The authors investigaed on the reduction process of several sorts of iron Ores by the reformed natural gas. the results obtain were as follows: In general, the reducing action of natural gas, was weak, but it was found that when it was decomposed, the reduction became strong. This strong reducing action would be given by hydrogen formed by the decomposition of hydrocarbon in the gas. The action of carbon monoxide in natural gas appeared similarly in the case of pure CO. At lower temperature, reduction of bog iron ore and hematite was proceeded more rapidly than that of magnetite, while at higher temperature, the magnetite was most rapidly reduced than others. The degree of reduction at the constant temperature (=700°C) was greater, when the flow rate of gas was more increased.Further investigation for reduction of iron ores by the reformed natural gas would be required not only for chemical compgsition but also for mineral construction of the ore.
It has been early known that boron was reduced and alloyed with steel, when steel was melted under a covering borate-containing slag, and the steel was hardened. One of the authors has reported this facts. (cf. M. Hasegawa, "Effect of Special Elements on Iron & Steel, " 1950, Tokyo; M. Hasegawa, Tetsu-to-Hagane, Vol. 38, 1952, No. 7) Lately Speight also reported on the addition of boron to steel by the reduction of boron oxide, in detail. Prior to this, as the authors have studied this problem, in this issue they report the preliminary experiments in laboratory and chiefly the results of industrial tests using 2-ton Heroult furnace. The results of industrial application are as follows; (1) The experiments were performed in 2-ton basic electric furnace and 15 specimens of low-chromium and low-manganese cast steel were made. (2) 0-3kg of boric acid anhydrous (B2O3) was added in the final slag before tapPing, and it was reduced with less than 0.2% of aluminium and 0.15% of titanium. Then, after the killing for 5-15 min., the molten steel was tapped into ladle. (3) In every case, the suitable amounts of boron could be alloyed in steel. The yield of boron changed with the melting conditions, of course, but in the stationary condition, 30-50% of boron was reduced approximately, in this experiments. (4) The optimum amounts of B2O3 addition to promote the hardenability of steel were 0.05-0.02% in weight to steel. (5) There was no difference between the steel made by this method and boron steel using boron-contaning ferro-alloys, in quality. (6) The authors concluded that this method was not difficult, not expensive and suitable for making boron steel in practice.
In order to investigate the cause of the defects of the rimmed steel tubes during the piercing process by the Mannesmann type roll, hot w6rking properties of rimmed steels were studied. When the cross section.of the billets was macro-etched with the ammonium copper chloride solution, many dark grey spots and black spots were detected in the core of billets. The results of the rotary hammering tests, impact bending tests and piercing tests showed that the dark grey spots were not so injurious, while the black spots acted as defect point for the hot working.
The effects of alloying elements on Charpy U notch impact properties were investigated in the range from room temperature to 900°C. Arsenic, copper, tin and molybdenum were added singly or simultaneously to a base composition of 0.04% carbon, 0.2% silicon and 0.4% manganese. Ferrite and austenite grain sizes, hardness and microscopic structures of the specimens were also examined. The results obtained are as follows: 1) Copper less than 0.35% or tin less than 0.1% has no effect on impact property of dcad soft steel when either of these is added to the steel. 2) When copper and tin are added together to a steel, the temperatures in which the impact value becomes maxiinum and minimum respectively move to higher temperature range. 3) When arsenic, copper and tin are added together to a steel, transition temperature of the steel is increased as the content of arsenic increases. Whcn a steel contains less than O.25% arsenic, 0.35% copper and O.1% tin, any serious effect is not observed on impact properties at room temperature and these values may be the maximum limit of the allowable content. 4) Molybdenum has the tendency to lower impact value at room temperature, inhibits the decrease of minimum impact value in blue shortness range and also inhibits the temperature of maximum impact value to move to higher temperature range. 5) Ferrite and austenite grains are fine and neary similar in all specimens, but ferrite grains of the specimens which showed brittle fractures at room temperature are somewhat larger than the others. 6) Hardness of annealed specimens increases as the content of arsenic, copper, tin and molybdenum increases. 7) From the results obtained above, the maximum allowable content of arsenic, copper and tin are estimated for the deformability of dead soft steel. The form of ingots, heating temperature and its time etc. must also be considered for the determination of the allowable limit.
