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RESISTANCE SPOT WELDING METHOD

  • US 20160271720A1
  • Filed: 12/22/2014
  • Published: 09/22/2016
  • Est. Priority Date: 12/27/2013
  • Status: Active Grant
First Claim
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1. A resistance spot welding method to join parts to be welded by squeezing and pressing the parts between a pair of electrodes and passing current, the parts being a plurality of overlapping metal sheets, the method comprising:

  • performing test welding and actual welding in which a current pattern is divided into two or more steps, whereinin the test welding, a constant current of a different value is passed in each step, and a time variation of an instantaneous amount of heat generated per unit volume and a cumulative amount of heat generated per unit volume that are calculated from an electrical property between electrodes when forming an appropriate nugget are stored as a target value,in the subsequent actual welding, welding is started using, as a standard, a time variation curve of the instantaneous amount of heat generated per unit volume obtained by the test welding,when a time variation amount of an instantaneous amount of heat generated per unit volume deviates during any step of the actual welding from the time variation curve by a difference, a current passage amount is controlled in order to compensate for the difference during a remaining welding time in the step so as to match a cumulative amount of heat generated per unit volume in the actual welding to the cumulative amount of heat generated per unit volume that is determined in advance in the test welding, andin the test welding, 0.3×

    Ix

    Ia<

    Ix, where Ia is a current in a first step, and Ix is a current in second and subsequent steps.

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