Heavy steel plates for offshore structure and shipbuilding with yield strengths of approximately 690 MPa and low yield-ratio
A steel composition substantially leaner than that of HSLA-100 steel was proposed in our previous work”1-5” to produce heavy plates with thickness of - 100 mm and mechanical properties equivalent to that of the HSLA-IOO.The as quenched microstructure of the industrially produced plates consisted of fine granular bainite ( GB) and lathlike bainite ( LB).Excellent combinations of room temperature yield strength ( YS) and subzero temperature Charpy V-notch toughness (CVN) ( YS >690 MPa,CVN > 100 J at -80℃ ) were achieved across the thickness section of the plates after isothermal tempering.However,the yield ratio ( YR) of quenched and tempered plates were higher than 0.95.The present work aimed to improve the stress ratio of the plates.For that,intercritical annealing followed by water quenching ( L) was inserted between quenching and tempering ( QLT) to tailor the microstructure.Integrated industrial production trials via continuous casting,thermomechanical control rolling,and varying heat treatments were conducted.The QLT-treated microstructure of the heavy plates with increased fraction of high angle grain boundaries ( HAGBs) consists of ferrite as soft phase and tempered martensite as hard phase.The martensite formed during L treatment is strengthened by Cu-bearing precipitates after tempering.The industrially produced QLT-plate exhibits YS greater than 690 MPa,improved YR lower than 0.83,and CVN toughness higher than 150 J at - 80℃.It is also proven that direct quenching followed by L ( DQ-L) is a potential substitute for the reheating and quenching steps for efficient production of the heavy plates.
ultrahigh strength heavy plate for shipbuilding intercritical annealing and quenching strengthening and toughening
LIU Dongsheng CHENG Binggui
Institute of Research of Iron and Steel,Shasteel,Jinfeng Town,Zhangjiagang 215625,Jiangsu,China
国内会议
上海
英文
1-8
2013-06-01（万方平台首次上网日期，不代表论文的发表时间）