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

Tetsu-to-Hagané Vol. 95 (2009), No. 6

  • Effect of Iron Ore and Coal Properties on Reaction Behavior of Carbon Composite Iron Ore Briquette

    pp. 453-459

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    DOI:10.2355/tetsutohagane.95.453

    Four kinds of carbon composite iron ore briquette (CCB) were made by mixing two kinds of iron ores and coals that have different properties such as hematite, magnetite, fluidity and non-fluidity coal. The reaction behavior of those CCB was examined at the temperatures of 1273–1473K in N2 gas atmosphere. The effect of iron ore and coal properties on reaction behavior of CCB was investigated. In the case of CCB that mixed fluidity coal, gasification and reduction rates of the CCB were fast because the contact of iron ore and coal improved. In the case of CCB that mixed hematite ore, reduction rate of the CCB was fast because the reduction rate of hematite ore is faster than that of magnetite ore. Therefore, the reaction rate of CCB that mixed fluidity coal and hematite ore was the fastest in samples.
  • Evaluation of Mechanical Properties in Microscopic Textures of Coke before/after Solution Loss Reaction

    pp. 460-466

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    DOI:10.2355/tetsutohagane.95.460

    In this study, the elastic modulus of coke microscopic textures is measured with a nano-indentation method to investigate the effect of solution loss reaction on the mechanical properties of coke matrices. In addition, elemental analysis by means of SEM-EDS is carried out to reveal the effect of solution loss reaction on degradation of coke elastic modulus.
    The results are summarized as follows:
    (1) The elastic moduli of active components and inerts decreased with an increase in conversion.
    (2) The nano-scale pore increased with an increase in conversion.
    (3) A decrease in elastic modulus under the condition that reaction rate is a rate controlling step is greater than that under the condition that either reaction rate or mass transfer is a rate controlling step in active components.
    (4) The results of SEM-EDS show that there are the catalytic mineral matters in fragmentary texture.
    (5) A decreasing in elastic modulus of inerts is greater than that of active components because ashes in inerts work as the catalysts of solution loss reaction.
  • Effect of Residual Volatile Matter on Reduction Reaction between Semi-coal-char and Iron Oxide

    pp. 467-472

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    DOI:10.2355/tetsutohagane.95.467

    Carbon composite pellets intentionally including residual volatile matter (V.M.) were proposed to decrease the starting temperature for reduction reaction of carbon composite iron ore agglomerate under a rising temperature condition, such as in a blast furnace shaft. The carbonization of coal (Newcastle blend coal) under a rising temperature condition was interrupted at a certain temperature, TC,max=823, 1073 and 1273K, to obtain semi-coal-char including some residual V.M. The semi-coal-char was mixed with reagent grade hematite in the mass ratio of one to four, together with Bentonite of 1 mass% as a binder. Carbon composite pellets using the semi-coal-char were prepared by hand rolling. From the TG-DTA analysis, the weight of carbon composite pellet at TC,max=823K decreased largely from 823K because of release of residual V.M. Isothermal reductions of thus obtained pellets were done in N2 gas atmosphere. Fractional reductions of the carbon composite pellets using the semi-coal-char at TC,max=823K were higher than any other pellets (TC,max=1073 and 1273K) by about 10% at reduction temperatures: TR=1073 and 1173K. Furthermore, it was confirmed by the XRD analysis after reduction of pellets that the carbon composite pellets at TC,max=823K have the highest reducibility; the original Fe2O3 was mainly reduced to Fe3O4 and FeO at TR=1073K for 60 min, to FeO and Fe at TR=1173K for 90 min and to Fe at TR=1273K for 60 min.
  • Scientific Research for Iron and Slag Samples from Simulated Tatara Iron Making Using of Specularite Ore Raw Material

    pp. 473-482

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    DOI:10.2355/tetsutohagane.95.473

