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

Tetsu-to-Hagané Vol. 76 (1990), No. 4

  • Future Aspects of State Analysis of Ferrous Materials

    pp. 483-494

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  • Plastic Deformation Mechanisms in α Titanium

    pp. 495-502

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  • VAMAS International Joint Research on Testing Method and Evaluation of Creep Crack Growth

    pp. 503-514

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  • Removal of Impurities in Iron Ore by Na2O-B2O3 Flux

    pp. 515-522

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    Removal of impurities in fine-grained iron ore with Na2O-B2O3 flux and its mechanism have been investigated by use of the flux leaching and the recrystallization methods. The isolated impurities as well as those on the surface of ore particles were removed by the former method, while the inclusions prerent inside the particles together with the above-mentioned impurities were removed by the latter method. In the flux leaching method, the high yield of iron oxide and the low content of impurities were obtained at flux compositions of Na2O·2B2O3 and 2Na2O·5B2O3. The contents of Si, Al, Ca, Mg, Mn, V decreased with increasing temperature from 850°C to 1450°C ; these observations were explained by the break up of ore particles and the increase of the amount of recrystallized iron oxide. About 80% of iron oxide yield was obtained in both flux treatments by use of the Na2O-2B2O3 flux.
  • Catalytic Activity of Reduced Iron Pellets for Water Gas Shift Reaction

    pp. 523-530

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    In order to investigate the catalytic activity of Reduced Iron Pellets (RIP) to the water gas shift reaction, hematite pellets were reduced at different conditions of temperature (873K-1 273 K) and reducing gas (H2 and CO) to make catalysts. Rate of water gas shift reaction was measured by detecting the concentration change of gas during shallow packed beds which consisted of the RIP as catalyst. Reaction rate of the water gas shift reaction catalyzed with the RIP was apparently represented within the experimental conditions by the equation on the basis of mass action law. Apparent activation energy of the rate constant measured was 8.2-24 kJ/mol for H2 reduction and 23-45 kJ/mol for CO reduction respectively.
    The RIP reduced at lower temperature or by H2 gas was found to have higher catalytic activity than that reduced at higher temperature or by CO gas. Another phenomenon obseved was the decrease in the catalytic activity of the RIP when the experimental temperature for the water gas shift reaction exceeded the temperature of reduction. According to the measurements of the physical properties of the RIP such as pore size distribution, specific area and porosity, decay of the catalytic activity was caused by the change of the physical properties of the catalysts, mainly decrease of specific area.
  • Disintegration of Pseudo-particles in the Moving Bed

    pp. 531-537

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    Material disintegration in the blast furnace should be relative not only to the material strength but also to the stresses in the furnace. However, there are only few papers on the particle disintegration related to stresses.
    Disintegration of pseudo-particles in the moving bed was investigated by using the reduced scale model of Hirohata No. 4 blast furnace. Normal stresses in the model were also measured and analyzed in relation to the particle disintegration.
    As a result, the followings were clarified. Most of the particle disintegration occured at the periphery of the model. The generation rate of fine particle in the lower part was higher than that in the upper part. Particles were highly disintegrated when a large dead zone was temporarily formed at the wall. Through the comparison of the stresses with the particle strength, it was suggested that the shear stress causes the particle disintegration. Maximum shear stress possibly acts on the particles at the boundary of the temporary dead zone. The shear stress possibly varies in accordance with the temporary dead zone growth.
    When the strength of the materials charged into the blast furnace is lower than the shear stress, the materials will enormously be disintegrated.
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  • Flotation of Kish Graphite Precipitated from Carbon-saturated Iron Melt

    pp. 538-544

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    The flotation of carbon precipitated from carbon-saturated iron melt has been studied as a function of temperature drop, cooling rate, stirring and sulfur content in metal. Under the experimental conditions such as temperature (1450°C), the temperature drop (50 240°C) and the cooling rate (14.6 150°C/h), the amount of carbon floated to the top of the metal phase was observed to increase with increasing the degree of the temperature drop and with decreasing the cooling rate. The rate of flotation for the flakytype graphite (Kish graphite) was much faster than that for the sphere-type precipitated carbon. Furthermore the rate of flotation was accelerated by stirring, and increased by the addition of sulfur.
  • Effect of Oxygen Partial Pressure in Atmosphere on Thermoelectromotive Force of Solid Electrolytes

