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

Tetsu-to-Hagané Vol. 71 (1985), No. 6

  • Iron Ore Resources and Steel Making Industry in China

    pp. 627-632

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  • Mineral Processing and Refining of Rare Earth Elements

    pp. 633-644

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  • Recent Developments in Electrometallurgy

    pp. 645-653

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  • Problems on Fracture Toughness Evaluation and Role of Instrumented Charpy Test

    pp. 654-660

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  • Nuclear Power Generation and Nuclear Fuel

    pp. 661-671

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  • Reduction Behavior of Wustite Pellets with Different Levels of Porosity by Hydrogen Containing Hydrogen Sulphide at Elevated Temperatures

    pp. 672-679

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    In order to understand the effect of sulphur in reducing gas on the reduction behavior of iron oxides, the reduction experiments were conducted in H2-H2S mixtures with various sulphur activities at 1 000 and 1 200°C.
    Macroscopic reduction patterns of pure wustite pellets can be divided into seven types, depending on the porosity of pellets and the activity of sulphur in the gas. This classification is slightly modified by the addition of MgO and CaO.
    The reduction of pellets with low porosity is retarded greatly due to the formation of iron-oxysulphide liquid. The retardation of reduction does not occur with pellets of high porosity even under the high sulphur activity to form FeS. However, the reduction is retarded provided that the sufficient amount of the liquid to fill up the pores is formed.
    The activity of sulphur in equilibrium under iron, wustite and iron-oxysulphide liquid was determined experimentally. MgO in wustite raises the sulphur activity and CaO lowers it.
    Sulphur in the gas without the formation of sulphides causes the topochemical reduction pattern, independently of the presence of foreign oxides.
  • Analysis of Reduction Kinetics of Dense Wustite Foils in CO-H2 Gas Mixtures by Mathematical Model with Water-gas Shift Reaction

    pp. 680-686

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    A mathematical model for the kinetics of reduction of wustite with CO-H2 gas mixtures was developed based on the unreacted-core model. In this model, (i) the water-gas shift reaction with reduced iron as a catalyst was taken into consideration, and (ii) the diffusion rates of gases through the gas-film and the product iron layer were evaluated from the STEFAN-MAXWELL equations for multi-component diffusion.
    Reduction experiments of dense wustite foils with CO-H2 gas mixtures were carried out at 1 000°C and the data obtained were analyzed by the above-mentioned mathematical model with the following results.
    (i) The effect of the water-gas shift reaction on the reduction kinetics was negligibly small.
    (ii) Relation between the reduction rate and gas composition showed negative deviation from the additivity, i.e. a linear combination of the rates of reduction with the pure component gases. It was attributed to the predominant contribution to the overall reaction resistance of the diffusional resistances through the gas-film and the product iron layer.
  • タカイタカイ/高炉屋は獣医でもあるのか?/わが国製鋼メーカーのリターン屑発生率/「太平洋の時代を迎えて」

    pp. 686-686,692

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  • Thermodynamics of Phosphate and Phosphide in BaO-BaF2 Melts

    pp. 687-692

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    The thermodynamics of phosphate and phosphide in BaO-BaF2 melts was studied by equilibrating the melts in a graphite boat with CO-Ar mixtures and Ag-P alloys between 1 200°C and 1 450°C.
    The concentration dependence of both constituents on the partial pressure of phosphorus and oxygen, the melt composition and temperature was determined.
    Comparing with the CaO-CaF2 system previously reported by the authors, BaO-BaF2 melts were found to have a larger capacity for phosphate by an order of magnitude but nearly the same one for phosphide.
    It is concluded that BaO-BaF2 melts are very effective in removing phosphorus from other systems under either oxidizing or reducing conditions.
    x

    Readers Who Read This Article Also Read

    1. Oxidation Dephosphorising Method of Molten Steel Containing Chromium Tetsu-to-Hagané Vol.74(1988), No.2
    2. Phosphorus Distribution between Mn-Si Melts and CaO-SiO2-MnO-CaF2 Slags Tetsu-to-Hagané Vol.74(1988), No.10
  • Phosphorus Distribution between CaO-CaF2-SiO2 Melts Saturated with Solid CaO Compounds and Carbon-saturated Iron

    pp. 693-699

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    The information of thermodynamic properties of phosphorus in lime bearing slags at low temperatures is required in connection with the recent progress of hot metal treatment.
    In the present study, the equilibrium distribution ratio of phosphorus (LP) between CaO-CaF2-SiO2 melts saturated with CaO, 3CaO·SiO2 and/or 2CaO·SiO2 and carbon-saturated iron was measured under CO atmosphere at temperatures ranging from 1 200 to 1 400°C, keeping in mind that the industrial flux always contains some undissolved solids.
    The results are summerized as follows :
    (1) LP increases with increasing CaO content and has a maximum when the slag is saturated simultaneously with CaO and 3CaO·SiO2.
    (2) Phosphate capacity was confirmed to be independent of the oxygen partial pressure by using ironcarbon melts equilibrated with austenite and CO at 1 300°C. The phosphate capacity in basic regions of this system is much greater than other lime bearing slags.
    (3) CaF2 is more effective for dephosphorization than CaCl2, probably because the interactions between fluorine and phosphorus and between fluorine and calcium are stronger than those between chlorine and phosphorus and between chlorine and calcium, respectively.
    (4) LP increases significantly with a small Na2O addition to the CaO-CaF2-SiO2 system. This result indicates that the costly soda ash treatment can be replaced by using lime based fluxes containing a little soda ash.
    x

