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

Tetsu-to-Hagané Vol. 65 (1979), No. 2

  • Overflow Pipe and Partition Plate in Fluidized Bed with Multi-Stages and Multi-Rooms

    pp. 169-175

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    An investigation was carried out to obtain the stabilizing conditions for the flow of solid particles in a continuous fluidized bed both with overflow pipes and partition plates, using a cold model made of glass.
    (1) Amounts of gas introduced into overflow pipe, when l>l'>7.5, qbqmf and qcqmf were given by the following equations.
    In batch operation, In continiuous operation, qb=Qp (d'/D) 2ψb.
    In continiuous operation, qc=Qp (d'/D) 2ψc-Fs (1-εf) ·103
    It was suggested that qc must be nearly equal to qmf in order to maintain the stabilization of gravity flow of solids through the overflow pipe.
    (2) The pressure difference, at a level, between the beds separated by a partition plate was decreased with increasing the height above the gas distributor.
    In order to minimize the height difference in these two beds, the partition plate with a slit at lower level was effective.
    (3) It was suggested that the overall solid mixing behavior in two fluidized rooms, separated by the partition plate with a partially formed moving bed of solid particles, was similar to that expected for two complete mixing stages in series.
  • Fluidization of Iron Ore Particles at High Temperature and Pressure

    pp. 176-184

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    For stable operation of continuous fluidized bed reduction of iron ore at high temperature and pressure, fluidizing conditions of iron ore particles of a wide size distribution were investigated using a fluidized bed model at room temperature.
    At a certain fluidizing velocity it was possible to maintain these iron ore particles of the wide size range at good fluidization, in which the particle size distribution in bed was almost uniform during the continuous operation and the dust from the bed was a little in the amount. On the basis of this suitable fluidizing velocity obtained from the experiment of a cold model, fluidizing velocities corresponding to the change of factors such as temperature, gas composition, and reduction degree of iron ore were calculated.
    The controlling method of the flow rate of reducing gas and gas pressure in the reactor in a continuous operation from the start up at room temperature to the steady state at high temperature was devised.
    According to this controlling method, the continuous operation of a pilot plant using nitrogen and hydrogen as fluidizing gas was performed at high temperature and pressure.
  • Operation of Pilot Plant for Fluidized Bed Reduction at High Temperature and Pressure

    pp. 185-194

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    In order to develop a direct reduction process by fluidized bed, experimental operations of a pilot plant were carried out. The plant comprised multiple fluidized beds with both counter current and cross current contacting of ore and gas in a reactor of 25 cm inner diameter.
    The results are summarized as follows.
    1) Stable and sintering-free continuous operation at a maximum temperature of 900°C was carried out, using coarse particles of Hamersley iron ore (16-115 mesh) under pressure of 7 kg/ cm2G; the product of a reduction of above 95% was obtained, the utilization of hydrogen gas was 17%, and productivity was 55 t/m2d.
    2) The distribution of fractional reduction in a fluidized bed was surveyed by magnetic separation of samples obtained from the bed. Reduction rate of particles in the bed was obtained directly from the distribution curve. An operation analysis was made on this information of particle reduction.
    3) Operations using a partition plate designed by the authors were successful and effective to increase reduction of products and productivity.
  • Rate of Melting of Partly Reduced Iron Pellets into Iron Melt

    pp. 195-202

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    Rate of melting of partly reduced iron pellets into iron melt was obtained by measuring CO gas evolved. The effects of composition of pellets as well as temperature and carbon content of iron melt on their melting rate into the melt have been investigated. The following results are obtained:
    (1) Apparent activation energy of melting of reduced iron pellets containing 0, 10, 20 and 40% Fe2O3 was 33 kcal/mol.
    (2) Without slag melt on the iron melt, the maximum melting rate of pellets containing 10, 20 and 40% Fe2O3 was obtained at about 3.3, 3.0 and 2.5% carbon contents respectively.
    (3) Melting rate was proportional to -0.5 power of Fe2O3 content at the range of 15-60%Fe2O3, increased at 2-10% Fe2O3 and decreased above 70% Fe2O3.
    (4) CaO, CaCO3 or C of 2-5% as addititive increased the melting rate of pellets, but addition of Al2O3 or SiO2 decreased it extremely. Simultaneous addition of CaO and SiO2 (CaO/SiO2=1) and addition of pre-fused slag whose melting point was low decreased the melting rate slightly up to 5%, and their content in pellets should be limited within 15%.
  • Theoretical Analysis on the Effective Distribution Coefficient for Solidification Accompanied with Liquid and Solid Region

