Commentary

Car Wars: Steelmakers Strike Back Keith Taylor

"The battle of competition is fought by cheapening of commodities." -Karl Marx

Competition, those in capitalist societies say, brings out the best. My youth provided an opportunity to personally witness materials competition in an everyday-life application-the beverage can. In 1970, recycling was a new concept, and our Boy Scout troop was involved in a drive to collect aluminum cans. We had a drop-off bin set up in a shopping center parking lot, and on weekends we harvested cans (as well as other refuse) from parks and along roadsides. At the time, most cans were made of steel, and glass bottles were still in wide use. The stronger and heavier "tin" cans were the recycler's gangue and had to be kept separate from the aluminum cans. An exciting thing about the aluminum can was, besides its value (Reynolds was paying ten cents per pound), that it could be crushed with bare adolescent hands, giving a satisfying illusion of brawn. Aluminum went on to capture the U.s. beverage can market with staggering speed. Today, nearly all beverage cans are aluminum, and about four times as many cans are produced as were in 1970. It is probably safe to conclude that the steel vs. aluminum competition has contributed to increasingly better cans. Despite the setback in the Can Wars, my respect for steel was renewed during college. Ferrous alloys were the prototypical materials for many of the concepts and teachings in my metallurgical courses. I was amazed at the richness and variety of the solid-state phenomena that can come into play in the processing of steels. By tweaking the recipe and processing judiciously, an improbably wide range of properties-mechanical and physical-can be accessed with iron-based ingredients. The situation with other metals is often far less intriguing. Metallurgically, aluminum is downright boring by comparison. Pressures to boost fuel efficiency have, of course, been driving automakers to reduce vehicle weight. As a result, alternative materials to steel such as aluminum have become increasingly attractive. The steel industry, still mindful of the beverage-can lessons, realizes that aggressive pursuit of product and process improvements is necessary to ensure that the important automotive market is not lost. I do not agree with the introductory 12

comment by Marx, but cost reduction probably does drive many industrial product and process development efforts. Steel is already" cheap," and prices have been relatively stagnant for more than a decade. Adjust the prices for inflation and you find that steel has been getting even cheaper. The cost advantage that steel enjoys over many competitive materials may become even more significant as consumer demands for automotive safety and comfort features continue to grow. In this issue of JOM, however, the emphasis is not on the development of lower-cost steel products. Instead, the focus is on several automotive applications in which efforts are directed at developing improved steels or simply at using steel more intelligently. The following are some applications where the competition between steel and alternatives is especially fierce. Body-in-white (BIW) design: The article by Mary Jean Crooks and Ronald Miner (LTV Steel) describes a program supported by an international consortium of steel producers and carried out by Porsche Engineering Services. Here, a holistic design approach that makes extensive use of high-strength steels achieved a weight reduction of more than 20% (and a 14% cost reduction) as compared to a BIW benchmark. The resulting body structure also has a torsional rigidity 60% greater than the benchmark. All of this was accomplished without invoking any fundamentally new forming or joining techniques. Subsequent phases of this program will test actual prototype bodies. Hot-rolled sheet for wheels: In an example of tailoring the processing to suit the characteristics of the material, researchers from Sollac (the French steel company) demonstrate how fatigue resistance can be improved by numerically simulating the forming process to utilize higher-strength steels in wheel designs. The article by Guy Marron and Pascal Teracher describes how they examined four basic compositions, providing distinctive microstructures and tensile strengths ranging between 460 MPa and 830 MPa. Through intelligent design of the forming sequence, estimated fatiguelife increases of up to a factor of three were obtained. The authors suggest that this increased fatigue resistance can be translated into a thickness reduction (i.e., weight savings).

Fuel tanks: Due to a number of factors, plastics are threatening to replace leadalloy coated steel as the material of choice for fuel tanks. Improved steel products with lead-free coatings that are more resistant to corrosion by a1coholcontaining fuels (e.g., Zn-Ni, Zn-Fe, and tin) have been proposed for this application and are undergoing evaluation. The article by Peter Alvarado (U.s. Steel) compares plastics and steels in terms of market share, design, manufacture, cost, performance, and recyclability. High-strength steels for body parts: Thanks largely to development of zincbased coatings, corrosion has become almost a non-issue for steel body parts. Efforts to improve the steel substrate continue, however, and Wolfgang Bleck (Aachen University of Technology) reviews some of the latest metallurgical approaches for increasing the strength and formability of steel sheet. Recent process advancements, such as the capability to routinely control chemical composition at the parts-per-million level, have helped to make some of these approaches viable. Steels that undergo strain-aging during the paint-baking treatment are one example. These "bakehardenable" steels have gained the attention of automakers as a means of increasing dent resistance and for the possibilities they offer for weight reduction. Microalloyed and multiphase steels (containing mixtures of ferrite + martensite or ferrite + bainite + austenite) are also being developed with a primary objective to provide weight reduction. Yes, competition is good! And aggressive efforts such as those highlighted in this issue of JOM are helping to improve vehicles by bringing out the best in steel. Aluminum and high-tech materials may be assuming important roles in applications that stir the imagination-aerospace,' microelectronics, and even the cover of Madonna's book!-while steel struggles for regard despite its ubiquity and continued advances in sophistication. Still, it is much easier to imagine a world without aluminum and high-tech materials than one without steel! Keith A. Taylor is a senior research engineer at Bethlehem Steel Corporation. He is also the advisor to JOM from the Ferrous Metallurgy Committee of the TMS Structural Materials Division. * Actually, there is at least one advanced aircraft that arguably can be regarded as steel-intensive. The experimental Mach 3 XB-70 Valkyrie, which helped inspire the design of the defunct American SST, featured panels that were predominantly stainless steel.

JOM • July 1996