Heat treatment common quality defects of seamless steel pipe

Seamless steel pipe in the heat treatment, there is thermal stress and tissue stress, this internal stress can be superimposed or partially offset, is complex and varied, because it can with the heating temperature, heating speed, cooling, cooling speed, parts shape and size changes, so heat treatment deformation is inevitable. Seamless steel pipe in the heat treatment process of mechanical collision will also cause deformation of parts, but this deformation can be improved with the operation to reduce and avoid.

1, Surface decarburization
Seamless steel pipe in the heat treatment process, if it is heated in the oxidizing medium, the surface will be the oxidation of parts of the surface to reduce the quality of carbon, resulting in surface decarburization. The depth of the surface decarburization layer exceeds the final processing of the amount will make the parts scrapped. Determination of surface decarburization depth The metallographic method and microhardness method can be used in the metallographic examination. The surface layer of micro-hardness distribution curve measurement method shall prevail, to do arbitration criteria.

2, Soft points
Due to lack of heating, poor cooling, quenching improper operation and other reasons caused by seamless steel pipe surface hardness is not enough phenomenon known as quenching soft point. It can cause surface abrasion and fatigue strength as a result of surface decarburization.