| In the development of steel technology, continuous casting has become the main process route for mass production of steel today. 1100 million tons of steel was casted annually corresponding to more than 90% of the total steel production in the world. Like any other new process, continuous casting is efficient. However, it also introduces new types of defects, like oscillation marks, corner cracks, facial cracks, macro inclusions, etc. Currently, a wealth of experience in industry has been developed to improve slab surface qualities. Most of the research has indicated that the final cast slab surface is strongly dependent upon the heat release rate from the steel strand, i.e., heat transfer rate from the partially solidified strand to caster mold.; Mold fluxes have been widely used to infiltrate in between the caster mold and strand to moderate the heat transfer rate. The main goal of this study is to explore the effects of mold flux composition and solidification on heat transfer rates, especially on radiative heat transfer rates.; It has been shown in the work that both solid crystalline and glassy phase films have different thermal resistance and affect the radiative heat transfer rate, and the crystallization behavior of the mold flux is the primary factor affecting the overall heat transfer rate in continuous casting. By using an infrared radiation emitter, which was developed at Carnegie Mellon University, a radiative heat flux was applied to a copper mold covered with solid mold flux disk to simulate the radiative heat transfer phenomena in continuous casting. The solid slag disk could either be glass or a mixture of glass and precipitated crystals. The kinetics of mold slag crystallization was studied by the recently developed double hot thermocouple techniques (DHTT) as well. It has been investigated that the effect of full crystallization of a slag disk is able to reduce the heat transfer rate by 20% in the meniscus area in this work. By studying the heat transfer mechanism proposed here, the hypothesis could be used in real casting industry to help moderating heat transfer rates to eliminate or minimize oscillation marks, to achieve a defects free final slab. |
