Application of seamless steel pipe: general-purpose seamless steel pipe is rolled from ordinary carbon structural steel, low-alloy structural steel or alloy structural steel.
According to different uses, it is divided into three categories: supply according to chemical composition and mechanical properties; supply according to mechanical properties.
Supplied by hydrostatic test. Steel pipes supplied according to categories a and b, if they are used to withstand liquid pressure, shall also be subjected to a hydrostatic test. Special purpose seamless pipes include seamless pipes for boilers, seamless pipes for chemical power, seamless pipes for geological use and seamless pipes for petroleum.
The seamless steel pipe should be boiled in boiling water for 30 seconds before cold treatment, which can effectively eliminate about 15% of the internal stress and stabilize the retained austenite.
Then, cold treatment can be carried out in a conventional manner. Of course, the second suggestion is to choose a regular treatment of minus 60 degrees, and then cryocooling at minus 120 degrees.
The lower the treatment temperature, the faster the retained austenite will be transformed into martensite, but not completely.
After experiments, it can be found that there will be about 2% retained austenite.
At this time, it is necessary to retain the retained austenite to achieve a certain buffering effect.
