A Development of 780MPa Hot Rolled High Strength Steel for Application to Automotive One-Piece Front Lower Control Arm

Automakers are putting ever more emphasis on their environmental and energy efficiency efforts through improving the fuel consumption of vehicles. One way of saving energy is to reduce the total weight of the vehicle by using high strength steel. Hyundai steel developed a new 780 MPa grade of hot rolled high strength steel with excellent stretch flange formability in which the ferrite matrix is strengthened by ultra-fine, nano-sized precipitates. The material developed in our study met the material requirement of OEM's material specification with 780 MPa tensile strength and 55% hole extension ratio. Steel grades of 780 MPa were applied to develop front lower control arm for automotive chassis. In order to evaluate the performance of materials, primary design, durability and strength analysis of materials were prepared in collaboration with suppliers. Prototype of front lower control arm was fabricated and durability test and strength test were performed. Both of them satisfied the target.