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

Tetsu-to-Hagané Vol. 79 (1993), No. 8

  • Isolation and Determination of Precipitates in High Alloys and Super Alloys (II)

    pp. 897-907

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  • Mechanisms and Mechanics of Fatigue Fracture of Steels

    pp. 908-919

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  • Effect of the Addition of SiO2 and SiO2-CaO on the Reduction of Dense Wustite at High Temperatures

    pp. 920-926

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    The dense wustite plates containing SiO2 or SiO2-CaO have been reduced isothermally in a stream of hydrogen at temperatures between 1000 and 1345°C. The specimens used in this work consist of FeO phase with a dissolved part of added oxides, Fe-Ca olivine and dicalcium-silicate. At temperatures below 1100°C, reduction of FeO is accelerated by the presense of SiO2 and/or CaO dissolved in a small amount, and affected slightly by Fe-Ca olivine and dicalciumsilicate.
    At temperatures above 1200°C, reduction of FeO is not accelerated by the additives, but retarded by the formation of the layer of dense iron on wustite or by low reducibility of the oxide which are formed with reduction of the molten oxide which is formed from the complex oxides and a part of FeO phase.
    x

    Readers Who Read This Article Also Read

    1. CO2 Recycling for a Carbon Resource Tetsu-to-Hagané Vol.78(1992), No.8
    2. Reaction Rate of Methane Formation for the Catalyst of Reduced Iron Pellets Tetsu-to-Hagané Vol.78(1992), No.11
    3. Outlook of Kinetic Studies on the Combustion of Pulverized Coal in a Blast Furnace Tetsu-to-Hagané Vol.78(1992), No.8
  • Behavior of Burden during the Pulverized Coal Injection into Blast Furnace through Tuyers

    pp. 927-933

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    It is known that the pulverized coal injection operation leads to increase in the ore/coke ratio in a blast furnace and some of the injected pulverized coals are accumulated in the blast furnace, being not burnt. Because these situations could make the blast furnace operation unstable, the control of gas flow in the blast furnace, which corresponds to the pulverized coal injection operation, becomes necessary.
    In this paper, a systematic experiments were made to clarify the effect of ore/coke ratio on chemical reactions in a cohesive layer which dominates the gas flow in a blast furnace. The effects of ore/coke ratio and unburnt pulverized coal on the mechanical strength of coke slits in a blast furnace were also investigated by using CO2 gas with volatile matter removed char prepared from a coal.
    It was found that:
    (a) Reduction of ore in a cohesive layer is affected by the gas flow resistance through the cohesive layer due to the increase in thickness of ore layer.
    (b) Unburnt pulverized coal is gasified more rapidly than lump coke and, hence, the degradation of coke is decreased.
    x

    Readers Who Read This Article Also Read

    1. CO2 Recycling for a Carbon Resource Tetsu-to-Hagané Vol.78(1992), No.8
    2. Reaction Rate of Methane Formation for the Catalyst of Reduced Iron Pellets Tetsu-to-Hagané Vol.78(1992), No.11
    3. Outlook of Kinetic Studies on the Combustion of Pulverized Coal in a Blast Furnace Tetsu-to-Hagané Vol.78(1992), No.8
  • Effects of the Swirl Motion of Bubbling Jet on the Transport Phenomena in a Bottom Blown Bath

    pp. 934-940

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    A bubbling jet in a cylindrical bath subject to centric bottom gas injection rotated around the vessel axis under a certain blowing condition. There exist two kinds of swirl motions: one is closely related to the so-called sloshing and the other is induced by hydrodynamic instability of a large scale ring vortex enclosing the bubbling jet.
    Conditions describing the occurrence and cessation of the swirl motions have been studied by many researchers. However, the bubble characteristics, liquid flow characteristics, mass transfer from a solid body immersed in the bath, and mixing time of the bath have not been clarified under swirl motions. This study was made to investigate the effects of the swirl motions on the above mentioned transport phenomena using a high-speed video camera, an electroresistivity probe, a laser Doppler velocimeter, an electrochemical sensor, and an electric conductivity probe. In order to stop the swirl motion, a cylindrical pipe was brought into contact with the bath surface. The swirl motion was found to enhance the mass transfer coefficient and reduce the mixing time significantly. This fact allows us to develop new metallurgical processes using swirl motion. It should be kept in mind, however, that the errosion of vessel wall also is enhanced by swirl motion.
  • Improvement of Mn Yield in Less Slag Blowing at BOF by Use of Sintered Manganese Ore

