Cracking Analysis on Welding Parts of Copper Pipe and Low Carbon Steel Pipe

A large quantity of cracking appeared in welding parts of the copper pipe and low carbon steel pipe. The cracking reasons were analyzed by means of macro examinaton on the cracking position, chemical compositions analysis, fracture observition by SEM and microstructure inspection. The results show that the comprehensive effect, which was induced the oxygen content in the material was over standard and grain boundary weakness by long time welding, made that the structural stress and thermal stress existed in the joint. The grain boundary cracked when the stress exceeded the limit of the material. The improved measures were also brought forward on the basis of analysis.