Variable Gauge Rolling and Continuous Annealing Process for Double Phase Steel DP590

A roll gap setting equation for variable gauge rolling was established based on the discretization control method; A variable gauge rolling roll gap control model was given by building the load-frees closed-loop and loaded roll gap closed-loop control formula. The single variable gauge zone variable gauge rolling were carried out on double steel DP590 by laboratory four high cold rolling mill, and then simulated continuous annealing experiments for cold rolled sheet, that is TRB sheet, was executed. Microstructures and mechanical properties of different positions of TRB sheet after annealing were studied. The results show that, the maximum thickness deviation in 50 mm variable gauge zone of TRB sheet was below 0.08 mm and the length deviation below 0.3 mm. The difference of temperature between setting and actual values was small, and the difference between the thin zone and the thick zone was small; the tensile strength increased by 65 MPa and elongation increased by 2.8% in thin zone than others, and the almost same yield strength as that of in the thick zone. The continuous annealing process should be determined by the thickness of thick zone for cold rolled dual phase steel TRB sheet, which being more conducive to the mechanical properties control.