Niobium Metallurgy in Advanced High Strength Steels for Automotive Light-Weighting

In order to increase safety standards and to reduce CO₂ emissions, advanced high strength steels (AHSS) are increasingly being used in the manufacturing of car bodies. As state of art the body mass of the latest vehicles already constitute more than 30% AHSS and the future target is to increase this to 60%. However unlike conventional high strength steels many OEMs find it challenging to apply AHSS due to the differences in forming behaviour, high strain-rate behaviour, weldability, and potential HIC delayed cracking. In the development and application of the new generation of AHSS a key enabler has been the use of a low carbon concept microalloyed with niobium (Nb).

The present paper explains the fundamental concepts and metallurgy of low-carbon Nb-microalloyed AHSS. Focusing on Nb microalloyed Dual Phase (DP), Press Hardened (PH) and Complex Phase (CP) steels, the performance of these steels when applied in modern forming technologies are also discussed together with specific automotive component examples.