During sheet metal forming of multiphase steel for automotive application, more and more often failure happens prior to necking, so that the forming limit diagram is not an appropriate measure for cold formability anymore. Alternatively, the modified Bai Wierzbicki (MBW) model can be applied since it belongs to the group of coupled continuum damage mechanics models. It considers all invariants of the stress tensor both in the yield potential and in the crack initiation criterion. In this publication the model is successfully applied to characterize the cold formability of a dual phase steel of the grade DP600. Additionally, a procedure is described which delivers the parameters of the macroscopic MBW model's damage initiation criterion by simulations of representative volume elements. In these simulations, the underlying physical mechanisms of crack initiation and propagation are quantitatively described.