The influence of an addition of 10 percent and of 20 percent of nickel on the thermal expansion in the range of 10° to 50°, rigidity modulus at 20° and its temperature coefficient in the range of 20° to 50° of the alloys of cobalt, iron and chromium has been examined. The relations between those properties of nickel-added alloys and the concentrations are qualitatively almost similar to those in the case of the ternary alloys of cobalt, iron and chromium; that is, there are two groups of alloys, one of which has a positive temperature coefficient of rigidity modulus and the other a negative, a zero coefficient boundary existing between them. The addition of nickel affects the coefficient of thermal expansion and the temperature coefficient of rigidity modulus of the ternary alloys, as if cobalt can be substituted by nickel; that is, the compositions, at which the thermal expansion coefficient shows the minimum value and the temperature coefficient of the modulus a positive maximum, shift to the side of low cobalt content with the addition of nickel. Further, if the quantity of nickel is increased, the concentration range having the positive coefficient of the modulus becomes wider, and the slope of the latter to the concentration slower.
When the quantity of the added nickel is 10 percent, the minimum value of the thermal expansion coefficient is 2.20×10⁻⁶ obtained with the alloy containing 43.5 percent of cobalt, 47 percent of iron and 9.5 percent of chromium, and when 20 percent of nickel is added, it is 1.69×10⁻⁶ obtained with the alloy containing 31.3 percent of cobalt, 60.2 percent of iron and 8.5 percent of chromium. In the case of an addition of 10 percent of nickel, the positive largest value of the temperature coefficient of rigidity modulus is +46.7×10⁻⁶ obtained with the alloy containing 43.5 percent of cobalt, 47 percent of iron and 9.5 percent of chromium and in the case of 20 percent of nickel +66.0×10⁻⁵ obtained with the alloy containing 34.5 percent of cobalt, 58.5 percent of iron and 7 percent of chromium. The maximum and minimum values of rigidity modulus in the case of 10 percent of added nickel are 9.10×10⁵ kg/cm² in the alloy containing 65 percent of cobalt, 15 percent of iron and 20 percent of chromium and 6.00×10⁵ kg/cm² in the alloy containing 71 percent of cobalt, 25 percent of iron and 4 percent of chromium, respectively, and in the case of 20 percent of added nickel, 8.36×10⁵ kg/cm² in the alloy containing 41 percent of cobalt, 40 percent of iron and 19 percent of chromium and 5.09×10⁵ kg/cm² in the alloy containing 32 percent of cobalt, 61 percent of iron and 7 percent of chromium, respectively.

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The hardness, structure, and the thermal electromotive force as well as the density of forged plain iron-cobalt alloys have been studied. The hardness difference produced by slow cooling and quenching reaches the maximum at 26 and 76 percent cobalt, the maximum value of the thermal electromotive force is observed at 26 percent cobalt and the minimum at 76 percent cobalt, and rise of hardness is noticed in the range from 26 to 34.5 percent cobalt by keeping the specimen at the temperature of 300° to 400° for 4∼6 hours. As 26 and 76 percent cobalt correspond to Fe₃Co and FeCo₃ points respectively, the facts may be looked upon to indicate the probable existence of Fe₃Co and FeCo₃ superlattices.

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The electric resistance have been measured with forged plain iron-cobalt alloys as objective. Temperatures where the changes of the electric resistance, hardness and structure occur, were found to exist in the composition range from 20 to 76 percent cobalt and to coincide with the line of the order-disorder transformation and its extention, indicating that the transformation of FeCo superlattice may exist in the range from 20 to 76 percent cobalt. The heating curve of the electric resistance of ordered specimens shows that an unordinary change occurs in the range from 40 to 60 percent cobalt with FeCo at the middle, at the temperature of 430° to 580°, which coincides witch the temperature at which an unordinary change was seen by Dr. Kaya when he measured the specific heat of the FeCo specimen.

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The rectifying characteristics, their temperature dependence, the change of forward current at 0.8 V and the reverse current at 6 V of copper disks containing various kinds of impurities were studied and the following results have been obtained: (1) The rectifying characteristics of cuprous oxide rectifier increases with the purity of copper. (2) With the increase of silver content from 0.001% to 1%, the resistance in the reverse direction increases, but scarcely varies in the forward derection. The copper disks containing 0.1∼1% Ag show higher creeping tendency than the others. (3) When copper contains 0.001% Zn, the rectifier shows the highest efficiency. (4) As tin content increases from 0.001% to 1%, the rectifying resistance increases in the forward direction, while decreases in the reverse direction. (5) As nickel content increases from 0.001% to 1%, the resistance increases in both directions. (6) When copper contains 1% Ni or 1% Sn, it is difficult to prepare rectifying disks, mainly because of nonadherence of the oxide layer. (7) The forward current in running test increases in the first few minutes, but afterwards it remains almost constant.

