The standard creep limits are not yet determined in our country, and this report was made so as to give some contributions for its determination. Using the author's simple creep tester⁽⁹⁾, 13 kinds of definitions for creep limits as in Table 1, were experimentally compared. The experiments were done with four kinds of metals as given in Table 2 and at temperatures between 300° and 700°. The creep diagrams obtained are shown in Figs. 2 to 19, and the creep limits were calculated as given in, Table 3 to 7, within the error of 1kg/mm². The creep limits can be rearranged in the next numerical order, which shows the mean percentage by taking K W I No. 1 as 100%.
(1) Simidu No. 3 180% (6) Frank. Bureau Veritas 75%
(2) Mitubisi, Sunaga 120% (7) Sasagawa's & Engl. Hatfield's Method <50%
(3) Sumitomo and K W I No. 1 100% (8) Siebel & Ulrich's Method 80%
(4) K W I, No. 2, No. 3 95% (9) Juretzek and Sauerward's Method 90%
(5) Germany DVM
Swiss
Author.} 90%
From the point of view of accuracy and easiness of the experiment, the definitions in the groups (3), (4) and (5) are the most recommendable.

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High speed steel is today playing a very important role in the improvement of the efficiency of mechanical industries, particularly in the field of cutting tools. The composition taken for the investigation was either 18-4-1 or 14-4-2, to which cobalt is added to improve the durability for cutting power. This property is not only dependent upon the qualities of raw materials, production process, composition, etc., but also much upon heat treatments. The writer carried out a series of experiments with five varieties of typical high speed steel of different cobalt contents and studied changes in their hardness and microstructures brought about by the quenching temperature, holding time and tempering temperature, etc., and also tested their durability by putting them in actual service.
The results of this experiment areas follows:- (1) Quenching temperature necessary for the maximum hardness will be lowered as the cobalt content increases, (2) In the case of low quenching temperature, higher in hardness and durability for cutting power will be obtained by holding the steel longer at the quenching temperature. (3) When the hardening process is.repeated, the austenite crystals grow larger and the hardness becomes less. (4) The maximum hardness obtained by the tempering increases as the increase of cobalt content and the rise of quenching temperature, while its tempering temperature shifts somewhat to the higher side, (5) The durability for cutting power increases as the quenching temperature becomes higher and as the cobalt content increases, there is a moderate tempering temperature for each high speed steel.

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Die Untersuchung der Leichtmetall-Lagerwerkstoffes ist von alters hergetan. Es-gibt zahlreiche Legierungen, die in Literaturen vorgestellt rind. Etwas von deser sind für den Flügmotoren zur praktischen Anwendung gebracht. Aber sie stehen der Bleibronzen die gegenwärtigen Lagerwerkstoffe sind, an der Laufeigenschaft nach. Wir konnten bei dieser Untersuchung bessere Legierungen als bisher bekannten Al-Legierungen erforschen. Dieser Legierungen haben die folgenden Zusammensetzung:
Al 80_??_90%, Sn 9_??_15% Cu, Ni, Ti, Mn 0.05_??_3.0% jeder für sich. Nach der vergleichende Prüfung der Verschleissfestigkeit gegen verschiedenen gegenwärtigen Lagerwerkstoffe ist die Verschleissfestigleit besser als gegenwärtigen. Wir betrachten these Al-Legierung als hoffnungsvallen Lagerwerkstoff.

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The author has studied the magnitude and distribution of internal stresses set up during the heat-treatment of aluminium alloys with special referrence to 25 S.
As the quenching media, three different rates of cooling by water, namely at 20, 50, and 100°, and by rape-seed oil at 20° were selected. The stresses induced by quenching in water at 20° proved to be the maximum and in boiling water the minimum. The trouble, however, is that the internal stresses cannot be reduced without simultaneously decreasing the mechanical properties which results a maximum of internal stresses. For 25 S-alloy the soy-bean oil at 20° gave the most beneficial effects, where neither remarkable decrease in the optimum strength nor dangerous amount of internal stress was found. Although the tempering following quenching indicates the limited removal of stresses, its amount is very small comparing with those when quenched in any adequate medium. The stresses seems to be more or less increased by heating at 170°, probably on account of the new stresses induced by precipitation phenomenon.
The resistance to corrosion is lowered with the increasing temperature of the tempering and quenching medium. It is also affected by the various kinds of medium.
The investigations were carried out by several other aluminium alloys and the possibility of relieving the internal stresses without giving deleterious effect on the properties of metals has been proved.

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