各種原料の燒成過程における物理牲の變化

珪石煉瓦のMatrixの研究 (第3報)

抄録

In the first report, we have proposed “matrix brick” which is made of quartz flour through the 1600 hole/cm² sieve mixed with abt. 5% of CaO. In mixing this “matrix” with varions amounts of coarer grains (400-1600 hole/cm²), we found that the sample cones containing less than 30% of “matrix” are more refractory, and therefore such bricks are good for use in open-hearth roof.
In the second report, results of dilatometric experiments and microscopic observations of matrix bricks are given. There are two remarkable periods of mineral development during the sintering of matrix bricks; i.e.
1000-1200°C cristobalite development
1200-1400°C tridymite development
The formation of tridymite was detected by
T₁-inversson (α→β₁ trid.) in samples fired at lower temperatures
T₂-inversion (crist.→trid.) in samples fired at higher temperatures
By comparing parmanent expansions at 1000°C in reheating the bricks, a minimum was found in samples fired at 900-1100°C, Milk of lime in green body gradully absorbs CO₂ and is converted into CaCO₃ at abt. 600°C, then it decomposes. At abt. 800-900°C, formation of calcium silicate was concluded from a marked shrinkage, and at abt. 1400°C it became visible under a microscope in forming ring-like shaped crystals. When fired at above 1400°C, calcium silicate diffused into the matrix, but when cooled, it recrystallized again.
In the present (third) report, experimental results of parmanent expansion, porosity, apparent density and permeability are given.
In the firing range of 1100°-1200°C, the apparent specific gravity of the matrix bricks has decreased from 2.60 to less than 2.40, but the porosity has also decreased and the crushing strength increased. Because there is no great change of porosity during firing, it is advisable to make quality control in green body. Increase of CaO content is good for crystal growth of Tridymite but rather decreases the it's amount, and makes expansion smaller.