304不锈钢焊接接头火焰矫形后的晶间腐蚀分析

Analysis on Intergranular Corrosion of 304 Stainless Steel Welded Joint after Flame Straightening

304奥氏体不锈钢焊接接头在火焰矫形后耐腐蚀性下降,实际应用中产品发生提前腐蚀破坏。为确定火焰矫形后接头耐蚀性的薄弱区域,利用草酸电解腐蚀法进行晶界腐蚀试验,对比分析了焊缝、熔合线和母材的晶间腐蚀程度,并通过电子探针（EPMA）分析了接头不同区域C和Cr元素分布情况以确定碳化铬的析出程度。试验结果表明：火焰矫形后的304不锈钢焊接接头焊缝处晶界碳化铬析出最严重,耐蚀性最差;而熔合线耐蚀性优于焊缝,且碳化铬沿着纵向晶界析出;母材火焰矫形区出现不连续状的腐蚀点,但腐蚀点并不完全位于晶界处。

The corrosion resistance of 304 austenitic stainless steel welded joint decreases after flame straightening, and in actual application, corrosion failure of the products happen ahead of time. In order to determine the weak corrosion resistance area of the joint after flame straightening, the intergranular corrosion test was carried out by using oxalic acid electrolytic corrosion method, and the intergranular corrosion degree of weld zone, fusion line and base metal were analyzed.The C and Cr elements distribution in different regions of welded joint were analyzed by using electron probe（EPMA） to determine the precipitation extent of chromium carbide. The test results show that the chromium carbide precipitates most seriously at grain boundary of the weld zone in the 304 stainless steel welded joint after flame straightening and the corrosion resistance is the worst. The corrosion resistance of the fusion line is higher than that of the weld zone, and chromium carbide precipitates along the longitudinal grain boundary. The flame straightening zone of the base metal has discontinuous corrosion pits, while the corrosion pits are not completely located at the grain boundary.