The author considered the general relation between the failure and the stress for annealed steel and cast iron,taking into account the effects of structure upon the strength.In these cases the author assumed that the failure of metallic material would occur in two kinds of forms,namely,tough and brittle, depending on both its own strength (sliding or separating) and type of stress (shearing or nomal tension), but not on its apparent feature. The conclusions were as follows:
(1) The yielding point σ_xs of steel containing x% of carbon can be formulated as being σ_xs=σ_fs+(σ_ps-σ_fs)(x/0.9)^2/3, \labeleq1
where σ_fs and σ_ps indicates the yielding point of ferrite and pearlite, respectively.
(2) Proportional limit of steel occurs at the stress σ above σ_fs, originating in failure in ferrite which was inhibited temporarily by the pearlite phase. The elastic elongation ε_l of composed phases in that instance may be written as follows: ε_l ≥σ/E+(1+2/m)(σ-σ_fs){(0.9/x)^1/3+(x/0.9)^1/3}/2E \labeleq2
where E is the Young’s modulus of each phase and m is the Poisson’s ratio.
(3) The tensile strength of cast iron σ_B was discussed,using the following equation: σ_B=(σ_t/α_k)(A-ΔA)/A \labeleq3
where σ_t is the separating strength of steel part in cast iron, α_k is the stress concentration factor,ΔA is the sectional area occupied by the graphite part and A is the total area of specimen.For cast iron,however, the comparison with the experimental data was considerably unsuccessful, because of some arbitral estimations or assumptions.
Besides, the author dealt with problems in bending, torsion and compression for cast iron and with the effect of outer notch for steel and cast iron.

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The author proposed the general formula for the fatigue strength as follows: σ_nW=σ_n-k_1τ, \labeleq1where σ_nW and σ_n mean the fatigue strength,respectively,with or without diminishing the effect caused by repeated load having the stress difference τ in shearing,and k₁ is a coefficient depending on micro-slip-path besides τ. In other words, σ_n correspends to the separating strength discussed Previously.
For steel,k₁ is about 2.8∼3.3 and σ_t is equal to (2.3∼2.7)σ_u,where σ_u indicates the fatigue limit in single blow tension. Furthermore,the following expressions were derived, respectively: σ_W,fatigue limit in tension and compression=(0.53∼0.68)σ_u, σ_W′, fatigue limit in bending\doteqdot(1.1∼1.3)σ_W, τ_u, fatigue limit in single flow torsion\doteqdotσ_W, and τ_W, fatigue limit in double blow torsion=(0.3∼0.4)σ_u. With the same conception, for cast iron, σ_u′, σ_W′, σ_W″, τ_u′ and τ_W′ which correspond to σ_u, σ_W, σ_W′, τ_u and τ_W respectively, for steel, were expressed using stress concentration factor α_kt (in tension) or α_kt (in shearing), correcting factor k₂ against k₁ and factor δ in bending. For an example, for σ_W′ the following formula was derived : α_ktσ_W’=σ_t-k_1k_2(σ_kt/2+α_ks/2)σ_W’ \labeleq2
For steel containing x% of carbon, an approximation was put forward empirically as follows: σ_Wx’=(0.6 ∼0.9){σ_fs+(σ_ps-σ_fs)(x/0.9)^2/3}\labeleq3
where σ_fs and σ_ps indicate the yceld point of firrite and pearlite, respectively. This idea could be applied also to the carburized steel, which is considered to be composed of harder outer case and softer inner part. Furthermore, the author discussed the outer notch effect on fatigue.

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In the past investigations, it was explained that there was the softening process before recrystallization of strained aluminium, namely, recovery process.
These investigations were carried out by using polycrystalline aluminium,which had received very complex strain in cold-working owing to disorientation of grains and irregularity of atomic arrangement at grain boundaries. For these reasons, the observed hardness values for the same specimen were at random and one could not find small changes in recrystallization.
Therefore we used single crystals for this experiment. According to our experimental results, there were two steps in recovery process. One is the softening process,the other the hardening process. And the second hardening process occurs through rather severe cold working before recrystallization itself.
On the other hand, microscopic observations were made. Judging from this observations, obviously the first softening process was reduced to the disappearance of strain (dislocations), but there were no changes in the second hardening process. Furthermore,the polygonization was a successive phenomena from the beginning of annealing(recovery)till the recrystallization, and yet probably it was related to deformation bands formed by cold working.
We are now obtaining some interesting results by electron microscopic investigation upon the second hardening process.

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The cracks caused by working of aluminium slab often originate in the casting cracks, so the experiment was carried out to find how these cracks could be prevented under different casting conditions. About 1 kg of aluminium was cast in an iron mould, the inner dimension of which was 200×120×16 mm. The mould was fixed with the melting crucible and they were rotated together by a driving motor to get a difinite pouring speed. The metal was poured at different casting temperature, pouring speed and temperature of mould, and after the solidification, the ingots were examined with eyes or under microscope. The results were as follows:
a) The faster the pouring speed was,the greater was the cracking of ingot at the upper parts.
(b) The higher the temperature of the mould, the less the cracking was.
(c) With pure aluminium,the ingot was apt to crack for its large grains.
(d) The lining of the mould could present the casting crack.

