The creep characteristics of tungsten of drawn 10μφ wire, annealed 10μφ wire and 0.2mmφ wire were studied in the temperature range from 1000°K to 1940°K under the stress of 121-1443gr/mm² in the vacuum of 10^-6mmHg.
Although the data obtained showed appreciable scatter, the activation energies for creep of these three kinds of wires were obtained as 140Kcal/mol., considering the effect of the recrystal lization during the creep and the effect of surface tension on decreasing the creep-rate. The obtained energy is consistent with that of self-diffusion.
From the microscopic observations of the specimens, the scatter of the data could partly be accounted for the scatter of the degree of recrystal lization and the imhomogeneity of recrystallization. It was suggested that the brittle behavior of the fracture was resulted from the pore formation during creep.

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It is difficult to measure correctly the diagonal length in the measurement of the depressed hardness and the depression has been studied as regards the measuring accuracy by many persons. In the same tester is used, there is not a little influence on the hardness of the personal error of each measurer, the difference in the illumination of depression, the enlargement in the measurement of depression and so on, besides the errors that may be prevented with care, for instance, the error in reading the scale, the trouble in the tester. The prevention of the errors is all the more important in the case of the measurement of micro-hardness because the depression is very small.
The authors have studied the surface figure of the depression, especially the piling up, and from this point we pursue the personal error in the optical measurement of the depression in the micro-hardness testing with the same tester (manufactured by Leitz Co.). The diagonal length of the same depression is measured by four measurers, one of whom is expert in using that tester, and the other three persons are unexperienced in the measurement of the hardness and operate the tester for the first time, and at the beginning of this experiment the latter three are trained twenty times in the operation of hardness tester.
As the result, it is found that there are occasions of measuring error being affected by the surface figure of depression, especially by the piling up, however large the absolute value of error may be, when the unexperienced measurer examines the hardness.
And then, a person, who has a narrow maximum deviation of the measuring value not with standing the absolute value of the error, has a reliable technique of measurement and may be able to improve rapidly as a good measurer.

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Residual stresses resulted from carburizing and quenching were measured dy the etching method, using plate specimens of two kinds of steels.
The microstructure after quenching is likely to include retained austenite due to high carbon content of the carburized layer, which may decompose into martensite in time at room temperature. To investigate the effect of aging on the distribution of residual stress, stress measurements were made on the specimens which were kept in rest at room temperature for 1, 7, 15, 23, and 30 days after quenching separately. The effect of repeated stressing on the residual stress was also examined by applying the stress amplitude below the endurance limit. Fatigue tests for the carburized specimens and those which were subjected to subsequent quenching were made to investigate the improvement of fatigue strength by quenching process.
The results obtained were as follows;
(1) Residual stresses which result from carburizing and quenching are simple thermal stress type, being compression at the surface and tension in the core. The stress reversal occurs neas the boundary between case and core.
(2) Tempering process reduces the initial residual stresses considerably.
(3) surface residual stresses tend to decrease during the aging period of seven days after quenching and then turn to increase noticeably for following fifteen days, thenceforward turning again to diminish gradually.
(4) Surface residual stresses subjected to repeated stressing decrease during the first few fraction of ten-thousands of cycles and thence turn to increase untill the most severe distribution of residual stress is developed, being followed by gradual diminution. After 10⁷ cycles they do not fade completely and have the values about 60% of the initial values.
(5) Among the fractured specimens of the fatigue test, fish eyes were recognized. Crack seems to initiate at the region slightly inside of the carburized layer, where tension peak occurs as the combined result of the bending and the residual stresses.
(6) Numbers of cycles to fracture have remarkable difference between the carburized and quenched specimens and as-carburized specimens, and accordingly surface compressive residual stresses could not be neglected in regard to their role in increasing fatigue strength.

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For nondestructively inspecting the existence of a decarburized layer and its depth in a carbon steel, we investigated the electric inspection method of tubing and bar stock.
If a steel bar stock which has a known depth of decarburized layer on its Surface is placed in the field of a exciting coil, which is energized by alternating current of high freequency, circumferential alternating current are induced in the steel bar.
These induced currents, distributed near the suface of the bar, set up a magnetic field opposing the magnetic field of the exiter. The flux density between the coil and the bar is therefore a function of the resistance of the material and of the distance from the mean path of the current with in the material.
The measurement of the magnetic flux is effetive by means of search coil located with in the magnetic flux and in close proximity to the steel bar.
The voltage induced in the search coil is measured by a valve voltmeter, and from these results the decarburized depth versus induced voltage reletionship is obtined.
Using this relationship, we can nondestructively inspect the existence of a decarburized layer and its depth in a steel bar stock.
This experiment was carried out with the specimens of 0.61% carbon steel, 12mm diameter, 155mm in length, and its decarburized depth 0-0.5mm. The experimental result obtained are as follows,
(1) When the exciting current are 40-80mA, the sensitive results are obtainable.
(2) The suitable frequency of exiting current are selected from the range of 400-1200cycle/ sec according to the depth of decarburized layers, which ranges from 0 to 0.5mm.
(3) This method is useful for picking up some decarburized ones from many heat treated parts which have same dimension.

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In order to study influence of strain ageing upon embrittlement of hightension steel sheet (as rolled, 12mm thick), we have performed V-notch Charpy impact test of pre-strained and then aged specimens.
Namely, test specimens were strained 1-10% in tension, aged at 100°C or 250°C, and then these impact values were measured at temperaturs ranging from -70°C to +100°C.
These test results showed that impact values decreased and transition temperatures increased with increasing pre-strains and progressing strain ageing.
Therefore, we must be careful to use of cold-worked high-tension steels.

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Continued from 1st report, we studied influence of strain ageing upon fatigue strength of high-tension steel sheet (as rolled, 7mm thick).
Test specimens were strained 1-10% in tension, aged at 100°C or 250°C, and then these endurance limits were measurd under completely reversed plane bending by Upton-Lewis type fatigue testing machine. Here, in order to put these tests to condition of practical use, sheet surfaces of test specimens were as rolled and not finished.
These test results showed that endurance limits of high-tension steel decreased largely with incresing pre-strains, and changed slightly with progressing strain ageing.

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In this paper, fatigue deformation of 0.37%C steel annealed, twisted plastically at room temperature, and torsional stress-aged was studied in various combinations of stress amplitude and mean stress.
Results obtained are summarized as followes:
(1) The optimum condition of torsional stress-aging in case of 0.37%C steel was a combination of 350°C and 3 minutes.
(2) The fatigue yield strength of annealed steel coincides with yield point in static tests, having no relation with the value of mean stress. And so the diagram, shows the fatigue yield strength, coincider with what has been expressed conventionally as endurance limit.
(3) The torsional stress-aged steel is more useful in preventing fatigue deformation than cold-worked one.
(4) In cold-worked and torsional stress-aged steels, the fatigue yield strength is smaller than the yield strength in static tests and the more mean stress decreases, the more fatigue deformation increases.
For this reason, it is undesirable to use these treated steels under partly or completely reversed torsion.
(5) It seems due to Bauschinger effect that in these treated steels, the fatigue yield strength under reversed torsion decreases remarkably.
Stress-aging treatment is very effective for decreasing the Bauschinger effect.

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