US Patent 7915560 TIG welding equipment and TIG welding methods

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.