Abstract
Continuing the previous studies in cooperating with Kichinosuke Fukai (this Journal, 1934, 42, 339, 471 1935, 43, 55), one of the present authors S. Nagai has again farther studied on the steatite refractories in cooperating with Giichi Inoue, by using other samples. Some results were preliminarily reported in the present paper. The brief summaries are abstracted from the original Japanese paper, as following:
(1) Raw materials were again collected, i.c., (a) Talc samples from Manchoukuo, (b) Serpentine samples in Japan, (c) Shuganseki sample of Bowenite or Meerschaum type from Manchuokuo, & Korea etc., and these samples were tested on their chemical compositions and specific gravities. The results are shown in the following table 1.
From these results, the rational formulae xMgO·ySiO2·zH2O were calculated by making y of SiO2 as round number and obtained the following results: Talc E: 3MgO·4SiO2·1.5H2O, Talc F: 3MgO·4SiO2·1.1H2O, Talc G: 3MgO·4SiO2O·9H2O, Talc H: 3MgO·4SiO2·1.0H2O, Talc I: 3MgO·4SiO2·1.0H2O, Shuganseki B: 2.9MgO·2SiO2·1.9H2O, Serpentine D: 3MgO·2SiO2·2H2O, and Serpentine E: 2MgO·SiO2·1.5H2O. These results show that the present samples are of good quality having the theoretical formulae of magnesium hydrosilicates talc, serpentine, etc. But the samples of serpentine D and E are of a little lower grade cont:ining a little larger amounts of alumina and iron oxide impurities.
(2) By using the talc sample E, several series of tests were systematically carried out. The test pieces were moulded to small plate (Length: 60mm, Bredth: 30mm and Thickness: 5-10mm), by pressing with oil press, applying various pressures 100-700kg/cm2 without water, which was quite different from those moulded with water in the previous reports I-III. The moulded pieces were not necessary to dry and then at once burned at 1300-1500°C for 2-6 hours. The test pieces were strictly compared on varous points, i.c., drying and burning shrinkages, specific gravities, porosities, mechanical strength (bending or transverse strength, or modulus of rupture). The results are shown in the following tables.
It is clearly seen from these results that the physical property of bending strength became greater proportionally to the higher moulding pressure, and the porosity was considerably small in the samples of higher moulding pressures. These results are far better than those of samples moulded with water in the previous papers I-III, owing to the moulding process without water.
(3) As plastising materials, magnesium chloride of 12% water solution and boric oxide in powder were used, and the moulding and testing were quite equally carried out as those above explained. The results are tabulated in the following table 3.
The addition of small amount of magnesium chloride or boric oxide gave good results, e. g., higher bending strength and smaller porosity, especially in the samples moulded by higher pressure 400-700 kcm2. But on the contrary, these plastisers gave bad effects to the products. The test pieces expanded and lowered the strength by storing in the air for three months, esperially the sample MR60-2 moulded by the addition of borax considerablly expanded and disintegrated.
(4) Nextly, free magnesia and silica were mixed in the molecular ratio of natural magnesium hydrosilicate minerals of talc, serpentine, merrschaum, etc., and moulded with or without water. For this purpose, caustic or light burned magnesia and Keisanhakudo (siliceous white earth, natural product in the province of Ishikawa, containing large amount of
