The result of the experiment of manufacturing mullite refractories from SiO₂, Al₂O₃ type minerals was reported as follows:-
(1) The ore deposite of andalusite and cyanite in Korea.
(2) Physical and chemical properties of mullite refractories made from Korean andalusite in comparison with German sillimanite bricks.
(3) The present new mullite bricks ("Slasist A-1" bricks) has the characteristics of both silica and chamotte bricks, so that it is convinced that the former would develop more excellent results than the hitherto used silica or chamotte bricks, when used in the bottom, hearth, bosh and shaft of the blast furnace or used in the roof and gas parts of the open hearth and electric furnace.

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In the stationary basic open hearth furnace used heretofore, which has a difficulty in substituting slags, the slag usually contains more than 10% of SiO₂, so that there is a limit around 0·01% P and 0·02% S in the usual refining. However, the author made success in practising a Hoesch-system refining two times using a Merz-type open hearth furnace and managed to obtain a steel melt with 0·003-0·010% P and 0·006-0·012% S. The following are the conclusions from viewpoint of the actual operation:
(1) It is recommended to keep the CaO/SiO₂, in the slag to the second order in the first melting, to tap as soon as possible before the failure of the furnace bed, and, in the second melting, to make the highly basic slag with the CaO/Si0₂ of the fourth order as soon as possible.
(2) Therefore, a considerable quantity of fluorite should be used to retain a suitable quantity of CaF₂ in the slag.
(3) The Mn in the steel melt should be retained at least up to 0·2% in the case of the second melting, to make the desulphurization effective.

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The characteristics of the method of the electric are steel making were said to lie in that either the method oxidation or that of reduction might be selected as the chemical reaction within the furnace is processed in a closed vessel; and that there is little change in the gas atmosphere of the furnace so as to make the reaction between the metal and the slag active and as near as possible to the chemical equilibrium. In the present paper, the author dealt with the charge control for desulphurization and decarburization and breing, advantage of the method to slag off twice; and carbide and white slag method. Then the author referred to elimination of slag-inclusions, some working diagrams of the high quality steel and examination of the special steel.

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Bei der Abschreckung Cr- und Cr-Mo-Stäble kristallisiert der nalelartige Ferrit sich leicht heraus, so muss man, um ihnen hohe Festigkeit zu geben, verbältnismässig niedrige Anlesstemperaturen wählen. Der nadelartigen Ferrit haltende Stahl hat naturlich die niedrigere Kerbzähigkeit als der aus Martensit angelassene, aber der erstere steht doch dem letzteren an der Ermüdungsgrenze nicht nach.
Die Oelabschreckug, die nach der Raschabkühlung durch Wasser bei einem Temperaturgebiet, etwa 600°C, folgt, verhindert die Präzipitation des nadelartigen Ferrits und man erhält damit die gleiche Resultat betreffs der Abschreckungseffekt als die völlige Wasserabschreckung und ausserdem kann man die Härterissen vermeiden.
Aus den Ergebnissen, dass Cr-Mo-Stähle höhere Dauerstandfestigkeit und schwachere Brüchigkeitsanfälligkeit durch Langzeitserhitzung als Ni-freie Stähle haben, mag man schliessen, dass die erstere für die an der hohe Temperatur und hohem Druck ansgesetzte Scheibe vielmehr geeignet sind.

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To examine the practically useful properties of chromium and chromium-molybdenum steels now in current use as non-nickel case-hardening steels and to find the higher strength steels in substitution for the high nickel-chromium case-bardening steels (Ni₄-5%F, Cr0·5-1%), iuvestigations were made on the mechanical properties, mass effect and carburizing characteristics of chromium and chromiwu-manganese steels with 1-3% Cr. The results obtained were summarized as follows:
(1) 1-1·2% manganese increases the tensile strength of the 1% and 2% chromium-molybdenum steels without decreasing the tenacity, but more manganese diminishes the Charpy impact value while increasing the tensile strength.
(2) Some kinds of alloy steels containing 3% Cr were found to be more excellent in the mechanical properties and the mass effect than 2% Cr-Mn steels, especially the 3% Cr-Mo steels were proved to have more superior mechanical properties than 2/2% Cr-Ni-Mo steel or 3/2% Cr-Ni-Mo steel whichcontains 1-2% Ni.
(3) From the viewpoint of mass effect, the 3% Ni steel may be substituted by steels with 1% Cr or 1·5%Mn, and the 4% Ni-Cr steel by those with 2% Cr and 1% Mn.
(4) These kinds of alloy steels are apt to be subjected to over-carburizing, forming a globular carbide zone on the carburized surface which makes the case brittle. Some especially compounded carburizing agents proved to be effective in preventing the over-carburizing.

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When steels centaining chromium are treated with chlorine gas at elevated temperature, anbydrous chromic chloride is formed, which is not wholly volatilized and insoluble in water. Hence the chlorine method in determination of non-metallic inclusions in steels containing chromium has not been applied hitherto. Wasmulit reported that the insoluble chloride is removed away by washing the residues with a warm diluted solution of stannous chloride. According to the present experiment, however, the anbydrous chromic chloride is not dissolved completely by such a procedure and it is necessary to use a fairly concentrated solution of chromous ions.
A satisfactory method, therefore, was proposed by the present writer; that is, the residue after chlorination is treated with a concentrated chromous chloride solution prepared by the following method. 5g K₂Cr₂O₇ was dissolved in 100cc HCl (1:1), and reduced to chromic state with alcohol and then re uced to chromous state with 5g zinc in nitrogen atmosphere. Considerable amount of HCl used are consumed in arising KCl, CrCl₂ and ZnCl₂, and the resulting concentration of HCl is less than 5%, so that the non-metallic inclusions are not dissolved away.
The aforementioned modified chlorine method was applied to various engineering alloy steels containing chromium, such as 1% chromium steels, nickel-chromium steels, chromium-molybdenium steels, high carbon chromium steels, nitriding steels and stainless steels, and satisfactory results were obtained. The total oxygen content determined by the chlorine method well coincides with that of vacuum fusion method.

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