The Wanishi-machi No. 3 Blast Furnace (Nominal capaeity 225t/day, hearth diameter 4.3m, inner volume 356m³) is the smallest of the kind now operating in Japan. But the blower used for this furnace has a large capacity enough for 500t/day operation. Therefore several counter- measures to the furnace operation were taken according to the change of conditions during the period since its blow-in of June 1948, and we have got various interesting results.
1. Common Blast Operation.
During the long period of a year and four months from June 1, 1948 to September 12, 1949, common blast operation with the same blower was smoothly kept on together with Wanishi-machi No. 4 Blast Furnace (Nominal capacity 225t/day then also in operation.
2. Operation with the Use of Low Grade Coke.
Since shut-down of No. 4 Blast Furnace in September 1949, the single operating furnace has been obliged to use the coke made only from Hokkaido coal and without blending of coalite. The drum index of that coke was as low as about 55%. Besides, for the purpose of raising the yield of lump coke, nut size coke was used to mix some 20%.
In order to maintain the best output of pig iron under such unfavourable conditions, the following counter-measures were successively applied all of which proved good results.
a) A heavy charge operation by increasing the ore/coke ratio up to 1.85, and the coke ratio could be lowered to 0.85. (Period of Practice: Sept. 1949Feb. 1950)
b) Rise of the blast pressure from 700-800g/cm² to 900g/cm², so that the operation might be kept on in good condition. (Period of practice: March 1950-July 1950)
c) Enlargement of the diameter of tuyeres from 110mm to 130mm, so that the blast volume might be increased to bring more output of pig iron. (Period of practice: August 1950-up to date)

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Evolution of gases from rimming-steel ingots during solidification was studied, with the results as folloWs.
(1) Most of gas evolution curves have maximum value, for volume of evolved gases increases at the beginning of solidification and then decreases. The volume of gases and position of maximum value are to be affected by the C, Mn and O₂ content of metals.
(2) The main composition of gases are CO (91-85%), CO₂ (4-1%) H₃ (4-11%) and N₂ (0.5-4%) and during solidification CO and CO₂ decrease, but H₂ and N₂ increase gradually.
(3) CO and CO₂ in gases and C or O₂ in molten metal are approximately in equilibrium.
(4) Gas pressure of molten metal is about 1.5atm., and this value is coincident with the presumed value from the ingot structure.
Besides, the relation between the gas evolution and ingot structure as well as a probable mechanism of blowhole formation were studied.

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A number of papers such as by H. Schenck, F. Korber, and W. Oelsen have much explaihed the function of the slag in steelmaking and provisionally perfected the working instruction of the prest steelmaking. There are, however, many problems left to be solved in its essential details. Some reaulta obtaingd by the author'a egperiment concerned are as followa:
(1) A slag tends to be strongly ionic as the temperature rises, and. the specific electric conductivity κ is in molten state in the order of 1/10-1 Ω^-1 cm^-1 being dissociated into several cations and complex anions. Particularly such silicate or phosphate ions in a molten slag do not always exist in one special form only, but the nighbouring anions of nearly equal construction are considered in a combined mixture statistically or in the form of some of these specified orientations.
Many experimental facts obtained here establish molten slag to be ionic, but they do not give the degrees of dissociation Therefore it is perhaps unfair to insist as some researchers persist that neutral molecules should not remain.
(2) The technique was proposed deciding through the combination of more practical ionic molar energiea of formation (ε) concering the elementary oxides, number of metallic atoms included in the components (m), number of O atoms as the nearest neighbours around them (c: co-ordination numbers) and mole fractione of the elements (n); this quantity was considered to be possibly the precise formula of the slag basicity from the point of view owing to the G.N. Lewis definition of acids and bases, so that it would presumably replace the ambiguous basicity such as customary (CaO)/(SiO₂) ratio etc., judging from the eaperimental results here obtained and also specification of practical data.
(3) It was decidad that B or Br above mentioned were tightly connected with the Martens hardness of a quenched molten slag except the basic ones, which were regarded as strongly microhetercgeneous. Besides we discussed two kinds of irreversible phenomena like the electric conductance of a molten slag observed and the viscosity associated with it, as compared with the excellent studies by O. Esin, Kheinman and others (U. S. S. R.) who claimed about the ionic constructions of a molten slag. Specially we supported the Grotthuss type mechanism by meane of O-- concerning the conductance, and emphasized the important. role of O-- played in the estensive fields.
(4) Also the attempts introducing the FeO activity from the statistical treatment in the ternary system GaO-SiO₂-FeO referred to. O. Esin & V. Kozheurov were interpreted, and so they seemed to be pretty well suitable for the esperimental facts with more or less defects. We hope that (n) inB or Br should be correctly understood through such considerations and other experimental measurements.
In these intermediate stages of studies, we can only anticipate the peculiarities of interface reactions between slag and metal in high tempeture, but it is hard to attain the quantitative analysis of reaction mechanism or "Slag Control", and "Reaction Control" instantly.

