厚壁型不锈钢管道应力腐蚀开裂及对策

对甲醇一氧化碳变换管道焊缝裂纹进行宏观和微观分析,对裂纹内腐蚀产物进行X射线分析,认为SUS304厚壁型不锈钢管道在焊接过程中焊缝区域极易产生微裂纹、敏化等缺陷,这是厚壁型不锈钢管道发生应力腐蚀开裂的重要内因;高温下含高水分、适量氧气、微量氯离子的水煤气介质是不锈钢管道产生应力腐蚀开裂的重要外因;而由于温差变动造成的热应力是管件疲劳开裂的另一个重要外因。采用铬钼低合金钢管道输送高温水煤气是适宜有效的,但其耐均匀腐蚀性较差,生产过程中宜加强监测,以确保安全。

Analysis of stress corrosion cracking of thick-wall stainless steel pipes and Countermeasures

Inorganic chlorides in crude oils are mainly sodium chloride, magnesium chloride, calcium chloride, etc. They can form hydrogen chloride by hydrolysis reaction in crude oil processing, leading to serious corrosion of the unit. The impacts of reaction conditions, reaction temperature, reaction time and water volume on the conversion of hydrolysis reaction of sodium chloride, magnesium chloride and calcium chloride are studied. The optimum hydrolysis reaction conditions and its possibilities of reaction in crude oil processing of inorganic chlorides are deduced. The results show that magnesium chloride, and calcium chloride may generate hydrogen chloride by hydrolysis reactions in crude oil desalting and distillation, while sodium chloride is difficult to hydrolyze. In addition, the hydrolysis conversion rates rise with rising reaction temperature and extending reaction time. The electro - static desalting process should be optimized to control the production of hydrogen chloride.