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

Tetsu-to-Hagané Vol. 77 (1991), No. 6

  • Recent Trend of Electric Furnace Steelmaking Equipment and Operation Technology

    pp. 723-734

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  • The Structure of Interphase Boundaries and the Ledgewise Growth of Precipitates in Metals and Alloys

    pp. 735-745

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  • Production of Magnetite Particles in Microorganisms

    pp. 746-751

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  • Sample Introduction Techniques for Inductively Coupled Plasma Emission Spectrometry

    pp. 752-758

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  • Effect of Fe Addition on Coke Gasification

    pp. 759-766

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    Gasification of metallurgical coke to which Fe had been added was studied at 1 000, 1 200, 1 400°C with Ar-CO-CO2 mixtures.
    The rate of gasification was accelerated by Fe addition. As the results of X-ray diffraction, carbon in coke was roughly classified into two groups, crystal and non-crystal carbon. However, there was no effect of Fe addition on carbon crystal size. Kinetic analysis was carried out on the basis of modified Langmuir-Hinshelwood type rate equation (K=k1ST PCO2/(1+k2PCO+k3PCO2), ST: ratio of total adsorption site to carbon atom), which has been adopted for conventional metallurgical coke. From the rate constants obtained for Fe doped coke, it was found that the high reaction rate was caused by decreasing of k2 and k3, which were inhibition term of reaction by CO and CO2, respectively.
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    Readers Who Read This Article Also Read

    1. Circulation and Reduction Behavior of Iron Ore in Circulating Fluidized Bed Tetsu-to-Hagané Vol.78(1992), No.7
    2. Analysis of Steam Flow in Coke Oven Chamber Tetsu-to-Hagané Vol.77(1991), No.8
    3. An Analysis on Exergy Consumption and CO2 Discharge in Ironmaking Systems Tetsu-to-Hagané Vol.77(1991), No.8
  • Development of a Cementless Cold-bonded Pellets Process

    pp. 767-774

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    At NSC Kimitsu Works, we have recently developed cementless cold-bonded pellets process using ground-granulated blast-furnace slag containing gypsum as a binder instead of cement. Ground-granulated BF slag hardens only when an alkali activator and water were added because of latent hydraulicity. We confirmed the effect of an alkali activator, water and atomospheric temperature ( curing temperature) on the hardening speed by pilot test. As a result of the tests, we developed cementless cold-bonded pelletizing process which shows same hardening speed as with cement. And the properties of cementless cold-bonded pellets are almost same and superior to those of cement cold-bonded pellets. So we have made a commercial plant that produced 40 000 t/month, and now we use 3% cold-bonded pellets for blast-furnace burden with good operating results.
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    Readers Who Read This Article Also Read

    1. Circulation and Reduction Behavior of Iron Ore in Circulating Fluidized Bed Tetsu-to-Hagané Vol.78(1992), No.7
    2. Analysis of Steam Flow in Coke Oven Chamber Tetsu-to-Hagané Vol.77(1991), No.8
    3. An Analysis on Exergy Consumption and CO2 Discharge in Ironmaking Systems Tetsu-to-Hagané Vol.77(1991), No.8
  • Upper Limits to Combustibility of Pulverized Coal in Blast Furnace Raceway and Desirable Injection Position

    pp. 775-782

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    1. An equation (1) for estimating the upper limit value (PCR)u (kg/t) of the pulverized coal injection rate in blast furnaces was derived from an experiment on the combustion of pulverized coal in the coexistence of coke and a mathematical model of the tuyere combustion zone.
    (PCR)u=(FR-254)/{0.0142(C)pc+0.0425(H)pc-0.0056(O)pc+0.15}……(1)
    Where FR: fuel rate (kg/t), (C)pc, (H)pc, (O)pc: ultimate analysis of C, H, O, in pulverized coal (% (dry)). The upper limit to the coal injection rate at which the pulverized coal can burn 100% in the tuyere combustion zone is 180 kg/t when the fuel rate is 500 kg/t.
    2. The upper limit to the particle size of granular coal injected into blast furnaces is 0.70 mm in terms of characteristic particle diameter (upper limit of particle diameter covering 80%(wt) of coal).
    3. An equation ( 2 ) for estimating the upper limit to the distance L (m) between the coal injection position and the tuyere nose at which scab does not form on the tuyere nose was derived.
    L≤(52dp*2-53dp*+17.5)/(PCR-30)……(2)
    Where dp*: characteristic particle diameter (mm), PCR: coal injection rate (kg/t).
    It is necessary to bring the injection position near the tuyere nose when the injection rate is increased.
    4. Since April 1990, Kimitsu No. 4 blast furnace has continued stable operation at a high-rate coal injection of 132 kg/t, proving that the coke replacement ratio does not decrease at a low theoretical flame temperature of 2050°C.
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    Readers Who Read This Article Also Read

