An Investigation of the Mold-Flux Performance for the Casting of Cr12MoV Steel Using a Mold Simulator Technique
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THE property of mold flux is important in determining the surface quality of the strand during the process of continuous casting, as it can protect the molten steel from oxidation, prevent steel from freezing, and absorb inclusions from molten steel. Besides, it tends to lubricate the shell during the mold oscillation and moderate the heat transfer in the mold when it infiltrates into the mold/shell channel. The properties of mold flux, such as crystallization, heat-transfer ability, viscosity, melting behavior, and surface tension, are used to characterize the performance that the mold flux behaved in the mold. The crystallization of mold flux usually determines the structure and phase (glass, crystalline, and liquid) distribution of slag film in the mold wall/shell gap, which in turn controls the in-mold
LEJUN ZHOU and CHAO XU are with the School of Metallurgy and Environment, Central South University, Changsha 410083, P.R. China. WANLIN WANG is with the School of Metallurgy and Environment, Central South University, and also with the National Center for International Research of Clean Metallurgy, Central South University. Contact email: [email protected] CHEN ZHANG is with the Steelmaking Research Department, Research Institute, Baosteel Group Corporation, Shanghai 201900, P.R. China. Manuscript submitted November 19, 2015. Article published online May 22, 2017. METALLURGICAL AND MATERIALS TRANSACTIONS B
heat transfer and lubrication in the continuous casting mold.[1,2] The heat-transfer capability of mold flux affects the horizontal heat transfer in the mold greatly; an uneven heat transfer and rapid cooling of solidified shell can cause enormous thermal stress on the initial shell, especially for the casting of crack-sensitive high-carbon Cr12MoV alloy steel, which consequently causes cracks and other surface defects on the shell surface.[3,4] Viscosity is one of the most important properties of mold flux, as it determines the powder consumption and the lubrication of the mold oscillation.[5] The melting temperature range of the mold flux directly determines the thickness of liquid flux on the top surface of molten steel, which affects the behavior of inclusion absorption, heat insulation, and reoxidation protection.[6] The surface property of the mold flux usually not only influences the absorption of inclusions, but also affects the size and shape of the slag rim formed in the vicinity of the meniscus, etc.[7,8] In order to characterize the specific properties of mold flux, many techniques and methods have been developed. For example, differential thermal analysis (DTA),[9,10] single/double hot thermocouple technology (SHTT/DHTT),[11–13] and confocal scanning laser microscopy[14,15] were used to study the crystallization ability of mold flux. The Fourier transform infrared spectrometer,[16,17] infrared emitter technique,[18,19] inverse heat-flux simulator,[20] and several other thermal were conductivity measurement methods[21–23] VOLUME 48B, AUGUST 2017—2017
developed to investigate the heat-transfer behavior of mold flux.
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