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Development of Evaluation Technique of High Temperature Creep Characteristics by Small Punch-Creep Test Method (ll) - Boiler Header -

Sp-Creep 시험에 의한 고온 크리프 특성 평가 기술 개발(ll) - 보일러 헤더 -

  • Baek, Seung-Se (Dept.of Precision Mechanical Engineering, Graduate School of Chonbuk National University) ;
  • Lee, Dong-Hwan (Dept.of Precision Mechanical Engineering, Graduate School of Chonbuk National University) ;
  • Ha, Jeong-Su ;
  • Yu, Hyo-Seon (Automotive New Technology Research Center, Dept.of Mechanical Engineering, Chonbuk National University)
  • 백승세 (전북대학교 대학원 정밀기계공학과) ;
  • 이동환 (전북대학교 대학원 정밀기계공학과) ;
  • 하정수 (한국전력연구원(KEPRI)) ;
  • 유효선 (전북대학교 기계공학부, 자동차 신기술 연구소)
  • Published : 2002.01.01

Abstract

For the development of a new creep test technique, the availability of SP-Creep test is discussed for 1Cr-0.5Mo boiler header material. And some results are also compared with those of 2.25Cr- 1Mo steel which widely uses as boiler superheater tube. The results can be summarized as follows. The load exponents(n) obtained by SP-Creep test for 1Cr-0.5Mo steel are decreased with increasing creep temperature and the values are 15.67, 13.89, and 17.13 at 550$^{circ}C$ ,575$^{circ}C$ and 600$^{circ}C$, respectively. The temperature dependence of the load exponent is given by n = 107.19 - 0.1108T. This reason that load exponents show the extensive range of 10∼16 is attributed to the fine carbide such as M$_{23}$C$_{6}$ in lath tempered martensitic structures. At the same creep condition, the secondary creep rate of 1Cr-0.5Mo steel is lower than the 2.25Cr-1Mo steel1 due to the strengthening microstructure composed by normalizing and tempering treatments. Through a SEM observation, it can be summarized that the primary, secondary, and tertiary creep regions of SP-Creep specimen are corresponding to plastic bending, plastic membrane stretching, and plastic instability regions among the deformation behavior of four steps in SP test, respectively.y.

Keywords

1 Cr-0.5Mo Steel;SP-Creep Test;SP-Creery Rate(${\varepsilon}_{df}$;Creep Rupture Life;$t_{r}$;Load Exponent;H;Monkman-Grant Relation;Lath Tempered Martensite;Creep Deformation Behavior;Boiler Header

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