Recently, newly developed bake-hardenable (BH) steel sheets strengthened by CuS have been successfully employed in commercial production lines that supply automotive outer panels. The metallurgical concepts governing fabrication of these new BH steel sheets require keeping carbon content as low as 0.0015 wt.% without any additional amount of titanium and/or niobium for solute carbon scavenging. The role of CuS precipitates has turned out to raise the yield strength acting as a barrier against dislocation movement. In this paper, we studied the effects of chemical compositions and manufacturing process variables on the microstructure and mechanical properties of newly developed BH steel sheets. We found that the control of carbon and nitrogen showed a good balance between bake-hardenability and yield point elongation. We identified the crystallographic relationship between the nano-size CuS precipitates and the ferrite matrix of (001)sulfide//(001)alpha-Fe and [001]sulfide//[001]alpha-Fe. We also found that the bake-hardenability and yield point elongation were affected by the formation of AlN and the annealing temperature.
Development of Cu-bearing bake-hardenable steel sheets for automotive exposed panels
Entwicklung von kupferhaltigen Bake-Hardening-Stahlblechen für Fahrzeugaußenwände
Metals and Materials International, Seoul ; 16 , 6 ; 883-890
2010
8 Seiten, 8 Bilder, 2 Tabellen, 23 Quellen
Article (Journal)
English
Aluminium , Aluminiumnitrid , Ausscheidung , Bake-Hardening-Stahl , Fahrzeugwand , Festigkeitserhöhung , Glühtemperatur , IF-Stahl , Kaltnachwalzen , Kohlenstoffgehalt , Korngröße , Kupfersulfid , Kupferzusatz , mechanische Eigenschaft , metallisches Carbid , Mikrostruktur , Orientierungsbeziehung , Reckalterung , sehr kohlenstoffarmer Stahl , Stahlherstellung , Streckgrenzenverlängerung , TEM (Transmissionselektronenmikroskopie) , Verformung , Warmband
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