等温淬火工艺对超高强贝氏体钢组织性能影响
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摘要
针对低碳超高强贝氏体钢在不同等温淬火工艺下的组织和力学性能演变规律进行研究.结果表明:与一阶段等温淬火工艺相比,两阶段工艺下组织中贝氏体量增加,马氏体量相对减少,致使实验钢的屈服强度高达1 178 MPa,提高58%,延伸率从7. 7%升高到14. 4%,单位冲击韧性达到66 J/cm~2,提升16%.对比研究不同等温淬火工艺下实验钢的强塑性匹配发现,两阶段工艺A3(240℃等温2 h后再270℃等温1 h)条件下实验钢的强塑积可达21 888 MPa·%.通过两阶段工艺,可消除实验钢中由于Mn元素偏析造成的马氏体带,获得相对均匀的贝氏体组织,从而使得实验钢的强度和韧性同时提高.
The effect of different austempering processes on microstructure evolution and mechanical property of low carbon ultra-high strength bainitic steels was studied. The results show that compared with the one-stage austempering process,the amount of bainite increases and the content of martensite decreases in the two-stage process,which result that the yield strength of the experimental steel increases 58% and is up to 1 178 MPa,the elongation increases from 7. 7% to14. 4% and the impact toughness increases 16% and reaches 66 J/cm~2. Comparing the strength and plasticity matching of the corresponding experimental steels under different heat treatments,it is found that the product of strength and elongation of the steel can reach 21 888 MPa·% under the A3( 240 ℃ for 2 h and then 270 ℃ for 1 h) two-stage process condition. Under the two-stage process conditions,the martensite band due to Mn segregation in the steel can be eliminated and a relatively uniform bainite structure can be obtained,so that the strength and toughness of the experimental steel can be improved simultaneously.
The effect of different austempering processes on microstructure evolution and mechanical property of low carbon ultra-high strength bainitic steels was studied. The results show that compared with the one-stage austempering process,the amount of bainite increases and the content of martensite decreases in the two-stage process,which result that the yield strength of the experimental steel increases 58% and is up to 1 178 MPa,the elongation increases from 7. 7% to14. 4% and the impact toughness increases 16% and reaches 66 J/cm~2. Comparing the strength and plasticity matching of the corresponding experimental steels under different heat treatments,it is found that the product of strength and elongation of the steel can reach 21 888 MPa·% under the A3( 240 ℃ for 2 h and then 270 ℃ for 1 h) two-stage process condition. Under the two-stage process conditions,the martensite band due to Mn segregation in the steel can be eliminated and a relatively uniform bainite structure can be obtained,so that the strength and toughness of the experimental steel can be improved simultaneously.
引文
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[9] Fultz B,Kim J I,Kim Y H,et al. The stability of precipitated austenite and the toughness of 9Ni steel[J]. Metallurgical and Materials Transactions A,1985,16(12):2237-2249.
[10] Caballero F G,Bhadeshia H K D H,Mawella K J A,et al.Design of novel high strength bainitic steels:part 1[J].Materials Science and Technology,2001,17(5):512-516.
[11] Jing C N,Wang Z C,Han F T. Research progress of the influencing factors on transformation induced plasticity[J].Heat Treatment of Metals,2005,3(2):26-31.
[12] Jimenez-Melero N H, Van Dijk L, Zhao J, et al.Characterization of individual retained austenite grains and their stability in low-alloyed TRIP steels[J]. Acta Materialia,2007,55(20):6713-6723.
[13] Matsuoka Y,Iwasaki T,Nakada N,et al. Effect of grain size on thermal and mechanical stability of austenite in metastable austenite stainless steel[J]. ISIJ International,2013,53(7):1224-1230.
[2]贺信莱,尚成嘉,杨善武,等.高性能低碳贝氏体钢——成分、工艺、组织、性能与应用[M].北京:冶金工业出版社,2008.(He Xin-lai,Shang Cheng-jia,Yang Shan-wu,et al. Highperformance low-carbon bainitic steels—compositions,processes,microstructures,properties and applications[M].Beijing:M etallurgical Industry Press,2008.)
[3] Caballero F G,Bhadeshia H K D H. Very strong bainite[J].Current Opinion in Solid State Materials Science,2004,8(3):251-255.
[4]俞德刚,王世道.贝氏体相变理论[M].上海:上海交通大学出版社,1998.(Yu De-gang,Wang Shi-dao. Bainite transformation theory[M]. Shanghai:Shanghai Jiaotong University Press,1998.)
[5] Parker E R. Interrelations of compositions,transformation kinetic,morphology and mechanical properties of alloy steels[J]. Metallurgical Transaction A,1977,8(7):1025-1042.
[6] Steven W,Haynes A G. The temperature formation of martensite and bainite in low-alloy steels,some effects of chemical composition[J]. Journal of the Iron and Steel Institute,1956,183(8):349-359.
[7] Babu B N P,Bhat M S,Parker E R,et al. A rapid magnetometric technique to plot isothermal transformation diagrams[J]. Metallurgical Transaction A,1976,7(1):17-22.
[8] Lan H F,Du L X,Li Q,et al. Improvement of strengthtoughness combination in austempered low carbon bainitic steel:the key role of refining prior austensite grain size[J].Journal of Alloys and Compounds,2017,710(5):702-710.
[9] Fultz B,Kim J I,Kim Y H,et al. The stability of precipitated austenite and the toughness of 9Ni steel[J]. Metallurgical and Materials Transactions A,1985,16(12):2237-2249.
[10] Caballero F G,Bhadeshia H K D H,Mawella K J A,et al.Design of novel high strength bainitic steels:part 1[J].Materials Science and Technology,2001,17(5):512-516.
[11] Jing C N,Wang Z C,Han F T. Research progress of the influencing factors on transformation induced plasticity[J].Heat Treatment of Metals,2005,3(2):26-31.
[12] Jimenez-Melero N H, Van Dijk L, Zhao J, et al.Characterization of individual retained austenite grains and their stability in low-alloyed TRIP steels[J]. Acta Materialia,2007,55(20):6713-6723.
[13] Matsuoka Y,Iwasaki T,Nakada N,et al. Effect of grain size on thermal and mechanical stability of austenite in metastable austenite stainless steel[J]. ISIJ International,2013,53(7):1224-1230.