Effect of Intercritical Tempering Time on Microstructure and Mechanical Properties of 0.04C-5Mn Q690F Mid-thick Plate
The low-C medium-Mnmid-thick steel platewith good combination of strength and toughness can be widely used in offshore platform.A 0.04C-0.5Mn steel was subjected controlled rolling and directlywaterquenched,and then the mid-thick steel plate of 30mm thickness wasintercriticallytempered at 650℃ for 10min,20min,and 50min,respectively.The microstructure and mechanical properties were studied.The results showed that the microstructure of water-quenched mid-thick steel plate composes of lath martensite and little retained austenite.The microstructure of tempered mid-thick steel plate consisted of alternative laminate structure of tempered martensite and reversed transformed austenite.In the process of tempering,the martensite lath recrystallization occurred,and the reversed transformed austenite nucleated between the martensite lath.The yield strength,tensile strength,and elongation of 835MPa,905MPa,and 25.0% were obtained when the quenched mid-thick steel plate was tempered for 10min.Moreover,the impact absorbed energy was 198.5J and 132.4J at 20℃and -60℃,respectively.The yield strength and tensile strength decreased,while elongation and impact absorbed energy increased with the extending of tempering time.As the tempering time increasing to 50min,the yield strength and tensile strength were decreased to 660MPa and 825MPa respectively,and the elongation increased to 29.3%.The impact absorbed energy was 259.8J and 199.7J at 20℃ and -60℃,respectively.The fine tempering lath martensite enhanced the strength.The enriched carbon and manganese in reversed austenite enhanced the stability of austenite at room temperature.The metastable reversed transformed austenite played the significant role on improving toughness and plasticity.
medium Mn steel mid-thick plate microstructure mechanical properties reverse austenite
QI Xiangyu DU Linxiu HU Jun ZHAI Jianhan WU Hongyan GAO Xiuhua
The State Key Laboratory of Rolling and Automation, Northeastern University,Shenyang 110819, Liaoning, China
国际会议
成都
英文
103-106
2016-11-16（万方平台首次上网日期，不代表论文的发表时间）