Thermal stress and structural stress exist in seamless steel tube during heat treatment. Internal stress can be superimposed or partially offset, which is complex and changeable, because it can vary with heating temperature, heating speed, cooling speed, cooling speed, the shape and size of parts, so heat treatment deformation is inevitable. The mechanical collision of seamless steel tube during heat treatment can also cause the deformation of parts, but the deformation can be improved by operation, thus reducing and avoiding.


1. Surface decarbonization
In the heat treatment process, if the seamless steel pipe is heated in the oxidizing medium, the surface will be oxidized by some surfaces, which will reduce the quality of carbon and lead to surface decarbonization. Surface decarbonization depth will exceed the final processing volume, and waste components will be discarded. The decarburization depth can be measured by metallographic method and microhardness method, which can be used for metallographic examination. The arbitration standard is based on the measurement method of surface microhardness distribution curve.


2, soft spots
Due to lack of heat, poor cooling and improper quenching, the phenomenon of insufficient surface hardness of seamless steel tube is called quenching point. Surface decarbonization can lead to surface wear and fatigue strength.