连铸过程中金属液流动的电磁控制
|
摘要
近十年来，随着材料电磁加工技术的发展，电磁场的应用范围和途径不断地扩大。本文提出了一种新型的利用电磁制动制备两面具有不同性能的复层材料的方法，为了分析此技术的可行性，选择合理的铸造工艺，用自编的SIMPLE程序，对电磁控制下铸型内金属液的流动进行了模拟；还提出了直浇道电磁搅拌技术，用有限元分析软件ANSYS研究了电磁搅拌对直浇道内流场和温度场的影响，并选用Sn-3.5％Pb进行了连铸模拟实验。
依据磁流体动力学理论，建立了电磁控制下铸型内金属液流动的数学模型，使用交错网格技术和块修正的行迭代方法，用VC++6.0编制了流场计算的SIMPLE程序，研究了水平电磁场对金属液流动的影响。结果表明：在铸型宽度方向上施加的水平电磁场，不仅可以有效抑制出水口的流速，减少其射流深度，还可以减小铸型中心处出现的回流区；当磁感应强度B≥0.2T时，控制效果明显；为了避免施加电磁制动后在液面出现的横向流动，可设置高度20mm-30mm的挡板；均匀的速度分布还导致了铸型内均匀的温度分布；拉坯速度快时，电磁场对铸型水口区域流场控制效果好，所以电磁控制更适合于高速连铸的场合。
因此，在铸型宽度方向施加水平电磁场，从两个浸入式浇口同时浇注成分不同的合金液，通过电磁力控制铸型内金属液的流动，使两种金属液体流动平稳，不发生混流，可以生产出两面具有不同性能的复层梯度功能材料。
施加直浇道电磁搅拌可以使连铸坯的凝固组织变得细小而均匀，从实验结果分析可得：施加电磁搅拌后，铸坯的晶粒细化，等轴晶区扩大，柱状晶区减小；在降低过热度的情况下，施加电磁搅拌，可避免直浇道堵塞，保证浇注顺利进行，而且铸坯的凝固组织更加细小。
为了探讨直浇道电磁搅拌细化连铸坯凝固组织的机理，使用商用软件ANSYS5.6模拟了直浇道内的流场和温度场，得出以下结论：施加电磁搅拌后，直浇道内金属液的轴向速度基本不变，而周向速度发生显著变化，即金属液体产生了旋转运动；在相同的浇注温度下，施加电磁搅拌后，浇道内的温度分布比未施加搅拌时变得均匀，降低了直浇道堵塞的可能性，从而可以实施低温浇注。所以，施加直浇道电磁搅拌细化晶粒的原因可能有两个：一是电磁搅拌改变了浇道内金属液的流动形态，螺旋运动的熔体进入铸型后，对铸型内的金属液起到搅拌作用；二是使浇道内温度分布均匀，从而可以降低浇注温度，在较
连铸过程中金属液流动的电磁控制
小的过热度下浇注成形。
With the development of electromagnetic processing of materials, the applied range and paths of electromagnetic field has been expanding in the last ten years. A new technology, that can manufacture clad metal materials with electromagnetic brake, was put forward; In order to analyze the feasibility and choose reasonable technological parameters, the effects of electromagnetic field on molten metal flow in the mould are discussed by use of self-programming software SIMPLE. Another new technology, the nozzle electromagnetic stirring (N-EMS), was brought forward; the effects of electromagnetic stirring on flow field and temperature field in the nozzle are studied using analytic software ANSYS; the experiments of continuous casting were performed with Sn-3. 5%Pb alloy.
Based on MHD theory, mathematical model of fluid flow in the mould installed electromagnetic field was established; SIMPLE code for computing fluid field was programmed using Visual C++6.0 software, adopting interleaving mesh and iterative routine of line-by-line with block amendment; the effects of level magnetic field (LMF) on metal fluid flow were researched. The results show that by imposing LMF, discharge velocity from the nozzle is suppressed, jet length is decreased, back flow zone in the center of the mould is reduced; that control effectiveness is obvious when magnetic flux density is more than 0. 2T; that it is necessary to set dam board of about 20mm-30mm high in the upper port of the mould in order to avoid lateral flow of liquid-level due to applying EMBR; homogeneous velocity distribution results in uniform temperature distribution; when the casting speed is faster, the effectiveness of EMBR is better, so EMBR is suitable for quick-speed continuous casting.
