For various reasons, the decarburization of the workpiece during the quenching of the salt bath is inevitable. If the decarburization layer is relatively thin, the subsequent grinding process can be completely removed without any problem; if the decarburization layer cannot be ground, it will seriously affect the product. quality.
1. Effect of decarburization on product quality
Decarburization refers to the phenomenon that the surface carbon content of steel decreases when heated, or the combustion of steel surface carbon, ie 
The essence of decarburization is that the carbon of the steel surface layer acts on oxygen and hydrogen at high temperature, which causes the surface state to change, thus affecting the quality of heat treatment , mainly in the following aspects.
(l) Early failure
Decarburization reduces the surface hardness of the workpiece after quenching and affects the service life. Such as W18Cr4V steel 
Screw slot milling cutter, the microstructure of the tip surface is white crystalline decarburization layer (microhardness 338HV) + a small amount of black torconium transition zone (microhardness 627HV) + normal tempered martensite and a small amount The carbide (microhardness 825HV) is shown in Figure 1. The decarburization layer is distributed along the tooth profile, and it can be seen that decarburization is produced in the heat treatment . Milling cutters fail early due to low hardness.
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