PURPOSE: To improve a joint strength and to stabilize a welding by using the resistance welding machine having a frequency converting device and by performing resistance welding with the welding current in the specified frequency range as well.
CONSTITUTION: The frequency converting device which can fluctuate the frequency of a welding current optionally is provided as well on a resistance welding machine. In case of welding the steel sheet coated with the paint containing conductive powders, the resistance welding is performed by setting the frequency of the welding current in the range of 100W1,000Hz via a frequency converting device. By performing the welding by using the welding current in this frequency range the resin part inside the film is burnt and its adhesion to the electrode and the welding time becoming longer can be prevented. In this way, the welding defect based on the current concentration to the conductive powder can be prevented. Consequently, the joint strength can be improved and the welding can be stabilized.
YAMAYOSHI KAZUO
MORI NAOTO
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