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

Tetsu-to-Hagané Advance Publication

  • Intra-Particle Water Migration Dynamics during Iron Ore Granulation Process

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    DOI:10.2355/tetsutohagane.TETSU-2019-056

    The influence of iron ore properties, such as ore type, mineralogical texture, and particle size, on the intra-particle water migration dynamics were evaluated using immersion method. When immersed, ores were reached 68–78% of their final saturation in first 60 s and then approached final saturation slowly. It typically took up to 1×105 s to reach final saturation. Compared with the initial and final saturation water contents of 2.8–4.0 mass% in the case of Brazilian ores, Australian ores showed higher water contents of 5–6.4 mass% due to more porous structure. While the final saturation water content was partially explained by the porosity and total pore volume of ores, the kinetics of water migration should be considered to explain the saturation curve of different ores. In terms of mineralogical texture, porous texture showed higher final saturation water contents than dense texture. Finer particles showed higher final saturation water contents than coarser particles. A revised migration model was introduced to explain the effect of pore size distribution and trapped air. It was revealed that water migration proceeds more readily in the finer pores due to the larger capillary force, which is needed to overcome the trapped air. The water migration in the coarser pores is restrained due to the weak capillary force against trapped air, resulting in lower degree of saturation at equilibrium. Compared with Australian ores, Brazilian ores showed a lower degree of saturation due to their higher proportion of coarse pores.
  • Evaluation Method for Small Fatigue Crack Growth Life of Low Carbon Steel with Fine Grain HAZ Microstructure Simulated with Heat Treatment

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    DOI:10.2355/tetsutohagane.TETSU-2019-072

    Small fatigue crack growth tests utilizing DIC technique are carried out for low carbon steel with two different heat treatment to establish the small fatigue crack growth evaluation method. As a result, small fatigue crack growth rate (FCGR) looked larger than that of large crack by evaluating with usual stress intensity factor range. The small fatigue crack opening stress, successfully measured by using DIC technique, were decreasing with loading stress was increasing. In addition, by using effective cyclic J integral range calculated with measured crack opening stress, even small fatigue crack growth rates were almost agreed with that of large crack data. Due to this evaluation, microstructural resistance, appeared in the region of crack length is 0.2 mm or less, is successfully visualized. Finally, estimated small fatigue crack growth life by using Paris’s law of large crack, effective cyclic J integral range and conventional approximation formula of crack opening stress was almost agreed with corresponding experimental data.
  • Determination of Facet Plane and Cleavage Fracture Plane of the Top Dross Formed in a Molten Zinc

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    DOI:10.2355/tetsutohagane.TETSU-2019-067

    In a molten zinc bath of a continuous galvanizing line, top dross particles crystallize as Fe2Al5 intermetallic compound containing Zn. These particles easily adhere to the steel sheets causing surface defects. Therefore, controlling the top dross particles is a key issue. The present study focused on the determination of facet plane of top dross using three-dimensional analysis of morphology of the top dross by simultaneous exploitation of the serial sectioning process and electron back scattering diffraction (EBSD). Furthermore, the crystallographic plane of the cleavage fracture surface of the top dross was determined by EBSD, after cleavage crack was introduced by Vickers hardness indentation. The following results were obtained: (1) The facet planes of the top dross consist of two planes of (001), four planes of {110} and eight planes of {111}. In addition, the top dross particles grow fastest in the [001] direction. Consequently, the top dross particle is concluded to have the polyhedron structure with 14 facet planes. (2) The cleavage fracture surface of the main crack in the top dross is (100) plane.
  • Fundamental Parameter Method for Energy Dispersive X-Ray Fluorescence and its Application to Stainless Steels as First Principles Calculation

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    DOI:10.2355/tetsutohagane.TETSU-2019-050

    Energy dispersive X-ray fluorescence (ED-XRF) spectrometer was built in the laboratory with low wattage X-ray tube and silicon drift detector using a 3D printer. SUS 304 and 316L stainless steels were measured by the ED-XRF spectrometer and a sequential type inductively-coupled plasma atomic emission spectrometer (ICP-AES). The results of quantitative analysis obtained by the fundamental parameter (FP) program developed by the authors were compared with the ICP-AES results, and concluded the following three points.(1) The FP method is a first principles method to theoretically calculate the concentration of elements using XRF. The accuracy and precision are satisfactory but inferior to the calibration curve method.(2) The representative accuracy and precision in SUS 304 quantification are expressed as 18.3±0.08% for Cr and 18.1±0.01% for Ni. These values are comparable to the accuracy and precision of ED-XRF. Therefore the FP method is suitable for the ED-XRF analysis; the calibration curve method (dj method) is highly precise and accurate, and thus suitable for wavelength dispersive (WD) XRF method.(3) Though it is said that the FP databases should be improved in order to increase the accuracy, the FP database improvements have not been effective.
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    1. Determination of Facet Plane and Cleavage Fracture Plane of the Top Dross Formed in a Molten Zinc Tetsu-to-Hagané Advance Publication
  • Effect of Magnetic Transitions on the Formation of the Thermal Vacancy in αFe

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    DOI:10.2355/tetsutohagane.TETSU-2019-041

    In the processes of precipitations and phase transformations, thermal vacancies play an important role through diffusions of atoms. Due to magnetic transitions, the thermal vacancy fraction becomes smaller in the ferromagnetic state comparing to the paramagnetic state. In this work, the effect of magnetic transitions on the vacancy formation was examined using Inden model for the magnetic excess Gibbs energy, which has been widely applied in the CALPHAD-type thermodynamic assessments. In the present work, the effect of magnetic transitions on SFeMag/R and HFeMag is estimated to be 0 ~ –0.5 and 0 ~ 0.06 eV, respectively, The differences between ferromagnetic and paramagnetic states of αFe are +0.06 eV for the enthalpy of vacancy formation, and −0.435 R for the entropy of vacancy formation.
  • Effects of Alloy Elements on Carbon Partitioning at Early Stages of Proeutectoid Ferrite Transformation in Low Carbon Mn-Si Steels

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    DOI:10.2355/tetsutohagane.TETSU-2019-020

    Controlling carbon concentration and its distribution among constituent phases is one of the most important issues to achieve high strength and ductility in the design of steel. The carbon distribution near the α/γ interface at the early stage of isothermal holding at 750ºC was measured and visualized in Fe-C-Mn-Si alloys, containing 2 mass%Si and 1.5 or 2 mass%Mn, using recently developed high precision FE-EPMA, and results were compared with the theory of ferrite growth in multi-component low alloy steel. The carbon concentrations at α/γ interfaces in austenite were generally between the NPLE/PLE and paraequilbrium γ/(γ+α) boundary concentrations. In alloys of carbon content smaller than the NPLE/PLE boundary, it seems that α/γ interfaces migrated under the condition close to paraequilibrium or with partially developed spikes of alloy elements at early stages. On the other hand, in alloys of bulk composition on the boundary and its higher carbon concentration side, Mn enrichment was observed at the interfaces, and the carbon concentration tended to be higher than those in alloys of lesser carbon content, albeit there were variations at individual interfaces.

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