburizing heat treatment process

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The results show that the flatness is not well controlled and the flatness is poor. The mounting method is improved, the hanging mode of h-shaped material rod is adopted, and the width, groove depth, wall thickness and other parameters of material rod are constantly improved, which can improve the flatness and stability of parts, and the deformation qualification rate of parts is also improved.

Advantages of vacuum carburizing heat treatment process

Although the vacuum carburizing equipment and process appeared for a short time, but because of a series of significant advantages and characteristics, so, the application scope in production is expanding rapidly.

(1) it is easy to control the depth of the carburizing layer, the carbon concentration, and the concentration gradient (hardness gradient).

Due to the characteristics of physical and chemical reactions in the process of vacuum carburizing, the process parameters of vacuum carburizing heat treatment can be determined simply by calculation or some relation curves according to the technical conditions of the parts. The production practice shows that, especially for batch production, the process parameters calculated need to be verified and corrected by process experiments, which is very important for batch production of high precision and important parts. The production practice also shows that as long as the process parameters determined by the process experiment are operated, the consistent carburizing results of each furnace can be obtained with good reproducibility.

(2) high surface quality of carburized parts.

Because the vacuum carburizing heat treatment is in the vacuum state heating, heating and carburizing after the diffusion, so the parts do not produce decarburization and black tissue and other problems, the surface is clean. In this way, the cleaning process can be eliminated and the finishing process after heat treatment can be facilitated.

(3) vacuum carburized parts have high mechanical properties.

Because the vacuum carburized heat treated parts have the characteristics of high surface quality (no decarburization, no oxidation), it has a favorable effect on the stress state and fatigue strength of the surface layer.

(4) it has good carburizing effect on the parts with blind hole, deep hole and narrow seam. It is difficult to carburize stainless steel and silicon steel by gas carburizing heat treatment method.

(5) thin, thick (up to 7mm) and high carbon concentration carburizing layer can be obtained. A steep or gentle carbon concentration gradient can be obtained by matching the carburizing period with the diffusion period.

(6) high temperature carburizing heat treatment can be carried out to shorten the carburizing time.

Vacuum carburizing is developed on the basis of exploring the possibility of high temperature carburizing. The reason why high temperature carburizing is possible in vacuum state is that the structure and component material of modern vacuum carburizing furnace have been able to meet the requirements of high temperature carburizing.

High temperature carburizing heat treatment can significantly reduce the carburizing time. This is because austenite has a higher solubility to carbon at high carburizing temperatures, and the carburized gas used can fully supply activated carbon atoms. Also because high temperature carburizing can significantly increase the diffusion rate of carbon in steel. In addition, the parts are heated in the vacuum state, which produces degassing, removal of oxides and other effects, thus activating the surface of the parts and accelerating the absorption process of carbon atoms.

Under normal gas carburizing conditions, the carburizing furnace can not withstand high temperature for a long time. Therefore, the high temperature carburizing experiments with gas carburizing furnace for many years have not been successful.