Since a long time in Japan, magnetic iron sand was treated in a low furnace with charcoal, and heavy mass of iron bear thus produce 1, about 3-4 tons in weight, was broken up to small piec s. They are sorted into several kinds, according to their own hardness Their chemical compositions are very pure, low in sulphur and phosphorus. The original sands having pret'y rich coutents of those elements, the author proposes in this paper the liquation theory p. evailing in the bottom of furnace to explain this fact.

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In the production of the white heart malleable cast iron, in practice, close puck the white cast iron in a furnace with some iron oxide, and anneal for a long time at a high temperature. To study the mechanism of the decarburisation of the cast iron, two different phenomena; the action of the gases in the furnace and the migration of the carbon in the cast iron; shoud be demonstrated. This first report is the study of the action of the gases in the furnace, and the phenomenon about the migration of carbon may be published on the second report.
The decarburisation of the cast iron in the furnace be taken place on the meaning of the oxidation of the carbon in the cast iron and the reduction of the iron oxide by the intermediating action of the carbon monoxide and the carbon dioxide.
The writer has studied the act on of the mixed gases of the carbon monoxide and the carbon dioxide on the decarburisation in their many different rates of composition, and further studied the change of the components of the gases in furnace during the annealing. And by these experimental results, the writer confirmed the action of the gases in the furnace to be explained by the chemical equilibrium of the iron-carbon-oxygen.

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Up to this time shear blade is generally made of oil-quenched high carbon steel. The most difficult treatment of this work is hardening process. In the case of quenching of it, long and flat section, there results a strain of heat treatment especially at A 1 transformation point. To lessen this strain it must be heated uniformly in hanging state, and immersed in oil-bath slowly and straightly. For this purposes we designed the vertical electric resistance furnace. But now there is a tendency of using special steel instead of high carbon steel. The most favourable material for shearblade of least strain, proper hardness and long life is self-hardening steel.
The chemical composition of it is as follows:
This special steel has an excellent property of self hardening, 500-600 B.H.N. only by air cooling, so there is no need or oil quenching.

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The author studied on the viscsosity of slag from an acid and basic open heauth furnace in molten state, with a measuring apparatus for viscosity based on a rotating cylinder method. In this experiment, as any refractory material is attacked by molten slag from a steel furnace, especially by basic slag. he used a rotating cylinder covered with platinum and a Platinum crucible, and measured the temperature up to 1, 600°C, steeping a Pt-Pt·Rh thermo couple directly in the slag.
Unlike iron, the change of the viscosity of steel furnace slag highly depends on temperature, and the slag does not present the distinct temperature of primary crystalization, acid open hearth furnace slag is far more viscous than basic one.
When the amount of FeO increases in acid open hearth furnace slag, its melting temperature becomes low, and its viscosity weak; whill, MnO malses the melting temperature of the slag high and the viscosity weak.
The melting temperature of fayalite (FeO·SiO₂) obtained by viscosity curve is 1, 360°C, that of Rhodonite (MnO·SiO₂) is 1, 255°C, and that of tephroite (2MnO·SiO₂) is about 1, 270°C, They are all weak in viscosity, and their change in viscosity influenced by temperature is comparatively small. As for viscosity cuwe, in rhodonite it is rather inclined., but in the rest it is nearly horizontal.
Making the sum of FeO and MnO about 24%, and CaO, MgO, SiO₂ and Al₂O₃ constant, the author measurtd the viscosity of artificsal steel furnace slag, in which FeO and MnO were reflaced each other. The slag rich in FeO is weak in viscosity and low in melting temperature, but the more there is MnO ir the slag, the stronger its viscosity and the higher its melting temperature,
Different views have been held as to the action of fluorspar in the open hearth slag, The present author ascertained the relation between the viscosity of molten slag and the amount of fluorine in it. 0.1-0.4°% F was found in 10 basic open hearth slags. The amount of spar added to the slag is 0.3-5% of the latter and 15-16% CaF₂ of the spar is present in the slag. Spar makes the viscosity of basic open hearth slag weak, and the melting temperature remarkably low. 1% F makes the melting temperature low about 100°C Examining the analytical results of slags which were added with spar, the losses of F anb Si correspand to the ratio SiF₄.
Six artificial slag were plepared maintaining the sum of CaO, MgO and MnO about 61%, other constituents constant, and replaceng MnO by MgO and CaO from 0.32 to 13.64%, and there viscosity was measured. MnO makes viscosity weak and melting temperature low. if 1% of CaO+MgO is replared by MnO, the melting temperature of the slag decrease about 12°C,
Further, making the sum of CaO and MgO aboat 36% and MnO, FeO and Al₂O₃ constant, the autnor measured the viscosity of these 5 artificeal slags, in which CaO and MgO were replaced each other. The slag rich in MgO is weak a little in viscogity, and remarkably high in melting temperature. If 12 of CaO is replaced by MgO, the melting temperature of the slag decreases ab. ut 14°C.

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