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Steel vs. Aluminum: The Lightweight Wars Heat Up

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Steel vs. aluminum? By choosing to build the 2015 F-150 with an all-aluminum body, Ford is shaving 700 pounds from the truck’s weight. And that’s a critical factor as automakers struggle to reach a 54.5 mpg fleet average by 2025. The F-150 has been America’s favorite vehicle for 32 years, so lightweighting it—and reaching, maybe, 30 mpg on the highway—is really important to Ford.

The FutureSteelVehicle (FSV) is said to cut body mass by 39 percent when used in a battery electric vehicle. (SMDI graphic) “Over time, you’ll see more and more aluminum across our product line,” said Alan Mulally, Ford’s CEO, said at the Detroit auto show. “It will be the material of choice.”
 
Them’s fighting words, says the Steel Market Development Institute (SMDI). In an interview, Lawrence Kavanagh, the group’s president, and Ron Krupitzer, it’s vice president for automotive markets, stoutly defended the future of steel in lightweighting cars, and said that the venerable metal could match aluminum pound for pound.
 
“We can produce parts at the same weight as aluminum, at 37 percent less cost,” said Kavanagh. “If steel can do the same job at lower cost, then why make the shift?”
 Ford's 2015 F-150 loses 700 pounds with an aluminum body. (Ford photo)Krupitzer adds that steel’s cost advantage has led some manufacturers to switch aluminum parts back to steel. He also cited some cars, such as the new VW Golf, the Infiniti Q50 and the Acura RDX, that make extensive use of lightweight high-strength steel. “We’re doubling our efforts with car companies to show them the new grades of steel,” said Kavanagh.
 
SMDI also makes other arguments: Steel is more easily repaired than aluminum, and is also less energy-intensive to produce. “There are five times the carbon dioxide emissions from aluminum for the same weight,” said Kavanagh.
 
In 2011, SMDI introduced the FutureSteelVehicle (FSV), which was said to save up to 39 percent on body mass over a conventional car, while retaining a five-star safety rating. SMDI claimed the car would also reduce total lifecycle emissions by 70 percent. The target was clear: aluminum, which was already starting to show up in a lot of manufacturers’ body panels. The secondary target is carbon fiber, which displays huge weight-saving advantages and gets a workout on the new BMW i3, but remains too expensive to be used widely.

Both steel and aluminum claim to have the environmental advantage. (Aluminum Association chart)Of course, the aluminum industry counters steel’s claims. “When used to build new cars and trucks, aluminum reduces the total carbon emissions associated with climate change,” says the Aluminum Association. “It’s also infinitely recyclable, with nearly 75 percent of all aluminum produced since 1888 still in use today.” Because of these factors, the association expects the average vehicle’s aluminum content “to nearly double by 2025.”

Even with that sharp increase, steel will still be the number one auto metal, but aluminum’s rise has clearly got the old guard riled.

Kevin Lowery, a spokesman for Alcoa, says that steel’s arguments are “like old tapes being played.” He made a critical point—it’s mild steel that has a significant cost savings over aluminum. “When you compare high-strength steel to aluminum, the price points are pretty darned close,” he said.

Lowery also says that the repairability question was worth asking when the aluminum-bodied Audi A8 was introduced, and few shops could handle working on it, but today “thousands of places repair aluminum vehicles every day.”

Lowery also points to a preliminary 2013 Oak Ridge National Laboratory study concluding that an aluminum-intensive vehicle “offers the lowest lifecycle energy and carbon dioxide impact.” The lightweight steel vehicle “has the lower production phase environmental impact offset by higher use-phase energy and CO2,” the study said.
Making Jaguars out of aluminum. (Photo courtesy of Novelis)Tom Boney, general manager for automotive at Novelis, the primary supplier for the new F-150, said that steel's lower-emission production is offset by extensive recycling of aluminum. But, of course, steel is frequently recycled, too. Boney said he's privvy to other manufacturers' rollout plans through 2018, and that Ford's truck is just the beginning. "We are continuing to prepare for some really exciting major programs," he said. "No other F-150s, but some very large volume, very successful car-of-the-year vehicles."

Kavanagh claims Ford made the decision to switch the F-150 to aluminum four or five years ago, and that the company wouldn't make the same choice today. But Boney counters, "We know what's going on through 2018, and there isn't one carmaker, foreign or domestic, that isn't having a discussion about moving some of its platforms to aluminum."

Did you know the Tesla Model S has an aluminum-intensive body? (Jim Motavalli photo)Aluminum is the number one metal for making engines and wheels, and it’s showing up all over for hoods, trunks and doors. Cars with a lot of aluminum in them in addition to the A8 include the Jaguar F-Type, Tesla Model S, Lincoln MKT and the new Range Rover (which uses it to cut 926 pounds).

Think of this as Hertz vs. Avis. Hertz is still out ahead, but in that rear-view mirror it appears that Avis is gaining ground.  

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