    1. Circulation and Reduction Behavior of Iron Ore in Circulating Fluidized Bed Tetsu-to-Hagané Vol.78(1992), No.7
    2. Analysis of Steam Flow in Coke Oven Chamber Tetsu-to-Hagané Vol.77(1991), No.8
    3. An Analysis on Exergy Consumption and CO2 Discharge in Ironmaking Systems Tetsu-to-Hagané Vol.77(1991), No.8
  • Mechanisms of Formation of MgCr2O4 Spinel from MgO and Cr2O3

    pp. 783-789

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    The rate constant of parabolic law of MgCr2O4 spinel formation from MgO and Cr2O3 was measured during 1 573 and 1 873 K. The rate constant decreased according to -3/4 power of oxygen partial pressure less than about 30 Pa, increased according to 3/4 power one more than the oxygen pressure and was constant less than 0.1 Pa. On the other hand, the electric conductivity was constant against the oxygen pressure. The interface of spinel texture grown from MgO and Cr2O3 devided the spinel layer in the ration of 1:3, respectively. Concludingly, the rate of spinel formation is limited by the diffusion of chromium vacancy in the oxygen pressure more than 30 Pa and by that of interstitial chromium ion less than 30 Pa. In the oxygen pressure less than 0.1 Pa, the concentration of interstitial chromium ion is constant because of the solubility of MgO in the spinel. Finally, the dissolution rate of the spinel into molten slag was estimated using the rate constant of spinel formation.
  • Determination of a Partial Electronic Conduction Parameter of Solid Eelectrolytes for an Oxygen Sensor by using AC Two Terminals Method

    pp. 790-797

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    A new determination procedure of a partial electronic conduction parameter of a solid electrolyte applied to an oxygen sensor has been developed. It has been confirmed that the partial electronic conduction parameter measured with this procedure is the same that measured with a previous procedure, Swinkels method.
    The procedure has following advantages:
    1. The procedure can be applied to smaller size of solid electrolyte like 10 mm in long and 2 mm in diameter.
    2. The procedure has no restriction concerning the shape of the solid electrolyte.
    3. The solid electrolyte is not contaminated during the measurement.
    4. Measuring time is shorter than that by the previous method.
    The following partial electronic conduction parameters are observed:
    ZrO2-7 mol%MgO: log Pe'=19.1-70×103/T ZrO2-8 mol%MgO: log Pe'=19.8-70×103/T
    ZrO2-9 mol%MgO: log Pe'=23.9-70×103/T ZrO2-15 mol%MgO: log Pe'=25.7-70×103/T
    ZrO2-11 mol%CaO: log Pe'=37.8-91×103/T ZrO2-15 mol%CaO: log Pe'=37.8-91×103/T
    ZrO2-6 mol%Y2O3: log Pe'=20.1-63×103/T ZrO2-8 mol%Y2O3: log Pe'=20.1-63×103/T
  • Use of Oxygen Sensors in Steelmaking Companies during 1987 Year and Their New Uses

    pp. 798-804

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    The number of oxygen sensors consumed by Japanese steelmaking industries in 1987, the objects of use and the reliability of sensors were surveyed. 518 653 pieces of oxygen sensor were consumed in Japan and 157 700 pieces were exported to Taiwan, China and Korea. 26.3% of them consumed in Japan were used in converters, 9.9% in ladles, 53.9% in RH and DH, 5.6% in secondary refining, 3.2% in the tundishes of continuous casting and 1.0% in electric furnaces. Main objects of the uses were almost the same as the results of survey in 1985, that is, the determination of the amount of deoxidizers and the control of aluminium content in steel. Oxygen sensors were also used in converters for the estimation of contents of phosphur and manganese in steel at blow-end. Discussions on the reliability of oxygen sensors and the other technics for determining the contents of elements in steel were made.
  • On-line Analysis for Manganese in Molten Iron by Measurement of Emission Spectrum at Hotspot during Oxygen Blowing

