Patent ID: 6861609

Claim:
A method of forming spot welds in a workpiece of aluminum alloy sheet metal, each said workpiece comprising two or more layers of said sheet metal with each layer having thickness of from about 0.9 mm to about 4 mm or more, said method comprising: pressing two opposing copper or copper alloy electrodes on opposite sides of said layers of sheet metal to provide a contact force and electrical contact with said layers for said spot weld, said electrodes each having a round body with a diameter of at least 11 millimeters and terminating at one end in a round cone with a spherically crowned weld face surface, the diameter of said crowned weld face surface being in the range of 11 millimeters to the diameter of said body and the radius of said spherically crowned weld face surface being in the range of about 20 to 35 millimeters, and the surface of said crowned weld face surface having a texture; and passing a welding current between said electrodes to produce a spot weld nugget between said workpieces.