With the deepening of the machinery and equipment industries and mature, the progressive refinement of the industry, markets have continued to increase. At present, about "after heat treatment of bearing parts by some of the common quality defects of" awareness of the growing.
Common quality defects after heat treatment of bearing parts: quenching microstructure of soft spots and surface removal, heat treatment, crack, not enough hardness, under heat, overheating, etc.
1. soft point
Due to inadequate heating, poor cooling, hardened bearing surfaces caused by improper operation of local phenomenon called quenching hardness not enough soft spots. It like decarburization can cause surface wear resistance and fatigue strength of serious decline.
2. surface decarburization
In heat treatment of bearing parts, if it is heating in oxidizing medium, surface oxidation occurs so that part of the surface carbon content reduced, causing decarburization. Surface decarbonization layer depth exceeds the amount of final processing will cause scrap. Determination of surface decarbonization layer depth available in the metallographic examination of metallographic methods and micro-hardness method. The microhardness distribution curve of the surface layer measurement shall prevail, can do arbitration criterion.
3. heat treatment deformation
In heat treatment of bearing parts, thermal and stress, this stress can be superimposed or partially offset is complex, as it can with the heating temperature, heating, cooling, cooling rates, parts vary in shape and size, so distortion is inevitable. Understanding and grasp of its variation can make the deformation of the bearing elements (such as oval ring, size up, etc) where it can control the scope of production. Of course in the heat treatment process of mechanical collision will cause deformation, but this kind of distortion can be reduced by improved operations and avoid.