Design of process parameters for dual phase steel production with strip rolling using the finite-element method

Dual-phase steel are low-carbon micro-alloyed steels, characterized by a ferritic multiphase structure (bainite and residual austenite) in which martensite is dispersed. The dual-phase structure depends on the chemical composition of the steel, and on thermo-mechanical treatment realized with lower rolling temperatures. The properties derived from this microstructure give high performance to dual-phase steels in cold-forming applications. In this work the authors propose an approach to simulate tandem rolling for understanding the influence of the process parameters on the thermo-mechanical treatment. The approach is based on the finite-element method (FEM); two models have been developed, the first being a coupled thermo-mechanical model, which describes the behavior of the strip during its travel in each stand of the rolling train; whilst the second is a thermal model, which analyzes the strip transfer between two consecutive stands. The approach has been used also to verify how an existing rolling plant can be adapted to obtain dual-phase steels: the characteristics parameters obtained from an experimental tandem rolling process for dual-phase steel production have been used to design a new rolling process on an existing rolling plant, obtaining the desired thermal cycle of the material during the process.