Making research on the reflecting microscopic structures on the cross section of slag pancake sampled at several stages of basic O-H steel refining, the authors have made an inspection on the relation between the structure and the mineralogical components of slag. As the results, structure could be classified into four groups (I. olivin, II. merwinite, III. dicalcium-silicate, tricalcium-silicate) according to its basicity. And it was found that in each group, structure differed according to the differences in basicity and other components. Therefore, it was confirmed that if a standard sample was prepared in advance, the components of non-determined sample could be presumed by comparing with it. Basicity could be estimated within an error of 0.1 or 0.2 respectively at under or above 2.5 Vp (=CaO/SiO₂+P₂O₅) and estimation of FeO, MnO and P₂O₅ was also possible to some extent. The time required in determination being within 10 minutes and an intricate apparatus or skill being not required. Thus so this method could be applied to an operation plant with confidence and the improvement of accuracy in estimation could be expected by applying it together with pancake test.

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The author had already reported the results on the test heats by oxygen blowing at 5t and 10t arc furnace, in which some problems on the factors in steel smelting were studied. (cf. Lectura Meeting, Iron & Steel Inst. Japan, Oct. 1951; Denki-Seiko, Sept. 1951, May & July 1952.) In the mean time all heats had been changed to oxygen process at Dec. 1951. Therefore, by summing up the data on the practical operation and results on the test heats, this paper studied decarburization, dephosphorization and gas removal, and also some problems on the particularities of oxygen blowiog process. The results obtained were as following:
(1) In regard to decarburization, comparing with 5t and 10t furnace with respect to decarburizing velocity, oxygen efficiency and the relations between[C]% at melt down and decarburizing velocity, it was considered that the predominant factor among the factors that influenced upon decarburization velocity, were varied by[C]% and each blowing period to the blowing condition.
(2) In regard to dephosphorization, if only operational condition was suitable for dephosphorization, effect of oxygen blowing process was superior to that of are process and dephosphorization reaction proceed continuously from biginning to end of the blowing period and moreover, even under the condition that was suitable for dephosphorization, increase of[O₂] not larger than that of the ordinary condition. It was considered that among the factors that influenced upon dephosphorization at the oxygen blowing process, temperature was a subdominant factor while slag condition and supplying velocity of oxygen was predominant factor.
(3) In regard to hydrogen gas removal, oxygen process was superior to better and stabler than ore process.
(4) In regard to inprovement of quality of the produced steel, oxygen process was superior to ora process in respect of the decrease of non metallic inclusions and stabilization of grain size, which were remarkable on the low carbon steel and Cr-steel produced from high chromium scrap.

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Since introduction of the statistical quality control into the Tsurumi Iron works, Nippon steel Tube Co. one and a half year had elapsed. In this report the authors make a brief survey of the past experience, especially with reference to the stage of introduction period.
Although many control charts had been actually used, most of them were what they call "analysing." Such was very natural in view of the present condition of our open hearth furnace engineering. Nevertheless, some good results were obtained such as the improvement of techniques and the saving of production cost.
In order to make the use of control charts more effective, it wae imperative that there should be established more complete operation standard as quickly as possible. The major effort should thus be directed to the attainment of such aim.

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The authors have studied on the characteristics and differences of acid and basic open-hearth furnace steels in origination of sand cracks during the ingot makimg process. (cf Rep. 1, Tetsu-to-Hagane, 38, 1952, No. 5.) The subjects of study were as follows:
(1) Deoxidizing products during the ingot making process.
(2) Corrosion of various refractories by molten steel.
(3) Oxidation of molten steel by atmosphere during the ingot making process.
The results obtained were as follows:
(1) It was evident from the analytical results of non-metallic inclusion (sand) in steel in furnace before tapping, in the ladle and in the runner, or from analysis of scum in the mould, that basic molten steel produced much more deoxidizing products than acid molten steel in the ingot making process.
(2) According to observation of the runner surface on which the molten steel bad passed through, its analytical results, relation between[Mn] and[Si] contents in these molten steel before tapping and in the ladle and those oxidizing products, it was found that corrosion of various refractories by basic molten steel was more ε ctive than acid molten steel.
(3) From the changes of[C], [Si], [Mn], [Al], [Cr], [FeO], etc., in these molten steels before tapping and after the finish of casting, it was inferred that oxidation of basic molten steel by atmosphere during the ingot making process was heavier than the acid.

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In the previous reports, (Tetsu-to-Hagane' vol. 38, (1952), 470-478 & 683-686) the authors made clear the effect of carbon and chromium on the high carbon high chromium die steels. In the present investigation, the authors studied the effect of tungsten on the high carbon high chromium die steels by the same method as previous investigation.
As the results of these investigations, the effect of tungsten on the high carbon high chromium die steels was ascertained and then a die steel containing 1.25-2.00%W was found better as the punching and drawing dies than non-tungsten die steel.

