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http://dx.doi.org/10.3740/MRSK.2019.29.8.511

Effect of Carbon Equivalent and Cooling Rate on Microstructure in A516 Steels for Pressure Vessel  

Lee, Hyun Wook (School of Materials Science and Engineering, University of Ulsan)
Kang, Ui Gu (Technical Research Center, Hyundai Steel Company)
Kim, Min Soo (Technical Research Center, Hyundai Steel Company)
Shin, Sang Yong (School of Materials Science and Engineering, University of Ulsan)
Publication Information
Korean Journal of Materials Research / v.29, no.8, 2019 , pp. 511-518 More about this Journal
Abstract
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 $20^{\circ}C/s$ 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 ${\sim}10{{\mu}m$, 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.
Keywords
A516 steel; carbon equivalent; cooling rate; microstructure; bainite;
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