    pp. 941-947

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    In order to improve manganese recovery by smelting reduction of manganese ore during less slag blowing at BOF, the effects of sintered manganese ore on reduction behavior have been studied both in 100kg laboratory scale and in 340t industrial scale tests. Results obtained in this work are summarized as follows. 1) The oxidation of [Mn] during addition of manganese ore is suppressed by using sintered manganese ore, because the active oxygen in manganese ore can be decreased to one third by sintering. 2) Addition of CaO to sinter is very effective for increasing the reduction rate of (MnO). Especially, it is most effective when CaO/SiO2 of sinter is more than 3. 3) Using the sinter with CaO/SiO2 of 3.05, manganese recovery in industrial converter can be increased to 70-80%, when the amount of sinter is 12-13kg/t and also end-point [C] is 0.10-0.18%. (65% for raw manganese ore) 4) These effects of high basicity sinter are due to both early slagging and decreasing (%MnO)/[%Mn].
  • X-ray Fluorescence Analysis on mg Order of Oxide Super Conductors by Glass Bead Technique and Matrix Correction Using Theoretical Alpha Coefficients

    pp. 948-954

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    The X-ray fluorescence analysis using the glass bead technique was applied for the determination of major components (La, Sr, Cu, Ba, Ni, Y, Zn, Bi, Pb, Ca, Tl, Nd and Ce) in small samples of various oxide superconductors. A Pt-5%Au crucible newly designed for small amounts of samples was employed for melting and casting vessel. Ten milligrams of sample was fused with 500mg of sodium tetraborate containing 20 mass % of lithium carbonate for the analysis of La and Y system superconductors. Five hundred mg sodium tetraborate containing 15 mass % of lithium hydroxide and 500mg of lithium tetraborate containing 10 mass % of lithium carbonate were used for Bi and Nd system one, respectively. For the analysis of Tl system one, in which Tl2O3 has a low boiling point and toxicity, 1500mg of sodium disulfate containing 12 mass % of sodium tetraborate was superior in fusing at a low temperature (ca. 400°C). The synthetic calibration standards were prepared with each oxide prefused with a fusing mixture, which contained 10 mass % of an analyte. The effect of coexisting elements were corrected with the theoretical alpha coefficients correction method. The relative standard deviations (RSDs) of repetitive seven measurements for the determined values of each analyte were less than 1%. The analytical values of various samples were in good agreement with those obtained by chemical analysis.
  • Effects of Manganese and Chromium on the Oxygen Potential in Liquid Zinc Bath

    pp. 955-960

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    Control of the free aluminum concentration in a hot dip galvanizing bath is of great importance for producing galvannealed steel sheets. Since aluminum has much greater affinity for oxygen than zinc, the oxygen potential of Zn-Al-O bath may be determined only by the following equilibrium reaction;
    Al2O3(s)=2Al(in Zn)+3O (in Zn) when the aluminum concentration in the bath is relatively small. Aluminum sensor based on the emf method using the zirconia solid electrolyte has been devised by utilizing the above equilibrium relation.
    In this paper, pure manganese or chromium has been employed as a deoxidizer for molten zinc and the effect of these additives on the oxygen potential in molten zinc has been investigated by emf measurements using the cells below.
    (-) W|O in (Zn-Me) |ZrO2(+8mol%Y2O3) In, In2O3|W(+) Me; Mn or Cr
    The above cells responded quickly and showed stable emfs with fairly good reproducibility. From the analysis of such emf values at temperatures between 450650°C, the following relationships between additive concentration and cell emf for two cells at 450°C were obtained;
    E/mV=34.5 ln[Mn]/mass%+380.1, 0.03≤[Mn]/mass%≤0.99
    E/mV=11.0 ln[Cr]/mass%+408.7, 0.0007≤[Cr]/mass%≤0.276
    Also, the analysis of above results suggests that the emf method using zirconia solid electrolyte is applicable down to Po2/Pa=10-40 at 450°C. It has been confirmed by calculating the value of P_??_ that the portion of electronic conduction in the above zirconia solid electrolyte was negligibly small.
  • Effect of Cr Contents in Steel on Corrosion Behavior of the Metal Plated Sheets in Can

