Cold drawn seamless pipe control of rolling and cooling can reduce alloy consumption and reduce production costs, so in the production of seamless steel pipe is being promoted, and the initial formation of online regularization, on-line quenching, online rapid cooling and other processes.
1, Online regularization process
On-line regularization is also known as on-line normalizing, is in the hot rolling line after the rolling process, so that the steel pipe get the uniform microstructure of the process in the austenite phase air cooling or forced cooling.
The process consists of two phase change processes:
1) The cooling pipe is from 1100 ℃ to 550 ℃ below the steel austenite into ferrite + pearlite;
2) The seamless steel pipe by reheating after cooling, steel in the ferrite + pearlite and into austenite.
Through the online regularization, both can make steel uniform, grain refinement; can improve the comprehensive mechanical properties of seamless steel pipe.
2, On-line quenching process
1) Austenitic stainless steel tube
Austenitic stainless steel tube on-line quenching, also known as on-line solid solution, is the C element dissolved in austenite to form a single austenite. The solution temperature is generally 1000-1150 ° C. Cooling can be used water, oil, air cooling and so on.
2) Carbon steel, low alloy steel pipe
Refers to the use of rolling after the waste heat directly to the water quenching, and then on-line tempering treatment of quenching and tempering heat treatment process. Through this process can greatly save energy.
3, Online rapid cooling process
It is based on ultra-fast cooling technology as the core of a new generation of technology. Refers to the use of rolling after the use of rolling heat after the direct heat treatment process is to strengthen the cooling of the austenite after rolling, so that the metal in a very short period of time quickly cooled to near the ferrite phase transition temperature, thus inhibit the austenite grain growth, try to keep the austenite hardening state.
On-line rapid cooling in the improvement of seamless steel pipe organization, improve the comprehensive mechanical properties of seamless steel pipe, refine the surface grain, improve the anti-fatigue crack growth ability and so has obvious effect.
