Steel wheels have lost a lot of traction over the past two decades. Back in 1980, steel was the material utilized in 90% of automotive wheel production. But in 2003, it could only lay claim to less than half of this market, as aluminum has muscled its way to 60% of production.

What's responsible for the slide of steel wheels? Perhaps the biggest reason was the growing interest of consumers in high-end trim level packages—a trend that was ushered in by the 1990s economic bubble. Additionally, stamped and welded steel wheels could not match the tight tolerances held by aluminum wheels, which are cast and machined. This precision meant that aluminum could deliver higher uniformity and reduced vibration on the road—a big plus in the age of the sport utility vehicle, which is more susceptible to transmitted road vibration.

But now, steel is set for a comeback. Now that the high-margin era has passed, aluminum's higher costs have become more burdensome, and lower cost steel wheels are growing in appeal. In fact, steel is already beginning to recapture a sizeable portion of its lost market share. For example, Tom Heck, director of product engineering at Hayes Lemmerz of Northville, Michigan, says that his company alone will replace an estimated 2 million low-end aluminum wheels with steel units that feature both large ventilation areas and attached cladding. Slated to appear on various new vehicle platforms in the 2006 model year, these steel units imitate the thin-spoke look of aluminum.

Clearly, manufacturers are now starting to achieve sleeker and sportier designs with stamped and welded steel. While the metal has long delivered production cost advantages, it had been hampered with material limitations. One way manufacturers have attained aluminum-level fatigue strength with conventional steel grades is by raising material thickness, as seen in the high-strength low-alloy (HSLA) steels that are now widely used in wheel production.

Manufacturers have also started looking into dual-phase steel, discovering that its properties make it ideal for wheel production. With this material, they can make walls thinner and entire wheels lighter. Moreover, this metal is easier to form because of its high elongation factor. It can bend readily in deep draw dies without breaking. Another advantage of dual-phase is there's little guesswork involved in using it. European wheel manufacturers have worked with it extensively since the late 1980s, and in the U.S., it was utilized in trial production as early as the 1970s. The material was never widely adopted in the U.S., however, because of its limited availability and "red scale" flaws resulting from its silicon-rich content—two issues that are now being resolved with more mills producing the material in the U.S and new formulations.

And aside from the availability of better materials, improved design and production techniques are also supporting steel's comeback bid. Much more precise designs are now possible because of recent advances in simulation software, says Zeferino Bacchineto, engineering manager at the Wheels Division of ArvinMeritor of Troy, Michigan. And Heck makes a similar observation, noting that improved CAD/CAM tooling data has enabled Hayes Lemmerz to increase wheel uniformity and dimensional precision.

But while steel wheels are set to regain market share, they are only challenging high-volume, low-end aluminum units. Two factors are keeping the metal from penetrating top-of-the-line models. First, steel wheels still cannot offer the styling benefits of pricey aluminum wheels because the casting and machining processes that shape aluminum are much more adaptable. And second, casting is more cost-effective than stamping at low, luxury volumes. In short, while steel is not expected to completely reclaim the dominant position it once held in the automotive wheel market, it is certainly on the verge of a resurgence.

Source:

Steel Wheels Make a Comeback
Kermit Whitfield
Automotive Design & Production, May 2004
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