This paper presents the development of a multi-scale material model for a 980MPa grade transformation induced plasticity (TRIP) steel, subject to a two-step quenching and partitioning heat treatment (QP980), based on integrated computational materials engineering (ICME) principles. The model combines micro-scale material properties defined by the crystal plasticity theory with the macro-scale mechanical properties, such as flow curves under different loading paths. For an initial microstructure, the flow curves of each of the constituent phases (ferrite, austenite, martensite) are computed based on the crystal plasticity theory and crystal orientation with input parameters calibrated by micropillar experiments. Crystal plasticity predicted phase properties are then used as inputs to a state variable model which computes macro-scale flow curves while accounting for hardening caused by austenite transformation into martensite under different straining paths. The ICME model calibration is implemented in the LS-OPT analysis tool as a component of an optimization process. The final result of the ICME model calibration is a user-defined material subroutine, implemented in LS-DYNA finite element analysis tool, which can be subsequently used in vehicle crashworthiness performance simulations.