ESC中渣池热电耦合过程的数值模拟

电渣熔铸(ESC)过程中的渣池是一个集热场、电磁场、流场等于一体的复杂体系,各种场之间是相互影响的,且整个体系的边界条件非常复杂.本文对自耗电极、渣壳、结晶器、渣金界面等渣池热电传输边界条件作了合理的处理,同时借助于大型通用有限元分析软件ANSYS对渣池的热电场进行了模拟,获得了渣池的电场和温度场分布规律.并在此基础上研究了两种场的分布特点,提出作为熔铸过程中主要产热区的渣池是由高热源区和低热源区所组成的观点,对调整电渣熔铸过程中工艺参数、稳定熔铸过程具有一定的指导意义.     

电渣熔铸空心环形件的热电场分析

借助ANSYS-SOLID69热电耦合单元,建立等同功率空心环形件在常规工况和大电流工况下电渣熔铸时金属熔池及铸锭区域、体系的热电场物理模型。以综合分解法对其进行热电场有限元模拟,以分析其金属熔池及电流电压的关系。结果表明:金属熔池最高温在渣金界面且都比渣池最高温低约200 K,为预防深金属熔池导致的缩松缺陷应避免在大电流工况下熔铸;电流集肤效应都很显著且通常在大电流工况下电流密度大,电流密度最大区域都在自耗电极端头或底水箱附近;电位线都在渣池内密集分布且伴有方向变化;空心环形件的金属熔池形状、体系电流与等电位线均呈现非对称分布,可增加内结晶器冷却强度以弱化金属熔池内倾斜倾向。     

电渣熔铸中渣池中心高温区的模拟与实验研究

电渣熔铸是一种利用大电流通过渣池区域而产生的高温将自耗电极逐渐熔化的方法，其中渣池的温度分布特点直接决定电极的熔化速度、提纯度以及铸锭的组织结构等，是熔铸系统中的关键区域。时渣池进行了热电场耦合模拟研究，发现电极端部与金属熔池之间的渣池区域存在着一个集中的高温区，并从电场分布的角度分析了高温区产生的原因，同时进行了实验验证。为实际生产中优化工艺参数和提高生产效率提供了重要依据。     

电渣熔铸中渣池热电场的试验和模拟研究

电渣熔铸是一种利用大电流通过渣池区域而产生的高温将自耗电极逐渐熔化的方法,其中渣池的温度分布特点直接决定了电极的熔化速度、提纯度以及铸锭的组织结构等,是熔铸系统中的关键区域.本研究中采用"反向熔铸"试验和"真假双电极熔铸"试验对渣池温度场分布进行了研究,并借用具有极强的分析功能的大型通用有限元软件ANSYS软件,对试验模型进行了数值模拟.试验和模拟计算均证实了电极端部与金属熔池之间的渣池区域存在着一个集中的高温区,该高温区的存在对自耗电极的熔化起了极大的促进作用.     

基于ANSYS轧辊表面电渣加热渣池热电场模拟研究

利用大型有限元软件ANSYS,在建立轧辊表层电渣加热物理模型和数学模型的基础上,对辊芯表层加热系统特别是渣池中的电场、电位、电流密度分布、温度场、热流密度、热流梯度分布及影响因素进行了模拟研究.结果表明,在辊芯表层和电极之间存在一个强电流区,使辊芯表层被快速加热;随着电压的升高、渣池深度的增加和电极与辊芯间距的减小,渣池中的电场强度和整体温度升高,高温区集中在辊芯与电极之间;电极数量越多,系统的电场分布越均匀.研究表明辊芯表层电渣加热具有加热速度快、节能等特点.     

电渣熔铸中电极端部形状对渣池热电场模拟的影响

电渣熔铸(ESC)是一种用电加热的方法进行金属冶炼和成型的铸造方法,熔铸过程中自耗电极与渣池的接触界面是渣池能量的入口,针对平底型电极和锥底型电极两种模型进行了渣池的热电场耦合模拟,分别获得了2种模型的温度场和电场分布规律,阐述电极端部形状对熔铸过程模拟的重要性.     

固定自耗电极充填法电渣熔铸渣沟形成过程的研究

以自耗电极、渣池和铸锭为研究对象,利用大型有限元分析软件ANSYS对固定自耗电极充填法电渣熔铸的渣沟形成过程进行了数值模拟,并对其进行了实验研究。实验结果表明,当铸锭尺寸为400 mm×70 mm×200 mm时,由于固定自耗电极的熔铸电流产生了波动,铸锭侧表面形成了渣沟,在铸锭宽度方向上渣沟的深度为1.5 mm,长度为12 mm。渣沟的模拟结果与实验结果基本吻合,验证了模拟程序的准确性。根据工艺参数对渣沟形状的影响,发现自耗电极电流密度的稳定性与填充比的相互匹配是固定自耗电极充填法电渣熔铸消除渣沟形成的关键因素。     

