冷却速率对Ti-V-Mo复合微合金钢组织转变及力学性能的影响
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摘要
利用OM、EBSD、HRTEM和Vickers硬度计等手段研究了冷却速率对Ti-V-Mo复合微合金钢组织转变、析出相及硬度的影响,阐明了(Ti,V,Mo)C在不同冷却速率下的析出规律及其对显微组织和硬度的作用机理。结果表明,当冷却速率低于20℃/s时,随着冷却速率的增加,析出相平均尺寸由13.2 nm逐渐减小至6.9 nm,铁素体平均晶粒尺寸由5.06 mm逐渐细化至2.97 mm,硬度呈先快速增大而后缓慢增大的趋势,铁素体的细晶强化和(Ti,V,Mo)C的沉淀强化是硬度升高的主要因素;冷却速率为20~30℃/s,其对晶粒细化和沉淀强化的影响效果已趋于饱和,硬度基本保持不变,此时Ti-V-Mo复合微合金钢的硬度具有最大值410 HV,屈服强度高达1090 MPa。Ti-V-Mo复合微合金钢的硬度y与冷却速率x符合指数衰减关系:y=-229exp(-x/5)+412。
Nanoscale co-precipitation strengthening in steels has attracted increasing attention in recent years and has become a new cornerstone for the development of advanced high performance steels with superior combination of strength and ductility. Rolling process, finishing temperature, cooling rate and coiling temperature are the main factors which affect the mechanical properties of microalloyed steels by changing the volume fraction and particle size of precipitates. Nevertheless, the influence of cooling rate on microstructure evolution, precipitates and mechanical properties of complex microalloyed ferritic Ti-V-Mo steel has been rarely reported. In this work, the precipitation law of(Ti, V, Mo)C carbides at different cooling rates and its effect on microstructue evolution and mechanical properties of Ti-V-Mo complex miroalloyed steel were studied by OM, EBSD, HRTEM and Vickers-hardness test. The results indicated that the hardness first increased quickly and then increased slowly as the cooling rate increased(lower than 20 ℃/s); the mean size of(Ti, V, Mo)C particles decreased from 13.2 nm to 6.9 nm and the average size of ferrite grain reduced from 5.06 mm to 2.97 mm; the hardness of Ti-V-Mo steel was improved by the means of grain refinement hardening and precipitation hardening. However, when the cooling rate increased from 20 ℃/s to 30 ℃/s, its effects on grain refinement hardening and precipitation hardening has become saturated, so the hardness was kept flat and achieved a maximum vlaue of 410 HV,and the yield strength reached as high as 1090 MPa. The hardness y of Ti-V-Mo microalloyed steel and cooling rates x accord with a exponential decay relationship: y=-229 exp(-x/5)+412.
Nanoscale co-precipitation strengthening in steels has attracted increasing attention in recent years and has become a new cornerstone for the development of advanced high performance steels with superior combination of strength and ductility. Rolling process, finishing temperature, cooling rate and coiling temperature are the main factors which affect the mechanical properties of microalloyed steels by changing the volume fraction and particle size of precipitates. Nevertheless, the influence of cooling rate on microstructure evolution, precipitates and mechanical properties of complex microalloyed ferritic Ti-V-Mo steel has been rarely reported. In this work, the precipitation law of(Ti, V, Mo)C carbides at different cooling rates and its effect on microstructue evolution and mechanical properties of Ti-V-Mo complex miroalloyed steel were studied by OM, EBSD, HRTEM and Vickers-hardness test. The results indicated that the hardness first increased quickly and then increased slowly as the cooling rate increased(lower than 20 ℃/s); the mean size of(Ti, V, Mo)C particles decreased from 13.2 nm to 6.9 nm and the average size of ferrite grain reduced from 5.06 mm to 2.97 mm; the hardness of Ti-V-Mo steel was improved by the means of grain refinement hardening and precipitation hardening. However, when the cooling rate increased from 20 ℃/s to 30 ℃/s, its effects on grain refinement hardening and precipitation hardening has become saturated, so the hardness was kept flat and achieved a maximum vlaue of 410 HV,and the yield strength reached as high as 1090 MPa. The hardness y of Ti-V-Mo microalloyed steel and cooling rates x accord with a exponential decay relationship: y=-229 exp(-x/5)+412.