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In previous paper, I have reported the mild carburization by suppressors was not different from that by a mild promoter. Though the annealing treatment of super-carburized layer at high temperature or in vacuum is considered as another mild carburizing method besides the above-mentioned method, various defects in it may be conceived. As it is considered that the best method of mild carburization is to use the adequate mild promoters in each carburizing condition, I tried to establish in this study the suitability of various promoters for the mild carburization. First, the foundamental tendency of surface carbon content of plain carbon steel was studied by changing the carburizing temperature, and time was measured in the case of 35%BaCO₃ and 5%Na₂CO₃, respectivly as promoter. It was found that Na₂CO₃-CaO system as promoter was excellent for the mild carburization. Finally, the characteristics of various promoters for chrome-steel were clearified from the results of the carburzation by using the eleven sorts of carbrizers in the temperature range of 920∼980° and the time range of 5∼10 hrs.

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As an example of inland poor iron ore, we studied Oeyama nickel containing yellowish earth which had the following composition: Fe 34.06% Ni 0.71% Si 7.55% Al 11.35% Mn 0.58% Cr 1.34% S 0.04% P 0.01% ignition loss 9.60%. The results obtained are as follows: (1) Dehydration velocity of this earth has a very large value and hydration velocity of once dehydrated one decreased with elevation of dehydration temperature. (2) Reduction velocity of the earth by hydrogen or carbon monoxide hads a large value. (3) Iron reduced by hydrogen at temperatures blow 950° is spotaneously combastible.

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The influence of carbon and silicon on the spherulitic graphite iron, treated with 0.5%Mg in the form of Mg-Ni-Si-Fe-Cu-Al alloy containing 10.87%Mg,was investigated,using specimens cast in dry sand mould of dia. 14 mm. The following results were obtained:
(1) The matrix became pearlite plus ferrite when the total of carbon and silicon exceeded about 7% and manganese content was about 0.5%.
(2) The more the content of carbon in the iron increased,the larger the size of the spherulitic graphite in the iron became and the more its number increased.
(3) The more the content of silicon in the iron increased, the smaller the size of the spherulitic graphite in the iron became and the more its number increased.
(4) The more the content of carbon in the iron increased, the lighter the colouring of magnesium print became, the print being obtained in the same way as in sulphur print.
(5) The more the content of silicon in the iron increased, the heavier the colouring of the print became.
(6) Both desulphurization and decarburization of molten iron due to the addition of magnesium were promoted by increase of carbon or silicon in the melt, although the alloying efficiency and the available magnesium % of the added magnesium alloy decreased thereby. The principal reactions are presumed to be as follows:
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The authors investigated the solidification process of Fe-C alloy experimentally comparing with that of Al-Si alloy. The results obtained are as follows:
(1) When the hypo-eutectic Fe-C alloy was slowly cooled,primary dendrites of austenite were formed at first,then at eutectic temperature the austenite named SASANOHA structure, which were super-saturated with carbon,developed from the primary dendrites.
The super-saturated carbon crystallized out on the axes of SASANOHA as cementite,which immediatly graphitized to so-called flaky graphite. Besides, the linkes of cementite remained on the grain boundaries of austenite and in a few cases it happened that the blocks of cementite were closed in the austenite,and they turned into chain-like graphite and block graphite with the lapse of time.
(2) As to the hypo-eutectic of Al-Si alloy,the primary dendrites of Al were formed at first, then SASANOHA solid solution of Al developed followed by the separation of Si on the axes of SASANOHA. The final structure was the eutectic Si-needles which corresponded to the flaky graphite in Fe-C alloy.

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When nickel plates for vacuum tubes are annealed in hydrogen gas at 900∼1000° in the process of production, their surfaces are often tarnished and show milk-white appearance, which considerably lowers their commercial value. In order to infer the cause of this tarnishing, six kinds of plates were selected and their surfaces were examined by electron diffraction after the heat-treatment. Milk-white surfaces gave generally diffuse rings, which were entirely different from the nickel pattern. Many rings were obtained from two kinds of tarnished surfaces,but another tarnished surface gave only one diffuse ring. Three specimens did not alter their appearances after the treatment. One of them gave a few diffuse rings and elongated spots, while the other two, one of which was made in U.S.A., yielded many comparatively sharp rings. According to our analysis,rings obtained from the two milk-white surfaces were due to(Mg,Ca)SiO₃ and NiO,and those from the two lustrous surfaces belonged to nickel and Mg₂SiO₄ in the one case and to nickel, MnO, MnS and NiO or to nickel, Mg₂SiO₄, MnO and NiO in the other case. From the fact that a great part of diffraction rings of the milk-white surfaces can be explained as being due to (Mg,Ca)SiO₃, it is concluded that the tarnishing is due to silicates of light metals. They were also found on the lustrous surfaces, but because of their minute quantity, appearances of the surfaces were not altered by the heat-treatment. An apparition of the oxide and sulphide of manganese in some cases was due to a comparatively large quantity of this element in the specimen in question. Silicates like (Mg,Ca)SiO₃ and Mg₂SiO₄ must be removed at the time of melting, but if a small quantity of them remains and is dispersed over the whole material, it may gradually aggregate at grain boundaries by the heat-treatment, which finally causes the tarnishing of surfaces.

