The shrinkage of Al-Zn and Al-Sn alloys during unidirectional cooling was studied by continuous measuring the change of length and temperature of the top of specimens from 850°C to room temperature. The results obtained were:
  1) The amount of shrinkage decreased with increasing the contents of alloying elements.
  2) The total amount of shrinkage in that temperature range was mostly dependent upon the amount of solidification shrinkage.
  3) In the case of aluminum alloys having zinc of 15 and 20% there occurred shrinkage of two steps during solidification. This appeared to be due to the movement of partially solidififying region.
  4) As compared with this, aluminum alloys containing tin of 1 to 10% did not show such shrinkage of two steps.

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  In the present work copper and copper alloys were solidified within a cylindrical die under high hydrostatic pressure of 1,000 to 6,000 kg/cm². When pressure was applied to molten metal at a temperature extensively higher than its melting point, columnar crystals developed from the surface of the die toward the center. When the temperature of the molten metal at which the pressure was applied was lower, there grew equiaxial crystalline structure in the center of the cylindrical casting, and the central zone of equiaxial crystalline structure had a tendency to be increased with increasing pressure. When pressure was maintained constant, with lowering the temperature at which pressure being applied to metal the equiaxial zone grew larger and the size of crystals became finer. This may be due to the fact that undercooling was favoured by rise of melting point, rapid cooling and abnormal condensation of solute element under high pressure. The latter effect of pressure was significant in case of copper alloys having wider freezing range such as Cu-Sn and Cu-Pb alloys. Particularly under higher pressure preferentially linear growth of dendrite arms was promoted. This resulted in refining dendrite cells and producing dispersion of fine and flat secondary phases in the cell spacings.

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  Generally self hardening moulding processes consist of adding sodium silicate (having a molecular ratio of 2.3 to 3.3 and a specific gravity of 1.4 to 1.6) to silica sand.
  The hardening reaction starts with the hydrolysis of the sodium silicate, giving sodium hydroxide (NaOH) and hydrated silica (H₂SiO₃), because of the various chemical reactions, the hydrated silica is gradually dehydrated, but does not dissociate.
  In this investigation, bentonite is used as an additive to sodium silicate, and the relationship of the chemical reactivity of bentonite and the hardening reaction of the sodium silicate is reported. The change in composition of the sodium silicate soaked bentonite was chemically analysed and the swelling capacity, viscosity, pH value, base exchange capacity, and others were measured.
  The conclusions are as follows:
  1) The viscosity or plasticity of the bentonite reaches a maximum value as a certain water content. Depending upon the variety of bentonite used, the increase in viscosity and pH drop is dependant upon the type and amount of solvent used, i.e. water, sodium silicate, sodium hydroxide solution.
  (a) Consequently, the viscosity is greater using sodium silicate than when using water or sodium hydroxide, and bentonite with a higher water absorption factor, gives a higher viscosity in a muddy suspension when mixed with sodium silicate, but after some time, the viscosity becomes constant.
  (b) This phenomena seems to indicate that the stronger the water absorption property of the bentonite particles, the greater the amount of OH^- ions and H₂O are taken from the sodium silicate. This can be illustrated, because when the water absorption is maximum, the viscosity reaches maximum and the pH value is lowest and stops falling.
  2) The chemical reaction between bentonite and sodium silicate may be explained as follows:
  (a) Bentonite has a very strong base exchange property in an electrolyte such as sodium silicate, compared with other minerals such as kaolinite. This reaction starts with the hydrolysis of the sodium silicate.
      Na₂O•nSiO₂+H₂O=2NaOH+nSiO₂
  That is:
      Na₂SiO₃⇌2Na⁺+SiO??^-
                          +      +
      2H₂O⇌    2OH^-+2H⁺
                          ⇃↾    ⇃↾
                   2NaOH+H₂SiO₃
  Since the chemical equation supposes that the Ca²⁺ ions existing in the bentonite particles are substituted by Na⁺ ions in the sodium silicate through absorbing OH^- ions.
  (b) The facts are understood, because the bentonite soaked in sodium silicate, decreases the H₂O and Na₂O content of the solution. It can be shown that the hardening reaction depends upon the hadrolysis of the sodium silicate, and the presence of high absorption value bentonite, accelerates the hydrolysis of the sodium silicate.

