【作者】 卢志明；

【导师】 童水光；

【作者基本信息】 浙江大学 ， 化工过程机械， 2003， 博士

【摘要】 压力容器在湿硫化氢环境中的应力腐蚀开裂（SSCC）是一种发生频率较高，后果较为严重的破坏现象，特别是近年来随着我国原油深度开采和中东进口原油数量的增加，石油炼制业原料油中硫元素含量越来越高，使得湿硫化氢环境引起的应力腐蚀问题日益突出。国内外许多学者对硫化氢环境中的应力腐蚀问题已进行了大量研究工作，取得了一定的研究成果，但由于应力腐蚀影响因素众多，各种试验技术和对应力腐蚀机理的认识均带有一定的局限性，所以还存在许多问题值得深入研究和探讨。 本文选择了三种比较典型的压力容器用钢：低合金钢16MnR、低碳钢20g和奥氏体不锈钢316L作为研究对象，采用慢应变速率拉伸腐蚀试验和恒位移预裂纹断裂力学试验方法，研究了这几种钢材的在湿硫化氢环境中的应力腐蚀敏感性。在环境因素中，主要考虑了H₂S浓度、CI^-浓度、温度和PH值等介质参数单独或交互作用对应力腐蚀敏感性的影响。试验方案设计采用了均匀设计方法，将试验介质参数在各自取值范围内进行均匀散布组合，确定试验条件。材料因素方面主要分析了三种不同种类的钢以及同一钢种母材和焊缝的应力腐蚀敏感性的差异。通过试验数据的逐步回归分析，进一步揭示试验介质参数对应力腐蚀敏感性指数影响的显著性。在试验研究基础上，从微观角度提出了压力容器用钢在湿硫化氢环境中应力腐蚀的理论模型。综合上述试验和理论研究工作，本文得出下列几条主要结论： 1．16MnR钢慢应变速率拉伸腐蚀试验（SSRT）和应力腐蚀敏感性指数F（A）的回归分析表明，在湿硫化氢环境中，H₂S浓度（x₁）对16MnR应力腐蚀敏感性指数F（A）影响最为显著，其次是PH值（x₄），CI^-浓度（x₂）与F（A）之间没有显著的相关关系，温度（x₃）和H₂S浓度（x₁）将对F（A）产生交互作用。随着H₂S浓度的升高，16MnR应力腐蚀敏感性指数增大。表示16MnR母材应力腐蚀敏感性指数F（A）与试验介质参数之间关系的交互型数学模型为： F（A）=-14.5048+3.01×10^-2x₁+7.99x₄-2.51×10^-5x₁²+5.0×10^-4x_x3 有萝2.比较16MnR母材和焊缝的慢应变速率拉伸腐蚀试验结果发现，16MnR焊 缝的应力腐蚀敏感性高于母材。其主要原因是:焊缝的强度和硬度高于母 材;焊缝的金相组织均匀程度比母材差，且晶粒比较粗大;同时焊缝区域 的存在的较高焊接残余应力也会促进应力腐蚀裂纹的产生和扩展。3.恒位移预裂纹试样应力腐蚀试验显示，16MnR钢在炼制高硫原油常减压装 置的硫化氢环境中，应力腐蚀临界应力强度因子KlscC不大于 32MPa石， 此时应力腐蚀裂纹扩展速率约为10一4mm/h。4.209钢母材和焊缝在脱硫系统贫液、富液环境中应力腐蚀敏感性指数均较 低，试样断口上存在大量韧窝，应力腐蚀特征不明显。温度对209材料的 应力腐蚀敏感性影响相对较大，且随着温度升高，敏感性指数有所增大; 而贫液和富液中HZS浓度对应力腐蚀敏感性影响不大。5.316L钢的慢应变速率拉伸腐蚀试验和应力腐蚀敏感性指数F（A）回归分 析表明，在湿硫化氢环境中，Cl.浓度（xZ）和温度（x3）对316L的应力腐 蚀敏感性指数F（A）影响均较显著，PH值（x4）与F（A）没有显著的相 关关系，HZS浓度（xl）和温度（x3）对F（A）将产生交互作用。随着CI- 浓度和温度的升高，316L钢应力腐蚀敏感性指数F（A）增大。表示316L 应力腐蚀敏感性指数F（A）与试验介质参数之间关系的交互型数学模型为: F（刁）=一22.34+l.92x一。一2x2+5.8lx10一，x，+1.oxlo一x，x36.从微观的角度提出了钢材在湿硫化氢环境中的腐蚀导致局部塑性变形 （e000Sion Enhan。ed Plastieity Model，即eEPM）的应力腐蚀理论模型。 阴极反应产生氢原子通过渗透进入金属，并和位错发生交互作用，作用的 结果削弱了位错之间的相互作用力，促进了位错发射、增殖和运动，从而 加剧了局部塑性变形，导致微裂纹的形核和扩展。并提出了由初始氢浓度 和温度计算弱化指数的定量关系式。更多还原

