Microstructure and properties of submerged arc weld metal of 1 000 MPa grade high strength steel

Welding wire and welding flux were designed for submerged arc welding of 1000 MPa grade high strength steel used in hydropower. JMat Pro software was used to simulate microstructure and mechanical properties of weld metal. Microstructure and mechanical properties of weld metal were evaluated by means of tensile test, impact test, OM, SEM and EDS. Effects of weld metal composition and welding heat input on microstructure and mechanical properties of weld metal were analyzed. The test results showed that the developed welding consumables had excellent welding process. Mechanical properties of weld metal were higher than standard values by controlling content of alloying elements. Effects of Cr content on microstructure and mechanical properties of weld metal were particularly analyzed. A small amount of Cr in weld metal would increase needle ferrite content, while a higher Cr content would increase bainite content, which resulted in increasing strength and first increasing and then decreasing impact toughness of weld metal. As welding heat input increased, acicular ferrite content of weld metal decreased and pre-eutectic ferrite content increased, microstructure was coarsened, and strength and toughness of weld metal decreased.