Nowadays interest is still being aroused in methods for direct reduction bypassing the blast furnace. In the previous literatures we can find some practical operating data on the direct reduction that makes use of a rotary kiln as reducing device, but scarcely any kinetic or analytical research on the process.
We have produced pig iron in a submerged type electric smelting furnace through halfreduced sponge iron which is obtained from iron sand in a rotary kiln since early 1956. Recently we constructed a 46m long kiln for various tests, equipped with 6 sampling holes for different purposes. By this equipment we tried to make an overall measurement of the reducing kiln.
The measurement of the rotary kiln was made on the following items:
(1) Temperature of raw material at 7 points along the axis of kiln.
(2) Spot sampling of material at the same points and its chemical analysis.
(3) Spot sampling of atmospheric gas at the same points and its chemical analysis.
(4) Temperature of iron shell and others.
We obtained some results after several measurements and analysis on the operating kiln, especially suggested the importance of abnormal phenomenon i. e., segregation of raw material in the rotary kiln, which has influence on the reducing reaction and others.
In this paper we show the dimensions of the test kiln, equipments and methods for measuring, and then present the results of measurements.

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The partial pressure of oxygen of 10^-1 down to 10^-20 atm. in carbon monoxide-carbon dioxide and argon-oxygen mixtures has been measured at temperatures of 800°C, 900°C, 1000 and 1200°C by an oxygen concentration cell method with a solid electrolyte, ZrO₂-CaO, which provides pure oxygen anion conduction due to oxygen vacancies at high temperatures.
The cells employed are shown below:
(1) CO.ECO₂: FeO-Pt|ZrO₂-CaO|FeO-Fe|Pt
(2) CO.ECO₂: Pt|ZrO₂-CaO|NiO-Ni|Pt
(3) CO.ECO₂: FeO-Pt|ZrO₂-CaO|Cu2O-Cu|Pt
(4) Air or Ar-O₂ : Pt|ZrO₂-CaO|NiO-Ni|Pt
It was shown that this method is very convenient in analyzing directly the gas composition of CO and CO₂, or Ar and O₂ at the elevated temperatures as well as of other gas mixtures.
Calibration curves of EMF against gas composition are presented. The expected advantages and disadvantages in the case of industrial application are also discussed.

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During the heating process thermal stress arises in the steel ingot because of two main causes; i. e. the temperature difference within the ingot and the volume change caused by the transformation.
In this report author tried to relate theoretically the method of calculating the thermal stress under high temperature. As the deformation under high temperature is accompanied by not only elastic strain but plastic strain also, it is very difficult to determine the thermal stress. Here the author denotes the deformation in elastic-plastic range by a nonlinear integral equations and by introducing the conception of equivalent total strain he calculates the stress and the plastic strain through a comparatively easy successive integration.
For the calculation of the stress during transformation range the author regards the curve of the expansion values as three straight lines and these three lines denote the three stages of transformation i. e. the pre-, mid- and post-transformation stage and so he makes calculation according to these three stages. And he calculates the stress and plastic strain which occur when the transformation progresses from the surface to the core.
Two calculated examples are shown of high-carbon-chromium steel circular ingots at two stages; one is where the ingot is undergoing the transformation and the other is where the ingot has no relation with transformation.
The following facts have been discovered by this theoretical calculation;
(1) As for the stress distribution there is compression stress (σ_r=0, σ_t=σ_z) in the outer part of the ingot and tension stress (σ_z≅2σ_r=2σ_t) near its core and the stress is greatest at the core in the heating process, because of high surface temperature.
(2) During the transformation the tension stress which has been greatest at the core decreases in accordance with the progress of transformation for the time, but from the beginning of transformation of the core till its completion there occurs a violent increase of the stress and plastic strain and the elastic stress becomes the greatest of all the stages.
So if some crackings take place in this case, it can be inferred that discus-form crackings will occur normal to the axis near the core when the core completes the transformation.

