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

Tetsu-to-Hagané Advance Publication

  • Effect of Natural Gas Injection Point on Combustion and Gasification Efficiency of Pulverized Coal under Blast Furnace Condition

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    DOI:10.2355/tetsutohagane.TETSU-2017-087

    The reduction of CO2 emission from the ironmaking process is important issue from the view of environmental problems typified by global warming in recent years. Low RAR (reducing agent rate) operation of the blast furnace is one of effective measures for reducing CO2 emission. Injection of HRA (hydrogenous reducing agents) from the tuyere (where is the lower part of blast furnace) is also effective measure. In this study, the influence of HRA injection point on combustion and gasification efficiency of pulverized coal (PC) in the case of simultaneous injection of HRA and PC from double-channel lance was examined by small scale combustion furnace and three-dimensional numerical simulation for improvement permeability in blast furnace. Combustion experimental conditions were in three cases, case1: injected HRA from outer side and PC from inner side of double-channel lance, case2: injected HRA from inner side and PC from outer side of double-channel lance and case3: injected HRA and PC premixed. As a result, the combustion and gasification efficiency was increase in the order of case3, case2 and case1. The rate of combustion and gasification of PC was investigated in case1. Not only the oxidation reaction was also accelerated CO2 and H2O gasification reaction in the case of simultaneous injection HRA and PC. A three-dimensional numerical simulation of the experimental furnace was conducted, we confirmed the increase of combustion temperature, the acceleration of oxygen consumption and gasification reaction as with the experimental results in the case of simultaneous injection HRA and PC.
  • Development of On-site Measurement Technique of Retained Austenite Volume Fraction by Compact Neutron Source RANS

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    DOI:10.2355/tetsutohagane.TETSU-2017-080

    Neutron engineering diffraction is a powerful technique which provides the information of the micro structure of steels in bulk-average, while X-ray diffraction or Electron backscatter diffraction can provide information only from the surface layer. However, such measurement using neutron diffraction is typically performed in a large facility such as a reactor and a synchrotron, while a compact neutron source has never been used for this purpose. Authors have recently developed a neutron diffractometer installed in Riken Accelerator driven compact Neutron Source (RANS) and succeeded in the measurement of texture evolution of a steel sheet. In this study, we made an attempt to measure the volume fraction of retained austenite by RANS. Background noise was carefully eliminated in order to detect as many diffraction peaks as possible with low flux neutrons. The volume fraction was estimated by Rietveld analysis. The accuracy of the measurement result was discussed by comparing with those obtained by a large neutron facility (J-PARC TAKUMI). The volume fraction obtained by RANS with reasonable measurement time, i.e. 30-300 min, showed only 1-2% discrepancies with those obtained in J-PARC. These comparisons suggest that neutron diffraction by RANS is capable of quantitative analysis of the volume fraction of crystal phases, showing the possibility of practical use of an in-house compact neutron source in the industry.
  • Reduction of Contact Resistance on Titanium Sheet Surfaces by Formation of Titanium Carbide and Nitride, and Its Stability in Sulfuric Acid Aqueous Solution

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    DOI:10.2355/tetsutohagane.TETSU-2017-085

    Separators for solid polymer fuel cells must have a low contact resistance with the carbon paper and stability in a corrosive environment of sulfuric acid in the cell. The titanium surface is highly resistant to corrosion thanks to a passive film but has high contact resistance.In this study, titanium carbide or nitride as the electrical conductor was formed on the surface by annealing commercially pure titanium sheet. The contact resistances of these sheets were evaluated before and after a sulfuric acid aqueous solution exposure test, “pH4 at 80°C for 4 days”, briefly simulating the operating environment. In addition, the same evaluation test was conducted with a surface with TiC formed dipped in nitric acid to enhance the stability in a sulfuric acid solution.The initial contact resistance falls below 10 mΩ·cm2 by formation of TiC and TiN, Ti2N on sheet surface. However, the contact resistance rises to 100 or above after the exposure test because a large amount of TiO2 precipitates. This is probably because TiC and TiN are dissolved by sulfuric acid, generating TiO2.By contrast, dipping in nitric acid hardly raises the contact resistance from less than 10 even after the exposure test. It is considered from the results of surface analyses that Ti ion generated by partial dissolution of TiC is turned into TiO2 by the oxidizability of nitric acid, changing the surface structure covering TiC. It is considered that the newly formed TiO2 film enhanced stability in a sulfuric environment.
  • Characterization of Liquid Metal Embrittlement for the Hot Stamped Galvannealed Boron Steel Sheets

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    DOI:10.2355/tetsutohagane.TETSU-2017-076

