Steel for the Cars of Tomorrow
Scientists at the Max Planck Institute for Iron Research in Düsseldorf develop lightweight steels that are not only particularly strong, but also very ductile. Their low specific weight and exceptional mechanical properties make them ideal material for applications in the automotive industry.
Text: Tim Schröder
The mention of iron and steel making usually conjures up images of huge blast furnaces in which molten raw (pig) iron glows white-red, bubbling gently. Once it has reached the correct temperature and composition, it is simply poured off in a submarine ladle, or it rapidly solidifies to masses of pig iron. Or so it may seem. Yet steel making is more than just this large-scale tableau. It can, in the truest sense, be compared to the high art of gourmet cooking: producing steel with specific properties requires the right ingredients, the right recipe, and creativity on the part of the cooks.
Georg Frommeyer is a steel expert with the requisite ingenuity. He is professor of materials technology at the Max Planck Institute for Iron Research in Düsseldorf, where he and his colleagues have developed new kinds of steel that major players in the steel industry have called “a significant leap forward in development.” These steels are very light, extremely tough and particularly ductile. Known at the institute as “high-strength, supraductile TWIP/TRIP lightweight construction steels,” they are especially suitable for the automotive industry.
Regardless of whether they are intended for the road or the railway, the focus is always on making vehicles tougher, lighter and safer. Bodyworks are expected to offer higher and higher levels of occupant safety in the event of accidents. At the same time, engineers aspire to create increasingly lightweight designs in order to reduce fuel consumption and emissions. Steel manufacturers have long since realized that they are facing increasing competition from aluminum and new materials, such as magnesium and plastics. To stay in the running, they must make their steels lighter, stronger and more ductile than their competitor products.
Steel consists mainly of iron. It takes on different properties when, for example, different metals are added – or alloyed – such as manganese, nickel or chromium. This is how stainless steel and high-strength or even super high-strength steels are created – the right material for the application at hand. Automobile manufacturers are particularly demanding when it comes to steel for autobodies, which must be strong enough to take the weight of the vehicle without deforming or vibrating. They must also be rigid enough to form a protective structure around the vehicle’s occupants in the event of a collision. And it should be possible to calculate precisely how they will deform to absorb the impact energy in an accident.
Although a single material will not have all of these properties, the steels from the Max Planck laboratories in Düsseldorf are truly multipurpose, and are able to take on several different functions. “A few years ago, experts were saying that the properties of steel had been exhausted,” says Georg Frommeyer. “Alloying steel with other elements had already made it suitable for numerous functions.” Nevertheless, the Max Planck researchers were convinced that there was more to be coaxed from this well-established material, although initially their assumptions were based only on theoretical considerations and many years of experience.