A summary of the investigation on improvement of the yield of casting.
  To improve the yield of casting, following factor will be considered:
  the loss due to the riser, the loss due to the gating system and the loss due to the inferiority of the products.
  Among them, the loss due to the riser is the greatest, and by minimizing this loss, the yield rate of the casting will be elevated to above 80%.
  Of course, such effort should not cause the wrong effect to the economical conditions.
  In many case the shape of the raise is cylindrical, and its diameter is equal to its height.
  In this case, the time required for solidification of the metal is given by;
   [Written in non-displayable characters.] ⋅⋅⋅⋅⋅⋅⋅⋅ (6)
where,
  t_s : the time required from the pouring, to the beginning of the solidification,
  t_c : the time required from the beginning to the end of the solidification,
  γ : specific gravity of the molten metal,
  c : heat capacity of the molten metal,
  q : latent heat of solidification of the metal,
  θ₀ : the pouring temperature of the molten metal,
  Ⓗ : solidificating temperature of the metal,
      X=V⁄(S)=Volume of the feeder head⁄(Surface area of the riser)
  B : heat diffusion rate of the mold.
  The term X²/B² is only concerned with the mold, and the term inside of { } is only concerned with the characteristics of the molten metal.
  Now, consider two cases using different material for the mold of the raise: the one, using ordinary casting sand, shown by the symbol Rf, the other, using the heat insulating matarial, such as ceramics.
  In these two cases, if the same condition of the molten metal is adopted, the terms inside of { } are the same, then from the eq. (6),
  Rf solidification time : Rd solidification time
      =X_f²⁄(B_f²) : X_d²⁄(B_d²)
  If the time required for solidification in these case are the same,
      X_f⁄(B_f)=X_d⁄(B_d) ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ (9)
  And if the shapes of the raises are similar each other, consequently X=V⁄(S) ∝d, then eq. (9) becomes;
      B_d⁄(B_f)=d_d⁄(d_f) ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ (10)
  Jf B_d⁄B_f=x, then d_f/d_f=x, consequently
      Volume R_d⁄(Volume R_f)=x³
  For example, if B_d⁄B_f=X=½, the equation above becomes 1/8.
  This fact induces following conclusion;
  “A heat insulating material is essentially effective for the mold.”
  The formulae of B is expressed;
      B=√γ•C•λ
  λ : heat conductivity of the mold material.
  To decrease the value B, a material having low value of γ must be chosen.
  Considering economically, we chose the material No.083 for the mold of raise.
  The practical datas using this material were well brought in line with the theory above mentioned.

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It is Common knowlege that, put silicate Calcium Salt (2CaO. SiO₂) into Soduim Silicate water solution, it congeals as time Passes, and gradually harden as increase mechanically intensity.
  CaO-SiO₂ groupo lie kind of 4 Silicate salt compound, in the and these produce CaO•SiO₂•nH₂O and Ca(oH)₂ by hydration.
  Hydraulic properties arise in reaction of hydration of component compound, and the most notable of them is 3CaO•SiO₂, and 2CaO•SiO₂ is weak as to hydraulic properties.
  Reaction mechanism of 2CaO•SiO₂ and Sodium silicate that is meak of hydraulic properties is very complrxity, it is impossibility to briefly make clear.
  Next hardened mechanism supply a few consideration writer's experiment data and quotation of records.
  Show result of examination as follaws.
  Presumption of hardened mechanism
    Na₂SiO₃+2H₂O⇌2NaoH+H₂SiO₃ —①
              2Ca₂SiO₄→2CaO+2CaSiO₃ —②
        CaO+H₂SiO₃→CaSiO₃+H₂O     —③
            CaO+H₂O⇌Ca(oH)₂              —④ (①+②+③+④
  ————————————————————
Na₂SiO₃+2Ca₂SiO₃+2H₂O→2NaoH+3CaSiO₃+Ca(oH)₂
  After sodium silicate dissolves in water, raise hydrolysis and turn out NaoH and H₂SiO₃. Because of H₂SiO₃ is weak acide, the degree of elecrolytic dissosiation is very small. The other side NaoH is strong base and degree of electrolytic dissosiation large, So it produce a great deal of oH^-, prove strong alkali Solution. 2CaO•SiO₂ is Orthosilicate Salt and it’s molecule union is stable in air, but has character to change to Stable Metasilicate Salt under the Some stimulus.
  Therefore it seems that being of strong alkali or silica is conditions of dissociation and it quiken dissosiation of 2CaO•SiO₂ but NaoH of Strong alkali is a changeless catalyst process. Also H₂SiO₃ act upon Separated CaO, expend CaO and more promote dissociation.
  This is a reason that hardened speed of 2CaO•SiO₂ in NaoH individual Solution is slawnes but it is proved to speedily harden in soduim silisate. And also namely CaO react upon H₂O and produce Ca(oH)₂.
  It seems that this influenced by silica and quantity of humidity. And hydrolysis reaction of sodium silicate is done secondary way as follows.
    Na₂SiO₃+H₂O→NaoH+NaHSiO₃
    NaHSiO₃+H₂
  In sodium silicate as this is being sodium silicate hydrogen. It causes reaction of next formula but does not show large action.
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  Author has investigated the pyrolytic characteristics of cabonaceous materials for molding sand by means of thermobalance.
  The pyrolysis of carbonaceous materials varied with the characteristics and the structures of their own, and it was remarkably affected by the conditions of carbonization process. Especially, the atomosphere was the largest factor of all conditions.
  In pyrolysis, resins was easily depelymerized, in general, at lower temperature. Coaldust and pitch took place the decomposition and distillation, of whose chief reaction was evaporation of the some relatively low moleculor organic matter contained in it.
  Under the same heat-treatment conditions, among carbonaceous materials, coal-pitches have a tendency to show the smallest of pyrolytic rate, and also this tendency will be able to be explained from the results of residual carbon, combustion rate, weight and activation energy of pyrolysis etc.

