某H13钢铝型材挤压杆在正常使用过程中发生断裂失效，采用化学成分分析、断口宏微观分析、金相检验、硬度测试等方法，对挤压杆断裂失效的原因进行了分析。结果表明：该挤压杆杆身与杆座之间的过渡圆弧误加工成退刀槽而形成应力集中，且挤压杆回火不充分，有较高的残余内应力，显微组织不稳定，偏析组织产生附加组织应力及各向异性，使得退刀槽棱边萌生裂纹，在安装引起的偏心载荷作用下，导致挤压杆在服役初期即产生弯曲疲劳断裂。

Fracture failure of an H13 steel extrusion rod for aluminum section occurred during normal operation, the causes of fracture failure were analyzed by means of chemical composition analysis, fracture macro and micro analysis, metallographic examination and hardness test. The results show that the transition arc between the extruded rod body and the rod seat was mistakenly processed into the run-out groove and formed stress concenfration. The extrusion rod was not fully tempered, and had high residual internal stress. The microstructure of the extruded rod was unstable, and the structure stress and anisotropy were produced in the segregation structure, which caused cracks in the edge of the run-out groove. Under the installation eccentric load, the bending fatigue fracture of the extruded rod occured in the initial stage of service.