方坯连铸结晶器电磁搅拌的数值模拟

根据麦克斯韦电磁理论,利用有限元分析软件ANSYS对240 mm×280 mm方坯结晶器电磁搅拌的磁场进行数值模拟。分析电流强度、电流频率及结晶器铜管等对搅拌器内磁场分布的影响,得到了磁场特性与电磁搅拌参数的关系。研究结果表明:旋转磁场在结晶器搅拌区域内产生旋转电磁力,使钢液在水平方向形成旋转流动;磁感应强度随电流强度的增大呈线性递增;在低频搅拌条件下频率对电磁搅拌强度的影响较小,而铜管厚度对磁场强度影响较大;模拟结果与实测结果基本吻合。     

连铸结晶器电磁搅拌磁场及钢液流场模拟

 建立了大方坯连铸结晶器电磁搅拌条件下电磁场及钢液流场数学模型,开发了相应的Visual Cast仿真软件,并应用软件模拟分析了大方坯连铸结晶器内磁场、电磁力分布及双侧孔浸入式水口条件下结晶器内钢液流场的分布特征。结果表明,结晶器内磁场分布均匀,并沿横断面水平旋转,电磁力的旋转周期为磁场旋转周期的一半。电磁搅拌改变了结晶器内流场形态,减小回流区和冲击深度,有利于促进钢液中非金属夹杂物上浮排除,提高大方坯洁净度。     

Flow Modelling in Continuous Casting of Round Bloom Strands with Electromagnetic Stirring

For the majority of continuously cast semis for stringent applications such as wire rods, rails, seamless tubes, etc. an optimal cleanness, surface and sub‐surface quality as well as a minimum of centre line segregation and central shrinkage porosity is almost mandatory. In‐mould electromagnetic stirring (M‐EMS) has a number of functions but its primary purpose is to help breaking down coarse columnar dendritic solidification structure to produce a finer dendritic structure and a larger proportion of equiaxed grains. The rotary effect of M‐EMS has also an important impact on the cleanness of the steels, which can be explained by its action on exogenous and endogenous inclusions. The modelling of turbulent flow, steel temperature, solidification, exogenous inclusion transport and electromagnetic stirring with mathematical and ‐ as far as possible ‐ physical models are presented, including PIV‐measurements on a 1:1 scale water‐model of the strand.     

大方坯连铸结晶器电磁搅拌的数值模拟

对大方坯连铸结晶器电磁搅拌过程的流场和温度场进行了数值模拟,并讨论了搅拌强度对流场和温度场的影响。结果表明：在结晶器电磁搅拌下,搅拌器区域的钢液变为水平旋转,使从水口向下吐出的钢水与向上回流的钢水流股相冲突,流股侵入深度变浅,从而使轴向温度迅速降低,径向温度升高,提高了热区位置,有利于传热;搅拌强度越大,钢水的二次流现象越明显,热区位置越高。     

大圆坯结晶器电磁搅拌器磁场的数值模拟

基于有限元方法,利用ANSYS软件模拟计算了大圆坯连铸结晶器电磁搅拌(M-EMS)器内三维磁场分布,分析了铜管厚度、断面和搅拌电流、频率对磁场分布的定量影响,并通过磁场的实验测定对数学模型进行了验证.研究表明,磁场模拟结果与实测结果吻合得较好;结晶器铜管对磁场具有较强的屏蔽作用,铜管越厚,屏蔽作用越强;小断面结晶器内磁感应强度大于大断面的情况;磁感应强度随着频率的增大而减小,随电流的增大而增大.     

360 mm×450 mm方坯连铸结晶器电磁搅拌的数值模拟

根据麦克斯韦电磁理论,建立了360 mm ×450 mm方坯连铸结晶器电磁旋转搅拌的数学模型,分析了结晶器内电磁场、电磁力的分布特征以及电流(300～700 A)、搅拌频率(2.0～3.0 Hz)对电磁场和电磁力的影响.结果表明,旋转磁场在结晶器搅拌区域内产生电磁力,使钢液在水平方向形成旋转流动;磁感应强度与搅拌电流成线性关系,在低频率搅拌条件下频率对电磁搅拌强度的影响较小.     

