Resistance spot welding method of aluminum material, control device of resistance spot welding of aluminum material, and resistance spot welding machine

A resistance spot welding method of sheets or plates of aluminum material, comprising, in the following order:

• sandwiching a plurality of sheets or plates of aluminum materials overlapped with each other between electrodes for spot welding;
• performing main energization to form a nugget between the sheets or plates of aluminum materials sandwiched between the electrodes;
• and
• performing pulsation energization in which energization between the electrodes and stop of the energization are repeated a plurality of times before the nugget is completely solidified, thereby forming, inside the nugget, a shell and a solidified portion of the aluminum material alternately from an outer edge portion of the nugget toward a nugget center portion in a cross section in an overlapping direction of the sheets or plates of aluminum material, the shell having a solidified structure different from that of the solidified portion of the aluminum material,
• wherein in the step of performing pulsation energization:
• a current value in the pulsation energization is set to be equal to or greater than a current value of the main energization,
• the energization and stop of the energization are repeated at least three times in the pulsation energization, and
• an energization stop period is gradually increased from a first half of the pulsation energization to a second half of the pulsation energization.