Tetsu-to-Hagané
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ONLINE ISSN: 1883-2954
PRINT ISSN: 0021-1575

Tetsu-to-Hagané Vol. 59 (1973), No. 1

  • 新年を迎えて

    pp. 1-2

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  • 1972 Perspective of Production and Technique of Iron and Steel in Japan

    pp. 3-16

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  • On the Reduction and Firing of Pellets Containing Charcoal and Coke

    pp. 17-27

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    The purpose of this paper is to clarify the influence of self produced gas on the reduction of pellets containing solid carbon materials. The changes of the state in the firing of the pellets were investigated by chemical analysis. gas chromatography, microscopic observation, and X-ray microprobe analyzer.
    The following, results were obtained.
    1) When the self produced gas reacted effectively in the firing of pellets, the green pellet containing 20% carbon materials was reduced to highly metallized state.
    2) The content of solid carbon materials and the gas volume of atmosphere in the beginning of the firing had be chosen to appropriate value.
    3) Maximum CO gas concentrations of 72, 73, and 98% were obtained by the pellets containing coke of 10.0, 12.3, and 20.0% respectively.
    4) In the case of the pellet containing charcoal, it was almost the same as in the case of coke's pellet described above, but concentration of CO gas was markedly increased in the temperature range from 700 to 1 000°C. It is noted that charcoal's pellets indicated good reduction degree in the range of low temperature, compared with coke's pellets.
    5) As the charcoal contents of pellet were increased, however, the compression strength become lower and the significant behavior of reduction at low temperature did not appear clearly.
  • The Effect of Iron Oxide in Slags on the Interfacial Tension between Molten Iron Saturated with Carbon and Molten Blast Furnace Type Slag

    pp. 28-32

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    The measurement of the interfacial tension between a molten lime -alumina -silica slag and a molten iron saturated with carbon was done in order to know the characteristics of the reaction, (SiO2) +2Fe=Si+2 (FeO), at the slag-metal interface. The results showed as follows;
    (1) The concentration of iron oxide in slags changed the interfacial tension between the slag and the metal, and it suggests that the interface potential for the slag-iron (saturated with carbon) system was mainly determined by the concentration of iron oxide in slags.
    (2) Electrical double layer at slag-metal interface may be formed by negative excess charge at the metal surface and possitive excess charge at the slag side. And the excess possitive charge may be induced by the existance of Fe2+ cations adsorbed at the metal surface.
  • An Investigation of Sulphur Transfer via Gas Phase in a Blast Furnace

    pp. 33-45

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    As one of a series of investigations designed to establish the mechanisms of mass transfer via gas phase at the melting zone in the blast furnace, thermodynamic and kinetic investigations of S transfer from or into molten iron via gas phase has been carried out.
    It is clarified from the thermodynamic considerations that the molten iron is desulphurized not only by slag-metal reaction in the hearth, but also by gas-metal reaction when the molten iron is descending through the melting zone. S in metal is removed from the molten iron to gas phase as S2 or CS2 etc, and to slag phase as sulphides by gaseous alkali or alkaline earth metals produced at high temperature zone.
    From the experimental results on the desulphurization kinetics of the molten iron by Mg gas, it is observed that the rate of desulphurization is considerably rapid.
  • Pressure Drop in Countercurrent Moving Bed with Radial Distribution of Particle Size

    pp. 46-54

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    Characteristics of pressure drop, gas velocity distribution and solids movement in countercurrent moving bed with radial distribution were studied.
    Following results were obtained:
    1. Radial mixing of particles in bed was not observed up to the channeling state. The effect of descend ing motion of particles on the pressure drop was not observed clearly. However, the pressure drop was found to be remarkably affected by the variation of radial distribution of void fraction.
    2. Except for the upper layer, the pressure drop per unit bed height was found to be constant along the height of bed.
    3. The pressure drop was found to vary considerably depending on the size combination of charged in center and periphery. It seemed that radial distribution of gas velocity was built up so as to realize uni form radial distribution of pressure and minimum pressure drop.
    4. The gas velocity distribution was observed to correspond to radial distribution of particle size and to become more uniform with increasing rate of gas flow.
  • On the Determination of Interfacial Tension between Liquid Iron Alloy and CaO-Al2O3 Slag