电磁制动下结晶器内流体流动行为的数值研究

 数值模拟了在电磁制动作用下结晶器内金属液的流动行为,并研究了诸如磁感应强度,水口出口角度和磁场位置等各种操作条件对电磁制动效果的影响。数值模拟结果表明：应用电磁制动使结晶器内的流场有很大的改变。施加0.5 T的磁场使结晶器内金属液的表面流速最小,这一计算结果与实验结果十分吻合。为此,应用磁场对结晶器内的流场进行控制,有必要在一定的浇注条件下优化磁感应强度的大小。当磁感应强度、拉坯速度和水口出口角度一定时,磁场位置与水口浸入深度之比有一最佳值,可达到理想的电磁制动效果。     

Effect of Electromagnetic Stirring on Molten Steel Flow and Solidification in Bloom Mold

The effect of electromagnetic stirring on molten steel flow and heat transfer in a 260 mm× 300 mm bloom mold was investigated by using a method combining both finite element method and finite volume method. The simu lation results related to magnetic fields were consistent with the onsite measured data. The magnetic flux density in creased with increasing the current intensity but decreased with increasing the current frequency. Electromagnetic stirring caused molten steel to flow with rotation on a horizontal section and two sets of recirculation regions with opposite fellow directions in a longitudinal section formed. The maximum tangential velocity increased with increasing the current intensity and frequency. Furthermore, the superheat degree of the molten steel on the outlet cross section of the mold decreased with increasing the current intensity. growth zone of solidified shell in the effective stirring zone. bearing steel, the appropriate values of current intensity and to be 300 A and 3 Hz, respectively. Electromagnetic stirring caused the emergence of a zero For the 260 mm N 300 mm bloom continuous caster of current frequency of electromagnetic stirring were found     

Multiphase Solidification Modeling of Solidification Structure Evolution and Macrosegregation of Round Bloom Continuous Casting Process with Mold Electromagnetic Stirring and Final Electromagnetic Stirring

Based on Eulerian–Eulerian method, a 3D/2D multiphase solidification model, which takes into consideration the heat transfer and fluid flow with grains nucleation and crystal growth, is developed to predict the macrostructure evolution and macrosegregation in continuously cast round bloom. The results show that the mold electromagnetic stirring (M-EMS) can accelerate superheat dissipation and promote grain nucleation, but the horizontal swirl induced by M-EMS has a strong washing effect on the solidification front and leads to subsurface negative segregation. When the M-EMS current intensity increases from 200 to 300 A, the subsurface negative segregation ratio decreases from 0.935 to 0.875. The final electromagnetic stirring (F-EMS) not only improves the center segregation, but also leads to the formation of negative segregation zone near the round bloom center due to the enhancement of solute washing induced by F-EMS. As the F-EMS current intensity increases from 150 to 300 A, the center segregation ratio decreases from 1.148 to 1.075, and the negative segregation ratio near the strand center decreases from 0.985 to 0.977. Another phenomenon is found that the nucleation of equiaxed grain ahead of columnar tips restrains the solute diffusion and leads to a local macrosegregation in columnar-to-equiaxed transition zone.     

大方坯连铸结晶器内钢水流场的数值模拟

 采用数值模拟的方法对大方坯结晶器内钢水流动过程进行了理论计算和分析,评估了浸入式水口结构对结晶器综合冶金效果的影响,并讨论了有关工艺参数与浸入式水口结构参数的关系。结果表明,浸入式水口结构及其工艺参数对结晶器内钢水流场分布及湍流粘度分布影响显著。     

圆坯中频电磁软接触连铸结晶器内钢液流动的数值模拟

采用有限元方法模拟了中频电磁场对软接触结晶器内钢液流动的影响规律,讨论感应线圈电流强度和电源频率等因素对结晶器内钢液流动的影响。结果表明：电磁力能加强结晶器内上半部熔池的搅拌强度,并在弯月面区域形成一明显的回流区,同时还能减小钢液射流的渗入深度;增大电流强度,能加强钢液的回流和对钢液的搅拌,减小射流渗入深度,同时也加剧了钢液自由表面的波动,因而电流强度有一个最佳的控制范围;增加电源频率时,射流的渗入深度变化不大,但弯月面附近钢液的紊动能和速度都有所提高,综合考量,本研究中将频率控制在2500 Hz左右。     

板坯连铸浸入式水口出口速度对结晶器流场影响的数值模拟

以宝钢一连铸板坯结晶器为研究对象,采用大型商业软件CFX4.3,将模拟计算出的浸入式水口的出口速度直接赋给结晶器作为入口条件,计算了结晶器内钢液的流动情况.结果表明:速度矢量在水口出口截面分布不均匀、方向与水口倾角不一致.因此,有必要将水口计算结果与结晶器模型结合起来以更好地反映钢液的流动情况.     

