Failure Analysis of Dissimilar Steel Weld Cracking on High and Medium Pressure Guide Pipe

The hardness test and microstructure characterization were adopted to analyze the cracking failure of dissimilar steel weld cracking on high and medium pressure steam lead pipe. The materials of the cylinder, the guide pipe and the welding material were ZG15Cr2Mo1, 1Cr9Mo1VNbN and AWS 5. 11 ENiCrFe-1, respectively. The study showed that the hardness of the fusion line was higher than that of the adjacent base metal (ZG15Cr2Mo1) and nickel base welding, which was the weak area. The pressure pipe cracking is high temperature fatigue crack. The grains in the weld joint region were coarse, indicating that the welding specification is too broad and the time for welding remaining in the sensitized temperature zone is too long. The improper welding process was the main reason for the welding cracking of the high and medium pressure guide pipe.