GMA welding of 9% Ni steel in pure argon shielding gas using coaxial multilayer solid wire

A coaxial multilayer solid wire was developed to perform stable gas metal arc welding of 9% Ni steel in pure argon shielding gas. This wire has a double structure consisting of an inner and outer part with different compositions. The average composition of this wire is similar to that of the wire for solid welding wire of 9% Ni steel. A potassium compound was added to the area between the inner part (center wire) and the outer part (hoop) of the wire to stabilize the welding in pure argon shielding gas. First, the wire melting behavior was observed with a high-speed video camera system. Then, the effect of potassium was confirmed experimentally. Next, the relation between the amount of potassium and the length of the column of liquid molten metal (CLM) was analyzed. The coaxial multilayer solid wire which contained more than 0.001 wt% potassium was able to shorten the CLM. Lastly, the welding was carried out in the V-groove to assess the ductility and strength of joints. The optimized coaxial multilayer solid wire that was developed and a constant current characteristics power source were used to obtain acceptable weld joints in pure Ar shielding gas.