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ONLINE ISSN: 1883-2954
PRINT ISSN: 0021-1575

Tetsu-to-Hagané Vol. 65 (1979), No. 3

  • 冶金技術の一貫性について

    pp. 329-330

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  • The Reduction Behavior of Synthetic Chromites by Carbon

    pp. 331-340

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    The chromites shown below were prepared synthetically and reduced by graphite powder under a CO atmosphere: FeCr2O4 (Sp 1), MgCr2O4 (Sp 2), (Fe0.5Mg0.5) Cr2O4 (Sp 3), (Fe0.5Mg0.5) (Cr0.8Al0.2) 2O4 (Sp 4), and Mg (Cr0.6Al0.4) 2O4 (Sp 5).
    The results obtained are as follows:
    1) In the case of the pure iron chromite Sp 1, the reduction of FeO component preceded that of Cr2O3. With the progress of the reduction, the metallic products changed in the following order: Austenite→austenite+ (Fe, Cr) 3C→ (Fe, Cr) 3C+ (Cr, Fe) 7C3→ (Cr, Fe) 7C3.
    2) The reduction of complex chromites containing iron oxide (Sp 3 and Sp 4) took place in two stages. In the first stage with the reduction of the FeCr2O4 component, FeO and Cr2O3 were reduced simultaneously at temperatures higher than 1150°C, although the reduction of FeO preceded at lower temperatures. The reduction of the MgCr2O4component (the second stage) required higher temperatures. It started at 1200°C and proceeded rapidly at temperatures higher than 1250°C in the case of Sp 2 and Sp 3. The rapid progress of the reduction of MgCr2O4 component of Sp 4 and Sp 5 which contained Al2O3was only encountered at temperatures higher than 1330°C.
    3) The metallic product of the chromites Sp 3 and Sp 4 was (Cr, Fe) 7C3in either reduction stage of the FeCr2O4 and MgCr2O4 components. The final product of the reduction of the chromites Sp 2 and Sp 5 was Cr3C2, while an unidentified phase appeared during the course of the reduction and was considered to be chromium oxycarbide.
  • Mechanism of Heat Transfer in Packed Beds Having Fused and Unfused Layers

    pp. 341-348

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    Model experiments at low temperature were carried out for the simultaneous gas flow and heat transfer in the packed beds which have the double structure of fused and unfused layers providing different resistances to gas flow in order to elucidate the mechanism of heat transfer in the fused zone in the blast furnace.
    Temperature changes were observed at various positions in the bed with unfused layer of spherical alumina and fused layer which was made of polystyrene particles.
    In the case of the low degree of fusion, the fused layer is considered to be heated up principally by heat exchange between gas and solid, because the preheated gas can flow through the fused layer. On the other hand, for the high degree of fusion, temperature decreases from the boundary between fused and unfused layers to the core of the fused layer. This temperature gradient allows conductive heat transfer from the alumina layer to the fused layer.
    The experimental results show good agreement with the values predicted from the mathematical model which has been developed in the previous paper.
    Furthermore, the effective thermal conductivity of the fused layer was measured with various degree of fusion. Results obtained was expressed by an empirical equation with respect to the degree of fusion. The equation was used for the prediction of temperature changes in the bed by the mathematical model.
  • Laboratory Evaluation of Physical and High Temperature Properties of Commercial Pellets

    pp. 349-357

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    Sampled commercial pellets are classified into 6 types according to the chemical composition of gangue in pellets, that is SiO2-type, (SiO2+Al2O3) -type, high total Fe-type, CaO-type, (CaO+MgO) -type, and the rest.
    This paper mainly evaluated high temperature-reducing properties of 44 kinds of commercial pellets in the world, which were measured with one-ball softening test under load.
    As to beginning temperatures of softening of acid pellets, those of high total Fe-type pellets are higher, those of SiO2-type pellets with large amounts of gangue minerals are lower, those of (SiO2+Al2O3) -tyep pellets vary widely depending on indurating conditions and SiO2/Al2O3ratio in them. Beginning temperatures of softening of self-fluxed pellets are in the highest level.
    Melting down temperatures of pellets are linearly increased with the increase of total Fe-contents in acid pellets and that of melting points of gangue minerals in self-fluxed pellets.
    Therefore, in pelletizing of low grade ores, addition of MgO-contained minerals is contributed to improvement of high temperature properties. In acid pellets, the range of SiO2/ (SiO2+Al2O3) ratio =0.75-0.85 in raw ores should avoid in order to attain better high temperature properties of pellets.
    x