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In case of annealing low carbon steel, sometimes an "anneal-brittleness", (named by the author) occurs accompanied by its softening and a remarkable decrease in impact value. This report treats of the results of inspection on the cause of developing "anneal-brittleness" and its prevention. Some of chief conclusions are as follows:
1. Anneal-brittleness occurs remarkably in low carbon rimmed steel, while it seldom occurs in killed steel.
2. Anneal-brittleness occurs, because ferrite grains become coarse and cementite separates out around the boundaries of ferrite grains when low carbon steel is cooled slowly from high temperature.
3. Anneal brittleness increases remarkably with decrease of the C content and with increase of the N, O or P content.,
4. From the viewpoint of quality, killed steel should be used instead of rimmed steel if anneal brittleness is undesirable. In case of rimmed steel anneal-brittleness can be avoided by such normalizing in which aircooling rate is high.

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In sequence from the previons reports (TentsutoHagane, May 1951, p. 272283), the eaperiment was made and summarized as follows:
(5) Addition of zirconium refines the austenitic grain size of steel and retards the grain growth at high temperatures.
(6) 0.50.9% of zirconium into steel has no remarkable effect on A1 point, but slightly lowers A3 point both in heating and cooling conditions. But in most cases these effects are covered by the action of the silicon.
(7) In many cases zirconium refines the annealed and normalized structures of steel, but there is no remarkable effect in quenched and tempered structures.
(8) Addition of zirconium more than 1% on carbon steel and lowalloyed steel can not expect the improvement of their mechanical properties, but addition of it up to 0.5% improves the mechanical properties of steels in normalized and high temperature tempering conditions.
(9) Zirconium raises the toughness of steel at low temperature tempering and shows the temperresistance at high temperature tempering.
(10) Zirconium prevents the temper brittleness of lowalloyed etructural steels.
(11) The deoxidation with zirconium improves the low temperature brittleness of steel With the indirect effect by improvement of structure, as in the previous report.

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The foundamental problems of steels for high pressure vessel used in ammonia synthesis can be devided as follws:
1) Mechanical strength at high pressure and temprature
2) Chemical attack by high pressure and temperature gases In high pressure vessels and covers, 1) is the most important, while in internal parts, catalyst tubes, heatexchange tubes etc., 2) is the most important roblem.
As one way of studying about the chemical vessels, we tested the changes of the high pressure vessels, made at the Muroran plant of Japan Steel Werks, Ltd., and used for about twenty years. The authors took specimens from these materials and tested the changes of their chemical composition, micro structure, mechanical properties and gas adsorption.
As results of the tests, it was found that the high pressure vessels, made from NiCr steel and used for about twenty years, could stand the use of longer period. Nevertheless, the upper cover used for the same period and under the same condition was attacked by gases under high pressure and at high temperatures.

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The author studied on the change of mechanical properties on the diffusion of dendritic segregation by means of high temperature normalizing treatment; and also studied on the repeated normalizing test that were applied to the various specimens, including Cr-Mo cast steels (1% Cr, 0.25-0.35% Mo) added with Si, Ni and Mn.
Whether simple or repeated normalizing was applied, the mechanical properties, eapecially impact resistance, increased as the dendritic segregation were diffused.

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Since the end of the war, welding electrodes have become one of the most important special materials in Japan. However, the technical level of quality of welding electrodes in Japan seems to be much lower than that of in U.S.A. and England. Therefore, for general reference, the auther collected here the various recent data of welding lectrodes, such as the history of formation of Japanese standard specifications for arcwelding electrodes and its wires, American specifications of electrodes for mild steel, low alloy steel, and corrion-resisting chromium and chromiumnickel steel, British specifications for mild steel electrodes and chemical compositions of some foreigh electrodewires of superior quality in order to introduce and explain them especially from a viewpoint of metallurgists.

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