An arc welding process for welding a circumferential surface of a fixed pipe etc. by shielding a work part with a shield gas is provided. It is welded by a flat arc formed in a flat sectional view by simultaneously ejecting a gas from nozzles (19) to the arc formed between a welding torch (10) and a product for welding by placing a pair of the gas nozzle (19) for ejecting the gas at the end of the welding torch (10).
A plasma welding method has successive steps including pre-heating of members to be welded, tack welding of the members for tentatively fixing these members, keyhole welding for completely welding the members to each other, and finish padding. These steps are automatically conducted by a single plasma welding apparatus operative in accordance with a programmed sequence including data concerning the optimum conditions of operation in each step in relation to the conditions such as sizes and materials of the members to be welded. The apparatus has a welding torch, a welding head on which the welding torch is mounted for rotation, a controller adapted for storing the optimum welding conditions for successive steps of the welding process in relation to the conditions of the members to be welded, a power supply system for transmitting welding current and welding speed signal to the welding head in accordance with a command provided by the controller, and a gas supply system for supplying a plasma gas at a rate determined in accordance with a command from the controller.
An electric rotating machine as disclosed herein includes an armature core having an outer peripheral portion with slots, a rotatable shaft having an outer periphery and rotatably supporting the armature core, a plurality of lower layer coils each having at opposite ends thereof respective lower layer coil protrusion portions, and a plurality of upper layer coils disposed radially outside of the lower layer coils and each having at opposite ends thereof respective upper layer coil protrusion portions. According to the novel method of this invention, the lower layer coil protrusion portions are bonded to the upper layer coil protrusion portions with a welding torch of an arc welding machine by radially moving at least one of the welding torch and boundary portions, at which the corresponding protrusion portions abut one another, relative to each other. By radially moving the welding torch and the boundary portions relative to each other, circumferentially adjacent bonded protrusion portions are smaller, mechanically stronger, and do not abut against one another.
