Numerical Simulation of Bulging Deformation for Wide-Thick Slab Under Uneven Cooling Conditions
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N the continuous casting process, the bulging deformation of a solidified shell between rolls inevitably occurs under the load of ferrostatic pressure, as illustrated in Figure 1. If the tensile strain on the solidification front, caused by bulging and other factors, exceeds the critical threshold value, internal cracks occurs.[1–3] Additionally, a bulging deformation, especially one that occurs near the strand solidification end, significantly aggravates the slab centerline segregation.[4,5] It compresses the mushy region and promotes the solute-enriched interdendritic liquid to flow into the central part of the strand. As a result, the level of the centerline segregation is dramatically increased. Furthermore, bulging deformation decreases the equipment life owing to the greatly increased mechanical load between the strand and rolls. Due to the difficulties in accurately measuring the bulging deformation in practical continuous casting,[6] only a few experimental measurements have been reported.[7–10] For this reason, various mathematical analysis methods were widely adopted by previous researchers to study this deformation behavior to provide a theoretical basis for optimizing the process parameters and to decrease the adverse effects from bulging deformation. Verma[1] and Han[2] studied the
CHENHUI WU, CHENG JI, and MIAOYONG ZHU are with the School of Metallurgy, Northeastern University, 3-11, Wenhua Road, Shenyang 110816, China. Contact e-mail: [email protected] Manuscript submitted April 23, 2017.
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strain status at the solidification front caused by bulging deformation and other factors by using a strain analysis model. Based on the theory of a bending beam, Yoshii[11] and Sheng[12] calculated the bulging deflection of the slab, and Sheng proposed a new formula for bulging deflection with clear physical meaning, after evaluating some frequently used equations. Han[13,14] investigated the influence of bulging of the solidified shell on slab deformation in the straightening zone of the continuous caster and the influence of roll misalignment on slab bulging deformation. Based on the theory of a 2D plate, Xu[15] and Wang[16] calculated the bulging deflection of the slab, and Xu deduced an analytical model for calculating the casting withdraw resistance. All of the above works mainly adopted an analytical method. To further improve the calculation accuracy and revealing the bulging behavior more comprehensively, finite element method began to be adopted by researchers.[17,18] A series of 2D[19–23] or 3D[24–32] finite element models were then developed to quantitatively estimate the bulging deflection or strain status of the solidified shell. During these works, Lee[20] and Miki[22] clarified the origin and characteristics of unsteady bulging. Bellet[21] calculated the thermomechanical state of steel all along the continuous casting machine using a global non-steady-state approach. He[23] explained the mechanism of bulge deformation in continuous slab casting by introducing positive creep a
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