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

Tetsu-to-Hagané Vol. 75 (1989), No. 3

  • A Critical Review of Solid State Sensors Used for in-situ Determinations of Dissolved Elements in Molten Iron and Steel

    pp. 379-388

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  • Superplasticity of Ceramics

    pp. 389-395

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  • Trace Analysis of Hydrogen in Aluminum and Its Alloys

    pp. 396-405

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  • Analysis of Aluminum and Its Alloys

    pp. 406-415

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  • Reduction Equilibria at the Final Stage of Reduction of Quaternary Calcium Ferrite with CO-CO2 Gas Mixtures

    pp. 416-423

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    Quaternary calcium ferrite was synthesized from chemical reagents of Fe2O3, CaCO3, SiO2, and Al2O3 and the reduction equilibria at the final stage of reduction with CO-CO2 gas mixtures were studied. The results obtained are summarized as follows :
    1) Dicalcium ferrite, which is produced during the reduction of binary calcium ferrite, is not found in the reduction of quaternary calcium ferrite. The reduction stage from dicalcium ferrite to iron and CaO is therefore not existent in the reduction of quaternary calcium ferrite.
    2) The reaction at the final stage of carbon monoxide reduction of quaternary calcium ferrite is given by the following equation.
    'FeO' (s)+ CO(g) = Fe(s)+ CO2 (g)
    where 'FeO' is the wustite which contains CaO, SiO2 and Al2O3 as solid solutions. The temperature dependence of the apparent equilibrium constant K(= PCO2/PCO) of the reaction which is the final stage of reduction of quaternary calcium ferrite synthesized in this study is given by the following equation.
    K = exp (-2.785 + 2 042/T) ± 0.003 (1 0731 326 K)
    x

    Readers Who Read This Article Also Read

    1. Reduction Equilibria of Ternary Calcium Ferrite with CO-CO2 Gas Mixture Tetsu-to-Hagané Vol.80(1994), No.6
  • Flow Characteristics of Gas and Powders at Circulating Fluidized Bed Reactor

    pp. 424-431

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    In order to investigate the characteristic of the circulating fluidized bed reactor, a cold model experiment was made to evaluate the interaction force between gas and powders and a mathematical simulation model was developed to estimate the behaviors of powders and gas in the riser and the downcomer. As a result of these studies, it is predicted that the gas velocity must be set high at the riser to achieve a stable circulating flow of powders and to use raw material with larger distribution of particle size.
  • Equilibrium Distribution Coefficients of Solute Elements between Solid and Liquid Phases in Ni-base Multi-component Alloys

    pp. 432-438

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    The equilibrium distribution coefficients, kXo, between solid and liquid phases in Ni-base multi-component alloys have been determined by means of the experiment and also the thermodynamic calculation.
    The experimental results show that kXo's of Ni, Cr, Fe, and Co are almost unchanged for the compositions of alloys, but that kXo's of Nb and Ta decrease with increasing Fe and Co contents in both Ni-Cr-Fe-Mo and Ni-Cr-Co-Mo base multi-component alloys. The composition dependence of kXo was also obtained by the thermodynamic calculation in which the solute-interations were taken into account.
  • Densities and Surface Tensions of Melts in the System CaF2-CaO-SiO2

    pp. 439-445

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    Densities and surface tensions of CaF2-CaO-SiO2 melts were measured by the Archimedean method and the maximum bubble pressure method, respectively. From the measured densities, the molar volume was computed for the following binary systems; CaF2-CaO, CaF2-3CaO·SiO2, CaF2-2CaO·SiO2, and CaF2-3CaO2·SiO2. For the systems, the molar volume obeyed the simple additive law on volume and it suggests that calcium fluoride in the melts behaves as a diluent. On the other hand, the surface tension for the binary systems changed approximately in accordance with the Guggenheim's equation for the regular solution. From the results, the iso-density curves and the iso-surface tension curves were proposed for the CaF2-CaO-SiO2 ternary melts having the ratio, CaO/SiO2 > 1.5 at 1 550C°.
  • Microsegregation in Ni Base Alloy

    pp. 446-453

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    In Ni base alloys, the precipitates resulting from the segregation of alloy elements often harm the quality of the material. The experiments of solidification and solution treatment with Hastelloy were done. The formation and elimination of precipitates were investigated, and the following results were obtained.
    1) The equilibrium distribution ratio of Mo is 0.77 and Mo is easy to segregate.
    2) The precipitates are formed in the interdendritic region at final solidification stage and their size is determined by the cooling rate during solidification.
    3) The effect of cooling rates on the precipitate size can be explained by the solidification model referred to the segregation of Mo.
    4) The precipitates are fully eliminated by the solution treatment for 24 h at 1 250°C. The elimination of precipitates can be described by the model where the diffusion of Mo is a rate controlling step.
  • Dephosphorization of Crude Stainless Steel with BaO-based Flux

