The changing shape of steel in cars

NYTimes.com: The modern car still contains 60 percent of steel by weight.

But automotive steel has changed quite a bit since the Ford company's first Model T rolled off the assembly line in 1908. Metallurgists and manufacturers have learned to manipulate steel's microstructure through precise control of processing to create sheet steels of increasing strength. Prompted by crash-worthiness requirements and the need to make cars lighter to improve gas mileage, automakers are replacing conventional steels with advanced high-strength ones.

Where once a single grade of steel might have sufficed, the typical "body in white," as automakers call a car's basic skeleton, might now be a patchwork of a dozen or more steels of different types and strengths, tailored through computer modeling to handle the stress and strain of normal driving—and of severe crashes.