    Readers Who Read This Article Also Read

    1. Heat Transfer Phenomena in Immersion Cooling of Heated Steel Plate and Influence of Water Stirring on Heat Transfer Tetsu-to-Hagané Vol.64(1978), No.1
    2. 第97回講演大会討論会講演概要 Tetsu-to-Hagané Vol.65(1979), No.2
    3. 第95回講演大会討論会講演概要 Tetsu-to-Hagané Vol.64(1978), No.2
  • Study of Ore and Coke Distribution in Blast Furnase Carried out on a Full Size Model

    pp. 358-367

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    The distribution of are and coke burden composed of pellet and sinter has been investigated by a full size model. Falling trajectory of materials was measured in both the model and a blast furnace, and the equation of the trajectory to be applied to the design of charging equipment was led theoreticarlly. It was found that the inclination of ore and coke layers varied with charging sequence and dumping volume. It was clearly shown that the radial distribution of are and coke depended on coke volume, ore to coke ratio in charging burdens, charging sequences and pellet content in burdens.
    Results of the model investigations were applied to commercial blast furnaces. The distribution of of ore to coke ratio with gas flow was calculated with the results of full size model and the are to coke ratio was shown to be reduced at central part with high gas flow velocity in blast furnace.
    By comparing the results of full size model with those of a onetenth reduced model, it was found that the mixed layer of are and coke was formed and the are to coke ratio was decreased in the central part of the reduced model. It was reasoned that the ratio of particle weight of are and coke should be taken as one of the scaling factors in the reduced model.
  • Fundamental Study on the Behavior of Pellets at Higher Temperature in Blast Furnace

    pp. 368-376

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    In order to clarify the behavior of pellets and sinters in the reduction and melting process in the blast furnace, some phenomena, such as the retardation of reduction at higher temperature, the exudation of FeO-containing slag and the meltdown, were investigated. The results obtained are as follows:
    1) Some kinds of burdens show strong retardation of reduction at higher temperature (1200°-1250°C).
    2) When a reduced sample is held at 1300°-1400°C during several minutes, the exudation of FeO-containing slag to its surface takes place.
    3) In the meltdown test, the meltdown behavior is different among various kinds of burdens according to the factors such as gangue volume and composition of burdens and the reducing conditions.
  • Effect of Fluid Flow on Columnar-Equiaxed Transition in Solidification

    pp. 377-382

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    The effects of fluid flow and solidification conditions on the columnar-equiaxed transition are investigated. The ratio, R, of heat flux at dendrite tip to that at dendrite stem is introduced as a parameter which characterizes the columnar-equiaxed transition (For R>1, columnar grains grow, whereas for R<1, equiaxed grains grow). This heat flux ratio, R, is calculated for Fe-0.5%C alloy under varying condition by using the finite element method. The heat flux ratio thus calculated indicates, in good agreement with previously reported observation, that the columnar-equiaxed transition occurs when the temperature gradient decreases to about 5°C/cm under natural convective flow faster than 0.3cm/sec, and columnar grains come to grow again as the temperature gradient further decreases to less than 1°C/cm. For flow slower than 0.3cm/sec, only columnar grains are shown to grow.
  • The Oxide Produced by Addition of Aluminium to Molten Iron

    pp. 383-390

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    This study was carried out to investigate the oxides formed from molten iron with addition of small amount of aluminium during cooling and solidifing. Electrolytic iron with addition of small amount of aluminium (0.05 and 0.1 wt%) was melted in a levitation furnace of purified Ar-gas atmosphere, and molten iron was kept at 2200°-2300°C for about 40 sec or at 1580°-1610°C for 1-2 sec. Then, the molten iron was quenched by moulding it into a copper mould or putting it between two copper plates. The oxides formed during cooling and solidifing were extracted from the quenched iron by the Iodine-Alcohol method and identified by the X-ray diffraction.
    The oxides identified were hercynite, γ-, κ-, θ-and α-Al2O3 in the case of quenched iron with addition of 0.05 wt%Al and γ-, κ-, θ-and α-Al2O3 in the case of quenched iron with addition of 0.1 wt%Al. It was considered from these results that γ-, κ- and θ-Al2O3's were the oxides of intermediate state of change from hercynite to α-Al2O3 by the reaction of hercynite with aluminium in molten iron.
  • Eutectic Conjugation in Fe-Mn-S System

