There are ever so many representation methods of austenite grains, but they have, in general, some limitation when applied to practical use in some or other cases of chemical compositions of steel. Moreover, there was no trustworthy and versatile method of invesitgating the behavior of grains at high temperature where their actions are very remarkable. The method described here is, however, versatile enough to be used in this field of science. When the specimen is kept in inert atmosphere of high temperature, corrosion by evaporation will be noticed most conspicuously at the grain boundaries, and owing to the evaporation and rearrangement of grain surface atoms, surfaces characteristic of and inherent to crystal will be exposed. Each surface has a fixed resistance to the oxidation according to its orientation, respectively, so that when oxydized by a small quantity of oxygen the surfaces take various colors of their own. By using this method we have the advantage of observing austenite grains treated at an arbitrary temperature and duration. The present authors studied the behavior of the growth of low carbon steel grains by means of this method and noticed the pronounced correlation between the coarsening of fine grains of Al-killed steel and the solubility of AlN into γ-iron.

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In this experiment the impact fractures of mild steel, high carbon steel and Ni-Cr steel were studied by electron microscopy. The impact fractures of mild steel were observed in the temperature range from −70° to 350°. At low temperature, the fracture surfaces are very flat and are divided into domains of large sige comparable to that of crystal grain size. In the temperature range from 100° to 250° the fracture surfaces exhibit very ductile behavior similar to that of pure iron. Above this temperature range the impact values slightly decrease and the domains in fracture surfaces become smaller and many small steps are sometimes seen. In the case of a quenched state of high crabon steel or Ni-Cr steel, fracture surfaces exhibit a very flat and small ductile deformation. And the domains in fracture surfaces are very large. Fracture surfaces of tempered Ni-Cr steel present very different aspects depending on the cooling velocity after tempering. That is the samples water-cooled after tempering show the familier ductile deformation, but those furnace-cooled after tempering show small ductility and stepwise deformation.

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During and after the war, great attention has been directed to the high carbon and high vanadium types on the high speed steel. These types of high speed steel offer advantages because of their greatly increased resistance to wear, but little has been reported on the detailed relations between their compositions and their properties. It is the object of this survey to elucidate these relations in this new type of high speed steel. For this purpose, laboratory tests on heat treatment, hot hardness, impact properties and cutting power have been carried out. The carbon and vanadium contents being higher than normal, resulting in a decreased amount of matrix carbon and in an increased amount of complex carbide, they are easy to forge and heat treat. And as a result of this experiment, specimens containing 1.4%C, 5∼10%W, 4%Cr, 5.5%V have been found to have the highest properties as tool steel, especially for fine drills.

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The impact value and the wear resistance of hardened high speed steel (18-4-1 type) was measured by the Sharpy Impact Tester and the Skoda Wear Testing Machine. The heat treatment of the specimen was oil quenching, tempering subzero treatment, austempering martempering and alternate repetition of tempering and subzero treatment. The wear resistance and the impact value was improved by the heat treatment which consists of tempering and subzero treatment after quenching in heated oil.

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In the previous report, (N.K.G. Vol. 16 (1952) p. 328) the authors concluded that the super-cooled austenite of high speed steel precipitates carbides prior to γ→α transformation. The present report is on the experimental results and discussions on the actual influences of such carbide precipitation on the properties of hardened high speed steel. A sample is austenitized at 1300° and quenched in a metal bath of 600°, kept in the bath for a duration of time and then quenched in oil. Such specially quenched specimen contains no residual austenite, and in tempering shows no secondary hardening. The causes of these differences of properties, between the samples which were normally quenched and specially quenched, were studied by the usual metallurgical methods.

