Study on Quenching-and-tempering Process of Water-quenched 30Mn Steel

The continuous cooling transformation or CCT characteristics and hardenability of the 30Mn steel are investigated. The results show that when cooling rate is higher than 60℃/s, in the metallurgical structure of the specimen martensitic structure accounts for over 50%, and the hardenability is up to the requirement as set for oil well pipes with sizes under Ф 245mm×13.84 mm. Based on these data, further investigation is conducted, involving the law of the effect of different temper temperature & temper soaking time and the quench temperature & quench soaking time on the mechanical properties of the 30Mn steel. Accordingly, relevant lab quenching-and-tempering process is designed and performed experimentally, resulting in the conclusion that the mechanical properties of the 30Mn steel as quenched and tempered has met relevant requirements as specified in API Spec 5CT, and thus the 30Mn steel as a kind of water-quenched steel is applicable to the production of N80Q oil well pipes.