A Study for Initial Solidification of Sn-Pb Alloy During Continuous Casting: Part II. Effects of Casting Parameters on I
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cts, such as transverse cracks, longitudinal cracks, deep oscillation marks, and depressions, are directly associated with the high temperature thermodynamics occurring in the mold, and the initial shell solidification in the vicinity of the meniscus in continuous casting has significant effect on the shell surface quality.[1,2] The formation of surface defects has a direct relationship with the irregular shell solidification of melt in the upper mold.[3–6] Therefore, casting parameters together with mold flux properties determine the thermodynamic conditions of initial solidification and affect initial shell growth. Many studies[7–12] have been conducted to investigate the initial shell solidification and the mechanism of surface defect formation. Shin et al.[7] have studied the influence of mold oscillation and superheat on powder consumption, OMs depth and hook characteristics during industrial casting trials; it suggests that high oscillation frequency results in thinner, shallower OMs and hooks. Ramirez-Lopez et al.[8,9] reported that the heat flux increased gradually during negative strip time (NST), but decreased during positive strip time (PST), and the slag infiltration starts at the begging of NST; the depth of the OMs decreased with the increase of mold DONG ZHOU, HAIHUI ZHANG, and KEN CHEN, Graduate Students, WANLIN WANG, Professor, FANJUN MA and LEJUN ZHOU, Post Doctors, are with the School of Metallurgy and Environment, Central South University, P.R. China. Contact e-mail: [email protected] Manuscript submitted October 16, 2013. Article published online April 1, 2014. 1048—VOLUME 45B, JUNE 2014
oscillation frequency. Ferreira et al.[10] focused their research on the effect of melt superheat on metal/mold heat transfer coefficient during solidification of a Sn-10 wt pct Pb alloy in a static mold, their results showed that a higher heat transfer coefficient was obtained in horizontal direction, and the reverse situation was observed in vertical upward direction, as the melt superheat increased. Besides, the results from Zhang et al.[11] indicated that steel superheat significantly affects solidification structure and solidifying end point, which is also associated with the heat transfer across mold. Badri et al.[12,13] found that the characteristic of OMs holds a uniformly corresponding relation with the high frequency fluctuation of heat flux across the mold at the meniscus through an experimental mold simulator; however, the detailed study of the influence of casting conditions on the OMs has not been conducted. Most of those studies were based on post-occurrence analysis and lack of transient in situ observation, and very few works have been conducted to systematically investigate the detailed relationship between casting parameters, responding heat transfer and corresponding initial solidification. Therefore, the study regarding to the effect of casting temperature, mold oscillation frequency, and stroke on initial solidification as well as shell surface was conducted in this article by using the previous developed mold s
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