The oil casing pipe is a large-diameter pipe that acts as a fixed oil and gas well wall or wellbore. The casing pipe is inserted into the wellbore and fixed with cement to prevent the wellbore from separating the formation and the wellbore from collapsing, and to ensure that the drilling mud circulates for drilling. Different types of casing pipe used in oil extraction: Surface oil casing pipe - Protects the well from contamination by shallow water and shallow gas, supports wellhead equipment and maintains the other layers of the casing pipe. Technical oil casing pipe - Separate pressures at different levels to allow normal circulation of the drilling fluid and protect the production casing pipe. Oil layer oil casing pipe - Exports oil and natural gas from the subsurface storage layer to protect the well and stratify the drilling mud. When producing oil casing pipes, the outer diameter is usually 114.3 mm to 508 mm.

27MnCrV steel has AC1=736°C, AC3=810°C, and the heating temperature during sub-temperature quenching is selected between 740-810°C. The sub-temperature quenching selects the heating temperature of 780 ° C, the quenching heating holding time is 15 min; the quenching and tempering selects the temperature of 630 ° C, and the tempering heating and holding time is 50 min. Since the sub-temperature quenching is heated in the α+γ two-phase region, quenching is performed while retaining a portion of the undissolved ferrite, and the toughness is improved while maintaining high strength.

At present, the process has been applied in steel pipe processing plants. The quality assurance data shows that the yield strength of the steel pipe after heat treatment is 820-860 MPa, the tensile strength Rm is 910-940 MPa, and the impact toughness Akv is between 65-85 J. 100% qualified. The data shows that the 27MnCrV steel pipe is a relatively high-quality high-grade oil casing pipe, and on the other hand, it shows that the sub-temperature quenching process is an excellent method to avoid high-temperature brittleness in the production of steel products.

At the same time, the low temperature quenching is lower than the conventional temperature, which reduces the quenching stress, thereby reducing the quenching deformation, thus ensuring the smooth operation of the heat treatment production, and providing a good raw material for the subsequent wire processing.