Investigation of Damage-Controlling Process-Parameters During Cold Rolling on the Impact Toughness of DP800 Steel Under Crash Loading Stress States

The damage introduced into components during forming operations is often critical for the component performance in service. Because these performance properties depend strongly on the local stress state, it is important to consider this while evaluating material or components produced under specific processing chains. In this paper, we present an approach to correlate the process parameters during cold rolling with the crash impact toughness of DP800 steel, using a straightforward approach. Already hot-rolled S355 steel is cold-rolled with varying pass reductions and then heat treated to DP800 steel. In order to account for a relevant stress state, numerical simulations of a crash box are used. The critical stress state is extracted and assigned to an impact tensile specimen by varying the side notch of the sample. The damage quantification using density- and SEM-measurements shows a clear difference between the individual material states, but there is no fully identifiable correlation between damage and energy absorption in the impact tensile tests. It is assumed that other parameters influenced by rolling (e.g., strain hardening) have a greater influence than the damage. Further studies will be conducted to clarify under which loading conditions the damage is more likely to have a strong correlation with the performance capability.