The present report is the result of the preliminary research for industrialization and the semi-industrial test for manufacturing sponge iron from a hematite with Iittle silica; and the result of aetual melting tegt for the application of hematite to the basic electric arc furnace. Hematite ore was prepared in particles with the size 3-15mm and reduced at about 1000°C with coal, consequently yielding a sponge iron of which the metallic iron is 70-80% and the reduction rate above 90%.
When the hematite was used for the charge into the electric arc furnace. about 10% increase in electric power and melting hours was observed than in the all-scrap method. The product was found to be of good quality.

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Dor Mechanismus des isothermen Austenitzerfalls des Sonderstahles ist sehr kom- pliziert und manche Untersuchungen sind dazu gewidmet. Vor allem ist der Zusammenhang zwischen dem Zerfallsprozess und der Kühlgeschwindigkeit eingehend untersucht, aber man hat nicht so genuge Ergebnisse daraus gewinnen gekonnt. Anderseits ist die Forschung des isothermen Austenitzerfalls in jedem Lande labhaft geworden und verschiedene undeutliche Punkte sind schon damit klargemacht.
Die Methode der S-Kurve, nach der man in Amerika allgemein verfährt, ist nichts anderes als eine kunstvolle Zusammenstellung des isothermen Austenitzerfalls. Die S-Kurve gibt uns die anschauliche Darstellung des Austenitzerfalls und hat nicht den theoretischen, sondern vielmehr den praktischen Wert Denn der Chrakter der S-Kurve ist ihre Anschaulichtkeit, mit dem man die Zerfallsprozesse bei verschiedenen Wärmebehandlungen verstehen kann, aber es ist nur praktisch erlaubt und theoretisch nicht erlaubt, dass man direkt den bei Wärmebehandlung vorgehenden heterothermen Austenitzerfall auf der S-Kurve bezieht, wie manche Forscher getan haben. Der Verfasser stellt diesen Zusammenhang mit dem in Deutschland untersuchten Additionsregel fest, und äussert einige interessante Anwendungen.
Hauptsächlich ist der bei einer Wärmebehandlung vorgegangene Austenitzerfall das Integral der differentialen isothermen Austenitzerfälle. So ist die genaue Kenntnis der isothermen Austenitzerfalls die notwendige und genaue Bedingung, unter der man in dem Austenitzerfall bewandert ist.

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Heretofore the analysis of the iron oxide contained in sponge iron-has been cond- ucted in-general by the "mercuric chloride method", which consists in first dissolving the metallic iron in the mercuric chloride solution, then eliminating the metallic mercury in the residue with alcoholic solution of iodine or chlorine gas and finally determining the residual iron oxide.
The present method tried by the author is that of dissolving the metallic iron in the aqueous iodine solution instead of mercuric chloride solution, determining the iron oxide in the residue, and comparing the result with that obtained by the abovementioned method, The result agreed satisfactorily with the mercuric chloride method, which had been recognized to be the most accurate, and showed that the iron oxide may be determined simply and precisely by the present method.

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It is absolutely necessary for the practice in the melting plant to measure precisely temperatures of the molten steel in the furnace, of tapping and of casting so as to attain to the excellent products. To solve the present problem, an apparatws usiug the WC/C thermocouple has been devised, which was explained in the first and the second report. However, the WC/C thermocouple revealed some draw backs such as the difficulty in obtaining uniform quality in the available materials and the necessity in exchanging the protection tube for the hot junction in each measurement. Therefore further research was made in the line of the W/Mo thermocouple, inventing a special coating method to prevent the oxidation, using a silicon carbide-coated carbon tube as the protection for the direct contact with the liquid steel, thus developing an apparatus sufficiently applicable in the practice. The new apparatus is made of materials easily available and of low cost. Besides, the method of application is simple, free frompersonal errors and so it is suitable for the actual operation.
As results of the application of the apparatus to the practice, it became possible to measure precisely the temperature change during operation in the high frequency and the open hearth furnace, and the temperature distribution in the atmosphere and the melt in the oppn hearth and the are furnace, thus disclosing some facts unknown in the past. Above all, it was explained in mathematical figures that there is a more remarkable local difference in temperatures between the point just below the arc and the furnace-bottom (or the furnace-wall) in the melt of the arc furnace owing to the orign of heating when compared with the case in the open hearth furnace. Some consideration should be made regarding such remarkable facts for the guide of actual operations. It is extremely necessary for the manufacture of good quality steels and for preventing waste products to measure the temperature of the melt exactly and to control the temperature-measurement reasonably during the melting operation. It is expected that the present thermocouple would contribute so much to the future practice in general.

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