终轧温度和冷却工艺对铁素体贝氏体双相钢组织和力学性能的影响
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摘要
利用Gleeble-2000D热模拟机、550 mm轧机、扫描电镜等研究了终轧温度和冷却工艺对铁素体贝氏体双相钢组织和性能的影响。首先,在水冷-空冷-水冷模式下研究终轧温度对显微组织和力学性能影响,结果表明:随终轧温度降低,基体组织带状加剧,且铁素体形态由多边形转变为沿轧制方向变形的椭圆形;当终轧温度低于800℃时,铁素体比例明显增加,贝氏体比例下降,抗拉强度下降。其次,在850℃的终轧温度下研究了冷却工艺对显微组织和力学性能的影响,结果表明:当终轧后冷却方式为水冷时,基体组织以准多边形铁素体和针状铁素体为主,伸长率较低;终轧后采用水冷-空冷-水冷方式冷却时,基体组织以块状铁素体和贝氏体为主,伸长率较高。
Gleeble-2000 D thermal simulation machine,550 mm rolling mill and SEM were adopted to investigate the effects of finish rolling temperature and cooling process on the microstructuress and mechanical properties of ferrite and bainite dual phases steel.The effects of finish rolling temperature on microstructure and mechanical properties under the process of water cooling-air cooling-water cooling were studied firstly.The results show that the band trend of microstructure is identified by reducing the finish rolling temperature,meanwhile,the shape of ferrite changes from polygonal to oval along rolling direction;when the finish rolling temperature is lower than 800 ℃,the proportion of ferrite increases and that of bainite decreases,and the tensile strength decreases accordingly.Secondly,the effects of cooling process on microstructures and mechanical properties with finish rolling temperature of 850 ℃ were researched.The results show that the matrix microstructure is mainly quasi-ferrite and acicular ferrite after water cooling followed hot rolling immediately,which shows lower elongation.However,the matrix microstructure is mainly polygonal ferrite and bainite with cooling process of water cooling-air cooling-water cooling,which shows higher elongation.
Gleeble-2000 D thermal simulation machine,550 mm rolling mill and SEM were adopted to investigate the effects of finish rolling temperature and cooling process on the microstructuress and mechanical properties of ferrite and bainite dual phases steel.The effects of finish rolling temperature on microstructure and mechanical properties under the process of water cooling-air cooling-water cooling were studied firstly.The results show that the band trend of microstructure is identified by reducing the finish rolling temperature,meanwhile,the shape of ferrite changes from polygonal to oval along rolling direction;when the finish rolling temperature is lower than 800 ℃,the proportion of ferrite increases and that of bainite decreases,and the tensile strength decreases accordingly.Secondly,the effects of cooling process on microstructures and mechanical properties with finish rolling temperature of 850 ℃ were researched.The results show that the matrix microstructure is mainly quasi-ferrite and acicular ferrite after water cooling followed hot rolling immediately,which shows lower elongation.However,the matrix microstructure is mainly polygonal ferrite and bainite with cooling process of water cooling-air cooling-water cooling,which shows higher elongation.
引文
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[2]LEE J,LEE S J,COOMAN B C D.Effect of micro-alloying elements on the stretch-flange ability of dual phase steel[J].Materials Science&Engineering A,2012,536:231-238.
[3]蔡明晖,丁桦,张建苏,等.经济型铁素体/贝氏体高扩孔钢的组织与性能[J].钢铁,2008,43(8):77-80.CAI Minghui,DING Hua,ZHANG Jiansu,et al.Microstructures and properties of ferrite/bainite dual-phase steels with high hole-expanding ratio[J].Iron and Steel,2008,43(8):77-80.
[4]商艳,丁桦,王卫卫,等.含Nb低碳FB钢组织与扩孔性能的研究[J].钢铁,2008,43(10):74-77.SHANG Yan,DING Hua,WANG Weiwei,et al.Study of microstructure and stretch-flange-formability of low carbon FB steel with niobium[J].Iron and Steel,2008,43(10):74-77.
[5]商艳,韩庆生,郭营利,等.TMCP工艺对车轮钢组织及扩孔性能的影响[J].中国冶金,2008,18(10):15-19.SHANG Yan,HAN Qingsheng,GUO Yingli,et al.Effects of TM-CP on microstructure and stretch-flange-formability of automobile wheel steel[J].China Metallurgy,2008,18(10):15-19.
[6]李文平.汽车顶盖前横梁拉延成形工艺数值模拟分析[J].塑性工程学报,2017,24(2):118-121,127.LI Wenping.Numerical simulation analysis on drawing forming process of front cross member of automobile top cover[J].Journal of Plasticity Engineering,2017,24(2):118-121,127.
[7]刘大海,许钢碧,常春.DP780高强钢板温热成形极限图及其计算模型[J].塑性工程学报,2017,24(2):192-197.LIU Dahai,XU Gangbi,CHANG Chun.Forming limit diagram and its calculation model for DP780 high strength steel sheet at elevated temperatures[J].Journal of Plasticity Engineering,2017,24(2):192-197.
[8]余凯,程和法,陈文琳,等.扭力梁热成形过程温度与微观组织的研究[J].塑性工程学报,2017,24(3):109-114.YU Kai,CHENG Hefa,CHEN Wenlin,et al.Temperature and microstructure of torsion beam during hot forming[J].Journal of Plasticity Engineering,2017,24(3):109-114.
[9]王敏,张春,肖海峰,等.高强钢热冲压成形破裂行为的变形速率效应[J].锻压技术,2017,42(1):23-26.WANG Min,ZHANG Chun,XIAO Haifeng,et al.Influences of deformation velocity on fracture behavior of high strength steel in hot stamping forming[J].Forging&Stamping Technology,2017,42(1):23-26.
[10]杜飞,夏琴香,肖华,等.DP600高强钢板杯形件单道次拉深旋压成形质量分析[J].锻压技术,2017,42(1):54-59.DU Fei,XIA Qinxiang,XIAO Hua,et al.Analysis on forming quality of high strength steel DP600 cup-shaped part during singlepass deep drawing spinning[J].Forging&Stamping Technology,2017,42(1):54-59.
[11]庞厚君,段宏伟.60kg汽车用热轧高扩孔钢生产与应用[J].宝钢技术,2012,20(2):41-45.PANG Houjun,DUAN Hongwei.Production and application of hot-rolled high hole-expansion steel(60 kg grade)for automobile[J].Bao Steel Technology,2012,20(2):41-45.
[12]GB/T 20887.2-2010,汽车用高强度热连轧钢板及钢带.第2部分:高扩孔钢[S].GB/T 20887.2-2010,Continuously hot rolled high strength steel sheet and strip for automobile Part 2:High hole expansion steel[S].