Anomalies are observed in measurements of electromotive force and electric conductivity measurements of solid oxide electrolyte cells involving Cr(s)-Cr₂O₃(s) electrode. Transformation in Cr(s)-Cr₂O₃(s) system at about 1 653 K is suggested to explain the anomalies mentioned above on the basis of measured temperature dependencies of electromotive force and total and electronic conductivities of the cells.

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An HSLA steel containing 1% Cr and 0.2% V was obtained in a dual phase form by cooling from the austenite field to the (α+γ) range, then quenching into iced brine. The present morphology consists essentially of polygonal ferrite and martensite. It exhibits higher strength than dualphase steel obtained by quenching from the intercritical range. Though this result has been reported before on a similarly treated Fe-Si-C steel, the present steel shows larger ductility. This is due to the effect of Cr and/or V on the interstitial content of ferrite. The yield strength, tensile strength and elongation were observed to vary linearly with the volume fraction of martensite in both quenched and tempered microstructures. Previous equations reported by Onel and Nutting, ¹²⁾ relating hardness of tempered martensite to its ferrite grain size were found applicable to the present tempered dual phase steel after averaging the free-ferrite and recoveredferrite. Furthermore, the yield strength varies with the average ferrite grain size via a Hall-Petch type relationship.

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In order to understand the air oxidation of molten steel during teeming, the model experiments on the gas entrainment of pouring stream were carried out by using water, ethanol, glycerin aqua solution and liquid tin.
The breakup length of pouring stream depends on the shape of nozzle, the pouring rate of liquid and the flow of liquid in the tank.
It was found that, in the range of the present experiment, the amplitude of disturbance at the nozzle exit, ε₀, decreases with the decrease of nozzle length and pouring rate as indicated by the following equation. In (a₀/ε₀)=44.3(l₀/D₀)^-0.75(Re)^-0.1 The rates of gas entrainment by the pouring stream increase with increasing height of teeming and rate of teeming.
It is confirmed that the rate of gas entrainment can be represented by a model assuming that the gas entrainment does not occur under the true cylindrical stream but arises by the cavity produced by the collision between the bath surface and the stream surface protuberances.
Consequently, taking the cavity radius R_c into account, the rates of gas entrainment can be described for all kinds of liquid stream as follows; V_g/V_l=0.02{(R_c-a)/a₀}³

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In order to develop the austenitic steell with the nonmagnetic characteristics, microstructures, mechanical properties, magnetic permeability and electric resistivity of Mn-Cr-Ni steels with much amount of manganese as an austenitizing element have been examined. The results obtained are as follows.
It was found that composition range showing stable austenite phase lays on the higher content side of the line connecting approximately 10%Mn-10%Cr and 20%Mn-0%Cr in Mn-Cr-1%Ni phase diagram. This composition range moved to the line connecting approximately 20%Mn-10%Cr and 23%Mn-0%Cr in the case of cold-rolled steel plate. High toughness and magnetic permeability (μ) under 1.01-1.02 were obtained in the steel with complete austenite phase. Magnetic permeability markedly increased by small amount of martensite in austenite phase. Therefore, it is necessary that nonmagnetic steel have complete austenite phase. The relationship between electric resistivity (ρ) and alloying elements; manganese, chromium, nickel, silicon in austenite phase, can be written as ρ=1.27[%Mn]+0.66[%Cr]+1.62[%Ni] +5.90[%Si]+36(μΩ-cm) From the above results, 25Mn-5Cr-1Ni steel may be selected as an optimum composition from the view points of stable austenite, high toughness, nonmagnetism and suitable electric resistivity.

