(I) Study on the influence of low temperature annealing upon the mechanical properties of S-H cast iron :
  The conditions of low temperature annealing were as follows :
  Annealing temperature · · · · · · · 350°C, 550°C and 700°C.
  Annealing time · · · · · · · · · · · · · · 1, 3 and 6 hours at each temperature mentioned above.
  Furnace cooling after heating.
  It was confirmed that the matrix structure of S-H cast iron changed entirely to ferrite when it was annealed under the conditions of 3 or 6 hours at 700°C. Under the other annealing conditions, the matrix structure of S-H cast iron showed much more pearlite than ferrite as in the original structure. The longer the annealing time at 700°C, the lower the tensile strength and Brinell hardness. Remarkable influence of the mechanical properties of S-H cast iron was not found when it was annealed for 1, 3 and 6 hours at 350°C and 550°C. The mechanical properties of S-H cast iron, especially the deflection, could not be improved by low temperature annealling against the expectation.
  (II) Study on mass effect of S-H cast iron :
  The test bar with six steps used for the present investigation was 550mm in total length, and the each size of six steps of a test bar was 50×80×100mm, 50×50×100mm, 50×40×100mm, 50×30×100mm, 50×20×100mm and 50×10×50mm respectively.
  Fracture test, microscopic observation on the structure of graphite and matrix and hardness measurement were carried out on the various positions at the center of each step of the test bar.
  it was made clear that the mass effect on the structure and Brinell hardness of S-H cast iron was much lesser than those of the common gray cast iron. It was found that the mechanical properties of the former were superior in uniformity than of the latter.

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  For the production of cast iron with cast-in-steel inserted, the authors made various tests of coating using steel-cores which are electrically plated on the surfaces with copper, chrome and nickel respectively.
  The copper plating is dissolved into the iron as solid solution and a part of the nickel plating is dissolved, but the rest remains unaffected, while, the chrome forms chemical compounds. Compared with iron cast with non-plated cast-in-steel inserted, the former shows a greater degree of soldering and strength, and in this respect, copper and chrome are most effective, especially copper ; while nickel has proved to make the production worse.
  From the above results, it may be inferred that cast iron inserted with cast-in-steel plated with copper is desirable, even the odded treatment and higher cost are taken into consideration.

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  The author has studied the impulsive heating of molding sand, the temperature in the molding sand, and has found out the following matters to dicrease the molding sand defects at elevated temperatures.
  1. Molding sand defect at the elevated temperature is caused originates by the partial heating of the molding sand and the steam pressure originated in the molding sand.
  2. By mixing silica flour over 20 persents into 40 mesh molding sand, heat conductivity decreases, and partial heating increases.
  3. Graphite, oil or wood flour additions decrease the defect of sand at the elevated temperatures.
  4. The more the moist percent, the more the heating rate of molding sand, and the more the permeability at the dried molding sand, the more heating rate of molding sand. The rate of heating of the graphite mix melding sand is fast.

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  To determine the grain shape of silica sand, W. Davies and W. J. Rees have established the method of air permeability and J. Kashima has also built up the method by means of a centrifuge. These are truely very precise methods to the determination of sand grain shape, but there leave some difficulties to apply the methods in foundry practices. Therefore, the authors worked out a new method of determining sand grain shape by using a permeability meter.
  The apparatus and attachment are illustrated in Fig. 1.
  The results of the determination are as follows :
  1) The method by means of permeability meter seems satisfactory in the points of precision and easiness of the determination.
  The coefficient of angularity of a glass ball used for day-light screen (20∼200 mesh) is 1.02 and the problable error is ±0.01.
  2) The coefficients of angularity of the silica sands yielded in Seto, Tokitsu and Mikawa were almost the same values with Isono's experiment.

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