Journal of High Pressure Institute of Japan
Online ISSN : 1347-9598
Print ISSN : 0387-0154
ISSN-L : 0387-0154
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Volume 61, Issue 1
Displaying 1-4 of 4 articles from this issue
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Original Paper
  • Examination of master curve shape of KIc of steel materials including embrittlement
    Akira KIUCHI
    2023 Volume 61 Issue 1 Pages 4-14
    Published: 2023
    Released on J-STAGE: March 01, 2023
    DOIhttps://doi.org/10.11181/hpi.61.4
    JOURNAL FREE ACCESS
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    In this report, the equation of the master curve of ASTM E 1921 was applied to the temperature dependence of the plane strain fracture toughness, KIc of steel materials, and its shape was examined based on the literature values. The target materials are used turbine rotors, and domestic and foreign nuclear pressure vessel steels. The brittle-ductile transition temperature, FATT in the Charpy impact test of them ranges from －22 to ＋177℃. When the test temperature, T is arranged by Excess Temperature, Te(＝T－FATT), it is clarified that the relationship between KIc and Te is expressed by the same equation as the master curve of ASTM E 1921, regardless of the magnitude of FATT. The difference between T where KIc＝100 MPa√m and T0 of the master curve of ASTM E 1921 is expressed using the 0.2% offset yield stress at T＝T0 as a parameter. In addition, the problems when applying the master curve to the actual machine are shown.
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  • Application of Elastic-Plastic Hinge Method to Up-lift Behavior of Flat-Bottom of Cylindrical Tank subject to Seismic Excitation
    (5th Report)
    Yoshihiko YAMAUCHI, Noriyuki KIYONO, Atsushi AOKI, Takashi MIYAUCHI
    2023 Volume 61 Issue 1 Pages 15-30
    Published: 2023
    Released on J-STAGE: March 01, 2023
    DOIhttps://doi.org/10.11181/hpi.61.15
    JOURNAL FREE ACCESS
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    Oil storage tanks are usually constructed directly on tank foundations without anchors. In such a flat-bottom cylindrical tank subject to seismic horizontal force, a part of the bottom plate adjacent to the shell will be lifted off the tank foundation by the overturning moment, and excessive plastic strain cyclically occurs at the toe of the inside fillet weld of the shell-to-bottom joint.
    Previously, expanding the basic theory of Elastic-Plastic Hinge Method (E.P.H.M.) to uplift behavior of flat-bottom of cylindrical tank, the authors proposed the analytical method to evaluate the integrity of annular plate adjacent to the shell from the viewpoint of seismic design, and calculations were carried out for a 32,000kl oil storage tank of high strength steel SPV490Q2)6). Furthermore, the equilibrium equations in consideration of 2 elastic-plastic hinges of uplifted bottom plate for the elastic sidewall tank were formulated, considering nonlinear M～ϕ relationship based on elastic-plastic beam theory (Relation-Ⅰ). Then, calculations are carried out for 32,000kl/18,200kl oil storage tanks, and the effectiveness of this method was shown by comparing it with results of FEM non-linear axisymmetric analysis7)8).
    In this paper, the effect of large deflection of uplifted bottom plate is taken into consideration based on the finite deformation theory of strap, and the method (E.P.H.M.) is expanded for the analysis on uplift behavior of flat-bottom of tank with large deflection.
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  • Effects of micro-alloying on hydrogen embrittle-ment susceptibility
    Yutaka TSUCHIDA
    2023 Volume 61 Issue 1 Pages 31-42
    Published: 2023
    Released on J-STAGE: March 01, 2023
    DOIhttps://doi.org/10.11181/hpi.61.31
    JOURNAL FREE ACCESS
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    Effects of micro-alloying have been examined on hydrogen embrittlement (HE) of various hot stamping (HS) steel sheets. Referring to these researches, formation and function of the alloy carbonitrides were given systematic consideration for analyzing their effects on HE. The state of hydrogen is important issue, and was determined preferably by thermal desorption analysis (TDA) rather than hydrogen permeation measurement. Although the coherent precipitates (carbonitrides) containing Nb, Ti or V in ferritic matrix can trap hydrogen effectively, they have negligible influence on the easy-to-move hydrogen that should be responsible to HE. This might be caused by the decreased amount of the precipitates in the HS process. The alloy carbonitrides, which had remained during austenitizing treatment and is in-coherent to ferritic matrix, restrain grain growth and prevent the degradation of grain boundary (GB) cohesion. Molybdenum (Mo) strengthens GB cohesion, not by forming carbonitrides but by segregating along GB. Both carbon (C) and boron (B) also segregate along GB and would strengthen GB cohesion. These enhanced GB cohesion makes the steels resisting to HE. It is true for steels like high strength spring steel, V alloyed high strength bolt steel and hydrogen gas accumulator steel, that micro-alloying of Nb is the key issue for improving the anti-HE property. The influence of V carbonitride on HE susceptibility appreciates continuous attention, especially in case of high temperature tempering.
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