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

Tetsu-to-Hagané Vol. 79 (1993), No. 4

  • The Mechanism of Reduction of Iron Oxides

    pp. 431-442

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    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
  • In-flight Reduction of Fine Ores in a Hot Reducing Gas Flow

    pp. 443-448

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    Direct injection of fine ores into a blast furnace has become a key technology to the development of an advanced blast furnace process for the 21st century. In order to take full advantage of this technology such as high flexibility under the coming resource circumstances, it is necessary to promote the "in-flight" reduction of fine ores in the raceway to the highest degree so as to minimize the endo-thermic reaction at the deadman due to the wustite residue.
    As a base of pursuing a rapid reduction process, the study put its emphasis on revealing the microscopic reduction behavior. of fine ores. Observation showed that some of are particles which were obviously liquefied and completely spheroidizied during the experiment contained metallic irons inside the wustite shell. This particular morphology was explained by "Marangoni Effect". It was also mentioned that the "micro-flow"on the molten wustite surface had significant influence over the smelting reduction of fine ores by reducing gases.
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    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
  • Production Test of High-carbon Ferromanganese Using a Shaft Type Furnace with Coke Packed Bed Injected with Highly Oxygen Enriched Air and a Large Quantity of Pulverized Coal

    pp. 449-455

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    High-carbon ferromanganese has been produced by electric arc furnace in Japan. But its production cost has increased because of a speedy rising of electricity cost and Japanese ferromanganese has lost competitiveness in the international market. So, for the purpose of decreasing its production cost, high-carbon ferromanganese production tests (production rate = 1. 9-4. 3t/d) were performed using a melting test furnace with coke packed bed injected with highly oxygen enriched air and a large quantity of pulverized coal. Moreover the operation indices of a commercial plant of 170t/d in production capacity were estimated by heat and mass balance model, and following results were obtained.
    1) In this test, high-carbon ferromanganese of [Mn] = 75% was produced stably using the coke blended with 56% non-coking coal, with coal rate of 1502kg/t, coke rate of 1087kg/t and productivity of 3.11t/(d·m3).
    2) The total coal consumption of the commercial plant of this method is estimated to be less than that of the blast furnace in spite of higher fuel rate because a large quantity of pulverized coal is used in this process. Through these investigations, this process seems to have a prospect of being available as a ferromanganese production process instead of electric furnace method.
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    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
  • Production Test of High-carbon Ferrochrome Using a Shaft Type Furnace with Coke Packed Bed Injected with Highly Oxygen Enriched Air and a Large Quantity of Pulverized Coal

    pp. 456-463

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    High-carbon ferrochrome has been produced by electric arc furnace in Japan. But its production cost has increased because of a speedy rising of electricity cost and Japanese ferrochrome has lost competitiveness in the international market. So, for the purpose of decreasing its production cost, high-carbon ferrochrome production tests (production rate = 50-110kg/ h) were performed using a melting test furnace with coke packed bed injected with highly oxygen enriched air and a large quantity of pulverized coal. Moreover the operation indices of a commercial plant of 35t/d in production capacity were estimated, and following results were obtained.
    1) It was confirmed that the reduction and melt down rate of chromium are sinter were superior to that of chromium ore pellet, and the favorable characteristics of chromium ore sinter were obtained as follows: CaO/SiO2 = 1.0-1.3, slag weight = 1100-1300kg/t-(Cr + Fe).
    2) It was confirmed that the fuel rate and productivity could be improved under the stable operation by using the chromium ore sinter.
    3)The fuel rate of the commercial plant of this process using chromium are sinter was estimated to be 1967kg/t in the case of [Cr] =52.2% with less net energy consumption than that of EAF.
  • Bath Vibration in Bottom Blowing Trough Type Reactor

    pp. 464-471

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    In the case to introduce the bottom blowing method under the trough type continuous steelmaking furnace, wave motion of steel bath should be suppressed. To solve this problem, water model equipment has been used to examine the wave motion in the range of shallow water waves. Basic results obtained are as follows.
    (1) Frequency of the induced wave is mainly affected by the bath depth, and along with the increase of the bath length this frequency is kept in a certain range by increasing the node number of the wave.
    (2) In the transition range of the node number, wave motion can be weakened.
    (3) To suppress the wave motion it is very effective to locate each bottom blowing nozzle at the distance from transition range to the wall obtained in one nozzle test and put the nearest nozzle from the wall at the half distance of transition range.
    (4) The node number and transition range can be represented on the non-dimensional diagram of the bath depth to the ratio between distances from nozzle position to both side walls.
  • Dissolution and Reduction Behavior of Manganese Ore in Less Slag Blowing at BOF

