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

Tetsu-to-Hagané Vol. 77 (1991), No. 1

  • R & D and A & C

    pp. 19-26

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  • Research and Development of Coal Gasification and Liquefaction

    pp. 27-35

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  • Chemical Processing of High Temperature Oxide Superconductors (II)

    pp. 36-45

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  • On-line Analysis of Molten Steel in Steel Making Processes

    pp. 46-55

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    [in Japanese]
  • Influence of Property of Iron Ores on the Coalescing Phenomenon of Granules during Sintering

    pp. 56-62

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    The fluidity and amount of formed melt seem to be important factors for the coalescing of granules in the iron are sintering process, since the coalescing phenomenon is essentially based on the bonding among unfused particles with the melt formed by the partial fusion of the granules. In this study, simplified sintering experiments was conducted using tablets consisted of the mixture of an iron are and limestone so as to estimate the fluidity of raw materials qualitatively at high temperatures. As the results, it was found how the sintering temperature, mixing ratio of limestone, kind and particle size of iron ores used and so forth influence the fluidity. The results also suggested that the segregation of materials affects significantly the fluidity. A fair linear relation was found between the fluidity obtained for the adhering mixtures of the modeled granules and the strength of the sintered granules. Further, the effect of the pre-calcination of limonitic ore, which was used as cores of the modeled granules, on the strength after sintering was examined.
  • Characteristic of Raw Mix Packed Structure on Sinter Strand with Chute Type Feeder and Its Effect on the Sintering Reaction

    pp. 63-70

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    Details of raw mix packed structure with current chute feeder and their effect on sintering reaction were analyzed. The chute feeding method cannot avoid the problem of avalanches, which makes it difficult to enlarge and control the degree of grain size segregation in the bed height by making simultaneously the sandwich-like structure of fine and coarse particles. The larger the raw mix feed, the larger the avalanches and the disturbunce of sintering reaction. Enlargement of continuous material grain size segregation in the bed height without sandwich structure is effective in improving both yield and productivity by homogenizing sintering in the sinter bed.
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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
  • Investigation on Behavior of Unburnt Pulverized Coal in Blast Furnace

    pp. 71-78

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    In order to clarify the combustion reaction when PC (Pulverized Coal) is blown into the tuyeres of blast furnace and the effects of resultant unburnt PC on in-furnace reactions, some fundamental experiments were carried out. The main results obtained are as follows.
    (1) Most of PC blown through the tuyeres rapidly burns in the raceway, but part of PC may be carried out of raceway without being burnt.
    (2) Unburnt PC tends to adhere to the softened and fused are bed. Unburnt PC adhering to the ore bed is consumed for the direct reduction of FeO, and effectively improves the high-temperature properties of ores.
    (3) The gasification reaction rate of unburnt PC is larger than that of coke. The presence of H2 enhances the reaction, whereas that of CO inhibits it.
    (4) Since unburnt PC is selectively gasified, the reaction rate of lump coke lowers, and thereby the degradation of coke in the raceway may be inhibited.
    In this way, PC entering the blast furnace without being burnt was found to be effectively consumed. However, since the ash could built up in front of tuyeres, it is necessary to examine an actual blast furnace by sampling in-furnace materials to mitigate combustion conditions, to expand the range of usable quality of burden materials and to search possibility of blowing a great amount of PC.
    x

    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
  • Application of Neural Network to the Distribution Pattern Recognition of Blast Furnace Data

    pp. 79-84

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    As for operation of the blast furnace, it is important to recognize the distribution pattern of measured furnace data. Usually, these data are identified visually by human experts. Recently, the neural network technology is expected to be a new technology realizing the artificial pattern recognition of the data in good agreement with human judgement.
    In this paper, the application of back propagation type neural network to the pattern recognition of blast furnace data is studied. This type of network can distinguish some specific pattern from others after learning typical teaching data. Such teaching data can be arranged in two ways. One way is to choose typical pattern out of the actual operation data. The other way is to create artificial teaching data, when it is difficult to find out that data from actual data. As for the recognition of the top gas temperature distribution in furnace the actual data are prepared for learning and for that of burden profile recognition, the artificial data are adopted. In both cases, the neural network succeeded in recongnition regardless of noises existing in the data.
    x

