The present study was made chiefly to ascertain the oxidizing degree of iron oxide contained in Kamaishi and Takanokura iron ores, the desulphurizing of Kamaishi ore and the improvement of their reducibility by the oxidize-Roasting.
At first, research was made on the chemical compositions and constitutional mineral components of these ores and then the relations between the condition of oxidize-roasting and the change of physico- chemical properties were ascertained.

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The non-metallic inclusions contained in a low chromium steel was studied by microscopic method. It was confirmed by etching test that the inclusions in chromium steel were mainly of SiO₂-Cr₂O₃ system and of SiO₂-MnO-Cr₂O₃ system, and that their natures were as follows.
1) The silica and the chromite easily formed the solid solution.
2) The Mn-oxide and the chromite did not form the solid solution.
3) The silica, the Mn-oxide and the chromite formed the eutectic inclusion of a ternary system.

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It is important to eliminate blowholes or pinholes in iron and steel, the mechanism of growth of them has not been yet sufficiently studied. As a first step, to study this mechanism, it is necessary to analyze the gases existing in blowholes or pinholes. For this purpose, vacuum cutting apparatus was designed and set up instead of drilling the sample in water or oil.
Vacuum cutting apparatus is a lathe which works in high vacuum, and is composed of three parts, that is, high vacuum part. low vacuum part, and atmospheric part. During the cutting with this apparatus, there are two kinds of gases extracted, one is discharged from blowholes or pinholes, the other is evolved from chips because of their high temperature: to prevent the mixing, the apparatus is designed so that its cutting velocity to be as slow as possible. Furthermore, to eliminate gases which evaporate from oil in vacuum, low pressure oil is used. The apparatus is then tested as follows.
(1) Using this vacuum rotary apparatus, high vacuum (10^-5mmHg) can be attained during operation.
(2) Cutting can be done automatically with a turning tool or cutter
(3) Gases discharged during the cutting can be got together by a mercury diffusion pump and a jet mercury pump, then analyzed by an Orsat apparatus.
(4) Gases evolved from the apparatus in vacuum is 0.03-0.04cc in 3hr, and it is neglisible small for analysis.
(5) Cutting temperature is about 60-100°C when measured by a thermocouple of a turning tool and the sample (iron or steel), and temperature of chips is about 100°C when measured by calorimetry of chips.
(6) Gas pressure during the cutting is continuously measured by a pirani gauge, and so the existence of blowhole is immediately and apparently indicated by sudden change on the pirani gauge reading.
Some experimental data observed by this apparatus are as follows.

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The author studied on the hardness and impact resistance of some special cast steels which were made by addition of Fe-V, and Fe-Ti in Cr-Mn-Si cast steel and Al, Al alloys, as well as Ca-Si in Cr-Mo cast steels.
According to the author's conclusion from the present tests, the cast steel of Cr-Mo-Si series containing more than 0.56% Si which was deoxidized by Ca-Si were most superior in strength and tenacity, followed by Al-Si (Al 0.10%), Al-Si-Mg (Al 0.5%), Al-Mg (Al 0.5%), Fe-V etc., and pure Al or Fe-Ti were rather feeble.

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The tensile strength, elongation, number of repeated bending, electric resistance and grain size were measured at room temperature on some heat resisting steels (Fe-Cr & Fe-Cr-Al system) which had been long heated at various temperature from 500° to 1200°C in a vacuum, hydrogen and nitrogen atmosphere. The results were as follows:
The tensile strength and elongation did not vary with the heating below 700°C in vacuum and hydrogen atmosphere. Even in a heating at 800°C, these values did not so decrease as in a heating in air at the same temperature. But in a nitrogen atmosphere, these values of Al-containing steels rapidly decreased and especially the decrease of elongation was remarkable in the heating at 800°C.
Number of repeated bending did not vary in a heating at temperatures below 600°C but began to decrease by a heating at 700°C for 5 days. In a heating at 800°C, these values of Al-containing steels decreased largely. These decrease were especially remarkable at heating in a nitrogen atmosphere. These phenomena were attributed both to the grain growth resulting from diffusion of nitrogen into the steels and to the precipitation of AIN. In a heating at temperatures above 900°C, number of repeated bending decreased with shortening of the time of heating.
The electric resistance did not nearly vary with long time heating at high temperatures in vacuum and hydrogen atmosphere. But these values of Al-containing steels already decreased with elongation of the time of heating at temperatures above 800°C.
The grains of Al-containing steels with high value of an Al%:Cr% ratio begin to grow with elongation of the time of heating even at 700°C and grew remarkably at temperatures above 900°C even by a short time heating. Especially nitrogen promoted grain growth by its diffusion at high temperatures. When heated to above 1100°C, grain growth was so remarkable that we could not appreciate the influence of nitrogen upon the grain growth.

