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Taking The Shine Off.

Aluminum has many merits. But not all that glistens with the lightweight metal is gold.

Put the words aluminum and vehicles together, and the brain fast-forwards into exotica. Images of Acura's pioneering NSX, Audi's A8 luxosedan, the lightweight S2000 and Z8 roadsters soon to appear from Honda and BMW, come to mind. Think Ford P2000 and Honda Insight, the featherweight platforms for advanced powertrains. Think PNGV, and the importance of aluminum alloys in making an 80-mpg mid-sized dream become reality.

Now snap back into the critical issues of cost and volume. Did you know that only five pounds of the average auto body-in-white built in North America this year is aluminum? The rest remains steel.

Are you aware that over half of aluminum's closure panel content in U.S. light vehicle applications is found in just one program -- Ford's F-Series truck -- and that it's all in the hood?

And did you know that just four basic components -- engine blocks, cylinder heads, heat exchangers and road wheels -- account for roughly two-thirds of the total aluminum content in North American-built light cars and trucks?

The sound design and engineering reasons for aluminum's steady rise in automobiles are well explained in the preceding feature story. Those many merits are causing the material's per-vehicle content to jump from about 130 pounds in the downsized 1980s, to nearly 350 pounds by 2009, according to a 1999 study of North American vehicle material content by Ducker Research of Bloomfield Hills, Mich.

Holy Sheet

All that glistens for the bright metal clearly is not gold. As competitors in the steel and plastics industries are quick to point out, aluminum's major gains are not necessarily where they're perceived.

"It's a common misconception that they're taking it out of our hide in steel body sheet," asserts Pete Peterson, director of automotive marketing for U.S. Steel. He notes that as the century wanes, steel still commands about 55% of the mass of an average vehicle -- a percentage that hasn't changed in 20 years. But he admits that the decade's light truck boom has helped keep the proportion steady.

About 80% of aluminum's automotive growth is in castings, mainly used in suspensions, transmission and differential cases, and particularly in engine blocks and heads.

These applications are displacing mostly iron castings, particularly in cylinder blocks, notes Peterson. Less than 20/6 goes into body structures and closures (doors, hoods, and decklids). That's still overwhelmingly steel's kingdom because of cost and the industry's long experience with the material.

And while the intake manifold arena was for many years a safe haven for aluminum, reinforced plastics are steadily capturing the business, due to the plastics' lower mass and ability to mold separate parts, such as fuel mils, throttle bodies and EGR systems, into tidy, integrated modules.

The Ducker report also notes that about 13% of the aluminum content in the average North American-built light vehicle is aluminum foil, used mainly for radiators, oil coolers and other heat exchangers. In this growing role, aluminum's primary threat has been to copper sheet and foil.

The steel industry has chosen the body structure in general, and sheet applications in particular, as the Motherland it will defend to the death against aluminum's assault. Peterson and his colleague Darryl Martin, director of automotive applications for the American Iron and Steel Institute trade group, gleefully recite aluminum's losses of body panel business to steel: among them, the decklid of Ford's 2000 Taunts, the hood on Jaguar's S-Type (changed to steel from aluminum during the design phase), and Ford's reported decision to reconsider a high-volume, aluminum-intensive sportwagon program (D219) for 2002, due to the cost of body-grade aluminum-alloy sheet.

Debating the "Fleet Effect"

When steel wisely decided to aggressively protect its tuff earlier this decade, in the face of aluminum's clear growth curve, it did it proactively -- by studying how the material, and new processes used to form and fabricate it could help automakers improve new vehicles and even reduce weight, while keeping costs down. The plan worked, earning steel-makers new respect from engineering chiefs.

"Frankly, we're very impressed by the Ultra-Light Steel Auto Body (ULSAB) program, and the steel industry's similar investigations on making closure panels, suspension systems and the like lighter still," Bernard Robertson, DaimlerChrysler's head of advanced engineering, told AI earlier this year. "They've given us new reasons to appreciate steel."

As both metal industries search for new applications, they're also keeping the heat on each other in public. Last summer, steel and aluminum faced off on the environment -- specifically, a concept steelmakers call the "fleet effect" of aluminum.

The jousting began when the steel industry hired the Massachusetts Institute of Technology's Materials Science Lab to research an aluminum industry contention: that on a product life-cycle basis, aluminum-intensive vehicles and their manufacture produce less [CO.sub.2] than their steel counterparts.

The argument goes that by replacing two pounds of steel in a vehicle with a pound of aluminum, the resulting lighter-weight vehicle will emit 20 pounds of [CO.sub.2] less (due to its better fuel economy) than the heavier vehicle, over the vehicle's lifetime. Because it is burning less fossil fuel per mile, the aluminum vehicle thus begins cancelling out the [CO.sub.2] emissions generated in the aluminum-making process, sometime in the middle of its useful life. (Aluminum-malting creates about six times greater [CO.sub.2] emission, per ton, than is created during steelmaking, claims the aluminum industry.)

Steel pulled its Sheffield sabre out of the sheath and waited for MIT's Dr. Joel Clark, a noted materials expert, to parry the lightweight metal's thrust.

Clark's analysis compared Ford's aluminum-intensive Sable AIV with its steel-bodied `92 Taurus cousin and with the ULSAB midsized sedan concept. It concluded that a large-scale switch to aluminum-intensive vehicles could make [CO.sub.2] emissions an even greater problem. Reasons included:

* Producing one ton of virgin aluminum creates about 10 times more [CO.sub.2] emissions than does producing a ton of steel.

* Building a fleet of 100,000 aluminum-intensive vehicles each year, for 12 years (a number picked as the typical life of a vehicle), creates over 2.26 million tons of [CO.sub.2]. Clark says that output includes any emissions gains from the vehicles themselves. It would thus take 35 to 38 years of driving aluminum vehicles for the "crossover" to occur between [CO.sub.2] saved in vehicle operation, versus [CO.sub.2] created in aluminum manufacturing.

Clark also found that the ULSAB vehicle, with its steel content optimized for low mass and strength, would generate a lifetime total of [CO.sub.2] that's 678 pounds less than the aluminum-intensive Sable. "The AIV never does recoup its initial [CO.sub.2] disadvantage," notes the MIT study.

The aluminum industry naturally refutes the MIT study.

"Aluminum's record is clear and easily verifiable," retorts J. Stephen Larkin, president of the Aluminum Association. "No matter how complicated the steel industry tries to make the materials comparison, it will not change the simple physics behind the improved fuel efficiency achieved from substituting aluminum for heavier materials in automobiles," the group asserted.

To the auto industry's product planners, designers, materials experts and engineers, the metallic ringing in their ears can only grow louder. If you think aluminum and steel are battling it out now, just wait until the price of gasoline in the U.S. exceeds $2.00 a gallon. Then the sparks will really fly -- only on the steel side, of course.
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Author:Brooke, Lindsay
Publication:Automotive Industries
Geographic Code:1USA
Date:Oct 1, 1999
Words:1242
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