    Readers Who Read This Article Also Read

    1. Rate of Dephosphorization of Liquid Iron by the Flux of Na2O-SiO2 System Tetsu-to-Hagané Vol.71(1985), No.1
  • Dephosphorization of High Chromium Molten Iron by Na2O-SiO2-NaF Flux

    pp. 700-704

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    Experiments of the dephosphorization of molten iron containing chromium (≤27 wt%), carbon (≤6 wt%), and phosphorus (0.1, 0.04 wt%) by the use of the flux of Na2O-SiO2-NaF system were carried out in the temperature range from 1 300°C to 1 600°C.
    Effects of flux composition, carbon and chromium content in molten iron and temperature on the dephosphorization were made clear.
    Relations between phosphorus and chromium distribution ratios obtained at the end of runs and carbon content in molten iron were also investigated. These distribution ratios depend on the carbon content strongly.
  • Decreasing of Inclusions by Adhesion Separation with Filter

    pp. 705-711

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    To separate inclusions from molten steel, a new method by filtration which is different from conventional ones based on floating-out of inclusions was investigated. Since filters with pores smaller than the diameter of inclusion are considered not to be applicable to molten steel, ceramic filters with many small holes were used with expectation of getting inclusions adhered on them.
    As the first step the influences of filter shape design and deoxidation of steel on the filtration of inclusions were investigated.
    Results obtained are summarized as follows:
    (1) The inclusions filtered are only of alumina type and therefore this filter is effective for removal of inclusion in aluminum killed steel.
    (2) Inclusions adhere at first on the edge of a filter pore where the flow of molten steel changes and grow to cover on the top surface of the filter and fill up the inner part of the pore. When the layer of adhered inclusions on the filter becomes thick, the molten steel can not go through the filter.
    (3) From the reason mention above, the increase of thickness of the filter dose not improve removal of inclusions.
  • Rolling Conditions for Annihilation of Micro Porosities and Development of Center-portion Heavy Reduction Rolling

    pp. 712-718

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    The authors investigated the method to get the sound heavy gauge plates only by rolling process, and developed the Low-speed Heavy Reduction Rolling process, the purpose of which was to secure the necessary temperature, time and compressive stress for annihilating micro porosities. Furthermore, taking notice that most of micro porosities are distributed in the about 50-60% region of mid-width of ingots, they have developed the Center-portion Heavy Reduction Rolling process which reduce only the high density area of micro porosities partially by the low speed and heavy reduction rolling. In such a partial rolling, the compressive stress in midthickness increases notably as a result of the binding force caused by the un-rolled edge parts and an increase in the reduction amount per pass.
    It would be possible to manufacture the sound heavy gauge plates stably from the conventional ingots by the application of this developed rolling process.
  • Effect of Atomization Conditions on Microstructure of Ni-base Superalloy Powder

    pp. 719-726

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    Many kinds of superalloys are widely being employed as materials for aircrafts, but the segregation is generally apt to occur in cast alloys because of bearing many alloying elements. Accordingly, the powder metallurgy technique has lately been available for the practical production of turbine disc etc. In order to sufficiently apply the improved properties of material, it is necessary to make microstructure of powder as fine as possible.
    The authors developed liquefied helium cooling centrifugal atomization technique and made a trial on a fine crystallization of particles by rapid solidification of melt in the process of the atomization. An investigation was made about the various atomization factors which widely control the secondary dendrite arm spacing, SII, as a measure of microstructure.
    The following results were obtained.
    (1) The most frequent diameter of powder, d(μm), is given as the following equation;
    d=4.0×105×R-0.84
    where R represents the revolution speed of the disc (rpm).
    (2) The following means are effective to make the microstructure finer.
    a) The particle size is smaller.
    b) The thermal conductivity of the cooling medium gas is higher.
    c) The gas pressure of the cooling medium is higher.
    d) The gas temperature of the cooling medium is lower.
    e) The introducing rate of the cooling medium is higher.
    f) The diameter of the atomizing disc is greater and its revolution speed is higher.
  • Grain Boundary Reaction and Creep Rupture Properties of a Co-base Superalloy HS-21