    pp. 55-62

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    An improved method for measurement of interfacial tension between liquid iron alloy and liquid slag has been developed. The method is based on simultaneous determination both surface tension of liquid iron alloy σmg, which is measured by use of large drop method, and contact angle of liquid slag droplet on the liquid iron alloy. The interfacial tension ‘σms°’ between CaO-Al2O3 slag and liquid iron alloy was determined at 1 570°C by the method within 0.5 second after contacting the two liquids. Results obtained are as follows:(1) Oxygen dissolved in liquid iron brings about drastic decrement of a σms°, while both carbon and chromium in liquid iron lowers slightly σms°.(2) Both decrement of am; and that of crag by addition of one of the elements mentioned above into liquid iron are nearly equal to one another, and also both decrement of σms° and that of surface tension of CaO-Al2O3-SiO2 slag asg by addition of SiO2 component into the slag are nearly equal to one another.(3) Main cause of the interfacial tension character will be induced by independent contributions both of σmg and σsg respectively, while interaction between the slag and the iron alloy may play a minor role in the interfacial tension character.(4) Work of adhesion Wa between the slag and the iron alloy within 0.5 second after contacting the two liquids keeps constant value even when only one of the two liquids makes change in composition.
  • Interfacial Impedance between Solid Platinum and Liquid Oxide Solutions

    pp. 63-71

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    Dispersion of AC-impedance at the interface of solid platinum/oxide or halide melts has been determined at 800 to 1 300°C under pure oxygen, air or argon atmosphere. The liquid solutions studied are; a) 60, 50, and 40 mol % PbO-GeO2, b) 60, and 40 mol % PbO-SiO2, c) pure CaCl2, d) 50 mol % CaF2-MgF2, and e) 47mol% CaF2-MgF2. The interface impedance, measured by both parallel and series connections of a variable capacitance and a variable resistance in the bridge, has been found to increase with decreases of the frequency, temperature, and oxygen pressure in the atmosphere, and with the increase of silica or germanate content.
    Under the assumption that the double layer capacity is independent of the frequency, a calculation for the ohmic and capacitive components of the measured interface impedance has been made. By so doing, these two-components have been plotted against reciprocal square root of the frequency. Except for the frequencies higher than 5 kilocycles, a good linear relation has been obtained in the diagrams. Thus, it seems that the interface impedance is predominantly composed of a diffusion impedance. The most likely species for the diffusion is deduced to be di-atomic oxygen dissolved in liquid oxide solutions, because the impedance has depended on both oxide composition and oxygen pressure in the gas phase.
    The probable double layer capacity is in the range of 700 to 1 100 μF square centimeter but its relation to temperature and the oxide composition has not been clarified due to large experimental errors.
  • The Air Reoxidation and the Formation of Large Inclusions in Continuous Casting Process

    pp. 72-84

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    A study was made of non-metallic inclusions in medium or high carbon steel billets which were cast by the six strands S-type continuous casting machine of Kokura Works, Sumitomo Metal Ind., Ltd. The way of avoiding large silicate inclusions was also investigated.
    As the result, the reoxidation by air during casting was found to be detrimental in producing high quality steel grades by continuous casting. Many kinds of large silicates even if they are chemically unstable can exist in large quantity when the tundish stream was not protected from air.
    In order to avoid those silicates, it was shown that the oxygen content of the atmosphere around the stream must be maintained under 0.8%. The mechanism of the silicate formation and its growth are discussed on the basis of the test results.
  • Effect of Alloying Elements on Toughness of Rapidly Heated and Quenched Steels