The deterioration of mineral oils for quenching was studied under the same procedure as described in the 1st report (The Deterioration of Fatty Oils: Tetsu-to-Hagane No. 2, Feb. 1954 p. 103-111). The properties of mineral oils vary with the blowing with air as follows: (1) The quenching ability of mineral oils increases at the beginning and then decreases slowly with the blowing time, and the time required to cool from 700° to 350°C is given approximately as a function of the blowing time by the following formula: then, The changes of cooling ability with the blowing time abovementioned are attributed to the rise of the characteristic temperature in cooling process, at which vapour film breaks down, due to the formation of polar substances with the blowing time and the rise of the beginning temperature of the convection stage due to the increase of the amount of polymerized product. the τmin offers a criterion for the life of oil and the ρmax gives a degree of variation of cooling ability during the deterioration of oil. (2) The viscosity increases with the blowing time: The amount of sludge increases with the blowing time: The specific gravity increases with the blowing time: The flash point decreases with the blowing time: The acid value increases with the blowing time: The iodine value decreases and the saponification value increases with the blowing time. (3) When oil is highly refined, the t0, the τmin and the αF are larger and the ρmax, αη, αS, αG and αA are smaller respectvely, that is, highly refined oil is more stable. (4) Lighter oil is more stable than heavier oil, but this difference of stability becomes smaller according to better refining. (5) Highly refined naphthenic oil is stable as paraffinic oil. (6) Among a series of mineral oils produced from identical crude oil, the larger the iodine value and the more the residual carbon, the deterioration of oil is the more rapid. (7) It is observed that the τmin becomes larger for higher temperature of oil in the measurement of cooling curves at various temperatures below 100°C with a same oil. (8) The t0, the τmin and the αS of mineral oil are larger and the αη and αG are smaller than those of fatty oil. Then, the deterioration of mineral oil is much slower than that of fatty oil. (9) The deterioration of mineral oil containing fatty oil is more rapid than that of straight mineral oil. (10) Quenching oil must be evaluated synthetically with values of the t0, τmin, ρmax, αη, αS, etc. Note: t: Time required to cool from 700° to 350°C for oil blown with air, sec. t0: Time required to cool from 700°C to 350°C for fresh oil, sec. tmin: Minimun value of t, sec. ρmax: Curvature at the point of t=tmin on the curve. η: Viscosity of oil blown with air, Redwood, sec. η0: Viscosity of fresh oil. S: Amount of sludge of oil blown with air, mg/10g. S0: Amount of sludge of fresh oil. G: Specific gravity of oil blown with air. G0: Specific gravity of fresh oil. F: Flash point of oil blown with air, °C. F0: Flash point of fresh oil. A: Acid value of oil blown with air. A0: Acid value of fresh oil. τ: Blowing time, hr. τmin: Blowing time for the minimum value of t, hr. c, b, αη, αS, αG, αF and αA: the constants.
The authors studied on the various properties of 13% Cr Cast steel (fluidity, machinability, corrosion-resistance, weldability, machanical properties, etc). The results obtained are as follows: 1) It was recommended to employ the materials consisted of such compositions as shown on the following table, in accordance with their proper uses. 2) The machinability was the best in annealed state. When heat-treatment was made, the cooling velocity changed in the order of oil and water. 3) The most favourable mechanical properties were obtained by quenching at 100°C and tempering at 700-780°C. 4) The annealing-brittleness possibly resulted from carbide precipitation on net work. It was improved by normalizing the materials. 5) In case welding was made with this steel, the best result would be obtained by the application of inverse-palarity using the electrode of 13% Cr or 10Ni-20Cr steel system.
The author feviewed the present situation of the creep testing and the knowledge about. creep characteristics of steels. At first, the author stated that among the so-called the first, the second, and the third stages of creep, the second one or the steady state creep would show an inflection period from the transient creep to the accerelating period. Several long term creep test results showed this idea to be true. In the past days, short time creep testing had been mostly carried out in Japan, there were, however, many reasons to prefer the long term test, and the Japan Society for the Mechanical Engineers and'the Japan Society of Testing Materials are now going to specify the procedures for conducting the long period, high sensitivity creep test and creep rupture test. Several precautions in regard to testing machines, loading apparatus, selection of the extensometer and the temperature control equipment were resumed. Applications of the creep data for thelengineering design had been introduced by several authors, among the so-called mechanicalequation of state advocated by Hollomon and.Lubahn, the master rupture curve of Larson and Miller and their reltd literatuewer.9 introduced in some details. In conclusion, the author cited important problems to be solved theoretically or experimentally in relation to the creep of steels.