In this study, the oxygen contamination and the heat input on the anode surface were investigated by experimental measurements in order to guarantee a high-quality welding in TIG welding with a constricted nozzle. As a result, it was clarified that the energy density which was one of the heat source characteristics became higher at the center of the anode surface by attaching the constricted nozzle. Moreover, the oxygen concentration on the anode surface during TIG welding with constricted nozzle was as low as that during a conventional TIG welding. In addition, the oxygen concentration on the center of anode surface was changed by operating conditions such as a welding current and a shielding gas flow rate. Finally, the suitable welding condition was proposed from the tendency of the oxygen concentration on the anode surface, in which the oxygen concentration on the anode surface kept low.
