低碳钢及焊缝硝酸盐露点腐蚀开裂研究

用U形恒应变实验方法，研究了20 g、16MnR、Q235-A材及焊接材料浸泡在不同浓度硝酸铵溶液中的开裂敏感性，同时也讨论了硫的氧化物对硝酸盐露点腐蚀开裂敏感性的影响.结果表明：焊接材料比基材更易于发生硝酸盐露点腐蚀开裂，20 g比16MnR、Q235-A在硝酸盐中有更低的开裂敏感性，硫的氧化物增加了开裂敏感性.在此基础上，还探讨了硝酸盐露点腐蚀开裂的类型和机理.

DEW POINT CORROSION CRACKING OF LOW CARBONSTEELS AND THEIR WELD SEAMS IN NITRATE SOLUTIONS

Recently,dew point corrosion cracking has been found in catalytic cracking equipments in many refineries.The reasons are thought to be the joint actions of welding residual stress and the gaseous corrosive media of nitrogen oxides,sulphur oxides,water vapor etc.which condensed on the wall of catalytic cracking equipments.In this paper,the susceptibility to stress corrosion cracking (SCC) of steels of 20G,16MnR,Q235-A and their weld seams were studied in various NH-4NO-3 solutions by the U-shaped constant strain method.Based upon experiments the effect of sulphur oxides on the susceptibility to SCC and the cracking mechanism of nitrate dew point corrosion were discussed.The results showed that the susceptibility to nitrate dew point corrosion cracking of the weld seam is higher than that of the relevant matrix,the SCC susceptibility of steel 20G is lower than that of steels 16MnR and Q235-A and that the existence of sulphur oxides increases the SCC susceptibility.