【Abstract】 Stress corrosion cracking of pressure vessel in wet hydrogen sulfide service is a more often occurred damage phenomenon, which will lead to serious consequence. Especially for recent years, with the deeply oil exploiting in our country and increasing of the import oil from Middle-East area, there are more and more sulfide element in crude oil in refining industry, and it make the stress corrosion cracking in wet hydrogen sulfide service increasingly outstanding. A lot of researches on tress corrosion cracking in wet hydrogen sulfide service have been made all over the world, and some useful results are obtained, however, because of lots of factors which will effect stress corrosion cracking susceptibility, and with some limitations for all kinds of test technologies and understanding of stress corrosion cracking mechanism, there are many problems left need to be resolved and discussed.In this paper, the stress corrosion cracking susceptibilities of three typical types of pressure vessel steels: low alloy steel 16MnR, low carbon steel 20g and austenitic stainless steel 316L in wet hydrogen sulfide service are investigated, by slow strain rate test and constant strain pre-cracked specimen test. Among the environments factors, the separate and interaction effects of H2S concentration, CI-concentration, temperature and PH values on stress corrosion cracking susceptibilities are considered. The tests are designed by even design method, all parameters of medium are divided into several grade within its ranges and combined evenly. The discrepancies of stress corrosion cracking susceptibility between different types of steel, base matal and welds are analyzed. By stepwise regression analysis of test results, the notabilities of effect on stress corrosion cracking susceptive indexes of medium parameters are revealed. Based on experiment research, a micro stress corrosion cracking model of pressure vessel steel in wet hydrogen sulfide has been developed. The main conclusions of this paper are as follows: 1. The slow strain rate tests(SSRT) and the stepwise regression analysis of stresscorrosion cracking susceptibility indexes F(A) of 16MnR indicate that, in wet hydrogen sulfide service, the effect of H2S concentrations(x1) is most notable, PH value(x4) comes second, there is no notable correlativity between CF concentration(X2) and F(A), temperature(x3) and FbS(x1) play interaction role on the indexes F(A). With increasing of HS concentrations(x1), stress corrosion cracking susceptibility indexes of 16MnR steel increase. The interaction fitting equation of stress corrosion cracking susceptibility indexes F(A) of 16MnR base metal can be expressed:2. By comparing the slow strain rate test datum of 16MnR base metals with that of welds, it is found that the welds of 16MnR is more susceptible to stress corrosion cracking than the base metals. The main reasons are: the strength and rigidity of welds are higher than those of the base metals; the metallographic structures uniformities of welds are not good as the base metals, the crystals of welds are bulky; and the higher residual stress of welds region would also accelerate process of origin and propagation of stress corrosion crack.3. Constant strain pre-cracked stress corrosion tests of 16MnR steel in refining high sulfide content oil service are carried out, and it indicated that, thethreshold stress intensity factors KISCC are not higher than 32 MPa, and underthis load condition, the stress corrosion crack propagation rate is about 10-4mm/h.4. The stress corrosion cracking susceptive indexes of 20g base metal and welds in the saturated H2S solution and less saturated H2S solution of desulfuration system are low. There are lots of cavity on surface of microstructure fracture of specimen, stress corrosion cracking features are not obvious. The temperatures are more aggressive to stress corrosion cracking susceptibility than the other parameters, with the temperature increasing, susceptive indexes increase; however, the H2S concentrations of satu更多还原