    pp. 454-461

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    Dephosphorization of crude stainless steel with BaO-based flux is investigated in a laboratory scale test and industrial AOD operation.
    By using BaO-BaCl2-Cr2O3 flux or BaCO3-BaCl2-C flux of about 100 kg/t, 60% dephosphorization is possible, if the crude stainless steel has a chromium content of 16 to 25% and a carbon content of 1 to 2%. In addition, a more than 90% desulphurization and removal of vanadium can also be achieved.
    To get satisfactory dephosphorization, Cr2O3 content in slag should be controlled in 3 to 6% with BaO content of 40 to 50%. Phosphate capacity of the slag ( CPO43-≡(PO43- ) /(PP21/2·PO25/4) ) is about 10227 at 1 450°C.
    It is considered that this dephosphorization of crude stainless steel having a carbon content of 2% and a chromium content of 18% at 1 450°C proceeds with slightly higher oxygen potential of slag than that of metal.
  • Effects of Calcination Conditions on the Reactivity of Burnt Lime whih Water and on the Desulphurization Reaction of Hot Metal

    pp. 462-469

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    Four kinds of limestones produced from different areas in Japan were calcined in a laboratory muffle furnace over the temperature range of 900-1 200°C and holding times from 0 to 120 min. The effects of calcination conditions on the reactivity with water and on the desulphurization reaction of hot metal were investigated.
    The lime calcined from the crystalline limestone was little affected by calcination conditions and indicated good reactivity with water even by calcination at 900°C. The lime calcined from the microcrystalline limestone was much affected by calcination conditions, and only the lime calcined at the temperature higher than 1 100°C indicated the same good reactivity with water as the lime calcined from the crystalline limestone. It means that the calcination condition depends on the structure of limestone in order to get good reactivity of lime with water.
    The burnt lime having a good 1 min value of reactivity with water indicated a good desulphurization efficiency for hot metal. The observed changes in reactivity of burnt lime with water and hot metal could be attributed to the structure of burnt lime, i. e. existence of cracks of μm order in width.
  • Effect of Gradient of Transverse Direct Magnetic Field on Suppression of Wave Motion

    pp. 470-477

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    Molten metal being electrically conducting fluid, direct magnetic field can suppress wave motions which induce instabilities and surface defects in the several processes such as twin roll, electromagnetic casting, or conventional continuous casting.
    Transverse magnetic field was imposed on mercury surface wave and damping behavior was measured by making use of laser beam. It was found that the suppression of wave motion did not depend on field intensity but the gradient of it. A dispersion relation of wave motion, ω21coth (ε1h0) ε2 coth (ε2 h0) } = 2ξ2 g, was derived from the theoretical analysis taking into account of the gradient of magnetic field, and was verified by the experimental results.
    The effect of gradient of transverse magnetic field on suppression of wave motion is discussed on the basis of the dispersion relation derived here.
  • Theoretical Study on Gas Flow and Heat and Mass Transfer in a Converter

    pp. 478-485

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    Theoretical study was made and its result was compared with hot model experiment in order to understand gas flow, and heat and mass transfer in the converter with a top blowing lance.
    The experiment was made in a 200 kg high frequency induction furnace equipped with a oxygen lance. Post combustion ratio, γ, measured by a mass spectrometer increases with increase in lance height and decrease in oxygen flow rate. Transfer efficiency, ηH, of reaction heat of CO and CO2 formation to metal bath decreases with increasing γ.
    Two dimensional equations of continuity, conservation for momentum, enthalpy and gas species were solved numerically under the condition that the reaction rate at a fire spot is controlled by diffusion in a gas phase. The ad hoc model was used for the calculation of effective viscosity. The values of γ and ηH computed under the constant heat and mass transfer coefficients agree with the measured ones except for the effect of oxygen gas flow rate on ηH.
    The computed profiles of physical quantities indicate as follows : The gradients of temperature and concentrations between the lance tip and the depressed surface of metal bath were steeper than those in the other region. The maximum temperature and CO2 concentration are in the recirculating flow zone located between the lance tip and the depressed surface.
    x

