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Correlation between Microstructure and Charpy Impact Properties of FCAW HAZ of Thick Steel Plates for Offshore Platforms

해양플랜트용 후판강의 FCAW HAZ 미세조직과 샤르피 충격 특성의 상관관계

  • Lee, Hun (School of Materials Science and Engineering, University of Ulsan) ;
  • Lee, Hyunwook (School of Materials Science and Engineering, University of Ulsan) ;
  • Cho, Sung Kyu (Technical Research Center, Hyundai Steel Company) ;
  • Choi, Dongki (Technical Research Center, Hydrofast) ;
  • Kim, Hyoung Chan (Energy Plant R&D Group, Korea Institute of Industrial Technology) ;
  • Kwon, Yongjai (School of Materials Science and Engineering, University of Ulsan) ;
  • Lee, Jung Gu (School of Materials Science and Engineering, University of Ulsan) ;
  • Shin, Sang Yong (School of Materials Science and Engineering, University of Ulsan)
  • 이훈 (울산대학교 첨단소재공학부) ;
  • 이현욱 (울산대학교 첨단소재공학부) ;
  • 조성규 (현대제철 R&D센터) ;
  • 최동기 (하이드로훼스트 기술연구소) ;
  • 김형찬 (한국생산기술연구원 에너지플랜트그룹) ;
  • 권용재 (울산대학교 첨단소재공학부) ;
  • 이정구 (울산대학교 첨단소재공학부) ;
  • 신상용 (울산대학교 첨단소재공학부)
  • Received : 2019.06.19
  • Accepted : 2019.08.04
  • Published : 2019.08.27

Abstract

In this study, the correlation between microstructure and Charpy impact properties of FCAW(Flux cored arc welding) HAZ(Heat affected zone) of thick steel plates for offshore platforms was investigated. The 1/4 thickness(1/4t) location HAZ specimen had a higher volume fraction of bainite and finer grain size of acicular ferrite than those of the 1/2 thickness (1/2t) location HAZ specimen because of the post heat effect during the continuous FCAW process. The Charpy impact energy at $-20^{\circ}C$ of the 1/4t location HAZ specimen was lower than that of the 1/2t location HAZ specimen because of the high volume fraction of coarse bainite. The Charpy impact energy at -40 and $-60^{\circ}C$ of the 1/2t location HAZ specimen were higher than those of the 1/2t location HAZ specimen because the ductile fracture occurred in the fine acicular ferrite and martensite regions. In the ductile fracture mode, the deformed regions were observed in fine acicular ferrite and martensite regions. In the brittle fracture mode, long crack propagation path was observed in bainite regions.

Acknowledgement

Grant : Development of steel application technologies against ice-induced crashworthiness and artic temperature high toughness, The Competency Development Program for Industry Specialist

Supported by : Korea Evolution Institute of Industrial Technology (KEIT), Korea Institute for Advancement of Technology (KIAT)

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