New grades and assembly approaches are giving steel new life in the highly competitive battleground for automotive materials. Automotive engineers discussed their plans for steel at the Great Designs in Steel seminar held in Troy, MI in April by the American Iron and Steel Institute.
New models from Honda, Chrysler, GM and BMW, in particular, show dramatically increased use of advanced, high-strength steels which reduce weight and boost safety performance of body structures. BMW's new X6 Sport Activity Coupe body structure contains 61 percent high-strength steels, including 1,300 MPa tensile strength hot-stamped B-Pillars. The Chrysler Minivan uses high-strength steel in tandem with front and side air bags to boost occupant protection
While overall weight in cars will drop from 2007 to 2015, use of high-strength steels (including advanced grades) will rise from 483 to 718 lb, according to a presentation made by Jody N. Hall, manager of global die standards and materials applications for General Motors Mfg. Engineering. In that same time frame, use of plastics composites will rise from 340 to 364 lb. Aluminum will rise from 327 to 374 lb. Growth for new materials will come at the expense of conventional mild steels, which will remain the dominant material used in cars. Hall's data is based on reports from Drucker Worldwide.
One of the problems facing plastics is the high cost of automotive grades, which are often special high-heat variations. Hall estimated the cost for auto plastics at $1.20 to $6.50 per pound, compared to 50 cents a pound for mild steels and 55 cents a pound for high-strength steels. Aluminum runs about $1 per pound and magnesium is $1.50 per pound.
“Cash is king,” says Hall. “Customers are paying less than before and are demanding more.”
Other problems with plastics are lack of manufacturing infrastructure and a poor recycling track record. Steel and iron recycled from a typical vehicle produced an income stream last year of $303, compared to zero from plastics used in cars, according to data reported at the seminar by the Steel Recycling Institute.
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