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Electric energy consumption of an Héroult type electric arc furnace was written in the form of the following polynomial, (as shown by "Tetsu to Hagane" Vol. 34, No. 9, 1948)
W=h₁M+h₂T+h₃
where W Electric energy cousumption
M Quantity charged
T Melting period
h₁ h₂ h₃ Constants
When we measure M, T and W, it will be easy to calculate h₁ h₂ and h₃. up to the present the author arranged the data by the aid of stochastics. How is it applied here, will be seen later.
1. The frequency distributions of W or T were collected and arranged. As the result, it was found that the distributions made a form just like a normal form of probability curve.
2. From the distribution diagrams of M, T and W shown as Table 2, 3 and 4, coefficients of simple correlation between them were calculated.
3. From the coefficients of simple correlation, the regression equation was deduced. This was the polynomial above mentioned. Thus the anthor showed an example of stochastics applied to the electric energy consumption of an Héroult type electric arc furnace, and described experimentally that the electric energy consumption varied in accordance with the above linear equation of quantity charged and melting period.

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Recently, although a large quantity of corrosion-resistance alloy is required for the chemical industry and others, the nickel production in this country is very poor at the present time. Therefore, the requirement of nickel always cannot be filled. To economize this material and to produce a lower-price stainless steel, the authors studied the method of manufacturing stainless clad plate and its qualities.
Base metal of stainless clad plate was mainly low carbon steel, and the clad metal was an 18% chromium and 8% nickel type austenitic stainless steel.
As the results of various tests, it was recognized as follows:
1. Of many manufacturing methods, both the casting method and the assembling method were the most suitable for mass-production because of easiness of working and the lowest cost.
2. In its manufacture, finishing of contact face in both metals, heating time or reduction ratio did not affect the adhesion strength of clad plate. For convenience of making, reduction ratio could be fixed properly.
3. The tensile strength of clad steel generally agrees with the value, calculated from the thickness ratio between clad metal and base metal layer. Nevertheless the endurance limit of a clad plate was far higher than the calculated limit.
4. The thermal conductibility of clad steel was considerably improved as compared with the mere stainless steel.

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Nitrogen and Hydrogen mixtures in ammonia synthesis industry attack steel at high pressures and moderate temperatures. Since a Claude plant applies the pressure and temperature higher than in other ammonia synthesis plants, and therefore catalyst container tubes used at Claude process is attacked specially by mixture of gases, sometimes serious failures may occur.
To obtain the low cost resistant steel for mixture of gases, the authors studied on the effect of hydrogen and nitrogen at pressure 800atm and temperature 600°C on various kinds of steel. the authors inserted the various kinds of steel in catalyst bed for 258 hours and exposed them to high pressure and tempratures. After exposure, the authors tested steel by various methods. From these tests, the authors could find the effect of mixture gases on steel as follows:-
1) In a Claude catalyst container tube, attacks of nitrogen were more severe than attacks of hydrogen for steel.
2) According as the position rises in tubes, nitrogen absorption of steel increases with concentration of synthetic ammonia
3) Chromium containing steel always cracked by mixture attacks of gas mixtures and this tendency increased with chromium percentage in steel.
4) Nickel was the usefull alloy element because of its crack-proof properties and others.
5) In every steel, low C content was desirable.
6) Titanium gave the resistance for decarburization in steel.
In tungusten steel no cracks occourred, moreover the absorption of both hydrogen and nitrogen gases decreased. For Claude plant steel, both elements were usefull.

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The author invetigated on the behaviour of arsenic in heating steel containing arsenic in the various atmosphere. The results obtained were as follows:
(1) Arsenic was concentrated on the surface under the scale in the oxidizing atmosphere.
(2) Arsenic was not concentrated in vacuum and in the reducing atmosphere.
(3) Concentration of arsenic was caused by selective oxidation on the steel surface.
(4) It was evidenced that the concentrated arsenic was chiefly Fe-As compounds by microscopic observation and chemical inspection.
(5) This concentrated arsenic gave the bad influence on finishing of steel.

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The outline of the total figure of the Fe-As-C system was investigated in the 1st report. (Lecture, 6th Subcommittee, Japan Inst. Metals, Nov. 1949) The authors continued the same experiments including the long time annealing as in the 1st report on many ternary alloys, determined the compositions and temperatures of the invarint points, solubility planes etc., and completed the Fe-As-C system. We also determined the γ roop, the solidus line of ferrite, the solubility limit of Fe₂As to ferrite etc. relating to the Fe-As system and compared these results with the former data reported by authors.

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Use of oxygen in electric arc furnace in the refining process for steel production was experimented in the United States through the years of 1930 to 1940, principally for recovery of chromium in the remelting process for low carbon high-alloyed stainless steel.
The experiment having been successful and the mass production of oxygen at low cost having become possible, the rage of application of the same gas to various types of electric furnace in the steel refining process was enlarged.
In Japan the research of oxygen application to electric furnaces was commenced belatedly as compared with that for application to open hearth furnace following the terminatin of the War, but the experiment has developed into the actual stage of use for production in a number of steel works.
Presently the object of oxygen application involves acceleration in the melt-down stage and bessemerizing in the steel bath. The benefits of oxygen application should be, therefore, considered from the viewpoint of material and power economy, operation efficiency and quality improvement.
This article dealt with the history and present condition of oxygen application to electric furnaces for steel production on the basis of a general conception gained from home and overseas reports and experiences in the authors' actual practice.

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