某304不锈钢编码器小轴在服役时发生断裂。采用宏观观察、化学成分分析、硬度测试、金相检验、扫描电镜及能谱分析等方法,对该编码器小轴断裂的原因进行了分析。结果表明:该编码器小轴断裂位置位于连接杆一侧的焊接热影响区;编码器连接杆一侧母材的碳元素含量偏高,组织中存在大量长条状非金属夹杂物,导致其力学性能较差,在较大的外力冲击作用下,该编码器小轴发生了脆性断裂。

The small shaft of a 304 stainless steel encoder broke in service. The cause of the encoder small shaft fracture was analyzed by means of macroscopic observation, chemical composition analysis, hardness test, metallographic examination, scanning electron microscope and energy spectrum analysis. The results show that the fracture position of the encoder small shaft was located in the welding heat affected zone at one side of the connecting rod. The carbon element content of the base metal at one side of the encoder connecting rod was relatively high, and there were large number of strip shaped non-metallic inclusions in the structure, resulting in poor mechanical properties. Under the impact of large external forces, the encoder small shaft had brittel fracture.