The addition of 0.3∼0.6% Mn to 3.2% C-5.5% Si grid iron melt lowers both the specific electric resistance and the hardness, while it raises the deflection amount and transverse strength at the bending test. The phenomenon can be explained as follows : MnO produced from the addition of manganese acts on suspended particles of 2 FeO₂ · Sio₂ or other silicates in molten iron, lowers the melting point of such non-metallic inclusions and promotes their growth, resulting easy separation of these inclusions from molten iron and prevention of the appearance of the normal flaky graphite in cast iron. The elimination of such reaction products promotes to make the reaction of FeO+Mn=MnO+Fe proceeding to the right side, resulting good deoxidation by adding small amount of manganese. This fact brings the appearance of the eutectic graphite structure in iron by the aid of the elimination of silicates which cause the growth of the graphite. Excess manganese besides that used for deoxidation and the killing alloys in iron and erases the eutectic graphite.
  Increase of silicon from 1% to 4% in 3% C-15% Ni-iron enhances the electric resistance and lessens its temperature coefficient, while the hardness is hardly influenced thereby. The reason why the electric resistance is greatly increased by the Si-addition depends mainly on the increase of the amount of the graphite and its large flaky form due to the Si-addition. By 0.5% Mn-addition the high-Ni, high-Si castings become tough and strong, and its electrical resistance is decreased, which is caused by the less amount of the graphite separated from the melt and the suppression of the growth of the graphite. Moreover, the addition of 0.5% Mn makes the amount of martensite maximum in the range of 0∼2% Mn-addition.

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  Here is reported the fundamental research on the production of the acid-resisting pipe by the centrifugal casting process, which consists of grey cast iron in the outside and high silicon cast iron in the inside in order to strengthen the brittleness of high silicon cast iron, to improve machinability of the outside, and to save expensive material.
  The results obtained are as follows :
 1. The boundary between high silicon and common cast iron had better to be as narrow as possible and to be clearly separated into two layers because corrosion-resisting property is injured by the movement of much amount of carbon into the high silicon part.
 2. The more beutiful casting surface of the inside high silicon cast iron was obtained by the higher casting temperature.
 3. If the temperature of grey cast iron is too low or its oxidation is severe when high silicon cast iron is cast, shrinkage cavities occur in the boundary.
 4. In this experiment, the dual metal of the pipe 150 mm in diameter, 40 mm in width and 10∼20 mm in thickness was produced at the temperature of grey iron 1200°C, when high silicon cast iron was cast at 1300°C. It obtained the bending 6.5 mm with the load 4700 kg. (M. I.)

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  Spheroidal graphite cast iron in inclined to have shrinkages and difficult to obtain the sound casting. In order to study the cause of such shrinkage which can't be seen on common gray cast iron, we take the wedge type test piece. The results obtained gray cast iron, we take the wedge type test piece. The results obtained are as follows ;
  1. The more the Mg addition, the more the shrinkage.
  2. The more the residual Mg, the more the shrinkage.
  3. The more the inoculant Si, the less the shrinkage.
  4. The influence of Mg for the shrinkage is greater than that of Si.

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  In view of "surface tension theory", we theoretically studied the variatiese upon the green strength of molding sand owing to fineness of sand grain, content of moisture and rate of ramming, with the experimental result and then discussed "surface tension theory" again.
  As its result there scarcely exists the difference between the value of caluculation by theoretical consideration and that of the experiment.
  This result shows well qualitatively and quantitatively that bonding power of molding sand owes it to surface tension of water. (T. Okakura)

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  When the inside of the cylinder liner for the diesel engine 1 to 1.5 mm is hardened by the induction hardening of the 200KVA spark gap type, its inner diameter shrinks a little and its tendency becomes the shape of a Japanese hand drum for the longitudinal direction.
  The outer diameter shrinks with it. The degree is different with the size of the liner, that is, the maximum deformation is 0.17 mm for the liner 4(1" / 4)×10(21" / 32) and 0.27 mm for 5(3" / 4)×15.02".
  When cast iron is hardened, the tensile strength is lowered but restored by the tempering. The tempering temperature which the hardness is not injured and the tensile strength is considerably restored is about 300°C.
  The graphite of cast iron becomes larger by the hardening. This will be caused by decomposition of cementite at the heating. (M. I.)

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