The relation between mechanical properties of extruded Al-and Mg-alloys, chemical conpositions and working conditions were investigated. The results obtained are summarized as follows:-
i) Pure Al; The rod extruded after the solution treatment by a lower extruding velocity and at a lower temperature has shown excellent tensile strength and elongation.
ii) Al-Mg alloy; The max. extruding pressure and tensile strength have been increased with Mg% up to 6%Mg. Elongation has been decreased to the min. value at 4%Mg, with a tendency to increasing with Mg% up to 6%Mg. Then, these properties have been changed to decreasing with Mg% from 6%Mg.
iii) The same phenomena have been found at 4% Cu on Al-Cu alloy, and at 4% Al on Mg-Al alloy.
iv) It is very interesting that the composition of alloys showing excellent mechanical properties coincide with that of the industrial light alloys.

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On the basis of our views concerning the precipitation and the ‘Umklappen’ in the phase change, some discussions have been given to the mechanism of formation of the austempering prcducts in carbon steels, and the following conclusions have been obtained:
i) The lower bainite is formed in the following course:
_??_
The lower bainite is, therefore, obtained by the austempering in the region of A' R' R'₀ in Fig. 2. It is also Obtainable in the case of lower-carbon than R', When they are cooled from a temperature above Ar''.
ii) The troostite_??_ pearlite is formed by two-phase (α and Fe₃C) precipitation and thus for this formation there is no need of such an intermediate stage as the martensite.
iii) When α' is tempered, one-phase precipitation of Fe₃C (or its cluster) takes place, the decomposition products being Fe₃C and residual α.

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The authors carried out experiments on the relations between heat treatment and magnetic properties of tungsten-chromium magnet-steel containing C 0.60, Si 0.19, Mn 0.35, Cr 0.89, W 6.01%, and then comparison of the austemper and martemper was made.
The results of this investigation may be summerised as follows:
(1) The most suitable normalizing temperature and annealing temperature of this steel are 975° and 730° respectively. (2) For the austemper treatment, the material was kept for 10_??_15min in the quenching temperature of 880°, and quenching in the hot bath of 200°, and then kept for 15min in it, and aging was done in boling water. (3) The austemper method is superior to the quenched tempered method.

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The author treated the problem relating to the aging phenomenon, corrosibility, grain size, heat treatment and structures rather than that of the constraction of the complex system.
From the results of determination of the above various properties, the author pointed out the compound τ is formed in the coexistence of manganese and silicon, which may not interrupt the formation of the main hardening element of the complex light alloys.

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From the point of view, that the graphitization process is the diffusion of carbon in matrix iron from cementite to graphite inherently present and that the iron-graphite alloy is existent, the graphitization phenomena have been explained as follows: - (i) S-shaped graphitization curves originate from two effects, namely one of them is the promoting effect due to the decrease of distance between cementite and graphite and the other is the retarding effect due to the increase of carbon content of matrix around the graphite during graphitization process; (ii) Incubation period of graphitization is the period in which the carbon content of matrix around the graphite increase its saturation with graphite; (iii) Promoting effect of quenching on graphitization is caused by the incrase of graphite nuclei on reheating after quenching; (i_??_) “Bull's eye” structure is due to the direct reparation of meta-stable ferrite α'_m from austenite around the primary graphite and to the following stabilization of α'_m to stable ferrite α' by the growing of primary grahhite in the temperature range between P' S' K' and P S K lines, in which the austenite will transform completely into graphite and ferrite but When cooled under P S K line before this transformation was completed the still existing austenite should change to pearlite. The formation of “Bull's eye” structure is quite similar to that of “abnormal” structure of steel.