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The graphitization of high carbon steel containing different contents of Si was studied by dilatation test, chemical analysis and microscopic examination. The effects of Si on deoxidizing and denitriding were determined from the result of gas analysis. When more than 0.6% of Si is contained the graphitization phenomena became remarkable, showing two stage during the cooling. Especially, graphitization of the specimen contating 1.3% of Si began from about 600°C in heating, but in the other specimens it was not observable. As to the relation between graphite and Si contents, it was found that the maximum and minimum values were respectively at 0.15% and 0.7% of Si when annealed at comparatively low temperature. The minimum point mentioned above changed to the low Si side and graphite increased in proportion to Si content when annealed at higher temperature.

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Oxide powders of Fe, Ni, Co and Fe-Co, prepared from their oxalates, formates or carbonyl compounds, were reduced in a hydrogen stream of 400 cc/min. After cooling, the powders were pressed into a cylindrical form under the pressure of 5 ton/cm² and their magnetic properties were observed. The most suitable reducing temperatures for iron formate, nickel corbonyl and cobalt formate were found to be 400°, 320° and 450° respectively. The coercive force of Fe compact, thus prepared, was the largest and that of Ni the smallest. The values found in the present experiment were compared with the values obtained by the theoretical formulae hitherto reported. In order to obtain a high coercive force by the reduction method, fine and needle-shape oxide powder may be desirable as the starting material.

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The so-called 475°-embrittlement in high chromium ferritic stainless steels has long been discussed by many investigators, but its cause, is not yet elucidated at all. Recently. S. Takeda and N. Nagai, one of the present authors, reported that this embrittlement was due to the formation of one of the super-lattices, Fe₃Cr(α′_3-1), FeCr(α′_1-1) and FeCr₃(α′_1-3) by them, according to the composition of alloys. In this paper, the present authors carried out a systematic research on the cause of the so-called 475°-embrittlement in four kinds of Fe-Cr-Al electric resistance wire alloys, by means of microscopic observation, magnetic and dilatometric analyses, as well as measurements of specific heat at elevated temperatures, hardness, electric resistance and intensity of magnetization at room temperature, through which it was proved that this embrittlement was also attributed to the formation of Fe₃Cr(α′_3-1), one of the super-lattices in Fe-Cr system, as in the case of high chromium stainless steels.

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By means of consumable double melting method we produced a titanium ingot containing about 2% each of iron and aluminium, whose structure is uniform and sound. As to mechanical properties, its tensile strength and elongation are about 90 kg/mm² and 20% at room temperature, respectively, and consequently this product shows a satisfactory result as high tensile alloy. Its tensile strength and elongation at 600° rise to 30 kg/mm² and 30%,respectively, and at moderate temperature it shows excellent heat resistance.
As to workability, it is easily subjected to hot forging and rolling. Furthermore, even in the case of 50% reduction by cold rolling it can obtain the tensile strength of 130 kg/mm², and in the case of reduction up to 80% by cold drawing the tensile strength becomes 150 kg/mm². With regard to heat treatment property, it shows a structure of α+β at room temperature, and in the case of water quenching from the temperature of 1,000° it shows the structure of α′. As a result of isothermal transformation test at the temperature ranging from 400° to 950°, α structure appears in the quanching structure, while in quench aging test an unknown precipitation appears in the structure at the temperature of about 500°.

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The corrosion rate of copper alloys by dilute aqueous solutions of sulfuric acid has been measured. The corrosion rate increases nearely in proportion to relative velocity in the range of low speed, but it becomes gradually constant as the velocity increases. The higher the concentration of hydrogen ions, the larger the corrosion rate. The corrosion is mainly controlled by the diffusion and the adsorption of dissolved oxygen on the copper alloys.

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Determination of hydrogen, oxygen and nitrogen in metallic titanium were studied by the vacuum fusion method and the chlorine method. In the vacuum fusion method, hydrogen and oxygen were completely extracted and could be determined at 1850∼1900° by using iron bath, but nitrogen was not extracted. Then, in the chlorine method, oxygen could be determied by chlorination at 300° in a stream of mixed gases of chlorine at 5 mL/min and nitrogen at 20∼30 mL/min.

