The workpiece is heat treated using a high-frequency induction heating machine, what are the factors that affect its decarburization?

The workpiece is heat treated using a high-frequency induction heating machine. Affected by many factors, the workpiece may produce decarburization defects. Decarburization reduces the fatigue strength, hardness and wear resistance of the workpiece. Therefore, it is very important to understand the reasons for the formation of decarburization. Today, the editor will tell you what are the factors that affect decarbonization?

Decarburization, like oxidation, is both a chemical process and an atomic diffusion process. Therefore, the main factors affecting decarburization are the chemical composition of the heated metal and the heating environment (such as heating temperature and heating time), that is, internal factors. and external factors.

1) Chemical composition in steel

The more carbon the steel contains, the deeper the decarburization layer will be. Among alloying elements, elements such as W, Al, SI, and Co promote increased decarburization, while elements such as Cr and Mn prevent decarburization. Ni and V have no effect on the decarburization of steel.

2) Heating temperature and heating time

The workpiece is heated using a high-frequency induction heating machine. Generally speaking, as the heating temperature increases and the heating time prolongs, the tendency of decarburization will be intensified. However, when the temperature of steel is 700℃-1000℃, the oxide scale formed on the surface can hinder the diffusion of carbon and weaken the degree of decarburization. When the temperature rises again, as the speed of carbon diffusion increases, the oxide scale also loses its protective effect and decarburization occurs. The layer is further deepened, and decarburization is more intense than oxidation, such as GCr15 steel. When heated to 1100℃-1200℃, intense decarburization will occur. The longer the heating time, the deeper the decarburization layer. But it is not directly proportional. When it exceeds a certain value, the increase in decarburization depth gradually weakens. At this time, decarburization is more intense than oxidation. The test pointed out that after 0.5h of high-speed steel at a high temperature of 1000℃, the depth of the decarburization layer is 0.4mm, 1.0mm after 4h of heat preservation, and only 1.2mm after 12h of heat preservation; if the heating temperature is raised to 1050℃, the decarburization layer will The depth of the carbon layer is increased to 2mm.

From the above description, we can see that heating temperature and heating time are important factors affecting decarburization. Therefore, during the heat treatment using a high-frequency induction heating machine, we should strictly follow the process operations to ensure that the heating temperature and The heating time meets the requirements.