The bulk densities, void ratios and effective thermal conductivities of packed beds composed of steel shot and zircon sand and those of steel shots with two different sizes were measured. The plate casting of aluminum alloy was casted by using these mixtures as a mold in evaporative pattern casting process. The bulk density and effective thermal conductivity of the packed bed composed of a mixture of steel shot 0.5mm in diameter and zircon sand took maximum when the weight fraction of the steel shot was about 0.7, and those for a mixture with steel shots of two different sizes 2.5mm and 0.17mm diameter took maximum when the weight fraction of coarse steel shot was about 0.8. When these mixtures were used, the solidification time of cast were reduced to about 1/3 and 1/4 of that when the mold was made of silica sand.

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  Diffusion bonding of spheroidal graphite cast iron (FCD) to austenitic stainless steel (SUS) has been investigated using three kinds of interlayers : 10μm-thick nickel foil, 50μm-thick Ni 50mass%Cu foil, and 38μm-thick Ni-Si-B alloy foil. In the present investigation the diffusion bonding has been carried out over the temperature range 1223K to 1373K in air atmosphere. Microscopic observation, X-ray microanalysis and scanning electron microscopic observation have been employed to clarify the interfacial characterization at the bond interface. The bond strengths of the joint were also evaluated using tensile test. In case of without interlayer, the precipitations of chromium carbides were observed in the SUS adjacent to the bond interface owing to the diffusion of carbon from the FCD to the SUS. Furthermore, the formation of silicon oxide was observed at the bond interface. The fracture of the joint occurred at the bond interface. The tensile strength of this joint was lower than that of the FCD. Chromium carbides were not formed at the SUS side near the bond interface of the joint bonded with 50μm Ni-50mass%Cu alloy interlayer. In this case, tensile strength of 596MPa and elongation of 16.1% were obtained.

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  In this study, the effects of rare earth elements (RE) and manganese (Mn) addition on the chilling tendencies and mechanical properties of flake graphite cast iron containing 0.08% sulfur (S) were investigated. RE and Mn reacted with S in the melt and the resulting complex sulfide, helped to nucleate the flake graphite, which led to notable graphitization. The addition of the corresponding stoichiometric amount of RE in relation to the amount of S in the melt containing up to 2% Mn was found to refine the pearlite lamellar spacing, improve the shape of graphite and enhance the mechanical properties. In flake graphite cast iron containing 2.0% Mn with 0.2%RE, the relatively high tensile strength of 300MPa or more was obtained without chill.

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  This study is aimed at examining the influence of ultrasonic vibration on the incorporation of Al₂O₃ particles into molten aluminum by melt stirring. The preheated particles were added to a molten aluminum surface at 1023K in a nitrogen atmosphere. The ultrasonic vibration was then transmitted to the molten aluminum stirred at 5rps through a coated stainless steel plate. Ultrasonic vibration causes the composite slurry to change its rheological property in melt stirring. that is, the torque decreases at slow stirring speed and small amounts of engulfed particles. By contrast, the torque increases at fast stirring speed and large amounts of engulfed particles. With the application of ultrasonic vibration to a melt stirring process, the Al₂O₃ particles incorporated into the molten aluminum rapidly increase due to the improved apparent wettability within a given stirring period. Ultrasonic vibration also inhibits the agglomerate particles with atmospheric nitrogen generated in conventional melt stirring.

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  In order to study the growth and constituent of aluminum-alloyed layer formed on the surface of steel, steel bars were immersed into molten aluminum and iron saturated Al-Fe and Al-Mg baths from 1023 to 1123K. In the aluminum and iron saturated Al-Fe baths, the alloyed layer was composed of Al₃Fe, Al₅Fe₂ and α-solid solution, and the formation of Al₅Fe₂ was prevailing. The growth rate of alloyed layer was greater in the iron saturated Al-Fe bath. It followed the parabolic law. In the Al-Mg baths. the thickness of alloyed layer increased with increasing magnesium content and decreased abruptly above 75mass% Mg. The product formed on the surface of steel was Al₃Fe up to 50mass%Mg and changed in the order of Al₅Fe₂, Al₂Fe and α-solid solution with the increase of magnesium content from 75 to 90mass%Mg. The cause of such change in product was thermodynamically explained.

