It is known already that when steel or cast iron was decarburized at the temperature as 800°C., there appears fine ferrite layer on its peripheral zone, but little is known why such a layer appears.
The writer treated this problem based on carbon diffusion in ferrite as in austenite, and explained the mechanism of the decarburization at such a low temperature by mathmatical method.
On the other hand the writer observed the influence of chemical compositions on the thickness of ferrite layer, and found the influence of chemical compositions are very sensuous.

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Up to the present, the investigation on diffusion of various elements into molten steel is very scanty, notwithstanding the subject is very important for the manufacture of special steels. The authors took the Swedish Carbon-steel wtth 0.3% C and the home made Nickel-steel with 3.29% Ni and 0.27% C as base materials. From them cylindrical samples 17mm dia. and 60mm long were prepared; and at their upper or lower part bores were spared, in which various elements as metals or ferro-alloys are to be enclosed. Thus prepared samples are molten in Tammann tubes and held at 1, 500°-1, 700°C during 10 or 20 minutes, as the case may be. They are slowly cooled and cut longitudinally along the centre line, polished and the hardness on their sections is measured along 12 horizontal lines 5mm apart by Rockwell and Schore hardness testers. The mean values of the hardness numbers on each line are plotted according to the height of the samples, and thus we get the hardness curves. From these hardness curves with their micrographs we could judge the manner of diffusion of various elements.
As we expected, it depends upon the various factors as melting points of elements of ferro-alloys, temperature of the molten bath, position of enclosure according to their specific gravities, time kept at constant temperatures, etc.
We found the conditions necessary for the uniform diffusion of various elements as Molybdenum, Nickel, Manganese, Chrome, Phosphorus, Vanadium, Titanium, Silicon and Carbon in both steels and also the interesting characteristics of the three elements Manganese, Titanium and Carbon in diffusion. Lastly we could not find any appreciable difference in diffusion of high- and low-carbon ferro-chromes or metallic chrome.

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The authors have previously published a paper on eutectoid transformation inAl-Zn alloys, in which the mechanism of the transformation was closely studied and a stepped transformation, β→β'→α+r, was proposed. (This Journal, vol. 10, 1934, p. 718; Mem. Ryojun Coll., Eng., Inouye vol., 1934, p 83) Now in this paper, small quantities of Mg 0.002%-0.3%, were added to specimens, nearly of the eutectoid composition and the effects of Mg on the said transformation were studied. The experiments were carried out on quenched specimens by means of hardness, electric. resistance and dilatation methods. So small a quantity of Mg, 0.002%-0.006% retards the changes remarkably, but still even in the case of 0.3% alloy some changes of properties were observed by ageing at room temperature On the other hand, the unusual characteristic of the intermediate structure, which appears by tempering at 100°-150°, fades away owing to the presence of Mg. This effect is most remarkably observed between 0.01% and 0.02%, of Mg-content, which shows that the presence of Mg causes some important changes in the inner parts of the crystal lattice. (This paper was read at the 12th General Meeting, 1934, of this Institute).

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The author has measured the fluidity of the casting aluminium alloys, namely No.12 alloy, Lautal, Silumin, Al-Zn (25%) alloy, German alloy and Y-alloy. After the molton alloys were cast into the special mould (see Fig.1) under constant conditions, he determined a spiral length filling up with alloys and assumed that its spiral length shows testing alloy's fluidity at that tem-perature.
From the results of the above test, he can find that Silumin is good fuidity No.12 alloy, Lautal, German alloy, and Y-alloy, are next to Silumin, but Al-Zn (25%) alloy as compared with the above five kinds alloys is inferior fluidity.

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