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Effects of selenium and tellurium on the surface tension of molten iron and on the Wettability of alumina by molten iron were measured with sessile drop method at 1600°C and results were discussed together with those of oxygen and sulphur.
The main results are as follows.
(1) Selenium and tellurium acted as the surface active agents and the surface activity increased in the order of: oxygen, sulphur, selenium, and tellurium.
(2) The contact angle between molten iron and alumina decreased with the addition of oxygen and increased with the additions of selenium and tellurium. While, sulphur scarcely affected the contact angle.
(3) The interfacial free energy between molten iron and alumina decreased with the increasing of these elements.
(4) The work of adhesion between molten iron and alumina decreased with the increasing of sulphur, selenium, and tellurium, and increased with the increasing of oxygen.

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Precipitation of 6 phase in an Fe-25Cr-7Ni-3Mo alloy with α/γ duplex structure has been studied systematically and the following results were obtained:
(1) TTP diagram for the a phase precipitation was a C-type with a nose at 820°C.
(2) σ phase nucleated on the α/γ interfaces and grew into α grains as a eutectoid reaction: α→σ+γ. Enrichments of Cr, Mo and W atoms into σ phase were remarkable.
(3) Hardness increase by the precipitation of σ was not so large, while impact value markedly decreased even at a few percent precipitation. σ phase was also found to decrease hot ductility.
(4) The precipitation range during cooling was 700-900°C and σ phase precipitation could be avoided if cooling rate was larger than about 20°C/ min after solution treatment.

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Effects of hot or cold deformation and thermal history on theσ phase0 precipitation in (A) a 25Cr-7Ni-3Mo and (B) a 23Cr-6Ni steels with ferrite/austenite (α/γ) duplex structure have been studied. Results obtained are as follows:
(1) The incubation time for the σ phase precipitation in Steel B was a couple of orders of magnitude longer than that in Steel A. This should be attributed to the difference in chemical composition between two steels, especially in a phase, where the majority of σ phase is known to precipitate.
(2) σ phase precipitation is enhanced by hot work or thermal strain as well as cold work. The enhancing effect of cold work is predominant, and the precipitation of σ particles is observed in γ grains as well as in α grains.
(3) The precipitation of σ phase is retarded by the prior heating history before aging; (a) heating at the α single phase region or (b) remelting. Especially the effect of the treatment (b) is remarkable. These retardation effects can be ascribed to homogenization of alloying elements by these heat treatments. The difference between the cases of (a) and (b) is thought to result from the degrees of their homogeneities.

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New process “SMP” (Slag Minimum Refining Process) which consists of hot metal desiliconization stage in hot metal container and dephosphorization and decarburization stage in LD converter has been studied in order to reduce the consumption of refining fluxes and slag volume yield in conventional LD process.
After experimental studies which have been carried out in KR equipment and conventional LD converter to estimate the feasibility of this new process, it becomes clear that hot metal desiliconization treatment can be done with simple equipment by using proper desiliconization agent and flux and its proper adding method.
By this new process, CaO consumption for dephosphorization in LD converter and slag volume can be reduced drastically with decreasing Si content in hot metal and that CaO consumption and slag volume required is 18kg/t-s, 42kg/t-s at Si=0.15% for low carbon rimmed steel. As a result, lining life of refractory can be extended and the amount of metal and heat losses can be decreased and it makes the LD refining very stable.
Based on the results obtained by the above experiments, a practical equipment of hot metal desiliconization treatment has been installed and came in use in October 1979, and now is in a stable operation.

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In order to investigate carbon distribution between solid and liquid phases in Fe-C binary system, austenite-liquid phases equilibrated in the temperature range from 1150 to 1400°C were quenched and the carbon concentrations in each phase were determined by EPMA.
The results obtained are summarized as follows.
(1) Solidus and liquidus obtained coincided well with the curves given in other recent works.
(2) Diffusion distance of carbon from liquid-solid interface into solid phase during quenching was calculated. From the results of the calculation, it became clear that carbon concentration in the center of solid phase was not influenced by the carbon diffusion during quenching,
(3) Equilibrium distribution coefficient of carbon in Fe-C system was determined thermodynamically. Solidus corresponding to the liquidus obtained experimentally was calculated by using the above coefficient and it was in good agreement with the experimental one.

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