Investigation of the Ultimate Strength of Periclase-Carbon Refractory Materials and Analysis of Their High Temperature Strength

A setup for determining the ultimate strength of refractory materials in compression at high temperatures is examined. The value of the ultimate strength of periclase-carbon materials in compression in the temperature range 20 – 500°C are presented. The fracture process and strength are analyzed. High-temperature plants are lined with refractory materials. In addition, the service life of many high-temperature plants is determined by the service life of the lining. Optimization of the factors influencing the stability of the lining makes it possible to increase the working run of a plant several-fold. Even without changing the form of the refractory a significant result can be achieved by simply improving the operating conditions (temperature regimes). Physical factors such as expansion and cracking arise in the case of thermal action on furnace lining. It becomes necessary to operate the plant continually without damaging the integrity of the lining in the working chamber and the technical-economic indices of the process. To prevent the lining from being damaged by the stresses arising during heating it must be operated in a regime where stresses grow at a rate below their relaxation rate. It is important to calculate the values of the thermal stresses when calculating the rate of heating. The stress values calculated using computational relations are compared with the admissible values, and on this basis a conclusion is drawn concerning the rate of heating of the plant. The average heating rate of high-temperature plants is about 60 Kmin [1]. The ultimate strength of the material is used in the calculations as the admissible value of the stresses arising with a change in the temperature field. Knowing the exact temperature dependence of the ultimate strength of the materials used it is possible to determine the maximum rate of heating of a plant (according to the conditions under which stresses arise). The results of tests performed on carbon-containing refractories produced by ‘Kombinat Magnezit’ JSC are presented in [2]. The characteristics and the stability of the parts are indicated and it is noted that the refractories have a high resistance to thermal shearing in the presence of temperature fluctuations. It should be noted that the ultimate strength in compression (ranging from 19 to 61 MPa for different types of refractories) is presented only at temperature 20°C. Thus, the plant data do not show the dynamics of the change in this parameter as a function of temperature.