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

Tetsu-to-Hagané Vol. 102 (2016), No. 11

  • A Water Model Experiment on Gas Absorption during Tapping

    pp. 607-613

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    DOI:10.2355/tetsutohagane.TETSU-2016-013

    Gas absorption phenomena during tapping from converter to ladle were studied by water model experiments. Gas absorption rate to molten steel was simulated by oxygen-water system and changes of dissolved oxygen in the vessels were continuously observed. In this study, effects of nozzle diameter and tapping height on volumetric coefficient for gas absorption rate, AkO, were investigated and gas absorption phenomena were discussed.Changes of water amount in both upper and lower vessels were calculated with Torricelli’s law and changes of DO in lower vessel were estimated by the kinetics formula considering dilution. Maximum AkO was found in the early stage of tapping. AkO after the middle stage of tapping were in good agreement with reported values. Changes of AkO during tapping could be classified into 3 regions, I: Growth, II: Transition, III: Steady. The growth of plunge pool was also studied by estimating the depth of penetration of bubbles, Hp, during tapping and was associated to gas absorption phenomena. As a result, strong relationship between the gas absorption phenomena and the growth of plunge pool was confirmed. The similar behavior was found in various initial tapping height and nozzle diameter settings by estimating the experimental results with Hp_obs./Hp_calc. and AkO_obs./AkO_calc.. By using this similarity, experimental results could be reproduced by the empirical formula.
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    Readers Who Read This Article Also Read

    1. Dynamic Material Flow Analysis of Stainless Steels in Japan Tetsu-to-Hagané Vol.102(2016), No.11
    2. Creep Damage Evaluation of Heat Resistant Ferritic Stainless Steel by Hydrogen Thermal Desorption Analysis Tetsu-to-Hagané Vol.102(2016), No.11
    3. Thermodynamic Properties of the CaO–AlO1.5–CeO1.5 System ISIJ International Vol.56(2016), No.11
  • Development of Control Techniques for Mixing Small Coke at Bell-less Top Blast Furnace

    pp. 614-622

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    DOI:10.2355/tetsutohagane.TETSU-2016-041

    Increased gas utilization and improved permeability have been desired in order to achieve low RAR (Reducing Agent Rate) operation of blast furnace. Coke mixed charging in the ore layer is one effective measure for realizing these improvements. A burden distribution control technique for mixing small coke at a blast furnace with a parallel type and center feed type bell-less top were developed and investigated in an experiment with a scale model of an actual blast furnace at JFE Steel. The scale model consists of an ore bin, a coke bin, a surge hopper, belt conveyers, a bell-less top and a model furnace to simulate the charging system of the actual blast furnace. The mixed coke ratio at the furnace top was controlled by the discharge pattern of mixed small coke and ore, and mixing position. The optimum patterns were founded to discharge the small coke from the coke bin after the ore discharged from ore bin in center feed bell-less top, and to discharge the small coke on the ore at front of quarter part overlapped in parallel type bell-less top. These patterns were applied to the actual blast furnace, and the improvement of permeability in a furnace was confirmed by the effect of increase the mixed small coke yield into ore layer.
  • Determination of Solid Solubility and Quantitative Analysis of Free-Lime in Steel Slag by Powder X-ray Diffraction

    pp. 623-629

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    DOI:10.2355/tetsutohagane.TETSU-2016-044

    X-ray diffraction analysis was performed on steel slag samples, and free-lime, which tend to cause hydration and result in swollen slags, were quantitatively analyzed. Simple CaO and solid solutions in the slag samples that correspond to free-lime could be distinguished from each other from the angles of 200 reflections. The contents of divalent-metal oxides that dissolved in CaO forming solid solution were determined from the lattice parameters calculated from the angles of reflection. The values of the contents were sufficiently large for the slags analyzed in this study to suppress the hydration reaction of the solid solution. Quantities of the free-lime were analyzed by the standard addition method. The reflection intensities of slag samples, to which different amounts of pure CaO were added, were measured, and the contents of the simple CaO and solid solution in the slags of each sample were determined separately.
  • Creep Damage Evaluation of Heat Resistant Ferritic Stainless Steel by Hydrogen Thermal Desorption Analysis

    pp. 630-637

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    DOI:10.2355/tetsutohagane.TETSU-2016-047