The cast metals that have different performance on two sides can cast continuously by pouring two molten metals, of different chemical composition, because electromagnetic force can suppress the mixing of molten metals in the molten pool.
Solidification structure of continuous casting billets is improved obviously by N-EMS. The experimental results show that after applying N-EMS, crystal grains are finer, zone of equiaxial crystals enlarges, zone of dendrite crystals reduces correspondingly; continuous casting can be conducted at the lower pouring temperature and the nozzle can' t
be jammed with N-EMS.
To discuss the mechanism of grain refining by N-EMS, flow field and temperature field in the nozzle are computed with the software ANSYS. The results are as following: axial velocity distribution is almost the same with or without N-EMS, and circumferential velocity distribution has remarkable difference, in other words, after applying N-EMS, the electromagnetic force makes the molten metal in the nozzle swirling; under the same condition of pouring temperature, temperature distribution of molten metal in the nozzle is more uniform with N-EMS. The mechanism of improving solidification structure of billets is that electromagnetic force changes the flow of molten metal in the nozzle, and molten metal in the mould is stirred by rotation motion of metal flow; that temperature distribution in the nozzle is uniform, and cold pouring is implemented for lower pouring temperature.
依据磁流体动力学理论，建立了电磁控制下铸型内金属液流动的数学模型，使用交错网格技术和块修正的行迭代方法，用VC++6.0编制了流场计算的SIMPLE程序，研究了水平电磁场对金属液流动的影响。结果表明：在铸型宽度方向上施加的水平电磁场，不仅可以有效抑制出水口的流速，减少其射流深度，还可以减小铸型中心处出现的回流区；当磁感应强度B≥0.2T时，控制效果明显；为了避免施加电磁制动后在液面出现的横向流动，可设置高度20mm-30mm的挡板；均匀的速度分布还导致了铸型内均匀的温度分布；拉坯速度快时，电磁场对铸型水口区域流场控制效果好，所以电磁控制更适合于高速连铸的场合。
因此，在铸型宽度方向施加水平电磁场，从两个浸入式浇口同时浇注成分不同的合金液，通过电磁力控制铸型内金属液的流动，使两种金属液体流动平稳，不发生混流，可以生产出两面具有不同性能的复层梯度功能材料。
施加直浇道电磁搅拌可以使连铸坯的凝固组织变得细小而均匀，从实验结果分析可得：施加电磁搅拌后，铸坯的晶粒细化，等轴晶区扩大，柱状晶区减小；在降低过热度的情况下，施加电磁搅拌，可避免直浇道堵塞，保证浇注顺利进行，而且铸坯的凝固组织更加细小。
为了探讨直浇道电磁搅拌细化连铸坯凝固组织的机理，使用商用软件ANSYS5.6模拟了直浇道内的流场和温度场，得出以下结论：施加电磁搅拌后，直浇道内金属液的轴向速度基本不变，而周向速度发生显著变化，即金属液体产生了旋转运动；在相同的浇注温度下，施加电磁搅拌后，浇道内的温度分布比未施加搅拌时变得均匀，降低了直浇道堵塞的可能性，从而可以实施低温浇注。所以，施加直浇道电磁搅拌细化晶粒的原因可能有两个：一是电磁搅拌改变了浇道内金属液的流动形态，螺旋运动的熔体进入铸型后，对铸型内的金属液起到搅拌作用；二是使浇道内温度分布均匀，从而可以降低浇注温度，在较
连铸过程中金属液流动的电磁控制
小的过热度下浇注成形。
With the development of electromagnetic processing of materials, the applied range and paths of electromagnetic field has been expanding in the last ten years. A new technology, that can manufacture clad metal materials with electromagnetic brake, was put forward; In order to analyze the feasibility and choose reasonable technological parameters, the effects of electromagnetic field on molten metal flow in the mould are discussed by use of self-programming software SIMPLE. Another new technology, the nozzle electromagnetic stirring (N-EMS), was brought forward; the effects of electromagnetic stirring on flow field and temperature field in the nozzle are studied using analytic software ANSYS; the experiments of continuous casting were performed with Sn-3. 5%Pb alloy.
