Abstract: To investigate the formation of internal cracks in steel billets during soft reduction with liquid core, fully coupled thermomechanical finite element models were developed by Abaqus/Explict, and sensitive temperature range of internal crack was calculated by solidification phase transition model. With the finite element models, the temperature distribution, the stress and strain states in the billet were calculated. The relation between internal cracks and equivalent plastic strain, as well as maximal principal stress was analyzed. The results indicate that internal cracks will be initiated when the accumulated strain exceeds the critical strain or the applied tensile stress exceeds the critical fracture stress during solidification. The results can provide references for the optimization of soft reduction in strand deformation distribution and improving the internal quality of the strand.

Key words: billet, soft reduction, internal crack, formation, finite element