CNG气瓶在不同H_2S浓度中的临界裂纹尺寸

CRITICAL CRACK SIZES OF CNG CYLINDER STEEL IN H_2S ENVIRONMENT

对3种不同的压缩天然气气瓶用钢4130X、30CrMo材料,在两种H2S环境溶液(高浓度2000×10-6和中等浓度200×10-6)中,采用改进型WOL试样,在测定材料室温K1C的基础上,用螺栓加载法,对22个试样测定了H2S环境下(室温)的临界应力强度因子KISCC.由此确定了不同材料在不同环境溶液中的临界裂纹尺寸,得到了气瓶工作压力及等效应力与临界裂纹尺寸的关系曲线.结果表明:几种材料的K1C值均较高,正常环境中都表现了良好的断裂韧性,但在H2S环境中,KISCC仅为K1C值的20%～40%.对于同样的4130X气瓶用钢,不同的供货来源,其KISCC值相差约30%,临界裂纹尺寸相差约80%.

Three groups of specimens of CNG cylinder steels, 4130X and 30CrMo, were tested in dense and moderate HES solutions. By using modified WOE specimens loaded with bolts, we obtained KISCC in HES environment, as well as KLC in air. The critical crack sizes of different materials in HES environment were thus figured out, and the curves with working pressures and equivalent stress to critical crack size were plotted. The results show that KLC of those specimens were all in a high level, thus with good fracture toughness in normal environment. However, KISCC in HES environment ranged from 20 % to 40 % of K LC- For two groups of specimens made of CNG steel 4130X but from different vendors, their KISCC are 30 % difference and their critical crack sizes are 80 % difference.