Gm Global Technolgoy Operations, Inc.

Warren D Hill

Gregory L Nagel

Anthony Lee

A method and apparatus are disclosed for resistance spot welding including applying a preconditioning pulse at the beginning of a welding process to stabilize the resistances at the interface of the sheets being welded and at the interface of the electrodes and the sheets. A current pulse is applied just after contact of electrodes and the workpiece when the electrode force is between about 10% and 75% of its final value to melt interface surfaces followed by a cooling time to permit dissipation of heat from the interfaces, and is finally followed by a conventional weld current schedule. The contact time is determined be electrically monitoring the conductivity between the electrodes as they are moved toward the workpiece. Alternatively, the applied electrode pressure is monitored to determine when sufficient electrode force is applied to the workpiece to achieve the proper resistance for the pulse application.

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Lake Orion, MI, United States of America

Warren D Hill