Studies were made on the crystallization of primary graphite in hyper-eutectic melts and on carbide matastabilizing tendency occuring at the time of solidification. It was found that the melts with high hyper-eutectic composition can crystallize the primary graphite even by rapid cooling such as quenching in water. As the contents of carbon and silicon increased, carbide metasrabilizing tendency decreased, and as the composition of alloy approached that with the liquidus of graphite of 1,450°C, cementite was not formed at all even in the castings which solidified in nearly five seconds. Presumably, such lowering of carbide metastabilizing tendency is caused by the existing primary graphite which absorbs the carbon formed by eutectic reaction L→γ+C, preventing the metastable reaction.

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  Fine grained matrix structure of 4-5μ in size and consisting of grains of ferrite and pearlite, can be produced in a wide variety of spheroidal graphite cast iron, by a thermal treatment involving rapid heating to the upper part of the eutectoid transformation temperature range, holding at this temperature and air-cooling. They exhibit significant increase in strength and ductility measured by 0.2% proof stress, tensile strength and elongation of tensile specimens such as 70-83kg/mm² in ultimate tensile strength, 19.3×10³kg/mm² in elastic modulus and 8-14.8% in total elongation. The 0.2% proof stress and ultimate tensile strength of these irons increase in a linear manner with the inverse square root of the grain size according to the equation: σ=σ_i+Kd^-1/2, where σ is proof or tensile strength, σ_i and K are experimental constants, and d is the average grain diameter.
  Microscopic observations under increasing tensile stress revealed that cracks initiate in ferrite grains at the vicinity of graphite nodules, owing to the stress at the end of a slip line. Grain boundaries and pearlitic grains act as major barriers to the propagation of the slip and crack which initiate within the grains. The production of fine duplex matrix structure may offer a new technique for strengthening of spheroidal graphite cast irons, without lowering ductility unlike other most strengthening mechanisms in the past.

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  Fifty grams of the alloy containing 4.3% of carbon, which was composed of electrolytic iron and electrode graphite, melted in a high frequency induction furnace and cast into iron mold, was placed in a fused silica crucible and remelted in a resistance furnace, following which antimony up to 0.8% of molten iron was added to the melt. At 1,35 °C, the graphite spheroidization treatment was done with Fe-Si-Mg(21.4%) alloy and furnace cooled, while the cooling curve was measured. At various predetermined temperatures in the solidification intervals, the specimen was quenched in iced water to interrupt the solidification process. The graphite nodule number and the fraction of solid in the eutectic were determined microscopically. Electron probe micro-analysis and X-ray micro-diffraction analysis were carried out to determine the distribution of antimony.
  By the addition of antimony, there were formation of aggregated graphites at the first stage, quasi-spheroidal and vermicular graphites at the middle stage and thread-like and granular graphites at the final stage of eutectic. It was observed that the aggregated graphites with the morphology of intertwined fine flaky graphites directly crystallized from the melt containing a large amount of antimony, and are surrounded by an austenite shell and grow by the diffusion of carbon through the austenite shell. There was an enrichment of antimony in the liquid in front of the austenite-liquid interface during solidification and then an antimony-rich phase was formed at the austenite boundary at the last stage of eutectic solidification. Therefore, the enrichment of antimony during solidificaiton resulted in the formation of various types of degenerated graphites. According to the previously reported classification of the inhibitory befavior of the harmful elements against the spheroidization of graphite, i.e., sulfur type (Mg-consuming type), titanium type (boundary concentrating type) and lead type (compound type), antimony can be classified into the titanium type.

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  Effects of Be, Al and Si additions for Cu-Sn, Cu-Pb and Cu-Zn alloys and some commercial bronzes on the thermal decomposition temperature of gypsum, made to contact with the alloys, were investigated by a differential thermogravimetric equipment with 20°C/min heating rate and the decolorization of KIO₃ solution in the same way as in the previous report. Amounts of additional elements to raise the thermal decomposition temperature of gypsum up to 200°C above the melting points of contacted alloys, in order to increase the possibility of application for plaster mold casting, were different depending on the additional elements as well as the Cu-base alloys. Addition of 0.5 to 1% of Be and 1% of Al for Cu-5%Sn and Cu-10%Sn alloys, and Cu-10%Sn-2%Zn and Cu-5%Sn-5%Pb-5%Zn bronzes, and 1% of Al for Cu-40%Zn alloy were effective in raising the thermal decomposition temperature of gypsum. Si addition for these alloys was not as effective as the other two elements. Although Be and Al addition for Cu-Pb alloy raised the thermal decomposition temperature of gypsum, as much as 2% of Be for Cu-5%Pb and 5% of Al for Cu-10%Pb alloy were necessary to raise the thermal decomposition temperature of gypsum up to the expected temperature. Si addition for Cu-Pb alloy and Cu-5%Sn-5%Pb-5%Zn bronze lowered the thermal decomposition temperature of gypsum. Therefore, it was considered that combined with the results of Be and Al additions, the improvement of Cu-Pb alloy by additional elements was rather more difficult than other alloys.
  It was considered that these differences of thermal decomposition temperatures were caused by the differences in the degree of contacting reaction between metals and gypsum, that is, thermal decomposition, may be produced by added Al, Be and Si which have much higher Gibb's free energy of formation of metal oxide at high temperature than Cu or other alloying elements. However, it was considered that when simple or complex compounds are formed which have low melting points, such as PbO and PbO-SiO₂ which form between Cu-Pb alloy with or without Si and gypsum, thermal decomposition temperature of gypsum may be lowered by them without the process of deoxidation being prevented.

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  For the purpose of containing austenitic cast iron with the minimum of alloying elements, effects of addition of alloying elements such as Si, Al, Ni, Cu, Mo, W, Cr, V were studied by observing the as-cast structure and measuring M_s temperature of Fe-C-Mn alloy cast iron. Si which is good for preventing the appearance of ledeburite during solidification varies M_s temperature, and consequently Si increment makes austenitization difficult. Aluminum, copper and nickel lower M_s temperature and good for getting austenitic cast iron. Molybdenum, tungsten, chromium and vanadium are carbide forming elements, therefore additions of these elements promote the appearance of ledeburite, Cr and V especially exhibit a powerful carbide stabilizing effect. These elements with the exception of Cr are very weak austenitizer, although they lower M_s temperature.

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  This paper describes the results of the determination of metallic fume generation from molten bronze, 85%Cu-5%Sn-5%Zn-5%Pb alloy, and the effect of double-layer covering on the molten surface on the suppression of fume dispersion. The quantity of fume generation was proportional to the vapor pressure of the metal. Maximum fume generation per unit mass of metallic component of bronze was with zinc fume because of the highest vapor pressure among alloying elements. High fume generation of zinc induced the increment of the quantity of lead fume generated from the molten bronze. High fume genration of cadmium, which is an impurity included in zinc raw material, was measured apparently. The dispersion of metallic fume emitted from the molten bronze is efficiently suppreesed by the double-layer covering on the molten surface with two kinds of material powders. The suppression efficiencies differed somewhat according to the kind of metallic fume.

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