ISIJ International
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ONLINE ISSN: 1347-5460
PRINT ISSN: 0915-1559

ISIJ International Vol. 30 (1990), No. 9

  • Effective Utilization of Coal via Flash Pyrolysis

    pp. 687-698

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    DOI:10.2355/isijinternational.30.687

    Pyrolysis is a fundamental reaction in all coal conversion process: combustion, gasification and liquefaction in addition to coke-making process. Gaseous and liquid products evolved during pyrolysis have been used as fuels and chemical feedstocks. It is important to promote the production of these products for the effective utilization of coal. Attention has been paid to flash pyrolysis of coal for this purpose. In this review, the effects on pyrolysis process are examined. Coal type, carrier gas, pressure, heating rate, final temperature, and residence time in the secondary reactions all affect the product yields. The efforts are made to make clear how to control the product distribution based on the mechanism of coal pyrolysis. The features of coal flash hydropyrolysis processes including those developed and under development are also described.
  • Recent Development Status of Functionally Gradient Materials

    pp. 699-703

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    DOI:10.2355/isijinternational.30.699

    Recently, spaceplanes such as "Orient Express" projected by the United States are attracting attention as new space transportation media. In Japan also, the study for developing spaceplanes is recognized as one of the most influential programs among the various research and development projects.
    In the development of the spaceplane, it is most crucial to develop super heat-resistant materials because of the nature of the spaceplane. In 1987, the Science and Technology Agency (STA) organized a project team in order to develop super heat-resistant materials called "Functionally Gradient Materials (FGM)" under the special coordination funds for promoting science and technology. The FGM is quite a new material which can be obtained by continuous and proper control of micro-elements in conformance with the use environment, and which will be able to relax the thermal stress under high heat load.
    This thesis will show the outline of this project as well as the latest technological achievements which have been made by several research insitutes in the area of the development of the Functionally Gradient Materials.
  • Purification of Roasted Iron Oxide Product from Waste Pickling Liquor by Glass-ceramic Method

    pp. 704-713

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    DOI:10.2355/isijinternational.30.704

    The experiment has been carried out for the purification of α-Fe2O3 by the glass-ceramic method. After melting the roasted product of the waste pickling liquor with Na2O-B2O3 fluxes having the Na2O/B2O3 (mole ratio)=1/2-1/5, the glass samples obtained by rapid quenching crystallized at temperatures ranging from 550 to 1 000°C for 55 s to 24 h. The separation of the precipitated α-Fe2O3 from the flux was made by wet chemical treatment with water and dilute HCl solution, after which high purity and fine α-Fe2O3 crystals were obtained. The impurity contents, Fe yield, and crystal shape and size have been investigated as functions of crystalization time, temperature and flux compositions. In the experiment that the crystallized fine α-Fe2O3 particles were dissolved by dilute HCl solution in stepwise manner, the analysis of impurities in each stage shows that the contents of Si, Na, B, Ca and Al were enriched on the crystal surface.
  • The Surface Viscosities and the Foamines of Molten Oxides

    pp. 714-721

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    DOI:10.2355/isijinternational.30.714

    Viscosities of melts in the systems, Na2O-P2O5, BaO-B2O3, Na2O-B2O3 and Na2O-SiO2 were measured at 1000°C on the surface as well as in the bulk phase by using a modified rotating viscometer. For some melts, it was found that the viscosity on the surfaces is higher than that in the bulk phase. The highly viscous layer on the surface suggests that concentration of surface active component such as B2O3 in the system BaO-B2O3 is higher on the surface than in the bulk phase. Foaminess of the melts was also measured. It is concluded that higher viscosity of the melt itself is important, but not enough to stabilize the foam, and higher surface tension depression by the melt composition is also required.
  • Relation between Sulfur Pressure and Sticking of Fine Iron Ores in Fluidized Bed Reduction

    pp. 722-730

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    DOI:10.2355/isijinternational.30.722

    Fourteen kinds of iron ore fines (0.015-0.021 cm diameter) were reduced to iron in a laboratory batch fluidized bed with a 90%CO-10%CO2 mixture (flow rate: 8 times the minimum fluidization velocity Umf) at 700-900°C to investigate the relation between sticking behavior and sulfur activity in gas phase of bed during metallization (aS), which could be evaluated from chemical analysis of sulfur species in exhausted gas, relative to iron/iron sulfide equilibrium.
    Values of aS obtained in all of tests were in the range of 0.01-1. The tests showing middle sulfur activities around 0.1, fell into sticking state soon after initial metallization, accompanied with long iron whiskers at higher temperatures. The tests showing activities other than the above conditions, induced short iron whiskers and porous or plain irons, indicating fluidized state until higher reduction degrees at lower temperatures. These temperature and sulfur activity dependences of product morphologies, which were in nearly agreement with authors' previous researches about abnormal swelling during reduction of iron oxide pellets prepared from reagent, corresponded to a sticking tendency of bed. These results give one reasonable idea by which the ore kind dependence of sticking can be interpreted.
  • The Modeling of Gas-bubble Driven Circulations Systems

    pp. 731-739

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    DOI:10.2355/isijinternational.30.731

