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

Tetsu-to-Hagané Vol. 101 (2015), No. 8

  • A Novel Measurement Method for Coal Thermoplasticity: Permeation Distance

    pp. 407-415

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    DOI:10.2355/tetsutohagane.TETSU-2015-013

    A novel measurement method for coal thermoplasticity was developed, where permeation distance of thermally plastic coal into glass beads layer placed on the coal sample was measured. The characteristic of this method is simulating the condition in a coke oven, especially void structure around the plastic layer by using glass beads and coking pressure by applying a load. In a standard condition, the coal sample is heated to 550 °C, and coal sample softens and permeates into the glass beads layer, then the permeation distance is measured after cooling the sample. The maximum permeation distance measured is roughly correlated with Gieseler fluidity, however large deviation is observed especially for high fluidity coals. Moreover, the deterioration of coke strength is observed in case that long permeation distance coal is used in a coal blend for cokemaking. This new measurement method clearly shows the difference in coking property of high fluidity coal as well as solving the problems in Gieseler plastometer method for evaluating high fluidity coals. By employing the permeation distance method, contribution to the production of high strength coke and effective usage of caking coal will be expected.
  • Shaft Furnace Simulation by Mathematical Model Considering Coke Gasification Rate in High Temperature

    pp. 416-421

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    DOI:10.2355/tetsutohagane.TETSU-2015-017

    Shaft furnace (cupola) is a scrap melting furnace and it can reduce CO2 emission because it requires no reducing agents. In a shaft furnace, coke gasification reactions by CO2 and H2O are occurred in high temperature and they have great effects on coke rate in shaft furnace because they are strong endothermic reactions. So prediction of shaft furnace operation needs accurate gasification rates. In this study, first, gasification rates by CO2/N2 and H2O/N2 system were measured at 1573, 1673, 1773 and 1873 K. Diffusion coefficients in gasification rates were modified to fit experimental results. Next, one-dimensional mathematical model using modified gasification rates was developed for shaft furnace simulation. The effects of coke size and blast moisture on coke rate were calculated and compared with actual operations. Operational results were accurately predicted by the model.
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  • Decorated Dislocations with Fine Precipitates Observed by FIB-SEM Slice-sectioning Tomography

    pp. 422-425

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    DOI:10.2355/tetsutohagane.TETSU-2015-004

    Dispersion behavior of intragranular NbC precipitates them in Nb added austenitic stainless steel were investigated via nanoscopic characterization, FIB-SEM slice-sectioning tomography, energy-dispersive X-ray spectrometry (EDS), selected area electron diffraction pattern (SAEDP) and transmission electron microscopy (TEM). The heterogeneous dispersion of fine intragranular NbC precipitates were visualized, and in particular, it was found that they were on the {111} slip plane and interacted with <110> dislocations.
  • Effects of Partitioning of Manganese and Silicon during Intercritical Annealing on Transformation Behavior and Mechanical Properties of Low Alloyed TRIP-assisted Steel Sheets

    pp. 426-434

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    DOI:10.2355/tetsutohagane.TETSU-2015-015

    The effects of partitioning of Mn and Si during intercritical annealing on transformation behavior and mechanical properties of low alloyed TRIP-assisted steel sheets were investigated by using 0.17%C-1.5%Si-1.7%Mn steel. During intercritical annealing, Mn and Si were concentrated in austenite and ferrite by partitioning, respectively. This partitioning of Mn and Si suppressed bainite transformation during austempering and decreased the volume fraction of retained austenite and its C content. This could be mainly because partitioning of Mn and Si shifted the T0’ curve to the lower C concentration region and stopped bainite transformation at a lower C concentration in residual austenite. The decrease in the volume fraction of retained austenite and its C content deteriorated the ductility of low alloyed TRIP-assisted steel sheets. Although proper intercritical annealing is necessary to increase C content in retained austenite, it should be noted that excessive intercritical annealing can deteriorate the ductility of low alloyed TRIP-assisted steel sheets because of partitioning of Mn and Si.
  • Mechanical Stability Analysis on Ideal Body-Centered Cubic Crystals under Finite Deformation

    pp. 435-444

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    DOI:10.2355/tetsutohagane.TETSU-2015-021

