The largest steel component is the engine (12 to 15 percent). A typical material composition of a mid-size passenger car would be 55 percent steel, 15 percent iron, 5 percent aluminum, 8 percent plastics, and 17 percent other. Substitutions of lightweight materials for iron and steel yield a primary weight savings plus a secondary weight savings derived from downsizing of supporting components, engine size reduction, and so forth.
For vehicles that are completely redesigned (that is, all but the 2005 “optimistic” vehicle) a secondary weight savings of 0.5 pounds per pound of primary weight is assumed for equal performance. For the 2005 “optimistic scenario” vehicle, a secondary weight savings of 0.25 pounds per primary pound is assumed.
For the 2005(m) scenario, the vehicle is an optimized steel design that has an aluminum engine. Because of the automakers familiarity with steel auto manufacture, it is assumed that 10 years is long enough to implement a complete vehicle redesign.
Through a clean sheet design approach with high-strength steels and advanced manufacturing processes, curb weight is reduced 11 percent, with an additional 4 percent reduction from the aluminum engine, for a total of 15 percent, compared with an unsubstituted baseline. Composition changes to: steel, 51 percent; iron, 8 percent; aluminum, 12 percent; plastic, 10 percent; and other, 19 percent.
Details about Reduction Scenarios
The estimated cost increase of $200 to $400 for the intermediate sedan is scaled according to weight for the other size classes. For the 2005 optimistic scenario, the vehicles have an aluminum-intensive body and an aluminum engine. However, it is assumed that by 2005, there is insufficient time to solve all of the design and manufacturing issues associated with a clean sheet aluminum design with maximum substitution and full secondary weight reductions.
A 20 percent weight reduction below baseline is achieved assuming secondary weight savings of 0.25 pounds per pound of primary weight. Composition changes to: steel, 29 percent; iron, 8 percent; aluminum, 31 percent; plastic, 12 percent; and other, 20 percent. The cost increase is estimated at $1,500 for the intermediate sedan and scaled according to weight for the other size classes.
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