    pp. 85-93

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    As reported previously by the authors, the hardness and toughness of steels which were heated rapidly to the optimum austenitizing temperature and quenched after holding at that temperature for a short time (“rapid heating”) were higher than those of steels which were slowly heated and quenched after holding for a longer time (“slow heating”).
    In this report, to clarify the effect of alloying elements on the toughness of steels treated by “rapid heating, ” static bending test and metallographic examination in electron microscope were carried out by using low alloy steels containing C, Ni, Cr, Mo, and Si which had been treated by “rapid heating” or “slow heat ing”.
    The results are summarized as follows:
    1) The statical bending characteristics of the steels without Ni, Cr, and Mo treated by“slow heating” were deteriorated with increasing carbon contents in martensite matrix.
    2) The statical bending characteristics of the high-carbon-nickel steels were improved by “rapid heating”, because the dissolved carbon in martensite matrix were decreased by this treatment.
    3) Ni had a very small effect on the toughness of high carbon steels treated by “slow heating” but had a large effect on that treated by “rapid heating”.
    4) From the above results, it was found that the carbon contents effective for the mechanical properties of steels containing Ni was below about 0.6% in martensite matrix.
    5) It was clarified that high hardness and good toughness could be obtained by the combination of “rapid heating” and high carbon steel containing Ni, Cr, and Mo.
  • The Influence of Cold Working on the Delayed Fracture Strength of Steel

    pp. 94-99

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    To evaluate the influence of internal strain, separating it from the influence of microstructure, upon the change of delayed fracture strength of steel due to tempering after quench-hardening, the change of delayed fracture strength with cold-drawing and annealing after drawing was investigated for 0.38%C-0.95%Cr-0.18%Mo steel whose microstructure had been made to contain stable spheroidized carbides by annealing. The delayed fracture test was carried out in 0.1N-HCl solution by a cantilever type bending machine. The results are summarized as follows:
    (1) The hardness and static bending strength of the steel increased and delayed fracture ratio (the ratio of delayed fracture limit to static bending strength) decreased gradually with increasing cold reduction in drawing.
    (2) The delayed fracture limit reached a maximum value with the cold reduction of 16%. It is thought that the result is attributed to the cause that at that cold reduction the load carrying capacity of the steel balanced with the susceptibility to delayed fracture, both of which increased with increasing cold reduction of steel.
    (3) The delayed fracture strength of the steel in short life region increased by cold working. It is thought that the result comes from the decrease of diffusion rate of hydrogen due to the trapping effect of lattice defects produced by cold working.
    (4) The delayed fracture limit and delayed fracture ratio of cold-drawn steel increased with increasing annealing temperature gradually up to 300°C and rapidly over 300°C.
    (5) The delayed fracture ratio varied in good correlation with the change of internal strain induced by cold working or annealing after that. It was suggested that microscopic internal strains play an important role in susceptibility to delayed fracture of steel.
  • Effects of Heat-treated Structures and Cold Working on the Machinability of Case-hardening Low Chromium Steels Containing Different Sulfur Contents

    pp. 100-111

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    Effects of heat-treated structures and cold working on machinability and tool life with high speed steel tools in drilling case hardening Cr steels containing sulfur up to 0.1% have been investigated.
    Lameller pearlite structures obtained by annealing or normalizing show the best drillability. As dispersion of cementite particles becomes uniform and spheridizing of carbide progresses drillability becomes worse remarkably. But machinability based on tool life is the best for spheroidized structures.
    Drillability seems not to be improved by cold working. The effect of cold working on tool life with high speed steel tools is understood as the result of both a favorable effect by decrease of ductility and an unfavorable effect of work hardening.
  • Effects of Si and Mn Contents on the Tensile Properties of Normalized Medium Carbon Steels

    pp. 112-124

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    Effects of Si and Mn additions on the tensile properties of medium carbon steels have been investigated to assess the utility as non-ardened high strength steels. Results concerning 0.3%C-Si-Mn steels are summarized as follows:
    (1) The tensile strength increases 9.5 kg/mm2 per 1% of Si+Mn up to the transitional value of 1.7%Mn, over which the strength is raised only with a rapid fall of elongation due to lowtemperature transformation.
    (2) The larger the Si/Mn ratio in the steels up to about 6, the higher strength can be obtained with little decrease of elongation, so far as the steels keep ferrite-pearlite structure.
    (3) The limit to strengthen these steels holding at least 18% elongation is estimated to about 90 and 70 kg/mm2 for tensile and yield strengths respectively. Concerning with 0.47%C-Si-Mn steels,
    (4) The larger the Si/Mn ratio up to about 2, the higher elongation can be obtained.
    (5) The limit to strengthen these steels holding at least 18% elongation is estimated to about 977and 63 kg/mm2 for tensile and yield strength respectively.
  • The Influence of the Inclination and Direction of Specimen Surface on Atmospheric Corrosion of Steels