    pp. 545-551

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    A dependency of thermoelectromotive force of solid electrolytes, zirconia stabilized by 11 mol%CaO, 9 mol%MgO and 15mol%MgO, on oxygen partial pressure in atmosphere were observed. Oxygen partial pressure, temperature difference and temperature are controlled between 0.21 and 5×10-19 atm, between 50 and 400°C as well as between 700 and 1250°C, respectively.
    Experimental results are as follows : above about 5×10-5 atm of oxygen partial pressure in atmosphere, the lower oxygen partial pressure, the larger thermoelectromotive force. Between about 5×10-5 and 5×10-15 atm, the lower oxygen partial pressure, the smaller thermoelectromotive force. Under about 5×10-15 atm, the lower oxygen partial pressure, the larger thermoelectromotive force.
    The complex phenomenon can be explained by an assumption that the observed thermoelectromotive force is consisted by that induced by ion and electron.
  • Oxidation Rate of Carbon in Iron by Iron Oxide in Slag

    pp. 552-559

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    The rate of oxidation of C in Fe-C, Fe-C-Si and Fe-C-P melts ( [%C] = 4.4 ) by FeO in Li2O-CaO-SiO2 slag has been investigated under the condition of mechanical stirring at 1300°C. The initial concentration of FeO in the slag was varied from 4.6 to 20% and those of Si and P in the melt were varied from 0.004 to 0.33% and from 0 to 0.1%, respectively. In the experiment for investigating the effect of P in the slag on the C oxidation, the initial concentration of P in the slag was changed in the range of 02%. It is found that the C oxidation rate greatly reduces when a small amount of P is added to the slag while P in the metal has no significant effect on the C oxidation. The rate of C oxidation decreases with increasing Si concentration in the metal.
    A mathematical reaction model is proposed for the oxidation of C in the metal by FeO in the slag. The model assumes the existence of CO bubbles in the slag-metal interfacial region. Three rate determining steps are taken into account, namely chemical reaction at the gas-slag interface, mass transfer of CO2 in the bubble and chemical reaction at gas-metal interface. The experimental result is in good agreement with that calculated from the model.
  • Optimization of the Blowing Sequence in a Top and Bottom Blowing Converter Containing Pretreated Hot Metal

    pp. 560-567

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    Experimental and theoretical studies have been carried out to clarify metallurgical reactions in combined blowing converters affected by the oxygen flow rates from the top and the bottom of the furnace.
    The 5t combined blowing converter showed the decrease in oxygen content in the bath with the increase in the oxygen flow rate from the bottom, while the 5t bottom blowing converter showed the decrease in oxygen content with the decrease in the oxygen flow rate. Thease experimental results are interpreted in terms of an index, I, related to the inverse of the oxygen efficiency used for decarburization, which has been introduced by considering the different reaction sites brought by the top blown and the bottom blown gases. Oxygen content in steel melt and ( T. Fe) in slag decrease with the decrease in the I value from LD to Q-BOP, which indicates that the I is suitable for characterizing metallurgical reactions.
    The metallurgical reactions at blow end can be controlled by changing the oxygen flow rates of top and bottom blowings, based on the aimmed I value.
  • Production of Titanium Powders by the Calciothermic Reduction of TiO2

