超低碳奥氏体不锈钢焊接接头耐腐蚀性及环保型化学钝化工艺研究

Corrosion Resistance and Environmentally-friendly Chemical Passivation of Welded Joints for Ultra-low Carbon Austenitic Stainless Steel

采用不同配比柠檬酸钝化液对焊接接头进行化学钝化,借助电子背散射衍射(EBSD)和X射线衍射(XRD)对304L不锈钢手工电弧焊和氩弧焊两种焊接接头组织结构进行表征,借助电化学测试研究了焊接接头不同区域钝化后的电化学性能,通过X射线光电子能谱(XPS)分析了焊接接头化学钝化后表面钝化膜的成分。结果表明,焊缝区采用316L不锈钢焊丝进行填充,点蚀电位最高,母材区晶粒组织较均匀细小,耐蚀性相对较好;热影响区由于出现晶粒长大或混晶组织,点蚀电位最低。借助柠檬酸钝化液对焊接接头进行钝化,当钝化液浓度为10%,钝化时间为15 min时,点蚀电位最高,表面钝化效果最佳。

Plates of ultra-low carbon austenitic stainless steel 304 L were welded by manual arc welding and argon arc welding respectively with 316 L stainless steel as filler. The welded joints were characterized by means of electron backscatter diffraction(EBSD) and X-ray diffraction(XRD). Whilst the welded joints were chemically passivated in 10% and 20% hydrogen peroxide solutions respectively, then their corrosion behavior was examined via electrochemical means and X-ray photoelectron spectroscopy(XPS). Results showed that the pitting potential of the weld zone was the highest due to the incorporation of 316 L stainless steel welding wire. The corrosion resistance of the matrix was relatively good because its inherent microstructure of relatively uniform and small grains. The heat affected zone has coarse grains and/or mixed grain structure, so that its pitting potential was the lowest, correspondingly its corrosion resistance was the worst. In a word, the welded joints of austenitic stainless steel 304 L had the best corrosion resistance, when they were passivated in 10% hydrogen peroxide solution for 15 min.