The author published sometime ago a paper on the performance of acidic electric furnace ("Tetsu to Hagane" Year XXIII, No. 2, p. 117). Since then, the performance is continued with excellent results. Although the complete results are not allowed to be published, the author describes herein, so far as being permitted, the statistical results of the actual operation, the results relating to properties of material, the chemical changes in furnace, etc for the reference of members.

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The recent progress in various industries in Japan demands large steel castings for machines and apparatus whilst the quality of the castings influences in a great deal upon the efficiency of the machines and appratus.
The Muroran Works of Japan Steel Works have manufactured many large steel castings and their quality has been gradually improved during the past 30 years.
As an example of the improvements made in the Works, the author deals with, in this paper, the changes in foundry and the improvement in quality of steel castings for hydro-electric power plants (runner and spiral castings) in order to enrich material for the study on foundry work of this kind.

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The author studied systemetically on the oxidation resistance, corrosion resistance and mechanical properties of the following patented special stainless steel.
Principal compouents: -
C 0·25, Si 0·1-1·5, Mn 0·2-2·0, P 0·3, S 0·1, Cu 0·05-1·5, Cr 15·0-25·0, Mo 0·1-6·0, Fe and other impurities rest.
If necessary, one or more than onc of the following elements can be added with in the limits as shown below.
Ni 10·0, W 2·0, V 1·0, Al 2·0, Ti 1·0.
He found that by changing property the ratis of Cr, Mo and Ni in the patented limits, many high quality alloy steels can be obtained as constructional materials suitable for various chemical industries.

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An accurate consideration is given on the carburizing of iron by gases which has heretofore been wrongly represented thus:
3Fe+2CO=Fe3C+CO₂……(1)
Since solid cementite is unstable and is decomposed at all temperatures into graphite, the reaction
Fe₃C→3Fe+C……(2)
is complete. Then by adding the equilibrium (3), i.e.,
2CO C+CO₂……(3)
to (2), we obtain
Fe₃C+CO₂→3Fe+2CO……(4)
which does not permit solid cementite to be produced by the reaction of iron with CO.
The carburizing reaction must be represented as follows:-
(Solid soln.)+2CO C(Solid soln.)+CO₂
The carbon content in the solid solution rises with the increase in the partial pressure of CO, until it becomes saturated with carbon. The equilibrium taking place over the saturated solid solution CO-existing with carbon is
2CO C+CO₂……(5)
These behaviors are shown in Fig. 2. Combining Fig. 2 with the Fe-C diagram, in which the solid solubility of oxygen may be neglected, the carburizing equilibria may be understood.
From the above considerations, it is possible to determine, by resorting to a method where thin iron plates are carburized and the saturation content of carbon analyzed, the solubility curve of carbon in Austenite, that is, the ES curve in the Fe-C diagram which has already been obtained by thermal analyses. The experimental results are shown in Fig. 4.
The solubility of carbon in α-iron is so small that below the eutectoid temperature carburizing can scarcely occur and only up to 0·03% C. Consequently, at these temperatures, decarburizing of steel is inevitable in spite of the reducing nature of the atmosphere.

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We studied on the effect of tungsten, molybdenum and vanadium on the transformation points and mechanical properties of a few kind of Ni-Cr steel and stainless steel.
Specimens were prepared in a 35k.V.A. high freqency induction furnace, remelting raw materials of carefully refined basic electric arc furnace steel. One of the above elements, W, Mo and V, was added to the molten steel, and after casting, ingot was forged and rolled to a rot of 20mm in diameter.
At first, transformation points were determined by the thermal dilatation method, and then hardness, tension and impact tests on the same sample were carried out after various heat treatments.
As for Ni-Cr steel, it is found that molybdenum is the most powerful in the descending effect on the Ar1 transformation, followed by tungsten, and vanadium is feeble. The effect of these elements on the tensile strength of Ni-Cr steel is difficult to appreciate in the case of tempering at the low temperatures such as 300°C after quenching, but when the tempering temperature is raised to 500-600°C, the effect becomes remarcable; that is vanadium is most affective and tungsten is rather feeble.
In the case of the stainless steel, containing 18% chromium and 8% nickel, tungsten, molybdenum and vanadium act to increase the tenacity. On the stainless steel of 13% chromium type, it is found that the above three elements slightly affect on the physical properties.

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The detemination of fatigue limits by an Ono's Repeated Bending Machine was made on duralmin and super-duralmin which has been immersed in sea water for a definite period. The results show that the damage due to the corrosion of sea water is very great in spite of a short period of immersion. The purpose of these tests is not for the discussion on general theory of "Corrosion Fatigue", but is merely to investigate the decrease of fatigue limits when the materials are accidentally corroded.

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