In some kinds of cold worked metals and alloys sometimes an extraordinary hardening occurs by the annealing at the lower temperature than their recrystallization one. The cause of hardening is attributed to the precipitation, or precipitation process is caused by the decrease of the solubility limit after cold work. We examined the low temperature phenomena of the cold worked purest Ni, Cu, Ag, Fe (C%: <0.01%) prepared chemically, by observing whether the hardening had occured or not from the hardness-time curves measured at each constant temperature from room temperature to 600°C. The conclusions of the experiments performed with the pure metals are as follows: (1) Generally, it is concluded that the hardening phenomenon is seen even in the pure metals in low temperature annealing after cold rolling. In this case, there is a linear relation between the time of reaching maximum hardness and that of the reciprocal of the absolute temperature. (2) Variously treated pure Ni showed the same hardening phenomenon (same hardness) in the low temperature annealing except in the case in which the time of reaching maximum value of the purest one was slower than the other. (3) In the case of the pure Fe the hardness obtained in the low temperature annealing after cold work was greater than the value obtained by water quenching the specimen from high temperature in α-range and subsequently aging at the same temperature. From the above mentioned phenomenon, we found that the hardening produced by the low temperature annealing can not be solved only by the precipitation theory or as the process of precipitation even in precipitating alloys.

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It was clarified in the previous report that the internal strain could easily and sensitively be detected by using inverse Wiedemann effect and that the change of the internal strain along with the process of the fatigue could slso be detected. In this report the change of the internal strain of the torsionally worked specimen caused by the repeated loading was measured by this method. The Schenbk-type’s torsion fatigue tester was used. The experimental apparatus used was the same as in the previous report. The results are briefly summarized as follows: (1) Intensity of induced current is always low at the early stage of the fatigue regardless of the applied load. And the heavier load in, the greater the degree of the lowering value is. I think that the lowering of the value is due to the relief of the torsional internal stress but the established facts cannot be discussed only from the experimental results which have been made clear here. (2) Increase of induced current is generally recognized before the fatigue failure. And the phenomenon of moving up and down of the current density with the process of the fatigue is not recognized in the present case, while the case of the non worked specimen is characteised by the fluctuation of the value. (3) In the case of load less than the fatigue limit the lowering of intensity is also recognized. But the degree of lowering is small and the induced current soon reaches the stationary value. The heavier load is, the larger the number of repeated cycles needed for saturation of induced current is. (4) When the fatigue limit is raised and the slope of the wohle curve becomes solw in the case of the worked specimen.

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In this report I studied the change of the internal strain along with fatigue for the specimens of carbon steel, (0.4%C) pure iron and nickel by using the same apparatus as in the previous report. The results are briefly summarized as follows: (1) By Inverse-wiedemann Effect, even the small strain can be measured very sensitively and quickly, that is, the existence of the fatigue can easily be detected. (2) If the load is classified into three kinds,-larger, less than the fatigue limit and equal to the fatigue limit-the process in which the value of the induced current changes with the propagation of the fatigue is almost similar in spite of the difference in the specimens. The heavier load is, the larger the fluctuation of the value is and the amplitude gradually reaches a small value if the load approaches the fatigue limit. Under the load less than fatigue limit the fluctuation of the induced current is very sensitively recognized in the early stage of the fatigue but it soon reaches the stationary value. (3) At Exciting current of 10A, the maximum value of the induced current was about 35 μA in carbon steel, 60 μA in pure iron, and almost zero in nickel. But if the exciting current is raised to 25 A, we can recognize the value larger than zero even in nickel. (4) If we measure the residual stress caused on the fatigue by Inverse-Wiedemann Effect, the value becomes about 3.5 kg/mm³ in carbon steel and 0.21 kg/mm² in nickel. Considering the internal changes of material caused on fatigue very small, it is very interesting that the residual stress is very small in comparison with that of the specimen cut by a lathe, in spite of the fact that my method is different from the ordinary ones. (5) It was recognized that the internal strain would disappear in early stage of the fatigue when the specimen has residual stress. This phenomenon was same as the result published in my fifth report. (6) Each fatigue limit of carbon steel (0.4%C), pure iron and nickel was 17.2 kg/mm², 9.2 kg/mm², and 11.5 kg/mm², and each proportional limit was also about 18.5 kg/mm² in cardon steel and 8.5 kg/mm² in pure iron.

