5CrMnMo热挤压模具断裂失效分析

Fracture failure analysis of 5CrMnMo hot extrusion die

针对5Cr Mn Mo热挤压模具的断裂失效,通过分析模具结构及工作状况,结合金相显微镜、扫描电子显微镜、硬度测试等分析手段对模具的服役状况、宏观形貌和微观组织进行了研究。结果表明:模具的结构及受力特点产生的局部应力集中是模具出现断裂的主要原因,模具表面加工质量差、组织中存在一次碳化物且存在较为严重的带状偏析对模具的失效起到了加剧作用;粗糙表面磨损形成裂纹源,而粗大的碳化物和带状偏析降低了模具的韧性,在巨大的应力集中作用下裂纹迅速扩展,最终导致了模具沿晶脆性断裂。

For the fracture failure of 5CrMnMo hot extrusion die, the service circumstance, macroscopical morphology and microstructures were studied by analyzing the die structure and working conditions combining metallographic, scanning electronic microscope （SEM）, hardness testing and so on. The results show that the main reason for the die failure is the local stress concentration due to the structure and mechanical characteristics of the die. The ragged die surface and microstructural factors including large-size carbides in the die steel and serious banding segregation contribute to the die failure. The cracks source is formed on the ragged die surface due to wear and the impact toughness is reduced due to large-size carbides and the banding segregation, which result in rapid propagation of cracks under great stress concentration and then lead to the die＇s intergranular brittle fracture.