    pp. 203-211

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    The effective distribution coefficients for solidification proposed hitherto are classified according to the morphology and the solidifing condition. In this paper, two cases for the solidification accompanied with a liquid and solid region have been theoretically analyzed by taking account of the diffusion in solid phase (case XII) or the diffusion boundary layer in front of the liquid and solid region (case XIV). In these cases, four kinds of effective distribution coefficient which were defined in the previous paper are represented by the theoretical formula. The representative effective distribution coefficient (K*3), which is the solid composition divided by bulk liquid composition, is formulated in the both cases as follows:
    K*3=K {1-A/ (Le) 2-K (1+τ) -2}
    case XII

    K*3= {1+1-exp (-Rδ/Dl) /Le (1-K/2) -1·AK/2} K/K+ (1-K) exp (-Rδ/Dl) -AK/ (Le) (2-K) -2
    case XIV
    Furthermore, by the use of the analytical results, the data concerning the macrosegregations in uni-directionally solidified Al-Ag alloys reported by the other authors are analyzed. The theoretical results have been in good agreement with the experimental data.
    In comparison with the two extreme cases for diffusion coefficients in solid phase, Ds=0 and Ds=∞, in the solidification accompanied with liquid and solid region, the effects of the diffusion in solid phase are given quantitatively.
  • Extremely Slow Strain Rate Stress-Corrosion Testing Machine and Some Experimental Results

    pp. 212-218

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    An extremely slow strain rate testing machine for stress-corrosion cracking (SCC), which can be continuously controlled with cross-head speeds over the range of 1.5×10-5cm/s to 7.7×10-9cm/s, has been newly devised and constructed.
    Stress corrosion behavior of Type 304 stainless steel in 143°C 42%MgCl2 at the potential of-0.34 V (SCE), and of Inconel 600 and Incoloy 800 in 140°C 50%NaOH at the potential of 0 V (SCE) was examined by the newly devised testing machine.
    SCC was observed to occur most severely at a strain rate of 3.3×10-6 s-1 for 304 stainless steel and 1.7×10-6 s-1 for Inconel 600 and Incoloy 800, and the susceptibility decreased at strain rates faster or slower than those for all specimens tested. For 304 stainless steel transgranular cracking was formed at the region of slower strain rates and intergranular at faster strain rates but the reverse was the case for Inconel 600 and Incoloy 800.
  • Strength and Low Temperature Toughness of High Manganese Austenitic Fe-Cr-Ni Alloys for Cryogenic Service

    pp. 219-225

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    Mechanical tests were carried out on high manganese austenitic iron alloys for cryogenic service to study the effect on the strength and the toughness at lower temperatures. Addition of manganese to austenitic Fe-Cr-Ni alloy can improve neither the strength nor the toughness. Impact energy decreases as manganese content increases. Although homogenization at 1000°C (1273K) for 24 hours gives rise to coarsning of the grain size, the proof stress and the toughness are remarkably improved. The improvement would be attributed to solution of carbides, which would be nucleation sites for void formation in ductile fracture. In this experiment, 30%Mn-5%Ni-15%Cr and 20%Mn-10%Ni-15%Cr iron alloys are recommended as cryogenic structural materials from the view point of the stability of austenitic phase at 4 K. However, the higher nickel alloy results in the better balance of strength and low temperature toughness than the higher manganese alloy.
  • Effect of Plate Thickness on Fracture Toughness by Means of Elastic-Plastic Fracture Mechanics

