Huazhi Gu

The Interfacial Behavior of Alumina-Magnesia Castables and Molten Slag under an Alternating Magnetic Field

Electromagnetic metallurgical technology has become an important method for the smelting of high purity steel with the development of metallurgical technology. The electromagnetic fields existing extensively in the steelmaking process can not only affect the smelting efficiency and the cleanness of steel, but also the interfacial behavior between the refractory and the molten slag. Focusing on alumina-magnesia castables, an important lining material in ladles, the interfacial behavior between the castable and different ladle slags with or without an AMF is studied in this paper. The results showed that the slag corrosion and especially the slag penetration of the alumina-magnesia castable are more severe under an AMF. Moreover, an AMF accelerates the migration of Fe, Mn and their oxides from the molten slag to the castable. Meanwhile, some low melting point phases such as diopside and anorthite form in the corrosion layer of the castable, which was deduced to accelerate the slag corrosion and penetration of the alumina-magnesia castable.

The Influence of Thermal Radiation on Effective Thermal Conductivity in Porous Material

Effective thermal conductivity is an important parameter of porous materials for measurement of heat insulation performance. Two-dimensional geometrical models based on micrographs of real material were constructed in this paper and the finite element approach was applied for thermal analysis, the effective thermal conductivity was calculated. The influence of radiation heat transfer, temperature, and porosity on thermal conductivity were analyzed. The results show that conduction heat transfer plays an important role in total heat transfer and the influence of radiation heat transfer was small at low temperature. Because of the increase in radiation heat transfer, the temperature gradient decreased obviously at high temperature and the heat flux lines passed through the pores and became relatively smooth; thus the radiation heat transfer plays an important role in total heat transfer at high temperature and the influence of radiation heat transfer cannot be ignored. Thermal conductivity for a high porosity value will be greater than thermal conductivity for a low porosity value at high temperature. This paper provides guidance for predicting thermal conductivity and reducing the heat transfer efficiency of porous materials at high temperature.

Corrosion Mechanism of Foamed Slag on the Lightweight Corundum-Spinel Castable

Development of lightweight linings for metallurgical furnaces is an important research direction in the development of refractory materials. In the steelmaking process, slag foaming is a common phenomenon, and it usually plays a positive role. However, because of the reactions between refractories and slag, the corrosion of wear lining refractories is not only related to the safety and stable operation of high-temperature furnaces but also affects steel quality. Foamed slag is likely to affect refractory corrosion, especially lightweight refractories containing lightweight porous aggregates. In this study, the slag corrosion experiments of lightweight corundum-spinel castable were performed in contact with the ordinary and foamed slag respectively and the foamed slag caused more serious corrosion to the lightweight corundum-spinel castable. Based on the corroded microstructure and Marangoni effect, slag corrosion mechanism was analyzed systematically, and could provide the basis for foamed slag resistance.