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In the 1st report, the influence of inclusions on the formability of a rimmed steel sheet was studied, and it was shown that the formability of a steel sheet was injured by a large sulphide existing in the position correspond to the segregated zone in the ingot top.
In this report, in order to making clear the origin of such inclusions and how to eliminate them, the shapes, distribution and deformation of inclusions at the segregated zone in the ingot top during slabbing were observed: Moreover, author studied the influence of refining and deoxidation process on the cleanliness of the segregated zone. The conclusions of 1st and 2nd report were as follows:
1) In the segregated zone at the ingot top, the network ofthe large flaked type sulphide rich in FeS is found.
It was considered that these inclusions suffer a few fractures during rolling process, for they change from FeS to MnS by soaking and reheating. Those large sulphides injured the formability of the steel sheet.
2) The cleanliness of ingot top is closely connected with the segregation and it is mainly influenced by the [S] and [O] in ladle.
3) In order to decrease the large sulphide mentioned in 1st report, the S-content in the segregated zone should be kept under 0.10% in the check analysis of slab, as the ladle [Mn] is about 0.30%.

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The form, shape and hardness of martensite structure transformed from strained austenite were investigated for an Fe-31.7%Ni alloy in order to make clear the strengthening mechanism of steel by ausforming treatment. From the results of hardening characteristics of martensite plates and of the change in X-ray diffraction lines from martensite and austenite due to deformation before transformation to martensite and also microscopic observation of the structure, it was confirmed that a strengthening. by ausforming could be attributed to both the refinement of martensite structure and the change in the internal strain of martensite induced by austenite deformation prior to transformation.
The study was also extended to the determination of the influence of applied stress on martensite transformation. Ms was raised by tensile stress at the rate of 1.6.. /kg/mm² in the temperature range between -45.. and -30.. and at 0.16.. /kg/mm² in the temperature range between -51.. and -45... It was found that the rate of 1.6.. /kg/mm² showed good agreement with the result obtained from the calculation of stress dependence on Ms by Cohen's treatment. A discussion was also made to estimate the relation between the energy to initiate martensite transformation and the energy to deform the material under an applied stress.

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The depleted uranium as a by-product of the enriched uranium manufacturing has been accumulated enormously in these several years, since it is unfit for nuclear uses. For the purpose of utilization of depleted uranium for non-nuclear uses, a large number of studies. concerning the effect of uranium addition on iron and steel have been made in the United States and Canada.
Here, in Japan, in 1961, “The Special Committee for the Study of Uranium Steels”, has; been organized in “The Japan Society for the Promotion of Science” so that industrial and. research fields miy share stuiies systematically from the basic researches to the practical applications.
In this paper, a laboratory study to reveal the principal effects of uranium addition to steel: as an alloying element has been carried out. The aluminum-killed low carbon steels (<0.25. %C) are chosen as the object of study on addition of small amountof uranium (<0.7%U).
The results are as follows:
(1) Recoveries of uranium from steels are 40 to 65% and related, ingeneral, with the: carbon contents as shown in Fig. 1.
(2) Non-metallic inclusions like sulfides and silicates decreased morphologically with uranium addition, but oxide inclusions increased remarkably.
(3) Uranium refined the austenitic grain size of steels slightly.
(4) As-normalized hardness suffered a little effect of uranium addition at a 0.06%C leveL but above a 0.16%C level the effect increased with the content of uranium.
(5) After water-quenching from a solution temperature ranging 950.. to 1250.. in 0.06, %C steels, secondary hardening occurred under the tempering up to 600... Microscopic exa mination showed that uranium caused pseudo-martensitic structure, and it also suggested that uranium had a solubility to austenite matrix to some extent.
(6) After water-quenching from a ferrite region ranging 750 to 800.., no ageing occurred at room temperature and at 150... It was suggested that uranium hadnot the slightest solubility to ferrite matrix.
(7) It appeared from the end-quench tests that the hardenability of steel did not risewith uranium addition from a quenching temperature of up to 900.., butabove 950.., uranium raised the hardenability of steels. So in low carbon steels, uranium formed the _intermetallic compound Fe₂U. And it is considered that Fe₂U decomposed above 950.., uranium had a solubility to austenite and had its hardenability improved, as mentioned above.
(8) Mechanical properties at room temperature were not affected by uranium addition, but impact strength decreased with the content of uranium.
(9) Transformation points of steels rose with uranium addition because of the stabiliza tion of carbon from austenite matrix.
(10) Uranium did not affect the work-hardening effect and since uranium fixed the interstitial atom like carbon and nitrogen, strain-ageing did not occur in silicon-killed uranium steel.
(11) Corrosion resistance against 5% hydrochloric acid improved with an addition of uranium as shown in Canada's report but in 5% sulfuric acid severe pitting occurred, and in 3% nitric acid no beneficial effect was observed.