    This study investigates mechanical stability of ideal b.c.c. crystals (α-Fe, Mo and Nb) under finite deformation. Strain energy density W is introduced using a lattice dynamics model with the second- and third-order elastic constants measured by experiments. Critical stress and strains are determined from the failure of strong ellipticity condition for stress equilibrium equation. Present numerical analysis for (001) in-plane deformation revealed that mechanical stability of the crystals depends on the deformation mode including the sign. It also revealed that the number and direction of emerging characteristic curves vary with the critical point reflecting on the nature of inter-atomic bonding. We also conducted the stability analyses for simple shear deformations on the principal planes: (100), (110) and (111). The critical shear stress show semi-quantitative agreement with those reported by first-principle calculation. Average of the shear stress over shear modulus ratio turns out to be 11%, which is close to the displacement burst condition measured by nano-indentation experiments.
  • Improvement of Desalted Paddy Soil by the Application of Fertilizer Made of Steelmaking Slag (Recovery of a Paddy Field Damaged by the Tsunami Using Fertilizer Made of Steelmaking Slag-1)

    pp. 445-456

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    DOI:10.2355/tetsutohagane.TETSU-2014-131

    Paddy fields located near the coast of northeastern Japan have suffered significant damage from the tsunami caused by the earthquake. The restoration of a damaged paddy field can be achieved with the washing out of Na by desalting treatment and fertilization with silica. The concentration of Na can be effectively reduced with Ca supplements. As steelmaking slag contains CaO and SiO2, it has a strong potential to become an economic solution for the recovery of fields.
    To evaluate the effect of fertilizer made of steelmaking slag, a new soil-filled column testing method was developed to simulate the paddy field conditions. The column was composed of a plow layer containing pore water and soil with fertilizer, along with a layer of surface water. Every day, water sample was collected from the bottom of the column and the same amount of fresh water was supplied for approximately 2 months. The original soil and the soil after desalting were used with and without fertilizer made of steelmaking slag. The influence of soil particle size was also investigated.
    During the experiment, the pH increased, while the oxidation and reduction potential decreased day by day; thus, the typical changes under paddy field conditions were simulated. Supplementation with fertilizer made of steelmaking slag led to the increase in Ca content and pH. In contrast, most of the Na was washed out by water exchange during the experiment; however, an initial decrease in its content was observed by the addition of fertilizer made of steelmaking slag.
  • Long-term Dissolution Characteristics of Various Fertilizers Made of Steelmaking Slag in a Desalted Paddy Soil Environment (Recovery of a Paddy Field Damaged by the Tsunami Using Fertilizer Made of Steelmaking Slag-2)

    pp. 457-464

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    DOI:10.2355/tetsutohagane.TETSU-2014-132

    To evaluate the effect of steelmaking slag as fertilizer in a flooded paddy field, a soil-filled column testing method was developed. The original soil and the soil after desalting with and without fertilizer made of steelmaking slag were used. Three brands of fertilizer with different compositions and phase ratios were evaluated.
    The results showed a pH increase and Ca supplement after the application of fertilizer made of steelmaking slag, and these changes were independent of the brand. The dissolution of Ca was higher when fertilizer with high CaO concentration was used. The composition of the fertilizer had an effect on cation dissolution behavior not only of Ca, but also of Mn, Si, and Mg. The cation mass balance before and after the experiment was studied. Most of the Na was contained in the water and was washed out during the experiment. The application of fertilizer did not affect the residual Na concentration clearly. The amount of Ca supplied by the fertilizer was almost the same as that contained in the soil, and a significant difference in the amount of Ca was observed between the fertilizer brands that used. In addition, it was deduced that free-CaO and the solid solution phase of 2CaO·SiO2 and 3CaO·P2O5 was dissolved and supplied additional Ca during the experiment, but the matrix phase was not dissolved and, thus, remained in the soil.

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