    The iron making experiments were carried out by the society for study of Nichinan-tatara. In these experiments for a smelting, a simulated Tatara iron making furnace and a raw material of specularite ore produced from Mt. Sentsu-zan in Tattori were used. Iron lunp after the smelting process was refined by a smith process. Iron lump and slag from the smelting process and the refining process, specularite ore and clay as a furnace material were observed by a microscope and an electron probe micro analyzer (EPMA). Concentration of carbon and sulfur in iron lump, specularite ore and clay were determined by a carbon and sulfur analyzer with a combustion infrared absorption method. Concentration of many trace elements in iron lump, slag, specularite ore and clay were determined by a neutron activation analysis (NAA).
    Concentration sulfur in iron lump from the 1st iron smelting experiment was high of about 0.86%. Specularite ore used in the 1st iron smelting experiment was low grade quality and pyrite ore with high concentration of sulfur was included in specularite ore. The existence of non metallic inclusions were observed in iron lump after iron making and iron lump after smithing by optical microscope. The existence of sulfur was confirmed to these non metallic inclusions by the EPMA analysis. It was clarified that the sulfide existed in iron lump from these results. It turned out that these sulfide originated in pyrite by XRD.
  • Alloy Layer Structure Formed by High-temperature Aluminizing in Metal Mold Steel SKD61

    pp. 483-488

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    DOI:10.2355/tetsutohagane.95.483

    The alloy layer formed by high-temperature diffusion treatments in the air after adhering of aluminum foil thickness from 5 to 50 μm on metal mold steel SKD61 are examined. As a result, structural defect was not observed between FeAl and αFe in the alloy of high temperature aluminizing, and the most stable alloying layer was formed at the case of the initial aluminum thickness was 15 μm. The case of initial aluminum was thinner than 5 μm at the long time diffusion and that was thicker, and than 5 μm at the short time diffusion, structural defects were observed in the alloy layer. The former structural defect contained Cr oxide and aluminum oxide outside, and the latter structural defect contained void and high concentration of Cr. The stable alloy layer of high-temperature aluminized metal mold steel will be consist by Cr saluted FeAl and αFe which has toughness without structural defects.
  • Probabilistic and Statistical Evaluation of Delayed Fracture Characteristics Obtained by CSRT Method

    pp. 489-497

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    DOI:10.2355/tetsutohagane.95.489

    The delayed fracture characteristics of steels are expressed by the relationship between the maximum fracture stress and the hydrogen content at the notch tip of circumferentially notched round bar specimen, where delayed fracture initiates. This material constant is easily obtained by CSRT (Conventional Strain Rate Technique) method. The CSRT tests with the notch tip radius of 0.1, 0.25 or 0.8 mm were carried out on the high strength steel having 1300 MPa in tensile strength. Based on the probabilistic and statistical evaluation of the CSRT test results, the specimen with the notch root radius of 0.25 mm gives stable and average results of all experiments. Moreover, this notch geometry has the comparable stress concentration factor to the bottom of the actual bolt screw and easily machined with high accuracy. From these points of view the 0.25 mm radius notch is considered to become the standard specimen geometry. The scattering of delayed fracture characteristics was evaluated by applying the P–S–N method of fatigue test and the P–S–H method was demonstrated.
  • Three Dimensional Simulation of Polycrystalline Cleavage Crack Propagation in Steel

    pp. 498-505

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    DOI:10.2355/tetsutohagane.95.498

    This paper proposes a three dimensional model to explain microscopic behavior of cleavage crack propagation in steel. This model is based on a fracture mechanics model, which assumes a crack propagation along the cleavage plane with the highest tensile normal stress among three {100} planes in a grain. For calculating the normal stresses on the {100} planes, local stress intensity factors need to be calculated. The model considered three factors for estimating the local stress intensity factors, i.e., non-straight crack front, irregular crack surface and unfractured ligament between the grains and approximate calculations were carried out. The results are compared with observations of Charpy impact specimen fracture surfaces by conventional SEM as well as 3D SEM. The comparison showed good agreement between the calculations and the experiments. It was demonstrated by the present model that grain size and critical value of shear fracture had influence on cleavage crack propagation direction, discontinuous boundary and tear ridge formation.
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    Readers Who Read This Article Also Read

