Detailed treatment of thick-walled seamless carbon steel pipe processing
In the processing of thick-walled seamless steel pipes, many steps are required to obtain such high-quality pipes. By eliminating work hardening of seamless tubing, a satisfactory metallographic structure can be obtained. The process equipment is a bright annealing furnace, which is mainly used for. The finished stainless steel is heat treated in a protective atmosphere. When the application performance requirements of thick-walled seamless steel pipe are different, the requirements for the metallographic structure after bright annealing are also different, so the bright heat treatment process will also be different.
The residual stress of thick-walled seamless steel pipe material remains after cold working, and the residual stress is very unfavorable to stress corrosion cracking of the pipe. Any degree of cold working can significantly improve a material's resistance to stress corrosion cracking. The degree of cold working can also negatively affect the high temperature resistance of austenitic stainless steels. Generally speaking, the higher the working temperature or the higher the fracture life requirement, the lower the degree of cold work.
It can be seen from the above introduction that the heat treatment process of thick-walled seamless steel pipes is quite troublesome. To obtain a qualified metallographic structure, the equipment adjustment part of the cooling section of the bright annealing furnace must be very large. Therefore, the current advanced bright annealing furnace generally adopts strong convection cooling in its cooling section, and has three cooling sections, and the air volume can be adjusted independently. It is divided into three sections along the width of the strip.
According to the production method, thick-walled seamless steel pipes can be divided into three categories: hot rolling (extrusion), welding and cold working. Hot rolled seamless steel pipe is a steel pipe in which a solid billet or ingot is punched and rolled into a hollow section. The basic process is drilling and rolling. Cold-worked seamless steel pipe is the secondary processing of steel pipe (also includes secondary processing of thick-walled seamless steel pipe and thin-walled seamless steel pipe). Cold working is an important method to obtain high-precision and high-performance pipes, including cold rolling, cold drawing, cold drawing and cold spinning, etc. Extruded non-ferrous metal seamless pipes for high alloy steel grades are mainly extruded.