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  A unique method of measuring the positional accuracy of mold cavities related to the mismatch of castings has been developed. With this measuring method, steel balls are put into a green sand mold, and their positions are measured using a coordinate measuring machine, thereby increasing measuring accuracy. The effects of various factors on the positional accuracy of mold cavities in green sand molding were examined. The results obtained are : (1) The positional accuracy of a mold cavity is affected by the average displacement of the flask from the original position during the molding process. (2) The average displacement of the flask is affected by the rigidity of the flask, compactability of green sand, uniformity of the initial sand filling and squeeze pressure.

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  The purpose of this paper is to draw CCT diagrams for heat treatment and clarify the continuous cooling transformation behavior of flake graphite cast irons containing 1.6 and 2.5mass%Si. A metallographic method is used to draw the CCT diagrams, and the Ac₁, Ac₃ and Ms temperatures are measured by the dilatometoric method. The austenitizing condition is 1223K × 900s, and the range of cooling time from the austenitizing temperature to 773K is about 0.5s to 4000s. Ferrite, pearlite, and martensite transformation regions exist in both the CCT diagrams of 1.6%Si and 2.5%Si cast irons. Cementite and bainite transformation regions do not exist in both CCT diagrams, and hypereutectic cementite and bainite are not observed in any of the specimens after cooling in this study. The ferrite transformation region in both CCT diagrams exists in the pearlite transformation region. This phenomenon is considered to occur due to insoluble cementite in the steadite, and that pearllte starting to precipitate from this cementite before ferrite precipitation in the austenite surrounding the graphite. The ferrite transformation curve and Ms temperature shift to a higher temperature with the increase in the Si content. The hardenability of the 2.5%Si cast iron is greater than that of the 1.6%Si cast iron.

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  The temperature field and heat flow in a die during cyclic heating and cooling is approximated using a simple one-dimensional model and numerically calculated with the finite difference method. Based on the numerical calculation results, a periodic steady model is proposed with which the effective mean temperature field and mean heat flow can be calculated without cyclic calculations. The steady model involves 16 variables (mean die surface temperature, amount of heat, cycle time, die thickness etc.) and 6 equations. By giving 10 variables, the rest can be calculated. For example, when the variables, heat flowing from the casting in one cycle, temperature of the cavity and back side, cycle time, heat resistance, and die thickness are given, the mean die surface temperature and heat absorption through the cavity side and back side can be calculated. If, for instance, the mean temperature during cooling is higher than that during heating, the design conditions can be determined as inappropriate.

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  Four series of high chromium cast irons with different chromium and carbon contents and plain carbon steels containing 0.12 to 1.55mass%C were brazed with pure copper filler, and the precipitation behavior of the alloyed phases in the molten copper of the bonded zone and the bond-strength are studied. The site at which the alloyed phase precipitates depends on the Cr/C value of the cast iron and the carbon content in the steel. The critical carbon content in the steel (C_st) can be expressed by equation : C_st (mass%) = 4.5 × (Cr/C)^-1.2. The alloyed phase precipitates at the steel side when the carbon content in the steel exceeds the critical value. When the alloyed phase precipitates at the steel side, a white layer with a chemical composition similar to the σ phase in the Fe-Cr alloy forms at the boundary between the steel and alloyed phase. The bond-strength decreases markedly with an increase in the width of the white layer, due to the fracturing of the white layer or the interface between the white layer and rod-like crystal.

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  A new process for combining alloys in the reaction chamber by inmold process was developed to control transitional graphite structure varying from spheroidal to flake and vice versa. Inoculant was placed on the spheroidizer in the chamber basically. Molten iron was treated in one chamber by two different reactions with time-lag. Spheroidized iron melt was dissolved and cast into the cavity immediately after dissolution of the inoculant. Transitional graphite structure varying from flake to spheroidal was formed in the casting from the lower layer to upper due to some properties differences between the two melts. Effects of the combination of both graphitizer and inoculant placed in the chamber on the graphite structure were investigated in this study. The aimed transitional graphite structure was produced in the casting, when the inoculant was placed on the spheroidizer in the chamber at a ratio from 1.0 to 2.5.

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