Automatic surfacing method and surfacing tool for sealing surface of nuclear-grade small-caliber valve

The invention discloses an automatic surfacing method and a surfacing tool for a sealing surface of a nuclear-grade small-caliber valve, a hot wire argon tungsten-arc welding method is adopted, and the automatic surfacing method comprises the following steps: S1, a valve to be welded is mounted on a working turntable, and a welding wire is connected with a wire feeding heating power supply; s2, controlling the working turntable to rotate for at least one circle without feeding a welding wire, and carrying out air melting for the first time, so that the sealing surface to be surfaced is preheated to a preset temperature; meanwhile, the welding wire is preheated; s3, the welding time of the first surfacing layer and a needed welding wire are determined, the working rotary table is controlled to rotate by one circle, meanwhile, the welding wire is automatically pushed, and welding of the first surfacing layer is completed; during welding, the preheated welding wire is in contact with a molten pool so as to conti