304不锈钢法兰焊接裂纹分析及返修

Analysis and repair of welding crack in 304 stainless steel flange

对检修过程中发现的304不锈钢焊缝裂纹及母材本体裂纹进行分析,焊缝存在较多的焊渣,以及根部未焊透是焊缝开裂的原因。母材的金相分析表明,304不锈钢晶界存在碳化物聚集,容易发生晶间腐蚀,引起母材开裂,焊接过程中,多层多道焊也容易使得热影响区晶间腐蚀加剧,引起母材开裂。304不锈钢锻造法兰的制造过程中应避免在敏化温度停留时间过长,固溶处理时应采取快冷的方式避免晶间腐蚀。焊接返修过程中,通过严格控制焊接层间温度,采用快速小热输入的工艺参数使得返修后的304不锈钢焊接质量检验合格。

The cracks in 304 stainless steel welds and base metal were analyzed during the overhaul,it was found that welding slag in the weld and lack of penetration were the reasons of cracking of welded joint. Metallographic analysis of base metal showed that carbides precipitate in grain boundary of 304 stainless steel,which likely results in the intergranular corrosion that could cause the cracking of base metal. During the welding process,the multi-pass welding easily caused the intergranular corrosion of heat affected zone,which can lead to cracking. During the cooling process after manufacturing of 304 stainless steel forging flange,it should be avoided remaining at sensitization temperature for too long time,and fast cooling after solution should be taken to avoid intergranular corrosion. The welded joint of 304 stainless steel was qualified by welding inspection after repairing by strictly controlling interpass temperature and low heat input during and fast welding.