鉄と鋼
Online ISSN : 1883-2954
Print ISSN : 0021-1575
ISSN-L : 0021-1575
早期公開論文
早期公開論文の7件中1~7を表示しています
  • 小西 剛嗣, 柴田 実奈, 三木 順平, 潮田 浩作
    原稿種別: 論文
    論文ID: TETSU-2019-067
    発行日: 2019年
    [早期公開] 公開日: 2019/08/19
    ジャーナル フリー 早期公開

    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.

  • 田中 亮平, 山﨑 慶太, 関 浩子, 松本 雄樹, 河合 潤
    原稿種別: 論文
    論文ID: TETSU-2019-050
    発行日: 2019年
    [早期公開] 公開日: 2019/08/09
    ジャーナル フリー 早期公開

    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.

  • 阿部 太一, 下野 昌人, 中村 健
    原稿種別: 論文
    論文ID: TETSU-2019-041
    発行日: 2019年
    [早期公開] 公開日: 2019/07/30
    ジャーナル フリー 早期公開

    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.

  • 山下 孝子, 榎本 正人, 田中 裕二, 松田 広志, 奥田 金晴
    原稿種別: 論文
    論文ID: TETSU-2019-020
    発行日: 2019年
    [早期公開] 公開日: 2019/06/06
    ジャーナル フリー 早期公開

    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.

  • 日高 哲郎, 野田 尚昭, 佐野 義一, 甲斐 信博, 藤本 宏義
    原稿種別: 論文
    論文ID: TETSU-2019-017
    発行日: 2019年
    [早期公開] 公開日: 2019/04/23
    ジャーナル フリー 早期公開

    In our earlier study, the authors revealed that the fatigue limit of ductile cast iron (DCI) specimens whose shapes are similar to the welded joint shapes is about three times larger than that of the welded joint specimens. However, since many defects are usually included in the DCI specimens, the fatigue limit of DCI joints decreases with increasing the maximum defect size. In this paper, therefore, the maximum defect size is estimated by using statistics of extremes. Then, the lowest fatigue limit corresponding to the maximum defect size is estimated from the 4 parameter model and compared with the lowest fatigue limit of the welded joint. As a result, it was confirmed that the lowest fatigue limit of the DCI specimens is about twice as large as the welded joint.

  • 増岡 弘之, 古谷 真一, 竹山 隼人, 平 章一郎, 松崎 晃
    原稿種別: 論文
    論文ID: TETSU-2019-007
    発行日: 2019年
    [早期公開] 公開日: 2019/04/18
    ジャーナル フリー 早期公開

    It is well known that Si, Mn and B, the alloying elements for high strength steel sheets, easily form oxides on the steel surface during annealing in a reducing atmosphere, and those oxides have a large influence on the surface performance of steel sheets, such as phosphatability. In this work, we discovered that the oxidation behavior of Mn-added high strength cold-rolled steel sheets could be simulated on mild steel sheets by using an ion plating method and investigated the relationship between the morphology of Mn oxides and phosphatability under the condition that both the amount and kind of Mn oxides were fixed. In a simulated Mn-O layer, fine surface oxides, which covered most of the steel surface, were observed after annealing. On the other hand, in a Mn-B-O layer, large globular surface oxides were observed on the steel surface, and the Fe surface was partially bare. The B-Mn compound oxide is considered to be in a molten phase during annealing because the melting point of the compound oxide is lower than the annealing temperature, and as a result, it is thought that large B-Mn compound oxides coagulate and grow during annealing. In addition, it was found that the large B-Mn compound oxides (about 500 nm) interfere with steel dissolution in the phosphate solution. These results demonstrate the importance of controlling the morphology as well as the amount and kind of surface oxides for obtaining good phosphatability of Mn-added high strength cold-rolled steel sheets.

  • 安田 雅人, 片岡 隆史, 牛神 義行, 村上 健一, 潮田 浩作
    原稿種別: 論文
    論文ID: TETSU-2019-013
    発行日: 2019年
    [早期公開] 公開日: 2019/04/18
    ジャーナル フリー 早期公開

    Recrystallization and grain growth are important phenomena for controlling the mechanical and magnetic properties of steels through texture. Only a limited number of studies have been carried out on texture evolution during recrystallization and grain growth in heavily cold-rolled Si steel. The present study first focuses on clarifying the texture evolution during normal grain growth, followed by an investigation into the development of the {411}<148> component during recrystallization. The {411}<148> component is remarkably developed during normal grain growth after the completion of recrystallization. At just fully recrystallized stage, the diameters of the {411}<148> grains were larger than that of the grains with other orientations. Therefore, the {411}<148> grains significantly grew owing to the size advantage.

    Just at the commencement of recrystallization, differences in grain diameter of recrystallized grains in terms of crystal orientation were not detected. However, it is worthwhile to mention that the nucleation of {411}<148> recrystallized grains is unexpectedly fast in heavily cold-rolled Si steel. Recrystallized {411}<148> grains were observed to nucleate in the deformed α-fiber grains, especially near the grain boundaries. Nuclei with {411}<148> orientation grow easily due to the high mobility of the interface between the recrystallized/non-recrystallized grains and the high driving force. Consequently, the diameter of a {411}<148> recrystallized grain becomes relatively large upon the completion of recrystallization. This contributes to the selective grain growth during the normal grain growth stage because of the size effect.

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