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The measurements of the attenuation of longitudinal ultrasonic waves was carried out in gray cast iron. The specimenes contained 3.4∼3.6 percent of carbon and 1.8∼2.2 percent of silicon, and the size of flake graphite was distributed between 0.05 and 0.5 mm. The measured value of attenuation was about 0.2 db/cm at 0.5 Mc/s and showed a remarkable increase with the frequency, and this rate of increase rose with the size of flake graphite. It has been concluded that the attenuation mentioned above is due to the scattering of ultrasonic waves by elastically anisotropic pearlite grains, which are separated by flake graphites and have a size comparable with the wave length of sound. The elastic anisotropy of pearlite grain in cast iron has been estimated on the basis of this conclusion, and the value coincides satisfactorily with that in hypoeutectoid steel.

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A statistical treatment of the anisotropic distribution of atom pairs responsible for the additional magnetic anisotropy in field-cooled or cold-worked ferromagnetic solid solutions as well as for the internal friction of the α-brass type is developed in connection with ordinary order-disorder phenomenon. A characteristic tensor, Γ, is defined, of which the diagonal sum is proportional to Bethe’s short-range order parameter and the principal values and directions of principal axes describe the anisotropic distribution of atom pairs. The energy of external force (stress or magnetic interaction of atoms in the ferromagnetic case) can be expressed in terms of Γ. The configurational entropy of atom pairs is evaluated by Takagi’s method. A long-range order parameter and Γ are calculated for the body-centered case under the condition that the effect of the external force is small compared with the ordering energy. The calculation clarifies the behavior of the anisotropic distribution of atom pairs at fixed concentrations or at constant temperatures, especially the way of abrupt diminution of it with the superlattice formation, and the dependency of the anisotropic distribution on the direction of external force. Finally, it is shown that the additional magnetic anisotropy in ferromagnetics has an orthorhombic symmetry and the three anisotropy constants are proportional to the principal values of Γ.

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Single crystals of 13 kinds of Ni-Cu alloys were prepared by the Bridgman method of slow solidification. The test specimens were square rods 1∼2 mm in width and in thickness and 3∼5 cm in length. The measurements of Young’s moduli were performed at room temperature by the new microscopic method. From the obtained Young’s moduli of some specimens of the same composition having arbitrary directions, the Young’s moduli for the principal crystal directions were derived. The Young’s modulus of [100] direction E_[100] decreases at first upon addition of Cu to Ni, reaches the minimun at about 10, the maximum at about 25%Cu, and then it decreases with further increasing Cu. The behavior of the Young’s modulus of [100] direction E_[110] is similar to that of E_[100], but the Young’s modulus of [111] direction E_[111] decreases monotonously. The three principal elastic coefficients S₁₁, S₁₂ and S₄₄ were determined by using the known data of compressibility for polycrystals of Ni, Cu and a Ni-Cu alloy containing 45%Cu. Futhermore the principal rigidity moduli were derived.

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Alpha brass hardens when it is annealed at low temperatures below recrystallization temperature after cold-working. This phenomenon will be called “anneal-hardening”. A theory was proposed to explain it. The outline of the theory is as follows. (1) Concentration of zinc atoms increases at the stacking faults of extended dislocatior which were newly formed by cold-working. The increase of zinc concentration is caused by H. Suzuki’s chemical interaction between extended dislocation and solute atoms. The increased zinc atoms form the nuclei of Guinier-Preston zones. (2) The nuclei grow to become Guinier-Preston zones, which cause the anneal-hardening of the alloy. Various phenomena accompanying the anneal-hardening are well explained by this theory. It is likely that the alpha phase forms a short range order. It seems, however, the ordering does hardly contribute to the hardening of this alloy. In the above discussion, the alpha phase solubility curve of Shinoda and Amano (Figs. 3 and 4) was used. In this diagram the solubility limit is very much reduced compared with the oldar ones.

