The electric current direct heating technique enables the production of ADI at a reduced processing time. In this study, in order to apply this method for ferrite matrix ductile cast iron in which carbon does not diffuse sufficiently into austenite under short heating, the effect of contained graphite characteristics on quick austempering process was examined. Microstructures of ADI obtained through the above technique strongly depend upon the characteristics of spheroidal graphite in supplied ductile iron. The banite structure domain expands as the size of each graphite decrease and its count increases even when the graphite area fraction is the same. It is clear that quick austempering based on direct electric current supply is applicable for ferrite structure ductile cast iron by controlling the graphite size. Consequently, an ADI with excellent mechanical properties can be produced successfully even from ferrite based ductile cast iron by quick austempering.

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  In the supply of green sand to the metal flask, aeration which introduces low pressure compressed air not only from the top of the sand tank but from the side as well is performed. Because the aeration reduces friction resistance acting on the taper of the sand tank and air pressure is low, the green sand in the sand tank is not compacted. In this study, filling experiments by aeration were conducted to compare free falling and blowing to the flask. The experiments clarified that aeration is effective for filling narrow cavities. The relationship between the aeration pressure and bulk density in narrow cavities was clarified and the condition of the aeration filling was optimized. Computer simulation was also performed using the distinct element method. The mechanism of the aeration filling was clarified from the experiments and analysis.

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  The effects of alloying elements on eutectic temperature was investigated. Most alloying elements have a linear relationship with content and eutectic temperature. But S, Mn and Rare Earth Metal (RE), both of which are sulfide forming elements, have transition points. In this research, the interaction between S and sulfide forming elements was investigated from the viewpoint of eutectic temperature, using a thermal analysis system consisting of three cups.
  The theoretical relation between Mn and S contents at the transition point can be expressed as Mn % = 1.71 S % + 0.4, where the difference between the graphite and cementite eutectic temperatures is maximum. The soluble S amount and soluble Mn amount at the transition points are always 0.023 % and 0.44 %, respectively. When S, RE, Ca and Ba coexist, the eutectic temperature is determined by the soluble S amount. The sulfide itself does not affect the eutectic temperature. The Ca and Ba contained in the inoculant increase the eutectic temperature difference, in addition to causing nucleation. Highly concentrated soluble S retards the growth of eutectic cells and curves the graphite.

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  Authors have developed a new mold release method by reducing the air pressure of poured green sand mold in a chamber. A moisture-condensed layer, which weakens the mold strength, appears when the temperature of the mold reaches around 373 K after pouring. The mold is placed in a chamber. Water near 373 K in the moisture-condensed layer of the mold starts to boil when the chamber pressure is reduced. Boiling generates a difference of pressure between the inside and outside of the mold, which breaks the mold. In this study, the mechanism of the mold release method using vacuum was investigated through fundamental experiments measuring the temperature and pressure of the sand mold after pouring. The actual phenomenon of mold release using vacuum in the chamber was confirmed. Furthermore, the properties of the green sand after mold release was clarified.

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  The influences of the incident angle of the ultrasonic wave on the measurement of remelted zone thickness in aluminum alloy castings were examined. When ultrasonic waves generated from a focussed probe were incident on a specimen surface with an oblique angle, the focussing of the waves in the specimen became worse with increasing angle of incidence. When an incident angle was less than 10 × (π/180) rad, the remelted zone thickness was evaluated from distributions of back scattering wave intensity, but the evaluated value of the remelted zone thickness became larger with the increase of the incident angle. When the incident angle was larger than 10 × (π/180) rad, the intensity of back scattering waves from a boundary between the remelted zone and the matrix became so small that the position of the boundary could not be detected distinctly. Thus the remelted zone thickness was not evaluated. The remelted zone thickness was also calculated numerically assuming that the intensity of the ultrasonic wave decreased with increasing travelling distance. The calculated values were in good agreement with the measured results, when the attenuation coefficient was assumed to be 1 to 2 dB/mm.

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