Sintering,structure, and properties of cast granular oxide refractories

Conclusions The interrelationship between the composition, sintering behavior, structure, and mechanical strength of a number of cast granular ceramics and refractories was studied.The contact interaction mechanism was studied in the system of sinteredmatrix-constant-volume filler, and the possible modes of crack propagation and the nature of crack formation in the materials containing granular fillers were presented.It was established that the magnitude of the uncompensated (or nonadmissible) shrinkage is the parameter that determines to a large extent the strength properties, thermal stability, and the structure.A new porosity index was suggested for evaluating granular materials, viz., the porosity formed due to microcracks and discontinuities in the contact regions.The dependence of the strength properties of the cast granular materials on a number of technological parameters was analyzed. It was shown that such materials are better than the compacted ones because of the possibility of attaining ultimate strength values up to 70–90 MPa under bending and up to 400–550 MPa under compression. In this case, the shrinkage during sintering does not exceed, 0.5–1%, owing to which it is possible to obtain large-sized products having high dimensional accuracy.Translated from Ogneupory, No. 7, pp. 10–16, July, 1985.