对洁净车轮钢在不同温度下进行正火处理, 得到不同晶粒尺寸的显微组织, 然后对车轮钢进行室温冲击试验, 利用扫描电镜对冲击试样断口形貌进行观察, 研究了夹杂物和晶粒尺寸对洁净车轮钢室温冲击韧度的影响。结果表明: 部分车轮钢冲击试样以夹杂物起裂, 夹杂物类型为Ti(C,N), 另一部分冲击试样断口起裂源处则未发现有夹杂物, 但尺寸在10 μm以下的Ti(C,N)夹杂物对车轮钢的冲击韧度没有明显的影响, 而晶粒尺寸对车轮钢的冲击韧度有明显影响; 其主要原因是室温下车轮钢冲击断裂的临界事件是微裂纹穿过晶界扩展引发解理断裂, 因此晶粒尺寸是决定洁净车轮钢冲击韧度的主要因素。

The cleaning wheel steel was heat-treated at different temperature to get microstructure with different grain size. Charpy V impact toughness of the wheel steel with different grain size was tested at room temperature. And the fracture surfaces were examined by scanning electron microscope with energy-dispersive X-ray spectroscopy. The results show that part of the impact specimens initiated from Ti(C, N) inclusions, and no inclusion was found on the other impact specimens’ fracture surfaces. Ti(C,N) inclusions with diameter less than 10 μm in the specimens didn’t decrease the impact toughness. The impact toughness of the wheel steel increased with the decreasing of grain size. The results relayed on the critical event of the impact cleavage fracture at room temperature was the micro-cracks propagating through grain boundaries.