Journal of the Korean Society for Heat Treatment (열처리공학회지)

The Korean Society for Heat Treatment (한국열처리공학회)
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Study on the Embrittlement of the Mod. 9Cr-1Mo Steel Tempered at $550^{\circ}C$

Mod. 9Cr-1Mo강에서의 $550^{\circ}C$ 부근에서 템퍼링시 발생하는 취성에 관한 연구

  • Gu, Ji-Ho (School of Materials Science and Engineering, Changwon National University) ;
  • Shin, Jong-Ho (School of Materials Science and Engineering, Changwon National University) ;
  • Hur, Sung-Kang (Doosan Heavy Industry)
  • 구지호 (창원대학교 나노신소재공학부) ;
  • 신종호 (두산중공업 기술연구원) ;
  • 허성강 (창원대학교 나노신소재공학부)
  • Received : 2010.04.21
  • Accepted : 2010.05.06
  • Published : 2010.05.30
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Abstract

The modified 9Cr-1Mo steel (P91 steel) is very popular as a boiler tube material of the USC (Ultra-Supercritical) power plants. The steels were tempered in the temperature range of 400 to $650^{\circ}C$ and the mechanical tests, such as impact and hardness tersts were performed at the room temperature for the tempered steels. A drop in the impact value (embrittlement) and the hardeness increase were simultanously observed in the range of temperature between $475^{\circ}C$ and $600^{\circ}C$, particularly at $550^{\circ}C$. TEM observation shows the hardening was caused by $M_2C$, resulting in the embrittlement. And the maximum volume fraction of $M_3C$ was also observed at $550^{\circ}C$, Therefore, the embrittlement seems to be caused by both the $M_2C$ and $M_3C$.

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References

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