    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
  • Shape Control of Molten Metal Rivulet Flow by Directly Imposing Electric and Magnetic Fields

    pp. 85-92

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    A new process to control the shape of molten metal rivulet flow is proposed in which direct electric and magnetic fields are imposed directly on molten metal to induce electromagnetic force. The experimental works were carried out to clarify the characteristics of shape control function of electromagnetic force in rivulet flow. It was found that electric current and flow velocity are the most important factors in this process. It is noticed that this process can control the shape of molten metal more dynamically than previously proposed process in which only magnetic field is imposed.
    The experimental data verify a mathematical model which can predict the shape of rivulet flow from the conditions of electric current, magnetic field and flow velocity. The fact that height and width of the flow have good correlation with Stuart number indicates that this rivulet flow is dominated by inertia force and electromagnetic one.
  • Production of Extra Low Oxygen Titanium by Calcium-Halide Flux Deoxidation

    pp. 93-99

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    Under co-existence of calcium and its oxide, the equiliblium oxygen content in titanium is 500 mass ppmO at 1 273 K1)2). The advanced methods were examined to attain the lower oxygen level from the thermodynamic viewpoints. Calcium-halide fluxes may decrease the activity of by-product CaO so efficiently that Ca-CaCl2 and Ca-BaCl2 fluxes were experimentally applied for the deoxidation of titanium.
    Titanium wires and small pieces containing a few hundreds mass ppm were deoxidized as low as a few tens mass ppm by use of CaCl2 flux and calcium vapor at 1 273 K. The oxygen sources to make worse the efficiency of the further purification of titanium were discussed and one of them was suggested to be the oxygen contamination in the flux.
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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
  • Hardened Depth Measurement Technique by Using Sound Velocity for Work Rolls of Cold Strip Mill

    pp. 100-106

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    In order to measure the hardened depth of quenched work rolls non-destructively, a technique using sound velocity distribution in the rolls was studied.
    The sound velocity can be measured by ultrasonic transducers, which are set on a roll surface so that the ultrasonic sound travels on a polygonal beam path in the roll. The velocity is average one in a certain range of depth.
    The sound velocity at each depth can be calculated using the average velocity on the transfering route, and then the sound velocity distribution from outer surface to internal portion is obtained.
    It is well known that there is a linear relationship between sound velocity and hardness. The sound velocity and hardness of the rolls are influenced by quenching temperature and residual stress. Therefore, if we want to estimate the hardened depth of a roll, we have to know the relationship between sound velocity and hardness of a test block cut out from a roll at first as an original data. And then, the hardened depth of a roll can be estimated using the relationship of the test block.
    The accuracy of the estimation of hardened depth is within +/-3mm.
  • Friction and Wear Properties of Graphite Cast Iron for Hot Working Rolls

    pp. 107-114

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    Two-disc type wear test and disc-block type adhesion test were conducted on the graphite cast iron roll material in hot rolling mills for the purpose of improving its wear and adhesion resistance. The effects of the amount of graphite in microstructure on friction and wear behaviors of the graphite cast iron were studied under the mild and severe conditions. Austenitic stainless steel SUS304 and carbon steel S45C were selected as the mated materials.
    The coefficient of friction is decreased by the increasing amount of graphite in microstructure, independent of mated materials and adhesion test conditions. Wear rate can be decreased by the increasing small amount of graphite, but it is increased by the increasing large amount of graphite, except for the case of the mated material S45C under the mild wear condition where wear rate is increased by the increasing amount of graphite.
    A new friction and wear model is proposed and it enables to explain these experimental results.
  • Effect of Phosphate and Silica Additives on the Performance and Structure of Chromate Conversion Coatings on Electro Galvanized Steel Sheet

    pp. 115-122

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    The performance and structure of chromate conversion coatings with phosphate or silica additives applied on the electro-galvanized steel have been investigated, and double roles of these additives in the film structure were proposed.
    It was found that phosphate reduces hexavalent chromium content, which is the possible reason for improvement of appearance and the adverse effect on corrosion resistance. While silica was found to form a bulky layer that can disperse yellowish hexavalent chromium and hold stable zinc corrosion product within the film, which can be related to the improvement of appearance and corrosion resistance.
    Phosphate forms a less-polor outer layer which repels paint, water and fingerprint. This is ascribable to the poor paint adhesion, relatively good wet adhesion and excellent fingermarking resistance of phosphate containing chromate. On the other hand, silica forms a polar outer layer which attracts paint, water and fingerprint. This is why the silica-containing chromate showed good paint adhesion as well as poor wet adhesion and a great amount of fingerprint adhered to its surface.
    The optimum film structure was designed based on these results.
  • High Temperature Oxidation of Fe-Si Alloys in Ar-H2O Atmospheres