    SEM observation was conducted on cross-sections of galvannealed (GA) boron-steel sheet specimens, subjected to direct hot-stamping tests (V-bending), to study liquid metal embrittlement (LME), caused by liquid zinc in the coating. Specimens were heated to 1173 K (900°C) in a combustion gas furnace, and subsequently hot stamped in a cooled, V-shaped die. The locus of intersections between the Fe-Zn ferrite grain-boundaries (expected to be filled with liquid zinc) of the coating layer, prior austenitic grain boundaries of the steel substrate, and the coating interface, were examined. Specimen cracking originated at the coating/steel interface, and propagated along prior austenitic grain boundaries, where liquid zinc directly contacted the steel substrate. These prior austenitic grain boundaries were considered to be “geometrically favored” sites for initiating LME cracking. Cracking did not occur at sites where direct contact with liquid zinc was not established. There were numerous sites where cracking did not occur despite contact between liquid zinc and prior austenitic grain boundaries, at the coating/steel interface. In heavily cracked specimens, there were 4.7 to 5.9 cracks per mm of coating interface. Cracking occurred in only 23 to 36% of the “geometrically favored” sites at the coating interface. At the bottom of large cracks, cracks were round-bottomed. Vickers hardness at the bottom was lower than that at the sidewall. Therefore, ferrite or bainite transformation, enhanced by plastic deformation, was indicated. This suggested an absence of zinc propagation at deeper austenitic grain boundaries, terminating crack propagation despite the plastic deformation.
  • Overview of Dynamic Strain Aging and Associated Phenomena in Fe-Mn-C Austenitic Steels

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    DOI:10.2355/tetsutohagane.TETSU-2017-089

    This paper presents an overview of the recent works on dynamic strain aging (DSA) of Fe-Mn-C austenitic steels including Hadfield and twinning-induced plasticity (TWIP) steels. First, a model of the DSA mechanism and its controlling factors are briefly explained in terms of Mn-C coupling and dislocation separation. Then, we introduce the effects of DSA on mechanical properties such as work hardening capability, uniform elongation, post-uniform elongation, and fatigue strength. Specifically, we note the pinning effect on extended dislocation for the work hardening, the Poretvin-Le Chatelier banding effect on damage evolution for the elongation, and the crack tip hardening/softening effect on crack resistance for the fatigue strength. We believe that this overview will help in designing advanced high-strength steels with superior ductility and fatigue resistance.
  • Effects of Steel Grade, Austenite Structure and Cooling Conditions on the Deformation of Square Section Bloom of Steel Cast Continuously and Stress Generation in the Bloom by Immersion Cooling

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    DOI:10.2355/tetsutohagane.TETSU-2017-083

    In recent years, the treatment of inverse-transformation has been adopted in the HCR (Hot Charge Rolling) process of CC (Continuous Casting)-Blooming for steel production to prevent surface cracking on blooming. However, the quenching of bloom in this treatment occasionally causes some troubles, such as distortion of bloom and quenching crack. On the behavior of deformation of bloom and the generation of stress in cross section of bloom, the effects of cooling conditions of immersion cooling (quenching), steel grade and size of austenite grain were analyzed in order to prevent these troubles by the model of metallo-thermo-mechanics in this study. The results obtained from this analysis are as follows: The behavior of deformation of bloom and the distribution of stress in cross section of bloom by quenching is affected by steel grade and size of austenite grain caused by the difference in the distribution of amount of both diffusion and no diffusion transformation accompanying expansion and heat generation by latent heat in cross section of bloom.

Article Access Ranking

21 Feb. (Last 30 Days)

  1. Comparison of Agglomeration Behavior of Fine Particles in Liquid among Various Mixing Operations ISIJ International Vol.58(2018), No.1
  2. Hydrogen Embrittlement Behavior of Ultra-high Strength Dual Phase Steel Sheet under Sustained Tensile-loading Test ISIJ International Vol.58(2018), No.1
  3. Evaluation of Porosity Closure during Hot Compression of Steel by Synchrotron X-ray Laminography and FEM Analysis Tetsu-to-Hagané Vol.104(2018), No.2
  4. Effect of CaO/Al2O3 Ratio of Ladle Slag on Formation Behavior of Inclusions in Mn and V Alloyed Steel ISIJ International Vol.58(2018), No.1
  5. Effect of Added Olivine on Iron Ore Agglomerate During Induration ISIJ International Advance Publication
  6. Thermal Strength Characteristics and Mechanism of Iron Ore and Carbon Pellets in the Non-isothermal Reduction Process ISIJ International Advance Publication
  7. Preliminary Investigation on the Capability of eXtended Discrete Element Method for Treating the Dripping Zone of a Blast Furnace ISIJ International Vol.58(2018), No.1
  8. Experimental Measurements of Gas Shielding Characteristics in TIG Welding with a Constricted Nozzle QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY Vol.36(2018), No.1
  9. Acceleration of Macrosegregation Simulation Based on Lattice Boltzmann Method ISIJ International Vol.58(2018), No.1
  10. Identification of Hydrogen Trapping Sites in a Strained Ferritic-martensitic Dual Phase Steel Tetsu-to-Hagané Vol.104(2018), No.1

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21 Feb. (Last 30 Days)

  1. blast furnace
  2. blast furnace permeability
  3. blast furnace productivity
  4. galvannealing
  5. 鉄と鋼
  6. mgo
  7. hydration
  8. steel microstructure mechanical properties
  9. bearing steel
  10. coil break