The metal drop method is useful for clarifying the formation of defects in die castings and the solidification phenomenon in spraying.
  In this study, a melted aluminum droplet in a crucible was dropped onto a copper mold at constant pressure. The falling height, that is, the distance between the crucible and copper mold was also changed. The external shape and the shape of a vertical section of solidified specimens were examined, and the thickness of specimens was measured. Area, periphery length, and shape factor of the bottom of the specimens were also measured quantitatively.
  The shape of the solidified specimen changed from Type A, Type B to Type D with increasing falling distance ; Type A : disk-like or columnar, Type B : doughnut-like at peripheral region and thin plate-like at center region, Type D : complex at main part and simple at dispersed parts. A Type B-D shape was also observed, which was neither the shape of Type B nor that of Type D. A solidification mechanism was proposed to obtain these shapes. It was clarified that falling height affects on the shape of solidified specimens.

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  We call Fe-C-V-Ni-Cr type alloys containing spheroidal vanadium carbide (VC) spheroidal vanadium carbide cast irons (SVI). The friction wear and rolling contact fatigue properties of SVI were investigated by a friction test using a lathe and a Nishihara type rolling wear test machine with light oil lubricant respectively. Friction wear resistance of SVI was much higher than that of ADI (600HV50) because the spheroidal VC with high hardness raises wear resistance, Friction wear resistance of Fe-2.62% C-10.46% V-7.84% Ni-17.92% Cr-0.84% Si-0.68% Mn(specimenB) with consistent VC distribution and little crystallization of plate-like type Cr-carbide was highest among the three specimens. SpecimenB also showed the highest rolling contact fatigue limit (F^∗), and Fe-3.02% C-10.18% V-8.4% Ni-18.45% Cr-1.07% Si-1.07% Mn(specimenA) showed lower F^∗ than that of Fe-2.30% C-10.20% V-10.26% Ni-18.24% Cr-1.25% Si-0.95% Mn(specimenC) with the lowest hardness. In order to raise friction wear resistance and F^∗ of SVI, homogenization of distribution of VC and reduction of Cr-carbide are required.

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  When casting defects occur in foundry shops, engineers may need to think of several methods to achieve good quality castings based on previous case examples. In practice, however, it is not easy to select the best method theoretically and promptly. Moreover, even if the best-proposed method is selected, most of the time, it is difficult to show the grounds of the decision-making logically. In this study, we attempted to develop a prototype decision-making support system which can indicate the score for evaluating methods to eliminate casting defects. In the system, AHP (analytic hierarchy process) is used to calculate the priority of elements important to the problems which has occured. At the same time, a user-friendly man-machine interface was developed for input/output. The feasibility of use of the system to support human decision-making in foundry shops was examined.

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  Plastic deformation with wet conditions causes marked embrittlement in austempered ductile cast iron (ADI). We call this behavior “Water Embrittlement effect”. Water molecules exist as water vapor in room air. Tiny amounts of water vapor in air are thought to embrittle ADI. Tensile tests were performed under different relative humidities. The purpose of this study was to examine the effects of water vapor on tensile properties of ADI. The results obtained were as follows : Water vapor in room air caused minute embrittlement in ADI. The increase in partial pressure of water vapor increased the degree of embrittlement. The humidity at which the embrittlement effects appeared clearly was above 50% RH. The increase in the exposure time to water vapor decreased the tensile properties. The embrittlement effect of water vapor may be due to surface reactions on the specimens.

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  The characteristic of green sand changes as it is heated by pouring. Then, after experimental repeated pouring, the green sand composition, and its properties were measured, and the penetration defect caused in a test casting was detected. As a result, it became evident that the sea coal in green sand changed the condition by the heat influence. That is, the sea coal powder changed to adhere to sand surface as the total clay removal. After heating, the oolitics increased, the specimen density increased, and the scabbing time decreased. The penetration defect became difficult to occur when volatile matter in sea coal was more and ash in sea coal was less.

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