超级双相不锈钢焊接接头的耐蚀性能

Corrosion resistance of superduplex stainless steel welded joint

通过SEM和EDS研究了采用不同焊接工艺后超级双相不锈钢UNSS32750焊接接头的两相比例及成分变化,并采用临界点蚀温度和浓硝酸法测试比较了不同焊接工艺接头的耐点蚀和晶间腐蚀性能.结果表明,焊接中较高的热输入、加填焊丝和背面采用氮气保护焊的方法可以稳定焊接接头中的奥氏体相的比例,并且较高的热输入,使得焊接接头冷却速度相对较慢,有助于铬的扩散而消除晶界贫铬现象,减小晶间腐蚀倾向;而与此相反的是较高的热输入,会导致两相中元素分配不均衡使铁素体相优先发生腐蚀,从而恶化材料的整体耐点蚀性能.

The changes of two phases proportion and element composition of superduplex welded joints stainless steels UNS S32750 welded joints by different technics were studied by SEM and EDS,meanwhile the pitting corrosion and intergranular corrosion resistance of welded joints were tested by critical pitting temperature (CPT) and 65% nitric acid solution experiment. The results showed that higher heat input,filling welding wire and nitrogen gas protection could make austenitic phase exist steadily,and higher heat input could make chromium to diffuse so as to reduce intergranular corrosion sensitivity which on the contrary make pitting corrosion worse. The reason is that the ferrite phase dissolves firstly because of the element partition disproportion.