The Thermal Distortion of a Funnel Mold
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thermal distortion of the continuous casting mold from room temperature to steady operating temperatures can influence the behavior of the solidifying steel strand in many ways, but likely the most important of these is the narrow-face taper. Mold distortion has been investigated in billet molds,[1–6] conventional thickslab molds,[7–9] beam-blank molds,[10] and thin-slab molds with[11–13] and without[12,13] a funnel. Each mold shape has distinctive thermomechanical behavior, but in general, these studies have revealed the importance of the waterbox on the mechanical behavior of the system,[7] and the importance of mold distortion on mold taper,[2,5] mold cracks,[11,13] and steel strand cracks.[3,4] Distortion is less severe with lower mold temperatures, such as those caused by lower casting speeds[2,4] or thinner mold plates.[2,8] Coating layers have little influence on the mechanical behavior of the mold[8] because they are so thin. The highest temperature is generally found just below the meniscus; operating a caster with a metal level near a row of bolts increases inelastic deformation of the copper near the hot face.[2] Many previous mold distortion models assume elastic behavior. Incorporating inelastic behavior of the mold copper is needed to predict residual stresses and residual distortion, but it does not significantly affect the mold shape during operation.[11] Previous models often oversimplify important effects such as bolts, clamping, LANCE C. HIBBELER, Graduate Student, and BRIAN G. THOMAS, Professor, are with the Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61802. Contact e-mail: [email protected]. RONALD C. SCHIMMEL, Senior Process Engineer, is with Strip Mainland Europe DSP, Tata Steel, 1970 CA, IJmuiden, The Netherlands. GERT ABBEL, Knowledge Group Leader, is with Research, Development, and Technology, Tata Steel. Manuscript submitted November 22, 2011. Article published online July 20, 2012. 1156—VOLUME 43B, OCTOBER 2012
interfacial contact, and mesh resolution, but their largest deficiency is oversimplification of the mold and waterbox geometry. A complete quantitative analysis of thermal distortion during operation of a funnel mold, including realistic heat transfer, all of the important geometric details, proper constraints, shell/mold friction, and validation with plant measurements, has not yet been performed and is the aim of this study. II.
MOLD GEOMETRY
The main geometric features of the funnel-shaped mold and waterbox under consideration are shown in Figures 1 through 3. Although the waterbox is not perfectly symmetrical, only one fourth of the assembly was modeled. Asymmetric effects, such as variations in bolt tightening or mold alignment, and mold geometry changes to accommodate the level detector on one side are expected to be small. This mold has no coating layers. Except for the top row, each bolt is instrumented with a thermocouple set 20 mm from the hot face. Each narrow-face copper plate is cooled by four 14-mm diameter c
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