The seamless expansion of the seamless steel tube
is divided into an overall thermal expansion treatment, a surface thermal expansion treatment, and a chemical heat treatment. The seamless expansion of the seamless steel pipe is generally treated by integral thermal expansion. Generally, they are subjected to basic processes such as heating, heat preservation, and cooling, and defects may occur in these processes.
Heat treatment defects of seamless steel tubes mainly include unqualified structural properties of steel pipes, excessive size and surface cracks, scratches, severe oxidation, decarburization, overheating, and over-burning.
Features of thermal expansion processing of seamless steel tubes:
The first process is heating: one is heating below the critical point Ac1 or Ac3; the other is heating above the critical point Ac1 or Ac3. The first is mainly to stabilize the structure of the seamless steel pipe and to eliminate the residual stress of the seamless steel pipe, and the second is mainly to austenitize the steel.
The second process is thermal insulation: the purpose is to uniformly heat the heating temperature of the steel pipe to obtain a reasonable heating structure.
The third process is cooling: the cooling process is a key process in the heat treatment of seamless steel tubes. He determines the metallographic structure and mechanical properties of the tubes after cooling. The steel tube cooling methods used in the actual production process are various. The cooling methods often used are furnace cooling, air cooling, oil cooling, polymer cooling, and water cooling.