    pp. 568-575

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    According to the measurements of equilibrium oxygen concentration in Ti under Ca-CaO co-existence, the deoxidation limit is 500 ppm at 1273 K. On the basis of these data, preparation of Ti powders have been carried out by reduction of TiO2 using saturated Ca vapors, liquid Ca and CaH2 powders at 1273 K and subsequent rinsing of CaO in the aqueous solution of HCl, CH3COOH or NH4Cl.
    The oxygen and calcium levels in the Ti powders reduced by the saturated Ca vapors and the liquid Ca were not below 2000 and 1000 ppm, respectively. This was attributed to the CaO which were confined inside the sintered Ti particles and could not be exposed to the rinsing solution.
    Reduction of the TiO2-CaO mixtures has led to the residual oxygen with the range of 1000-2000 ppm, thus the presence of CaO in the starting oxide was effective to control the sintering between reduced Ti powders. The particle size of the reduced Ti was 1-10μm.
    Reduction of TiO2 by mixing with excess amount of CaH2 powders could eliminate oxygen below 700 ppm which is close to the deoxidation limit for Ti by Ca of activity of unity.
  • Proposal of Control System of Surface Brightness of Rolled Sheet in Cold Rolling

    pp. 576-583

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    The purposes of this study are to examine systematically the effect of tribological factors on surface qualities of rolled sheet, and to propose a system for estimating and controlling the surface qualities of rolled sheet before rolling. The rolling experiments were carried out, changing the rolling speed, the reduction, the viscosity of lubricant and the surface roughnesses of roll and sheet. The surface roughness and the surface brightness of rolled sheet were measured and the surface photographs were taken. From these experimental data, when the surface roughnesses of roll and sheet are smooth, the surface brightness decreases with increasing the rolling speed and the viscosity of lubricant, and conversely the surface roughness increases. On the other hand, when the surface roughnesses of roll and sheet are rough, they have a great influence upon the surface qualities of rolled sheet. In the former case, the dependence of the rolling speed, the viscosity and the surface roughnesses of roll and sheet before rolling on the surface brightness is equal to that on the oil film thickness. Consequently, the surface brightness is expressed as a function of the oil film thickness. In the latter case, the surface brightness is expressed as three functions of the oil film thickness and the surface roughnesses of roll and sheet before rolling. By using the relations, a system for estimating and controlling the surface brightness before rolling can be constructed.
  • Development of the Full-Automated Mechanical Testing System for Steel Products

    pp. 584-591

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    Mechanical testing in steel production plays an important role in both quality assurance through the materials inspection of various high grade steel products, and stabilizing or upgrading the steel quality through supplying the production analysis data. Authors have been engaged in developing the updated materials testing system for a more accurate and rapid testing process. However some problems still remain in the area of delivery time of test results and worker's job efficiency. In June 1988, we developed a new system for total factory automation of the full-automated materials testing at Fukuyama Works, NKK Corporation, including the automatic machining process of test specimens and a computer control system first of their kind anywhere in the world. This paper details the aims of the development and the new machining techniques.
  • Morphology and Microstructure of Pulsed Electrodeposited Zinc-Iron Binary alloy

    pp. 592-597

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    Zinc-iron electrodeposited sheet steels have been widely adopted for automobile bodies for their improvements in the corrosion resistance and paintability. In princiles, these properties depend on the crystal structure, morphology and microstructure of deposits. The deposit with various pulse off time have been electrodeposited from sulfate bath and examined by scanning microscopy and X-ray diffraction. All the deposits consist of the η-and Γ-phases, and the deposit morphology consists of hexagonal columnar crystals and Γ-phase granular crystals. These hexagonal columnar crystals consist of the η-phase plates and fine granular Γ-phases dispersively precipitate within the grain and grain boundary of these η-phase plates.
    For the 1.0ms pulse off time deposit, the granular crystals form only on the (00.1)η of hexagonal columnar crystals. For the deposit more than 1.0ms, these granular crystals form both on the (00.1)η and {10.0}η of hexagonal columnar crystals. The amount of granular crystals increases as the increase of off time. Also the deposit cross sectional observation reveals the increase of white microstructures whose zinc contents are less than dark microstructures. The X-ray diffraction shows the decrease of diffraction intensity and number of diffraction lines of η-phase, and the increase of those of Γ-phase.
  • Effect of Anodic Oxidation Treatment prior to Reflow on Uniformity of Tin Layer on Tinplate

