Key points for controlling the heat treatment process of high-pressure seamless steel pipes
In the production process of seamless steel pipes for high-pressure boilers, heat treatment is a key process. Heat treatment has an important impact on the intrinsic quality and surface quality of seamless steel pipes. It is especially important for the production of alloy seamless steel pipes and has a long-lasting performance on high-pressure boiler pipes for power station boilers. The stable metallographic structure and good internal and external surface quality represent the manufacturing level of steel pipe enterprises. After the chemical composition of the steel pipe is determined, it is the heat treatment process that ultimately gives the steel pipe excellent mechanical properties and intrinsic structure. The ASME standard gives a wide range of process parameters, and production companies need to conduct on-site experiments to find the appropriate heat treatment process. The usual heat treatment process of T22: normalizing at 920℃-940℃, holding for more than 20 minutes; tempering at 720℃-740℃, holding for 2 hours.
Control of non-destructive testing of high-pressure seamless steel pipes
Generally, domestic boiler companies purchase high-pressure boiler tubes in accordance with GB5310 or company procurement regulations (ordering technical conditions). Non-destructive testing generally uses eddy current and ultrasonic automatic flaw detection. Steel pipes are required to undergo eddy current flaw detection one by one. The eddy current flaw detection method and acceptance standards are controlled according to the higher level of GB7735. ; Steel pipes are subjected to ultrasonic flaw detection one by one, and the flaw detection method is in accordance with GB5777. The acceptance standards for steel pipes of all specifications should meet the requirements of L2 level; the non-destructive testing of export pipes or steel pipes delivered in accordance with ASME SA-213 standards is controlled in accordance with SA-450. Ultrasonic thickness measurement and oblique flaw detection functions have begun to be configured in domestic automatic flaw detection equipment, which will better improve the performance of domestic equipment and effectively detect delamination defects in steel pipes.
