20CrMn钢双辊薄带振动铸轧细晶机理试验
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摘要
为了改善传统双辊薄带铸轧板坯中存在的缩孔、裂纹、组织不均以及晶粒粗大等缺陷,提升双辊薄带铸轧产品带坯的力学性能,提出振动铸轧新技术,以细化铸轧带坯组织晶粒度,提高其力学性能。为了确定振动铸轧过程的细晶机理,分别在1 570℃和1 530℃两种开浇温度下进行20CrMn钢双辊薄带铸轧振动与非振动工况的对比试验,并对所得带坯微观组织及力学性能进行检测和分析。微观组织观察结果表明,在铸轧过程中振动可以有效细化产品带坯晶粒,其细晶机理为在凝固阶段振动可以提升熔池区形核率并促使振动侧枝晶尖端熔断,而在轧制阶段振动可以强化塑性变形区的动态再结晶;拉伸试验结果表明振动有效地改善了铸轧板坯的力学性能,开浇温度1 570℃时,沿轧制方向振动铸轧板坯较传统铸轧板坯屈服强度、抗拉强度和伸长率分别提高了12.11%、14.57%和38.9%,垂直轧制方向分别提高了7.72%、13.23%和34.8%;开浇温度1530℃时,沿轧制方向分别提高了9.22%、14.95%和31.25%,垂直轧制方向分别提高了21.36%、27.35%和42.86%。试验表明振动铸轧较传统铸轧不仅能在凝固阶段通过振动提高形核率,细化晶粒,还能在轧制段通过振动增强动态再结晶效果,改善材料微观组织结构,从而提升其力学性能。
In order to improve the comprehensive mechanical properties of the twin-roller cast-rolling strip, the concept of vibratory cast-rolling is proposed to refine the grain size of the strip. For the purpose of verifying the grain refinement effect of the vibratory cast-rolling technology and exploring its mechanism, twin-roller strip cast-rolling comparative experiments of 20 CrMn steel under the condition of vibratory and non-vibration are carried out at two casting temperatures of 1 570 ℃ and 1 530 ℃respectively. Then the microstructure and mechanical properties of the strips obtained from the experiments are tested and analyzed. The microstructure observation result shows that the mechanical vibration can effectively refine the grain of the cast-rolling strip. The mechanism of grain refinement is that the vibration can promote the rupture of dendrite in the vibratory side so as to increase the nucleation rate in the molten pool in the solidification stage and can promote the dynamic recrystallization of the plastic deformation zone in the rolling stage. Tensile test result shows that mechanical vibration effectively improves the mechanical properties of the cast-rolling strip.At the casting temperature of 1 570 ℃, the yield strength, tensile strength and elongation of the vibratory cast-rolling strip are respectively12.11%, 14.57%, 38.9% higher in the rolling direction and 7.72%, 13.23%, 34.8% higher in the vertical-rolling direction than that of the conventional cast-rolling strip.At the casting temperature of 1 530 ℃, the yield strength, tensile strength and elongation of the vibratory cast-rolling strip are respectively 9.22%, 14.95%, 31.25% higher in the rolling direction and 21.36%, 27.35%, 42.86%higher in the vertical-rolling direction than that of the conventional cast-rolling strip. The results show that vibration casting-rolling can not only increase nucleation rate and refine grain size in solidification stage, but also enhance dynamic recrystallization effect by vibration in rolling section, improve microstructure of material and enhance mechanical properties.
