27MnCrV is a new type of steel for the production of TP110T steel grade oil
casing pipe sleeves. The conventional production of TP110T steel grade oil pipe sets is 29CrMo44 and 26CrMo4. Relative toThe latter two, 27MnCrV contains less Mo element, which can greatly reduce production costs. However, after the production of 27MnCrV by normal austenitizing quenching process, there is obvious high temperature temper brittleness, resulting in low impact toughness and instability. Solving such problems is usually handled in two ways: First, the method of rapid cooling after tempering avoids high temperature brittleness and obtains toughness. Second, the sub-temperature quenching method improves the toughness by effectively improving the harmful elements and impurities through incomplete austenitization of the steel. In the first method, the heat treatment equipment is relatively strict and requires additional costs.
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 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.
The process has been applied in the pipe processing plant of Tianjin Pipe Group. The quality assurance data shows that the yield strength of the steel pipe after heat treatment is 820-860MPa, the tensile strength Rm is 910-940MPa, and the impact toughness Akv is between 65-85J. The anti-destructive performance is 100% qualified. The data shows that the 27MnCrV steel pipe is a relatively high-quality high-grade oil casing, 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.
