高钢级管线钢外部应力腐蚀开裂风险因素研究

Study on External Stress Corrosion Cracking Risk Factors of High-Grade Pipeline Steel

目前涉及到3个及以上风险因素的管线钢应力腐蚀研究还较少。为此,通过混合水平的正交试验法,采用慢拉伸试验研究了钢级、保护电位、温度、土壤环境等各敏感因素对高钢级管线钢应力腐蚀开裂行为的影响权重,并采用扫描电镜(SEM)观察了-1500 mV(vs CSE)保护电位下高钢级管线钢在近中性和高pH值模拟土壤溶液中的应力腐蚀行为。研究结果表明:管线钢外部应力腐蚀开裂风险在设置的试验水平因素中,保护电位对应力腐蚀指数ISSRT影响的权重最大,随后依次是温度、钢级及土壤环境;保护电位-1500 m V下,X70、X80管线钢在近中性和高p H值模拟土壤溶液中均具有较强的应力腐蚀敏感性,其SCC机制均为氢脆(HE)机制。

Nowadays,the researches on more than 3 risk factors which influenced stress corrosion cracking of pipeline steel have less been studied.In this work,the influence weights of various sensitive factors such as steel grade,protection potential,temperature and soil environment on the stress corrosion cracking(SCC)behaviors of high-grade pipeline steel were studied by means of orthogonal test at mixed level and slow strain rate test.Moreover,the stress corrosion behaviors of pipeline steels in simulated soil solution with near-neutral and high p H values under over-protection potential of-1500 m V were observed by scanning electron microscope(SEM).Results showed that among the experimental risk factors which influenced the external stress corrosion cracking of pipeline steel,the protection potential had the maximum weight in the stress corrosion index of ISSRT,followed by temperature,steel grade and soil environment.Under over-protection potential of-1500 m V,both X70 and X80 pipeline steel exhibited high stress corrosion sensitivity in simulated soil solutions with near-neutral and high p H values,and the SCC mechanism belonged to hydrogen embrittlement(HE).