In order to improve the comprehensive mechanical properties of the twin-roller cast-rolling strip, the concept of vibratory cast-rolling is proposed to refine the grain size of the strip. For the purpose of verifying the grain refinement effect of the vibratory cast-rolling technology and exploring its mechanism, twin-roller strip cast-rolling comparative experiments of 20 CrMn steel under the condition of vibratory and non-vibration are carried out at two casting temperatures of 1 570 ℃ and 1 530 ℃respectively. Then the microstructure and mechanical properties of the strips obtained from the experiments are tested and analyzed. The microstructure observation result shows that the mechanical vibration can effectively refine the grain of the cast-rolling strip. The mechanism of grain refinement is that the vibration can promote the rupture of dendrite in the vibratory side so as to increase the nucleation rate in the molten pool in the solidification stage and can promote the dynamic recrystallization of the plastic deformation zone in the rolling stage. Tensile test result shows that mechanical vibration effectively improves the mechanical properties of the cast-rolling strip.At the casting temperature of 1 570 ℃, the yield strength, tensile strength and elongation of the vibratory cast-rolling strip are respectively12.11%, 14.57%, 38.9% higher in the rolling direction and 7.72%, 13.23%, 34.8% higher in the vertical-rolling direction than that of the conventional cast-rolling strip.At the casting temperature of 1 530 ℃, the yield strength, tensile strength and elongation of the vibratory cast-rolling strip are respectively 9.22%, 14.95%, 31.25% higher in the rolling direction and 21.36%, 27.35%, 42.86%higher in the vertical-rolling direction than that of the conventional cast-rolling strip. The results show that vibration casting-rolling can not only increase nucleation rate and refine grain size in solidification stage, but also enhance dynamic recrystallization effect by vibration in rolling section, improve microstructure of material and enhance mechanical properties.
引文
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[2]KIM J.Interfacial heat transfer of a single belt casting process[D].Montréal:Mc Gi U University,2000.
[3]DING P D,JIANG B,YANG C M,et al.Development and thought of thin strip continuous casting[J].The Chinese Journal of Nonferrous Metals,2004,14(S1):192-196.
[4]刘振宇,王国栋.钢的薄带铸轧技术的最新进展及产业化方向[J].鞍钢技术,2008(5):1-8.LIU Zhenyu,WANG Guodong.The latest development of thin strip casting and rolling technology and industrialization direction[J].Angang Technology,2008(5):1-8.
[5]乐鹏,毛大恒,李建平,等.电磁-超声能场对3003铝合金铸轧组织和性能的影响[J].中国有色金属学报,2014,24(3):615-623.LE Peng,MAO Daheng,LI Jianping,et al.Effect of electromagnetic-ultrasonic energy-field on structure and properties of roll-casting 3003 aluminum alloy strips[J].Chinese Journal of Nonferrous Metals,2014,24(3):615-623.
[6]RAMIREZ A,MA Q,DAVIS B.Potency of high-intensity ultrasonic treatment for grain refinement of magnesium alloys[J].Scripta Materialia,2008,9:19-22.
[7]NAKADA M,SHIOHARA Y,FLEMINGS M C.Modification of solidification structure by pulse electric discharging[J].ISIJ International,1990,30(1):27-33.
[8]杜凤山,许志强,路鹏程,等.振动式双辊薄带铸轧机:中国,CN101181719[P].2008.DU Fengshan,XU Zhiqiang,LU Chengpeng,et al.Oscillatory type double roll strip casting mill:CN,CN101181719 A[P].2008.
[9]GUAN R G,CAO F R,CHEN L Q C,et al.Dynamical solidification behaviors and microstructural evolution during vibrating wavelike sloping plate process[J].Journal of Materials Processing Technology,2009,209(5):2592-2601.
[10]KOCATEPE K.Effect of low frequency vibration on porosity of LM25 and LM6 alloys[J].Materials and Design,2007,28(6):1767-1775.
[11]FARSHID T,HASAN S,YOUSEFHK K.Study on the effect of prolonged mechanical vibration on the grain refinement and density of A356 aluminum alloy[J].Materials&Design,2009,30(5):1604-1611.
[12]ABOUTORABI A,ASSEMPOUR A,AFRASIABH.Analytical approach for calculating the sheet output curvature in asymmetrical rolling:In the case of roll axis displacement as a new asymmetry factor[J].International Journal of Mechanical Sciences,2016,105(1):11-22.
[13]ALI P,FRSHID A.Slab analysis of asymmetrical clad sheet bonded before rolling process[J].International Journal of Advanced Manufacturing Technology,2016,65(7):1-14.
[14]ZHANG S H,ZHAO D W,GAO C R,et al.Analysis of asymmetrical sheet rolling by slab method[J].International Journal of Mechanical Sciences,201265(10):168-176.
[15]PENG C,MAO D,HUANG M.Texture and property of thin roll casting aluminium sheets under high speed[J].Mining&Metallurgical Engineering,2002,1(3):101-103.
[16]库尔兹,费希尔,李建国,等.凝固原理[M].北京:高等教育出版社,2010.KURTZ,FISHER,LI Jianguo,et al.Solidification principle[M].Beijing:Higher Education Press,2010.