• Title/Summary/Keyword: 개량 9Cr-1Mo 강

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A Study on Microstructure and Mechanical Properties of Modified 9Cr-1Mo and 9Cr-0.5Mo-2W Steels for nuclear Power Plant (원자력용 개량 9Cr-1Mo 및 9Cr-0.5Mo-2W 강의 미세조직과 기계적 특성 연구)

  • Kim, Seong-Ho;Song, Byeong-Jun;Han, Chang-Seok;Guk, Il-Hyeon;Ryu, U-Seok
    • Korean Journal of Materials Research
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    • v.9 no.11
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    • pp.1137-1143
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    • 1999
  • Microstructure and mechanical properties of Mod.9Cr-1Mo and W added 9Cr-0.5Mo2W steels were investigated for liquid metal reactor (LMR) heat exchange tube. The tempering temperatures at which cell structure was formed were $700^{\circ}C$ for Mod.9Cr-1Mo steel and $750^{\circ}C$ for W added 9Cr0.5Mo-2W steel. indicating the recovery of dislocation was delayed by the addition of W. 9Cr-0.5Mo-2W steel had the same kinds of precipitates with Mod.9Cr-1Mo steel, but the W was included in the precipitates in 9Cr-0.5Mo-2W steel. Micro-hardness and ultimate tensile strength of 9Cr-0.5Mo-2W steel were higher than those of Mod.9Cr-1Mo steel. The impact property of Mod.9Cr-1Mo steel was superior to that of 9Cr-0.5Mo-2W steel.

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Effect of Hardness and Substructure on Long-term Creep Behavior of Mod.9Cr-1Mo Steel (개량 9Cr-1Mo 강의 장시간 크리프거동에 미치는 경도와 하부조직의 영향)

  • 박규섭;이근진;정한식;김정호;정영관;엔도타카오
    • Journal of the Korean Society for Precision Engineering
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    • v.21 no.2
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    • pp.168-176
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    • 2004
  • Interrupted creep tests were carried out on the Mod.9Cr-1Mo steel in order to investigate the structural degradation during creep. The ranges of creep stress and temperature were from 71 to 167MPa and 873 to 923k, respectively. The change of hardness and tempered martensitic lath width were measured in the grip and gauge parts of interrupted specimens. The lath structure was thermally stable in static conditions, but was not stable during creep, and the structural evolution was enhanced by creep strain. The relation between the change in lath width and strain was described in the from, $\delta$W= a ($W_s-W_o$)$cdot;varepsilon$, where $\varepsilon$ is the strain, $W_o$is the initial lath width, $W_s$ is the final lath width depending solely on stress, and a is the constant of the magnitude of 0.67 $\mu$m /strain. The change in Victors hardness was expressed by a one-valued function of creep life consumption ratio. Based on the empirical relation between strain and lath width, a model was proposed to explain the relation between change in hardness and creep life consumption ratio. The model revealed that about 65$%$ of dislocations in lath structures were eliminated by the migration of subboundaries.

Analysis of Mechanical and Ultrasonic Properties for the Evaluation of Material Degradation in Modified 9Cr-1Mo Steel (개량형 9Cr-1Mo 강의 열화도 평가를 위한 기계적 성질 및 초음파 특성 분석)

  • Hyun, Y.K.;Won, S.H.;Lee, S.H.;Son, Y.H.;Lee, J.H.;Kim, I.B.
    • Journal of the Korean Society for Heat Treatment
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    • v.23 no.4
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    • pp.198-204
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    • 2010
  • Modified 9Cr-1Mo steels possess excellent high-temperature mechanical properties and are widely used in energy conversion industries. However, in-service materials degradation, such as softening, carbide-induced embrittlement, temper embrittlement, etc., can take place during long-term operation. Evolution of microstructure due to service exposure to high temperature has a strong effect on the performance of heat resistant steels. In case of modified 9Cr-1Mo steels, precipitation of $Fe_2Mo$-type laves phases and coarsening of $M_{23}C_6$-type carbides are the primary cause of degradation of mechanical properties such as toughness, hardness, tensile strength and creep resistance. This study was aimed at finding reliable parameter for assessing the integrity of modified 9Cr-1Mo steels. Characteristic parameters were attained between mechanical and ultrasonic properties.