    pp. 226-234

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    The effect of plate thickness on fracture toughness in terms of J-integral concept, Jc, has been investigated using a heavy section A533B steel (165mm in thickness) which has highly uniform toughness in thickness direction except for surface layer. Notched bend specimens were prepared from this uniform region by varing thicknesses from 3mm to 100mm in order to minimize the metallurgical effects and tested at various low temperatures.
    The results are summarized as follows:
    (1) A new, simple technique of Jc estimation is proposed. According to this method, Jc values can be easily obtained using only the information from COD test which is represented by fracture load and critical clip gage displacement.
    (2) There exists an evident effect of plate thickness on fracture toughness in cleavage fracture. Using KC which is converted from Jc, the effect is formulated as follows:
    KIC=KC/ (1+2.3βC) 1/2, β2C= (KCY) 2/B
    where KIC is plane strain fracture toughness and KC is fracture toughness at plate thickness of B. δY is yield stress.
  • Effects of the Widmanstatten-like Reversed Austenite on Mechanical Properties in Fe-Ni Alloys

    pp. 235-244

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    The effects of morphology, size and stability of reversed austenite (γrev.) on the mechanical properties have been investigated in very low C-high Ni-Steels with particular reference to the Widmanst@/au56/@tten-like γrev. (γW). The main results are summerized as follows:
    (1) Precipitation of γW caused increase of tensile strength and yield strength of steels investigated.
    (2) Strengthening by the precipitation of relatively stable γW was detrimental for the increase of ductility at low temperature, which is the characteristic of low C-Ni-Steels.
    (3) When the stability γW was relatively low, the high ductility at low temperature was obtained together with remarkable strengthening by γW.
    (4) Increase of absorbed energy together with some strengthening was observed in the steels in which small amounts of very fine γW precipitated.
    (5) The marked strengthening by the precipitation of a large amount of γW decreased absorbed energy. Precipitation of (γLB) along the lath boundaries did not cause remarkable increase of hardness but the decrease of absorbed energy by large amounts of γLB was smaller than that by γW.
  • Mechanical Properties of Sintered Iron Sheets Containing Dispersed Oxide Particles

    pp. 245-253

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    Oxide (SiO2 orAl2O3) particles were cmbeded to iron powder, and they were pressed, sintered at 850°C for 1 hr in a hydrogen atmosphere, rolled and annealed. The recrystallized grain size and the textures of the sheets were examined, and the reiatienship between these characteristics and tensile properties of the sheets were discussed.
    Effects of fine oxide particles added (amorphous SiO2 and γ-Al2O3: about 200Åφ) on the mechanical properties of the sheet were found to be remarkably high comparing with those of larger size (α- SiO2and α-Al2O3: about 2μmφ). In this case, the elongation decreased in general owing to fine recrystallized grain size in the matrix, although its increase appeared in the range of 0.4-0.7 vol. %addition in iron sheets. This fact suggested that the elongation was affected by the annealing texture which had been changed by additive content in the sheet.
    As a result, it was found that the dispersed oxide particles and the restraint of recrystallization of the sheet by these particles improved the strength of the sheet, and exerted a major influence on the other mechanical behaviours. Moreover, it was considered that a compound was formed at the inter-face between iron and oxide (SiO2 or Al2O3) during the sintering process.
  • The Bending Strength and Fracture of High Carbon High Vanadium Iron Alloys

    pp. 254-263

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    Micro-bending test and microscopic examination were carried out on high carbon high vanadium iron alloys prepared by melting and by over-laying method, in order to study the effects of size and distribution of V-carbide on the bending strength of the alloy. V-carbides in the specimens were controlled from 21 to 55% in volume and from 2 to 100 μm in diameter, dispersing in matrix of the ferrite, austenite and martensite. It was observed that cracks originated in the carbide phases due to a stress concentration, and was propagated iuto the matrix. The strength of the alloy was more in fluenced by the size than the amouut of the carbide. The cleavage fracture occurred partly in alloys containing much amount of V-carbide, even if the matrix was fully annealed.
  • Mass Spectrometric Determination of Activity of Phosphorus in Liquid Fe-P Alloy

