There is thermal stress and tissue stress in the heat treatment of
seamless steel pipe. The internal stress can be superimposed or partially offset, it is complex and changeable, because it can change with heating temperature, heating speed, cooling speed, cooling speed, shape and size of parts, so the heat treatment deformation is inevitable. The mechanical collision of the seamless steel pipe in the heat treatment process can also cause the deformation of the parts, but the deformation can be improved with the operation, thus reducing and avoiding.
1, surface decarbonization
In the process of heat treatment, if the seamless steel tube is heated in the oxidation medium, the surface will be oxidized by some surface, thus reducing the quality of carbon and leading to the decarburization of the surface. The surface decarburization depth will exceed the final processing volume and scrap parts will be scrapped. Determination of surface decarburization depth by metallographic method and microhardness method can be used for metallographic examination. The arbitration standard is based on the measurement method of surface microhardness distribution curve.
2, soft point
Due to the lack of heat, poor cooling, improper quenching, and so on, the phenomenon that the surface hardness of seamless steel pipe is not enough is called the quenching point. Surface decarburization can cause surface wear and fatigue strength.