    pp. 472-478

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    In order to improve the yield of Mn in less slag blowing at BOF, the dissolution and reduction behavior of manganese ore have been studied in 100kg scale test. The results obtained in this work are as follows.
    1) Dissolution of manganese ore into BOF slag is quite easy at 1600°C, but it is not so easy at 1400°C because of the precipitation of solid MnO-FeO. So, it is hard to dissolve manganese ore in the first harf of blowing at low temperature.
    2) If the amount of manganese ore addition is small, manganese ore has remarkable effect on slagging of BOF slag. But, if its amount is more than that of BOF slag, the melting point of BOF slag becomes higher than 1450°C.
    3) Reduction rate of manganese ore mainly depends on bath temperature, and higher temperature is desirable. On the other hand, the reduction rate is not affected by carbon content of steel in the range of [C]≥1%.
    4) From these results, in order to improve the yield of Mn, early slagging and keeping bath temperature as high as possible are very important.
  • Controlling of Centerline Segregation of Continuously Cast Bloom by Continuous Forging Process

    pp. 479-485

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    A continuous forging process has been put into operation to prevent the formation of centerline segregation in continuously cast bloom. In the process, the solidifying bloom is continuously forged down by a pair of anvils installed in the strand so that the solidifying shells are pressed into contact each other. In consequence of the application of the forging process on the casting, internal properties such as macro-and semimacro-segregation of the bloom are markedly improved. Segregation ratio of carbon at central part in the bloom can be controlled at the aimed value between 0.6 and 1.0 depending on the central solid fraction in the bloom at forging.
    A mathematical model which explains the discharge of solute enriched liquid from the solid-liquid coexisting region to the upper liquid region was developed. The calculated result shows that discharge ratio of liquid out of the solid-liquid coexisting region increases as solid fraction decreases. The discharge ratio is approximately equal to that of the fractional solidification refining reported by Flemings et al. The macro-segregations calculated from the model are in good agreement with observed ones for carbon, manganese, phosphorus and sulphur.
  • Electromagnetic Atomization of Solid Metals Using Arc Discharge and Static Magnetic Field

    pp. 486-491

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    An electromagnetic atomization process for solid metals is newly proposed. The electromagnetic force induced by a direct electric current and a static magnetic field is utilized to splash metals melted by arc discharge.
    Tungsten was used as an unconsumable cathode to atomize titanium as the anode. It was found that the imposed magnetic flux density and the current had lower limits in atomizing the solid metal in a stable condition. It was also found from observations by a high speed video set that particles were splashed not continuously but intermittently. The effects of current and imposed magnetic flux density on particle size distribution were studied. The mean particle diameter decreased with increasing the imposed magnetic flux density (B) in proportion to B-0.46, but on the other hand scarcely depended on the imposed current.
  • Simple, Rapid, and Precise Determination of Manganese in Iron and Steel by Flow-injection Analysis

    pp. 492-496

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    In order to improve the simplicity, rapidity, accuracy and precision in the chemical analysis of iron and steel, a flow-injection analysis (FIA) has been studied for manganese determination with photometric detection. The FIA system consists of a direct on-line coupling of coloring reaction and absorbance measurement in a continuous flow mode ; manganese is oxidised by ammonium peroxodisulfate to MnO4- and the absorbances of the resultant solution are measured before and after the addition of sodium nitrite. The FIA manifold and the optimum reaction conditions were established for allowing this simultaneous measurements of analytical and blank signals by single sample injection with single detector. The analytical results by the proposed method for four Japanese standards of steel (The Iron and Steel Institute of Japan) agreed well with the certified values for manganese and showed high precision of relative standard deviations of 0.25-0.50% which are much smaller than those usually observed in manually operated spectrophotometric methods. An injection rate of 12 sample solutions/h can be achieved. The most appealing feature of the proposed method is that the analysis is achieved in a continuous and nearly closed system without complicated manual operations, which can afford simpler and rapid as well as accurate and precise determination of manganese.
  • Evaluation of Parameters Affecting Mist Cooling Heat Transfer in High-temperature Region

    pp. 497-503

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    To predict mist cooling heat transfer, it is necessary to understand systematically this phenomena. However, since there are many parameters affecting mist cooling heat transfer and the effects of these parameters are very complicated, it is still a difficult task to predict mist cooling heat transfer for actual systems.
    In the present paper, the effect of surface diameter on mist cooling heat transfer was experimentally investigated. To do this, the diameter of test plates was varied from 10 to 30mm. Mist cooling experiments were conducted for horizontal upward-facing surfaces made of silver. The experimental results obtained in this study show that the diameter of the plate affects the heat transfer coefficient of mist cooling in the high-temperature region corresponding to the film boiling region on the boiling curve.
    Next, the correlating equations for the heat transfer characteristics of mist cooling in the high-temperature region are developed accounting for the effects of volumetric droplet flow rate and surface parameters including the effect of the surface diameter. These correlating equations are in good agreement with a number of experimental data.
  • Development of Simple Strain Distribution Measurement System by Interferometry Using CCD Image Elements