    A mathematical model is presented of the turbulent recirculating two-phase flow in gas-stirred systems. Conservation equations are solved for each phase variables and these are connected through interaction parameters. Allowance is made both for the direct influence of bubble transport on the turbulence field and the additional generation of turbulence energy at the liquid/gas interphase. In addition, the plume shape is a direct result of the computation rather than being prescribed a priori. Computed flowfields are presented for both air-water and nitrogen-steel systems. The air-water results compare well with established measurements of gas fraction and mean velocities. The steel system results seem to suggest that gas plumes in metals may be narrower than in water.
  • Desiliconization Reaction of Pig Iron with High FeO Containing Blast Furnace Slag under Pressurized and Coke-coexisting Condition

    pp. 740-747

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    DOI:10.2355/isijinternational.30.740

    For the quantitative investigation of the desiliconization inside blast furnace by the iron oxide injection through tuyeres, fundamental researches on the desiliconization reaction by high FeO containing slag under pressurized and coke-coexisting condition were performed by the use of a pressurized high frequency furnace. Under coke-coexisting condition, FeO not only reacts with silicon in hot metal but also simultaneously reacts with coke through the direct reduction reaction and the decrease of temperature and the increase of total pressure accelerates the desiliconization reaction through suppression of the direct reduction reaction. The increase of the amount of slag and the increase of slag basicity result in the enhancement of the desiliconization.
    Based on the results of fundamental researches, an unsteady state desiliconization mathematical model was developed with consideration of the coupled reactions of desiliconization and direct reduction and successively applied to the quantitative analysis of the coupled reactions.
    A test operation with dry iron ore dust was performed under almost constant pig iron temperature at Wakayama No. 4 blast furnace. A decrease of silicon content of 0.09% was obtained by the iron ore injection rate of 32 kg/pt without carryover of the injected iron ore to the hearth. Accordingly, the desiliconization by the iron ore injection was verified in the commercial test operation.
    x

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  • The Cold Model Study on the Decarburization Rate in Oxygen Steelmaking Processes by CO2/KOH System

    pp. 748-755

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    DOI:10.2355/isijinternational.30.748

    The model experiments using KOH solution/air-CO2 mixture gas jet are conducted to understand the effects of blowing conditions on reacting interfacial area in simulation of decarburization in the oxygen steelmaking. The fast pseudo-1st-order reaction regime is adopted by the chemical absorption theory to observe gas/liquid interfacial area which is the most important controlling parameter in the decarburization kinetics of high carbon regime. The result shows that the reacting interfacial area is greatly dependent on injecting gas flow rate, nozzle diameter, injection scheme and aspect ratio of the reacting volume. It is deduced that these effects are closely related with physical aspects of two-phase jet structure. An intuitive model for the jet effect on the reactivity is suggested.
  • Spray Deposition Method and Its Application to the Production of Mill Rolls

    pp. 756-763

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    DOI:10.2355/isijinternational.30.756

    Rapid solidification processing generally results in fine grained and macrosegregation free microstructures and improves hot-workability of highly-alloyed metals (e.g., superalloys and high alloy steels).
    The Osprey Process is a technology capable of producing rapidly solidified materials in thick sections. The Process also provides a means of producing dense preforms in one step directly from liquid metal by an integrated atomisation/deposition operation. Consequently, the Process retains most of advantages of powder metallurgy methods while eliminating the major disadvantages resulting from multi-stage processing (i.e., powder production, sizing, compaction and sintering) which often leads to high cost and oxide contamination in the final product.
    In the present investigation, the Osprey Process has been applied satisfactorily to mill rolls.
    The results indicate that:
    (1) A fine grain size is obtained by controlling operational parameters;
    (2) The as-sprayed preform exhibits higher mechanical properties compared with conventional cast rolls;
    (3) In experimental tests the amount of wear of Osprey products is 1/2 to 1/6 of conventional cast material; and
    (4) The life of Osprey rolls under service in a wire-rod mill exceeded that of conventional ones by two to three times.
    x

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  • Metallurgical Investigation for Producing Deep-drawable Continuously Annealed Al-killed Sheet Steels through Low-temperature Coiling

    pp. 764-772

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    DOI:10.2355/isijinternational.30.764