引文
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[16]Xu Y,Sun M X,Zhou Y L,et al.Precipitation behavior of(Nb,Ti)Cin coiling process and its effect on micro-mechanical characteristics of ferrite[J].Acta Metall.Sin.,2015,51:31(徐洋,孙明雪,周砚磊等.(Nb,Ti)C在轧后卷取中的析出及对铁素体相微观力学特征的影响[J].金属学报,2015,51:31)
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[18]Zajac S,Siwecki T,Hutchinson B,et al.Recrystallization controlled rolling and accelerated cooling for high strength and toughness in V-Ti-N steels[J].Metall.Mater.Trans.,1991,22A:2681
[19]Manohar P A,Chandra T.Continuous cooling transformation behaviour of high strength microalloyed steels for linepipe applications[J].ISIJ Int.,1998,38:766
[20]Zhang K,Li Z D,Wang Z Q,et al.Precipitation behavior and mechanical properties of hot-rolled high strength Ti-Mo-bearing ferritic sheet steel:The great potential of nanometer-sized(Ti,Mo)Ccarbide[J].J.Mater.Res.,2016,31:1254
[21]Yong Q L,Ma M T,Wu B R.Microalloyed Steel─Physical and Mechanical Metallurgy[M].Beijing:China Machine Press,1989:65(雍岐龙,马鸣图,吴宝榕.微合金钢─物理和力学冶金[M].北京:机械工业出版社,1989:65)
[22]Gladman T,Mc Ivor I D,Pickering F B.Some aspects of the structure-property relationships in high-carbon ferrite-pearlite steels[J].J.Iron Steel Inst.,1972,210:916
[23]Kim Y W,Song S W,Seo S J,et al.Development of Ti and Mo micro-alloyed hot-rolled high strength sheet steel by controlling thermomechanical controlled processing schedule[J].Mater.Sci.Eng.,2013,A565:430
[24]Zhang K,Li Z D,Sun X J,et al.Development of Ti-V-Mo complex microalloyed hot-rolled 900-MPa-Grade high-strength steel[J].Acta Metall.Sin.(Engl.Lett.),2015,28:641
[25]Pavlina E J,Van Tyne C J.Correlation of yield strength and tensile strength with hardness for steels[J].J.Mater.Eng.Perform.,2008,17:888
[26]Xu Y.Study on ferrite transformation and nano-precipitation behaviors and mechanism of Ti micro-alloyed steel[D].Shenyang:Northeastern University,2015(徐洋.钛微合金化钢中铁素体相变及纳米相析出行为与机理研究[D].沈阳:东北大学,2015)
[2]Jiao Z B,Luan J H,Miller M K,et al.Co-precipitation of nanoscale particles in steels with ultra-high strength for a new era[J].Mater.Today,2017,20:142
[3]Lv Z P,Jiang S H,He J Y,et al.Second phase strengthening in advanced metal materials[J].Acta Metall.Sin.,2016,52:1183(吕昭平,蒋虽合,何骏阳等.先进金属材料的第二相强化[J].金属学报,2016,52:1183)
[4]Kim Y W,Kim J H,Hong S G,et al.Effects of rolling temperature on the microstructure and mechanical properties of Ti-Mo microalloyed hot-rolled high strength steel[J].Mater.Sci.Eng.,2014,A605:244
[5]Chen J,Lv M Y,Tang S,et al.Microstructure,mechanical properties and interphase precipitation behaviors in V-Ti microalloyed steel[J].Acta Metall.Sin.,2014,50:524(陈俊,吕梦阳,唐帅等.V-Ti微合金钢的组织性能及相间析出行为[J].金属学报,2014,50:524)
[6]Mukherjee S,Timokhina I,Zhu C,et al.Clustering and precipitation processes in a ferritic titanium-molybdenum microalloyed steel[J].J.Alloys Compd.,2017,690:621
[7]Phaniraj M.P,Shin Y M,Lee J,et al.Development of high strength hot rolled low carbon copper-bearing steel containing nanometer sized carbides[J].Mater.Sci.Eng.,2015,A633:1
[8]Li X L,Wang Z D.Interphase precipitation behaviors of nanometersized carbides in a Nb-Ti-bearing low-carbon microalloyed steel[J].Acta Metall.Sin.,2015,51:417(李小琳,王昭东.含Nb-Ti低碳微合金钢中纳米碳化物的相间析出行为[J].金属学报,2015,51:417)
[9]Chen C Y,Chen C C,Yang J R.Microstructure characterization of nanometer carbides heterogeneous precipitation in Ti-Nb and Ti-NbMo steel[J].Mater.Charact.,2014,88:69