    pp. 123-130

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    The oxidation of Fe-(1.5, 3%)Si alloys at 1000-1400 K has been investigated in Ar-(1, 10%)H2O atmosphere using metallographic and electron probe microanalysis techniques.
    The scale layers developed consisted in general of the external, the internal and the subscale. Oxides phases in each scale layer were identified as the mixtures of FeO, Fe2O3, and small amount of Fe3O4, the mixtures of FeO and Fe2SiO4, and the mixtures of Fe2SiO4 and SiO2 respectively.
    With increase in Si content in the alloys the rate of the total oxidation decreased significantly at 1 200-1 300 K. The oxidation kinetics of Fe-3%Si alloy and Fe-1.5%Si alloy were irregular and regular with each temperature, respectively. The latter was obeyed a parabolic rate law. The apparent activation energies for the growths of the internal scale and the subscale of Fe-1.5%Si alloy were estimated to be 123-132kJ/mol and 119-156 kJ/mol, respectively. The rate determining diffusion element for these scale growths was considered to be Fe in FeO in the internal scale and /or in the external scale.
  • Mechanical Properties of Cold-worked and High-Low Temperature Duplex Aged Ti-15V-3Cr-3Sn-3A1 Alloy

    pp. 131-138

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    Mechanical properties were studied by tensile test of Ti-15V-3Cr-3Sn-3A1 alloy obtained by duplexaging after cold-swaging, i.e. aging at higher temperatures followed by reaging at a lower temperature. Combinations of short-time aging at 823 K, 873 K and 923 K and reaging at 673 K have improved strength-ductility balance of this alloy greatly, realizing high strength of about 1.8 GPa with tensile elongation of 5%. This duplex aging process further diminishes the influence of reduction of cold-swaging on mechanical properties after aging.
  • Production of Ti-5Al-2.5Fe Alloys by the Blended Elemental Method with Microstructural Modification and Their Mechanical Properties

    pp. 139-146

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    The aim of the present investigation was to produce highly fatigue tolerant P/M Ti-5Al-2.5Fe by the microstructure-controllable Blended Elemental (BE) method, in which as-sintered preforms are quenched from the beta phase region prior to HIP'ing. An extra low chlorine titanium powder and a 53.6Al-26.3Fe-21.1Ti master alloy powder were used as starting materials. The microstructure consisted of fine alpha-beta two phase structure with massive alpha phase at grain boundaries (GB). The highest fatigue strength at 107 cycles, 60 kgf/mm2, was obtained for the compacts HIP'ed at 850°C, which was equal to that reported for Ti-6A1-4V compacts produced by the same method. However, the fatigue ratio at 107 cycles was lower and the scatter of the fatigue data was larger. The examination of the fatigue crack initiation sites by the precision sectioning method revealed that the lower fatigue life was related to the fracture along GBα boundary. The fatigue crack initiation sites were always in the interior of the specimens. Independent of the stress level, the initiation site was located at about the same depth(100200μm) below the surface, indicating maximum zone of tensile stress in these regions.
  • Non-destructive Evaluation of Cooling Rate and Toughness in Hot-work Tool Steel Quenched from Various Austenitization Temperature by Barkhausen Noise Analysis

    pp. 147-154

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    The purpose of this paper is to develop a non-destructive method for evaluating the cooling-rate (time for cooling from austenitization temperature (T) to 500°C (Ht)) generally in tempered specimens 0.4C-5Cr-Mo-V hot-work tool steel after quenching from a constant austenitization temperature within 1 0151 035°C. For this, the authors tried to employ Barkhausen Noise (BHN) signals which were induced during magnetization process. The BHN signals were measured on the surfaces of specimens, which were quenched with various T and Ht, and were tempered to adjust the hardness (H). The experimental results indicated that the total energy (Vp) of BHN signals was strongly related with microstructure which changed depending on T and Ht. These relationships could be successfully generalized as experimental expressions in the form of Ht=f(H, Vp, T). These results made it clear that non-destructive evaluation of Ht could be achieved generally by using a hybrid method combining the BHN method with an ordinary hardness test when specimens were austenitized at a constant temperature within 1 0151 035°C. The authors also confirmed the possibility of general estimation of Charpy impact values (Ch) through the generalized relationship between Ht, H, T and Ch when austenitization temperature was set at a constant temperature within 1 0151 035°C.
  • Impact Fatigue Properties of Carburized SCM415 Steels

