高炉大钟拉杆断裂原因分析

高炉大钟拉杆在工作过程中突然发生断裂，为了查明断裂原因，对拉杆头部的断口进行了宏微观分析和拉杆头部的材质解剖分析。分析结果表明，拉杆断裂的裂纹源位于表面R5过渡圆弧处，裂纹由表面向内疲劳扩展至断裂。表面裂纹萌生原因是拉杆在腐蚀性高炉煤气粉尘和轴向拉伸等工作应力的综合作用下，形成的应力腐蚀裂纹。建议加大R5过渡圆弧的尺寸，拉杆材质最好选用抗氧化性和耐腐蚀性较好的低碳低合金钢。

Fracture Analysis of a Large Bell Pull-rod of a Blast Furnace

A large bell pull-rod of a blast furnace （BF） suddenly fractured during the period of service. In order to find out the fracture cause, fracture surface examination and chemical analysis were carried out. The results show that cracks initiated at the surface of the turn angle, then propagated into the inner matrix, and eventually resulted in the fracture. The initiation of the cracks was caused by stress corrosion resulting from the co-effect of the corrosive gas dust and the axial tensile stress. It is suggested that the dimension of the turn angle should be enlarged and the pull-rod should be made of low-carbon low alloyed steels with better oxidation resistance and corrosion resistance.