[10]Yi H L,Du L X,Wang G D,et al.Development of Nb-V-Ti hotrolled high strength steel with fine ferrite and precipitation strengthening[J].J.Iron Steel Res.Int.,2009,16(4):72
[11]Li X L,Wang Z D,Deng X T,et al.Effect of final temperature after ultra-fast cooling on microstructural evolution and precipitation behavior of Nb-V-Ti bearing low alloy steel[J].Acta Metall.Sin.,2015,51:784(李小琳,王昭东,邓想涛等.超快冷终冷温度对含Nb-V-Ti微合金钢组织转变及析出行为的影响[J].金属学报,2015,51:784)
[12]Zhang K,Yong Q L,Sun X J,et al.Effect of coiling temperature on microstructure and mechanical properties of Ti-V-Mo complex microalloyed ultra-high strength steel[J].Acta Metall.Sin.,2016,52:529(张可,雍岐龙,孙新军等.卷取温度对Ti-V-Mo复合微合金化超高强度钢组织及力学性能的影响[J].金属学报,2016,52:529)
[13]Olasolo M,Uranga P,Rodriguez-Ibabe J M,et al.Effect of austenite microstructure and cooling rate on transformation characteristics in a low carbon Nb-V microalloyed steel[J].Mater.Sci.Eng.,2011,A528:2559
[14]Wang Q,Sun T T,Bai Y Q.Effect of cooling rate on microstructure and mechanical properties of ultra-low carbon micro-alloyed steel[J].Heat Treat.Met.,2015,40(2):148(王权,孙婷婷,白雅琼.冷却速度对超低碳微合金钢组织和性能的影响[J].金属热处理,2015,40(2):148)
[15]Ma F J,Wen G H,Tang P,et al.Effect of cooling rate on the precipitation behavior of carbonitride in microalloyed steel slab[J].Metall.Mater.Trans.,2011,42B:81
[16]Xu Y,Sun M X,Zhou Y L,et al.Precipitation behavior of(Nb,Ti)Cin coiling process and its effect on micro-mechanical characteristics of ferrite[J].Acta Metall.Sin.,2015,51:31(徐洋,孙明雪,周砚磊等.(Nb,Ti)C在轧后卷取中的析出及对铁素体相微观力学特征的影响[J].金属学报,2015,51:31)
[17]Sha Q Y,Li G Y,Yan P Y,et al.Effect of cooling rate and coiling temperature on the precipitates in ferrite of Nb-V-Ti microalloyed complex strip steel[J].Mater.China,2011,30(12):23(沙庆云,李桂艳,严平沅等.冷却速度和卷取温度对Nb-V-Ti复合微合金带钢铁素体中析出的影响[J].中国材料进展,2011,30(12):23)
[18]Zajac S,Siwecki T,Hutchinson B,et al.Recrystallization controlled rolling and accelerated cooling for high strength and toughness in V-Ti-N steels[J].Metall.Mater.Trans.,1991,22A:2681
[19]Manohar P A,Chandra T.Continuous cooling transformation behaviour of high strength microalloyed steels for linepipe applications[J].ISIJ Int.,1998,38:766
[20]Zhang K,Li Z D,Wang Z Q,et al.Precipitation behavior and mechanical properties of hot-rolled high strength Ti-Mo-bearing ferritic sheet steel:The great potential of nanometer-sized(Ti,Mo)Ccarbide[J].J.Mater.Res.,2016,31:1254
[21]Yong Q L,Ma M T,Wu B R.Microalloyed Steel─Physical and Mechanical Metallurgy[M].Beijing:China Machine Press,1989:65(雍岐龙,马鸣图,吴宝榕.微合金钢─物理和力学冶金[M].北京:机械工业出版社,1989:65)
[22]Gladman T,Mc Ivor I D,Pickering F B.Some aspects of the structure-property relationships in high-carbon ferrite-pearlite steels[J].J.Iron Steel Inst.,1972,210:916
[23]Kim Y W,Song S W,Seo S J,et al.Development of Ti and Mo micro-alloyed hot-rolled high strength sheet steel by controlling thermomechanical controlled processing schedule[J].Mater.Sci.Eng.,2013,A565:430
[24]Zhang K,Li Z D,Sun X J,et al.Development of Ti-V-Mo complex microalloyed hot-rolled 900-MPa-Grade high-strength steel[J].Acta Metall.Sin.(Engl.Lett.),2015,28:641
[25]Pavlina E J,Van Tyne C J.Correlation of yield strength and tensile strength with hardness for steels[J].J.Mater.Eng.Perform.,2008,17:888
[26]Xu Y.Study on ferrite transformation and nano-precipitation behaviors and mechanism of Ti micro-alloyed steel[D].Shenyang:Northeastern University,2015(徐洋.钛微合金化钢中铁素体相变及纳米相析出行为与机理研究[D].沈阳:东北大学,2015)