针对30CrMnSiA碰撞断裂样品，经宏观分析并采用扫描电子显微镜微观断口观察，配合能谱仪成分分析，及金相显微镜组织观察可知，断面原有陈旧性大裂纹，深达管厚一半，碰撞断裂起始于陈旧裂纹根部，是陈旧裂纹再扩展。主裂缝根部晶粒粗大，缝旁有大型氧化铝夹渣及点状内氧化物，缝边脱碳，陈旧裂纹形成与穿管有关。穿管裂纹与大型夹渣及局域粗晶，共同造成碰撞非正常断裂。其中，夹杂物和粗晶区域是管材断裂主要原因。
According to 30CrMnSiA of the fracture defects, scanning electron microscope(SEM)and optical microscope(OM) were used to observe and find large former crack in the fracture, crack deepness contains half of the tube, crack was originated from the former root crack, which is the former crack propagation. Because of the big grain in the root crack, alumina slag and decarburization nearby the crack, the crack is concerned with the pierced tube. Pierced tube crack, alumina slag and big grain cause improper breakage. And the rising temperature leads to the big grain and fracture.
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