20Mn2A圆链钢的鱼眼断裂分析

20Mn2A圆链钢在编链热处理后的拉伸试验中出现了断裂,在大多断口上发现有圆形或椭圆形平台。用扫描电镜、光学显微镜及直读光谱等仪器分别对圆链的断口形貌、组织、化学成分进行了分析。结果表明,圆链钢的化学成分正常,圆链的局部组织为回火马氏体和铁素体,铁素体组织的存在降低了圆链钢的硬度及耐磨性。圆链断口圆形平台的微观形貌为冰糖状沿晶形貌,平台中央有氧化铝类夹杂,这种以夹杂为核心的鱼眼状氢脆是引起圆链断裂的主要原因。

Fish-eye fracture analysis of 20Mn2A round chain steel

20Mn2A round chain steel was fractured in the tensile test after heat treatment of the braided chain, and round or oval platforms were found on most of the fractures. The fracture morphology, microstructure and chemical composition of the round chain were analyzed by scanning electron microscope, metallographic microscope and direct reading spectrometer. The results show that the chemical composition of the round chain steel is normal, and the microstructure of the round chain is tempered martensite and ferrite. The existence of ferrite reduces the hardness and wear resistance of the round chain steel. The micromorphology of the round platform on the steel fracture is crystal sugar-like intergranular morphology, and there are alumina inclusions on the central surface of the platform. The fish-eye hydrogen embrittlement with inclusions as the core is the main cause of the round chain fracture.