The orientation and grain size of pure Mg crystals which were deformed at the degrees of 20∼60% and annealed at 640° for 1∼4 hours were examined by investigating micro-scopic structure and by X-ray analysis. The results were as follows: 1. Recrystallized grain grew abnormally at the working degree of about 45∼55%. 2. The inclination of hexagonal axis  to the direction of working was from 0° to about 30° after pressing or forging. 3. For the samples annealed at 640°, the inclination of  to the direction of working was from 0° to about 50° and for the samples grown abnormally, it was from 15° to 70°. 4. The inclination increased a few minutes after heating at 640° and aftter 1 hour it was kept at about 15∼70° to 4 hours.
The procedure of grinding of Fe in oil or benzol was observed and the results were compared with those described in the previous report (the grinding procedure in air): (1) The diffraction patterns in this case, in the stage of coarse grinding, were very sharp and in good contrast compared with the case of in-air-grinding. The reason lies in (a) the difference in the fine contour of ground surfaces of specimens, (b) the difference in the perfectness of lattice construction. (2) The oxidizing effect was much reduced compared with the case of in-air-grinding. This should be due rather to the cooling effect of liquid, than to the eftect of interception from atmosphere. (3) The extra rings (c.f. the 1st report) developed very often and very steadily in the stage of short coarse grinding, they were transferred to the reflections of Fe3O4 in the next stage of grinding. The substance giving these extra rings was unknown but supposed to be of the construction some what similar to Fe3O4.
Effects of the magnetic and sonical fields on the anodic passivation of pure iron in 1 N-HNO3 and 2 N-H2SO4 were studied. Results obtained are as follsws: (1) In the magnetic field perpendicular to the anodeplate, the passivation was retarded, but in weak field parallel to the anode it was quickened. (2) The sonical field used in the present experiment retarded the γ-Fe2O3 passivation and suppressed the Fe3O4 passivation. (3) Both the magnetic and sonical fields which are so strong as to retard the passivation fairly, make the passive films (γ-Fe2O3) resistant to dil. HNO3.
It is generally recognized that the abnormal expansion at Ar1 transformation of gray cast iron is due to the graphitization of the pearite-cementite. In the following experiments, the present authors tried to confirm quantitatively the effect of hydrogen to retard the graphitizaton of the pearite-cementite in cast iron by using the above-mentioned fact. Gray cast iron specimens, 8 mm in diameter, and 80 mm in length, were prepared from the gray cast iron castings of the size, 30 mm×30 mm×130 mm, which were made by casting the melt with varied perecnt of silicon in green sand mould. In order to measure the expansion at their Ar1 transformation, the dilatometric experiments were carried out. Soon after they were heated in air and in hydrogen, respectively, up to the temperature 50° above their Ac1 point, they were cooled. The heating and cooling rate were 10°/min, and the rate of flow of the purified hydrogen in the dilatometer was 50 cc per minute. The microstracture of the specimens was also studied. At the present stage of experiment, the effect of hydrogen to retard the graphitization of the pearite-cementite was found to be very strong and almost corresponded indegree to the effect of 2.5∼3.0 pct. silicon in favour of the graphitization in question. It was also found that A1 transformation temperature of the specimens was almost independent of the atmospheres in which they were heated.
It has been believed that the graphite nodules in white iron occur first, when it is heated, but it was known that white iron containing Si already had the small graphite nodules, when it was cast. Etching the white iron with acid, we can see only the structure of white iron as shown in Photo. 1, but by means of electrolytic etching, the small graphite nodules may be seen in the structure of white iron as shown in Photo. 2. Electrolyzing the sample with Uhlig method, the ground mass around graphite will especially be etched, therefore, even the small graphite particles may be seen. Heating the white iron, the small graphite particles will become the nuclei of temper carbon nodules and the graphitization will proceed. If the heating rate is slow, these graphite particles will grow equally and the temper carbon nodules as many as the number of the graphite particles, which was first present in the white iron, will occur (Photo. 3). But, if the heating rate is rapid, the graphitization below A1 will not proceed, therefore, the graphite particles will not grow, even when the samples reach A1. These small graphite particles disappear through Ac1 transformation, and only the relatively large graphite particles remain. Accordingly, the number of temper carbon nodules decrease (Photo. 4).
Samples prepared are shown in Table 2. The results obtained are as follows: (1) Room temperature age-hardening. Some researcher did not observe the room temperature age-hardening, but we observed it in “A 10” and “A 20” alloys. (Fig. 1 & 2). (2) Form of age-hardening curves and its activation energy. We studied age-hardening of “A 20” alloy at 30°, 50°, 70° and 90°, and obtained next results. Denoting hardening degree by p and ageing time by t, p⁄1−p is proportinal to tn, and at 50°, 70° and 90°, n=1. From these results actvation energy at these stages was calculated and obtained Q=8,200 cal/mol. (Fig. 3-5). (3) Double aging. We expected double age-hardening of these alloys as well as Al-Cu alloys, so studied it in “B 20” alloy. As expected,we could observe double aging clearly between 140° and 200°. (Fig. 6-8). (4) Relation between aging temperature T in absolute scale and the time at which the alloy at a given temperature T reaches maximum hardness. This relation was studied from the data of “B 20” alloys between 140° and 350°, and we obtained the result that logt depends linearly on 1⁄T and activation energy Q at these stages is 22,000 cal/mol. (Fig. 9). (5) Dehardening (“Rückbildung”) phenomena. We studied dehardening phenomena in “A 10” and “A 20” alloys which were aged at 30° for long time or at 150° for 5 hours. And we observed distinctly dehardening phenomena when alloys treated for very short time at the optimum temperature. (Fig. 11-20).