    pp. 961-967

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    In order to develop the metal plated steel sheet with excellent corrosion resistance for drinking can, we studied corrosion behavior of Sn electroplated sheet and TFS sheet under corrosive environment in the can and effect of chromium added steel as base metal on corrosion resistance.
    As a result, it was proved that corrosion resistance of these electroplated steel sheet is increased with increase of chromium amount contained in the steel. Furthermore, as a result of analysis of oxide film property on steel surface, it was presumed that coating property of Cr2O3 base coating film is superior with greater than 7 wt% of chromium amount and is apt to form stable passivation film in aqueous solution of phosphoric acid and citric acid, becoming one of factors for improvement of corrosion resistance.
  • Effect of Strain on Ferrite Transformation from Super-cooled Austenite in Fe-0.5%C Alloy

    pp. 968-972

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    Fe-0.51wt%C alloy was cooled from 1000°C at 0.3°C/s and rolled at 710°C, at which austenite was super-cooled by 55°C. The isothermal transformation behavior at 710°C from the super-cooled and strained austenite to ferrite was investigated. It has been found that the nucleation rate of the ferrite particles increases with strain and that the rate constant for the growth of the ferrite particles remains constant regardless of the strain. The time required for the transformation and the average size of the ferrite particles decrease with increasing strain.
  • Effects of Cu, Ni, Cr and Sn on Mechanical Properties of Ti Added Extra Low C Steel Sheet

    pp. 973-979

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    The effects of Cu, Ni, Cr and Sn addition on the mechanical properties of Ti-added extra low carbon continuously annealed steel sheet were studied. Following results were obtained:
    (1)Cu or Cr addition up to around 0.2% raised tensile strength, and decreased total elongation and r value.
    (2)When slab reheating temperature was lowered to 1050°C, tensile strength was decreased and total elongation and r value were increased at the same 0.2% Cu or 0.2% Cr content.
    (3)Ni addition up to 0.12% did not give a significant effect on tensile properties or r value.
    (4)Sn addition up to 0.085% increased tensile strength, and decreased total elongation and r value. In the case of Sn, lowering slab reheating temperature did not improve total elongation and r value.
    (5)The effects of Cu, Ni, Cr and Sn content on mechanical properties are proportional to the difference in atomic radius between iron and those impurities.
    (6)The effect of impurity content on r value is different between the group of Cu, Ni and Cr, and Sn. In the case of Cu, Ni and Cr whose atomic radius are slightly bigger than that of iron, r value can be improved with lowering slab reheating temperature. However, in the case of Sn whose atomic radius is significantly bigger than that of iron, the effect of slab reheating temperature is very small.
  • Effects of Cr, Mo, W, Mn and Ni on Toughness of 2.25Cr-Mo-V Rotor Steel

    pp. 980-987

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    The effect of Cr, Mo, W, Mn and Ni contents on the toughness of a 2.25Cr-Mo-V based bainitic steel was investigated and microstructural factors which affect the toughness of this steel were discussed. Fracture appearance transition temperature (FATT) is decreased remarkably with the increase of Cr, Mo and/or Ni contents whereas the FATT is increased with the addition of Mo in excess of 1.5% or with the addition of W. Mn exerts no significant effect on the FATT.
    Cr addition refines the bainitic microstructure by lowering the bainite start temperature (Bs) and improves the toughness. Ni addition also contributes to the improvement of toughness by increasing stacking fault energy which makes cross slip easier. The decrease in toughness with the addition of Mo over 1.5% may be attributed to the high precipitation density of coarse particles of M6C in the matrix. In addition, it is demonstrated that the toughness of the 2.25Cr-Mo-V steels is superior to that of the conventional 1Cr-Mo-V steel.
  • Effects of Cr, Mo, W, Mn and Ni on Creep Properties of 2.25Cr-Mo-V Rotor Steel

