Stress corrosion cracking properties of 34CrMo4 high - strength steels, the material of compressed natural gas vessels in vehicle,were studied. In wet H2S environment,tension tests of compact tension (CT) specimens of 34CrMo4 steel were carried out at the displacement rate of 5 x 10-5mm/s. The critical stress intensity factor and crack growth rate were gotten in different concentrations of hydrogen sul-fide solution (20,63 ,200,630 and 2000 ppm) . The results show that KISCC decreases with increase of the concentrations of hydrogen sulfide, but the influence of the concentration on KISCC changes very little when hydrogen sulfide concentration reaches a certain value; da/dt increases with the increase of the concentrations of hydrogen sulfide, then while the influence of the concentration on crack growth rate is very little from 630 to 2000 ppm.%以车载压缩天然气气瓶用钢34CrMo4为材料,试样为紧凑拉伸(CT)试样,采用多功能动态应力腐蚀试验机进行恒位移速率拉伸试验,实测了在20,63,200,630和2000 ppm的硫化氢水溶液中的应力腐蚀临界应力强度因子KISCC和裂纹扩展速率da/dt.结果表明,应力腐蚀临界应力强度因子KISCC随硫化氢浓度的增大而减小,但当硫化氢浓度达到一定量时,溶液的浓度对KISCC值的影响并不大；裂纹扩展速率da/dt随硫化氢浓度的增大而增大,但在630～2000ppm范围内,硫化氢浓度对裂纹扩展速率影响很小.
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