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    2. A Model Study on Jet Penetration and Slopping in the LD Converter Tetsu-to-Hagané Vol.58(1972), No.1
  • Behavior of the Outlet C Concentration from the Trough Type Continuous Steelmaking Furnace

    pp. 486-492

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    Continuous steelmaking furnace is represented by combination of a statistical model derived by linear time series analysis, with a non-linear model consisting of 2 mixed tanks where rate of decarburization is assumed to be proportional to the product of average carbon concentration and apparent oxygen concentration, which is defined as a ratio of total oxygen and residing liquid iron in respective tank.
    As a result of simulation by applying measured time series data to the combined model, the performamce of the furnace was confirmed to be expessed reasonably well so that forecasting and design of control system may be feasible with the model.
  • Control of Cupola Operation for Continuous Steelmaking Process Using Time Series Model

    pp. 493-500

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    CSM Process is a continuous steelmaking process, developed to supersede electric furnace. In its demonstration plant, melting of scrap was carried out by a hot blast, liningless cupola to supply the steelmaking furnace with molten iron continuously for several days. The essentials of the cupola are to avoid bridging, which is caused by growth of skull at watercooled stack shell, and to keep the molten iron temperature TM above a certain level. As a result of time series analysis with the records obtained during operation of the plant, following things were revealed.
    (1) When the correlation of heat loss from stack shell HS and windbox pressure PB is neglegible while that of HS and exhaust gas temperature TE is appreciable, considerable melting should be taking place near the shell, and bridging is anticipated.
    (2) As a function of blast temperature TB and % coke CR, the behavior of TM can be expressed by a time series model, which is useful for forecasting as well as checking the stationarity. According to this model, 10°C rise of TB should bring approximately 4°C increase in TM without appreciable delay in average. Effect of CR to TM is estimated to be 515°C/% with 34 h delay.
  • Effect of Oxide Inclusions on MnS Precipitation in Low Carbon Steel

    pp. 501-508

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    It has been known that precipitates of MnS become effective nuclei of intragranular ferrite during A3 transformation and improve the ductility of steels. The objective of this work is to investigate the effect of oxide inclusions on MnS precipitation after solidification in order to obtain uniform distribution of precipitates. Various deoxidizing elements were added to low carbon steel melt of 1 kg. This steel melt was solidified in an alumina crucible after some killing time. The nonmetallic inclusions were analysed by two-dimensional X-ray microanalyser on a cross-section of the ingot specimen. Among deoxidizing elements, the number of oxide inclusions of Hf, Ce, Y or Zr was greater and the distribution was more uniform than that of Al or Ti. The precipitation of MnS was followed effectively on those oxide inclusions between 1 100 and 1 400°C. The kinetics of precipitation was analysed by a precipitation model taking into account solidification and δ/γ transformation. The low diffusivity of Mn causes the depletion of Mn around MnS precipitates. It was considered that this Mn depletion promoted ferrite nucleation.
  • Influences of Microstructure on the Wear Resistance of High C-5Cr-V Steels for Work Rolls in Cold Rolling Mills

    pp. 509-516

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    Influences of microstructures on the wear resistance of high C-5%Cr-V steels are studied using a two-cylinder type wear test machine. Under the test conditions of low Hertz stress (100kgf/mm2)-high slip ratio (20%) and high Hertz stress (150200kgf/mm2)-low slip ratio (9%), the main results obtained are as follows.
    (1) The initial wear rate decreases with C content, which increases primary carbides and spheroidized carbides. However, the steady state wear rate is increased by pit-like flakings which often occur in the primary carbides.
    (2) The initial and steady state wear rates tend to decrease with the increase in V content up to the amount which makes the ratio of V content to C content, V/C, larger than 1. This decrease of wear rate closely relates to the fine precipitation of MC type carbides and the increase in the fraction of spheroidized carbides.
    (3) In the case of the steels having V/C of less than 1, the steady state wear rate increases with the increase in the spheroidized carbides and the retained austenite.
    Under the test condition of high Hertz stress and low slip ratio, the significant increase in wear loss is obtained in the steel having V/C of less than 1. It is indicated that the increase in wear loss is caused by the flaking which results from the nucleation, growth and coalescence of voids from the spheroidized carbides larger thab 1μm.
  • Improvement of the Ratio of Fatigue Limit to Tensile Strength in Hot Rolled Steel Sheets by the Surface Strengthening

    pp. 517-522

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    Plain bending fatigue strength has been investigated about the surface layer strengthened hot rolled steel sheets produced by intercritical rolling of cast composite ingot which in the surface layers, about 0.01%Nb-0.1%V are added on the 0.14%C-0.5%Mn base composition. Following results are obtained.
    (1) The ratio of fatigue limit to tensile strength becomes as high as about 0.67 in the polished specimens of 20% surface fraction. This value is very high compared with that of conventional uniform hot rolled steel sheets.
    (2) Fatigue limit of the 8% prestrained specimen is 4 kgf/mm2 lower than that of the non-strained at the 20% surface fraction. This decrease is caused by very low work-hardening property and residual tension stress in the surface layers.
    (3) It is thought that fatigue limit of surface layer strengthened hot rolled steel sheets is determined by that of surface or inner layer at large or small surface fraction each. At this transient region of surface fraction (1020%), the ratio of fatigue limit to tensile strength becomes maximum.
  • Corrosion Fatigue Behavior of 13Cr Martensitic Stainless Steels in 3 % NaCl Solution with a Special Reference to Their Intergranular Corrosion Susceptibility

