After adopting this heat treatment method, oil casing can effectively improve the impact toughness, tensile strength, and anti-destruction performance of oil casing, ensuring good value in use. Oil casing is an essential pipe for drilling oil and natural gas, and it needs to have good performance in use. Oil casing uses different temperature controls in different temperature ranges, and heating needs to be produced according to a certain temperature. For the AC1=736℃ and AC3=810℃ of 27MnCrV steel, the selected temperature for tempering after quenching should be 630℃, and the tempering heating holding time is 50 minutes; the heating temperature for sub-temperature quenching is selected between 740 and 810℃. The heating temperature for sub-temperature quenching is 780℃, and the holding time for quenching heating is 15 minutes. Because sub-temperature quenching is heated in the α+γ two-phase region, the quenching is carried out in a state where the local ferrite is not dissolved, and the toughness is improved while maintaining high strength.

The heat treatment of oil casing must be strictly implemented to ensure that the produced oil casing has excellent product quality and performance, can show good use value and performance in use, maintains high strength and toughness, and carries out heat treatment in different ways. At the same time, low-temperature quenching is lower than the conventional temperature, which reduces the stress of quenching and the deformation of quenching, thus ensuring the smooth operation of the production of oil casing heat treatment, and providing good raw materials for subsequent threading processing.

At present, this process has been applied in steel pipe processing plants of different steel pipes. The quality assurance data shows that the tensile strength Rm910-940MPa yield strength Rt0.6820-860MPa of the steel pipe after heat treatment is 100% qualified, and the impact toughness Akv65-85J data indicates that 27MnCrV steel pipe is already a high-quality high-grade oil casing. On the other hand, it also shows that the sub-temperature quenching process is an excellent method to avoid high-temperature brittleness in the production of steel products.