    pp. 805-811

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    Recently, there are great demands for the development of direct analysis methods for molten iron in order to monitor the reactions of in steel making processes. In this paper, the new on-line analysis method for manganese in molten iron is developed and the theoretical background of the method is clarified. The analytical method realizes the real-time and continuous measurement of manganese concentration during the decarbonization process in a converter. This method is based on the measurement of atomic emission spectra of manganese and iron radiated at the high temperature zone called "hotspot", which is formed on the surface of molten iron when the oxygen gas jet impinges on it for decarbonization.
    In the actual analysis, the emission intensity ratio of manganese to iron is measured in order to eliminate the influence of dusts and surface level fluctuation. The ratio has the adequate correlation to manganese concentration, which is represented as follows;
    I(Mn/Fe)=K'(T)·[Mn]n
    "K'(T)" is a function of the hotspot temperature and "n" is a self-absorption factor. "K' (T)" represents the effect of hotspot temperature on the ratio of the vaporization rate of mangnese and iron from molten iron. There is the fairly good correlation between the manganese concentration obtained by this method and that obtained by the conventional sampling method, and the coefficient of their correlation is 0.942 in the concentration range from 0.26% to 1.09% of manganese.
  • An Interpretation of Effect of Mn on Snoek Peak of Low Carbon Steels

    pp. 812-815

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    There are two interpretations for the decrease in carbon atom Snoek peak of low carbon steels by addition of manganese, i.e., decrease in solubility of carbon in ferrite and decrease in intensity of internal friction due to formation of carbon-manganese complex. Reported Snoek peak data are analyzed on the following assumptions, on the basis of the reported fact that the solubility of carbon in ferrite is not influenced by presence of manganese:
    (1)Solute carbon atoms([C]) are distributed on interstitial sites adjacent to manganese atoms([Mn-C]) and on those free from manganese atoms([Free C]).
    (2)Their partition between the two sites is in thermodynamical equilibrium.
    (3)Carbon atoms contribute to internal friction in characteristic ways of the two types of occupying sites.
    The analyzed data including newly measured ones on ageing process are consistently explained by these assumptions under the condition that the equilibrium partition is established at temperatures of measurements.
  • Effect of Applied Tensile Stress on the Transformation Behavior of Medium Carbon Low Alloy Steels

    pp. 816-823

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    In order to accelerate the ferrite-pearlite transformation of medium carbon low alloy steel bars, the possibility of controlling the transformation behavior by application of the tensile stress during cooling after rolling was investigated. Tensile stress was applied by controlling the strain rate considering the stress drop due to relaxation. It was found that acceleration of ferrite transformation was occured by developed method. This results proved this method to be effective for softening the rolled bars. Furthermore, increase of uniform elongation up to about 60% occured in the case of straining during transformation. Discussion was focussed on the role of the applied stress and it was concluded that applied stress increased the internal stress of the austenite and resulted in the increased nucleation rate of ferrite transformation.
  • High Temperature Tensile Properties of Ti-15V-3Cr-3Sn-3Al Alloy and Its Microstructural Changes during the Deformation

    pp. 824-831

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    Effects of an initial structure and deformation temperature on high temperature tensile properties of the Ti-15V-3Cr-3Sn-3Al alloy have been investigated by carrying out microstructural observations and tensile tests in a temperature range which is straddling the β-transus temperature being about 1 015 K. The main results obtained can be summarized as follows.
    1) The specimen which was in an as cold-rolled state showed a larger total elongation, in particular than other specimens in which recrystallizations had already been finished.
    2) The initial microstructure of the specimen in the as cold-rolled state was seen to change, during tensile deformation below the β-transus temperature, into a fine grained (α+β) structure in which granular α phases were uniformly dispersing. As the result, the total elongation and flow stress of the specimen deformed below the β-transus temperature were found to be much more improved than those of the specimens already having fine recrystallized microstructures before heating to the test temperature.
    3) The present experimental results suggest that the main deformation processes of this alloy at high temperatures would be both superplastic flow and dynamic recovery which would be accompanied by a continuous recrystallization.
  • Development of a Nickel-base Single Crystal Superalloy