Based on MHD theory, mathematical model of fluid flow in the mould installed electromagnetic field was established; SIMPLE code for computing fluid field was programmed using Visual C++6.0 software, adopting interleaving mesh and iterative routine of line-by-line with block amendment; the effects of level magnetic field (LMF) on metal fluid flow were researched. The results show that by imposing LMF, discharge velocity from the nozzle is suppressed, jet length is decreased, back flow zone in the center of the mould is reduced; that control effectiveness is obvious when magnetic flux density is more than 0. 2T; that it is necessary to set dam board of about 20mm-30mm high in the upper port of the mould in order to avoid lateral flow of liquid-level due to applying EMBR; homogeneous velocity distribution results in uniform temperature distribution; when the casting speed is faster, the effectiveness of EMBR is better, so EMBR is suitable for quick-speed continuous casting.
The cast metals that have different performance on two sides can cast continuously by pouring two molten metals, of different chemical composition, because electromagnetic force can suppress the mixing of molten metals in the molten pool.
Solidification structure of continuous casting billets is improved obviously by N-EMS. The experimental results show that after applying N-EMS, crystal grains are finer, zone of equiaxial crystals enlarges, zone of dendrite crystals reduces correspondingly; continuous casting can be conducted at the lower pouring temperature and the nozzle can' t
be jammed with N-EMS.
To discuss the mechanism of grain refining by N-EMS, flow field and temperature field in the nozzle are computed with the software ANSYS. The results are as following: axial velocity distribution is almost the same with or without N-EMS, and circumferential velocity distribution has remarkable difference, in other words, after applying N-EMS, the electromagnetic force makes the molten metal in the nozzle swirling; under the same condition of pouring temperature, temperature distribution of molten metal in the nozzle is more uniform with N-EMS. The mechanism of improving solidification structure of billets is that electromagnetic force changes the flow of molten metal in the nozzle, and molten metal in the mould is stirred by rotation motion of metal flow; that temperature distribution in the nozzle is uniform, and cold pouring is implemented for lower pouring temperature.
引文
1．田乃媛主编．薄板坯连铸连轧．北京：冶金工业出版社，1998，5-6
2．舍克里著，彭一川等译．冶金中的流体流动现象．北京：冶金工业出版社，1985，175-203
3．韩至成编泽．电磁流体力学在冶金生产中的应用．国外钢铁，1987，(5)：27-39
4．韩至成著．电磁冶金学．北京：冶金工业出版社，2001，1-16
5. Asai S. Matall. Appliance Magneto-hydro-dynamic. Proceedings of a IUTAM Symposium, The Metal Society, 1984, 224
6．李廷举等．电磁场作用下材料加工新技术．大连理工大学学报，2000，40增刊：961-964
7．周士平等．钢的电磁铸造，钢铁，1994，29(12)：71-74
8．刘薇等．连铸工艺中的电磁搅拌技术．炼钢，1999，15(1)：53-56
