The refractoriness is one of the essential properties of the moulding sand in steel castings.
  It is supposed that the refractory skin of the mould is necessary to get better surface in the casting.
  In the present investigation, it was found that this skin of the mould was within 1-2mm in the small steel casting of about 30mm thickness.
  So it was found that the small steel casting could be produced by floor sand or river sand mould coated with high refractory materials.
  Then, this idea will be developed to thicker castings by investigating the refractoriness and coating method.

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  The wear resitivities and properties of wear surfaces of various cast irons having different graphite have been studied in the case of dry abrasion. In this investigation, the lower specimens are semi-nodular graphite irons of spheroidal and quasi-flake graphites. The upper mated specimens are of various cast irons of different graphite forms, and the wearing test has been carried out till the maximum running distance of 160 km. The results obtained can be summe rized as follows :
  (1) The amounts of wear are influenced by the combination of both materials. In this investigation, spheroidal and semi-nodular graphite cast irons have the best wear resistivity, flake graphite cast irons have the medium, and eutectic graphite cast irons show the lowest one. The specimens having a few grow roughness reveal a stable wear resistivty.
  (2) The roughness of wear surface reveals different curves according to the contact materials, but if the running distance of wearing test increases, the roughness curves of each combined materials approach to a similar one.
  (3) The hardness of wear surface increases with running distance, and gradually tends to a constant value. Some minor differences are also observed in the change of hardness for various contact materials.

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  Recently, various deoxidizers were added to molten cast irons to improve mechanical properties. The present writer had studied on the improvement of fluid life of molten Al alloys at high temperature by dressing the alkali metal salts on the mold surface. Lately he found that, these salts are effective to improved the mechanical properties of cast irons when added to molten metal. Of these salts, k₂CO₃ gave the best results and a few more experiments were done on the line. Then CaH₂ were added to molten cast irons and investigated. The results obtained were as follows :
  (1) The eutectic cells were refined and the tensile strengths and elongations were improved by using these salts.
  (2) Eutectic cell sized were approximately proportional to tensile strengths when alkali metal salts were used.
  (3) Solidification temperatures of primary dendrites and eutectic varied by using alkali metal salts observed in the cooling curves.
  (4) In the cast when K₂CO₃ was used :
    A. Increase the carbon equivalent decreases the tensile strength.
    B. The maximum tensile strength was obtained when 0.5∼0.67% K₂CO₃ was added, the sizes of eutectic cells were least at this time.
  (5) The size of eutectic cell was smallest in the case of 4.06 of C. E. whether K₂CO₃ was added or not.
  (6) CaH₂ refined the eutectic cells and increased the tensile strengths, but if Fe₂O₃ was added beforehand to the melt, it refined the cells more.

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  Moulding sand which was the mixture of silica sand, Ca-Si powder and sodiumsilicate was prepared and thermal expansion, high temperature strength, residnal strength after cooling, and gas quantities evolved at high temperature were examined on it. The results obtained were as follows :
  Thermal expansion is maximum at about 670-700°C.
  High temperature strength is maximum at about 600°C, and at higher temperature falls again to lower value.
  Strength after cooling rapidly fulls to low value heating from room temperature up to about 200°C, and no more remarkable change occurred heating up to 1000°C.

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  Since aluminum bronze has good mechanical and incorrodible properties and has low density, it has recently been used as propellers or propeller shaft sleeves of high speed big ships. This report covers the manufacturing method and the various properties of large sized aluminium bronze castings manufactured by centrifugal method were discussed in the following conditions.
  (1) Chemical composition; 8.5∼10.5 Al-3.5∼5.0 Fe-1.0∼4.5 Ni-0.5∼1.0 Mn-bal Cu
  (2) Melting; Oil fired air furnace, double melting, 4 heats.
  (3) Casting; horizontal centrifugal casting machine.
  (4) Casting weight; 3∼6.5 tons. O. D. 500∼720 mm I. D. 400∼600 mm L. 5300∼6500 mm
  (5) Various properties; Tensile test, Hardness test, Fracture test, Macro structure test, Micro structure test, Chemical segregation test, pressure tightness test, other general physical properties.
  It was found that in the production of aluminium bronze sleeves by centrifugal casting, extremely sound castings can be obtained by controling melting and casting techniques.

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