通过化学成分检测、低倍和显微组织观察、断口形貌分析及力学性能测试等手段, 对48MnV非调质钢曲轴断裂的原因进行了分析。结果表明：曲轴的失效模式为典型的疲劳断裂, 断裂源位于主轴颈与曲柄销之间的过渡圆角处, 断裂主要原因是曲轴钢中夹杂物过多; 裂纹源区条状硫化物较多, 曲轴表面有类似锻造流线形状的疏松缺陷, 易于产生疲劳裂纹; 裂纹沿条状硫化物及带状组织扩展, 最终导致疲劳断裂。

The fracture cause of the non-quenched and tempered 48MnV steel crankshaft was analyzed by the methods of chemical composition detection, macroscopic and microstructure observation, fracture morphology analysis and mechanical properties analysis. The results show that the failure mode of the crankshaft was a typical fatigue fracture. The crack source was located at the transition fillet between the main journal and the crank pin. Too many indusions in the crankshaft steel were the main reason for the fracture of the crankshaft. A lots of sulfides were observed at the crack source area and the porous defects with the shape similar to the forging streamline were found on the crankshaft surface, leading to an easy generation of fatigue cracks. The cracks propagated along the strip sulfides and banded structures, and eventually caused the fatigue failure.