A maximum stress of the O type cast iron test pieces is given as
    σ₁1=δEI₂/AR³{(π/4)−(2/π)}
    |σ₂|=δEA/2πR²{(π/4)−(2/π)}
    σ₁ : max. stress of arm, |σ₂| : max. stress of ring
    δ : deflection, E : Young's modulus
    A : sectional area of center bar
    R : radius of ring
    I₂ : sectional modulus.
  (1) The difference of the sizes of the center bar and ring gives the different cooling velocity, and which is the most important factor of casting stress.
  (2) Hardness of green sand mold gives a small effect.
  (3) Transition temperature from elastic zone to plastic is about 600°C.

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  The mould or the core in contact with molten steel usually changes its volume because of the expansion of sand grains, and they collapses after the bond is destroyed by heat. The effect of wood flour added to sands on steel casting was studied.
    The results are summarized as follows :
  1) The wet strength of the moulding sand is reduced by the addition of wood flour, therefore its content should be limited below 3 per cent.
  2) The dry strength of the moulding sand depends upon the drying temperature and drying period.
  3) It is observed that 2 per cent of the added materials gives good results.
  4) The expansion of the moulding sand at a high temperature is decreased notably when 2 per cent of wood flour is added.
  5) These results have been successfully applied in the foundry shop practice.

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  The author has announced the method to express the semblance of a sand grain by a numerical figure in the “IMONO” (Sept. 1954).
  Applying this method to the various kinds of sands used in foundries, the semblance of those sands were measured and the relation between the grain size index and permeability of a certain sand was investigated this time.
  The permeability of a sand mold, in general, is influenced greatly by the grain size of the sand, the additional amount of binder and the degree of ramming. Therefore, the permeability of various kinds of sands were measured respectively by keeping the degree of ramming and the grain size of the said sand constant.
  According to the test result of this study, it has been ascertained that the influence of the semblance of sand grain is extremely small in the limits of the additional amount of binder commonly used in the foundries ; i. e. 4 to 8 per cent. As the amount of binder added to the sand becomes smaller than this limit and reaches to almost zero, the grain size index of each sand having identical grain size can be determined by comparing the permeability value of each sand.

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