    Metallurgical factors for realizing the low temperature coiling at around 650°C of hot-rolled bands have been investigated in producing deep-drawable continuously annealed Al-killed sheet steels with a high yield rate. The following conditions are proposed: the control of the chemical compositions as i) 0.01% < C ≤ 0.02%, ii) Mn ≤ 0.15% and iii) Al ≥ 0.05%, and the choice of iv) low slab reheating temperatures below 1150°C. Conditions i) and ii) contribute to the coarsening of cementites in hot-rolled bands and to the decrease in the amount of Mn-C complex during annealing, whilst condition iii) contributes to the promotion of AIN precipitation. These are considered to play a significant role in improving the r-value of the annealed sheets. Furthermore condition iv) not only has an effect on promoting grain growth due to the coarsening of precipitates in hot-rolled bands, but also contributes to the prevention of hot-shortness caused by the segregation of S in austenite grain boundaries. A mechanism concerning the influence of the C and Mn contents on cementite coarsening in the hot-rolled bands is discussed, and it is concluded that the growth rate of cementite particles during coiling was retarded by the presence of Mn. Moreover the metallurgical meaning for obtaining the excellent r-values is also rationalized.
    A mill test based on the knowledge obtained in laboratory examination with a coiling temperature of 650°C resulted in a desired level of high r-value and less variation through a whole length of finished coil.
    x

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  • Effects of Chemical Composition on the Heat-treatment Response of Ti-15V-3Cr-3Sn-3Al Based Beta Titanium Alloys

    pp. 773-779

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    DOI:10.2355/isijinternational.30.773

    Ti-15-3(Ti-15V-3Cr-3Sn-3Al) and two other alloys which contained less V and Cr and more Al than Ti-15-3 were studied to investigate the effects of alloying elements, Al, V and Cr, on beta transus temperature, aging behavior and mechanical properties. The variation in composition causes a little increase in the beta transus temperature and the nose temperature. At full-aged condition, it produces a slight increase in hardness and large increase in alpha phase volume fraction. Among the effects, it is notable that the variation in composition produces rapid aging to full-aged condition, but it does not alter the strength-ductility relationship in full-aged condition. Hence, in Ti-15-3, the adjustment of composition as adopted in this study can widen 'processing window' to attain the required properties.
  • Solid Solution Hardening in Ternary Ni-Y(Y: Co, Pd, Fe)-Nb Alloys

    pp. 780-785

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    DOI:10.2355/isijinternational.30.780

    Solid solution hardening in Ni-Co, Ni-Pd and Ni-Fe binary matrix alloys is investigated mainly by the addition of Nb and the results are compared with that in nickel. It is shown that the rate of solid solution hardening per 1at% of Nb is larger in the following order; Ni-Co, Ni-Fe>Ni>Ni-Pd. Since there is no appreciable difference in the size misfit parameter of Nb in these alloy systems, such difference cannot be interpreted solely by the elastic interaction theory. To be noted is the fact that the limit of solid solubility of Nb would be reduced in Ni-Co and Ni-Fe alloys but be increased in Ni-Pd alloy both as compared to that in Ni. Then the limit of solid solubility is shown to be well correlated with the magnitude of the interaction parameter between the solute and the solvent. If it is large negative, there should be a strong tendency for the solution to have a short range order and if it is large positive the solute atoms should tend to form clusters. In relation to the limit of solid solubility, it is suggested that in Ni-Co and Ni-Fe alloys dislocations would no more be interacting with discrete single solutes distributed randomly but with some kind of solute aggregates to cause the extra hardening as compared to Ni.
  • X-ray Fluorescence Analysis of Superconductor YBa2Cu3O7-δ by Glass Bead-FP Method

    pp. 786-793

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    DOI:10.2355/isijinternational.30.786

    In the accurate elemental analysis of ceramic powders by X-ray fluorescence spectrometry with few or no available standards, the glass bead technique combined with the fundamental parameter (FP) method has been found to be suitable. As an example of ceramic powder analysis, we determined the amounts of Y2O3, BaO, and CuO contained in a superconductor YBa2Cu3O7-δ with this combined method.
    The results were as follows:
    (1) Satisfactory glass beads with near-infinite thickness to both incident and fluorescent X-rays were found to be prepared from 10 g of Na2B4O7, 1 g of YBa2Cu3O7-δ, and 0.20 g of KI.
    (2) Absorption enhancement effects for YKα, BaKα, and CuKα as below were taken into account in the analysis. YKα is more absorbed by substituting Y2O3 in the mixed reagents (Y2O3-BaO-CuO) with either BaO or CuO. BaKα is enhanced or a little more absorbed depending on the substitution of BaO in the mixed reagents with CuO or Y2O3. CuKα is more absorbed or a little enhanced depending on the substitution of CuO in the mixed reagents with BaO or Y2O3.
    (3) The amounts of Y2O3, BaO, and CuO in the superconductor were determined with the good accuracies (σd's) of 0.11, 0.18, and 0.19wt%, respectively by this combined method.

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