    pp. 125-130

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    The corrosion rate of a steel and the morphology of the rust formed are influenced by the inclination and direction of the steel surface exposed to the atmosphere. Sheets of a carbon steel and a low alloy steel one side of the surfaces of which was coated by resin paint were positioned at the inclinations of 0, 30, 60 and 90 degrees to the horizon, facing skywards and groundwards. Atmospheric exposure test has been carried for two years. Corrosion rate of steels, sulfate content of rust, and retained water content of rust layer after rain fall have been studied.
    The results are as follows;
    (1) Corrosion rates of the groundward surfaces were greater than those of the skyward surfaces and decreased with steepening the inclination of the surfaces. Corrosion rates of the skyward surfaces positioned horizontally and vertically were greater than those of the surfaces inclined at the intermediate angles.
    (2) The sulfate content of rust varied with the inclinations of the surfaces on which the rust was formed. This fact seems to relate to the amount of rain running along the surface of the specimens.
    (3) The sulfate content of the rust could explain the dependency of corrosion rates of the groundward surfaces on the inclinations of the surfaces. As to the corrosion behavior of the skyward surfaces, however, the water retaining property of the rust layer after rain fall, which shows the same dependency on the exposure inclinations as the corrosion rates, must be taken into consideration.
  • Dissolution of Iron in Molten Zinc in Continuous Sheet Galvanizing

    pp. 131-141

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    In continuous sheet galvanizing process, dissolution of iron into molten zinc results in a fairly great amount of dross. In order to decrease the harmful dross, the amounts of dissolved iron into galvani- zing bath have been measured in several conditions.
    (1) According to our method studied here the iron loss by the reaction between molten zinc and solid iron is divided into two quantitative terms; a quantity dissolved and that in alloy layer.
    (2) Under a condition which corresponds to the practical continuous sheet galvanizing process, the above mentioned quantities are both in the range of 0.1-0.5 g/m2. For example, in the case of 10 seconds immersion in a 0.18% Al bath, quantity of dissolved iron is 0.39±0.09 g/m2 and the quantity of iron in alloy layer is 0.24±0.10g/m2.
    (3) The quantity of dissolved iron obtained here corresponds fairly well to the amount of drossformed in practical processes.
    (4) The incubation period is 0.5-1 min or 5 min depending on the phase in alloy layer; the former corresponds to δ phase and the latter to Fe2Al5 phase.
  • Determination of Various Components in Coating of Mild Steel Arc Welding Electrodes by Atomic Absorption Spectrophotometry

    pp. 142-151

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    We have studied the method for determination of SiO2, TiO2, Al2O3, Fe, Mn, CaO, MgO, Na2O, and K2O in coating of mild steel arc welding electrodes by atomic absorption spectrophotometry.
    In this study the working conditions for the determination of these components, the influences of reagents for fusion, acids, and diverse coexisting components, and the suppression of the interferences were examined systematically.
    A new method using a polyethylene plate mask to decrease absorbance of the element that has a high sensitivity for measurement and a high content in the sample was also examined, and it was applied to the determination of Mg.
    The methods were actually applied for the routine analysis of coating of the electrodes.
    Satisfactory results were obtained; the methods were simple, rapid, reproducible, and accurate enough to be employed to analyses of various components in silicates, TiO2 in ilmenite and iron sand, and Mg in dolomite, which were used as raw materials of the coating.
  • Work Hardening of Composite Materials

    pp. 152-170

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  • 抄録

    pp. 171-176

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