【摘要】 用扫描电镜 (SEM )分析了X70管线钢在模拟高 pH值 (pH =9 3)土壤介质 0 5mol/LNa2 CO3+1mol/LNaHCO3的碳酸盐溶液中 ,循环载荷下的裂纹断口形貌。结果表明 :(1)在高应力比 (R =0 9)下 ,静载拉伸力学因素在断裂机制中占主导地位 ,断口的大部分呈现静载断裂特征 ,随着应力比R的降低 ,断口呈现疲劳断裂特征 ;(2 )随着加载频率的降低 ,断口MnS夹渣的数量和密度明显增加 ;(3)由于X70管线钢的晶粒很细小 ,在碳酸盐溶液中的断口并没有呈现典型的晶间断裂冰糖状断口形貌。更多还原

【Abstract】 The crack fractographs of X70 pipeline steel in the synthetic high pH (pH = 9.3) soil solution 0.5 mol/L Na2CO3 + 1 mol/L NaHCO3 under cyclic loading are investigated by the SEM. The results indicate that at high stress ratio (R =0.9) the static state tensile mechanics is the dominant factor in the fracture mechanisms. With the decrease of the stress ratio R, the fractograph presents evident fatigue fracture characteristic. The amount and density of MnS inclusion evidently increase with the decrease of the loading frequency. Because of the smaller grain of X70 pipeline steel, the typical intergranular fracture characteristics have not found.更多还原