Modern vehicle bodies make intensive use of high strength steel grades to improve the weight and the mechanical performance simultaneously. A broad range of medium and extra high strength steel grades is available. These steel grades have different characteristics concerning strength, formability and weldability. 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 and also assists in obtaining the bake hardening effect. Some modern multiphase steels rely on niobium to achieve additional strength via grain refinement and precipitation hardening. Microstructural control provides a way to further optimize properties relevant to automotive processing such as cutting, forming and welding. The relevance of niobium microalloying in that respect will be outlined.
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