Application of a Three-Dimensional Microstructure Evolution Model to Identify Key Process Settings for the Production of Dual-Phase Steels

During the production of dual-phase (DP) steels, many transformation phenomena occur, each of which may significantly influence the final properties of the product. In the continuous annealing line, recovery, recrystallization, carbide dissolution, austenite formation, ferrite formation, and martensite formation may all occur. These processes can strongly influence each other. Furthermore, these processes may overlap. This metallurgical complexity makes both establishing the root cause of property variations and the design of new chemistries experimentally expensive and time consuming. With the recent introduction of a computationally efficient three-dimensional (3-D) microstructure evolution model that describes all transformation processes that occur during the processing of DP steels, a tool has become available to study in detail the effect of individual process parameters on the final microstructure. The model has been applied to study the transformation processes on the run-out table of the hot strip mill and in the continuous annealing line. In this study, emphasis has been placed on the role the hot-rolled microstructure plays in the final DP microstructure. Therefore, the model was extended to include the influence of manganese segregation on band formation. Details of the model and findings on the relation between the final microstructure and process settings are presented.