METHOD OF CONTROLLING RESISTANCE WELDING

PROBLEM TO BE SOLVED: To maintain a nugget diameter to be formed within a proper range by suppressing the nugget diameter from reducing even when electrode abrasion progresses in resistance welding.SOLUTION: In a method of controlling resistance welding which pressurizes a plurality of materials to be welded 2 by a pair of electrodes 1a and 1b and welds them by performing power-control so that an instantaneous electric power value Pd to be supplied to a welding portion changes according to an electric power target pattern Pr, welding current Iw is energized by constant current control to perform test welding for forming a proper nugget before normal welding and a time change of the instantaneous electric power value Pd during the test welding is stored to form the electric power target pattern Pr. This allows to automatically form the electric power target pattern Pr to be a proper value. In this power control, even if electrode abrasion progresses, heat input amount to a material to be welded 2 is constant, so that the nugget diameter can be substantially maintained to be constant.