Kaiser Aluminum’s motto is “Higher, Lighter, Lower”—higher strength, lighter weight, and lower processing cost. Those have been Kaiser’s technology drivers for 60 years.
Doug Richman, Vice President of Engineering and Technology, Kaiser Aluminum Corp., said that the first wave of reducing weight in vehicles involved the large castings: engines, cylinder heads, and wheels. “Aluminum has made good progress in penetrating those markets in the last 10 to 20 years, and that has reached the saturation point,” he said. “More than 60% of all engine blocks are aluminum, 100% of all transmission cases are aluminum, and 60% of all wheels.”
The move is now to take the benefits of lightweight aluminum to the next group of heavy components: suspension arms. Suspension arms represent collectively nearly 100 lb (45 kg) on a vehicle. Using aluminum, half of that weight can be reduced. Many suspension arms are cast today, but where extremely high strength is required, such as in the Chevrolet Corvette and other high-performance vehicles, forged arms are the choice. Most of these are still steel. Currently, about 15% of these are aluminum, but that is changing.
“In those markets, again the challenge is stronger, lighter, and less expensive,” Richman said. “We have a new alloy that is designed specifically for forged control arms—Alloy 7033. The main issue between forged and cast aluminum is that higher physical strength and higher fatigue life can be achieved in a forged product. If a vehicle demands very high strength in the part because of packaging, and they want the absolute lightest part, the higher structural integrity of forging the aluminum alloy can generally achieve a 10% weight savings over a casting.”
The typical alloy used for virtually all suspension arms and automotive components is 6061, or for European applications, 6082, which is the EU equivalent. Kaiser’s new 7033 is 60% stronger than 6061 in overall strength.
Richman explained that the 6000 series uses a magnesium silicide strengthener. The 7000 series of alloys are typically aerospace alloys and use zinc. The basic 7000 series of aluminum alloys, while very high strength, are rarely if ever used in automotive because they are susceptible to corrosion. They cannot stand up to the common environmental and road conditions required of vehicle components.
“Alloy 6061 is naturally corrosion-resistant,” Richman said. “But we wanted this added strength, so we combined some other elements along with the zinc for strength to the 7000 series to come up with 7033. From corrosion test evaluations at OEMs in the U.S., Japan, and Europe, it has been rated equal to 6061 in every corrosion test it has been exposed to. We’ve run a battery of tests, working with independent third-party labs, so there is no issue with the objectiveness of the testing.”
Alloy 7033 is 60% stronger than 6061, so the part designed using it can be both lighter and stronger. Richman said that they are seeing a 10 to 15% weight reduction compared to a well-designed forged 6061 part. That means less metal needs to be purchased, resulting in overall lower delivered cost of the part.
Kaiser developed Alloy 7033 but did not patent it; the company registered it with the Aluminum Association. “We have three parts we are producing using it today. Three years ago that was zero,” Richman said. “I would say it’s moving reasonably well into key automotive applications.”