Mechanical Properties and Collision Deformation Performance of 980 MPa-grade High-Strength Steel Sheet

This report describes the mechanical properties, formability, weldability, and collision deformation performance of the new 980 MPa-grade steel sheet used in the front side frame of an automobile’s body framework. In order to determine the material properties of the 980 MPa-grade steel sheet needed for use in the front side frame, the study used special bending tests to find the threshold values at which cracking occurred during collision deformation. It was found that these special bending characteristics correspond closely to hole-expansion properties and it is necessary to increase hole-expansion properties of the new 980 MPa-grade steel sheet. The new 980 MPa-grade steel sheet with high hole-expansion properties has an enhanced forming limit curve compared to conventional 980 MPa-grade steel sheet, and can be formed to the shape of the front side frame. In collapse tests simulating collision deformation, the steel sheets demonstrated the necessary performance without cracking. The new material makes it possible to use 980 MPa-grade steel sheet for components such as the front side frame of an automobile’s body framework, which are challenging to form and undergo significant deformation in collisions.