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The adsorption of boron and other interstitial solute elements in the quenched state could be made well observable by etching the steel with aqueous solution of NaOH-NaNO₃. Boron atoms adsorbed on a grain surface fill up the lattice defects or diffusion holes, reducing the internal strains induced by these imperfections; in other words, these atoms diminish the unstability of austenite grain boundaries and can suppress the transformations beginning there.

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Through an electron-microscopic examination we studied the condition of a supersaturated solid solution of a copper alloy containing 2.2 per cent nickel and 0.7 per cent silicon. We also investigated the process of aging of the alloy by measuring the changes in its hardness, the electrical conductivity and the X-ray diffraction. We quenched all the test-pieces (of Groups A and B) in water from 950°, and then tempered them in the following manner:
The test-pieces of Group A were tempered at 30∼750° for 60 minutes. Those of Group B were similarly tempered after cold-drawing (Reduction in area: 78 per cent). After polishing the pieces of both the groups mechanically or electrolytically, we etched them in a 10 per cent aqueous solution of (NH₄)₂ S₂O₈. The results of our electron-microscopic examination made by the two-stage replica method (polystyrene-chromium film) were as follows: (1) In the initial stage of increase in hardness and electrical conductivity of the Group B test-pieces, which occurred at the time of tempering, precipitates were observable only within the crystal grain boundaries; but, in the stage where their hardness and conductivity reached the maximum, the precipitates were visible not only within the crystal grain boundaries, but also inside the crystal grains prior to recrystallization (See Figures 1 and Photographs 2 and 5). Therefore we consider that the increase in hardness and electrical conductivity of the test-pieces resulting from tempering was ascribable to precipitation. We observed that the precipitates formed within the crystal grain boundaries were relatively large-grained, while those formed inside the crystal grains were extremely small-grained and almost reticulate. From the foregoing we infer that the precipitation of the alloy under notice occurs chiefly in the course of polygonization. (2) No precipitate was visible in the twin-boundary of any of the test-pieces of Group A or B. (3) The precipitates of the Group B test-pieces were larger in granular size than those of the Group A test-pieces,and the former were also larger in quantity than the latter. The tempering temperature, at which the Group B test-pieces showed the maximum hardness and electrical conductivity, was about 50° lower than that in the case of the Group A pieces. From the above we consider that the precipitation of the supersaturated solid solution is promoted by its strain before agling. (4) We observed that the nuclei of the recrystallization within the crystal grains tend to start forming themselves chiefly in the vicinity of massed preciptates. (5) All the precipitates appeared to be in the shape of a complicated polyhedron or granule, rendering it impossible for us to know their exact shape.

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To explain the so far obtained experimental results concerning the thermodynamical properties of binary alloys during fusion, the entropy of fusion of binary alloy is investigated starting from a thermodynamical theory of phase diagram⁽¹⁾. Especially, the effects of mixing of vacancies, of the short-range ordering and of the change of atomic vibrations due to alloying in solid or in liquid are discussed, and compared with some experimental results. Mixing of interstitial type is argued too. Good agreement between the theory and observations is indicated and some predictions are made.

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The magnetic susceptibility of crystalline tellurium, in the range between ambient and liquid air temperatures, has been measured by means of the Sucksmith’s ring balance, and the magnetic anisotropy of a single crystal of tellurium has also been studied by the torsion magnetometer method in the same temperature range. The susceptibility of purest crystalline tellurium is diamagnetic, being appraised at−0.301×10⁻⁶ c.g.s.e.m.u. per gr, and remains constant from room temperature down to liquid air temperature. A single crystal, however, shows the difference in the susceptibility between the directions perpendicular and parallel to the principal hexagonal axis, that is to say, Δχ=χ_⊥−χ_\varparallel amounts to 0.458×10⁻⁸ at 78°K and rises linearly to 0.717×10⁻⁸ at 295°K. Whence it follows that the magnetic anisotropy, χ_\varparallel⁄χ_⊥, is evaluated to be 1.015 at 78°K and 1.024 at 295°K.