    pp. 832-839

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    In order to improve oxidation resistance and creep-rupture strength of SC-83, a single crystal superalloy for gas-turbine blades, which has been developed by an alloy-designing method and possesses much higher temperature capability than conventional single crystal alloys, the effects of the addition of Hf and Co and the increase of "Solubility Index" were investigated.
    The optimum solubility index value was 1.5 and the addition of small amounts of Hf and Co increased oxidation resistance greatly and creep rupture strength slightly.
    The finally developed alloy SC-83K which contains 0.1% Hf and 1% Co has much higher creep rupture strength than conventional alloys as well as good structural stability and oxidation resistance.
  • Effects of Cr and Al Contents on the Pulse Response Property in Soft Magnetic Stainless Steels

    pp. 840-847

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    Soft magnetic stainless steels are used for the yoke in fuel injectors to require a good corrosion resistance. The pulse response property of the yoke material is essential to the dynamical performance of fuel injectors. However, effects of alloying elements on the property is not clear.
    An equipment measuring the pulse response property is devised to investigate various Fe-Cr-Al alloys including commercial magnetic stainless steels. The ring specimens used in the equipment are provided with a slit to simulate the injector system. The magnetic response to a magnetizing pulse current is measured so that the relaxation time can be obtained to estimate the pulse response property.
    The results obtained show that the relaxation time mainly depends on the specific resistance of the alloy specimens. It decreases with the increase in the specific resistance, though the magnetic properties such as the coercive force are hardly affected. As a result, it has been found that a soft magnetic stainless steel of 10Cr-3Al composition is recommendable to the yoke material, better than 45Ni-permalloy or 12Cr-0.8Si-0.3Al stainless steel previously used.
  • X-ray Fluorescence Analysis of Tl-Ba-Ca-Cu-O Superconductors by Microdroplet Analysis-FP Method

    pp. 848-855

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    In the accurate analysis of the superconductor Tl2Ba2CanCun+1Ox -Hereafter, superconductor composition is written as (2223), when n=2- by X-ray fluorescence spectrometry, the microdroplet analysis technique combined with the fundamental parameter method has been found to be suitable because of the following reasons. The superconductor contains both poisonous and high-temperature-volatile thallium, and has few or no available standards. By this combined method, we determined components in superconductors (2223) and (2212), and obtained the results below.
    1) Specimens were prepared by dissolving 1 g of sample with 10 ml of nitric acid (1+1), followed by dropping the solution onto formed filter papers asa much oxides as 0.353 mg/ cm2.
    2) Standards were prepared via the same sample solution process as specimens, from the samples of known compositions and analogous matrices.
    3) In addition, by adopting the homogeneous mixture of nitrates and the filter as a model for both specimens and standards, Tl2O3, BaO, CaO, and CuO in superconductors were determined with the respective accuracies σd's (differences from wet-chemical values) of 0.70 wt%, 1.06 wt%, 0.17 wt%, and 0.29 wt% in the case of (2223), and of 0.53 wt%, 0.73 wt%, 0.14 wt%, and 0.19 wt% in the case of (2212), which were fairly good.
    4) Absorption enhancement effects for TlLα1, BaKα, CaKα, and CuKα under the present analytical conditions were calculated. However, they were recognized only in the case of CaKα and CuKα.
  • Some Views on the Slag Foaming in Iron and Steelmaking Processes

    pp. 856-858

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    Readers Who Read This Article Also Read

    1. Circulation and Reduction Behavior of Iron Ore in Circulating Fluidized Bed Tetsu-to-Hagané Vol.78(1992), No.7
    2. Analysis of Steam Flow in Coke Oven Chamber Tetsu-to-Hagané Vol.77(1991), No.8
    3. An Analysis on Exergy Consumption and CO2 Discharge in Ironmaking Systems Tetsu-to-Hagané Vol.77(1991), No.8

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