    pp. 727-734

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    The effect of solution and aging treatment on the grain boundary reaction (GBR) as well as on the general precipitation in the interior of grain (GP) was investigated for Co-base superalloy HS-21. The GBR occurred during furnace-cooling after solution heating, and the maximum amount of it was obtained in the temperature range from 1 523 K to 1 548 K. The GBR that occurred during aging was considerably influenced by the cooling procedure after solution heating. A large amount of GBR was observed in the specimen directly quenched. In the air-cooled specimen, the amount of GBR was less than one half of that observed in the directly quenched one, while very few amount of it was observed in the water-quenched one. The extent of GP that occurred during aging was also affected by cooling procedure, and the maximum amount of it was obtained in the water-quenched one.
    Creep rupture life was longer on the specimen with a small amount of GBR with GP. The improvement of rupture life resulted from the retardation of grain boundary sliding by the zigzag grain boundary owing to the GBR and by the increase of strength in the interior of grain due to the GP.
  • High-speed Tool Steel Having Recrystallized Hyperfine Grains and Its Application

    pp. 735-742

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    There is a limit to grain refinement of high-speed tool steel by usual recrystallization process at the austenite region even after working with a large reduction.
    In a series of our experiments, however, it was shown that in steel specimens processed through preforming and then solution treatment, the grain size after recrystallization was extremely refined. Tests carried out in a range of commercial high-speed tool steels quantitatively clarified the effect of preform reduction, solution temperature, reduction for recrystallization and annealing temperature on the final grain sizes.
    Furthermore, it was shown that high-speed tool steel with fine grain sizes was possible to become superplastic and its total elongation exceeded 300% over a suitable range of temperatures and strain rates.
  • Influence of Stacking Fault Energy on Plastic Flow of Cr-Ni Austenitic Stainless Steels

    pp. 743-748

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    A series of Cr-Ni austenitic stainless steels whose stacking fault energy (SFE) was varied systematically, were deformed by tension at the condition of temperature, 291 and 473 K, and strain rate range from 10-5 to 10-3 s-1. The various plastic flow parameters such as strain hardening exponent, COTTRELL-STOKES ratio, activation volume and etc., were determined through usual tensile test and temperature or strain rate change tests. The measurement of magnetic permeability was also carried out continuously during the tensile test in order to check the occurrence of stress induced martensite.
    Although the dependence of SFE on yield stress was not so clear at room temperature (291 K), ultimate tensile stress (UTS) and the strain hardening exponent apparently depended upon SFE, namely, both the UTS and the strain hardening exponent decreased with increasing SFE. The COTTRELL-STOKES ratio determined by the temperature change tests was an appropriate measure to check the relative contribution of thermal and athermal components of flow stress. According to the linear increase of the ratio with SFE, it was clarified that the higher the SFE, the larger became the contribution ratio of the athermal component. The activation volume measured by the strain rate change tests, decreased with increasing SFE, and the degree of its variation with strain was larger for higher SFE steels.
  • Corrosion Resistance of Organic Film Coated, Metal-organic Composite Coated and Some Zinc Coated Steel Sheets

    pp. 749-755

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    Corrosion behavior of organic film coated steel sheet(ZM), which might be applied to automobile bodies, has been compared with that of metal-organic composite coated steel sheet(WM) and some kinds of zinc coated sheets; (galvanized, galvanealed and zinc-nickel alloy coated shects).
    The results obtained are as follows:
    (1) Unpainted specimens of ZM and WM show excellent corrosion resistance in cyclic corrosion test (C.C.T.), where a s cathodic E.D. painted specimen of ZM with cross scribes seems to have almost as less corrosion resistance as cold rolled sheet.
    (2) 3 coat painted specimen of ZM with cross scribes has also less corrosion resistance than zinc coated sheets in salt spray and weathering test. This shows little sacrificial corrosion preventive effect of zinc powder existing in organic film.
    (3) Convex part of ZM exhibits better appearance, but larger perforation than zinc coated sheets after 22 weeks C.C.T., probably because of the surface crack of organic layer.
    (4) WM seems to have excellent appearance and less perforation than the others especially in convex part.
  • Chip-disposability and Tool Wear in Ferritic Steels Mixed with Martensite

    pp. 756-763

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    The improvement of chip-disposability has a primary importance in the automation of machining process and the use of unmanned machine tool.
    Chip-disposability and tool wear during turning of low alloy steels having ferrite and martensite phases were examined. The experimental results showed the chip-disposability was remarkably improved in the steels mixed with martensite, compared with the spheroidized or normalized steels.
    In steels which were mixed with martensite and had the hardness of HV 200350, chips in the high cutting speed region were broken below one curl. The influence of martensite phase on the chip-disposability was discussed through the observation of the microstructure and surface shape of chips.
    The wear of hard metal tool in the cutting of steel mixed with martensite tempered at about 300°C was similar to that of the spheroidized steel, and the tool life time of high speed steel tool for the steel tempered above 400°C was considerably longer than that for the steel tempered at 300°C. When the cutting was done with high speeds using a cermet tool, the tool wear for the steel mixed with martensite and not tempered was larger than that for the normalized steel.
  • 抄録

    pp. 769-771

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