This study examined the influence of silicon content, addition of nickel, and inoculation on the impact properties of annealed spheroidal graphite cast iron with a ferritic structure at a constant C. E. value (C. E. =C+1/3Si=4.3) ; an analysis of impact fracturing behaviour and microfractography on the fractured specimens have been performed.
  When the C. E. value is the same, the transition temperature increases considerably as the silicon content increases but the shelf energy absorbed in the ductile range does not change so much by the silicon content. The transition temperature, maximum fracture load and lower yield load all increase by the addition of nickel. By adding ferrosilicon for inoculation, the transition temperature decreases. This is attributed mainly to the increase in the number of graphite particles which act as a barrier to the propagation of brittle cracks. From the result of microfractography, the decohesive fracture pattern at twin-matrix interface was found to incline to appear frequently in the brittle fracture of higher silicon content cast iron.

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  A numerical calculation method-Matrix Method-is proposed for the calculation of solidification of castings of complicated-shapes and examples of two calculations are shown.
  This method was arrived at by extending the Dusinberre's Triangular Network Method and applying the Finite Element Method (FEM). The proposed method is essentially equivalent to FEM and the conventional Finite Difference Method (FDM) and has the following advantages. (1) The physical significance of the Matrix Method is clearer than that of FEM. (2) Various elements, such as 3 and 6 nodes triangular elements, triangular ring elements, rectangular parallel-piped elements and so on, can be used more easily than in FEM. (3) It is more easily applicable to solidification problems with boundary conditions more complicated than FDM.

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  The effect of riser and chill arrangement on the soundness of sand-cast HK-40 steel (0.4%C-25%Cr-20%Ni) was studied experimentally. It was found that the size of risers should be about two times as large as that recommended by Pellini for plain carbon steel and that the end cooling distance and riser feeding distance were approximately equal to those found by Pellini on plain carbon steel.
  The effect of several foundry variables on the mechanical strength of steel at room temperature as well as at an elevated temperature was studied experimentally. It was found that strength decreased with an increase in section thickness and that the major cause for the decrease was a micro-constituent which precipitated during slow cooling after solidification, and not the casting defects nor crystal grain size. It was shown that much of the decrease of strength in heavy sections could be prevented by rapid cooling after solidification.

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  Low alloyed wear resistant cast steel usually gives high wear resistance by introducing extremely hard martensite, so tempering treatment after quenching should be carried out at temperatures as low as possible. This makes it difficult to have cast steel sufficiently toughened. The authors made some investigations on the effects of Si, Cu and Ni additions to martensitic type Si-Mn-Cr steel, as well as heat treatments, on their mechanical properties and attempted to improve toughness by making the low tempering temperature embrittlement occur at temperatures as high as possible.
  Addition of 1.0%Si to Si-Mn-Cr cast steel causes the low tempering temperature embrittlement to appear at higher temperatures and consequently the toughness of the steel tempered at relatively low temperatures is improved. The combined addition of 1.0%Si and 1.8%Cu diminishes decrease in hardness resulting from tempering by Cu precipitation, whereas the improvement in toughness lowers correspondingly compared to 1.0%Si single addition. The toughness of steel containing Si and Cu improves even more by another addition of 1.8%Ni. It became clear that on the whole bainitic structure by Ni addition is better than tempered martensitic structure in terms of hardness and impact value.

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  Pressure variations in molds and mold cavities of vacuum sealed molds were measured, and the influence of the vent between the mold cavity and atmosphere and the mold coating on them were investigated. Experiments were carried out on molds for plate-shaped castings having dimensions of 400mm×200mm and thickness of either 60mm or 20mm.
  Pressure in the mold and the mold cavity severely varies during pouring. By melting the film covering on the mold surface at pouring, the air in the mold cavity is exhausted through the mold sand. At that time, pressure in the mold cavity decreases while the pressure in the mold increases, so that the pressure difference between the mold and the mold cavity becomes small, and the mold strength is thereby lowered. When a vent of adequate size is provided in the mold, pressure drop in the mold cavity can be prevented and the pressure can be held at about atmospheric pressure. Usually, the strength of the drag mold is more stable than that of cope mold, because the pressure increases considerably less in the drag mold than in the cope mold. The above described pressure variations can be reduced by the mold coating which decreases permeability at the mold surface.

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  It has been shown in authors' previous studies that the dendritic structure of Al-solid solution in Zn-Al binary alloys may be refined considerably by adding small amounts of Zr, Ti, Mn or Ni. Tests were carried out to investigate in detail the effect of those elements on dendritic structure.
  By Zr addition, nodular-like structures were observed in alloys of 0.05-0.28%Zr addition which grew slowly with the increase in the temperature drop. Dendrite arm lengths in every composition increased rapidly in the initial stages of freezing. Secondary arm cell size and arm spacing increased gradually as the temperature drop increased and the growth rate of dendrite cell in alloys of 0.28%Zr addition was greater than those of other composition alloys.
  In case of Ti addtion, petaloid-like dendritic structures were observed in alloys of 0.05-0.5% Ti addition. The growth of dendrite, and changes of arm length, cell size and arm spacing were nearly the same as Zr addition alloys. The growth of dendrite in 0.25% Tialloy was less than that of other composition alloys. With regard to Mn addition, the dendrite shape factors were nearly the same as Zr and Ti addition alloys.
  In case of Ni addition, the growth of the primary dendrite was disturbed by increasing the amount of addition. The secondary dendrite arm length increased rapidly until the temperature drop of approximately 30°C. Secondary arm cell size and arm spacing increased gradually as the temperature drop increased and the dendrite arm lengths grew especially remarkably in 1.0%Ni alloys.
  The Zr and Al concentrations of dendrite in the freezing range of Zr addition alloy which remarkably refines dendritic structures were measured. It was recognized that Zr was slightly enriched at the circumference of the secondary arm cells in 0.1%Zr alloy was greater than that of 1.0%Zr alloy.

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