异质污染对316L不锈钢焊缝组织及耐蚀性影响的显色研究

目的 针对核电站管道焊缝中不明原因显色现象,设计了一种模拟工程现场引入异质污染的情形,研究异质污染对管道焊缝的影响.方法运用邻菲罗啉显色检测法,分别评价了以ER316L焊丝、掺杂了铁丝与铁粉的焊丝以及纯铁丝作为焊丝的316L不锈钢焊缝异质铁污染,结合能谱和动电位极化测试,分析了异质铁污染对焊缝组织和耐蚀性的影响.结果焊缝表面大面积持续显色主要为铁氧化物和焊缝中的富铁相,焊缝内部的点状持续显色为铁氧化物夹渣.在打磨条件下,无污染和富铁相作用下的焊缝,随空气放置时间的延长,显色程度a*逐渐降低,而点状显色没有明显改变,根据临界红色像素下临界色度(ac=5.3)时的积分面积百分比表明,点状显色的百分比低于1％,带状显色的积分面积百分比为20％～30％,ac=5.3时,显色开始显现.在3.5％NaCl溶液中,316L不锈钢焊缝的耐电化学腐蚀能力由大到小的顺序为ER316L+铁粉焊缝>ER316L焊缝>ER316L+铁丝焊缝>纯铁丝焊缝.结论铁污染的加入会导致显色现象更易产生,同时也会降低316L不锈钢焊缝的耐腐蚀性能.

Color Rendering Study of Effect of Heterogeneous Pollution on Weld Structure and Corrosion Resistance of 316L Stainless Steel

The work aims to design and simulate the introduction of heterogeneous pollution on site, study the effects of heterogeneous pollution on pipeline welds to solve the phenomenon of unexplained coloring in the pipeline welds of nuclear power plants. Orthophenanthroline color detection method was used to evaluate the heterogeneous iron contamination of 316L stainless steel welds using ER316L welding wire, welding wire doped with iron wire and iron powder, and pure iron wire. Combined with energy spectrum and dynamic potential polarization test, the effect of heterogeneous iron pollution on the structure and corrosion resistance of the weld seam was analyzed. The results showed that the continuous color development on the large surface of the weld was mainly iron oxide and the iron-rich phase in the weld, and the dot-like continuous color development inside the weld was iron oxide slag; under grinding conditions, the weld under the action of no pollution and iron-rich phase prolonged with the air storage time, and the color development degree a gradually decreased; while the dot color development did not change significantly; according to the percentage of the integrated area at the critical chromaticity (ac = 5.3) under the critical red pixel, when the percentage of dot color development was less than 1%, and the color development of band shape was 20%~30%, ac = 5.3, the color development began to appear. In 3.5% NaCl solution, the order of 316L stainless steel welds'' resistance to electrochemical corrosion was as follows:ER316L + iron powder welds > ER316L welds > ER316L + wire welds > pure iron wire welds. The addition of iron pollution will cause the color development phenomenon to occur more easily, and also reduce the corrosion resistance of 316L stainless steel welds.