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GM testing magnesium metal for lighter cars

General Motors is testing magnesium sheet metal, which would make cars and trucks weigh less.

Die-cast magnesium is commonly used in cars and trucks for steering wheels and other parts. What is new, said GM metals researcher Jon Carter, is the ability to form magnesium sheets to make inner panels of doors and trunk lids.

GM is starting slow, but eventually the expanded use of magnesium can take a significant amount of weight away from cars and trucks, Carter said.

Magnesium is 75 per cent lighter than steel and 33 per cent lighter than aluminum, said GM engineer Paul Krajewski.

"Magnesium will allow us to reduce the weight of certain sheet metal panels and thereby improve fuel efficiency and handling and overall performance," Carter added.

It is more difficult, Krajewski said, to form lightweight metals such as aluminum than it is to stamp out auto parts by using steel. It is difficult still to form magnesium sheets into the intricate shapes needed for inner panels on cars and trucks.

GM will conduct a production run of 50 vehicles to be bought by consumers in the fourth quarter, but Carter would not indicate the model or models that will test the expanded use of magnesium this year.

Carter and Krajewski said the goal of taking weight out of vehicles is largely due to the more stringent US fuel economy standards to go into effect in coming years.

By 2020, magnesium will be able to take out 15 per cent of the weight of a vehicle, leading to fuel savings of 9 per cent to 12 per cent, according to the US Automotive Partnership.

Forming magnesium sheets into auto parts by heating them to 842°F (450°C) is a slow process. Eventually, Carter said, GM researchers want to test the use of alloys in the process that will allow magnesium sheets to be reshaped at lower temperatures, and eventually, at room temperature.

So the use of magnesium in GM vehicles will be small in the near-term, but may expand as researchers and engineers speed the process.

GM has patents on the process for heating magnesium and for making it more resistant to corrosion. The company plans to license the technology to allow auto-parts suppliers to produce the magnesium inner panels, according to GM spokesman Kristopher Spencer.

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