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For studying the mechanism of the decarburization reaction, the rate of the carbon removal with oxygen gas was measured and the specific velocity constants were determined over the temperature range, 1430∼1780°. Fe-C alloys containing about 4% carbon were melted by means of a high frequency induction furnace and decarburized by an oxygen stream. In this experiment purified air was used as oxygen source. The rate of carbon removal in this system was determined by flow method. It is expected that as a first step in this reaction the gaseous oxygen is dissolved in molten iron and then the decarburization reaction occurs. In this case the rate of carbon removal may be given by the following equation:
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As the second term on the right side of the above equation may be neglected in consideration of the experimental conditions and the concentration of oxygen, entering the reaction, is constant during the reaction, this equation may be simplified as follows:
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Integration of this simplified equation gives:
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\ oindentwhere C_t1, C_t2 stand for the respective carbon contents in molten alloys at time points t₁ and t₂. By means of measuring C_t1 and C_t2 at given times the specific constant k₀ was calculated at various temperatures. Log k₀ plotted against 1⁄T was found to give a straight line with a slope corresponding to the apparent activation energy of about 13 kcal/mol. Since the reaction may be regarded as a first order reaction with respect to carbon content, the decarburization reaction is deemed to occur by the following steps:
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\ oindentand in these reactions the step determining the rate of decarburization seemed to be the reaction between carbon and oxygen dissolved in molten alloys. Concentration gradients of carbon was mainly eliminated by convection rather than diffusion in these experiments.

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To be continued to 8th∼9th report, the present investigation has been carried out to ascertain the effect of nitrogen on the elongation at the yield-point and serrated deformation in steel. From the present investigation, the authors concluded as follows: (A) The elongation at the yield-point in steel is due to the nitride (or carbide) which was precipitated from α-iron at 0∼250°. (B) The serrated-deformation in steel is due to the precipitation of nitrogen (or carbon) from α-iron by the existence of working stress during the test.

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The present investigation was carried out to ascertain the effect of nitrogen on the corrosion resistance of steels Corrosion test, (in 1∼1.6% H₂SO₄, for 5∼24 hours at 50°) were carried out with low carbon steels containing various amounts of nitrogen. All the specimen were air-cooled from 950°, and then slowly cooled after tempered for 3 hours at 550°. And the specimen was given cold work at room temperature by the method of tension or drawing. From the present investigation the authors concluded as follows: (1) There is a clear correlation between the nitrogen content in steel and corrosion resistance. (2) With the specimens at annealed state, the corrosion increased with the increase of nitrogen content. (3) With the specimen in cold-worked state, the corrosion increased steeply with the increase of nitrogen up to 0.007 percent, over which a slower increase may be seen. (4) By the addition of denitrogenizer at molton condition, or by removing the nitrogen from steels by annealing in a stream of hydrogen, the corrosion resistance is increased.

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This experiment was conducted to study the corrosion of carbon steel knives in the Jordan Engine which treats the pulp solution containing aluminium sulphate, rosin soap, etc., of pH values ranging from 4.5 to 5.2. The carbon steel specimens (0.3% C and 0.8% C) were rotated in water at varying r.p.m. (0∼1400) and pH of water (3.2∼6.5), and corrosion loss of the specimens was measured. The corrosion rate of carbon steel in Al₂(SO₄)₃ solution increased gradually with the increase in acidity at constant r.p.m., but was far less than in H₂SO₄ solution with the same pH value, and at the same r.p.m., the rate was about 1/10 of the values found in the latter solution. This is due to the inhibitive action of positively charged colloidal particles of Al(OH)₃ which was produced by the hydrolysis of Al₂(SO₄)₃ solution and was adsorbed on the cathodic area of the local cells of corrosion. Cupric ions in the solution markedly accelerated the corrosion by acting as a depolarizer for hydrogen and moreover producing galvanic corrosion due to the metallic copper reduced on the steel and these effects increased with the increase in r.p.m. Therefore a pipe of copper or copper alloy should be avoided as conduit-pipe to carry the pulp solution at a high speed into a Jordan Engines. 12% Cr stainless steel was perfectly immune against the solutions under the conditions mentioned above.

