Greep behaviour of X20CrMoV12·1 welded joint

By a newly developed test method, the constant strain rate (CSR) test method, the creep behaviour of X20CrMoV12·1 pipe girth welds was studied with particular emphasis on the effect of welding conditions and type of filler metal. It was shown that the creep resistance of the welded joint is lower than that of the base metal and the weld metal as well, and is not affected by the change in preheating temperature, number of times of postweld heat treatment and even the type of filler metal. The outer part of the fine grained HAZ, the so called "type IV" zone, possesses the least creep strength. It is necessary to take into account of a welding efficiency factor in a design procedure if the combind axial stress due to internal pressure and system stresses is permitted to be equal to the hoop stress in the pipe.