    pp. 391-398

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    The conjugation of <Fe-(Mn, Fe) S-(Fe, Mn) S>, <Melt-Fe-(Fe, Mn) S> and <Melt-Fe-(Mn, Fe) S> in the Fe-Mn-S ternary system with up to 4% of manganese in iron phase, was investigated as the first approach to understand kinetics of sulfide formation in steel, and the compositions of all phases were determined in the temperature range from 670°C to 1500°C.
    The results are summarized as follows:
    (1) The three-phase conjugation among melt, iron and (Mn, Fe) S was observed in the temperature range from 1004°C to 1500°C.
    (2) No evidence was found for the intersection of the eutectic line with the miscibility gap, proposed by Wentrup.
    (3) The solubility of sulfur in iron abruptly decreased at 1371°C from 0.12% to 0.05% with the δ→γ transformation of iron.
    (4) As a result of the peritecto-eutectic reaction, four phases of melt, iron, (Mn, Fe) S and (Fe, Mn) S coexisted at 1004°C.
    (5) Below the peritecto-eutectic temperature, both three-phase conjugations of <Melt-Fe-(Fe, Mn) S> and <Fe-(Mn, Fe) S-(Fe, Mn) S> were stable. The former met Fe-FeS binary at 988°C, its eutectic temperature.
  • Changes in Thermoelectric Power and Electrical Resistivity in the Processes of Cold Rolling and Isochronal Annealing in Pure Iron

    pp. 399-407

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    Changes in thermoelectric power, electrical resistivity and Vickers hardness in the processes of cold rolling and isochronal annealing at 30 min/20°C step were observed in J. M. pure iron and electrolytic iron decarburized and denitrided. The cold rolling and isochronal annealing processes could be separated into different regions by plotting the observed values on absolute thermoelectric power (S0°C) -conductivity (1/ρ0°C) diagrams.
    From the S0°C-1/ρ0°C diagram for J. M. pure iron, the average gradient of the lines corresponding to increase and decrease of dislocation density was found to be 500±100 μV·μΩ·cm/deg. The cold rolling process in electrolytic iron could be separated into three regions. The 1 st region which was confined within about 10% reduction was considered to be influenced by segregation of nitrogen and carbon atoms onto dislocations. The onset of 3rd region above 40% reduction was explained as due to vacancy formation. On annealing over 500°C, dissolution of nitrogen and carbon atoms took place in both the specimens, and the gradient of the lines on S0°C-1/ρ0°C diagram was 130±50 μV·μΩ·cm/deg.
  • Influence of Various Heat Treated Structures on the Machining Behaviour of Medium Carbon Low Alloy Steel

    pp. 408-417

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    The behaviours of chip formation during machining heat treated SCM 3 steel with various microstructers were investgated. The obtained results are summarized as follows:
    1) Concerning the sufficient condition to the formation of built up edge, this reseach elucidated a new mechanism different from the previous studies, namely the temperature at front surface of built up edge was higher than that outside of tool surface. This seems to be related to strain rate distribution, degree of blue shortness and generated heat at cutting zone.
    2) Cutting force (R) in turning decreased with the hardness in these samples. This can be explained from a relation between R and shear angle (φ) being dependent on the thickness of deformation flow laver (Fμ) of chip. The formation mechanism of Fμ should also be considered.
    3) In the range of this study, a new equation to caluclate the shear angle (φ) of chip was obtained by replacing the hardness of steel and the cutting speed with the observed Fμ.
  • Deep Drawability and Stretchability of Pure-iron Single Crystals

    pp. 418-424

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    A stydy has been made of the orientation dependence of drawability and stretchability, using pureiron single crystals. Disk specimens (thickness: 0.5 mm, diameter: 20 mm) with various planar orientations have been prepared and subjected to deep drawing and stretching by means of mini press machine. The results show that the variation of deep drawability and stretchability can be explained in terms of plastic strain ratio (γ) and work-hardening exponent (n), respctively, and that both deep drawability and stretchability are excellent for planar orientations {111}, {122}, and {123} having high values of n as well as γ. It is also shown that the variation of deep drawability with planar orientations in the single crystals is directly related to the texture dependence of deep drawability in commercial steels. Contrary to this, the texture dependence of stretchability is not obvious because the exponent n depends markedly upon the grain size of steels.
  • Behaviour of Transformation Induced Plasticity of 18%Ni Maraging Steels

