Effect of Layer Cooling Control Process on Warpage of Q690D Low Carbon Bainitic Steel

In this paper, a coupled finite element model of temperature phase transformation stress strain for low carbon bainitic steel plate during laminar cooling is established by extending Avrami transformation kinetic model and combining thermal strain and transformation strain. Elastic strain, thermal strain, elastic strain caused by phase transformation, plastic strain and plastic strain induced by phase transformation are fully considered. The newly developed model was used to simulate the numerical changes of temperature, phase transformation, stress / strain and warpage along the thickness direction of low carbon bainitic steel under three cooling modes, and the influencing factors of warpage were analyzed quantitatively. The results show that the temperature difference and phase transformation are uneven in the thickness direction of the steel plate during asymmetric cooling, and the stress / strain asymmetry is the main factor affecting the warpage. Unsymmetrical cycle cooling can effectively alleviate the warpage of plate shape to a certain extent.