Abstract: The TIG welding methods of the present invention include generating an electric arc between an electrode and an object to weld the object, wherein a first shielding gas including an inert gas flows toward the welded object surrounding the electrode, a second shielding gas containing an oxidative gas flows toward the welded object along a periphery of the first shielding gas, and the concentration of the oxidative gas in the second shielding gas is set such that the oxygen concentration in the welded metal portion of the welded object is within a range of 70 to 220 wt. ppm.

Abstract: The TIG welding methods of the present invention include generating an electric arc between an electrode and an object to weld the object, wherein a first shielding gas including an inert gas flows toward the welded object surrounding the electrode, a second shielding gas containing an oxidative gas flows toward the welded object along a periphery of the first shielding gas, and the concentration of the oxidative gas in the second shielding gas is set such that the oxygen concentration in the welded metal portion of the welded object is within a range of 70 to 220 wt. ppm.

Abstract: The object of the present invention is to achieve a deep weld penetration in a welded portion in metal by setting appropriate conditions for welding without deteriorating the quality of welding. That is, in the present invention, the weld penetration can be made deep by using a shielding gas comprising: 0.2% by volume or more (preferably 0.4% by volume or more) of oxygen gas; and the balance being helium gas, and by further setting the other welding conditions, such that the concentration of oxygen in the welded metal in the range of 70 to 700 ppm, and the scale ratio, i.e. the value D/W, can be made large. According to the present invention, a deeper weld penetration can be achieved without deteriorating the quality of welding by adopting at least one selected from the appropriate conditions of the welding current, the welding speed, and the arc length.

Abstract: A TIG welding equipment and a TIG welding method are described, capable of forming a welded metal portion deeply without lowering the welding quality, making the welding performance easier and improving the welding efficiency. The TIG welding equipment includes an electrode 2 for generating an electric arc 7 between itself and the welded object 10, a tubular inner nozzle 3 disposed surrounding the electrode 2, and a tubular outer nozzle 4 disposed surrounding the inner nozzle 3. A first shielding gas 8 composed of an inert gas can be supplied from the inner nozzle 3, and a second shielding gas 9 containing an oxidative gas can be supplied from between the inner nozzle 3 and the outer nozzle 4.