    pp. 598-605

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    The uniformity of the tin layer on tinplate formed along the surface roughness on steel generally decreases after the reflow. We estimated the uniformity of the tin layer by using the EPMA, and quantitatively investigated the effect of the anodic oxidation treatment prior to the reflow on the uniformity of the tin layer.
    The experimental results are summarized as follows.
    (1) The morphology of the surface of the tin layer which was reflowed after the anodic oxidation treatment was similar to that of the as electrodeposited surface.
    (2) The uniformity of the tin layer on tinplate was improved by the anodic oxidation treatment prior to the reflow.
    (3) The occurrence of the iron sulfide products, which occurred at the deformed areas on lacquered tinplates after the retort test in the solution containing sulfide ions, depended on the uniformity of the tin layers.
  • Fracture Toughness of Ti-8Al-1Mo-1V

    pp. 606-613

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    Effect of microstructure on fracture toughness of a near α Ti-8Al-1Mo-1V alloy was systematically examined.
    At 0°C, β-processed specimens with acicular microstructure had higher fracture toughness at a given strength than those with equiaxed microstructure, because the former had a greater crack extension resistance than the latter. The embrittling phase, α2 phase, which precipitated during furnace cooling after annealed at 650950°C, reduced fracture toughness by more than 20 percent although that increased tensile strength. Precipitation of α2 phase had a great influence on crack initiation and reduced CTOD value at crack initiation, δi, by 50 percent.
    At-196°C, the specimens with acicular microstructure had higher fracture toughness than those with equiaxed microstructure similar to those tested at 0°C. The latter had lower fracture toughness than that of Ti-6Al-4V with equiaxed microstructure at a given strength, because the crack initiation of Ti-8Al-1Mo-1V were lower than that of Ti-6Al-4V.
    It is concluded that the relationship between microstructure and crack initiation or crack extension resistance properties of microcracks preceding unstable fracture accounted for the changes in fracture toughness of Ti-8Al-Mo-1V.
  • Acceleration of α Precipitation and Strengthening of Ti-15V-3Cr-3Sn-3Al Alloy by Two Step Aging

    pp. 614-621

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    Acceleration of α precipitation and strengthening of metastable β titanium alloy, Ti-15V-3Cr-3Sn-3Al (15-3), by 2 step aging was investigated.
    Ti-15V-3Cr-3Sn-3Al alloy shows a phase-separation of β phase in low temperature aging at 573K after β solution treatment. Precipitation of small particles of α phase in the second stage high temperature aging was accelerated by phase separation in which β' phase precipitates, because β' precipitates provided the nucleation sites of α precipitates.
    Higher strength by shorter total aging time could be attained by 2 step aging in the combination of 1st step aging of 573K, (14.428.8)ks aging and 2nd step aging of (753813)K, (3.686.4)ks aging.
  • X-ray Fluorescence Analysis of Superconductor YBa2Cu3O7-δ by Glass Bead-FP Method

    pp. 622-629

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    In the accurate analysis of ceramic powders with few or no available standards by X-ray fluorescence spectrometry, the glass bead technique combined with the Fundamental Parameter (FP) method is suitable. As an example of ceramic powder analysis, we determined Y2O3, BaO, and CuO in a superconductor YBa2Cu3O7-δ with this combined method.
    The results obtained were as follows:
    1) Satisfactory glass beads with near-infinite thickness to both incident and fluorescent X-rays were found to be prepared from 10g of Na2B4O7, 1g of sample, and 0.20g of potassium iodide.
    2) The calculation of the absorption enhancement effects for the YKα, BaKα, and CuKα lines got the results below. The YKα line is more absorbed by substituting Y2O3 in the mixed reagents (Y2O3-BaO-CuO) with either BaO or CuO. The BaKα line is enhanced [a little more absorbed] by substituting BaO in the mixed reagents with CuO [Y2O3] The CuKα line is more absorbed [a little enhanced] by substituting CuO in the mixed reagents with BaO [Y2O3].
    3) Y2O3, BaO, and CuO in the superconductor were determined with the good accuracies (σd'S) of 0.11wt%, 0.18wt%, and 0.19wt%, respectively by the combined method.
  • H.BESSEMERのもうーつの夢

    pp. 630-631

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  • 気になる「よそ様」の事情/'90年代における鉄鋼材料研究でのコンピュータ利用

    pp. 641-642

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