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

Tetsu-to-Hagané Vol. 96 (2010), No. 12

  • Development of Thermophysical Property Measurement for Liquid Fe Using Noncontact Laser Modulation Calorimetry

    pp. 673-682

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    DOI:10.2355/tetsutohagane.96.673

    Newly developed noncontact modulation laser calorimetry has enabled us to measure accurate thermophysical properties such as thermal conductivity and heat capacity of high temperature liquid metals with suppressing chemical reactions and convections. However, in spite of the demand for accurate thermophysical properties as input parameters in precise numerical simulation for casting and welding processes, it is still difficult to measure those of liquid iron (Fe). The difficulty is caused by the high density and electrical resistivity of liquid Fe. In this study we designed a new levitation coil having high lifting force with moderate heating for liquid Fe. Furthermore, a superconducting magnet, which has a maximum dc magnetic field of 10 T, was equipped to the measurement system to suppress the convection in the liquid Fe. The isobaric molar heat capacity of liquid Fe was successfully measured at lower dc magnetic field (3 and 4 T). This can be explained by the accomplishment of the semi-adiabatic condition caused by the higher thermal conductance of the convection. The isobaric molar heat capacity of liquid Fe was determined as follows; cp=45.5±4.1 J·mol−1·K−1 [1816–1992K]. On the other hand, the apparent thermal conductivity of liquid Fe decreased with increasing dc magnetic field, and then finally converged to be 38.7±2.5 W·m−1·K−1 [1794–2050 K] above 9 T due to the suppression of convection.
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  • Effect of Raw Materials on Reaction Behavior of Carbon Iron Composite

    pp. 683-690

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    DOI:10.2355/tetsutohagane.96.683

    In these years, the development of innovative energy saving technologies for climate change is strongly desired, and low reducing agent ratio (RAR) operation in the blast furnace is required to reduce CO2 emission in ironmaking. As a mean of realizing low RAR operation, the development of an innovative raw material “Carbon Iron Composite (CIC)” for satisfying both high coke reactivity and iron ore reduction is thought to be useful. Carbon Iron Composite is produced by mixing the non-or slightly caking coal and low-grade iron ore and briquetting, followed by carbonization of the briquetted materials. Carbon Iron Composite having both high strength and high reactivity was successfully produced at the blending ratio of iron ore of 30 mass%. Investigation of CO2 reactivity of CIC at the simulated blast furnace condition revealed that beginning temperature of CO2 reaction of CIC is lower than the temperature of conventional coke. Especially, CIC made from high volatile matter coal and porous iron ore has high reactivity and high strength after CO2 reaction.
  • In-situ Observation of Martensite Transformation and Retained Austenite in Supermartensitic Stainless Steel

    pp. 691-697

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    DOI:10.2355/tetsutohagane.96.691

    Martensite transformation of supermartensitic stainless steel during cooling was in-situ observed by using high temperature laser scanning confocal microscopy and X-ray diffraction by Synchrotron radiation. The crystallography of martensite and austenite structure were analyzed which X-ray diffraction spots and electron back scattered diffraction patterns (EBSD). From the test results it could be concluded that the austenite phase is accommodated by rotation less that 3 degree of the crystallite when the martensite transformation is occurred. X-Ray diffraction integration strength of austenite was influenced by the transformation stress immediately after the martensite transformation. We consider that the diffracting power of parent phase of austenite increase during martensitie transformation, because the compression stress is accommodated, and the defect is introduced, resulting in the mosaic structure.
  • Serial Batch Elution of Electric Arc Furnace Oxidizing Slag Discharged from Normal Steelmaking Process into Fresh Water

    pp. 698-705

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    DOI:10.2355/tetsutohagane.96.698

    The serial batch leaching test of an electronic arc furnace oxidizing slag was performed on the basis of JIS K 0058-1 to investigate the safety of the slag and to clarify the elution mechanism. The slag which was discharged at the time of refining of normal steel was used for this experiment. The slag was dissolved in water whose initial pH was 6.0. After that, the slag was naturally dried. This operation was performed 12 times successively.
    The dissolution behaviors of Ca and Mg were expressed by the parabolic law. That of Si was expressed by the linear law. The dissolutions of them from the slag were controlled by the diffusion through pore and the surface layer through the surface layer where compositions of FeO and Al2O3 were high. Generally, the dissolve concentrations decreased with the increase in the number of the elution times. The environmentally regulated substances were not detected or less than the levels of the environmental quality standards for soil. Ba, Mn, Mo, K, Na, Sr and W were detected as minor element except for the environmentally regulated elements. Generally, the detected environmentally regulated substances and the other minor elements decreased with the number of the elution times. During the elution of the slag, the pH of the aqueous solution steeply increased initially, and it decreased afterwards. The pH decreased with the increase in the number of the elution times.
  • Prediction Model of Global Demand for Iron Source by Utility of Stock Hypothesis

    pp. 706-713

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    DOI:10.2355/tetsutohagane.96.706

    The Utility of Stock hypothesis, which assumes that an in-use stock of constructional material is a function of GDP, was formulated and a clear correlation between the world steel stock and the world GDP led to the estimation that the world demand for iron ore (primary iron) depends not on the volume of GDP but on the variation of GDP, as already reported. It also became clear that the flow of primary iron has the controlling effect on the world production of crude steel. In this study, the prediction power of the Utility of Stock hypothesis is verified. Based on the verification, the global demand for iron source until 2050 is projected by deciding a world 1-region model.
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  • Swirl Motion of a Bubbling Jet in a Cylindrical Bath with an Immersion Cylinder

    pp. 714-719

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    DOI:10.2355/tetsutohagane.96.714

    The deep-water wave type of swirl motion of a bubbling jet appearing in a cylindrical bath agitated by bottom gas injection is promising to elevate mixing efficiency significantly in the steelmaking industry. At the same time, it affects the erosion of the refractory of the reactor and causes oscillation of the reactor. An understanding of the swirl motion observed under different conditions therefore is of practical importance. Considering these circumstances, an effect of a top lance on the swirl motion is investigated in this study based on water model experiments. A hollow cylinder which is a model for the top lance is slightly immersed in a water bath contained in a cylindrical vessel. The cylinder and the vessel are concentrically placed. Air is injected through a centered bottom nozzle into the bath to generate the swirl motion. The occurrence condition of the swirl motion is revealed and empirical equations are proposed for describing the condition. Empirical equations are proposed also for the basic characteristics of the swirl motion such as the period, amplitude, starting time, and damping time.

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