A small piece of Swedish pig iron was melted down at 1250°C in the Porcelain tube passing through the purified hydrogen gas. Keeping the temperature at constant, the tube was evacuated and then hydrogen was refilled. The procedure was repeated from 1 to 40 times. With. an inerease of the times of repetition, graphite flakes grew up longer in length and the content increased. When repeated to a certain extent, graphite flakes became shorter in length and the content decreased. At last, graphite disappeared and the long fine cementite crystals appeared. After the pig iron was melted and purified with this procedure, the hydrogen was replaced respectively by CO, CO₂, O₂ and N₂ and allowed to coal. All of CO, CO₂ and O₂ gave rise to the fine eutectic graphite structure and in the cases of the first two the combined carbon was little formed but in the last the secondary cementite existed in pearlite. N₂ gave rise to the straight graphite flakes and e ground mass was wholly pearlitic. When CO coexisted with H₂ or N₂, or with both of them it promoted the further growth of graphite flakes and N₂ in this case made the graphite flakes straight also.

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The author applied oreng in melting cast iron in an electric furnace with silicious lining to lower a certain extent hydorgen aud silicon contents in the bath, so as to get sound castings free from blow holes and of the better mechanical properties. When oreing had been excuted in presence of acid slag containing carbon just after melt down, decarbonization and other undesirable influence of oxygen were not only perceived, but increasing tendency of carbon content due to violent reaction between slag and molten iron during boiling period. To get a satisfactory result by oreing operation it was necessary to keep followng conditions correctly for prevention of excessive oxidation; that is, high silicon (>2%), low heat, and suitable degree of oreing. followed by reducing reaction.

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Recently, cracking oftire flanges has often been experienced. As a result of a metallograplrical study, the authors have concluded that such a trouble is caused in the following way:
i) The surface of a tire (flange and tread) is heated above Ac1 repeatedly by brake-heating and then cooled rapidly. In this way the surface is hardened and shows martensitic structure.
ii) Further, the surface is tempered by a second brake-heating (below Ac₁) and shows tempered (troostite or sorbite) structure. Such hardening and tempering are repeated.
iii) The hardened and tempered zone, called "brake burn" or "affected zone", produced by such a process is always accompanied by hair cracks (tempered cracks).
iv) Flange cracks are caused by the hair cracks with repeated alternative stresses occuring while the tire is rolling.

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An important role is played by hot working tool steels such as die, Container and ram etc. employing for Extrusion and Crank Presses to manufacture ferrous and non-ferrous metal tubes and rods. These steels are suffering from intermitent heating at high temperature (400-650°C), wear and repeated sudden temperature changes by heating and cooling. We investigated the effects of some alloying elements and carbon content on the standard W-Cr-V-Steel and mechanical properties at room and high temperatures.

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Following the 7th. report (Tetsu to Hagane; May 1949, p. 9-13), the author studied on the rapid method of discrimination of the elements of the various high speed steels by spark testing.
Moreover, the author studied on the hardness, abrasion and cutting efficiency of 18-4-1 standard high speed steel, by means of nitriding of ammonium gas at 550°-600°C

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Castings Division, one of the Investigation Committees of the Iron and Steel Institute of Japan has been adopting the investigations on mould and roll. Four times of meeting were held during the one year, from the summer of 1948 to that of 1949. Outline of the meeting is described in this report. The chief subjects of Investigation Committee on Mould are those on chemical compositions of mould, effect of annealing on the life of mould, mould of cast steel, microscopic . structure and its classification, classification of the causes of disusing mould, and thickness of mould. While, the chief subjects of Investigation Committee on Roll are those on the improvement of the hardness of chilled roll, standardization of hardness tester, the method of measuring the depth of chill part of chilled roll, chemical compositions of rolls for various use, and inspection on the results of using roll of special materials.

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Data published so far and some results obtained in the author's laboratory are outlined. Spheroidization of graphite in iron can be achieved in the wide range of composition: C 2.4-4.2%, Si 0.8-6.0%, Mn 0-1.0%, P<1.0%, S<0.2%, although Mn<0.4%, P<0.05% and Si 2.0-3.5% are needed for the high ductility of the iron as cast. The total carbon content must be 3.5% plus in order to avoid the high shrinkage in casting, but C 4.0% plus sometimes causes the flotation of graphite in massive castings. The less the sulphur content is, the easier the spheroidization becomes.
In irons treated with magnesium, it is probably adsorbed on the surface of the graphite nodules precipitated from melt, but the binding condition of Mg atoms in irons obtained by tempering the white irons of the same melt differs from that in nodular irons as cast.
The chemical, physical and mechanical properties are varied in the wide range by the chemical composition and the microstructure of the ground mass embeded with the spheroidal graphite. The irons are stronger and tougher than the ordinary gray iron, and have generally both markedshock resistance and heat resistance.

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