9/1/2000 | 7 MINUTE READ

This, That, and the Other

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At AD&P, we are not what you might call "neat freaks." We work in offices that often have but a single path between door and desk—the floor being the only available space in which to stack press kits, papers, reports, photos, notebooks, and all other manner of information from which we assemble this magazine. Occasionally, we determine that our working conditions might be bordering on the hazardous and we attempt to clean up.

This month, we found the following cool stuff about materials buried amidst copies of European car magazines, machine pamphlets, and briefcase bags emblazoned with corporate logos. Which is not to disparage the importance of this information, but to state that this is not a tidy little article that sticks to one topic. (In fact, there's something here about each of the big three materials: aluminum, composites and steel.) But why draw attention to this haphazard creative process? To make the point that in this day and age, regardless of your discipline, neither the information that you use nor the solutions that you seek come in nice orderly packages.

Beware of anyone with a clean desk.

For five years now, Stahl-Informations-Zentrum, a German steel industry organization, has been awarding Steel Innovation Prizes. This year, two such awards were given to subsidiaries of ThyssenKrupp AG (Düsseldorf) for developments in automotive components. A new catalytic converter substrate garnered an award for Krupp VDM GmbH, while a new multi-link suspension system design landed one for Thyssen Umformtechnik und Guss (TUG) GmbH.

To explain the significance of the new catalytic converter substrate, first consider this: according to Krupp VDM, 70% of all pollutants emitted from a conventional catalytic converter are produced when the engine is started, before the catalytic converter has warmed to its ideal operating temperature. So the obvious key to reducing pollutants is to heat the cat faster. But how? Krupp VDM's solution is to reduce the thickness of the steel substrate, the honeycomb-shaped surface that's coated with the expensive metals (platinum and rhodium) that act as the catalysts.

Seems pretty simple. So why hadn't anyone thought of this before? Well, they probably did. But metallic-substrate converters are made from corrugated and wound metal foils, and according to Krupp VDM, inadequate heat resistance has limited these materials to a thickness of no less than 30 µm. But a new alloy called Aluchrom 7Al YHf—developed in conjunction with the Fraunhofer Institute for Applied Materials Research (Bremen), the University of Wuppertal, and Emitec GmbH (Lohmar)—can be manufactured in a thickness of just 25 µm and still withstand the 1100°C exhaust temperatures. The alloy is created by first and foremost increasing its aluminum content. This improves heat resistance, as the aluminum oxidizes under heat exposure, forming a protective coating. This necessitates adding reactive elements yttrium and hafnium to the alloy to slow the aluminum depletion, thereby achieving a similar life span to that of conventional 50 µm foils. Furthermore, the low electrical resistance of the material allows catalytic converters using it as a substrate to be electrically preheated, further reducing light off times.

While using chemistry to save the environment is a noble endeavor, ThyssenKrupp's other award-winning idea may be nearer and dearer to the hearts of many, as it involves saving cash. Even better, the new suspension design can facilitate high-end handling performance in decidedly less-than-high-end vehicles.

The crux of the multi-link design is a stamped wheel knuckle. Rather than employing a cast and machined part like a traditional multi-link suspension, TUG uses two stampings joined by shielded arc welding; the inner piece also acts as the trailing arm. Main advantages include a 30-40% weight reduction, while manufacturing costs are said to be 50% lower. Since this design is more compact and less costly, it also allows for multi-link suspension systems to be fitted on smaller vehicles. Tests of the same system with high strength steels show even further weight reduction potential.

Glückwünsche Zwei
Speaking of German awards…it is worth noting that Dow Automotive (Auburn Hills, MI) was the only North American supplier to pick up a corporate supplier award from Volkswagen AG. Dow Automotive received the 1999 Leading Edge Award. There were a total of 45 suppliers awarded based on their meeting VW's requirements for flexibility, innovation, quality, service, and competition.

(We get flooded with announcements about companies winning such things as awards from GM and other automakers, but this curious distinction vis-à-vis a North American company and a German company piqued our attention.)

Dow Automotive's resins are used in a variety of applications—interior trim, consoles, and instrument panels among them—on VW vehicles including the Golf A IV, Bora, Jetta, Passat, Seat Toledo, and Audi A6.