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With the object of elucidating the cause of Perminvar characteristics of the “Senperm” alloys containing 14∼18%Ni, 8∼12%Si and the remainder Fe, which was discovered by T. Yamamoto about ten years ago, the constitutions of alloys containing 15 at%Ni and 5∼25 at%Si were investigated by means of microscopic observation magnetic and dilatometric analyses as well as measurements of electric resistance and intensity of magnetization, through which the sectional diagram of 15 at%Ni was determined. There exists no superlattice as inferred by T. Yamamoto, but a ferromagnetic ternary compound named the σ-phase by the authors precipitating from the α-phase is formed. Measuring the B-H curves of several alloys under various heat-treatments with ballistic galvanometer method, it was also found that the striking Perminvar characteristics was obtained when the σ-phase was precipitated in dispersed state, through furnace cooling from about 900°. Considering these results, the Perminvar characteristics of the “Senperm” alloys was attributed to some dispersed precipitation of the σ-phase in the matrix of the α-phase.

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It is shown that the ferromagnetic uniaxial anisotropy induced by magnetic annealing in solid solutions can be explained by the anisotropic coupling between atom pairs caused by the interplay between spin-orbit coupling and orbital valence. When the ferromagnetic solid solutions are annealed in the absence of magnetic field, every domain wall is stabilized by this induced uniaxial anisotropy, which leads to the perminvar character. The change of magnetization curves due to heat-treatments in various alloys can be interpreted in terms of these ideas.

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An apparatus for precise measurement of magnetostriction at high temperatures has been constructed, by which the magnetostriction and its relaxation under a constant magnetic field applied at high temperatures has been measured with 7 γ-phase nickel-cobalt alloys thermaly demagnetized. The magnetization and the magnetosriction at room temperature have also been measured with the alloys annealed in magnetic field. The change of magnetostriction of the alloys in the lapse of time was not observable at temperatures below about 350°, but it showed a very remarkable increase at temperatures above about 350°, the amount of the change of magnetostriction for 1 hr showed a rapid increase at about 450° with a rise of temperature, and it eventually almost vanished near the curie temperature. It seems that the effect of magnetic annealing on the magnetic properties of Ni-Co alloys is in close connection with the micro-creep due to magnetostriction at high temperatures.

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The aging characteristics of various alloys are interpreted satisfactorily from the unified standpoint of view that the formation of the Guinier-Preston (G-P) zone or “Complex” which is a segregation of the solute stoms on the matrix lattice is not a preparative process of precipitation of the new phase. Supersaturation of the solid solution is not necessarily required for the formation of the G-P zone, if the concentration of the solute atoms in the matrix solid solution is suitable. Taking into account the stability of the G-P zone as a function of the concentration of the solute atoms and considering the incubation periods of the formation of the G-P zone and of the precipitation of the new phase, the aging process and the effects of the additional elements and cold working to the aging characteristics are explained. The results of the calorimetric, electrical resistance and X-ray measurements on Al-Cu, Al-Ag, Mg-Pb, Al-Al₂Mg₃Zn₃, Al-MgZn₂ etc. are referred to for the discussions.

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The present author tried to detect and succeeded in determening the actual deflection phenomena of a rotary bending test piece by means of the so-called air condnser method. Namely, the distance between a rotating bending piece and a fixed plate, which is not constant under a constant loading, was made clear at any instant by application of the so-called modulation method of a high frequency circuit connected to the gap (namely, equivalent to the deflection of the test piece) of the air condenser. Results thus obtained give us a clear idea that a rotary bending fatigue specimen under a constant loading do not show uniform constant deflection around the circumference of the piece as it is usually supposed to occur, but always show non-uniform deflection, which also is of a completely cyclic state just the same as the cycle of the rotary piece. These results give us a new foundation to the idea that, a direct measurement about deflection of a rotary bending piece could,at any instant of its rotation, be obtained using a reading microscope, if we would observe under a strobo-glow lamp illumination excited by a circuit of the same cycle as the rotary piece. By this new method, observations of the deflection of a rotary piece were carried out; these observations were easily made as a simple statical measurement. Also, by a successive change of the phase of the strobo (neon) lamp illumination by a cam apparatus, the deflection at various phases of rotation of a rotary piece was equally measured; thus the distribution of deflection around the circumference of the piece could easily be determined. These results will give a new information about the actual features of an actual fatigue fracture. Moreover, by this author’s new method, deflection phenomena which may be brought about by the effect of the speed of the load application and of the shape of the notch of a fatigue specimen (i.e. actual fatigue resisting strenth) may equally be traced by the results of this same measurement.

