Selected Performance Criteria of Complex Heat-Insulating and Slag-Forming Mixtures
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Vol. 61, No. 3, September, 2020
HEAT ENGINEERING SELECTED PERFORMANCE CRITERIA OF COMPLEX HEAT-INSULATING AND SLAG-FORMING MIXTURES S. K. Vil’danov,1,2,3,4 L. V. Rogalyova,3 and A. N. Pyrikov2,3 Translated from Novye Ogneupory, No. 5, May, pp. 16 – 22, 2020.
Original article submitted February 02, 2020. A total thermal conductivity of a complex heat-insulating and slag-forming mixture has been calculated by accounting for the convective heat transfer component and thermal conductivity of the liquid oxide solution formed by melting the ingredients of the complex mixture. It was shown that the thermal conductivity of the complex mixture at an application temperature of 1,823 K remains at a rather low level of about 18.8 W/(m(K). Performance criteria of the complex mixture were formulated for various stages of its application, including supplying the mixture into a steel-pouring ladle, both a steel-pouring ladle and a tundish, and molds. It was established that by utilizing the complex mixture in a steel-pouring ladle, it becomes possible to reduce the metal cooling rate by 1.5 times. A performance criterion of the complex mixture used as a heat insulator in the tundish is associated with the level of negative deviation from the average temperature value obtained in a series of consecutive measurements (4°C). Performance criteria of the complex mixture used as a slag former in the tundish are related to an increase in the Al2O3 concentration of the oxide solution with an increase in the number of melts in the series, and a decrease in the FeO concentration to equilibrium values (about 0.5 wt.%). Provided there is a sufficient amount of the liquid oxide solution formed by the components of the complex mixture, no carburization of the molten metal with free carbon from the mixture takes place. Keywords: complex heat-insulating and slag-forming mixture, convective heat transfer, thermal conductivity of liquid oxide solution, steel-pouring ladle, tundish, carburization.
according to the basicity index (A). The latter can be expressed, for example, as A = (CaO + MgO + Na2O + K2O)/SiO2. In this case, the mixtures can be classified based on the analogy (although, rather conditional) with characterization of slags, e.g., neutral (A » 1), acidic (A < 1), and basic (A > 1). In this regard, instead of being a formal parameter, the mixture index (A) is rather an important energy indicator, which affects such physical properties of the mixtures as thermal conductivity, viscosity, density, etc. in both solid and liquid phases. A synergetic result of the effective performance of complex mixtures consists in providing low-level heat losses from the open molten steel surface, and formation of a stable fluidic layer of an oxide solution formed by melting an inorganic part of the mixture, which prevents the oxidation of liquid iron and steel alloying ingredients by atmospheric oxygen. In addition, the molten part of the complex mixture should not have a significant aggressive effect on the lining,
INTRODUCTION At present, complex me
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