The behavior of oxygen during refining process is most important and fundamental reaction. Many investigations on the oxygen had been studied with the pure system, but investigation on the behavior of the oxygen during refining process of steel had not been studied.
The authors studied on the mechanism of operation of oxygen against the bath during oxidizing period in the acid open-hearth furnace process by the limestone method.
Most of oxygen (about 60-70%) operated for the bath through the oxidizing period were supplied from the additional ore and about 30% oxygen came from atmosphere in the furnace and then small quantity of it were supplied from the iron oxide in the slag.
Therefore it was possible to calculate the slag weight by compositions of slag at the above mentioned times and the amount of additional limestone, and to calculate the iron oxide weight from the slag weight and the concentration of iron oxide in the slag.
Effect of the oxygen from ore were influenced by CaO/SiO₂ in the slag. If CaO/SiOSiO₂ increased its effect was rapid, and the oxygen from atmosphere was influenced strongly by physical conditions of the slag (for instance, thickness, disturbance of surface etc.) in comparision with chemical composition of it (for instance, FeO and MnO content, CaO/SiOSiO₂ etc.). The oxygen supplied from the iron oxide in the slag were influenced by the chemical slag conditions, the amount of additional limestone and the temperature.
Most of oxygen (about 75%) which had been sent into the bath were used for oxidation of carbon and about 20% and 3% of it were used for oxidation of silicon and manganese respectively.
The oxygen from the ore was calculated by the amount of the additional are and its composition, and the oxygen from slag was calculated from variation of the iron oxide weight in the slags and so the remaining oxygen must have come from atmosphere.
The method of calculation of the iron oxide weight in the slag was as follows:
If the slag weight at melt-down, before addition of limestone and in the last stage of oxidizing period respectively was expressed by X, Y, Z and the CaO and MnO concentration in the slag at the abovementioned times expressed by X_CaO, Y_CaO, Z_CaO, X_MnO, Y_Mno, and Z_MnO respectively,
where a= amount of additional limestone.
But the absolute MnO content in the slag had no change through the period of limestone addition.
And then because the absolute CaO content in the slag at melt-down and before addition of limestone was equal.

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This report treated of the results of studying the formula of calculating the scaling loss of rolled carbon steel based on the oxidation degree, on the correlation among shapes, size and the scaling loss of rolled steel and on the scale-off depth of steel surface due to oxidation at high temperature in the case of several degrees of heating temperature and heating rate.
A formula was set up, by which the scaling loss could be calculated by applying an empirical formula showing the relation between temperature and oxidation degree mentioned in the previous report. The relation between the scaling loss and the shape and size of heated steel could be expressed in a simple formula.
The formula of y=A.t^B, B<0 was set up by which the approximate value of oxidation degree (y, g/cm²) could be calculated by applying it to several degrees of heating temperature and heating rate (t, °C/min), if the temperature of extracting ingots and the time of keeping it in the furnace were known. The formula D=1/(f-1)×y/7.8 was obtained, by which the scale-off depth (D, cm) due to oxidation at high temperature in the furnace could be calculated, and the correlation between the oxidation degree, the heating temperature, the heating rate and the scale-off depth was made clear. Then some consideration was given to the relation between. the scaling and defects in rolled products.

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A type of miniature test casting was devised as the means of investigating the influence of chemical composition of cast steel upon hot-tearing tendency. The test casting consisted of a 40mm diameter vertical cylinder with four horizontal and radial branches, each 70mm long.
The casting wheighed so small as 2kg that it could be poured from an ordinary sampling spoon.
Mould cavity for each branch was made of a 8mm I.D. quartz tube, one end of which penetrated into the central mould cavity for the vertical cylinder, the depth of penetration being 10mm.
The contraction of the branch was restrained by a steel pipe which was inserted in between the vertical cylinder and a small flange at the outer end of the branch. This restrained contraction caused a complete or incomplete hot-tearing at the junction of the branch and the vertical cylinder. The hot-tearing tendency of a cast steel could be evaluated from the load required for the fracture of the branch at room temperature and also from the area of hot-tear on the fractured surface, provided that the mechanical and thermal variables of the casting were kept constant.
Reproducibility and sensitivity of the result were satisfactory. For example the difference between hot-tearing tendencies of two heats of steel containing 0.020% and 0.030% sulphur respectively could be discerned clearly by pouring only a pair of spoon samples of steel. Although the test casting was very small in size, the cooling of the portion where hot-tearing occurred was as slow as that of a 40mm diameter cylinder casting or of a 20mm thick plate casting. So the results of investigation by this test casting might well be applied to castings having wall-thickness of 10-30mm. Another significant advantage of this method was that there was only a limited amount of oxide film or scale formed on the surface of hot-tears, so that it was possible to examine more precisely the microscopic appearance of hot-tears in various types of steel castings.

