Effects of hot wire on mechanical properties of weld metal using gas-shielded arc welding with CO2 gas

In the fabrication of steel structures, the method of gas-shielded arc welding is widely utilized with pure CO2 gas. However, the welding with pure CO2 gas is limited with respect to the heat input in order to maintain the fixed mechanical properties of weld metal. A new welding method for increasing weld deposit in every weld bead under keeping the fixed mechanical properties of the weld metal is proposed. An electrically heated filler wire, hereafter referred to as hot wire, was inserted to the weld pool neighboring the arc formed with a leading welding electrode. By using a hot wire without arc, the increase in heat input could be suppressed, but the amount of weld deposit could be greatly increased. In the present investigation, the effects of the welding conditions on both the microstructure and mechanical property of the weld metal are clarified and discussed from the view point of the improvement of welding conditions. Mechanical properties of the weld metal formed with F-metal active gas (MAG) could be greatly improved under high heat input. The microstructure formed with F-MAG is so fine because of the change in the chemical composition of the weld metal by the use of the hot wire. The refined microstructure in F-MAG might improve the mechanical properties of the weld metal.