目的：评价90SS和90SS-3Cr油管钢在H2S-CO2环境下的硫化物应力腐蚀开裂(SSCC)行为,并分析其断裂机理。方法利用四点弯曲实验和慢应变速率拉伸实验,结合显微组织分析、扫描电子显微镜分析技术,研究90SS和90SS-3Cr两种钢材在H2 S-CO2环境下的应力腐蚀开裂行为和断口形貌特征。结果90 SS-3 Cr钢的显微组织中存在更多的非金属夹杂物。经过720 h四点弯曲实验后,90 SS和90 SS-3 Cr试样表面均未出现宏观及微观裂纹,表现出良好的抗硫化物应力腐蚀开裂能力。在慢应变速率拉伸实验中,当H2 S浓度由0增加至6 mol/L时,90SS-3Cr试样的断后伸长率δ、断面收缩率ψ及断裂时间t分别下降了71.6%,69.6%,61.4%,远高于90 SS钢的塑性损失(分别下降2.9%,52.5%,10.3%)。断口形貌分析表明,90SS-3Cr钢在较低浓度H2 S时就由塑性断裂向脆性断裂转变。结论随着H2 S浓度的升高,90 SS和90 SS-3 Cr钢的塑性损失增加,抗SSCC能力均下降。相比90 SS钢,90 SS-3 Cr钢对应力腐蚀开裂更为敏感。
Objective To evaluate the sulfide stress corrosion cracking ( SSCC) behavior of 90SS and 90SS-3Cr tube steels in H2 S/CO2 environment, and determine the fracture mechanism. Methods The SSCC behavior and fracture morphologies of 90SS and 90SS-3Cr tube steels in H2S/CO2 environment were investigated by using four point bend test (FPB), slow strain rate test (SS-RT), microstructure and scanning electron microscope (SEM) analysis. Results For 90SS-3Cr, more non-metallic inclusions ap-peared in the microscopic structure. After the FPB test for 720 hours, there were neither macroscopic nor microcosmic cracks on the surfaces of 90SS and 90SS-3Cr specimens, which meant that they possessed a favorable SSCC resistance. However, the SSRT tests in-dicated that as the concentration of H2 S increased from 0 mol/L to 6 mol/L, the elongation, the reduction of cross section and the fracture time of 90SS-3Cr steel decreased by 71. 6%, 69. 6% and 61. 4%, which were much higher than that of 2. 9%, 52. 5% and 10. 3% of 90SS steel respectively. The fracture morphology analysis showed that the fracture of 90SS-3Cr steel transformed from duc-tile fracture into brittle fracture at lower H2 S concentrations. Conclusion The SSCC resistance of both 90SS and 90SS-3Cr tube steels decreased with the rising of H2 S concentration. 90SS-3Cr specimens were more prone to fracture than 90SS steel.
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