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 has been applied to the suspension system, and 780 N/mm~2- grade one has recently been applied on trial to the same parts. Both of the steels used for the suspension system are required good formability, especially high stretch-flangeability. This paper describes the effect of microstructure of the steel on the stretch-flangeability. It has been shown by the result of mill trial that the bainitic-ferrite single-phase microstructure has the best mechanical property.