Experimental work was carried out to develop a technique for making titanium castings free from porosity by static molds. Plates, 2cm thick, 6cm wide and 8 cm high were vertically cast without risers and used to assess porosity. The soundness was ascertained from a simple visual inspection of a longitudinal section through the casting. Castings had extensive gas pores regardless of types of melting stock, e. g. sponge or rolled bar when melted and poured under reduced pressure of argon. Porosity was also observed in castings made in the copper mold previously heated at 500 K in vacuum to exclude the effect of interaction of the metal with the mold and the effect of gases in the mold. The addition of various elements less than 2 mass per cent, bottom gating and control of melting rate were not effective for the prevention of porosity insofar as melting and casting were done under reduced conditions. Soundness was improved by increasing the pressure of argon during melting and casting processes and porosity free castings were obtained under the pressure above 250 kPa. Bridging of the charge in the crucible could be avoided when melting was conducted under pressurized conditions. From these results it was deduced that calcium gas generated by the reaction between lime crucible and titanium melt is one of the causes of porosity in the castings produced by this process and the boiling of calcium is suppressed by the pressure of argon.

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  In the evaporative pattern casting process, the largest cause of defects is the formation of liquefied resin and gas associated with thermal decomposition on the pattern. In this study, simulations which rapidly heated the original beads for the evaporative pattern in a reaction tube, were carried out to quantitatively measure the gas pressure, the amount of produced gas, and the amount of mist produced in thermal decomposition of the pattern. Then, the effects of thermal decomposition temperature on the composition of the original beads were studied to determine the gas pressure, the amount of produced gas and the amount of produced mist in thermal decomposition of the beads. The results obtained are summarized as follows : 1) The gas pressure, the amount of produced gas, and the amount of produced mist in thermal decomposition of the original beads increased when thermal decomposition temperature was increased. 2) It was found that the gas pressure and the amount of gas produced in thermal decomposition increased as the amount of PMMA increased in the original beads. 3) As the PMMA content in the original beads increased, the amount of mist produced in thermal decomposition decreased. 4) It was found that both the number-average and weight-average molecular weight in the extracted mist decreased when thermal decomposition temperature was increased, and the EPS content in the original beads increased.

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  Wet slip-rolling contact fatigue tests of austempered spheroidal graphite cast irons were performed using Nishihara-type tester to clalify the effect of the graphite nodule size on surface spalling. In contrast to the UTS, elongation and hardness of ADI were improved, the rolling contact fatigue endurance limit of ADI was decreased with decreasing the graphite nodule size. The microcracks initiated from graphite nodules on the contact surface accerated the tipping, followed by spalling. The decreasing graphite nodule size, i. e. increasing the number of graphite nodules enhanced the frequency of initiation of microcracks, therefore the number of cycles to the spalling was diminished.

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  Highly increased usage of high performance engines has created a tremendous demand for exhaust components which can resist severe heat enviroments to nearly 1273 K. Such cast irons as high Si and austenitic ductile cast irons are not able to meet those requirements. Then the authors investigated some alloy steels to be able to improve thermal deformation on the basis of ferritic heat-resistant 18 % chromium steel having excellent oxidation resistance. As a consequence of these effforts, we have developed a new heat-resistant cast steel composed of 0.2 % C-18 % Cr-Ni-W-Nb for exhaust components required especial resistance to thermal deformation.

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  Swelling and shrinkage are more likely to occur in S. G. Iron castings then in F. G. Iron castings. This is due to the mushy solidification of S. G. Iron. Plate and cylindrical S. G. Iron castings were quenched during solidification to observe the progress of solid fraction. Solidification simulations were carried out to compare with the experimental results. A simulation considering diffusion of carbon through austenite envelope gave similar distribution of solid fraction to the experimental results. Measurements of shell movements were also carried out. Metal wall of plate casting tends to shrink while that of cylindrical casting expands. Calculation based on the growth of graphite surrounded by austenite envelope gave results qualitatively in agreement with measurement on expansion of cylindrical casting.

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