By John Huetter, Repairer Driven News on June 7, 2016
One of the most interesting elements of the lightweighting techniques used by General Motors and gobbled up recently by media at a recent event involves what reports described as the capacity to weld aluminum to steel.
“The aluminum-to-steel spot-welding system makes use of a uniquely designed welding tip patented by GM,” WardsAuto wrote May 19. “However, the tip fits with conventional tooling, so there is no need for specialized welding equipment. GM is expected to make the process available to other automakers interested in licensing the technology.”
Automotive News columnist Richard Truett observed that going mixed-materials with techniques like that allowed the automaker to build lightweight cars without spending $1 billion to retool plants for the aluminum F-150. (It should be noted that the F-150 isn’t purely “military-grade” aluminum — its frame is very proudly high-strength steel. Technically, the old Ford Escorts with steel bodies and aluminum bumpers were mixed-material.)
The CT6 is already in production and on sale, but GM plans to roll out the new process later this year to seatbacks and eventually the hood, according to the SAE publication Automotive Engineering. Not surprisingly, SAE’s article provides the best technical description of how all this works:
A specially-designed ridged electrode for the welding-gun tip is a key component of the system, said Blair Carlson, lightweight material processing lab group manager at GM Research & Development.
The advanced electrode (on the welder) helps to alleviate the physical-properties issues that to now have stymied steel-to-aluminum welding, including the 900º C delta in melting points between the two materials, formation of oxides on the aluminum component that compromise weld integrity and the tendency for a “glassy” layer to form between the two disparate materials, causing brittleness of the weld.
Carlson said cycle time before the welding-gun tip requires dressing currently is about 20 welds. The goal is to move the cycle into the hundreds …
Editor: Here is the link to read the full article: