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采用恒电位临界点蚀温度(CPT)法,利用OM,SEM,EDX和恒电位极化技术等研究了等离子弧焊接对双相不锈钢UNSS32304焊接接头微观组织及其耐点蚀性能的影响.结果表明,焊接接头热影响区和熔合区微观组织较母材相比发生了显著变化,两相比例严重失衡,铁素体所占比例均大于70%;两区域微观组织形态发生明显变化.且在铁素体晶粒内及两相相界处析出大量氮化物;焊接接头的耐点蚀性能明显下降,点蚀优先发生在高温热影响区所在的铁素体晶粒内.
The influence of plasma arc welding on the microstructure and pitting corrosion resistance of duplex stainless steel UNSS32304 welded joints was studied by means of constant potential critical pitting temperature (CPT) method, OM, SEM, EDX and potentiostatic polarization techniques. , The microstructure of HAZ and fusion zone of welding joint changed significantly compared with the parent metal, the ratio of two phases was seriously unbalanced, the proportion of ferrite was more than 70%, and the microstructure of the two regions changed obviously. A large amount of nitrides are precipitated in the grain and in the two phase boundaries. The pitting corrosion resistance of the welded joint obviously decreases. Pitting takes place preferentially in the ferrite grains where the high-temperature heat-affected zone is located.