In this study, the effect of carbon equivalent and cooling rate on microstructure and hardness of A516 steels for pressure vessel is investigated. Six kinds of specimens are fabricated by varying carbon equivalent and cooling rate, and their microstructures and hardness levels are analyzed. Specimens with low carbon equivalent consist of ferrite and pearlite. As the cooling rate increases, the size of pearlite decreases slightly. The specimens with high carbon equivalent and rapid cooling rates of 10 and 20 oC/s consist of not only ferrite and pearlite but also bainite structure, such as granular bainite, acicular ferrite, and bainite ferrite. As the cooling rate increases, the volume fractions of bainite structure increase and the effective grain size decreases. The effective grain sizes of granular bainite, acicular ferrite, and bainitic ferrite are ~20, ~5, and ~10 μm, respectively. In the specimens with bainite structure, the volume fractions of acicular ferrite and bainitic ferrite, with small effective grains, increase as cooling rate increases, and so the hardness increases significantly.

1. 서 론
2. 실험 방법
3. 실험 결과
4. 고 찰
5. 결 론
References

• 이현욱(울산대학교 첨단소재공학과) | Hyun Wook Lee (School of Materials Science and Engineering, University of Ulsan)
• 강의구(현대제철 R&D Center) | Ui Gu Kang (Technical Research Center, Hyundai Steel Company)
• 김민수(현대제철 R&D Center) | Min Soo Kim (Technical Research Center, Hyundai Steel Company)
• 신상용(울산대학교 첨단소재공학과) | Sang Yong Shin (School of Materials Science and Engineering, University of Ulsan) Corresponding author