    pp. 504-509

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    A simple measurement system for strain distribution has been developed on the basis of moire interferometry using CCD camera. A direct image of moire fringe can be obtained from the grid on surface of a plate specimen. After simply preprocessing the image, the system allows us to get the strain distribution in a few seconds. This paper describes the application of the system to large plate specimens by creep testing. The interference fringe generated by a CCD image agrees with the conventional moire fringe. Thus we can apply the system to measure the strain distribution of interrupted creep specimens. Since the system uses the simple configuration of a CCD camera and a personal computer for gridded specimens, little skill is needed to apply it. When the surface conditions are not smooth enough, a simplified smoothing treatment helps us to improve the accuracy of strain measurement. The range of measurement can be localized by the zooming function of the camera. Another feature of the new method is that it can be used in nearly real-time situation.
  • Effect of Impurities, Si and Mn Contents on Long Term Isothermal Temper Embrittlement of 3.5%NiCrMoV Steel Forgings for Turbine Rotors

    pp. 510-516

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    Isothermal aging tests at 375, 400 and 450°C for 1000020000 hs were performed on 3.5NiCrMoV steel forgings for low pressure turbine rotors with various amount of impruities, Si and Mn, in the Mn range of less than about 0.30 mass %. The results are summarized as follows.
    1) The shift in 50% fracture appearance transition temperature by isothermal temper embrittlement at T°C for t h (ΔFATTiT) decreases with decrease in amount of impurities, defined as X = (10P + 5Sb + 4Sn +As) × 102, Si, Mn, cooling rate during quenching and aging temperature. When X is less than 2.1, no temper embrittlement occurs, regardless of Si and Mn contents, but when X is greater than 4.1, embrittlement occurs according to Si and Mn contents. However, with X = 10.7, some embrittlement is observed even at 0.02% Si and 0.04% Mn in the aging tests at 450°C for 10000 hs. Therefore, reduction of amount of impurities is important to reduce susceptibility to temper embrittlement.
    2) When X is 4.1 to 7.0, the equation, which can accurately estimate ΔFATTiT from K = (Si + Mn)·X, X and the cooling rate, is derived.
    3) When K is less than 0.78 (X ≤6.0, Si≤ 0.05% and Mn ≤ 0.08%), maximum isothermal temper embrittlements at 375450°C for 20 years are calculated to be 24°C at surface and 16°C at center of a 1800 mm diameter rotor forging, and the fairly good toughness is estimated to be obtained even after using for a long term.
  • Effects of Alloying Elements, Microstructure and Applied Stress on Amount of Saturated Temper Embrittlement and Embrittling Rate in Low Alloy Steels

    pp. 517-523

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    Effects of alloying elements, microstructure and applied stress on temper embrittlement were studied at standpoints of the saturated amount and the rate of embrittlement in low pressure turbine rotor steels. The saturated amount of temper embrittlement was increased by Si or Mn content. It was affected by microstructure, but was not affected by hardness after tempering and applied stress. The saturated amount of temper embrittlement was the largest in a sample with martensite. The next was in a sample with bainite and the smallest in a sample with pearlite. The rate of temper embrittlement was enhanced by an increase in Mn content or hardness or by tensile stress. It was prevented by hydrostatic compression. Si and microstructure did not influence the rate of temper embrittlement. The amount of temper embrittlement increased with the amount of phosphorus segregated to grain boundary in samples with a certain microstructure. The amount of embrittlement was larger in samples with high hardness than in samples with low hardness at a certain amount of phosphorus segregated.
  • Strengthening of Austenitic Stainless Steels by Thermo-mechanical Control Process

    pp. 524-530

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    Strength of austenitic stainless steels produced by the thermo-mechanical control process were quantitatively estimated on the basis of various strengthening mechanisms. Optimum strength control method in an industrial scale and the change in corrosion resistance with strengthening were also investigated. The grain size dependency of 0.2% proof strength in austenitic stainless steels is 2/3 of that in plain carbon steels, so that the strengthening by grain refinement was limited to 100MPa or less. Further strengthening was performed by substructure strengthening through the rolling in the unrecrystallization region. The total reduction in this temperature region is the controlling factor for the strength and therefore important to attain an aimed strength level in an industrial scale. A critical cooling rate, above which the corrosion resistance of TMCP plates is comparable to that of ST plates, are 10°C/s for 0.066C, 1°C/s for 0.032C and less than 0.2°C/s for 0.021C.
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    1. Analysis of Microstructure Evolution during Steckel Mill Rolling of AISI304 Stainless Steel ISIJ International Vol.48(2008), No.2
  • Effects of Al-content and Isothermal Hot-working Temperature on Microstructures of Thermomechanically Processed (α2 + γ)-type TiAl Alloys

    pp. 531-536

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    Microstructures of thermomechanically processed Ti-40 50at%Al alloys have been studied with respect to the effect of Al-content and isothermal hot-working temperature. Thermomechanical processing of the alloys have been found to result in five different types of microstructures depending on Al-content and hot-working temperature. The regions corresponding to the five different microstructure types have been depicted in the Ti-Al binary system. Characteristics of each type of microstructure and factor determining the boundaries between the regions have been discussed on the basis of the results of optical and transmission electron microscopic observations.
  • What is C60?

    pp. N257-N262

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  • Theory and Application of Therlmo-Magneto Hydro Dynamics (II)

    pp. N263-N281

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  • Heat Resisiting Steels, Superalloys, and Ultra-high Temperature Materials

    pp. N282-N289

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