Effects of Variation of Heat Flux Released from the Meniscus on the Surface Shape of the Solidified Shell During Continu
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Effects of Variation of Heat Flux Released from the Meniscus on the Surface Shape of the Solidified Shell During Continuous Casting Yong‑tae Kim1 · Kyung‑woo Yi1,2 Received: 10 May 2020 / Accepted: 17 August 2020 © The Korean Institute of Metals and Materials 2020
Abstract Mold oscillations, widely used in continuous casting for infiltrating the mold flux between the mold and the solidified shell, change periodically the heat flux from the meniscus to mold. These variations of the heat flux affect the solidification behavior near an initial solidification position. Because the surface shape of the solidified shell is influenced by the initial solidification behavior, it is important to understand the relation between the mold oscillation, the heat flux and initial solidification behavior. In the present study, we developed a numerical model that simulates the flow and thermal behavior of the mold flux near the meniscus. Using this model, we analyze the effects of the variations of the heat flux from the meniscus on the initial solidification position and suggest the formation mechanism of the oscillation marks (OMs) and the hooks. Also, we will present quantitative results about the depth of the OMs and the length of the hooks at the conditions used in the present study. The factors that influence the hooks’ types and the causes of the irregularity of the shell surface are also discussed. Keywords Metals · Continuous casting · Numerical analysis · Oscillation mark · Hook
1 Introduction Mold flux, which is used during continuous casting of steel, has important roles such as lubricant and a heat transfer medium between a mold and steel melt or a solidified shell [1]. If the mold flux doesn’t play these roles properly, troubles during the process could happen such as a break-out [2, 3] or surface defects [4, 5]. So, to infiltrate the mold flux stably into the channel between the mold and the shell, mold oscillations are required during the process [1]. These oscillations change the flow pattern and thermal behavior of the mold flux near meniscus and these changes result in a characteristic periodic surface shape of cast products like waves, so-called oscillation mark (OM) [6, 7]. Also, it was reported that the surface and the sub-surface qualities are strongly affected by the OM [5, 7, 8].
* Kyung‑woo Yi [email protected] 1
Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Republic of Korea
Center for Iron and Steel Research, Research Institute of Advanced Materials (RIAM), Seoul National University, Seoul 08826, Republic of Korea
2
Previous studies have proposed various hypotheses about the formation mechanisms of the OM and the hook [6]. Common in these hypotheses is that the OM shape is determined by the trajectory of an initial solidification position. The initial solidification position depends on the variations of meniscus-shaped interfaces between the mold flux and the melt. Also, the variation of the meniscus results from various parameters such as thermal be
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