On 2018-08-08 14:48:54
Surface decarburization of heat treated products
Decarburization is a phenomenon that the carbon content of steel surface decreases during heat treatment. The essence of decarburization is that the carbon atoms in steel produce methane or carbon monoxide to the atmosphere (such as hydrogen or oxygen) in the furnace at high temperature. Decarburization is the result of mutual diffusion of atoms during heat treatment. On the one hand, oxygen diffuses to steel, on the other hand, carbon in steel diffuses outward. Only when the decarburization rate exceeds the oxidation rate can the decarburization layer be formed.
When the oxidation rate is very high, there will be no obvious decarburization phenomenon, that is, the iron produced after decarburization layer is oxidized to oxidized skin. Therefore, a deeper decarburization layer can be formed in the atmosphere with relatively weak oxidation.
The decarburization layer of steel includes two parts: full decarburization layer and partial decarburization layer (transition layer). Partial decarburization layer refers to the structure with normal carbon content after the whole decarburization layer. In the case of no serious decarburization, sometimes only part of the decarburization layer does not have a complete decarburization layer.
The depth of decarburization layer can be determined by many methods according to the change of decarburization composition, microstructure and properties. In the actual heat treatment production, it is the most common method to determine the decarburized layer of steel by metallographic method.