Analysis of the Cooling Modes of the Lining of a Ferroalloy-Casting Ladle

Abstract

An important element of the operation of high-temperature aggregates are modes that change over time. During these modes, maximum temperature changes are recorded in the cross-section of the lining of the aggregate. The difference in temperature leads to the formation of thermal stresses, which are the main reason for the repair of aggregates. During rapid heating, the inner layers of the lining are subjected to compressive stresses, while during rapid cooling, these layers experience tensile stresses. Under the same conditions, rapid cooling of the lining is more critical, since refractories have poor resistance to tension. The purpose of the study is to calculate and analyze the thermal stresses that arise during cooling of the casting ladle lining. The stresses are determined based on the calculation of the unsteady temperature field of the lining. Thermal stress values are necessary for analysis of the current cooling rates of casting ladles and subsequent development of optimal cooling modes for the lining. To solve the heat conductivity equation, a numerical method was chosen using an implicit four-point difference scheme. To study the cooling process of the casting ladle lining, temperature measurements were carried out in the zone of the greatest wear of the lining. Under conditions of natural convection, cooling of the casting ladle lining occurs unevenly. Cooling schedules during natural convection are characterized by significant unevenness and high rates of temperature decrease. The cooling rates of the inner surface of the lining at the initial stage of cooling significantly exceed the values recommended in the technical literature. Such cooling rates lead to the appearance of significant thermal stresses in the lining. For a refractory that has not been in service, the maximum thermal compressive stresses exceed the ultimate compressive strength by 1.27 times, and the tensile stresses exceed the corresponding limit values by 4.4 times. For refractories that have worked three fuses in the ladle lining, the maximum thermal compressive stresses exceed the ultimate compressive strength by 1.28 times, and the tensile stresses exceed the corresponding limit values by 3.19 times. The studied cooling modes for the casting ladle lining are unacceptable for operation. Cooling, taking into account the indicated rates, leads to the destruction of the lining material. To increase the resistance and duration of the working campaign of casting ladle linings, it is necessary to develop cooling modes for the lining at speeds at which the resulting thermal stresses do not exceed the strength of the refractory materials.