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The change of microscopic structure of a polished surface of steel during gas carburization was observed. The results obtained were as follows: (1) By gas carburization, grain boundaries on the polished surface of steel appeared even in 30 seconds at the temperature as low as 650° and new grains began to grow. (2) The carbon content of the surface reached the near eutectoid composition quickly, and it increased gradurally up to the saturated concentration of austenite.

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Generally, it is most difficult to preserve fine metallic particles completely from oxidation in several practical processes of powder metallurgy. e.g., keeping, compacting and mixing. Therefore, it seems the more improtant to investigate the influence of the film formed by oxidation on the sintering rate, but this problem has not yet been set tled experimentally. In this report, the accelerating effct on the sintering rate was studied by heating one layer of pre-oxidized spherical copper particles arranged on a silicate in reducing atmosphere under various conditions, from the viewpoint of morphology. The main results were as follows: (a) In hydrogen atmosphere, the sintering began at far lower temperature and the thickness of the sintered bond increases to several times, as compared with the results in normal sintering process under similar condition. (b) In the reducing process, it is natural that many ultra-fine particles be formed on the surface of the original particles. These fine particles are sintered more easily and rapidly owing to their large surface energy. (c) However, if the oxide film is too thick, groups of the reduced fine particles tend to separate from the original particles, by the individual shrinking of the former particles, so that gaps are formed between the reduced layer and the original particles. Consequently, previous oxidation at a higher temperature over ca. 500° is undesirable. Indeed, for assuring better effect, case must be taken to effect the previous oxidation at low temprature and do the heating slowly.

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The authors have analysed the effects of the ratio of electrode areas and resistance of circuit on corrosion current of zinc in a zinc-mild steel corrosion couple and expressed the corrosion current as a function of the ratio of electrode areas, polarization, radii of anode and cathode plates, specific resistance of solution and potential difference between the two electrodes. Employing this function they have interpreted the reason why the observed values of corrosion current of zinc in Na₂CO₃ solutions (pH 7∼12.5, 30°) undergo changes as the pH values of the solutions vary.

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In continuation of the works previously reported on Fe-Cr alloys and Fe-Ni alloys, the anodic polarization of Fe-Mo alloys has now been investigated. We have found the following results. (1) Active Fe-Mo alloys containing molybdenum in solid solution show the same degree of polarization as pure iron, but the critical current density at which the anodic passivity is attained is higher the greater the molybdenum content of alloys. Then, with Fe-Mo alloys (iron-rich solid, solution) in sulphuric acid solution, anodic passivity becomes decreasingly attainable as the molybdenum content in alloy increases. (2) In the polarization of two phase alloys containing more than 10%Mo two stages are distinguished: the dissolution of the α-phase and the dissolution of the intermetallic compound Fe₃Mo₂. (3) By anodic dissolution Fe₃Mo₂ or alloys containing more molybdenum acquire a protective layer of molybdenlum blue, resulting in mechanical passivity. (4) The electrode potentials of Fe-Mo alloys were measured and the results obtained are shown in Fig. 6.

