The tempering performance of low-alloy steel weldments

Abstract

High-energy piping systems are frequently fabricated from 1 2 Cr 1 2 Mo 1 4 V steel components joined by multipass 1 4 Cr1 Mo steel weldments. The creep behaviour of these weldments is then related both to the range of microstructures developed during manufacture and the effect of long-term, high-temperature exposure on microstructural changes. In the present work, laboratory aging experiments which simulate in-service tempering have been performed. Results indicate that for conditions equivalent to those encountered up to the nominal weldment design life, tempering effects are consistent with diffusion controlled coarsening of carbides. However, for more extreme situations, coarse grained ferrite of low hardness is developed within the weld heat-affected zone. The implications of these microstructural changes on high-temperature performance are discussed.