Fast algorithms for phase transformations in dual phase steels on a hot strip mill run-out table (ROT)

The hot rolling of dual phase steel, alloyed with 0.064% C, 0.05% Al, 0.48% Cr, 0.93% Mn, and 0.41% Si, was simulated by a deformation dilatometer. To model the ferrite transformation behaviour on the run-out table, the rate law approach proposed by Leblond and Devaux was employed. It models the ferrite transformation kinetics as a function of holding temperature and austenite conditioning, which is achieved by varying the austenite grain size and retained strain. Its transformation kinetics during cooling to the coiling temperature was investigated by varying the carbon content of the remaining austenite. The martensite transformation kinetics was also modelled by Leblond and Devaux's approach with a parameter coupled to the Koistinen–Marburger model. The modelling shows that this alloying concept allows a large process window for both temperature and austenite grain size. Finally, a selected set of processing parameters was chosen and transferred to a pilot rolling mill. The mechanical properties of the rolled sheets are satisfactory.