Microalloyed high strength steels for reduced weight and improved crash performance in automative applications

Reduced weight and improved crash performance are two important targets for the automotive industry today. Reduced weight means reduced fuel consumption, reduced CO2 emissions and improved driving performance. More than 50 % of the weight can be taken away by using high strength steel instead of conventional mild steel on single components. Improved crash performance is important in order to produce safer vehicles and to reach five stars in international crash tests, such as the EuroNCAP. With microalloyed high strength steels, these two targets can be achieved simultaneously in a cost effective way compared to other lightweight materials. These steels show good formability, weldability and parts can be manufactured with conventional forming and welding equipment. The main microalloying element used in high strength steels at SSAB Swedish Steel is niobium. The range of niobium alloyed steel grades includes precipitation hardened hot-rolled grades, precipitation hardened cold-rolled grades, dual phase cold-rolled grades and martensitic coldrolled grades. Cold-rolled grades are produced uncoated and hot-dip galvanized. This paper shows some examples of how these grades are produced, their properties in forming, welding and design as well as their current applications in the automotive industry. (AU)