Seamless Steel Tube Cold Treatment Cracks Preventive Ways

Seamless Steel Tube Cold Treatment Cracks Preventive Ways

The seamless steel tubes are mostly medium and high-carbon alloy steels. After quenching, a number of the subcooled austenite isn’t transformed into martensite, and it remains within the service state to become retained austenite, which affects the service performance. If it’s placed below zero to continue cooling, it can promote the martensite transformation of retained austenite. Therefore, the essence of cold treatment is to continue quenching. The quenching stress at temperature and therefore the quenching stress at zero are superimposed, and when the stack response force exceeds the strength limit of the fabric , cold treatment cracks are formed.

Precaution:

(1) After the seamless steel tube is quenched and cold treated, the seamless steel tube is placed in boiling water for 30-60 minutes, which may eliminate 15%-25% of the interior quenching stress and stabilize the retained austenite, then perform the traditional cold treatment at -60°C. Or perform -120℃ cryogenic treatment, the lower the temperature, the more the quantity of retained austenite transformed into martensite, but it’s impossible to finish the transformation. Experiments show that about 2%-5% of retained austenite remains. Press it’s necessary to retain alittle amount of retained austenite to relax the strain and play a buffering role. Because the retained austenite is soft and hard , it can partially absorb the energy of the rapid expansion of martensitization and ease the transformation stress;

• After the cold treatment is completed, the seamless steel tube is taken out and put in predicament to heat up, which may eliminate 40%-60% of the cold treatment stress. After the temperature is raised to temperature , it should be tempered in time. The cold treatment stress is further eliminated to avoid the formation of cold treatment cracks and acquire stable tissue performance. make sure that the seamless steel tube products aren’t deformed during storage and use.

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