高温时效对异质接头碳迁移和组织的影响

Influence of High Temperature Aging on Carbon Diffusion and Microstructure of Dissimilar Joints

电站锅炉的对流管束通常使用奥氏体不锈钢与低合金耐热钢的焊接,两种材料在成分和组织上明显不同,异质接头在高温服役中会发生碳迁移现象,形成一个增碳区和脱碳区,对异质接头进行500℃/100h高温时效处理,观察熔合线两侧成分和组织的变化,结果表明,在高温时效处理后,在熔合区碳含量增加并且析出大量碳化物,焊态下母材热影响区粒状贝氏体和上贝氏体退化,转变成铁素体和索氏体。

The welding of austenitic stainless steel with low alloy heat-resistant steel was usually used in the connection of convection tubes which can be found in power station boiler. These two materials were significantly different in the composition and organization. The carbon may diffuse if the two dissimilar joints were in the high temperature conditions, forming a recarburization zone and a decarburization zone. After the aging treatment for the dissimilar joint at 500 ℃/100 h and observing the changes of the composition and the microstructure on both sides of the fusion zone, The result show that, after the aging time, the carbon content increased in the fusion zone and a large number of carbide precipitated, granular hainite and upper bainite in the base material under welding degraded and transformed into ferrite and sorbite.