Abstract
The resistance of refractories to spalling is better compared by direct methods than by formulae based on theories, since the formers are more reliable than the latters. The present authors have proposed a new method of testing the resistance. Several magnesite bricks on market and experimental magnesite bricks have been tested by the method.
(1) Spalling test. Small test pieces are heated at about 1000°C to decompose basic carbonates. After cooling, modulus of elasticity at room temperature (E1) is determined. Then they are suddenly put in a furnace 900°C hot, are heated at the temperature for 10min., are cooled on a fun for 6min., are left in room for 15min., and are dried. After repeating 4 more cycles of these proceedures, moduluo of elasticity at room temperature (E2) is determined. Spalling tendency (S) is expressed by the formula, S=100(E1-E2)/E1.
(2) The test is delicate and is free from errors due to the inequality of the test pieces, since each test piece is examined for both E1 and E2.
(3) Among magnesite bricks on market Radex is particularly excellent.
(4) If the proportion of the fine powder is kept constant, the effect of the difference in the fineness of the coarse grains on the resistance of the refractories to thermal shock is slight.