    The change in hydrogen thermal desorption characteristic of heat resistant ferritic stainless steel (18Cr-2.5Si steel) due to creep was investigated to examine the applicability of hydrogen as a tracer for creep damage evaluation. The hydrogen charging into the interrupted creep specimens with a wide variety of damage degrees was conducted by means of cathodic electrolysis. Next, the hydrogen-charged samples were subjected to the thermal desorption analysis (TDA) for measuring the hydrogen evolution curve. The experimental results revealed that the overall shape of curve varied with creep depending on the test conditions. However, this change in desorption characteristic reflected not only the creep damage but also the microstructural changes such as precipitation/coarsening of NbC and change in dislocation density. In an attempt to separate their effects and extract the former alone, the measured curve was decomposed into several curves by comparison with the curves of thermally aged and solution treated steels. As a result, the amount of desorbed hydrogen, which was likely to be associated with defects like a void and/or vacancy cluster, was found to increase with increasing creep damage, and it was successfully arranged with the parameter derived based on the creep void growth’s law.
  • Effect of Annealing Temperature and Coiling Temperature on r-value of Nb and B-added Extra Low-carbon Steel for Welded Cans

    pp. 638-645

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    DOI:10.2355/tetsutohagane.TETSU-2016-024

    When the welded can body is expanded in the pail can manufacturing,it shrinks in the direction of can height.The change of height of can is influenced by r-value.The effect of annealing temperature and coiling temperature on the r-value of niobium (Nb) and boron (B) combined added extra low-carbon steel was investigated by using commercial steels.Ferrite grain size of annealed sheet decreased with the decrease of annealing temperature. At the same time,the orientation density of {001} <110> increased and the r90°-value decreased.The behavior of the decrease of r90°-value was dependent on the coiling temperature of hot-rolled sheet. The r90°-value decreased rapidly for low coiling temperature as the annealing temperature decreased.
  • Effect of Ductility on Load/Stress Conversion Coefficient of Small Punch Creep Test for Ni-Base Alloys

    pp. 646-652

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    DOI:10.2355/tetsutohagane.TETSU-2016-033

    Remaining-life assessment of high temperature components using the small punch (SP) creep testing technique necessitates the evaluation of SP load (F)/uniaxial stress (σ) conversion coefficient, F/σ, obtained by comparing the SP and uniaxial creep test results. In the present study, the SP creep tests were carried out at 850°C on various Ni-base alloys having different rupture elongations in the range of 0.06-0.63 to investigate the influence of ductility on the value of F/σ. The F/σ value was determined for each alloy by correlating SP creep rupture data with corresponding uniaxial creep ones. The experimental results revealed that the F/σ value increased with increasing rupture elongation up to 0.45 and remained almost constant at around 2 with further increase of rupture elongation. This result indicated that the SP creep rupture test result could be converted to that of uniaxial one if the ductility on a given material was available. Moreover, the correlation between the F/σ and the equivalent fracture strain in SP creep test specimen were also analyzed to establish a procedure for estimating the stress equivalent to the SP load from the SP creep test result alone. As the result, the variation of F/σ with the equivalent fracture strain was similar to its variation with the rupture elongation.
  • Dynamic Material Flow Analysis of Stainless Steels in Japan

    pp. 653-659

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    DOI:10.2355/tetsutohagane.TETSU-2016-043

    Dynamic material flow analysis of stainless steels in Japan during 1956-2014 has been conducted. End uses of stainless steels were divided into 9 categories, i.e. construction, industrial machinery, electrical and electronic equipment, household and commercial appliance, passenger vehicle, truck and bus, other transportation, container, and other products. Stainless steels were divided into ferritic stainless steels and austenitic stainless steels. It was found that in-use stocks of austenitic stainless steels for construction, industrial machinery, electrical and electronic equipment, household and commercial appliance, truck and bus, container, and other products have reached constant levels. On the other hand, only those for truck and bus, container have been reached constant levels for ferritic stainless steels. It was estimated that the maximum in-use stock per capita for ferritic, austenitic and the total stainless steels was 59 kg/cap., 106 kg/cap., 163 kg/cap., respectively.

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