27MnCrV steel AC1 = 736 °C, AC3 = 810 °C, sub-temperature quenching heating temperature between 740-810 °C selected. Sub-temperature quenching selection of heating temperature 780 °C, quenching and heating of the holding time 15min; tempering temperature after the selection of 630 °C, tempering heating holding time 50min. Since the sub-temperature quenching is heated in the α+γ two-phase region, quenching is performed in the state where the retained ferrite is partially dissolved, and the toughness is improved while maintaining high strength.
At the same time, the low-temperature quenching is lower than the conventional temperature, reducing the quenching stress, thereby reducing the quenching deformation, thus ensuring the smooth operation of the heat treatment production, and providing a very good raw material for subsequent wire processing and the like.
At present, the process has been applied to the processing plant of Magnon Steel, and the warranty data shows that after heat treatment, the yield strength Rt0.6 of the steel pipe is 820-860MPa, the tensile strength Rm is 910-940MPa, and the impact toughness Akv is 65-85J. , The resistance to destruction is 100% qualified. The data shows that the 27MnCrV steel pipe is a very good high-grade casing pipe, 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.
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