基于多场耦合模型的连铸结晶器内钢液凝固行为分析
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摘要
针对连铸结晶器内钢液的流动、传热、凝固耦合变化问题,应用连续介质力学和能量守恒理论,建立了板坯连铸结晶器内钢液流动、传热和凝固的三维非稳态数学模型。在此基础上,应用COMSOL软件进行数值模拟和分析。将耦合模型计算得到的凝固坯壳厚度与经验公式进行对比验证,总体符合较好。结果表明,结晶器内钢液流动的基本特征与单流场模型相比并没有发生变化。但是,钢液的上、下回流涡心到自由面的距离及流股冲击深度均有所减小。在靠近结晶器窄面的部分区域由于凝固坯壳的形成,不会出现钢液流动现象。由于凝固坯壳的存在,自由面钢液流速变大,自由面钢流波动更加剧烈。由于钢液的强制对流传热,结晶器内部钢液温度并不是由内到外逐渐降低的,而是出现了小幅度的波动。在结晶器出口处钢液温度较低,且分布不均匀,部分区域温度梯度较大。由于钢液的对流作用促进了钢液的热量传递,结晶器出口处窄面、宽面及角部凝固坯壳更厚。
A three-dimensional unsteady mathematical model of molten steel flow, heat transfer and solidification in slab continuous casting mold was developed on the basis of continuum mechanics and energy conservation theory. Using the coupling model, calculation and analysis were made with COMSOL software. The computed solidified shell thickness basically tallied with the empirical data. The results show that the basic characteristics of the molten steel flow in the mold does not change compared to the single-flow model. However, the distances of the vortex center of upper and lower recirculation regions to free surface decrease, and the steel penetrate depth decreases too. The molten steel flow phenomenon does not appear in some regions near the narrow side of the mold due to the formation of solidified shell. The steel velocity and turbulent kinetic energy on free surface increase because of the effects of solidified shell. The forced convection heat transfer causes molten steel temperature fluctuations within a narrow range, so the temperature does not gradually reduce from inside to outside in the mold. The molten steel temperature at the mold outlet is lower, the distribution is uneven, and the temperature gradient is larger in certain areas. As the molten steel convection promotes the heat transfer, solidified shell thickness at narrow side, wide side and corner is thicker.
A three-dimensional unsteady mathematical model of molten steel flow, heat transfer and solidification in slab continuous casting mold was developed on the basis of continuum mechanics and energy conservation theory. Using the coupling model, calculation and analysis were made with COMSOL software. The computed solidified shell thickness basically tallied with the empirical data. The results show that the basic characteristics of the molten steel flow in the mold does not change compared to the single-flow model. However, the distances of the vortex center of upper and lower recirculation regions to free surface decrease, and the steel penetrate depth decreases too. The molten steel flow phenomenon does not appear in some regions near the narrow side of the mold due to the formation of solidified shell. The steel velocity and turbulent kinetic energy on free surface increase because of the effects of solidified shell. The forced convection heat transfer causes molten steel temperature fluctuations within a narrow range, so the temperature does not gradually reduce from inside to outside in the mold. The molten steel temperature at the mold outlet is lower, the distribution is uneven, and the temperature gradient is larger in certain areas. As the molten steel convection promotes the heat transfer, solidified shell thickness at narrow side, wide side and corner is thicker.
引文
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[3]Szekely J,Stanek V.On heat transfer and liquid mixing in the continuous casting of steel[J].Metallurgical Transactions,1970,1(1):119-126.
[4]Thomas B G,Mika L J,Najjar F M.Simulation of fluid flow inside a continuous slab casting machine[J].Metallurgical and Materials Transaction B,1990,21(2):387-400.
[5]李宝宽,李东辉.连铸结晶器内钢液涡流现象的水模型观察和数值模拟[J].金属学报,2002,38(3):315-320.
[6]李志国,伍成波,王逢春.连铸结晶器中钢液行为数值模拟研究进展[J].铸造技术,2002,23(4):197-199.
[7]岳强,翟张霞,裴晓航,等.薄板坯连铸结晶器内钢液流动与传热及凝固耦合的数值模拟[J].过程工程学报,2015,15(2):205-211.
[8]李中原,赵九洲.平行板型薄板坯连铸结晶器中钢液流动、凝固及溶质分布的三维耦合数值模拟[J].金属学报,2006,42(2):211-217.
[9]金昕,任廷志,关杰,等.薄板坯连铸结晶器内钢液凝固行为的研究[J].铸造技术,2007,28(1):78-81.
[10]熊飞.CSP结晶器内钢液流场及温度场研究[D].重庆大学,2014.
[11]李广海.中薄板坯连铸结晶器内钢水流动、传热凝固及自由表面行为的数值模拟[D].鞍山科技大学辽宁科技大学,2004.
[12]Minakawa S,Samarasekera I V,Weinberg F.Centerline porosity in plate castings.Metallurgical and Materials Transaction B,1985,16(4):823-829.
[13]王挺.板坯连铸结晶器内流动传热和凝固收缩的数值模拟[D].西安建筑科技大学,2012.
[14]盛义平,孔祥东,杨永利.连铸结晶器传热边界条件研究[J].中国机械工程,2007,18(13):1615-1618.