Published October 24, 2012
By Jeff Cobb
No doubt you’ve heard of lightweight “mag wheels?” And for that matter, you may know die-cast magnesium has been used in steering wheels, engine cradles and other components? The latest application for this super-light but challenging to work with metal is being touted by General Motors which has development a thermal forming process along with proprietary corrosion treatment for weight-saving sheet metal panels.
To shape the panels, the company says it has successfully developed a technique using heat of 842 degrees Fahrenheit (450 degrees Celsius) resulting in stamped forms that it says are precise, rigid, and will enable it to help meet economy requirements.
Magnesium weighs 33 percent less than aluminum, 60 percent less than titanium, and 75 percent less than steel, GM observes, and a rear deck lid it produced that weighs about 2.2 pounds (1 kg) less than a traditional steel counterpart has passed durability tests that included 77,000 robotic slams and 250-kilogram impact drops without any issues.
GM says also that by 2020, the United States Automotive Materials Partnership estimates 350 pounds of magnesium will replace 500 pounds of steel and 130 pounds of aluminum per vehicle. This could equate to weight reduction of 15 percent. This in turn would translate to a fuel savings of 9 to 12 percent.
But magnesium has traditionally been a challenge to treat against corrosion. GM said it overcame this hurdle by a proprietary treatment which it did not elaborate upon. The results however it is reporting, and these are that its thermal-formed magnesium has resisted 10 consecutive weeks of 24-hour environmental tests involving salt spray, 100-percent humidity and extreme temperatures.
“Like all of our advanced material vehicle parts, we subjected the magnesium trunk lid to the most severe strength and corrosion tests we know of, and it passed with flying colors,” said Jon Carter, GM R&D metals researcher. “We expect it to perform extremely well even in the harshest environments.”
The move toward magnesium is part of the company’s desire to expand global use low-mass parts, and it is seeking licensing agreements for its new technology.
“This innovative use of magnesium is just one example of how GM is leveraging breakthrough technologies that will benefit our customers around the globe,” said Jon Lauckner, GM chief technology officer and vice president of Global Research & Development. “Using high-strength lightweight materials such as magnesium and aluminum is one of the most effective ways to improve vehicle fuel economy and driving performance.”
GM R&D also announced "an industry first" aluminum welding technology, that's slated for production use as well, and in August it reported an investment in NanoSteel as well by its GM Ventures arm.
“Every gram of weight reduction matters when it comes to improving fuel economy,” said Greg Warden, GM executive director for global vehicle body engineering. “Being able to replace heavier metals with one of the lightest will help us deliver better fuel economy to customers around the world while also still providing the safety and durability they expect.”