GM to use lightweight magnesium sheet metal

Car maker says double-digit fuel economy gains possible with more substitution for steel and aluminum

Comments Off on GM to use lightweight magnesium sheet metal October 23, 2012
by Design Engineering Staff

General Motors announced it is testing an industry-first thermal-forming process and proprietary corrosion resistance treatment for lightweight magnesium sheet metal that will allow increased use of the high-strength alternative to steel and aluminum.

GM wants to expand its use of low-mass parts on vehicles around the world and will pursue licensing opportunities related to the technology. The goal is for suppliers to be able to use the process to provide significant amounts of magnesium sheet that will trim pounds from vehicle mass.

The use of magnesium, which weighs 33 percent less than aluminum, 60 percent less than titanium, and 75 percent less than steel, will help customers save money at the gas pump, as will more efficient conventional engines and electric powertrains, the company said.

Until now, automakers have struggled to make reliably strong and non-corroding magnesium sheet metal panels using traditional panel forming methods. GM said its patented process turns up the heat on magnesium to 450 degrees Celsius (842 degrees Fahrenheit), allowing the material to be molded into precise, rigid shapes. Using this process, the company said it has developed a production-ready magnesium rear deck lid inner panel that withstood 77,000 robotic slams and 250-kilogram impact drops without any issues.

Automakers also have struggled to make magnesium corrosion resistant. GM’s proprietary treatment for thermal-formed magnesium resisted 10 consecutive weeks of 24-hour environmental tests involving salt spray, 100 percent humidity and extreme temperatures.

Die-cast magnesium has been used in a variety of parts ranging from steering wheels to engine cradles, but GM is the first to use thermal-formed magnesium sheet metal in structural applications, and it expects magnesium sheet applications to grow with additional materials and process improvements targeted at reducing cost.

The United States Automotive Materials Partnership estimates that by 2020, 350 pounds of magnesium will replace 500 pounds of steel and 130 pounds of aluminum per vehicle, an overall weight reduction of 15 percent. This weight savings would lead to a fuel savings of 9 percent to 12 percent.

“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.”
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