Constitutive Modeling of the Flow Stress of GCr15 Continuous Casting Bloom in the Heavy Reduction Process

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UCTION

FINITE-ELEMENT (FE) models have been widely used to simulate and analyze steel hot-forming processes, such as forging, rolling, extrusion, and casting. To guarantee the accuracy of the thermomechanical simulation results, a constitutive equation is necessary to describe the steel flow behavior under various loading conditions during the modeling process. The constitutive model based on the phenomenological or semiphenomenological approach has been widely used in simulation processes because the form of this type constitutive model is easily applied in FE models. Many constitutive models, such as the Sellars–Tegart model,[1] the Anand model,[2,3] the Johnson–Cook model,[4] the Zerilli–Armstrong model,[5] and the Fields–Backofen CHENG JI, ZILIN WANG, CHENHUI WU, and MIAOYONG ZHU are with School of Metallurgy, Northeastern University, 3-11, Wenhua Road, Shenyang 110819, China. Contact e-mail: [email protected] Manuscript submitted June 27, 2017.

METALLURGICAL AND MATERIALS TRANSACTIONS B

model,[6] have been widely applied in simulations of hot-working processes. In recent years, researchers[7–9] have modified or simplified these conventional constitutive models, resulting in a more accurate model and significantly enhanced model methodologies. The constitutive relationships for continuous casting processes have also been investigated and are usually derived from tensile test results, which do not accurately describe compressive deformation. Kozlowski et al.[10] summarized and analyzed four elasto-viscoplastic constitutive models for the steel continuous casting process. The experimental data used in the modeling constitutive relationship were the tensile test data and the creep-test data reported by Wray[11] and by Suzuki et al.,[12] respectively. Han et al.[13] originally proposed a constitutive model for a hot-forging process based on the research of Garofalo[14] and Uehara et al.[15] However, this model has also been applied in the continuous casting process by many researchers[16–19] to quantitatively describe the thermal deformation behavior of continuous casting steel,[16] to precisely estimate the critical fracture stress of the solidifying shell,[17] to predict the flow behavior of the d and c phases at various temperatures and strain rates,[18] and to

investigate broadening of the slab.[19] Thomas et al.[20] employed constitutive models by Anand to simulate the thermal behavior of a solidifying shell during steel solidification in a slab continuous casting mold. The current authors applied this model to describe the creep of shell deformation in a mold.[21] Recently, heavy reduction (HR) technology, which imposes a larger reduction amount at and beyond the solidification end of the strand, was developed for healing the solidification shrinkage cavity and improving the center density.[22] In this process, the strain rate is approximately 103 to 101 s1, which is significantly different from that in the regular continuous casting process (106 to 103 s1[10]) and that in the hot-working process, in which th