    1. Probabilistic and Statistical Evaluation of Delayed Fracture Characteristics Obtained by CSRT Method Tetsu-to-Hagané Vol.95(2009), No.6
  • Material Stock and Flow Analysis of Stainless Steel Based on Mass Balances of Cr and Ni

    pp. 506-514

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    DOI:10.2355/tetsutohagane.95.506

    This paper analyzed stainless steel stock and flow in Japan by using a dynamic modeling. Classifying different kind of alloys, stainless steel was subdivided into 13Cr, 18Cr, Ni–Cr, and Ni–Cr–Mo. Productions of heat-resistant steel, low-alloyed steels for machine structural use, cryogenic special steel, bearing steel, and spring steel were also taken into account as alloying steel including Cr and/or Ni in mass balances of Cr and Ni. In production processes, all raw materials for stainless steel were clarified by upholding mass balances of Cr, Ni and Fe. In-use stock of ferritics and austenitics at year 2005 were 4 Tg and 12 Tg, which could be converted to 3 Tg of Cr and 1 Tg of Ni. From the results of the model, collection rates as stainless steel scrap were estimated less than 35% for ferritics and more than 75% for austenitics. The collection rate of ferritics was estimated to be relatively small because some of ferritic scrap could be recovered as carbon steel scrap due to its magnetism. The dynamic model slso estimated that main source of ferritic scrap generation will be automobiles in the next decade. In order to promote recycling of ferritic scrap, recovery from automobiles would be important.
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    Readers Who Read This Article Also Read

    1. Origin of Steel Scrap Generated in Japan Tetsu-to-Hagané Vol.91(2005), No.1
    2. Analysis of Global Demand for Iron Source by Utility of Stock Hypothesis Tetsu-to-Hagané Vol.95(2009), No.6
    3. Probabilistic and Statistical Evaluation of Delayed Fracture Characteristics Obtained by CSRT Method Tetsu-to-Hagané Vol.95(2009), No.6
  • Basic Characteristics of a Swirl Motion of Bubbling Jet in a Cylindrical Vessel Accompanied by Particle Lifting

    pp. 515-521

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    DOI:10.2355/tetsutohagane.95.515

    A swirl motion of a bubbling jet in a cylindrical vessel is useful for bath mixing. This paper describes the mixing of small solid particles initially settled on the bottom of a water-filled cylindrical bath. The bubbling jet is generated by injecting air through a J-shaped lance placed on the bath centerline. Experiments are made on the patterns of swirl motion, the occurrence condition of the deep-water wave type swirl motion accompanied by lifted-up particles, the amplitude and the period of the swirl motion. The measured values are compared with empirical and theoretical equations proposed previously for the bottom blown bath.
  • Analysis of Global Demand for Iron Source by Utility of Stock Hypothesis

    pp. 522-530

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    DOI:10.2355/tetsutohagane.95.522

    To forecast iron source demand, the Intensity of Use hypothesis, which assumes that material consumption per capita is a function of GDP per capita, is the most dominant theory in existing studies. However, this hypothesis is not effective for a world one-region model of iron sources. Therefore, we focused our attention on utility, and we suppose that economic growth is a major driver to increase the utility. As the utility of steel sustains for ages after purchase, we formulate the Utility of Stock hypothesis, which assumes that the in-use steel stock is a function of GDP. In this study, the world steel stock was computed and the Utility of Stock hypothesis was tested. Clear correlation is found between the steel stock and the GDP. It leads to the estimation that the world demand for iron ore depends not on the volume of GDP but on the variation of GDP. For the first time with total world figures, the result enables us to rationalize the recent decoupling between the world growth of iron source demand and the economic growth.
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    Readers Who Read This Article Also Read

    1. Origin of Steel Scrap Generated in Japan Tetsu-to-Hagané Vol.91(2005), No.1
    2. Material Stock and Flow Analysis of Stainless Steel Based on Mass Balances of Cr and Ni Tetsu-to-Hagané Vol.95(2009), No.6
    3. Probabilistic and Statistical Evaluation of Delayed Fracture Characteristics Obtained by CSRT Method Tetsu-to-Hagané Vol.95(2009), No.6

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