Replacing Press Hardenable Steel with 980 MPa Generation 3 Steel for Automotive Pillars 2018-01-0117
Press hardenable ultra high strength steel (UHSS) is commonly used for automotive components to meet crash requirements with minimal mass addition to the vehicle. Press hardenable steel (PHS) is capable of forming complex geometries with deep sections since the forming takes place at elevated temperatures up to 900 degrees Celsius (in the Austenitic phase). This forming process is known as hot-stamping. The most commonly used PHS grade is often referred to as PHS1500. After hot-stamping, it is typically required to have a yield strength greater than 950 MPa and a tensile strength greater than 1300 MPa. Most automotive design and material engineers are familiar with PHS, the hot-stamping process, and their capabilities. What is less known is the capability of 3rd Generation advanced high strength steels (AHSS) which are cold stamped, also capable of forming complex geometry, and are now in the process of, or have recently completed, qualification at most automotive manufacturers. This paper will show that U. S. Steel’s Generation 3 steel with 980 MPa minimum tensile strength (980GEN3) has comparable crash performance to PHS1500 when used for automotive body-in-white (BIW) Pillars in a sedan. This paper will also show that these 980GEN3 BIW Pillars can achieve the same complex geometry as PHS1500, that the springback can be predicted and controlled, and that prototype parts can be assembled into a vehicle build and physically crashed without issues. Furthermore, correlation between cold stamped 980GEN3 BIW Pillars and forming simulation results will also be discussed.