Effect of shielding gas and heat input on microstructure and mechanical properties of deposited metal with 1 000 MPa grade welding wire for hydropower applications

Objective The purpose of this study is to apply gas metal arc welding wire of 1 000 MPa high strength steel in China, and to provide the basis for welding process of 1 000 MPa high strength steel for hydropower. Methods Four kinds of mixed gases with different ratios were used to test deposited metal, to determine the best ratio of protective gas with strength and toughness matching, and to study microstructure and mechanical properties of deposited metal with different heat input. Results When Ar content was 80%～95% in mixed gas protection, and mechanical properties of deposited metal could meet the requirements of 1 000 MPa welding materials for hydropower projects. When 90%Ar + 10%CO₂ mixture gas was used, strength and toughness matching performance of deposited metal was the best, and the properties of deposited metal met welding requirement of heat input between 15～35 kJ/cm, proportion of martensite decreased and proportion of bainite increased in the microstructure of deposited metal. Conclusion The study determines that HS-100S high strength steel gas metal arc welding wires of 1 000 MPa grade can meet the requirements for the properties of welding materials for hydropower projects. When shielding gas is 90%Ar + 10%CO₂ and heat input is 20～30 kJ/cm, it effectively ensures production efficiency, while deposited metal has excellent performance.