The following investigation was carried out to evaluate work hardening and bake hardening in actual body components. Five pressings were made from mild steel and three different grades of high-strength steel with ultimate tensile strengths ranging from 380 to 470 N/mm2. The latter were a batch annealed Rephos steel and two other grades of continuously annealed dual-phase (DP) steel. Tensile test specimens were taken from these components to evaluate the work hardening and bake hardening. The results are contained in the report. A new Volvo standard for high-strength cold-rolled sheet steel has been introduced. To some extent, the formulation of the standard was based on the results of the investigation of work hardening and bake hardening. The form and application of the standard are described in the report.
This paper presents the results of a strength analysis of a newly developed steel structure featuring a special cross section achieved with the hydroforming process that minimizes the influence of springback. This structure has been developed in pursuit of further weight reductions for the steel body in white. A steel tube with tensile strength of 590 MPa was fabricated in a low-pressure hydroforming operation, resulting in thicker side walls. The results of a three-point bending test showed that the bending strength of the new steel structure with thicker side walls was substantially increased. A finite element crush analysis based on the results of a forming analysis was shown to be effective in predicting the strength of the structure, including the effect of work hardening.
The current worldwide availability of zinc coated sheet steel is presented along with applications in the automotive industry. Available grades of zinc coated steels and their manufacturing processes are also described. Long term needs of these products by the automotive industry are discussed. Types of zinc coated steels and their future availability are forecasted.