Modern vehicle bodies make intensive use of high strength steel grades to meet the contradicting demand of lighter weight and simultaneously better mechanical performance. For many steel grades microalloying by niobium is the key to achieve their characteristic property profile. In HSLA steels niobium enhances the strength primarily by grain refinement. In interstitial free high strength steels niobium serves as a stabilizing element. Some modern multiphase steels rely on niobium to achieve additional strength via grain refinement and precipitation hardening. Microstructural control constitutes a powerful means to further optimize properties relevant to automotive processing such as cutting and forming. The role of niobium microalloying in that respect is outlined. The fundamental effect of niobium is that of grain refinement increasing the strength without deteriorating the ductility. It thus allows to work with a leaner alloying concept to reach a specified strength level. A leaner alloy concept is beneficial with regard to welding operations. Grain refinement also brings about a more homogeneous microstructure improving the forming behavior particularly when high localized strains are being induced. Niobium can exert a significant influence on the transformation behavior allowing to promote or retard the formation of individual phases. This can be exploited to exert better process control and optimize properties when producing multiphase steels. The formation of NbC precipitates is used to scavenge carbon from the ferrite matrix in IF steel. Partial redissolution of NbC in the annealing cycle can be used to liberate carbon for the bake hardening effect.


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    Title :

    The role of niobium in lightweight vehicle construction


    Additional title:

    Die Rolle von Niob in der Automobilleichtbauweise


    Contributors:


    Publication date :

    2005


    Size :

    8 Seiten, 6 Bilder, 16 Quellen



    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




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