Method for overcoming explosion defect of 4140 steel tubing hanger body

Abstract

The invention relates to a method for overcoming the explosion defect of a 4140 steel tubing hanger body. Firstly, a blank is heated section by section, then basic procedures are prepared, then die forging is carried out, then lime sand cooling is used for cooling, and finally a formed workpiece is subjected to quenched-tempered heat treatment. As the blank is slowly heated, the internal structureof the blank slowly changes, the effects of refining grain and homogenizing the structure are achieved, the actual grain size can reach a 7-10 level, and harmful structures such as a Widmannstatten structure generated by overburning and overheating are avoided. Due to the manner of die forging, too large surface stress triggered by hammer forging of free forging is avoided, sequential forging iscarried out in multiple directions, the fluidity of the blank is improved, and knife patterns and main cracks are avoided. During final quenching, the quenching cooling speed is reduced, the cooling speed of a martensite transformation region is reduced, thus, transgranular extension is avoided, structural stress of martensite transformation is reduced, and macroscopic cracks are avoided.

Description

technical field [0001] The invention relates to a method for overcoming the cracking defect of a 4140 steel oil pipe hanger body, and belongs to the technical field of workpiece forging. Background technique [0002] The 350 m3 4140 billet was forged with a 3t forging hammer to form the body of the oil pipe hanger. The forged billet of the hanger body was subjected to final quenching and tempering heat treatment after rough machining. In order to find out the cause of the defect, one of them was dissected and sampled for inspection. [0003] After investigation and research, it was found that the cracks on the main body of the pendant were ring cracks and longitudinal cracks coexisting, and the cracks were rigid and straight. The annular cracks are located at the transition arc of the steps and distributed along the circumference. The longitudinal cracks are connected with the annular cracks at the first large step and distributed along the radial direction. Regardless of...

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Problems solved by technology

[0006] Based on the above, in view of the macroscopic characteristics of the cracks on the main body of the pendant, the macro-microscopic morphology of the open crack fracture and the inspection results of the metallographic samples taken, there is a folding knife pattern defect at the transition arc of the steps of the main body of the pendant.

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