Iron ores used in a blast furnace are subjected to various changes. In this connections, a series of chemical investigations have been informed, nevertheless few physical investigations. Of course, just as the reducibility of iron ore is much influenced by its chemical composition and the conditions of reducing gas, some physical properties such as porosity, expansion, shrinkage, softening temperatuer under load and crushing strength at high temperature, have great influence on the reducing property. Thus, various iron ores occured in different districts as Nippon, Korea, Manchuria, China and some districts of the South Seas were measured relating to the following properties:
1. Expansion and shrinkage at high temperatures (in air and in reducing gas).
2. Softening temperature under load (in air and in reducing gas).
3. Crushing strength at high temperatures.
4. Permeability to gas.
5. Thermal analysis.
6. Conductivity of heat at high temperatures.
7. Chemical compositions and microscopic structure.

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The author commenced the experiment of manufacturing sponge iron by the use of rotary furnace in March 1938 (Showa-15), continued it to March 1939 (Showa-16) and began to manufacture industrially since May 1939. The following is the result of the experimental working informed as the second report.
The most difficult point in conducting various methods of manufacturing iron by the use of rotary furnace is the problem of refractory materials. Happily the manufacturing operation of the sponge iron is conducted at temperatures from 1000°C as maximum to 900-950°C, so that there is no fear of suspension of the operation by the limited life of the refractory bricks.
The rotary furnace used at present is of small size, so that the operation is easy and the product with the reduction grade of above 90% are continuously manufactured.
Improvements in operating the furnace since then were as follows:
A) 1. Equipping the measuring meters, and measurement of the temperature of the furnace walls and the furnace gases.
2. Measurement of the blast quantity.
3. Equipment of extracting the sample in the middle of the furnace.
4. Improvements in the method of extracting of the analysis sample of the furnace gases.
B) Justification of the passing time of the charge, increase of the production capacity and the stabilization of the manufacturing operation by modifying the inner form of the furnace.
The effect of the reducing agents on the reduction rate of the product is important, and it needs the more fixed carbon and the proper grain size. Impurities in the products are eliminated by simple operation. 30-40% of MnO etc. have been excluded when examined from the result of the experiment.
Moreover, the author reported on the result of the melting test of sponge iron that had been conducted for a long time since the experiment of the first report.

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Im ersten Bericht wurde die allgemeine Angabe uber den isothermen Austenitzerfall geaussert. Der Verfasser hat diesmal die Ergebnisse von der Untersuchung uber den isothermen Austenitzerfall einiger Stahlarten aufgestellt. Der S-Kurve des Ni-Cr-Stahles und die des Cr-Mo-Stahles verden zuerst gesucht und ihre Massenwirkungen werden damit abgeschatzt. Ferner erwahnt der Verfasser kurz des Ni-Cr-Mo-Stahles und des nickelarmen Mn-Cr-Mo-Stahles. Die Gefuge der bei verschiedenen Temperaturen isothermisch zerfallenden Proben werden der Reihe nach gezeichnet. Zum Schluss werden die mechanischen Eigenschaften des isothermisch zerfallenden Ni-Cr-Mo-Stahles gepruft und das sogenannte "Austemper-Verfahren" beim Sonderstabl wird beurteilt.

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Begriffsbestimmung des Automatenstahles. Unentbehrlichkeit des Automatenstahles fur die Schnellarbeiten mit den Werkzeugmaschinen. Beziehung der Zersapanbarkeit des Werkstoffes auf die Bearbeitung mit den Werkzeugmaschienen. Allgemeiner Einfluss verschiedner Elemente auf die Zerspanbarkeit des gewohnlichen Stahles. Einteilung der Automatenstahlen. Vorteile beim Anwenden von Automatenstahlen undihre Verwendungsgebiete. Birnenverfahren und die Herstellung von Automatenstahl. Dringende Notwendingkeit der Forderung und Verbreitung von Automatenstahlen. Schluss. Schrifttum.

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Many efforts have been devoted to utilize high chromium steel turning scraps since the high chromium steel were widely used in the engineering field, but no report of great success has been heard yet owing to the difficulty to overcome the easy oxidation of chromium and picking up carbon from the residual cutting oil on the surface of turning scraps. It is essential to reduce the carbon content as low as possible to maintain good mechanical properties and machinability. The authors have carried out several experiments to find the most suitable method for cleaning the turning scrap on the point of view to keep the picked up carbon as low as possible and also gave some suggestions to utilize the products.

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The report deals with some results of the author's experiments on the electrolytic polishing of the quenched 1.0% carbon steel. The experiments were performed according to the wall known Jacquet's method. Seeing from the results of numerous tests, the author proposed the following tentative recommendation to develop the mirror-like surface of the steel:
(1) Anode: A test piece as anode, vertically set parallel to the cathode about 25mm apart.
(2) Cathode: Aluminium plate, the cathode surface area being about 12 times of the polished surface.
(3) Electrolyte: (75% of anhydrous acetic acid solution)+(20% of the 60% perchloric acid solution)+(5% of distilled water).
(4) Current density of the anode: 7.0-8.0 Amp/dm².
(5) Solution temperatare: 15°C.
(6) Polishing time: 5-15min.
(7) Fe-content in the electrolyte: 1.6-6.3g/l.
(8) Agitation velocity: Comparatively slow (an agitator being used.)
The conditions above mentioned are not applicable to other steels, such as annealed carbon steel, high speed steel and high-carbon and high-chromium die steel, to obtain mirror-like surfaces, but sufficient to develop their microstructures.

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