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An 80kg/mm2 high tensile steel with a low carbon equivalent value and difficult to harden by quenching was tempered after water-quenching or transformed isothermally and the mechanical properties and the internal friction were measured. The internal friction at room temperature was calculated from the time during which the strain amplitude of the sample set free after being subjected to a transversal resonance vibration by the electromagnetic method decreased to 1/n of the initial value.
The experimental results are as follows:
(1) The sample quenched in water has a low strain amplitude-dependent internal friction and shows a low quenchability.
(2) The strain amplitude-independent internal friction of the specimen quenched in water from 900.. decreases remarkably by tempering in the temperature range from 20.. to 200.., shows litte change in the range from 300.. to 500.., and increases in the range from 550.. to 700... These changes correspond to the changes in the Charpy impact value. The three stages in the variation of internal friction are interpreted respectively as due to the precipitation of carbides from martensite, the decomposition of martensite and the formation of carbides.
(3) The transition temperature rise by tempering in the temperature range between 300.. and 500.., reaches a minimum after tempering at 700... The transition temperature is influenced by the form and distribution of carbides.
(4) The sample transformed isothermally has a strain amplitude-dependent internal friction.

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The effect of nitrogen addition to 25%Cr-28%Ni austenitic heat-resisting steels prepared by the high-pressure melting process in nitrogen atmosphere on both microstructures and mechanical properties at room- and high-temperatures was studied. The influence of replacing a part of nickel by cobalt in those steels was also examined. Main results obtained were as follows:
(1) It was necessary to heat for 1h at 1250.. for the solution treatment of the steels with high nitrogen content.
(2) The recrystallization temperature estimated from the hardness change during tempering of cold rolled specimens was found to be higher by about 100.. in the 0.54%N steel than in the 0.05%N steel, and the temperature of the former steel decreased with the replacement of a part of nickel by cobalt.
(3) It was observed from microstructural changes during ageing at high temperatures of the steels with high nitrogen concentration that the precipitation of nitride Cr₂N from the austenite proceeds in the following two different modes: one so-called general precipitation and the other a grain boundary reaction. The latter mode of reaction, which proceeds rapidly by consuming the nitride particles formerly precipitated by the mode of the general precipitaion, was found to be brought to a stop when the reaction covers about a half of the area under the microscope of the solution treated steels, whereas it was found to proceed until the reaction covers almost all of the structure in the cold-rolled steels.
(4) Proof stress and tensile strength of the steels at room-temperature increased markedly with an increasing concentration of nitrogen without any loss in ductility. At high-temperatures, the tensile strength increased with an increasing concentration of nitrogen, the ductility being deteriorated considerably.
(5) It was found from the tensile creep-rupture test at 700.. that the increase in creeprupture strength of the steels with an addition of nitrogen only was not so large as in the high-nitrogen 316L type steels, and that the creep-rupture properties of such steels were somewhat improved by cold-working, hot-cold working or ageing treatment at 800.. of the solution treated steels. It is expected that those properties may be improved considerably by a simultaneous addition of nitrogen and molybdenum, or nitrogen and niobium.

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In the present study, the following points were clarified with regard to the quenching effects of the blended oil, composed with fatty oil having large molecular weight and fatty acid ester having 20 carbon atoms:
(1) The mixture containing ester up to 90% in volume has a more remarkable quenching effect than the fatty oil used. The quenching effect is the larger with the more ester concentration.
(2) When the mixture contains ester over 90% in volume, its quenching effect becomes the less with the greater ester concentration. For carbon steel, having low hardenability, the above quenching effect is less than that of the fatty oil used.
(3) Under constant blending ratio, the quenching effect of the mixture is the larger with the greater molecular weight of the fatty oil, the larger polarity of the fatty acid ester and the lower boiling point of ester.
(4) The blended oil containing castor oil, generally, has a more remarkable quenching effect than other oil mixtures. It may depend on the thermal instability of castor oil. (5) The phenomena observed during quenching using fatty oil, fatty acid ethyl ester or fatty acid individually differ greatly from those observed in a blended oil of these ingredients.

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