9．徐国兴等．电磁搅拌技术在连铸机上的应用及其对铸坯质量的改善．上海金属，1997，19(3)：28-33
10．王军等．连铸工艺中的电磁技术．宽厚板，1999，6(3)：18-21
11. Tingju Li, etc. Surface Quality Improvement of Continuously Cast Metals by Imposing Intermittent High Frequency Magnetic Field and Synchronizing the Field with Mold Oscillation. ISIJ International, 1996, 36(4): 410-416
12. K.H. Spitzer, etc. Multi-Frequency Electromagnetic Stirring of Liquid Metals. ISIJ International, 1996, 36(5): 487-492
13．王学东等．电磁搅拌技术的国内外发展现状．辽宁工程技术大学学报(自然科学版)，2000，20(1)：82-83
14．S．Kumstreich，etc．小方坯和大方坯电磁搅拌(EMS)技术现状和指南．法国ROTELEC(罗德瑞克)电磁搅拌公司中国总代理
15. S. YOKOYA, etc. Swirling Effect in Immersion Nozzle on Flow and Heat Transport in Billet Continuous Casting Mold. ISIJ International, 1998, 38(8): 827-833
16. S. YOKOYA, etc. Swirling Flow Effect in Immersion Nozzle on Flow in Slab Continuous Casting Mold. ISIJ International, 2000, 40(6): 578-583
17. S. YOKOYA, etc. Development of Swirling Flow Generator in Immersion Nozzle. ISIJ International, 2000, 40(6): 584-588
18. S. YOKOYA, etc. Swirling Flow Control in Immersion Nozzle for Continuous Casting Process. ISIJ International, 2001, 41(S): S47-S51
19. S. Koshima, etc. Steel Flow in a High Speed Continuous Slab Using an Electromagnetic Brake. Iron and Steel Engineer, 1984, 11(5): 41-47
20. Anders F. Lehman, etc. Fluid Flow Control in Continuous Casting Using Various Configurations of Static Magnetic Fields. International Symposium on Electromagnetic Processing of Materials '94. Nogoya, Japan: ISIJ, 1994, P372-377
21. Dirk W. van de r Plas, etc. Metallurgical Investigations of the EMBR on Slab Caster No.22 at Hoogovens Ijmuiden. International Symposium on Electromagnetic Processing of Materials '94. Nogoya, Japan: ISIJ, 1994, P384-389
22. Akira Idogawa, etc, Control of Molten Steel Flow in Continuous Casting Mold by Two Static Magnetic Fields Imposed on Whole Width. International Symposium on Electromagnetic Processing of Materials '94. Nogoya, Japan: ISIJ, 1994, P378-383
23．李宝宽等．薄板坯连铸结晶器内流场电磁制动的模拟研究[J]．金属学报，1997，33(11)：1207-1214
24．干勇等．电磁制动对薄板坯连铸结晶器内流动及传热的影响[A]．第二届全国连铸电磁会议搅拌技术研讨会论文集[C]，庐山，1998：129-139
25．孙德勤等．双金属复合材料铸造工艺研究进展．铸造，1999，(12)：48-51
26. Eiichi Takeuchi, etc. MHD Analysis in Hydro-magnetic Casting Process of Clad Steel Slabs. International Symposium on Electromagnetic Processing of Materials '94. Nogoya, Japan: ISIJ, 1994, P364-371
27. Hwang W.S. Fluid Flow Modeling for Computer-aided Design of Castings. Journal of Metals, 1983(8): 22-29
28. Desai P.V. Computer Simulation of Forced and Natural Convection During Filling of a Casting. AFS Transactions, 1984: 519-528
29. Hwang W.S. Computer Simulation for the Filling of Castings. AFS Transactions, 1987: 425-430
30. Jonsson P. Fluid Phenomena in the Filling of Cylindrical Molds Using Newtonian and Non-Newtonian Fluids. AFS Transactions, 1991: 291-297
31. Lin H.J. Combined Fluid Flow and Heat Transfer Analysis for the Filling of Castings. AFS Transactions, 1988: 447-458
