Three-dimensional (3-D) finite-element thermal-stress models have been developed to predict temperature, distortion, and residual stress in the mold of continuous casters of thin steel slabs, comparing both funnel-shaped and parallel molds. The mold shape and high casting speed leads to higher mold temperatures and shorter mold life than in conventional slab casters. This study investigates heat flux and the effects of mold shape on distortion and cracking of the thin-slab mold. In Part I of this twopart article, mold wall temperatures measured in the plant were analyzed to determine the corresponding heat-flux profiles in thin-slab molds. This data was then used in an elastic-visco-plastic analysis to investigate the deformation of the molds in service for the two different mold shapes. The model predictions of temperature and distortion during operation match plant observations. During operation, the hot-face temperature reaches 580 ЊC and heat flux varies from 7 to 4.5 MW/m 2 when casting at 3.6 m/min. The copper plates bend toward the steel, with a maximum outward distortion of about 0.3 mm. This occurs just above the center of the wide faces and is smaller than the distortion of a conventional slab mold. JOONG KIL PARK, Graduate Student, and INDIRA V. mity of heat transfer, with resulting improvements in mold SAMARASEKERA, Professor, are with the Department of Metals and life and reduction in sticking corner breakouts. Materials Engineering, University of British Columbia, Vancouver, Ozgu [4] instrumented a slab mold to measure a wide range BC, Canada V6T 1Z4. Contact

The formation of cracks in a funnel mold of thin-slab casting is investigated using metallographic studies and mathematical models. In Part II of this two-part article on thin-slab casting molds, short longitudinal cracks near the meniscus region of a thin-slab funnel mold are studied metallurgically. X-ray analyses revealed the formation of Cu-Zn brass on the copper matrix at high temperature where the crack initiated. Heat-transfer and thermal-elastic-viscoplastic stress models described in Part I are applied to investigate the temperature and stress fields associated with the cracks. Large cyclic inelastic strains were found in the funnel transition region just below the meniscus due to the slightly higher temperature at that location. The cracks then appear to have propagated by thermal fatigue caused by major level fluctuations at transitions. The stress and strain predictions suggest cycles to failure for molds for various hot-face temperatures. I. BACKGROUNDis fully closed. Won et al., [2] using a two-dimensional (2-D) coupled thermo-elasto-plastic finite-element model of con-JOONG KIL PARK, Graduate Student, and INDIRA V.Most previous research has focused on conventional cast-SAMARASEKERA, Professor, are with the Department of Metals and ing, which has relatively lower mold temperatures due to

A mathematical model has been developed for the prediction of cracks in the continuously cast steel beam blank through the fully coupled analysis of fluid flow, heat transfer, and deformation behavior of a solidifying shell. Fluid flow and heat transfer in the strand mold were analyzed with a threedimensional (3-D) finite-volume method (FVM). For the complex geometry of the beam blank, a body-fitted coordinate (BFC) system was employed. Thermo-elastic-plastic deformation behavior in the strand was analyzed using the finite-element method (FEM) based on the two-dimensional (2-D) slice model. The thermal fields of the strand calculated with the FVM were used in the analysis of the deformation behavior of the strand. Through the iterative analysis of the fluid flow, heat-transfer, and deformation behavior, the coupling parameter of the heat-transfer coefficient between the strand and the mold was obtained. In order to describe the thermophysical properties and thermomechanical behavior of steel in the mushy zone, the microsegregation of solute elements was assessed. Consequently, some characteristic temperatures of steel as well as variations of phase fractions with temperature were determined. The probability of cracking in the strand, originating from an interdendritic liquid film, was quantified as a crack susceptibility coefficient. Recirculating flows were developed in the web and flange-tip regions. The development of a solidifying shell in the flange-center region was retarded by the inlet flow from a submerged entry nozzle (SEN). An air gap was formed mainly near the flange-tip corner. Surface cracks in the web and fillet regions and internal cracks in the flange-tip region were predicted.

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In order to analyze the phenomenon of mold level hunching (MLH) during thin slab casting process, the variation of the mold level and the bulging of strand were measured and analyzed using Fast Fourier Transform (FFT) spectrum analysis. Both of mold level hunching and bulging had the same frequency and the specific frequency corresponded to the main roll pitch of the thin slab caster. The unsteady bulging was found to be a main reason of mold level hunching. The unsteady bulging profile through the full range of the caster and the height of mold level hunching were calculated using a heat transfer model and a continuous beam model. The effects of process variables on mold level hunching and the process condition of reducing mold level hunching were studied. The amount of mold level hunching increased as unsteady bulging increased due to the hunching of casting speed. An aperiodic roll pitch between segments could be effective in reducing mold level hunching.KEY WORDS: mold level hunching (MLH); unsteady bulging; FFT analysis; continuous beam model; thin slab casting; aperiodic roll pitch.