Search

Ingot punching tests are performed on the already formed solid shell of a 450 kg steel ingot during solidification. Such test is designed in order to be representative of the thermomechanical conditions that give rise to macrosegregation during secondary cooling in steel continuous casting. In order to understand the different physical phenomena, a numerical model of the test has been developed, consisting of a two-dimensional planar finite element simulation in the median section of the ingot. A two-phase formulation has been implemented, in which the velocities of the liquid and solid phases are concurrently solved for. The simulation shows how solutes are redistributed through the central mushy zone of the ingot under the effect of the compression of the solid phase and the induced fluid flow resulting from the punching of the solid shell. By comparison with measurements of macrosegregation operated on two ingots of same initial composition but punched under different conditions, the simulation proves its capacity to reproduce the main experimental trends. However the predicted intensity of macrosegregation is lower than the one measured. Through discussion and analysis of different numerical sensitivity tests, critical material parameters and model improvements are identified in view of attaining better quantitative predictions in the future. [ABSTRACT FROM AUTHOR]

Experimental and numerical studies of hot tearing formation in steel are reported. On the one hand, an ingot punching test is presented. It consists in the application of a deformation at the surface of a solidifying 450 kg steel ingot. The experimental parameters are the displacement of the pressing tool, together with its velocity, leading to variations of a global strain rate. On the other hand, three-dimensional finite element thermomechanical modeling of the test is used. The time evolution of the strain tensor serves to compute an index to evaluate the susceptibility to create hot tears. It is based on the integration of a hot tearing criterion (HTC) that compares the local accumulation of strain with the expression of a critical value proposed in the literature. The main variable of the criterion is the brittleness temperature range (BTR) that refers to the solidification interval during which strain accumulates and creates hot cracks or tears. Detailed comparison of the simulation results with the measurements reveals the importance of the BTR for the prediction as well as excellent capabilities of the HTC to predict the formation of hot tears. [ABSTRACT FROM AUTHOR]