    pp. 264-272

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    The activities of P and Fe in a dilute solution of P in liquid iron at 1600°C have been determined with a combination of a mass spectrometer and a Knudsen cell; a magnetic deflection type mass spectrometer was used. A pulse counting system was used for the measurement of the ion currents of P+ and P+2, for the intensities of these ions were very small; the relatively large ion currents of Fe were measured with a DC amplifying system. The whole system was computer-controlled, and a high sensitivity with a large dynamic range and considerable resolution could be obtained by using this system.
    The range of the concentration of phosphorus was from 0.7wt% to 3.2wt% (1.3at% to 5.7at%), and the method based on the GIBBS-DUHEM relation was used to obtain the interaction coefficient, εPPfrom the obtained ion current ratios, and εPP= 7.3±0.1was obtained.
    The accuracy and the precision of the obtained value are discussed.
  • Mass Spectrometric Determination of Activities of Phosphorus in Liquid Fe-P-Si, Al, Ti, V, Cr, Co, Ni, Nb, and Mo Alloys

    pp. 273-280

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    The interaction coefficients for phosphorus have been determined in the Fe-P-i systems at 1600°C. The experimental technique is the same as described in the paper on the Fe-P systems which was reported previously. The measured systems are Fe-P-Si, Fe-P-Al, Fe-P-Ti, Fe-P-V, Fe-P-Cr, Fe-P-Co, Fe-P-Ni, Fe-P-Nb, and Fe-P-Mo.
    The experimental results show that the interaction coefficients for phosphorus with the elements in the fourth and fifth periods increase with the atomic number of the elements.
    The results obtained are summarized as follows:
    εSlP=12.6±0.6 (11.9±0.6)
    εTlP=-8±2
    εCrP= -3.8±0.7
    εNlP= 0.7±0.7
    εMoP= 0.4±0.7
    εAlP= 4.6±0.7
    εVP= -4.9±0.7
    εCoP= 0.9±0.7
    εNbP= -5.4±1.2
  • Determination of Oxygen in Steel and the Investigation of the Reference Material for Calibrating the Instruments of Oxygen Analyser by Means of Carrier Gas Extraction-Nonaqueous Titrimetry

    pp. 281-285

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    The nonaqueous titrimetric method for the determination of microamount of CO2 was introduced to determine oxygen in steel. Carbon monoxide extracted from a sample by the usual carrier-gas fusion method was oxidized with CuO at 750°C, and the dioxide produced was absorbed with N, N-dime-thylformamide containing 5% of monoethanolamine, and then titrated with the standard solution of tetra-n-butylammonium hydroxide in benzene-methanol. Satisfactory results could be obtained especially for the samples of low oxygen-contents. Sucrose was next investigated as a reference material to calibrate the instruments for the determination of CO or CO2. The definite amount of its standard solution was taken into a small gold boat and evaporated at 50°C in vacuo. The boat was then introduced into a small-mouthed graphite crucible heated at 1 900°C. Stoichiometric recovery of oxygen from the sucrose could be obtained under nearly the same extracting conditions as those for oxygen from steel samples. Thus, sucrose may be used as the reference material in order to calibrate the instruments for the analyses of both oxygen and carbon.
  • On the General Material Balance Equations for the LD Converter Process

    pp. 286-288

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    The general and shortened material balance equations for the LD converter process are derived by using linear mathematical expressions. By solving these simultaneous equations properly, we can obtain the reacted weights of metal phase components and some other unknown weights of dissolved raw materials. The solutions thus obtained satisfy the material balance equations for all constituents that are taken into consideration. The solutions can be applied in many theoretical discussions for the LD converter process.
  • The Recent Trend of Wear-Resistant Materials for Construction Machine and Heavy Equipment

    pp. 289-299

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  • Recent Metallurgical Aspect of Line Pipe and Oil Country Tubular Goods

    pp. 300-310

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  • History and Future of Iron-and Steelmaking Technology

    pp. 311-314

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  • ミシガン大学〔アメリカ〕

    pp. 315-316

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  • 抄録

    pp. 317-318

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  • 第97回講演大会討論会講演概要

    pp. A1-A16

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  • 第97回講演大会討論会講演概要

    pp. A17-A40

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  • 第97回講演大会討論会講演概要

    pp. A41-A60

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  • 第97回講演大会討論会講演概要

    pp. A61-A84

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  • 第97回講演大会討論会講演概要

    pp. A85-A116

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