Thermal properties and electrical conductivity of refractory balls

Apr 11, 2024

Thermal properties and electrical conductivity of refractory balls

1.1 Thermal expansion

    The GB/T7320 standard has two definitions: linear expansion rate (the relative change rate of the diameter of the refractory ball between room temperature and the test temperature, expressed in %), and average linear expansion rate (the length of the specimen for every 1°C increase in temperature between room temperature and the test temperature). relative change rate, unit is 10-6/℃)

    The measurement principle of the GB/T7320 standard: heat the sample to the specified test temperature at a specified heating rate, measure the change in the length of the sample as the temperature increases, and calculate the linear expansion rate of the sample as the temperature increases and the specified temperature. The average linear expansion coefficient of the range and draw the expansion curve.

    1.2 Thermal conductivity

    Thermal conductivity is defined as: the heat transferred through the unit area of the refractory ball in the direction of heat flow under unit temperature gradient per unit time.

    The principle of measuring the thermal conductivity is: based on Fourier's basic principle of the stable thermal conduction process of a one-dimensional plate, measure the heat flow in the one-dimensional temperature field per unit time in the steady state, flowing longitudinally through the hot surface of the sample to the cold surface and then flowing through the central calorimeter. absorbed heat. The heat is directly proportional to the thermal conductivity of the sample, the temperature difference between the hot and cold surfaces, the area of the heat absorption surface of the central calorimeter, and inversely proportional to the thickness of the sample.

The physical meaning of thermal conductivity refers to the heat passing through unit vertical area per unit time under unit temperature gradient. Thermal conductivity is a physical index that characterizes the thermal conductivity of refractory balls. Its value is equal to the heat flow density divided by the negative temperature gradient.

    1.3 Heat capacity

    Any substance will heat up when heated, but different substances with the same mass require different amounts of heat to raise the temperature by 1°C. It is usually expressed by the amount of heat (KJ) required to heat 1kg of material to raise its temperature by 1°C under normal pressure, which is called heat capacity (also called specific heat capacity).

    1.4 Conductivity

    Refractory balls (except carbon and graphite products) are poor conductors of electricity at room temperature. As the temperature increases, the resistance decreases and the conductivity increases. The improvement is particularly significant above 1000°C. If heated to a molten state, it will show great electrical conductivity.


    2. Mechanical properties of refractory balls

    The mechanical properties of refractory balls refer to the strength, elasticity and plastic properties of refractory balls at different temperatures. The mechanical properties of refractory balls are usually judged by testing indicators such as pressure resistance, flexural resistance, wear resistance and high-temperature load-soft creep.

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