    pp. 425-432

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    The behaviour of transformation induced plasticity under tensile test has been experimentally investigated at various temperatures between 300°C and room temperature, and at various strain rates for 18% Ni maraging steels. The results obtained are as follows:
    (1) Total elongation up to about 60% is obtained at the optimum condition (strain rate of below 0.03/min and temperature of 225°C for the 210 kg/ mm2 class maraging steel or temperature of 275°C for the 245 kg/mm2 class one).
    (2) The “n value” (work hardening exponent) is not constant with increase in strain, and have two peaks at the optimum condition mentioned above. The first peak indicates the characteristic of work hardening of austenite and the second one depends on the work hardening by transformation.
    (3) Total elongation is constant (about 60%) at strain rate of below 0.03/min, decreases with increase in strain rate in the range of 0.03-0.3/min and is constant (about 30%) over 0.3/min at above mentioned temperature. Decrease of total elongation in high strain rate depends on the heat of deformation.
    (4) In the double stage tensile test, the optimum temperature in the second stage to get maximum total elongation for the 210 kg/ mm2 class maraging steel, which is 20% prestrained at 300°C in the first stage, is 20 degrees lower than that of single stage tensile test, and the range of temperature to get more than 40% total elongation is 6 times of that of sigle stage tensile test.
    (5) The tensile strength and optical microstructure at room temperature are not significantly affected by the transformation induced plasticity.
    x

    Readers Who Read This Article Also Read

    1. Heat Transfer Phenomena in Immersion Cooling of Heated Steel Plate and Influence of Water Stirring on Heat Transfer Tetsu-to-Hagané Vol.64(1978), No.1
    2. 第97回講演大会討論会講演概要 Tetsu-to-Hagané Vol.65(1979), No.2
    3. 第95回講演大会討論会講演概要 Tetsu-to-Hagané Vol.64(1978), No.2
  • Hydrogen Induced Cracking of Steel Pipes due to Long Duration Exposure in Wet Hydrogen Sulfide Environment

    pp. 433-442

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    In order to investigate the hydrogen induced cracking (HIC) susceptibility of pipe sample in sour gas service, the container type specimen was used, of which body was made from the pipe tested. Three kinds of commercial large size line pipes of API 5LX-60 and X-65 grades were examined for this study. After the half of the volume was filled with test solutions, pure H2S gas or mixture of N2 and H2S was bubbled. The test solutions were synthetic sea water, pure water and synthetic sea water mixed with crude oil. After controlling the concentration of H2S, the containers were kept for about one year as they were. In order to know the development of cracking during the test, ultrasonic testing was used.
    As the results of this investigation, it was clarified that the development of HIC was due to the environment, steels, mill scale and so on. It was also obtained that HIC susceptibility of steels evaluated by the standard HIC test method which was recently developed by Kowaka et al, correlated wtih that evaluated by this long duration exposure test, although the investigation of environmental factors was important for the prevention of HIC.
  • Determination of Free Sulfur and Thiosulfate Sulfur in Substance Containing Sulfur of Various State

    pp. 443-449

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    The paper describes determination of free sulfur and thiosulfate sulfur in substance containing sulfur of various state using two methods-the extraction-combustion method and vaporization-combustion method.
    The outline of procedure is as follows:
    (1) Determination of free sulfur
    Sample is treated with 100 ml of carbon tetrachloride for 6 hours in Soxhlet's extractor. In this condition, free sulfur in sample is dissolved in solvent. Extracted liquid is evaporated by heating at under 100°C in alumina boat and free sulfur is educed. Free sulfur in material educed is analysed with conventional combustion method.
    (2) Determination of the sum of free sulfur and thiosulfate sulfur
    Sample is analysed by the apparatus of Fig. 1, and then free sulfur and the free sulfur produced from thiosulfate in sample is vaporized and oxidized by oxygen. Gas including sulfur oxides is absorbed with hydrogen peroxide solution. Sulfur in absorbent is determined by arsenazo III titration method.
    (3) Determination of thiosulfate sulfur
    Thiosulfate sulfur can be obtained as two times of the value of difference between the analytical values of the vaporization-combustion method and extraction-combustion method.
  • Fracture Surface Analysis by X-Ray Diffraction Techniques

    pp. 450-460

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  • Current Status and New Trends of Corrosion Preventive Technology for Marine Steel Structure

    pp. 461-470

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  • 抄録

    pp. 471-474

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