    pp. 988-995

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    The effect of Cr, Mo, W, Mn and Ni contents on the creep properties of a 2.25Cr-Mo-V based bainitic steel was investigated and microstructural factors which affect the creep rupture strength were discussed. The creep rupture strength is decreased by increasing Cr, Mn and Ni contents although it is slightly increased with the addition of W. The effect of Mo is very small. Addition of Ni in excess of 1.8% decreases the creep rupture strength remarkably.
    Preferable precipitation of Cr23C6 and Cr7C3 due to the increase of Cr content suppresses the precipitation of V4C3, and decreases the creep rupture strength. Ni and/or Mn addition decreases the creep rupture strength because the stacking fault energy which makes cross slip easier is increased. No further improvement of creep rupture strength due to solid solution strengthening is expected by the addition of Mo in excess of 0.8%. W contributes to the increase in creep rupture strength through solid solution strengthening effect. In addition, it is concluded that the creep rupture strength of the 2.25Cr-Mo-V steels equals or exceeds that of the conventional 1Cr-Mo-V steels.
  • Effect of Reversion Treatment on Strength and Ductility of Low C, Cr-Ni Martensitic Stainless Steel with High Resistance to Weld Softening

    pp. 996-1002

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    In order to develop high strength stainless steels with good ductility and high resistance to weld softening, reversion behavior of martensite to austenite of low C, Si-13%Cr-7%Ni martensitic stainless steels have been studied. Moreover, dependences of mechanical properties of reversion treated steels on austenite stability, cold rolled reduction and Si have been investigated.
    Main results obtained are as follows;
    When cold rolled steels, Mf temperatures of which are around room temperature, are heat-treated at the region between As and Af temperatures, some portions of martensite are reversed to austenite, which results in microduplex structure of ultra-fine austenite grains and tempered martensite. These steels have excelent balance of high strength and good ductility. The steel containing high Si possesses good ductility as well as high strength. Softening of welded metal dose not occur because it undergoes martensitic transformation on cooling after welding.
  • Strengthening Mechanism of Sintered and Heat-treated Compacts Made from Partially Prealloyed Steel Powders

    pp. 1003-1010

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    Extensive study has been executed for an optimization of chemistry of partially prealloyed steel powders with Ni and Mo for the production of high strength and high toughness sintered components via double-pressing, double-sintering and heat treatment.
    The austenite precipitates at Ni-rich phases in the sintered and heat-treated compacts made from partially prealloyed steel powders with 0.6% graphite. The detailed analysis of stress-strain curve of sintered and heat-treated compact indicates that deformation is localized at untransformed austenite and strain induced martensite with very high strength is formed at the initial stage. The tensile strength increases with the amount of strain induced martensite. Condensed carbon areas are observed in the specimen with higher amount of austenite. The tensile strength depends also on the carbon concentration in martensite.
    The maximum tensile strength increases with the decrease of Ni content. This is attributed to the decrease of sintered density and the increase of untransformed austenite for plastic deformation. The sintered and heat-treated compacts made from the 2%Ni-1%Mo steel powder contain a sufficient amount of austenite which transform almost completely to martensite during loading. Therefore, this compact shows an ultra high strength of 1920MPa and a high unnotched Charpy absorbed energy of 53J.
  • 誌上討論

    pp. 1011-1012

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  • New Materials for High Speed Railway Vehicle

    pp. N568-N575

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  • High-Temperature Plastic Flow in Fine-Grained Ceramics

    pp. N576-N582

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