The erosive condition of acidic fire bricks for a cupola was tested by changing the concentration of silica in them.
  In the case of consideration of only the chemical composition of acidic fire brick, as the result, was it clalified that the higher the concentration of silica is, which offers larger viscosity at high temperatures and better bloating property, the better the result is. It became apparant, in this respect, that the Roseki brick (Pyrophyllite base) of Japan is extremely excellent as the acidic fire bricks.

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  The dolomite refractory brick, highly resistive to spalling and also to errosion by slag, was used in the melting zone of cupola.
  The dolomite refractory brick is an unburned brick having the chemical composition of 12∼13% SiO₂, 9∼11% Fe₂O₃, 40∼42% CaO, 30∼32% MgO and the refractorieness of SK37 and 22.3% Porosity.
  The first test
  The dolomite refractory brick was heated at the temperatures between 1450°∼1500°C for about 8 hours for test. The surface of the brick was somewhat melted and the thickness of the brick was decreased by 30∼40mm., but any spalling tendency was not observed.
  The second test
  The brick was heated at the temperatures between 1450∼1500°C for one hour, and then cooled to room temperature, and again the brick was heated at the temperatures between 1450∼1500°C for one hour and cooled again to room temperature, thus the brick was tested four times in the same way, No spalling tendency was observed substantially, and the resistance for errosion was much better than that of the slag contains less Fe₂O₃ and more MgO compared with the ordinary one, and the melted iron was thus obtained by using the conventional brick.

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  The composition and properties of the patching material made in the U.S.A., was investigated.
  The results are as follows;
  (1) Refractorieness SK26;
  chemical composition; SiO₂ 85.50∼87.89% Al₂O₃ 7.71∼8.04%, Fe₂O₃ 0.63∼0.93%.
  (2) The distribution of the sizes of the grains is composed of about 45% of coarse grain (1,000μ up), about 20% of middle grain (1000∼149μ), and about 35% of fine grain (under 149μ)
  These grains were tested by chemical analysis, polarized microscope and X-ray diffraction pattern, and it was found that the coarse grain and middle size grain are quartz and fine grain consists of quartz and clay substance, which has a tendency of expansion when heated.
  (3) The patching material was heated at SK10 (1300°C) for one hour, the resulted material was compared with the raw material as in the following table.
  [Written in non-displayable characters.]
  (4) The Compresive strengths after aging are as follows:
  [Written in non-displayable characters.]

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  Author examined the properties of Daubpax, a material for cupola lining repairs, and used it in the practical operations.
  The following results have been obtained.
  (1) Daubpax is a mixture of natural silica and artificial silica of high grade, and consists of coarse grains retained on the 10 mesh sieve and fines passed through the 100 mesh sieve.
  (2) The green compressive strength is best in case of 6 to 8% moisture added.
  (3) Highest resistance to erosion has been obtained in case of 4 to 6 day's tempering, and the eroded volume is less than that of the pyrophyllite bricks, we have used.
  (4) As the material of cupola lining repairs, Daubpax has shown the equal or better results in comparison with the pyrophyllite bricks.
  (5) Comparing the cost of cupola lining repairs between the two, Daubpax is more expensive by reason of imported goods, but it can save the work time to repair.

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  There have been ardent requirements for reducing troubles of bricklaying and repairing of cupola linings. New type of patching material was made of coarse Quarzite grain and fine Pyrophyllite grain. Reduction of ¹⁄₃ of labour and time and good results were obtained by practical use. Specimens of used patching material were tested by microscope, Spectral analysis and X-ray diffraction patterns.

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