12Cr1MoV/304不锈钢焊接接头高温时效碳迁移现象

Carbon migration phenomenon in high temperature aging process of 12Cr1MoV/304 welding joint

针对高温环境下异种钢焊接接头在服役过程中出现碳迁移,进而导致脱碳层在服役中失效的问题,采用电弧堆焊方法研究了12Cr1Mo V低合金耐热钢和304不锈钢焊接接头在不同时效时间下的碳迁移问题.研究表明,经高温时效后,焊态区域的组织并未受到影响;在过热粗晶区形成的碳过饱和的上贝氏体和粒状贝氏体组织则发生退化,转变成回火索氏体组织.形成的脱碳层组织以铁素体为主,里面夹杂少量的颗粒状渗碳体,特别是在增碳层出现大量的碳化物,形成类似于马氏体的复杂的不规则组织.经菲克定律推导出的扩散方程计算后,证明碳扩散的理论曲线与实际曲线较为接近,可用于研究碳扩散的迁移机制.

In order to solve the problem that the carbon migration will appear during the service of dissimilar steel welding joint and thus the failure of decarburization layer will occur under the high temperature environment,the carbon migration problem of 12Cr1 M o V lowalloy heat resistant steel and 304 austenitic stainless steel welding joint under different aging time was investigated with the arc surfacing method. The results showthat after the high temperature aging treatment,the microstructure of welding zone is not affected. The carbon supersaturated upper bainite and granular bainite formed in the overheated coarse-grain zone will degrade and transform into the tempered sorbite. The microstructure in the decarburization layer is mainly ferrite containing a small amount of granular cementite. Especially,a large amount of carbides appear in the carburized layer and the complex irregular microstructure alike the martensite forms. Through performing the calculation with the diffusion equation derived on the basis of Fick's law,it is proved that the theoretical curve of carbon diffusion is close to the actual one,which can be used to study the migration mechanism in the carbon diffusion process.