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In order to know the effect of cold-working upon the age-hardening, Al-Cu-Mg-Zn alloy was rolled in cold after annealing, quenching or age-hardening and the change in hardness was studied. The hardening during cold-working increases but the hardening by aging after working decreases as the reduction of rolling increases. In process of heating after rolling (upward of reduction about 40%), the slip lines were observed with the microscope from the temperature at which precipitation ocucrred and they grew with rising temperature. It was clear that the minimum interval between two lines was 2∼4 μ and also the slides at cross 2∼5 μ at heigher reduction.

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On the combustion of charcoal which is important for heat treatment of steels, such as carburizing bright annealing, was investigated under various condition.
The results obtained are as follows : At any temperature, the oxidation of charcoal by air proceded rapidly, but reduction of produced gas in charcoal layer was gradual. Psedo-equilibrium state was easily reached at high temperature. The difference in behavior of combustion of charcoal layer comprising different particles was due to the velocity of gas flows passing through charcoal layer and also the effective area of the particles. Most of salts of Na, Ba and Ca are effective catalytically in the combustion of charcoal, but not Na₂B₄O₇ and Na₃PO₄. Mg salts are slightly, Al₂O₃ and SiO₂ are negatively and oxides of Fe, Co, Ni, Mn and Cr are not effective.

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The reaction on steel of the combusted gas of charcoal with dry air was investigated, with a view to the bright annealing and carburization. The results obtained were as follows : From the equilibrium relation, it seems possible to make steel have any amount of carbon by the reaction of gas having a given composition at any desired temperature. On the contrary, carburizing power of the gas was too week to reach the theoretical carbon content even at high CO% and high temperature. It was concluded that the weekness of caburizing power of dry charcoal combusted gas was due to the hindering reaction of CO₂ which was produced by the carburizing of the steel.

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In the previous report, the present authors studied the Thermal change of binary compact constituenents of which form a simple binary eutectic alloy. the resulT showed that even in a mechanical mixture of powderly metals, the similar phase change would take place as in the case of an alloy made by melting. In the present works, the object is to confirm whether the similar change will occur in the case of binary alloys which form an intermetallic compound.
The following alloy systems were experimented : Te-I, Mg-Pb, Mg-Sb, Mg-Zn, Te-Pb, Mg-Bi, Mg-Sn and Te-Bi. From thermal behaviours of compacts composed of these metals in heating, four types of the formation of intermetallic compound were recognized as follows :
(a) The formation of intermetallic compound takes place at a lower temperature than any of the eutectic temperatures in the alloy system.
(b) The formation of intermetallic compound takes place following one of the eutectic reactions.
(c) The formation of intermetallic compound takes place at a temeperature between the two eutectic reactions.
(d) The formation of intermetallic compound takes place at a higher temperature than those of any eutectic reactions.
In the cases of (a), (b) and (c), a metal compact of eutectic composition melts at the eutectic temperature, but in the case of (d), it hardly melts at the eutectic temperature.

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Acidity is defined as the tendency to accept an electron-pair from a base. Basicity is defined as the tendency to donate an electron-pair to an acid. Taking O⁼ in place of electron-pair, the authors made two scales of acidity and basicity of the constituent oxides of slag by using thermodynamic cycles and discussed the validity of these scales. The basicity scale is not sufficiently explicit in the case of comparing each group of different valence types, and the acidity scale is not general in use yet because of the difficulties in determining the radii of negative polyatomic ions.