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(1) The rods employed as sample were those of clothing card wire, piano wire and rope wire produced in Japan, Switzland, U.S.A, and Sweden. When they were treated by the warm H₂SO₄ method without bringing them into contact with the air, the quantities of the black residues were found larger than they were treated in the air, the degrees of increase being found to be nearly equal for all of them.
(2) When the absolute quantity was increased, though the ratio of quantities between the sample and H₂SO₄ was kept equal, the proportion of the black residue to the sample was found to increase.
(3) In many cases, the quantity of black residue showed a tendency to increase in proportion to the quantity of Cu contained, but in a few cases the contraries were observed.
(4) In analysing the black residues (1) which were obtained by treating the samples by warm H₂SO₄ method without being brought into contact with air and dried by heating in vacuum, some different results from that when the production and drying of the black residue (2) were carried out in air, were obtained. The degrees of remaining in residues for respective elements of rods were as follows. In cases (1): for Japanese products, C 12.9-26.6%, Si 29.7-65.7%, Mn 1.6-3.%, S 45.8-90.4%, P 33.3-65.6%, Ni 28.8-41.4%, Fe 0.82-2.28%, Cr 0%, Cu 100%; for the foreign products, C 6.7-7.9%, Si 32.2-42.6%, Mn 0.6-1.0%, S 47.6-61.5%, P 34.6-44.0%, Ni 10-20%, Fe 0.31-0.46%, Cr 0%, Cu 100%.
In both Japanese and foreign products, the values of Cr and Cu were identical for both (1) and (2) and all the other elements except P were remained in residue to larger extent in cases (1) than in cases (2). (cf. Akisue Kiuchi, Preprint for Oct. 1951 Lecture Meeting, Iron & steal Inst Japan.)

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As it was found that the disappearing states of the eutectic cementites of the white cast iron were changed due to the heating conditions when annealing, the effects of heating rate on them were studied thoroughly and it was confirmed that there exist two tendencies of cementite by heating rate.
If heating rate was not very high, the disappearance of eutectic cementite decreased with increase of the heating rate refering to the heating time between the Ac_1.3 transformation range, depending chiefly on the diffusion phenomenon.
But if the heating rate exceeded some certain limit, the disappearance of cementite increased again with the increasing rate of heating, and in this case which seemed to be affected by the super heated degrees of the transformation temperatures and the stress accompanying the transformation.

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It has been a general belief that the chill-cast rolls produced through the process of electric furnaces were apt to break off easily; because the graphite nuclei were dissolved by too intense heat; the iron losed its own property; and the manganese contained therein increased its quantity.
To correct these defects and eliminate the enlargement of graphite nuclei, it is necessary to keep the temperature of the furuace between 1450°-1550°C.
The reaction inside the furnace is divided into the following two periods: oxidation period, in which the authors aim at the proper adjustment of the charging and at the oxidation refining, and reduction period, in which the authors make complete deoxidation and desulphurization of the molten pig iron and the control of Fe-Si, the depth of the chill and then tapping.
The authors consider theoretically on the elimination of each element by oxidation, reduction period and recarburization, and the standard of the operation of the 3 tons Heroult electric furnace.

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Notable difference often was found between Gakushin-method (a methed recommended by Japan Society for Scientific Promotion, and followed by the Laboratory of Kamaishi Iron works) and colorimetric method (followed by open-heath furnace shops of the same works) when analysing manganese in sheet-bars and other steel. Therefore first the authors examined the following points which might cause erroneous results in Gakushin-method (ammonium persulphate-sodium arsenite).
1. Effect of heating temperature and time after added ammonium persulphate.-Though the Gakushin-method specified the heating time to be one minute, when manganese was contained in execss of 0.75%, the manganese was apt to begin to decompose starting from 30 seconds after heating and this decomposition rate increased with the rise of heating temperature.
2. Cooling temperature and time-The best results were obtained at cooling temperature of 20°C and the authors kept running water for three minutes in order to maintain the cooling temperature at 20°C
3. Concentration and quantity of sodium chloride solution repuired-The present experiment indicated that the best result conld be obtained at 1% in concentration and 10cc-15cc in quantity and end point was clear.
4. Selection of standard steel sample according to mangnese contents-the present experiment indicated that the best result conld be obtained when titrated with arsenite solution which standardized by the standard steel sample containing manganese nearest to that of the sample taken.

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It is not necessary to explain here that the components of slag play an important role in pig iron and steel making practice. It is certain that progress and improvement of operation can be achieved by analysing slag chemically and investigating them after each operation.
But in case the components of slag change every moment simultaneously with that of molten metal as in steel making practice, it would be required. to estimate the slag components quickly and to take proper means at once for the results. For this purpose, estimation within a short time is especially requested even at the sacrifice of its accuracy. As for the rapid estimation of slag, several kinds of method have been proposed and applied in practice.
The outline of all these methods was reviewed here which were intended to be used as a standard for so called "slag control" in operating plant, covering the following items:
1) Foreword
2) Rapid chemical analysis
3) Slag pancake test
4) Estimation by microscopic structure.
5) Estimation by colors.
6) Estimation by viscosity
7) Estimation by pH or specific electrical conductance of aqueous extracts of slag.
8) Spectrographic analysis
9) Estimation by specific gravity
10) Conclusion.

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[in Japanese]

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[in Japanese]

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