The solution of nonequilibrium second phase (θ) of Al-Cu alloys in the later stages of solution treatment have not yet been made theoretically clear. This paper attempted mainly to investigate this behaviour by approximate analysis given by a simple model based upon primary arm spacing as an effective diffusion distance of θ-phase which has crystallized at the boundary of dendrite element. Results expected theoretically are in approximate agreement with that of experiments for complete dissolution time and solution behaviour (especially at the later stages) of θ-phase. This result is comparatively better than that of conventional analysis by Flemings. A remarkable decrease in solution kinetics of θ-phase is shown by addition of 0.15%Ti to Al-4.32%Cu alloy.

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  Pig iron inoculation has chill decreasing effect in gray cast iron. The lower the sulfur content in inoculant pig iron, the lower is the depth of chill formation, the chill depth is remarkably kept at a lower level where the percentage of sulfur content is 10^-3% level. The higher the carbon content in inoculant pig iron, the lower is the depth of chill formation. Especially, where inoculant pig iron has about 5% carbon, chill depth is kept at a lower level in both quick and slow rates of melting. The chill level of specimens which are melted at a quick rate and inoculated by pig iron is always low, but further decrease of chill depth by combined inoculation of Ca-Si can not be expected. The chill level of specimens which are melted at a slow rate is high, and more decreaee in chill by combined inoculation of Ca-Si can be expected.

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  Since many water-soluble molds developed up to now consist of water-soluble salts, special molding techniques are required, and complete dissolution removal of the compacted salt molds requires considerable time. In addition, complete recovery of the salts from the diluted solution is very difficult. For the purpose of improving the salt molds, water-soluble ceramic mold was studied.
  The mold contains alumina as a base material, and potassium carbonate (K₂CO₃) as a binder. The mold was formed from the mixture of alumina, K₂CO₃ and water, and dried at 200°C. After drying, the transverse strength of the molds indicated above 50kg/cm², over the temperature range of 20°C-700°C. Below 750°C, neither chemical changes of the materials nor chemical reactions between molten aluminum and the mold materials was found. Consequently, sound castings were obtained using this mold. After casting, the molds can be decomposed by a small amount of water. In addition, the alumina can be precipitated in water, and K₂CO₃ can be separated by evaporating water.

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  An experimental investigation is carried out to analyze the performance of canopy exhaust hoods where a soap-bubble method newly developed is applied. By using this visualization method, it is now possible to introduce the effectiveness of the hood and the values of effectiveness are measured quantitatively. The results show that the existing two typical design-methods of canopy hoods have some deficiencies in obtaining reliable performances. In determining a hood capacity, the present analysis includes the effect of kinematic energy carried with contaminated air. This method expressed by a formula provides an effective approach to the design of a canopy hood with an optimal performance for a given rate of contaminants.

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  This investigation is concerned with the mechanical properties and the fractographic analysis on the Charpy impact fracture of eutectic graphite irons cast in metal molds. All irons were annealed at a cycle of 2hr soaking at 900°C and furnace cooling to 700°C. The composition of the irons was about 3.46%C, 2.73%Si and 0.42%Mn. The annealed microstructure consists of type D graphite morphology and completely ferritic matrix, which contains about 40vol.% graphite-free ferritic dendrites. Impact test were performed using the standard Charpy U- and V-notched 10mm square test pieces machined from the 20mm diameter casting bars. In order to obtain the load-time curves, the instrumented impact tester was applied.
  The U- and V-notch impact values were approximately 0.2 kg⋅m/cm² in all cases. At each test temperature (100°C∼−196°C), there was no difference in the impact values and the visual examination of the fracture surface. However, it was found that the fracture pattern with testing temperature could be distinguished with the scanning electron microscope. At temperature under 0°C, fracture of dendritic ferrite matrix showed typical brittle behavior with river pattern (a cleavage mode). The river pattern disappeared at temperatures above 0°C, but very ductile behavior did not appear with dimple pattern. Fracture surface ratio (%) of these dendritic ferrite matrix measured by SEM increased from about 2 to 30, as the test temperature was reduced from 100°C to −196°C. Further, the data of eutectic graphite irons were also compared with the data of type A flake or spheroidal graphite cast irons.

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  The molding sand which was made of a small amount of ultra-rapid hardening cement and containing additives was investigated for the purpose of establishing more effective molding process sand to reduce cost, increase efficiency of the molding process and keep a good environment for demolding.
  As addition of an accelerator composed of inorganic oxide and a surface stabilizer mainly composed of condensation of β-naphthalin sulfonic acid and formalin increases the degree of hydration during initial hydration of ultra rapid hardening cement and makes the structure of hardened binder dense, the molded sand develops suitable mechanical strength at the initial and later stages and has good surface stability enough for pouring of metal in spite of the small amount of cement. Recommendable proportion of the molding sand made of ultra-rapid hardening cement, water, the accelerator and the surface stabilizer were established in the range of 2-4, 3.0-6.0, 0.3-3.0 and 0.4-0.6 parts against 100 parts of silicious sand, respectively, according to temperature, compactness of the silicious sand and necessary properties for mold such as mechanical strength.
  In molds with insuffcient accelerator and surface stabilizer, coating the surface by blowing the surface stabilizer or resin emulsion after molding immediately is effective in making the casting process problemless because the surface stability and the hardness of the surface is remarkably improved. Free-water decreases with decrease of the cement content. Collapsibility and refractoriness of the foundry sand become better than those of previous process sand which used a large amount of ultra-rapid hardeningcement. Deformation under load at high temperature is very small just as with previous molding process sand.

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  In this paper, the effects of thermal factors on the soundness of Zn-Al binary alloy castings with the various freezing ranges are described. Various thermal factors can be obtained using copper chill and heating plate on both ends of castings. The castings of vertical and horizontal plate shapes are solidified unidirectionally from chilled end to heating plate end. The solidification data are obtained by thermal analysis and the casting soundness is assessed by measuring the ultimate tensile strength and segregation at different locations of the castings. The maximum ultimate tensile strength of Zn-4% and 50%Al alloy castings can be obtained at the chilled end, but that of Zn-22%Al alloy castings is obtained at the center of castings. The statistical analysis indicates that the ultimate tensile strength and the freezing index θ/G have a better correlation in Zn-4%Al alloys, but the ultimate tensile strength have better correlations with the average cooling rate Rc₁ in Zn-22% and 50%Al alloys.
  The relations of the ultimate tensile strength between thermal factors are influenced by the constituent of casting alloys. The examples are listed as follows :
    for Zn-4%Al alloy Y=−1.30 lnX₁+13.0
    for Zn-22%Al alloy Y=−1.90 lnX₂+C
    for Zn-50%Al alloy Y=1.74 lnX₂+24.4
    Y : ultimate tensile strength, kg/mm²
    X₁ : freezing time (θ)/temperature gradient (G), cm.min/°C
    X₂ : cooling rate (Rc₁), °C/min
    C : constant, 33.0 for horizonal plate shape casting
                        34.5 for vertical plate shape casting
  Zn-22%Al alloys have more porosity near the heating end but in Zn-50%Al alloys coarse porosity is observed near the heating end of castings, and fine porosity is observed over the whole of the castings. The light and shade patterns of radiography for Zn-22% and 50%Al alloy castings show the segregation of Al concentration. The maximum Al concentration differernce of Zn-22%Al alloy vertical plate shape castings in the top and bottom direction is approximately 8%, but in the freezing direction of castings the Al concentration is maximum at the center and minimum near the heating plate except for the bottom of the castings.

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