The most cost-effective way to reduce vehicle weight and improve fuel economy is through the use of high strength steels (HSS). The metallurgy of the three basic types of HSS - recovery annealed/martensitic, conventional and dual-phase - is reviewed. The use of HSS, which have considerably higher tensile strengths than low carbon steels, can result in lighter weight components with no loss in fatigue or crush resistance. However the formability, which is discussed in terms of the forming limit diagram, r, the anisotropy factor and n, the strain hardening exponent, are greatly reduced in the HSS. In addition these steels exhibit an increase in springback and 'side-wall curl' and a decrease in sheared edge ductility. It is shown that springback can be alleviated by the 'double-bend' technique, curl can be removed by plastic deformation and edge cracking is improved by the use of inclusion shape control and good quality edges. With the advent of HSS with more consistent mechanical properties, as produced on continuous annealing lines, it is anticipated that these materials will comprise up to 20 % of the dry vehicle weight. The last section of the paper is concerned with a discussion of galvanizing and its influence on both weldability and formability. This article is translated in Russian too.
High strength steels in automobiles
Hochfeste Stähle in Automobilen
1988
17 Seiten, 16 Bilder, 2 Tabellen, 27 Quellen
Conference paper
English
AUTOINDUSTRIE , VEREINIGTE STAATEN VON AMERIKA , BAUSTAHL , UEBERSICHT , KALTGEWALZTES BLECH , DICKE , HOCHFESTER STAHL , MIKROLEGIERTER STAHL , CHEMISCHE ZUSAMMENSETZUNG , DUALPHASENSTAHL , MARTENSITISCHER STAHL , ERHOLUNGSGLUEHEN , VERSETZUNGSSTRUKTUR , VERFORMUNGSFAEHIGKEIT , LEGIERUNGSELEMENT , KONZENTRATIONSEINFLUSS , KANTENRISS , PUNKTSCHWEISSEN , VERZINKTES BLECH , ZUGFESTIGKEIT , STRECKGRENZE , BRUCHDEHNUNG , KALTWALZEN , KRISTALLVERSETZUNG , RUECKFEDERUNG
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