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The authors investigated the alloys containing up to 61.3% of Mn from various stand-points, namely, microstructures, hardness changes under various heat-treatments, temperature dependence of electric resistvity and thermal expansion, and density at room temperature. Most outstanding results were as follows:
(1) The solubility curve of this system showed the form similar to that proposed by Grube but with a slight difference from it in the range of lower concentration, and did not agree with the type reported by Ishihara & Isobe.
(2) The alloy with about 10% of Mn displayed some anomalies at the higher temperature range, although it was conceived to be homogeneous solid solution. Furthermore, in the alloys of higher concentration, a singular process of a certain transformation type was supposed to exist, regardless of the solubility change.
(3) The activation energy of hardening in the alloy containing 42.9% of Mn which was quenched from 750° and aged at 400∼550° was about 23,600 cal/mol., but it was very small in the alloy of 61.3% of Mn.

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A microscopic study on the structure of aluminium single crystal produced by the critical strain method was carried out with the etching solution of P.Lacombe. We recognized, by inserting in hydrogen gas, the considerable change in the structure,when uniform and non-uniform deformations or the heat treatment were done.
The results of the experiment may be summarized as follows:
(a) Etch pits of pure aluminium single crystal are smaller than those of the crystal prepared from the molten metal into which the water vapour is blown.
(b) The specimen cold-worked by about 60 per cent in reduction reveals the sub-boundaries, and the sizes of the sub-boundary become larger with an increase of the volume of the occlude hydrogen gas.
(c) A weakly deformed specimen including hydrogen gas often reveals sub-boundaries by annealing for 20 hours at 620°C.

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The present investigation was carried out to ascertain the effect of heat treatment on the natural age hardening and temper hardening of Al alloys containing Cu and Sn which had been used for bearing materials.
As these test pieces were prepared by addition of the mother alloys (Cu₆Sn₅ Cu₃Sn) and Mg to Al, the results obtained from the study of Al-Cu₆Sn₆, Al-Cu₃Sn, and Al-Cu₆Sn₅-Mg systems were as follows:
(1) All the alloys of these systems did not show a natural age hardening at room temperature, and the temper hardening was remarkable except the two alloys containing 2%Cu₆Sn₅ or Cu₃Sn.
But the addition of 1.5%Mg to these two alloys gave an influence upon the temper age hardening. From these results,it was certain that Cu and Sn were soluble in Al.
(2) By heating these natural aged alloys at 220° for a short time, the hardness increased at first and decreased, and then increased.
This first hardening seemed to be a temper hardening with-out a certain precipitate and the second by it.

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In titrating the hydrochloric acid solution of the metal oxine,the author found that the amount of the bromate-bromide solution to be added is of vital importance in obtaining is correct result. In the bromization of oxine with the bromate-bromide solution, care should be taken not to add much excess of the solution, otherwise, by the subsequent addition of potassium iodide, insoluble iodine separates out together with a chocolate brown precipitate of an iodine addition product. After the back titration with thiosulphate, the blue colour of the starcd indicator returns again after standing the solution for a while, and this is liable to give too high a result in the analysis. The phenomenon is best explained by assuming that in the presence of dibrom-oxine, the solubility of iodine in potassium iodide solution is greatly diminished. The method, therefore, differs from an ordinary sense of the back titration, for the excessive bromate-bromide solution is restricted within a comparatively narrow limit.
In order to avoid too much excess of bromatebromide solution, the author prefers methyl orange instead of indigo carmine as shown in Table 3. The best plan to perform the titration proposed by the author is as follows: Add 2 or 3 drops of methyl orange to the hydrochloric acid solution of metal oxine and bromize with the bromate-bromide solution; if the colour of methyl orange fades away, add some drops of the methyl orange and continue to bromize. If, on the addition of methyl orange indicator, red colour fades away, stop the bromization.Dilute the solution to about 300 ml, add about 6 gr of potassium iodide, and the solution should be clear brown,free from precipitate, titrate with thiosulphate,using starch solution as an indicator toward the end.

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A colorimetric method of determining micro-quantities of silicon in steels was studied with the Pulfrich’s photometers, whith was carried out in presence of iron, eliminating its interferences by an addition of fluoride. As little as 0.01% of silicon in steels is determinable by this method within about ten minutes, and also some permanent colorimetric standard solutions of this yellow color have been prepared in order to make possible the colorimetric determination by means of some usual colorimeter.

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A colorimetric method with molybdenum blue for a rapid analysis of micro-quantities of silicon in steels was studied with Pulfrich’s photometer. By the molybdenum blue method,using ferrous iron and oxalic acid as reducing reagent, silicon can be determined colorimetrically in the presence of iron. As little as 0.01% of silicon in steels is determinable by this method within about ten minutes.

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