Lin-Xiu Du
Northeastern University, China
Title: Microstructure and mechanical properties of a low C medium Mn heavy plate steel
Biography
Biography: Lin-Xiu Du
Abstract
Advanced heavy steel plates with combination of high strength and superior low-temperature toughness are preferred as constructural materials for ship hull, bridges, buildings, pressure vessels, and offshore structures. The medium Mn steels containing 5-8wt.% Mn are thought to have great potential. The microstructure and mechanical properties of a 0.07C-5.5wt.% Mn steel subjected to quenching and intercritically tempering was studied. The slab of 230 mm thickness was hot rolled to 50 mm plate with the start rolling and finish rolling temperature of 1050℃ and 930℃, respectively. The plate was directly water quenched to a temperature between Ms and Mf of 380℃, and then cooling slowly to room temperature in a delayed cooling pit. The quenched plate was tempered at 630℃ for 80min and 650℃ for 40min respectively. The microstructure of quenched steel consisted of martensite and retained austenite. The yield strength, tensile strength, and elongation was 805MPa, 1114MPa, and 16.7%, respectively. The impact energy at 20℃ and -20℃ was 207J and 150J. The reverse transformed austenite fromed during intercritically tempering. The yield strength and tensile strength of 650℃ tempered speciems were decreased to 650MPa and 829MPa. The elongation was increased to 26.2%. The impact energy at 20℃ and -20℃ was 223J and 157J. When the tempering temperature was 630℃, the yield strength, tensile strength, and elongation was 648MPa, 824MPa, and 24.6%, respectively. The impact energy at 20℃ and -20℃ was greatly enhanced to 239J and 207J. The change of mechanical properties was attribuated to the volume fraction and stability of austenite.