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In our previous study on the recrystallization diagram of high purity aluminium, it was found that a coarsening takes place only in aluminium of 99.9% grade and that its range seems to be limited within the purities from 99.911 to 99.985%. In the present study, the authors looked into the effects of various impurities (Cu, Fe, Si, Mn, Mg, Zn, and Ag) on the coarsening of 99.99% Al which is hard to coarsen in the case of initial annealing at 350°. Then it was found that a remarkable coarsening takes place between 15 and 45% of reduction in some additional range of Cu, Si and Ms respectively, and Fe and Mn induce the coarsening in the lower reduction than 5% as expected, but Zn and Ag do not induce it at all. It was also found that a coarsening would take place in high purity aluminium whose composition is just in the range to be coarsened by Cu and Si, but no coarsening occurs outside of its range.
Regarding the reason of coarsening, the oriented growth theory is most widely accepted at present, but its study has been in most cases carried out on aluminium higher than 99.99% in purity. On the other hand, in the case of 99.9% Al containing a slight amount of impurities such as Cu, Si and Fe, the authors presume that the stress of solid solution or the difference of atomic radius of the elements must be taken into consideration. In other word, the more different the atomic radius between aluminium and the impurities such as Cu or Si is, the more easily the coarsening takes place, but it does not occur when Zn or Ag is added because the difference is much smaller. Therefore, the authors conclude that the coarsening phenomenon of aluminium of 99.9% grade is apparently related to the stress of solid solution.

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The effect of varying conditions of temperature and time of heating prior to the hot-rolling of slab ingots upon the recrystallization in cold-rolled 1 and 0.6 mm thick 2S sheets, corresponding to cold reduction in thickness of 75 and 85% respectively, was studied. The results obtained may be summarized as follows: The higher the heating temperature of the slabs, the higher the recrystallization temperature and perceptively the size of the grains, which become more isotropic. Also the deep drawing property increases exceedingly, though the elongation is lower in ingots rolled under higher temperature. Even when the heating temperature is high, if the heating time is too short, the effect of high temperature is lost. It is presumed that the condition of the mutual distribution of the elements in two phase alloys influences in these cases the recrystallization process, in respect to the nuclei and the growth of the crystals.

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The effect of Mn or Cu present in the melt upon the development of cracks was investigated by measuring the shrinkage or the cracks which appeared upon casting aluminium in the same metal moulds used in the experiment reported previously. The following results were obtained: There is a relationship of casting and mould temperature within a limited range which favors prevention of cracking, varying according to the kind and the content of the impurities. The shrinkage of the Al ingot increases with the rise in Cu contents, so that opportunities for cracking are multiplied but the effect of Cu is much smaller than that of Si. On the other hand, the shrinkage scarcely increases with the rise in Mn content. In this experiment, the cause of cracking was assumed, in a general way, to lie in the stress due to the disparity of the solidification range of the alloy, but in practical operation, the tendency to cracking is to a marked degree affected by other factors for example, the casting technique.

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The rapid determination of Nitrogen in iron and steel by Pulfrich’s photometer using color reaction of Nessler’s reagent for ammonia was studied. The sample was dissolved in H₂SO₄ or H₂SO₄-HClO₄ and oxidized by H₂O₂, then iron etc. were precipitated with NaOH aq, and separated by a centrifugal machine. Nessler’s reagent was added to this solution, and the nitrogen in iron and steel could be determined by this colorimetric method. The results obtained were as correct as those of the distillation (Kjeldahl) method. The time required for this analysis was about 30∼55 minutes. Common carbon steel was dissolved by only H₂SO₄ aq, but high alloy steel was dissolved by using H₂SO₄ and HClO₂ for treatment of the residue insoluble in H₂SO₄. The analytical values of nitrogen by the distillation method and the colorimetric method were both always lower than those obtained by the vacuum fusion method, the comparison rate being about 70∼80:100.

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High C-Cr steel is sensitive to heat-treatment. Especially, its susceptibility to hardening processes and its magnetic properties are strongly affected by its structure formed by previous annealing as has been reported by many investigators. Its structure before heat-treatment is influenced by the temperature, the time of keeping the temperature and the velocity of cooling in the annealing process for softening. The author investigated the effect of annealing temperature on the herdening quality and its magnetic properties of quenched magnetic steel containing 1% of carbon and 3.6% of chromium. The results are summarized as follows: (1) After annealing, the steel shows minimum hardness at or near the point Ac₁. The hardness decreases by raising the annealing temperature to Ac₁, but increases by a farther rise of the temperature. (2) The effect of annealing on the size of spherodized carbide shows the same tendency as that on hardness. The size reaches the maximum at the point Ac₁ upon annealing, but becomes smaller with a rise or drop from that point. (3) Hardening becomes easier as the temperature of annealing is lowered. Annealing at A₁ makes the steel most refractory against hardening. A higher annealing temperature affects the quality in a lesser degree. (4) Upon the magnetic properties after quenching and aging, the effect of annealing temperature is similar to the upon hardness.

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