Bumpin' Around
According to GE Plastics' automotive group in Southfield, Michigan, the 2001 Chrysler and Dodge minivans that have just started rolling are the first in their class to feature a thermoplastic bumper beam that exceeds the 2.5-mph federal impact standard. Mark White, GE Plastics market development manager comments, "We've integrated the functions of the traditional steel or aluminum beam and impact-absorbing foam into one high-performance, lightweight, injection molded system that not only meets the required 2.5-mph federal impact standard but passes the federal impact test at 5 mph."

Trailing arm
That yellow piece of metal that resembles a banana is actually the trailing arm of this multi-link suspension system. It's also the same stamping that forms the inner piece of the wheel knuckle.

The bumper was developed by GE Plastics along with Nascote Industries. It is being molded with xenoy 1103 resin, a blend of polycarbonate/polybutylene (PC/PBT), which means it combines the performance strengths of both amorphous and crystalline materials, a high flexural modulus, high tensile strength, good chemical resistance, and good low-temperature impact.

Benefits of the bumper system include the aforementioned impact resistance, as well as significant weight reduction: it weighs 11.4 lb., which is 8 lb. less (or 41%) than the stamped steel bumper it is replacing.

HOWEVER...the Bumper Project Group of the American Iron and Steel Institute has conducted a study that shows that the material that is presently dominant in the production of bumper systems—steel, of course—will actually gain strength within the next few years, marketwise, that is.

According to the study, it looks like this:

  • Steel: 76% of the market in 1997; projected growth to 91% in 2004
  • Aluminum: 6% of the market in 1997; projected decline to 1.4% in 2004
  • Plastics: 18% of the market in 1997; projected decline to 7.6% in 2004.
A reason why steel is having such a strong showing is because manufacturers are increasing their use of high-strength (minimum yield strength > 35 ksi and a minimum tensile strength < 100 ksi) and ultra high-strength steels (minimum tensile strength > 100 ksi. The study also examined 11 bumper systems. Included:
  • 2000 Ford F150 pick- up front face bar. Stamped high-strength steel features a 22-in. depth-of-draw for an aero advantage that facilitates fuel economy.
  • 2000 Ford Crown Victoria and Mercury Grand Marquis front reinforcing beam. Roll formed with an ultra high-strength steel.
  • 2000 T300 Dodge Ram pickup front face bar. Stamped from high-strength steel. Blank designed so that 65% of the finished trim line incorporated, thereby reducing scrap.
  • 2000 Chevy GMT 800 pickup front face bar. High-strength steel stamping features integrated brackets.
  • 1998 Volkswagen Jetta front reinforcing beam. Stamped from a high-strength steel tailor welded blank: 80,000 psi yield strength in the middle of the blank and 45,000 psi at the two end portions, thereby providing strength and formability.
  • 2000 Toyota Avalon front reinforcing beam. Roll formed ultra high-strength steel part mounts to the rails with minimal bracketry.
  • 2000 Ford Ranger pickup front face bar. Stamped high-strength steel part uses an energy-absorbing mounting bracket.
  • 2000 Ford Taurus and Mercury Sable front reinforcing beam. Roll formed from ultra high-strength steel: actually 190 ksi tensile strength martensitic steel, which is said to be the highest strength automotive sheet in production in North America.
  • 2000 Chrysler Voyager rear reinforcing beam. Ultra high-strength steel drawn to a 6-in. depth.
  • 2000 Toyota Camry front reinforcing beam. Ultra high-strength steel roll formed with a large sweep (35 sweep number) for a double box section.
  • 2000 Chevy Cavalier and Pontiac Sunfire front reinforcing beam. Roll formed ultra-high strength steel with a 50 sweep number, but this is a box section.
All of which goes to say that there are a lot of steel bumpers out there now, and their number is expected to grow.

Speaking of increases, this from the Automotive Bright Product Association (ABPA; Troy, MI): in 2004 more than 4.5 million aluminum chrome-plated wheels are expected to be produced. This is in contrast to five years ago, when less than one million were produced. The expectation is that the OEMs will have platers provide 2.5 million aluminum chrome-plated wheels in 2001. Comments J. Patrick Billinge, "Consumers prefer the look of chrome-plated wheels and consider them one of the top three options when buying or leasing a new vehicle." Billinge is the ABPA's executive committee spokesman, who went on to remark, "We fully expect consumer demand will drive increased production well past 2010."