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Les auteurs ont ètudié, en partant des films minces du titan vaporisé sous vide sur le plan de clivage du sel-gemme, les structures cristallines du Ti-α, des oxides du titan et spécialement leurs orientations relatives.
(1) Par le chauffage à 500°, quelques minutes dans le vide, le film du Ti-α donne le TiO et dans I’air ou dans le CO, il donne le TiO₂ (rutile et octahédrite) (2) On obtient le film du Ti-α monocristallin en chauffant le sel-gamme à 460∼530°. (3) Les orientations relativet sont:
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(4) On obtient facilement le TiO₂ mais principalement le rutile et un peu d’octahédrite. On n’observe pas de Ti₂O₃.

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The iron and oxygen atom-ratios of Fe-O melts are continuously variable by the change of oxygen pressure in gaseous phase. It is very reasonable that we suppose Fe-O melts are constructed by ionic components Fe⁺⁺, Fe⁺⁺⁺ and O⁻⁻, thanks to the knowledges on Fe-O solid-solution phases (ref. 5th and 9th Reports) and the electro-conductivity of melts. We assume the following configurational model for Fe-O molten system: (1) Oxygen ions O⁻⁻ are arranged on the face-centered cubic lattice (nearly close-packed), because they are very large compared with iron ions. (2) Fe⁺⁺ ions are distributed on the tetrahedral and octahedral interstitial lattice points of oxygen ion lattice. (3) If any tetrahedral lattice point is occupied by a iron ion, its nearest octahedral lattice points are vacant, and it is the same for the nearest neighbors of octahedral iron ions. (4) Positive holes are randomly distributed on Fe⁺⁺ ions, and thus Fe⁺⁺⁺ ions are formed. Using the above model the partition function of the Fe-O molten slag was formulated by the statistical thermodynamics, and the equilibrium relation between the slag composition and the pressure of oxygen in gas phase was calculated. This theoretical results are in good ageement with the measured values of Darken and Gurry (1946) in the wide range of pressure, 10⁻¹⁰ to 1 atm of O₂, and temperature 1400° to 1600°.

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The rate of the transfer of sulphur across a slag-metal interface was studied at the temperature range from 1440° to 1570°C. Radioactive sulphur, S³⁵, was used to improve the accuracy of the experiment. The net rate of transfer of sulphur from metal to slag increases with increasing basicity of the slag and with rising of temperature. This is ascribed to the fact that the rate of transfer of sulphur from metal to slag increases rapidly with increasing basicity of slag and with rising of temperature, while that from slag to metal does not change appreciably with changes in slag composition and temperature. In the case of high viscosity slags, the rate of the transfer of sulphur was interpreted by the assumption that the transfer is a reaction of the first order, but this assumption was inadequate for the experimental results on low viscosity slags.The rate of the transfer of sulphur seems to be affected remarkably by side reaction.

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A new method of an extremely efficient process of purification of metals and metaloids, called normal segregation or zone melting, has been developed in recent few years and its principle and practical application chiefly on semiconductors have been reported by a number of investigators. But very few experiments have been carried out on common metals. The purpose of the present paper is to deduce a fundamental data of normal segregation on ordinary alloys, such as Cu-Sn and Cu-Ni systems. The former has a segregation coefficient smaller than 1 (0.09∼0.2) and the latter greater than 1 (2.1∼2.7). The results obtained are shown in Figs. 3∼8, comparing the experimental data with the theoretical formula given by W. G. Pfann. As can be seen in these figures, the freezing rate of alloys remarkably influences the purification degree, resulting in a great deviation of experimental plots from the theoretical curve.

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A method was completed for recording the rapid cooling rate in quenching steels by means of an oscillograph, operated by a thermocouple e.m.f. through a cascade connected with a 3-stage amplifier. The complete assembly includes a quenching tank, a gas quenching unit, a thermocouple amplifier circuit, a sweep circuit, a cathode ray oscillograph and a recording camera. Using this apparatus, (a) the effects of carbon content on the hardenability of steel as indicated by the critical cooling rate were analyzed quantatively and (b) the effect of maximum heating temperature on this property was studied. As the result of the study, it has been found that (a) the critical cooling rate is lowest at the eutectoid carbon percent, as reported by former investigators, (b) this cooling rate lowers with the rise of the maximum heating temperature, and (c) the relation between the critical cooling rate and the austenitic grain size seems to be linar in every specimen of carbon steel.

