Deformation Characteristics of Steel Billets with Liquid Core

Abstract

To investigate the deformation characteristics of billets with liquid core during soft reduction and to clarify the correlation between internal cracks and deformation of the billet in the mushy zone, a fUlly coupled thermo-mechanical Finite Element Model was developed in ABAQUS , furthermore, casting and soft reduction tests were carried out in a laboratory strand casting machine. During soft reduction the temperature distribution, the stress and strain states in the billet were calculated, the deformation characteristics of the billet during soft reduction were determined and the relation between internal cracks and equivalent plastic strain as well as maximal principal stress was analysed. The results show that tensile stresses can develop in the mushy zone dUring soft reduction and the equivalent strain nearby the Zero Ductility Temperature (ZDT) increases with a decreasing solid fraction . Internal cracks can be initiated when the accumulated strain exceeds the critical strain and lor the applied tensile stress exceeds the critical fracture stress during solidification. In addition, the factors (reduction efficiency and internal cracks) that should be considered to determine the optimal parameter for the soft reduction were established.