With regard to the stress-strain curves of gray cast iron the following results have been obtained. In the range (i), that is from room temperature to about 500°C, the tensile deformation curves of ferritic and ferrite-pearlitic gray irons show the linear relationship between stress and strain at lower deformation stress and high strain hardening rate at higher stress. In the range (ii), from about 500°C to α→γ transformation starting point, the deformation curves show that the strain hardening rate decreases as the temperature increases, ductility increases up to 770°C and brittleness appears above 770°C. In the range (iii), eutectoid transformation range, the flow stress increases with the rise in temperature in ferritic gray iron. In the range (iv), from α→γ transformation finishing point to about 1,100°C, stress-strain curves show deformation with constant flow stress and elongation increases as the temperature is raised. In the range (v), from about 1,100°C to liquidus, the curves in solid state show low stress and slightly higher strain.
  With regard to the stress-strain curves of ductile iron the followings have been clarified. In the range (i), from room temperature to about 400°C, the curves show high strain hardening and a kind of nonhomogeneous plastic deformation or the so called “serrated flow” takes place within the range of 150∼400°C. In the range (ii), from about 400°C to α→γ transformation starting point, strain hardening decreases as the temperature is raised. In the range (iii), eutectoid transformation range, the wavy flow, the other kind of nonhomogeneous plastic deformation, takes place in the range of 810 to 845°C and it disappears and strain hardening increases as the temperature rises in ferritic ductile iron. In the range (iv), from the α→γ transformation finishing point to about 1,100°C, the curves show high strain hardening just above the eutectoid transformation range and strain hardening decreases as the temperature is raised till the plastic deformation takes place at constant stress. The wavy flow takes place also at higher temperatures in this range. In the range (v), from about 1,100°C to liquidus, the curves in solid state show the occurrence of inter-cellular fracture as the stress increases and the curves in solid and liquid coexisting state show that the flow stress increases slowly and then decreases till tensile fracture occurs.

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  Molten aluminum with different contents of hydrogen were either top-poured or bottom-poured into molds 32mm in dia. and 150mm in height. The molds were prepared in Vacuum Process using various mold materials. Densities of the castings were measured. Amount of porosity of the casting top-poured in the silica sand mold is in proportion to that of metallic mold casting separately poured. The influence of casting conditions are explained in terms of this relationship. Mold materials including considerably fine powder, more than 2cm thick facing sand, top-pouring, vaporization of plastic films and grain refining result in enhancing the degree of porosity.

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  The behavior of Ba contained in ferro-silicon inoculant was analyzed with EPMA to clarify the presence and location of minor elements in the sulfide of gray cast iron after inoculation and holding in an electric induction furnace. By adding a small amount of Ba containing inoculant to molten iron, Ba acts as a deoxidizer and remains at the center of Mn sulfide, and by adding a large amount, the excess Ba combines with sulfur and segregates around Mn sulfide. Meanwhile, Ca from Fe-Si and Ca-Si alloy additions is somewhat enriched in Mn sulfide. Ca also tends to fade, but Ca coexisting with Ba decreases more slowly. It is hypothesized that Ba in inoculant restricts the Ca fade in molten iron, and the retained Ca provides a more effective substrate on nucleation of flaky graphite. Therefore, the coexistence of Ba and Ca in inoculant reduces the chill depth and also restricts the fading of inoculation.

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  The experiment was carried out alternately every other week for comparison of the melting operation of non-lining 30-ton hot blast cupola with a double row and with a single row of tuyeres. A cupola was reconstructed from one wind box for blast air to be blown into the upper and the lower rows of tuyeres separately. Combution ratio in the operation of cupola with a double row of tuyeres showed a value 12% higher than that in the operation with single row of tuyeres. In melting iron having a similar chemical composition at a similar tapping temperature, it has been clarified that the operation of cupola with double rows of tuyeres not only allowed the use of metal charge having 1.4% higher steel scrap ratio in charge mixture but also saved 8% in total coke consumption. The variation in both carbon and silicon contents in cast iron from the cupola with a double row of tuyeres was in a smaller range than that with a single row of tuyeres. In order to obtain better performance from the cupola with a double row of tuyeres, blast air volume per unit section area of the furnace at tuyere level must be kept over 100Nm³/min·m² and speed of blast air passing through an upper tuyere has to be kept over 80m/sec.

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  The paper is concerned with the improvement of impact properties of spheroidal graphite cast iron by forming a ferrite-bainite duplex matrix. When the ferrite and bainite ratio was at best it was proved in the previous work that the strength and ductility were remarkably improved. The instrumented Charpy impact test was performed on irons with different ratios of ferrite–bainite duplex matrix.
  When a ferritic spheroidal graphite cast iron was austenitized at 900°C for a short period and then austempered at 400°C, 55 and 95% volume fractions of upper bainite were obtained, and toughness of the iron was improved to a great extent. Specifically, in the impact test, the absorbed energy at room temperature and the shelf energy reached the maximum value and the transition temperature drop to a minimum at these fractions. The absorbed and shelf energy was 14.5 to 15kg·m/cm², and the transition temperature was −45 to −47°C in the un-notched specimen. These values are somewhat better than those of ferritic spheroidal graphite cast iron. Excellent toughness can be obtained due to the upper bainite phase formed mainly around the graphite nodules. This is probably the result of the upper bainite with high strength and ductility preventing crack initiation at the graphite-bainite interface.

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  Ring mold hot tearing test was conducted on the binary Cu-Sn alloys containing Sn 0 to 15% and on the ternary Cu-Sn-Zr alloys. The maximum frequency of hot tearing was found in the Cu-2%Sn alloy which has the most extended freezing temperature range under practical freezing conditions. Modification of hot tearing was attained by Zr grain refining. The tendency to hot tearing is governed to a greater degree by the extent of the “semi-solid temperature range” from the temperature at which contraction practically starts down to actual solidus. The semi-solid temperature range depends on the whole freezing temperature range and solidification structure.

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