32. Upadhya G. Comprehensive Casting Analysis Model Using a Geometry Based Technique Flowed by Fully Coupled, 3-D Fluid-Flow, Heat Transfer and Solidification Kinetics
33．张凯锋等．材料热加工过程的数值模拟．哈尔滨：哈尔滨工业大学出版社，2001，96-99
34．王楚等编．电磁学．北京：北京大学出版社，2000，209-210
35．浅井滋生著．入门材料电磁．日本：内田老鹤圃，2000，15-18
36．周永东．柱状钢电磁连铸结晶器系统的磁场模拟分析．大连理工大学硕士学位论文，2001，26-29
37．雷银照编著．轴对称线圈磁场计算．北京：中国计量出版社，1991，106-115，234-240
38．章梓雄等编著．粘性流体力学．北京：清华大学出版社，1998，274
39．张政译．传热与流体流动的数值计算．北京：科学出版社，1984
40．李宝宽等编著．炼钢中的计算流体力学．北京：冶金工业出版社，1998，98-138
41．贺友多编著．传输过程的数值方法．北京：冶金工业出版社，1991，131-132
42．彭大暑等．金属层状复合材料的研究状况与展望．材料学报，2000，14(4)：23-24
43．张小平等编著．近终形连铸技术．北京：冶金工业出版社，2001，144-145
44. Fumitaka Tsukihashi, etc. Effect of Static Magnetic Field Application on the Mass Transfer in Sequence Slab Continuous Casting Process. ISIJ international, 2001, 41(8): 844-850
45. Deok-Soo Kim, etc. Numerical Simulation of the Coupled Turbulent Flow and Macroscopic Solidification in Continuous Casting with Electromagnetic Brake. ISIJ international, 2000, 40(7): 670-676
46．金属．日本金属学会编．日本：丸善株式会社，1993，13-15
47．徐广隽，赫冀成．恒稳磁场控制连铸结晶器内钢液流场热模拟实验．东北大学学报(自然科学版)，2001，22(1)：83-86
48．木松秀等．连续铸造方法．平3-254338
49．贺友多编．传输过程的数值方法．北京：冶金工业出版社，1991，200-210
50．ANSYS基本过程手册．美国，ANSYS公司
51．ANSYS耦合场分析指南．美国，ANSYS公司
2．舍克里著，彭一川等译．冶金中的流体流动现象．北京：冶金工业出版社，1985，175-203
3．韩至成编泽．电磁流体力学在冶金生产中的应用．国外钢铁，1987，(5)：27-39
4．韩至成著．电磁冶金学．北京：冶金工业出版社，2001，1-16
5. Asai S. Matall. Appliance Magneto-hydro-dynamic. Proceedings of a IUTAM Symposium, The Metal Society, 1984, 224
6．李廷举等．电磁场作用下材料加工新技术．大连理工大学学报，2000，40增刊：961-964
7．周士平等．钢的电磁铸造，钢铁，1994，29(12)：71-74
8．刘薇等．连铸工艺中的电磁搅拌技术．炼钢，1999，15(1)：53-56
9．徐国兴等．电磁搅拌技术在连铸机上的应用及其对铸坯质量的改善．上海金属，1997，19(3)：28-33
10．王军等．连铸工艺中的电磁技术．宽厚板，1999，6(3)：18-21
11. Tingju Li, etc. Surface Quality Improvement of Continuously Cast Metals by Imposing Intermittent High Frequency Magnetic Field and Synchronizing the Field with Mold Oscillation. ISIJ International, 1996, 36(4): 410-416
12. K.H. Spitzer, etc. Multi-Frequency Electromagnetic Stirring of Liquid Metals. ISIJ International, 1996, 36(5): 487-492
13．王学东等．电磁搅拌技术的国内外发展现状．辽宁工程技术大学学报(自然科学版)，2000，20(1)：82-83
14．S．Kumstreich，etc．小方坯和大方坯电磁搅拌(EMS)技术现状和指南．法国ROTELEC(罗德瑞克)电磁搅拌公司中国总代理
15. S. YOKOYA, etc. Swirling Effect in Immersion Nozzle on Flow and Heat Transport in Billet Continuous Casting Mold. ISIJ International, 1998, 38(8): 827-833
16. S. YOKOYA, etc. Swirling Flow Effect in Immersion Nozzle on Flow in Slab Continuous Casting Mold. ISIJ International, 2000, 40(6): 578-583
17. S. YOKOYA, etc. Development of Swirling Flow Generator in Immersion Nozzle. ISIJ International, 2000, 40(6): 584-588
18. S. YOKOYA, etc. Swirling Flow Control in Immersion Nozzle for Continuous Casting Process. ISIJ International, 2001, 41(S): S47-S51
19. S. Koshima, etc. Steel Flow in a High Speed Continuous Slab Using an Electromagnetic Brake. Iron and Steel Engineer, 1984, 11(5): 41-47
