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37Mn5钢是生产J55级石油套管的专用钢种。本文采用着色渗透检验、光学显微镜、SEM及EDS等手段对调质处理后37Mn5热轧钢内壁裂纹的形貌、非金属夹杂物与显微组织、断口形貌等进行研究并分析裂纹的形成原因。结果表明,非金属夹杂物为硫化物,其粗细等级为1.5级;内壁裂纹较短,深度较深,裂纹基本垂直于内壁,裂纹尾端尖锐、细小,且裂纹内部存在氧化物并有氧化脱碳现象,经EDS分析该氧化物为氧化铁,说明该裂纹为非淬火裂纹,由此推断该裂纹是在穿轧时形成,并在淬火应力作用下进一步扩展形成一定深度的纵向裂纹。
37Mn5 steel is a special steel grade for the production of grade J55 oil casing. In this paper, the morphology, non-metallic inclusions, microstructure and fracture morphology of 37Mn5 hot-rolled steel after quenched and tempered were investigated by means of color penetrant test, optical microscope, SEM and EDS. The results show that the non-metallic inclusions are sulfides with a grade of 1.5, the inner wall cracks are short and the depth is deep, the crack is almost perpendicular to the inner wall, the crack tip is sharp and small, and the oxide exists inside the crack and oxidizes Carbon, the EDS analysis of the oxide is iron oxide, indicating that the crack is non-quenching crack, infer that the crack is formed in the wear rolling, and further expand the quenching stress to form a certain depth of longitudinal cracks.