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  In respect of spheroidal graphite cast iron with bull’s eye and ferrite matrix, their dry sliding wear mechanism were investigated.
  The result was found that wear characteristic curves of each cast iron are similar to flake graphite cast iron.
  On spheroidal graphite cast iron, however, at 3.00-4.00m/s of sliding velocity were formed hard layer which seems martensite with approx. 0.02mm thick on sliding surface.
  And ferrite cast iron within both oxiditive wear limit and stable wear limit is on the side of higher pressure and velocity than bull’s eye cast iron.
  But in the result of experiment under wear condition to be fit for stable wear limit, wear loss is about 1.5-2.0 times as bull's eye cast iron in case of ferrite cast iron.
  Wear have been continuously increased until 10,000 meters of sliding length under applied condition in the mild wear range.
  And only γ-Fe₂O₃ was found in the initial stage of wear in the result. In increasing of sliding length gradually, γ-Fe₂O₃ change into α-Fe₂O₃ and there become to be α-Fe together with some of them.

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  This self-hardening mould basically consists of silica sand plus two to three per cent. of specific calcium silicate powders and from five to seven per cent. of sodium silicate aqueous solutions (having a molecular ratio of 2.3 to 3.3, and specific gravity of 1.6 to 1.4).
  The hardening reaction starts when the calciun silicate comes into contact with the sodium silicate solution, i.e., to begin with, the calcium oxide (CaO) isolates from the dicalcium silicate (Ca₂SiO₄), and these compounds of calcjum form insoluble hydraulic of calcium silicate and silica gel by reacting with silica sol (H₂SiO₃) or sodium hydroxide (NaOH).
  Therefore, the free water gradually decreases owing to evapolated reaction. The combined water still remaining, the silica sand combines one another.
  In this report, the properties of several bentonites were investigated by means of various efficiency tests, and the relations between the adsorbed moisture value, swelled capacity or chemical composition of each bentonite, and the effect of the hardening reaction were sought.
  The results may be summarized as follow;
  (1) When the bentonite is used as mould additives, it increses the green compressive strength, the hardening rate becomes more rapid, and decreases the hardening strength.
  (a) Bentonites of higher adsorbed moisture value give higher green compressive strength, but after 24 hours (after completive hardenimg reaction) dry compressive strength begins to drop sharply at four per cent. bentonites, and residual water is certainly produced a little more by the addition of bentonite than by nothing.
  (b) However, when the bentonites of high swelled capacity in the mixture, the strength after hardening reverses its trend and the strength is drops slowly. Of course the residual water is little.
  It may be said that these phenomena indicate that higher adsorbed moisture value of bentonites gives stronger adsorption of free water included sodium silicate aqueous solution. Moreover, the moisture in bentonite can't be easily discharged. It is as a result, supposed that residual water increases and hardening strength decreases.
  (2) When the bentonite mixed with the sodium silicate solution, its viscosity increase through the adsorption of H₂O and OH^- ions.
  Consequently, when the bentonite is used as sodium silicate additives, it raises the density of colloidul silica in the sodium silicate solution, and the hardening reaction becomes rapid.

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