Internal state of the high-S free cutting steel, weighing about 4t., was examined in detail. The segregation of elements and the distribution of inclusions were thoroughly explained; the segregation was about the same degree as in ordinary steel ingots.
In the maximum positive segregation zone near the top of the ingot, all the elements were found in higher concentrations than the average value. But in the inverted V-segregation zone, S and Cu were in positive segregation, while Mn, Si and O₂ in negative and that of C was not clear enough. In the V-segregation zone, the tendency was as in the inverted V-segregation, but not so clear because of its scarcity. In the so-called negative segregation zone in the lower middle part of ingot, the concentration of S, Cu and C were lower than the average, while that of Mn, S, and O₂ were extremely high.
It was found out by microscopic examination that there were a few silicate inclusions in the inverted V-segregation zone and a great many in the negative segregation zone.
It was observed that the investigation of a high-S steel ingot would provide us an easy clue to some hitherto-undiscovered features of the segregation in an ordinary steel ingot due to the conspicuousness of segregation in the high-S steel ingot.

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The following items were investigated using the medium carbon, low Mn-Cr steels containing various amount of P, Mo and Ti.
i) Influences of the content of nitrogen in steel and the fixing nitrogen by adding Ti on the temper embrittlement.
ii) Influences of the contents of P and Mo in commercial ranges on the temper brittleness.
iii) Investigations on the temper brittleness by applying a re-tempering heat treatment.
iv) Correlation between the temper embrittlement and the impact transition temperature.
v) Correlation between the temper brittleness and the electric resistance.
And the results obtained by the investigation were as follows.
A) It was observed that the temper brittleness at lower temperature (TELT) ranging 250-350°C was an irreversible phenomena caused by the decomposition of the martensitic structure, and the mechanism of the TELT was different essentially from the temper brittleness at higher temperature (TEHT) ranging 450-550°C.
B) Effects of adding Ti to the TELT were not made clear by this experiments.
C) The TEHT was observed apparently by the re-tempering treatment ranging 500-525°C and was considered to be caused by the precipitation from the fully tempered structure, and the impact transition temperature was raised by this precipitation.
D) Increasing P content, both the impact transition temperature of the specimen treated by the tempering and re-tempering were raised, but in order to prevent this appreciable rise in these transition temperature Mo addition was very effective. was is concluded by the investigations that the impact transition temperature depended on the Mo%/P% ratio and that Mo%/P%≥10 Was needed to prevent the TEHT in these steels.
E) No correlation was observed between the temper brittleness and the electric resistance.

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In the 1st report (Tetsu to Hagané, 39, Nov. 1953, No. 11, p. 1266-1270) we described that 27Cr-5Ni-1Mo-1Cu stainless steel had good acid resistance when heat treated at the temperature range from 700° to 1100°C and that content of 10% Ni in such steels helped the formation of sigma phase, so woresened the acid resistance.
Here, we researched on the effect of decreasing the Cr content on the acid resistance in such high-Cr steels containing 5%Ni, 1%Mo & 1%Cu by the same experimental method as in the lst report. At the same time, research was made on the effect of heat treatment on the acid resistance of several austenite stainless steels which were made in Japan and foreign countries.
25Cr-5Ni-1Mo-1Cu steel had a tolerable good acid resistance when heat-treated at the temperature range from 700° to 900°C, but at 1000° and 1100°C the acid resistance worenened presenting a large γ-phase accompanying a grain growth.
In 23Cr- & 20Cr-5Ni-1Mo-1Cu steel, the acid resistance woresened initially and more at the carbide-precipitating temperature, that is, at 700° and 800°C; but at 900°, 1000°C and 1100°C the acid resistance was better by re-dissolution of carbide. Accordingly, it was presumed that lower limit of Cr content on such high-Cr steels was 25% as far as the acid resistivity is concerned.
When these steels were heated for 200 hours at 800°C, even 25Cr steel formed no sigma phase but the aggregate of α and sigma. On account of this phenomena, the acid resistance worsened, but the weight loss by corrosion showed less than 20g/m²/hr which 27Cr steel showed in the same condition. 23Cr and 20Cr steel did not form sigma or aggregate, thus the hardness and weight loss by corrosion did not vary.
The acid resistance of austenite stainless steels containing both Cu and Mo showed nearly no change by heat treatment. The weight loss by corrosion of the steels which did not contain both Mo & Cu or which contained Mo alone increased remarkably when heat-treated at the carbide-precipitation temperature.

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A more powerful and simplified method of case hardening as well as of bright annealing by the use of town-gas has been proposed. The method was to make the case hardening power of modified town gas more effective by utilizing the cyanide salts and the oxidizing constituents in a closed vessel. A new gaseous constituent C₂ N₂ O was theoretically estimated to be its important one, being illustrated by comprehensive experiments.
Steels wese oxidized by heating in the atmosphere of town-gas, but were bright-annealed or case-hardend by addition of the K₄Fe(CN)₆ over 0.5gr per litre town-gas. Carbonitriding power became maximum at 3gr. K₄Fe(NC)₆ per litre town-gas, and was reduced by addition over it, the reason being that the concentration of C₂N₂O gas, having vital effect in case hardening, became maximum at 3gr./lr.

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Instead of the usual induction or carbon spiral furnace, the carbon cylindrical furnace was used as the melting furnace in a vacuum-fusion oxygen analysis. This furnace had some strong points as compared with the other furnace; that is, easy manufacture of heating units, easy operation, high and easily controllable operating temperature and some other points. By this furnace the blank test, analyisis of standard sample, the research of operating temperature and the comparison between the Herty method and the vacuum-fusion method. The mean CO value of blank test of this furnace were 0.066cc/15min. at 1900°C and 0.029cc/15min. at 1700°C and this value were seemed to be superior than the blank value of usual carbon spiral furnace. The extrusion of Al-killed samples at 1700°C was imperfect and the extrusion at about 1900°C was required. The results of six standard samples were coincident within the value 0.0071±0.0003%.

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The present authors studied the method of accurate determination of ferrous oxide in iron ores containing arsenic, organic matter, sulphur, or vanadium and recommended the following procedures.
(1) When As^III is present, 0.5-1.0g of the sample was dissolved in 30-50cc of HCl(1+1). The solution was evaporated to abont 5cc, which eliminates As^III as AsCl₃, and made it possidle to determine FeO permanganimetrically without the effect of As^III
(2) When As^v was present, the HCl dissolution method caused an oxidation of FeII by Asv, and hence about 20cc of H₂SO₄(1+1) was used to dissolve the sample.
(3) When As^III and As^v were present, the sample was dissolved in H₂SO₄(1+1). The solution was diluted to about 400cc, and Fe++ was titrated with 0.1N NH₄VO₃ or 0.1N Ce(So₄)₂.
(4) When organic matter was present 0.5g of the sample was dissolved in 30cc of H₃PO₄(1+1). The solution was diluted to about 150cc, and Fe++ was titrated with 0.1N NH₄VO₃.
(5) When sulphide sulphur is present, 5cc of the saturated solution of HgCl₂ is added to 0.5g the sample, then 30cc of H₃PO₄(1+1) was added to it and the sample was dissolved. The solution was diluted to about 150cc and Fe++ was titrated with 0.1N NH₄VO₃.

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