Effect of Mg content in spheroidizer on the chilling tendency of spheroidal graphite cast iron melt was investigated to produce high strength iron castings. Both iron melt treated with Fe-Si-3%Mg and Fe-Si-6%Mg was poured into a cartridge of CE meter. Cooling curves and cast structures were observed on the specimens. It was found that eutectic start temperature of iron melt with 3%Mg was higher than that of one with 6% Mg. formed ledeburite structure.

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  The solidification sequences of multi-component white cast irons containing different types of carbides were investigated by means of thermal analyses and quenching tests. In the case of cast iron with MC and M₂C eutectic carbides, first austenite (γ) phase or MC carbide precipitates as a primary phase, then the L→γ+MC eutectic reaction takes place and finally, the solidification finishes by the L→γ+M₂C eutectic reaction. In cast iron in which MC and M₇C₃ carbides coexist, the solidification begins with the precipitation of the primary γ phase or MC carbide, followed by the L→γ+MC eutectic reaction goes, and then the L→γ+M₇C₃ eutectic reaction. As for cast iron with MC, M₇C₃ and M₂C eutectic carbides, the solidification sequence is as follows : L₀→γ+MC+(L₁), L₁→γ+M₇C₃+(L₂) and L₂→γ+M₂C. EDS analyses of alloy concentrations in the liquid regions of the quenched sample demonstrated the propriety of each eutectic reaction during solidification.

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  The development of technologies to recycle low-level radioactive waste from decommissioned nuclear facilities is a key issue from the view point of reducing waste and the recovering natural resources. Radionuclide tranport behavior during melting is an important factor in the safety of radioactive metal (scrap) recycling. We obtained data on radionuclide transport from basic melting tests conducted in JAERI, and analyzed the data by using a statistical analysis method. As a result, it is found that the transport of Mn, Zn and Sr is mainly dominated by oxydation-reduction reaction between slag and molten metal and is explained on the basis of oxygen concentration in slag. On the other hand, the transport behavior of Cs is not explained by oxydation-reduction reaction. It is assumed that the partitioning of Cs to the off-gas is affected by its evaporation and restraint in sillicic acid network structure.

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  The machinability of as cast and heat treated high chromium cast irons containing 1mass%Cr, 15mass%Cr or 25mass%Cr was examined using a lathe. Some irons were cooled slowly after heating at 1073K to 1273K for 7.2ks. The other irons were tempered at 773K or 973K for 7.2ks after heating at 1173K to 1273K for 7.2ks to 10.8ks and quenching into oil bath. A WC-Co sintered tool coated with ceramic was used in turning. The machinability of irons tempered at 973K is superior to that of the other heat treated ones. Because as cast 15mass%Cr and 25mass%Cr irons contain high amounts of austenite (γ) and are consequently hardened by machining, the induced hard layer reduces machinability of irons. Damage of tool becomes larger as the hardness of irons increases. Thickness of chips becomes smaller as the hardness of irons increases.

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  Laser surface alloying of cast irons was carried out to obtain harder surface by carbide formation of alloyed element and graphite in the substrates. The alloying elements used were chromium or tungsten. To feed the alloying elements, a powder coated layer or electro plated layer was formed on the surface of the specimens prior to laser irradiation. Alloyed structures were obtained under the proper treatment conditions and X-ray diffraction tests showed that the modified structure with chromium powder layer contains chromium carbide (Cr₇C₃). Their microhardness was 950HV. The microstructures of tungsten treated speci-mens have primary dendrites and tungsten rich smooth matrix. X-ray diffraction also revealed the presence of W and Fe complex carbide and cementite. The microhardness of the tungsten alloyed structure, which is higher than that of melted-solidified structure without alloying element, was 1300HV.

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  The flow behavior of solid-liquid two phase flow during mold filling effects greatly on the properties of castings such as semi-solid metal products and particle-reinforced metal matrix composites. In this study, the flow behavior of solid-liquid mixture flowing into a rectangular cavity with a core was investigated using a water-polystyrene particle mixture. The shape of the free surface of the mixture in the cavity with a core was more stable than without. Even a small core of 2mm×2mm was effective. The main reason for the phenomena is the change in the flow path of the mixture due to the core. Although gas was entrapped near the core, the amount of the gas was less for the core with the same width as the gate than the cavity without the core. The low-concentration region of solid particles appeared at the V-shaped flow boundary, which existed upward from the bottom of the core. The concentration of particles decreased at the center of the rotation of flow, which existed under, at the side of, and above the core.

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  This paper presents an algorithm for simulating three dimensional fluid flow during mold filling of castings. The method for the discretization of mass and momentum conservation equations is based on the direct-finite-difference-method (DFDM). It is intended to simulate fluid flow with high accuracy and short CPU time. Efforts were especially made to model the shape of a free surface and calculate mass and momentum fluxes within the vicinity of the free surface regions. The reliability of the model was verified by comparing the simulated results with the experimental ones, and good agreements was achieved.

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  The purpose of the study is to show how friction and wear are affected by θ phase (CuAl₂) in Al-Cu alloys. To achieve this purpose, six pieces of Al-Cu alloys with different θ phases were fabricated by an usual casting method and used for the tests as a disk specimen. Friction and wear tests were carried out using a pin on disk type machine under dry and lubricated friction conditions. The results obtained are as followsb ; In dry friction tests Al-Cu alloys containing 50 to 91% θ phase area fraction (Af) showed a low friction coefficient and superior characteristics in specific wear rate or seizure resistance when applied to G2-cemented carbide. Under the lubricated conditions, the effecis of the θ phase depended on the Af and PV values, that is, the friction coefficient and wear damage were the smallest for the alloy specimens containing 7 and 78% Af θ phases.

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  An experimental study was carried out on a semi-solid diecasting process using a mixture of elemental alminum and silicon powders. The mixed powder with hypo or hyper eutectic composition was heated to the semi-solid state temperature and then stirred mechanically. After stirring, the powder was forced into the preheated metal die. The fluidity of the stirred hypo eutectic slurry was high and stirring improved the surface quality of the products. The α phase or Si phase particle in the slurry grew globular from collision during the stirring. Eutectic structures were refined by the stirring of the slurry. The tensile strength, elongation and hardness of the products made from the stirred slurry were higher than those of products made from unstirred slurry.

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