WELDING DEVICE

PURPOSE:To suppress the error in the residual unbalance measurement due to thermal strain and improve the measurement work efficiency by carrying out air blow for a welded part during the time from the completion of the balance weight welding onto a propeller shaft, etc., to the completion of the residual unbalance measurement. CONSTITUTION:A propeller shaft 1 is revolved, and an unbalance part is measured by an unbalance measuring means, and a balance weight 3 is welded onto the unbalance part through the projection welding 4. A control means 9 opening-operates an electromagnetic opening/closing valve during the time from the completion of welding by a welding machine 4 to the completion of the residual unbalance measurement by the unbalance measuring means, and cooling air is jetted towards the outer peripheral surface of the shaft 1 from a pair of injection nozzles 81 and 81 of an air blow means 8 which are installed on the both sides of a lower part electrode 42. Therefore, the cooling of the welded part is markedly accelerated, and the variation quantity of unbalance due to thermal strain can be suppressed, and the time necessary for cooling can be greatly shortened.