20. Anders F. Lehman, etc. Fluid Flow Control in Continuous Casting Using Various Configurations of Static Magnetic Fields. International Symposium on Electromagnetic Processing of Materials '94. Nogoya, Japan: ISIJ, 1994, P372-377
21. Dirk W. van de r Plas, etc. Metallurgical Investigations of the EMBR on Slab Caster No.22 at Hoogovens Ijmuiden. International Symposium on Electromagnetic Processing of Materials '94. Nogoya, Japan: ISIJ, 1994, P384-389
22. Akira Idogawa, etc, Control of Molten Steel Flow in Continuous Casting Mold by Two Static Magnetic Fields Imposed on Whole Width. International Symposium on Electromagnetic Processing of Materials '94. Nogoya, Japan: ISIJ, 1994, P378-383
23．李宝宽等．薄板坯连铸结晶器内流场电磁制动的模拟研究[J]．金属学报，1997，33(11)：1207-1214
24．干勇等．电磁制动对薄板坯连铸结晶器内流动及传热的影响[A]．第二届全国连铸电磁会议搅拌技术研讨会论文集[C]，庐山，1998：129-139
25．孙德勤等．双金属复合材料铸造工艺研究进展．铸造，1999，(12)：48-51
26. Eiichi Takeuchi, etc. MHD Analysis in Hydro-magnetic Casting Process of Clad Steel Slabs. International Symposium on Electromagnetic Processing of Materials '94. Nogoya, Japan: ISIJ, 1994, P364-371
27. Hwang W.S. Fluid Flow Modeling for Computer-aided Design of Castings. Journal of Metals, 1983(8): 22-29
28. Desai P.V. Computer Simulation of Forced and Natural Convection During Filling of a Casting. AFS Transactions, 1984: 519-528
29. Hwang W.S. Computer Simulation for the Filling of Castings. AFS Transactions, 1987: 425-430
30. Jonsson P. Fluid Phenomena in the Filling of Cylindrical Molds Using Newtonian and Non-Newtonian Fluids. AFS Transactions, 1991: 291-297
31. Lin H.J. Combined Fluid Flow and Heat Transfer Analysis for the Filling of Castings. AFS Transactions, 1988: 447-458
32. Upadhya G. Comprehensive Casting Analysis Model Using a Geometry Based Technique Flowed by Fully Coupled, 3-D Fluid-Flow, Heat Transfer and Solidification Kinetics
33．张凯锋等．材料热加工过程的数值模拟．哈尔滨：哈尔滨工业大学出版社，2001，96-99
34．王楚等编．电磁学．北京：北京大学出版社，2000，209-210
35．浅井滋生著．入门材料电磁．日本：内田老鹤圃，2000，15-18
36．周永东．柱状钢电磁连铸结晶器系统的磁场模拟分析．大连理工大学硕士学位论文，2001，26-29
37．雷银照编著．轴对称线圈磁场计算．北京：中国计量出版社，1991，106-115，234-240
38．章梓雄等编著．粘性流体力学．北京：清华大学出版社，1998，274
39．张政译．传热与流体流动的数值计算．北京：科学出版社，1984
40．李宝宽等编著．炼钢中的计算流体力学．北京：冶金工业出版社，1998，98-138
41．贺友多编著．传输过程的数值方法．北京：冶金工业出版社，1991，131-132
42．彭大暑等．金属层状复合材料的研究状况与展望．材料学报，2000，14(4)：23-24
43．张小平等编著．近终形连铸技术．北京：冶金工业出版社，2001，144-145
44. Fumitaka Tsukihashi, etc. Effect of Static Magnetic Field Application on the Mass Transfer in Sequence Slab Continuous Casting Process. ISIJ international, 2001, 41(8): 844-850
45. Deok-Soo Kim, etc. Numerical Simulation of the Coupled Turbulent Flow and Macroscopic Solidification in Continuous Casting with Electromagnetic Brake. ISIJ international, 2000, 40(7): 670-676
46．金属．日本金属学会编．日本：丸善株式会社，1993，13-15
47．徐广隽，赫冀成．恒稳磁场控制连铸结晶器内钢液流场热模拟实验．东北大学学报(自然科学版)，2001，22(1)：83-86
48．木松秀等．连续铸造方法．平3-254338
49．贺友多编．传输过程的数值方法．北京：冶金工业出版社，1991，200-210
50．ANSYS基本过程手册．美国，ANSYS公司
51．ANSYS耦合场分析指南．美国，ANSYS公司