General Motors Says Solved Hurdle to Spot-Welding Aluminum

The trend toward vehicle light-weighting has auto makers looking to use more and more aluminum, in turn forcing them to discover new bonding techniques.

Honda earlier revealed it is using a new process, dubbed friction stir welding, to mate aluminum to steel in the front subframe of its new Accord, and General Motors says today that it has developed an industry-first way to weld aluminum with aluminum.

The Detroit auto maker’s new resistance-spot-welding technique uses a patented multi-ring domed electrode to reliably mate two pieces of aluminum, rather than a smooth electrode, which GM says produces uncertain results.

“No other auto maker is spot-welding aluminum body structures to the extent we are planning to, and this technology will allow us to do so at low cost,” says Blair Carlson, manufacturing systems research lab group manager.

Being able to weld instead of fasten means the nearly 2 lbs. (0.9 kg) of costly self-piercing rivets typically employed to join aluminum can be purged from hoods, liftgates, doors and other parts where the metal is being used increasingly. Eliminating the rivets also makes the vehicle easier to recycle, the auto maker says.

GM already uses the welding process for the hood of the Cadillac CTS-V and liftgate for the hybrid versions of the Chevrolet Tahoe and GMC Yukon, but will expand applications “extensively” beginning next year.

“The ability to weld aluminum body structures and closures in such a robust fashion will give GM a unique manufacturing advantage,” Jon Lauckner, GM chief technology officer and vice president-global research and development, says in a statement.

“It is an important step forward that will grow in importance as we increase the use of aluminum in our cars, trucks and crossovers over the next several years.”

The new welding technique works on sheet, extruded and cast aluminum, GM says, crediting the multi-ring domed electrode head’s ability to disrupt the oxide on the aluminum’s surface to create a stronger weld.

The auto maker says it may be willing to license the technology, including to other automotive companies.