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To clarify the cause of high hardness of martensite in C-steel, the hardness of Fi-Ni alloys was measured and the following results were obtained. The hardness due to heat treatment was determined by (i) the degree of annealing of hardness of pre-homogenised quenching, (ii) the velocity of lattice transformation and (iii) the degree of annealing effect were destermired by the length of temperature interval after lattice transformation.

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The dilatation curves of steel by heating and by cooling cycles by obtained means of a common dilatometer (attached few springs) do not exactly coincide, that is, the cooling curve is usually located below the heating curve. This difference shows always the same degree of contraction in every repetition of heating and cooling under the same conditions provided that the specimens are cooled down to room temperature. Having made an investigation about the reason for such a peculiar phenomenon in steel, the auther has reached the following conclusion. It is a well known fact that during the transformation period of steel, a volume change occurs due to internal molecular movement or atomic rearrangement caused by dissolution of carbides in austenite (or separation of carbides). It is also well-understood that an enormously large internal stress accompanies this transformation, which according to Dr. Honda’s [K. Honda, Proceedings of the Japan Academy, Vol. 25 (1949), No. 1] calculation in tension or compression amounts to a few thousand Atm. pressures. This internal stresses keep equilibrium within, but if an external pressure be applied into one direction, even though the pressure is meager, the equiliblium will be disbalanced, consequently a deformation is liable to take place in the direction of applied force, however, It is, however difficult to continue the deformation after this transformation has once ceased. Judging by the above fact it will be concluded that the plastic deformation results by small applied compression during the transformation period only.

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In succession to our 13th and 14th report, the present investigation has been carried out to ascertain the effect of nitrogen, copper and arsenic on the impact-resistance, the decrease of impact-resistance by cold-work and V.P.H. The experiment was done on specimens containing C 0.01∼0.20, Cu 0∼0.85, As 0∼1.6, N₂ 0.003∼0.030. From the present investigation, the following results was obtained. (a) The same effect of nitrogen which was reported in the 13th and the 14th reports was recognized also in steels containing copper or arsenic. (b) The impact-resistance is not much changed by addition of ocpper. (c) By addition of arsenic, the impact-resistance is reduced, but the begree of reduction is not so strong as compared with the specimens containing phosphorous, (d) The strain-aging due to nitrogen increased severally in the range of 0∼0.006% of nitrogen in 0.4 percent copper steel as well as of 0∼0.005 percent in 0.2 percent arsenic steel.

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By electrolizing the alloys of aluminium with iron and silicon, the phases which are in equilibrium with aluminium, are extracted and subjected to chemical and X-ray analyses. The solid solubility of aluminium in silicon, which separates primarily, is found to be about 0.2% by weight, and the lattice constant of the silicon, thus separated, has been found to be a=5.419 Å. The phase, which is in equilibrium with aluminium in the system Al-Fe, is the compound FeAl₃. Below 500°C, the solubility of aluminium in the compound FeAl₃ increases according to the amount of aluminium, being proportionate to the formula Fe₂Al₇. Powder photographs obtained from the crystals separated from Al-20%Fe alloy showed the lines corresponding only to FeAl₃ having orthorhombic symmetry. No patterns which prove the existence of Fe₂Al₇ have been detected. There are two phases, α (FeSi) and β (FeSi), which are in equilibrium with aluminium in the ternary system Al-Fe-Si, and the contents of iron and silicon in these phases are determined as follows: α (FeSi), 30.15∼32.8%Fe, 8.39∼11.74%Si, β (FeSi), 23.52∼25.75%Fe, 15.77∼18.92%Si. A definite conclusion, however, was difficult to draw whether or not these phases have fixed or variable compositions. The analyses of the powder photograph obtained from these two phases have been made with tolerable coincidence with the data given by J. Phrágmen.

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