    pp. 155-162

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    Fatigue and impact fatigue tests have been carried out on carburized steels with the case between 0.3 and 0.5 mm.
    S-Nf curves in impact fatigue tests show a knee transition point as well as in fatigue tests. The crack initiates from the surface of the specimen in the cycle life region lower than the transition point, while that initiates from the inside of the specimen in the cycle life region higher than the transition point in both fatigue and impact fatigue tests. The fish-eye fracture appears when the crack initiates from the inside of the specimen. The transition on S-Nf curve is attributed to the difference in such a crack initiation site. Striations have been observed in the fish-eye fracture area in both fatigue and impact fatigue tests. The crack growth rate calculated from the space of striations in impact fatigue tests is higher than that in fatigue ones. The cyclic impact loading has been found to accelerate the release of dislocations and damage of grain boundaries comparing with non-impact cyclic loading.
  • Quantitative Evaluation of Effects of Size and Shape of Artificially Introduced Alumina Inclusions on the Fatigue Strength of Ni-Cr-Mo Steel

    pp. 163-170

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    In 1963, W. E. DUCKWORTH and E. INESON investigated the effects of non-metallic inclusions on fatigue life of En 24 steel using specimens which contained artificially introduced spherical or angular alumina particles with various controlled sizes. Their tests showed a large scatter of fatigue lives of specimens tested under the same stress level depending on the size and location of the inclusion at fracture origin. Their report revealed typical complicated aspects of the effects of non-metallic inclusions on fatigue strength.
    In the present study, their complicated data were analyzed by the prediction equation which was proposed by MURAKAMI et al. and contains the Vickers hardness (HV) as the material parameter and the square root of projection area (√area) of inclusion as the geometrical parameter. The data can be clearly analyzed in a unified manner by MURAKAMI et al.'s equation. It is also shown that the shape of inclusions, spherical or angular, is not crucial factor of inclusion affecting fatigue strength.
  • Development of Low Carbon Equivalent and Normalized HT50 Steel with High N-V Addition

    pp. 171-178

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    For the decrease of Ceq. of normalized HT50 through the grain refining effect, the effect of reheating, rolling conditions and contents of V, N, Al on the mechanical properties of high N-V added steel has been investigated.
    The results obtained are as follows,
    1) The decrease of strength and the deterioration of toughness occur with higher content of Al in low temperature reheating. And the strength of as-rolled increases with higher V, N content within a limits of relation, V=3.64N (wt%). On the other hand, in normalized steel the adequate contents of V, N are 0.030.09%, 150200 ppm respectively. The toughness is improved with higher content of V and N, however the excess addition of V, N deteriorates the toughness in as-rolled steel.
    2) The mechanical properties of high V-N added steel are influenced by VN precipitates and austenite grain size is subject to VN through Gladman's relation. And the amount of VN precipitates is decided due to the precipitation in equilibrium with residual N after precipitation of AlN.
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  • X-ray Fluorescence Analysis of Titanium Alloys by Acid Dissolution/Glass Bead Technique

    pp. 179-186

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    The study of the X-ray fluorescence analysis of titanium alloys by acid dissolution/glass bead technique has been performed. Synthetic bead samples were used for standards, which were prepared from the standard solutions of each analyte. Interference by coexisting elements was corrected by the Fundamental Parameter (FP) method, or the theoretical alpha coefficients method. Analytical results of the standard reference materials of titanium alloys samples (chip form) by the both methods showed in good agreement with the certified values. The analytical values for Al, V, Cr, Fe, Zr, Mo and Sn in the practical β-type titanium alloys were also in good agreement with the chemical analytical values. The Relative Standard Deviations (RSDs) of analytical values with the both methods were within 1.5%. Accuracy (σd) with the FP-method using one titanium alloy sample as a standard showed a little worse than that with the theoretical alpha coefficients method, but the FP-method was adequate for a rapid multielement analysis for titanium alloys.

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