シャモット種類差の光学ガラス坩堝素地の物理的諸牲質に及ぼす影響

光学ガラス熔融用坩堝に関する研究 (第4報)

抄録

Forty parts of bonding materials composing of equal parts of gairomé-, kibushi-, roseki-clay and kaolin (Table 1) were mixed to 60 parts of various chamottes (totaling 80 kinds in Table 2) previously graded and weighed-out as 21 parts of coarse, 6 parts of fine and 33 parts of very fine, and the drying, burning and spalling tests were made. The results are summerized as follows.
(1) At the burning temperature of chamotte within the range of this experiment, added alumiua scarcely sintered with kaolin and added quartzite aided sintering only when burned at high temperatures, but a remarkable sintering occured at lower temperatures in mixed chamotte of kaolin and feldspar.
(2) Amount of water required for the same fluidity of casting slips with the same bonding material, but differing in kinds and in burning temperature of chamotte, increased linearly with the water absorption of the chamotte used. The amount of the drying shrinkage water of bodies cast from these slips remained nearly constant irrespective of kinds and burning temperatures of chamottes.
(3) Between the bulk density of dried or burnt bodies and that of chamottes, a hyperbolic relation was found.
(4) Bodies of as small porosity as necessary for a practical use could not be made by chamotte of kaolin mixed with more than 20% of alumina, nor with quartzite unless they were burned at very high temperatures. Chamotte made of kaolin with each 5% of quartzite and feldspar gave, on mixing with bonding materials and burning at high temperature, more dense bodies than those with addition of 10% feldspar.
When the same mixture of 4 kinds of clays was used both for chamotte preparation and bonding material, more dense body was obtained than in cases when chamottes were made from single clay.
(5) Resistance against spalling was tested at two temperatures, that is the temperature at which glass batches are thrown-in and the other is that of withdrawal of pots from furnace. Addition of feldspar to raw clays for chamotte preparation decreased spalling resistance, whereas addition of alumina or quartzite gave rise to no definite tendencies but these were dependent on the composition of mix and the temperature at which the chamotte was burned.
(6) Spalling resistance seemed to be chiefly dependent on the physical properties of chamotte grain themselves, because adherence between chamotte and bonding material was not promoted by the use of the same raw material for the both of the two.
(7) When pot shell, which had been used repeatedly, was quenched or cooled slowly and used as chamotte, no denser bodies were obtained than the chamottes from single clay. The difference in the cooling manner of the pot was not reflected on the obtained bodies.
(8) Dense but spalling-resistant bodies could be easily obtained by selection of the proper chamotte. Chamotte made from roseki- or kibushi-clay was found to be good.