純Ar中でのGMA溶接を可能とする共金系9%Ni鋼用同軸複層ワイヤ

抄録

The coaxial multi-layer solid wire for 9% Ni steel have been developed to perform stable GMA welding in pure Argon shielding gas. This coaxial multi-layer solid wire has a double structure consisting of a different composition in its inner and outer parts. The average composition of this wire was the same level as the composition of the solid welding wire of 9% Ni steel. To stabilize the welding in pure Argon shielding gas, potassium compounds were used for this coaxial multi-layer solid wire. The potassium compounds were added between inner part (center wire) and outer parts (hoop). First, the wire melting behavior was observed with 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 column of liquid molten metal (CLM), which causes arc instability in pure Argon shielding gas, was analyzed. The coaxial multi-layer solid wire which contained potassium more than 0.001 wt % made the CLM shorten. As a result, the stable welding in pure Argon shielding gas was achieved. Lastly, the welding was carried out at V-groove to assess the ductility and strength of joints. The coaxial multi-layer solid wire which has appropriate composition and constant current characteristics power source were used. An excellent weld joint was obtained in pure Ar shielding gas. The Charpy absorbed energy was 89 J at 77 K (-196°C), 0.2% proof stress was 710 MPa and tensile strength was 855 MPa.