(1) Alloying method. First by sintering process we prepared a mother alloy of 10 per cent of chromium and 90 per cent of copper. Then it was alloyed with copper melt and we obtained copper alloys containing about 0.5 per cent of chromium. (2) Hot and cold working properties. We could deformed these alloys easily in both hot and cold states. (3) Age-hardening properties. As in the preliminary experiments, by measuring hardness change we studied age-hardening properties of cast alloys which were quenched from 950° and aged from 300° to 700° for 1 hour. The maximum. hardness was obtained with the tempering temperature of 500°. For the temperature of solution treatment, 950° is insufficient and above 1000° is nesessary. Next, for the tempering time, treating at 500° for 1 hour or 450° for 3 hours we obtained the maximum hardness. (4) Properties for electrical conductors. We made three kinds of wires (diameter 2 mm): first, after cold-drawn to 2 mm, solution treated and quenched, then tempered; second, after quenching, cold-drawn to 2 mm and tempered; third, after quenching, cold-drawn to intermediate diameter, tempered and then cold-drawn again. For example, properties obtained are as follows: (This article is not displayable. Please see full text pdf.) (5) Conclusion. For electirical conductors, this, alloy has very good conductivity, but its strength is inferior to that of alloys, such as copper-cadmium or corson alloys. However, we think there is a hope of to improving its tensile properties a little more by the modification of production process.
The stress restored in hot-work tool steel (0.3%C, 10%W, 2.5%Cr, 0.3%V) which had variously been heat treated, was measured by Nishihara’s method. The dimension of the specimen was 4 mm×10 mm×10 mm. A summary of the more important results of this work is as follows: (1) Full annealed specimen was treated……heated to 850°, kept 2 hours then slowly cooled with cooling velocity of 50°/hr. The specimen had no visible residual strees. (2) Quenched from just below the critical temperature. The specimen was kept at 750° for 40 minutes then quenched in oil. This specimen showed so called thermal stress type residual stress……compression near the surface and tension near the center. (3) Quenched in oil or air from above the critical temperature. The specimen was kept at 1200° for 40 min and then quenched in oil or in air. The max. compression remained at the surface and max. tension near the center; this was so called typical transformation stress typs. (4) Quenched and tempered state.The specimens was treated the same as mentioned above (3) and then reheated to 600° for 40 minutes, and then furnace cooled. The residual stress was reduced remarkably as shown in Fig. 3. By these treatments the specimen increased its toughness keeping max. strength or max. hardness, so that, in general, the steel is used in this state. (5) Martempered state. The specimen was heated respectively at 1200° and 1100° for 40 min, then quenched in lead bath at 500° for 40 min and then quenched oil or in air. In this state,as shown in Fig. 4. the residual stress was minima, but strength and hardness was very high as in direct quenched state.
Punching dies steel is now most widely used in mechanical and electrical industries, chifly to punch the thin Si-plate, mild steel-plate, etc. Many kinds of punching dies steels are commonly used today, but their composition are mainly of high carbon steel, low Mn-Cr-W steel, high carbon Cr steel. In the present investigation, ordinary low Mn-Cr-W steel which contains about 0.5∼1.4% of C, Mn, Cr, W were used as specimen, and the effect of the various elements, such as C, Mn, Cr and W were studied. We measured the transformation point, hardness, hot hardness, rate of deformation, toughess of these specimens, by means of different heat treatments. From the results of these investigations, we can produce a new kind of punching dies steel superior to the conventional punching dies steel.
Following the 4th report, the authers studied the abrasion test, thermal expansion coefficient, high temperature hardness, corrosion, test in comparison with the stellite and 65%Ni-Cu-Cr-Si-Fe series alloy for materials of valve seatings at high temperatureand high pressure. The results of the experiments shewed that stellite was superier to 65%Ni-Cu-Cr-Si-Fe series alloy for valve seatings.
Seven materials, such as brass, mild steel, malleable cast iron, free cutting steel, Al-Sn-Cu alloy, duralmin, and phenol-resin were chosen for solid retainer materials of No. 17203 magneto type bearings. The ball bearings constructed with these materials were tested in the spindle apparatus under no load for 150 hours. The weight decreases of the balls, retainers, and outer and inner races, were estimated after running. As the results of running tests, the most desirable materials for a solid material, were found to be such malleable metals as cast iron,brass, mild steel and Al-Sn-Cu alloy (10%Sn, 1%Cu, the rest Al). It is interesting that the pipe of the rapid malleable cast iron made by the centrifugal casting machine will easily be machined for the shaping as a retainer after a very short period of annealing.
The potassium ferrocyanide method for titrating zinc using ferrous sulphate or diphenylamine as an internal indicator requires much experience before an operator becomes skilled in its use. The author is frequently bothered to judge the end point in the titration with potassium ferrocyanide. Studing the titration of zinc, the author proposes a simple and convenient method for the titration of zinc. The method consists in precipitating zinc as sulphide with H2S using monochloracetic acid and sodium monochloracetate as a buffer solution at about pH 2.4. Zinc sulphide, thus obtained is sandy precipitate and can easily be filtered. After washing several times with water zinc sulphide is transferred to a flask with a filter paper,and it is dissolved in a definite amount of about 0.35 N HCl, followed by boiling for about 5 minutes to expel H2S. The acid solution is then cooled and diluted to about 200 cc, and the excess acid is successfully titrated with standard NaOH (about 0.35 N) using methyl orange as an indicator. The NaOH solution is standardized against pure ZnO dissolved in HCl as previously explained. Phenolphthalein cannot be used, for Zn(OH)2 begins to precipitate at about pH 6, as is shown in Fig. 1. The method is proved to be useful in analysing alloys containing zinc, such as brass and zinc duralumin.