| 摘要 |
A base metal composed of a plurality of metallic materials having an oxygen content of 10 ppm is first preheated partly or overall. Then AC (alternating current) current is made to pass through the preheated base metal and an electrode so as to generate an arc for welding the metallic materials. The waveform of the current is changed with time between a peak current value and a base current value excluding a current of zero value only in one of plus and minus polarity sides of the current. A current ratio defined by dividing a current amplitude between the peak and base current values by a current average of the alternating current is a range of 0.5 to 2.0. The alternating current has a frequency of 500 Hz or higher.
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