Eliminating method for tempered seamless steel pipe residual stress and adopted bi-directional chain type cooling bed

Abstract

The invention provides an eliminating method for tempered seamless steel pipe residual stress and an adopted bi-directional chain type cooling bed. A straightening working procedure is adopted beforetempering, and the straightness accuracy of a steel pipe before tempering is ensured; the bi-directional chain type cooling bed with the gradient is adopted, the steel pipe is constantly rotated in the cooling process after being tempered, the straightness accuracy of the steel pipe in the cooling process after tempering is ensured, and therefore it is ensured that the steel pipe is not subjectedto stress relief annealing after being tempered and residual stress does not exceed 3% of the specified minimum yield strength while the straightness accuracy reaches 1 mm / m or below. The gradient ofa bed boy of the bi-directional chain type cooling bed is 2-5 degrees, the bed body is provided with the lower front portion and the higher rear portion and formed by alternately arranging multiple forward chains and multiple reverse chains at intervals, the forward direction of the forward chains is the same as the movement direction of the seamless steel pipe, and the forward direction of the reverse chains is opposite to the movement direction of the seamless steel pipe. By means of the eliminating method, the technical effect of achieving straightness and low residual stress simultaneouslyis achieved, the working procedure of stress relief annealing is omitted, the production cost is reduced, and the surface quality of the steel pipe is improved.

Description

technical field [0001] The invention belongs to the technical field of heat treatment, and in particular relates to a method for eliminating the residual stress of a quenched and tempered seamless steel pipe and a two-way chain cooling bed used for eliminating the residual stress of the quenched and tempered seamless steel pipe. Background technique [0002] Residual stress will reduce the fatigue strength of the material, affect the collapse strength, increase the stress corrosion of the pipe body, and at the same time, there will be processing deformation during material processing. Therefore, in the fields of construction machinery, automobiles, oil and gas exploration, the residual stress of seamless steel pipes is generally The requirement shall not exceed ±5% of the specified minimum yield strength for the material. [0003] After quenching and tempering, the straightness of the seamless steel pipe must be guaranteed, and usually it will be straightened after quenching...

AI Technical Summary

Problems solved by technology

According to the requirements of API5C3 and related technical standards of users, the lower the straightening temperature, the greater the residual stress of the steel pipe. Generally, the steel pipe of L80-Q125 steel grade should be straightened by hot roller after quenching and tempering. The temperature of the steel pipe after straightening should be above 510 °C , if the straightening temperature of the steel pipe is lower than 510°C, the residual stress of the steel pipe will be large, and stress relief annealing is required to eliminate the residual stress. The better), it is difficult for most materials to meet the straightening temperature requirements when straightening, and stress relief annealing treatment is required after straightening. Stress relief annealing not only increases the scale on the surface of steel pipes, but also occupies quenching and tempering capacity, resulting in cost increases

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