The new Audi A8, scheduled for release in 2018, features a multi-material body structure consisting of more than 40% steel. That’s a marked turnaround from the all-aluminum body-in-white which Audi developed for the A8 in 1994, in which steel was essentially used for the B-pillars alone, and accounted for about 8% of the body structure.
Since then, steel has evolved significantly. Steel’s strength has multiplied by almost 10 times over the past 20 years, from 270 to 2000 MPa tensile strength. More than 80 new steel products are under development at steelmaker ArcelorMittal, with an automotive steel grade portfolio of almost 200 unique steel grades, half of which were introduced in just the past decade.
Around 17% of the new A8 body structure will comprise press hardenable steel (PHS), some of which will be supplied by ArcelorMittal. These steels have yield strengths up to 1500 MPa after press hardening. The strength-to-weight ratio of these grades outperforms even the most advanced—and costlier—aluminum grades. With the advent of new joining technologies, automakers can easily incorporate advanced high-strength steels into their vehicles. As these technologies mature and are adopted by carmakers, the use of PHS in the multi-material vehicles of the future is set to grow rapidly, according to ArcelorMittal.
Audi’s switch back to steel is part of a growing trend which is even surpassing the expectations of steelmakers, according to data released by the Steel Market Development Institute (SMDI).
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