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 oC 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 oC 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.

Abstracts
1. 서 론
2. 실험 방법
    2.1 시편 제조
    2.2 FCAW 공정 조건
    2.3 미세조직 분석
    2.4 기계적 특성 평가
3. 결과 및 고찰
    3.1 모재 미세조직 및 기계적 특성
    3.2 HAZ 미세조직
    3.3 HAZ 샤르피 충격 특성
4. 결 론
References

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