Influence of carbon content on microstructure and mechanical properties of 1000 MPa deposited metal by gas metal arc welding

The effects of carbon content (0.078–0.100 wt.%) on the microstructure and properties of 1000 MPa grade deposited metal produced by gas metal arc welding have been investigated. Experimental results show that the microstructure of the deposited metal was mainly composed of martensite, bainite and retained austenite. With increasing carbon content, the proportion of martensite increased, and the amount of bainite was reduced. High carbon content is beneficial to strength, but harmful to impact toughness, and thus, carbon reductions lead to the increase in impact toughness. When the carbon content was 0.100 wt.%, the lowest Charpy absorbed energy of 47 J at − 40 °C for the deposited metal was achieved, the highest yield strength of 1038 MPa was attained, and the yield-to-tensile ratio was more than 0.88, while the highest Charpy absorbed energy of 55.7 J at − 40 °C and the lowest yield strength of 915 MPa were obtained when the deposited metal contains 0.078 wt.% C, and the yield-to-tensile ratio was less than 0.85. It is concluded that bainite fraction and fine effective grain size were the dominant factors to achieve good comprehensive mechanical properties (the required strength and an acceptable toughness) of deposited metals with various carbon contents.