Cold metal transfer plus pulse (CMT+P) welding of G115 steel: Mechanisms, microstructure, and mechanical properties

Abstract

G115 steel is a prime candidate for key components in ultra-supercritical (USC) power plants. In this study, G115 welded joint of 15 mm thickness had been successfully fabricated using Cold metal transfer plus pulse (CMT + P) welding and the effect of heat input on microstructure and mechanical properties of G115 welded joint had been studied. The microstructure and mechanical properties were evaluated after PWHT (780 °C, 2 h). With the increase of heat input, the high temperature duration of welded joints increased, and the high temperature tempering effect increased, inducing more precipitates along grain boundaries and grains and thus enhancing the pinning effect of precipitates. Then the hardness and strength were improved 1.2 times and 1.1 times respectively as the heat input increased from 0.51 kJ/mm to 0.89 kJ/mm. However, as the heat input increased from 0.51 kJ/mm to 0.89 kJ/mm, the content of ferrite decreased, inducing the Charpy impact toughness was reduced by 50％.