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The carbon content in the produced pig iron in relation to the change of the charging combination is chiefly treated in the present investigation. The construction and dimension of the furnace are generally same as that of the first report, in consideration of some facts indicated in the previous conclusion. The effects of the changes of the charging combination on the products were examined, and, in general, the carbon content of the products increases proportionally to the coke ratio of the charge. That effect changes in accordance with the various kinds of coke, and in the present experiments, A gas coke which consisted of the fixed carbon is largest and ash content which was smallest as compared with the other kinds of coke, were most effective. There seems to be no relation between the basicity of slag and the absorption of carbon, The addition of the pig iron scrap to the combination of the charge could not be seen to be always effective in the carbon absorption. Tensile strength and hardness of the products are in inverse proportion to the carbon content.

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The flow of molten metal in the green sand mould was investigated by measuring the running length. Results obtained are as follows :
(1) Running velocity is related to \sqrt2ga (here, a is the height of molten metal), but the amount of metal used has little effect upon the running length within some limit of a. (2) Falling head affects the running length but the effect of sectional area of gate upon it is related to the size of ruuner and the height of head. (3) The heigher casting temperature and the less moisture in sand, the longer they become; but it is not always so with temperature, when the falling head is heigher. (4) Height or angle of branching to runner and shapes at the entrance have some effect on them. (5) When the thickness of ruuner is narrowed on the way, it is not length or situation but degree of them that is the master of the running length. (6) When the width of runner is changed but the thickness is constant, the most suitable width is existent for some size of gate.

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Several properties, namely, appearant density, permeability, stability at the surface of sand and bending strength, of Osaka-sand mixed with Nagoya-silica sand were investigated. Results obtained are as follows: (1) The increase in the amount of sand will make properties worser and worser,and, when mixed in equal ratio, they were worst. (2) They approached the properties of sand when the amount of added sand became less.

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In Japan, especially in the north-eastern district of Japan, there are a considerable number of hydro-electric plants which have to use acid river water because they are located in volcanic zones. In these electric plants, penstocks, hydraulic turbines and other metallic parts of the equipment are being corroded severely by acid water. Thus, the length of usefulness of such an equipment is greatly reduced, compared with that of similar equipment in other electric plants, which do not suffer from acid water corrosion. The cost for repair and the annual loss of electric power amount to a surprisingly large sum.
The results of analyses of several types of acid river water show pH values at electric plants to be about 5.0 to 3.0. pH values are lower at the upper reaches of the rivers. Acid constituents of acid water are sulfuric acid and hydrochloric acid, and in rare instances nitric acid. The purpose of our studies is to make clear the mechanism of corrosion and to prevent damage arising from it.

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Our experiments were conducted to study the corrosion of iron and steel parts in the hydro-electric plants. In quiet acid water, containing H₂SO₄ or HCl, mild steels are corroded with the evolution of H₂ gas when the pH value is less than 4.3. The corrosion rate is about the same either in H₂SO₄ solution or HCl solution when the solution is of a very dilute acidic nature. The influence of anions (SO₄″ or Cl′) on the difference in corrosion rate of steels in a H₂SO₄ or a HCl solution is very slight ; the corrosion action is considerably greater in a HNO₃ solution. When there is no evolution of H₂ gas (when the pH value is greater than 4.3) the corrosion rate is constant, and independent of the pH value. In quiet water, the corrosion rate is very small compared to that in running water, that is, when the specimen is being rotated in acid water, the corrosion rate increases in proportion to their r.p.m. The corrosion rate in running water increases when the pH value is decreased from 7.0 to 4.3, but it becomes constant when the pH value is less than about 4.0, even if the acid concentration of water increases. This is due to the fact that the corrosion rate in dilute acid running water is greatly influenced by dissolved oxygen in water. The corrosion of steels in running water, or when the specimens are being rotated, is very severe because of the combined reaction of hydrogen ion and dissolved oxygen in water.

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The author has succeeded in carrying out the rapid simultaneous polarographic determination of copper and zinc in brass in about 20 minutes by using 10 drops of saturated aqueous solution of Na₂SO₃ as oxygen eliminator and utilizing the two relation curves, one of which shows the relation between the waveheight-ratios and the concentration-ratios of zinc and copper, and the other the relation between the concentration ratios and the contents of zinc and copper. The use of the waveheight-ratio as mentioned above made it possible to remove not only the effect of temperature and capillary, but also the errors in measurements.

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