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Título: Techniques for the continuous measurement of melt temperature
Autores: Choi, Hyeon-Soo
Fecha: 1991
Publicador: McGill University - MCGILL
Fuente:
Tipo: Electronic Thesis or Dissertation
Tema: Engineering, Metallurgy.
Descripción: Continuous temperature measurement of molten steel in new as well as existing steelmaking processes is not always feasible with current technology. However, it is a well known fact that molten steel temperature, especially during the continuous casting operation, can have a profound effect on the quality of the product. A knowledge of the instantaneous steel temperature in the tundish can serve as a valuable tool in the quest for better quality. With the implementation of statistical process control techniques such occurrences as breakouts, tundish freeze up or the nucleation of an extensive area of columnar grains in the cast section can be reduced.
However, conventional thermocouples cannot withstand the severe corrosion around the slag line for a sustained period of time. Even though the sensing wires that comprise the hot junction can, if well protected, be used for long periods of time without serious deterioration, a suitable refractory cover or sleeve must be applied to the thermocouple prior to using it.
For the present work, two methods for continuously measuring melt temperature were developed. One of these relies on deducing melt temperature while the other is based on providing a cooled sleeve for the thermocouple to minimize slag line corrosion. The first technique involves the use of multiple thermocouples embedded in a refractory section at various displacements. When the refractory is contacted by the melt, transient heat transfer is initiated through the section. By analyzing this transient behaviour with a suitable heat transfer model, it is possible to infer the temperature of the melt. A mathematical model that adequately describes this process has been developed and tested.
An alternative approach that was developed uses heat pipe technology to prevent the corrosion of the thermocouple probe through solidification of slag onto the heat pipe which can serve as a protector of the probe. Heat pipes are devices capable of transferring large quantities of heat with very small temperature differences. Advantages of the heat pipe when used as a heat transmission device are constructional simplicity, flexibility, high heat transport capability, and no need for external pumping device. The heat pipe consists of a closed evacuated tube, porous wicking material, and working fluid. Heating one part of the external surface leads to evaporation of the working fluid and the establishment of a pressure gradient within the heat pipe. The resulting pressure difference drives the vapor from the evaporator to the condenser where the pressure and temperature are slightly lower. The effective conductance of the heat pipe can be several orders of magnitude higher than that of an equivalent solid copper bar. In the second part of this thesis, the feasibility of incorporating heat pipe technology to solidify and maintain a thin layer of slag on the heat pipe while it is in operation is presented.
Idioma: en