板坯连铸结晶器内钢水流场和传热凝固数值模拟

 以鞍山钢铁集团公司中薄板坯连铸机为研究对象,利用商业软件CFX44对结晶器内钢水流场和传热凝固进行了数值模拟,主要研究了三孔浸入式水口的冶金特征及其对结晶器内钢水流场和温度场的影响。结果表明,采用三孔浸入式水口可以优化结晶器内钢水流场和温度场,稳定坯壳发育和成形,防止拉漏。     

Numerical Simulation of Electromagnetic Field and Flow Pattern in a Continuous Slab Caster with In-roll Type Strand Electromagnetic Stirring

The electromagnetic field and flow analysis model were developed to simulate the electromagnetic field and the flow pattern in a vertical curved continuous slab caster with the in-roll type strand electromagnetic stirring.The transient electromagnetic field distribution and the induced electromagnetic force were numerically described.The effects of stirring current,stirring frequency,and different stirrer configurations on the electromagnetically driven flow field in the strand were investigated and the optimization of the stirring parameters was discussed by performing a relative comparison of numerical results.Results show that the in-roller type strand electromagnetic stirrer(SEMS)pair generates the fluctuating magnetic fields,penetrating through the cast slab and periodically parallel shifting along the slab wide face with time evolution.The transient induced electromagnetic forces travels toward the magnetic flux shifting direction.Different stirring parameters(i.e.current and frequency)and stirrer configurations affect the stirring strength and the flow recirculation pattern in the strand,which are closely related to metallurgical performances of the stirrers.There is an optimum frequency to obtain the maximum stirring.The present model provides a relatively theoretical insight into the in-roll type strand electromagnetic stirring system for best operating.     

结晶器电磁搅拌对圆坯质量影响的研究

通过数值模拟计算了马钢圆坯连铸（断面尺寸为Ф450mm）电磁搅拌参数对磁场分布的影响,并通过生产试验研究了电磁搅拌参数对铸坯质量的影响。模拟计算表明,结晶器磁场强度随着搅拌电流的增加而增大,电流不变时,频率越小,磁场强度越大。现场试验表明,采用电磁搅拌能有效改善铸坯低倍组织,搅拌电流越大,铸坯中心等轴晶比率越高;电磁搅拌还能有效改善铸坯疏松和中心偏析状况。选择合适的电磁搅拌参数可以获得良好的铸坯质量。     

Solidification Structure of Continuous Casting Large Round Billets under Mold Electromagnetic Stirring

The solidification structure of a continuous casting large round billet was analyzed by a cellular-automaton-finite-element coupling model using the ProCAST software.The actual and simulated solidification structures were compared under mold electromagnetic stirring (MEMS)conditions (current of 300 A and frequency of 3 Hz).There-after,the solidification structures of the large round billet were investigated under different superheats,casting speeds,and secondary cooling intensities.Finally,the effect of the MEMS current on the solidification structures was obtained under fixed superheat,casting speed,secondary cooling intensity,and MEMS frequency.The model accurately simulated the actual solidification structures of any steel,regardless of its size and the parameters used in the continuous casting process.The ratio of the central equiaxed grain zone was found to increase with decreasing su-perheat,increasing casting speed,decreasing secondary cooling intensity,and increasing MEMS current.The grain size obviously decreased with decreasing superheat and increasing MEMS current but was less sensitive to the casting speed and secondary cooling intensity.     

重轨钢连铸结晶器电磁搅拌技术应用研究

针对大方坯连铸机投产初期重轨钢连铸电磁搅拌冶金效果不明显的问题,开展了优化重轨钢连铸结晶器电磁搅拌工艺参数的现场试验,对比研究了电磁搅拌电流强度对重轨钢铸坯中心疏松、中心偏析、等轴晶率等内部质量的影响,制定了满足攀钢重轨钢连铸工艺要求的电磁搅拌工艺制度.生产应用表明,重轨钢连铸坯内部质量明显提高,铸坯中心区等轴晶率由18.8%增至36.2%,中心疏松≤1.5级,中心偏析≤1.0级,中心缩孔≤1.0级,中心碳偏析指数≤1.05,连铸坯轧成重轨的内部质量和力学性能能够满足350 km/h高速铁路用钢轨的要求.