弛豫时间对高强热轧双相钢组织性能的影响
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摘要
基于合金减量化原则,采用以超快冷技术为核心的新一代TMCP技术制备了600 MPa级热轧双相钢,研究了弛豫时间对试验钢组织性能的影响。研究表明:随着弛豫时间增加,试验钢铁素体晶粒尺寸和体积分数均增加,屈服强度降低,伸长率增加;组织中马氏体均以长条马氏体为主,并由块状向小岛状转变,其体积分数减少,抗拉强度降低;屈强比先减小后增加,n值先增加后减小。弛豫时间对铁素体和马氏体的体积分数及内部结构有影响。8 s弛豫的试验钢,组织中大量的长条马氏体及两相间较宽的过渡区提高了材料的位错密度和均匀变形能力,其铁素体体积分数为82.2%,铁素体晶粒尺寸为5.1μm,抗拉强度达到625MPa,伸长率为27.0%,屈强比最低为0.56,n值高达0.20,综合性能最好。
Based on the principle of alloy reduction,a 600 MPa hot rolled dual phase steel was prepared by a new generation of TMCP technology with ultrafast cooling as the core technology,and the effect of relaxation time on microstructure and properties of the tested steel was studied.The results show that with the increasing of relaxation time,the grain size and volume fraction of ferrite of the steel increase,the yield strength decreases and the elongation increases;the martensite in the microstructure is dominated by lath martensite and changes from block to small island,and the volume fraction of the martensite and the tensile strength of the steel decreases;the ratio of yield strength and tensile strength decreases first and then increases,and the n value increases first and then decreases.The volume fraction and internal structure of ferrite and martensite are affected by relaxation time.When the relaxation time is 8 s,the dislocation density and uniform deformation ability of the steel are improved by a large number of lath martensite in the microstructure and a wide transition zone between the two phases,and the ferrite volume fraction,ferrite grain size,tensile strength,elongation,yield ratio and n value of the steel are 82.2%,5.1 μm,625 MPa,27.0%,0.56 and 0.20,respectively.
Based on the principle of alloy reduction,a 600 MPa hot rolled dual phase steel was prepared by a new generation of TMCP technology with ultrafast cooling as the core technology,and the effect of relaxation time on microstructure and properties of the tested steel was studied.The results show that with the increasing of relaxation time,the grain size and volume fraction of ferrite of the steel increase,the yield strength decreases and the elongation increases;the martensite in the microstructure is dominated by lath martensite and changes from block to small island,and the volume fraction of the martensite and the tensile strength of the steel decreases;the ratio of yield strength and tensile strength decreases first and then increases,and the n value increases first and then decreases.The volume fraction and internal structure of ferrite and martensite are affected by relaxation time.When the relaxation time is 8 s,the dislocation density and uniform deformation ability of the steel are improved by a large number of lath martensite in the microstructure and a wide transition zone between the two phases,and the ferrite volume fraction,ferrite grain size,tensile strength,elongation,yield ratio and n value of the steel are 82.2%,5.1 μm,625 MPa,27.0%,0.56 and 0.20,respectively.
引文
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[3]Mein A,Fourlaris G,Crowther D,et al.The influence of aluminium on the ferrite formation and microstructural development in hot rolled dual-phase steel[J].Materials Characterization,2012,64:69-78.
[4]Fereiduni E,Ghasemi Banadkouki S S.Ferrite hardening response in a low alloy ferrite-martensite dual phase steel[J].Journal of Alloys and Compounds,2014,589:288-294.
[5]刘学伟,赵楠.600 MPa级热轧双相钢组织与性能优化分析[J].钢铁,2017,52(1):87-91.LIU Xue-wei,ZHAO Nan.Microstructure and properties optimization of hot rolled 600 MPa dual phase steel[J].Iron and Steel,2017,52(1):87-91.
[6]谷海容,赵征志,赵爱民,等.冷却工艺参数对600 MPa级热轧双相钢组织和性能的影响[J].金属热处理,2016,41(11):79-83.GU Hai-rong,ZHAO Zheng-zhi,ZHAO Ai-min,et al.Effect of cooling processing parameters on microstructure and properties of600 MPa grade hot-rolled dual phase steel[J].Heat Treatment of Metals,2016,41(11):79-83.
[7]Leeuwen Y V,Onink M,Sietsma J.The gamma alpha transformation kinetics of low carbon steel under ultra fast cooling conditions.[J].ISIJ International,2001,41(9):1037-1046.
[8]周乐育,张丹,蒋波,等.高强度热轧双相钢分段相变行为及性能[J].材料热处理学报,2014,35(4):116-120.ZHOU Le-yu,ZHANG Dan,JIANG Bo,et al.Transformation behavior and properties of high strength hot-rolled dual phase steel[J].Transactions of Materials and Heat Treatment,2014,35(4):116-120.
[9]Asadi M,De B C,Palkowski H.Influence of martensite volume fraction and cooling rate on the properties of thermomechanically processed dual phase steel[J].Materials Science and Engineering A,2012,538:42-52.
[10]刘宗昌,任慧平,宋义全.金属固态相变教程[M].北京:冶金工业出版社,2003.
[11]张红梅,孙彬斌,贾志伟,等.热轧双相钢显微组织和力学性能[J].材料热处理学报,2007,28(4):78-82.ZHANG Hong-mei,SUN Bin-bin,JIA Zhi-wei,et al.Microstructure and mechanical properties of as-hot rolled dual-phase steel[J].Transactions of Materials and Heat Treatment,2007,28(4):78-82.
[12]Chen C Y,Yen H W,Kao F H.Precipitation hardening of high strength low-alloy steels by nanometer-sized carbides[J].Materials Science and Engineering A,2009,499:162-166.
[13]Takehide Senuma.Physical metallurgy of modern high strength steel sheets[J].ISIJ International,2001,41(6):520-532.
[14]Kuang C F,Zhang S G,Li J,et al.Effect of pre-strain and baking parameters on the microstructure and bake-hardening behavior of dualphase steel[J].International Journal of Minerals Metallurgy and Materials,2014,21(8):766-771.