Detail treatment of thick-walled seamless steel pipe processing
In the process of thick wall seamless steel pipe, there are many steps to obtain pipes with such high quality. Satisfactory metallographic structure can be obtained by eliminating work hardening of thick-walled seamless steel pipes. The process equipment is bright annealing furnace, mainly used for. The finished stainless steel is heat treated in a protective atmosphere. When the application performance requirements of the 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 be different.
After cold working, the residual stress of the thick-walled seamless steel pipe material remains, and the residual stress is very unfavorable to the stress corrosion cracking of the pipeline. Any degree of cold working can result in a significant increase in the material's resistance to stress corrosion cracking. The degree of cold working can also adversely affect the high temperature resistance of austenitic stainless steels. Generally, the higher the working temperature or the higher the fracture life requirement, the lower the degree of cold working.
It can be seen from the above introduction that the heat treatment process of thick-walled seamless steel pipes is quite troublesome. In order to obtain a qualified metallographic structure, the adjustment part of the cooling section equipment of the bright annealing furnace needs to be large. Therefore, the current advanced bright annealing furnace usually 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.
Thick-walled seamless pipes can be divided into three categories according to production methods: hot rolling (extrusion), welding and cold processing. Hot-rolled seamless steel pipe is a steel pipe that pierces and rolls a solid billet or ingot into a hollow section. The basic process is piercing and rolling. Cold-worked seamless steel pipe is the secondary processing of steel pipe (also includes secondary processing of thick-walled seamless pipe and thin-walled seamless steel pipe). Cold working is an important method to obtain high-precision, high-performance pipes, including cold rolling, cold drawing, cold tension reduction and cold spinning, etc. Extruded non-ferrous metal seamless pipes for high-alloy steel grades are mainly produced by extrusion.