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  Using two kinds of coated metal molds preheated at about 150°C which had a form to restrict the contraction of castings, the tendency to hot tear formation of cast iron with varying composition was studied. Iron was melted in a high frequency induction furnace with alumina crucible at about 1,400°C and poured at about 1,300°C. The results obtained were as follows :
  (1) Free contraction was responsible for hot tear formation and chilling increased free contraction and promoted hot tearing.
  (2) Cast iron of lower Sc had more risk of hot tear formation.
  (3) The influence of various elements on hot tearing was :
      Si : Considerbly decreased hot tearing.
    Mn : Excessive Mn addition promoted both chilling and hot tearing.
      P : Promoted hot tear up to P 0.4%. Hot tear Remarkably decreased at P 0.6% but increased again above P 0.6%.
      S : Considerably promoted hot tearing.
    Cu : Contraction and hot tear formation tendency were slightly increased if Cu% was higher than 2.0.
    Sn : Promote both chilling and hot tearing if Sn content was above 0.2%.
  (4) Thick coating was effective not only on reducing cooling rate but on decreasing hot tear.
  (5) Inoculation was effective to reduce hot tear formation in low Sc iron castings.
  (6) It is considered that the temperature of hot tear formation is near to the solidus but the tearing temperature may be changed by chemical composition. When eutectic graphite structure is formed, hot tearing time is considerably late. When white iron structure is formed, hot tears form at comparatively high temperature.
  (7) It is effective to strip mold at early period to prevent hot tearing. In order to completely prevent hot tearing, it is necessary that the mold is stripped prior to finishing the eutectic solidification at the portion where tears tend to occur.

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  Considerable amounts of steel scrap are often charged into cupola together with pig iron and return scrap. Since steel has a higher melting point than the other materials, the charging manner of steel scrap, that is, the relative position of steel scrap and the other materials in a charged metal layer, would affect the cupola melting process. The following experiments have been performed to clarify this situation.
  A cupola of 400mm in int. dia. having about 800 kg/h of melting rate was used.
  With a charging ratio of pig iron : return scrap : steel scrap=3 : 4 : 3, six different kinds ot operations were performed changing the weight of a batch to 50, 80 and 120 kgs and the position of steel to the upper or lower part in each batch.
  Each operation was made at a coke ratio of 18% and a blast rate of 100 Nm³/mn-m². A steady state was established about 40 minutes after melting began to take place and subsequently experimental data were taken for about one hour.
  Samples for chemical analysis were taken from molten iron flowing through the front slagging spout every one minute to check the fluctuation of chemical compositions. Besides, the temperature of molten iron were measured continuously at the base of spout. Moreover, γ-ray intensity penetrated through the furnace at the level of 570mm above tuyeres was recorded continuously to catch the melting manner of the charged metals.
  As the results of operations of such different charging manners it was observed that the fluctuation of carbon content was large when steel was put into the upper part of the metal charge and the weight of one batch increased. On the other hand a higher temperature of molten iron was obtained in this case. The difference of temperatures was about 20°C.
  These results may be analysed by Fig.1. When steel is set at the upper part, cast iron occupying the lower part would melt down at a higher level due to a rapid heat absorption from bed coke and steel would melt down later seperately from cast iron. This melting manner would result in the large fluctuation of carbon content. The higher iron temperature would be brought from the temperature gradients of both materials as shown in the figure (A). Point T shows mean tapping temperare.
  On the contrary, when steel is put into the lower part of the charge, cast iron at the upper part would not be able to melt rapidly and both materials would melt down simultaneously at a lower level. The simultaneous meltng would result in small fluctuation of carbon content. The lower iron temperature in this case would also be proved by the figure (B).
  The melting-down levels of cast iron in both cases were caught by γ-rays.
  As the results of the exeriments the opposite effects were obtained on iron temperatures and the fluctuation of iron composition in the two charging manners. Since iron tomperature is an important factor concerning the quality of cast iron, the manner of putting steel into the upper part of metal layer is preferable and the fluctuation occuring in this case should be decreased by adopting a small batch weight or any other methods.

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