780 N/mm~2 grade hot-rolled high-strength steel sheet for automotive suspension system

摘要

590 N/mm~2-grade high-strength hot-rolled steel sheet has been applied to an automotive suspension system, and 780 N/mm~2-grade has recently been applied on trial to the same parts. Both of the steels used for the suspension system are required to have good formability, especially high stretch-flangeability. This paper describes the effect of the microstructure of the steel on stretch-flangeability. The results of mill trials have shown that the bainitic-ferrite mono-phase microstructure has the best mechanical properties.