利用光学显微镜和扫描电镜观察以及硬度测试等方法对某ZG42CrMo引锭杆链节的断裂原因进行了分析。结果表明: 由于该链节感应淬火工艺控制不当使得表面淬硬层硬而薄且与基体之间的硬度梯度过大, 导致链节在受到压应力作用时表面淬硬层首先发生脆裂产生小裂纹; 加之链节铸态组织过热、调质处理时淬火温度偏低造成基体显微组织中存在大量的网状铁素体和魏氏组织, 使得基体材料硬度偏低、韧性降低, 从而导致表面已形成的小裂纹由链节角部应力集中区快速向中心孔方向扩展, 引发引锭杆链节脆性断裂失效。

Means such as optical microscope and scanning electronic microscope observation and hardness testing were used to analyze the fracture reason of a ZG42CrMo chain link of dummy bar. The results show that because of the improper induction quenching, surface hardened layer of the chain link was hard and thin and hardness gradient from the surface to the matrix was steep, which resulted in the formation of little cracks first at the surface hardened layer when receiving pressure stress. At the same time, because the as-cast structure was overheated and quenching temperature was low, there were lots of network ferrite and Widmannstatten structure in the microstructure of the chain link, which resulted in the decrease of hardness and ductility of the matrix material. So the little cracks haven formed on the chain link surface expanded rapidly from the corner stress concentration area to the center hole and led to brittle fracture failure of the chain link of dummy bar.