    pp. 523-528

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    Corrosion fatigue tests of 13Cr martensitic stainless steels in several tempered states were carried out in 3% NaCl solution at room temperature, and the effect of metallurgical variables on corrosion fatigue strength at 107109 cycles was investigated. The followings are found : 1) Corrosion fatigue strength σWC monotonically decreases with the loading cycle. At 109 cycles, σWC decreases to 50MPa for some tempered states. 2) In a high cycle region, σWC strongly depends on the tempering conditions, and σWC of the steels sensitive to intergranular corrosion was relatively low because of the formation of deep pits. 3) The apparent stress intensity factor for corrosion fatigue cracking, Kcf, is about 1.62.5MPa√m at 107109 cycles and independent of tempering conditions. 4) The rate determining process for corrosion fatigue life under high cycle and low stress conditions appears to be that of pitting corrosion. 5) One of the effective methods to increase corrosion fatigue strength may be careful selection of the tempering conditions in which the Cr depleted zone is not formed.
  • Development of Oxide Dispersion Strengthened Nickel-base Superalloy

    pp. 529-536

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    An oxide dispersion strengthened (ODS) nickel-base superalloy, TMO-2 which has an extremenly high creep strength, has been developed by employing a matrix with a composition modified from that of a high temperature strength cast alloy previously developed based on the alloy design method of our institute.
    ( 1 ) The ODS superalloy TMO-2, when processed by mechanical alloying using nickel pellets of 3-7 mmφ as balls in the attritor, consolidation by extrusion, and isothermal annealing, showed a creep rupture life of 3 500 h under a test condition of 1 050°C and 16 kgf/mm2.
    ( 2 ) Another batch of ODS superalloy TMO-2, processed by mechanical alloying using steel balls of 9.5 mmφ in the attritor, consolidation by extrusion, zone annealing, and solution and aging heat treatment, showed a creep rupture life of 7 476 h under the same test condition of 1 050°C and 16 kgf/mm2 as in ( 1 ) above.
    ( 3 ) In some of long-time crept speimens of alloy TMO-2, the needle-like M6C has been developed. This is not harmful for creep rupture life but shows elongation values lower than those of specimens of ( 1 ) and ( 2 ) above.
  • Effects of Strain-induced Transformation and Temperature on Fracture Toughness of Titanium Alloys

    pp. 537-544

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    It is highly expected that the ductility and toughness of titanium alloys bearing unstable β phase may be developed by the stress relaxation caused by strain-induced transformation. In this study, tensile test, Charpy impact test, static and dynamic fracture toughness tests were carried out at various temperatures on typical titanium alloys bearing unstable β phase. The strain-induced α″ martensitic transformation occurred in the (α+β) type Ti-6Al-2Sn-4Zr-6Mo alloy and the dynamic fracture toughness of this alloy increased considerably at 223 K. The strain-induced α' martensitic transformation occurred in the (α+β) type Ti-6Al-4V alloy, and the static and dynamic fracture toughness increased considerably at 123 and 223 K respectively and strength increased at low test temperatures in this alloy. The mechanical twin occurred in the β type Ti-15V-3Al-3Sn-3Cr alloy and the elongation of this alloy increased considerably at 123 K.
  • Effect of Grain Boundary Carbide on High Temperature Creep Behavior of 15Cr-25Ni Steel

    pp. 545-552

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    In order to clarify the strengthening mechanism due to grain boundary carbide precipitation, creep behavior and dislocation substructure developed during creep of 15Cr-25Ni steels with different carbon content have been studied at 850 and 950°C under stresses of 14.7-79.2 MPa. With the grain boundary carbide precipitation, creep resistance and rupture life increased markedly, showing significant grain boundary precipitation strengthening by carbide. The minimum creep rate of γ single phase steel was independent on grain size, while it increased with increasing grain size in the steels with grain boundary carbide precipitation. With grain boundary carbide precipitation, dislocation density near grain boundary increased, but little difference in dislocation substructure within grains was observed in both steels. This suggests that grain boundary carbide strongly obstructs dislocation annihilation at grain boundaries, and therefore markedly increase the creep resistance. It is also suggested that the minimum creep rate of the steel with the grain boundary precipitation is controlled by recovery process near the grain boundaries instead of recovery at subboundaries which control the creep rate of γ single phase steel.
  • 八つあたり その2

    pp. 569-569

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