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i) It was recognized that ordinary carburizers in which energizers such as Na₂CO₃ and BaCO₃ became mild carburizers with the addition of Al, Al+5%NH₄Cl, Si, Ferro-Si, SiO₂, Cokes, especially (NH₄)₂HPO₄, NH₄Cl and S. Charcoal was energized mildly (but a little strong) with NaCl, not with another chrolides for Cr-Mn-Si (Composition about 1:1:1). Gas coke was energized with Na₂CO₃, not with BaCO₃. From this study I found that perhaps such an energizer as mild and so deep cementatable may not be found.
ii) I also found that mild cementation was held when its surface carbon concentration was held at eutectoid pt. and so applied the diffusion theorey to it and decided the next formulas
_??_
where x: Case depth, W: Weight increase, t: Time, β Constant decided with carbon concentration difference. S: Area of surface ρ: Density of steel, C₀: Carbon concentration difference of inner and outer side, C₁: constart, W: Weight increase per unit time.

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(i) I enlarged the application-limit of diffusion theory on the carburization process in which I supposed that effective carbon concentration difference was the austenite difference (Acm conc. -matrix carbconc.) >900°C. This relation consists of the various carburization temperatures, frome this result (and the results of RagatZand Watase) it was found that: D=_??_
D: Diffusion const, D₀: Diffusion Const when T=0 T: Temp.
(ii) I discusseed the limit of use of the diffusion theory and handled two cases in which the surface carbon concen-tration were proportional to A₁ sin Cot, and A₂ (1-cocwt), from these calculations I could makeclear the mechanism of the maximum appearance in W (Weight Increase per unit time) curve. (t; time)

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It is well known that an austempered steel shows better mechanical properties (ductility, toughness, etc.) than a martempered (hardened and tempered) one which have the same hardeness, although the cause of these differences are unascertained.
But it is said that such properties of martempered steel relates to the occurrence of micro-or submicro -cracks in hardening, though their existence have not been generally accepted.
For solving this question, the authors have at first compared the austempered carbon steel (0.8% C) with the martempered in hardness, tensile strength, elongation, No. of twist and fold, etc. In this paper the results of these tests are discussed.

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When the Th-W filaments used for the vacuum tube are heated in carburizing atmosphere, the layer of W₂C can be formed on their surfaces. It has been recognized that this layer increases the thermoionic emissivity of the filament. So we studied the conditions of formation of the W₂C-layer.
Microscopic observations concerning the carburized Th-W filaments were carried out on the samples heated for 3 minuts under low pressure (1-5mm Hg) of C₆H₆ vapour at temperatures between 1800° and 1000°
In the case of higher carburizing temperature or lower vapour pressure of C₆H₆, coarse columnar crystals of W₂C were obtained, where as in the case of lower temperature or higher carburizing gas pressure, fine crystals were recognized on the surface of Th-W filaments, and the thickness of W₂C-layer was largest under the vapour-pressure of 1mm Hg and the carburizing temperature was higher, the thicker it became. The author pointed out that the isothermal transformation from a solid solution of W and C to W₂C by carburization was mainly responsible for the columnar crystal formations of W₂C.

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We often observe that the surface of steel articles dipped in molten salt would be frosted in time elapsing and the frost would invite corrosion. We supposed that the frosting may be caused by the creeping out of the included salt which had diffused into the steel body when dipped in molten salt. Conducting the experiment for confirmation of supposition, we obtained the following results.
(1) When steel articles are dipped in molten salt, a part of it diffuses into the steel body.
(2) It diffuses mainly into grain boundaries.
(3) Observing the diffusing rate, the diffusion constants are obtained.
(4) The diffusion constants vary with temperature.
(5) If steel articles which have contained diffused salts is embaded in charcoal powder and heated, cementation is proceeded with a rate higher than in other steel ones not treated.
(6) We found a method to prevent such salt diffusion, which is to electerolyse with D. C., steel articles being held as the cathode.

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At present, the determination of SiO₂ in slag must depend upon the method of evaporation to dryness with HCl, but in the case of slag which contains too much Cr, it takes a long time to filter, and it is difficult to obtain the total SiO₂ by once or twice dehydration. But by evaporating after the addition of NH₄Cl, the time of filtration could be reduced to 1, 10, and the total SiO₂ could be obtained only by twice dehydration and thus the method of determination of Silica was simplified and made accurately. The mechanism of the addition of NH₄Cl was discussed theoretically.

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