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For the purpose of stress-relief in the induction surface-hardening the martempering was superior to the tempering at low temperature. However, the surface of martempered steel was stained with salt, therefore the martempering could not be applied to the induction surface-hardening.
Fortunately, the induction surface-hardening was operated automatically by the magnetic relay. As soon as the water-cooling of the induction surface-hardening was stopped, before the induction heated specimen was completely cooled down to the temperature of water, this specimen was cooled in air or oil, and the effects similar to that of the martempering on the induction surface hardening were obtained. For this purpose, the experiments were carried out with a 0.44% C-0.92% Cr steel.

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Many materials were studied hitherto by the authors as the spring materials for high temperatures, and these results were reported in Tetsu-to-Hagané as the 1st to the 4th reports.
In the 4th report, it was recognized that from the experimental results of microscopic structure, hardness, tensile strength and elongation, the material corresponding to a die steel No. 5 was found superior when treated at a constant temperature to which it had been treated with ordinary quench-temper method.
This time, the results of the test on tensile strength, elongation and microscopic structure at high temperatures upto 500°C were summarized as follows.
(1) In comparison with the ordinary quench-tempered material, the material which had been quenched at 1100°C and treated at constant temperatures of 350°C and 600°C was superior.
(2) From the result of studying the effect of holding time, remarkable differences were not recognized with the materials which had been treated at the constant temperature upto 500°C affecting the holding time.
(3) From result of the effect of the holding time at 500°C for 240min., the properties of the material were recognized to be changed but a little.
(4) The die steel No. 5, when treated at a constant temperature was considered superior as spring material for high-temperature uses upto 500°C.

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The Ni, Cr and Co are very important for the heat-resisting steels, so by the latest information a comparatively vast quantity of Ni and Co were used for the heat-resisting steel.
But Ni and Co were of high price and very scanty in Japan, so the authors examined them for the purpose of curtailing these elements.
The authors first examined the change of their hardness due to various heat-treatments of each sample: i.e. solid-solution treatment and aging, and then observed the microstructure.
As the results of these experiments, they gave the most moderate composition and heat-treatment for Ni-Cr-Co austenitic heat-resisting steel, concluding that (1) the best composition contained Ni 13-15%, Cr 20-25%, Co 10-15% (2) The solution-treatment was made at 1200-1250°C, and the aging temperature was 700-750°C, the aging time being 6-12 hours.

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In the present report, the results of investigation about the influence of various elements (C, Si, Mn, P, S, Cu, Ni, Cr, Mo, W, Sn, Al, Co, V, and As) upon the structure of the cast iron which solidified at a definite cooling-rate after treated with the slag containing titanium oxide under the most suitable conditions for producing eutectic graphite structure as described in the second report (Tetsu-to-Hagané, 39, 1958, 984). It was found that the effect of Ni and W were very favorable, and that the S and the Al were harmful elements. When other elements were contained in the specimen of cast iron in such an amount as contained in a cast iron of common grade, the eutectic graphite structure was always produced in it, if it did not solidify very slowly.

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Sampling on the quantitative spectrographic analysis of the silicon, manganese, nickel, chromium and copper contained in iron and steel was improved so as to apply it to the daily work.
By this investigation the authors could obtain practically satisfactory results in view of speed and accuracy of the test.
The results obtained were as follows
1) The authors designed two methods for sampling of molten steel. One was to cast in to a metal mold directly from the nozzle of ladle, and another was to pour into a metal-mold indirectly from the spoon.
2) The former metal-mold was used for the molten pig iron, and the core drill (7mm diameter) was designed for the grey pig iron.
3) The best condition for the discharge was to use the nipple-point type. (1.5mm diameter, 60-80° angle)
4) Local analysis was made easy by applying wax and punch to symmetric surfaces. Metallic zinc was applied to the symmetric electrode.
5) According to the application of the above-described sampling method, the time required for the analysis was shortened, and at the same time reproducibility was improved to 2-5%.

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In industry of Japan, the sub-zero treatment are widely discussed recently and applied to the manufacture of the ball and roller bearings, tools, gears, etc. The theory and the application of the sub-zero treatment of the steel are briefly outlined as follows.
(1) The retained austenite of the quenched steel can be decomposed by the sub-zero chilling and the hardness of the steel becomes higher and uniform.
(2) The retained austenite decomposes isothermally at room temperature and the length of the steel changes. To prevent the secular change of the length, the gauge or the ball bearing is cooled to the freezing temperature and tempered sufficiently. Thus treated, the change of the length becomes smaller than 10^-6 of the initial dimension after one year.
(3) The mechanical properties of the steel are improved by the sub-zero treatment of the proper cooling temperature. The impact value of the bearing steel or the life of the tool increases by this treatment.
(4) Stabilization and the transformation of the retained austenite are discussed. The stability increases when the α martensite is decomposed, while it decreases when the precipitation occurs.
(5) Sub-zero treatment is applied to the magnetic steel and the case-hardening steel.

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