Preventive measures for cold treatment of seamless steel tubes

A steel pipe made of a single piece of metal and having no seams on its surface is called a seamless steel pipe. Seamless steel pipes are mainly used as petroleum geological drilling pipes, cracking pipes for petrochemicals, boiler tubes, bearing tubes, and high-precision structural steel tubes for automobiles, tractors, and aviation.

Cold treatment method of seamless steel pipe may affect the performance of the seamless steel pipe, so we need to do some preventive measures when carrying out the seamless steel pipe cold treatment. The following small series introduces the preventive measures for the cold treatment of seamless steel pipe in detail:
(1) The seamless steel pipe is placed in boiling water for 30-60 minutes before quenching after quenching, which can eliminate 15%-25% quenching internal stress and stabilize the retained austenite, and then carry out conventional cold treatment at -60 °C. Or cryogenic treatment at -120 °C, the lower the temperature, the more the retained austenite transforms into martensite, but it is impossible to complete the conversion. Experiments show that about 2%-5% retained austenite remains, press It is necessary to retain a small amount of retained austenite to relax the stress and play a buffering role. Because the retained austenite is soft and tough, it can partially absorb the martensite sharp expansion energy and alleviate the phase transformation stress;

(2) After the cold treatment is completed, the seamless steel pipe is taken out and heated in hot water to eliminate 40%-60% cold treatment stress. After heating to room temperature, it should be tempered in time, the cold treatment stress is further eliminated, cold crack formation is avoided, and stable microstructure performance is obtained. Ensure that the seamless steel pipe products are not distorted during storage and use.