电渣熔铸过程渣池流场的模拟研究

电渣熔铸过程中熔渣的流动决定了熔铸体系温度场的分布以及金属熔池的形状,最终影响熔铸钢锭的质量。采用大型通用有限元分析软件ANSYS,对电渣熔铸体系渣池流场进行了模拟研究,所得结果与物理模拟实验结果完全一致。并以此研究了熔铸电流,填充比和电极端部形状对熔渣流速分布的影响,为实际生产提供了依据。     

电渣熔铸过程渣池流场的模拟研究

电渣熔铸过程中熔渣的流动决定了熔铸体系温度场的分布以及金属熔池的形状，最终影响熔铸钢锭的质量。采用大型通用有限元分析软件ANSYS，对电渣熔铸体系渣池流场进行了模拟研究，所得结果与物理模拟实验结果完全一致。并以此为基础，研究了熔铸电流、填充比和电极端部形状对熔渣流速分布的影响，为实际生产提供了依据。     

Cr20Ni80电热合金电渣重熔热电场模拟

采用有限元软件ANSYS模拟了Cr20Ni80电热合金电渣重熔系统处于稳态时的热电场分布,并且研究分析了重熔系统中渣池部分和金属熔池与铸锭部分的温度、热流密度、电位以及电流密度的分布。模拟结果表明:重熔系统稳态时高温区主要集中在渣池部分;在自耗电极端部、结晶器以及渣金界面处热流密度大;系统电位基本为层状分布,自耗电极端部电位最高,电流密度也最大;从自耗电极向下,电位、电流逐渐降低,铸锭电位基本为零。试验结果表明:根据有限元模拟结果来改进生产工艺,可以改善铸锭的微观组织。     

VAR过程电弧等离子体的电磁特性研究

依据磁流体动力学及等离子体物理学理论,建立三维有限元模型对VAR过程电弧区电磁场进行数值模拟,并以此分析其对铸锭质量的影响.结果表明,熔炼电极底部的电流密度和电磁力均最大;随着径向距离的增加,熔池表面的电流密度逐渐减小,焦耳热逐渐降低;弧长较大时,熔池表面的电磁力几乎不变;弧长较小时,随着径向距离的增大,电磁力先增大后减小.熔池表面的焦耳热随着弧长的增加而降低,但当弧长由45 mm增至50 mm时,焦耳热降低并不明显.弧压的增加会使得熔池表面的焦耳热增大.     

Effect of vibrating electrode on temperature profiles,fluid flow,and pool shape in ESR system based on a comprehensive coupled model

The vibrating electrode method was proposed in the electro-slag remelting(ESR) process in this paper,and the effect of vibrating electrode on the solidification structure of ingot was studied.A transient threedimensional(3D) coupled mathematical model was established to simulate the electromagnetic phenomenon,fluid flow as well as pool shape in the ESR process with the vibrating electrode.The finite element volume method is developed to solve the electromagnetic field using ANSYS mechanical APDL software.Moreover,the electromagnetic force and Joule heating are interpolated as the source term of the momentum and energy equations.The multi-physical fields have been investigated and compared between the traditional electrode and the vibrating electrode in the ESR process.The results show that the drop process of metal droplets with the traditional electrode is scattered randomly.However,the drop process of metal droplets with the vibrating electrode is periodic.The highest temperature of slag layer with the vibrating electrode is higher than that with the traditional electrode,which can increase the melting rate due to the enhanced heat transfer in the vicinity of the electrode tip.The results also show that when the amplitude and frequency of the vibrating electrode increase,the cycle of drop process of metal droplets decreases significantly.     

Effects of electrode immersion depth and remelting rate on electroslag remelting process

In the electroslag remelting process, the electrode molten state is a critical factor determining the ingot quality, while the electrode immersion depth and melting rate are key factors for the stability of the electroslag re-melting process. Studies were carried out to investigate the microscopic and macroscopic effects of electrode immersion depth and melting rate on the potential distribution and heat density in the slag bath, and on the depth and shape of the molten bath. Based on the finite element method and the numerical solution method, the effect of the electrode immersion depth on the slag bath heat density was researched; the relationship between the electrode immersion depth and the slag resistance was obtained; and the unsteady-state model of the solidification process of the re-melting ingot was solved using the finite difference method. The mathematical model and physical model of the electrode melting process were established and solved; and the corresponding curves between the electrode molten-state and slag-bath physical parameters were obtained. The experimental results verified the simulated results studied in this paper.     

三相电极电渣重熔系统中的磁流体流动和传热分析

建立了三相电极电渣重熔的全耦合三维非稳态模型,研究了电渣炉内的电磁现象、两相流动、传热以及凝固现象。其结果表明:大量的电流流经金属熔滴和熔渣,极少数的电流流经凝固锭。焦耳热功率密度的最大值出现在电极周围和金属熔滴中。高温区位于渣池上部的中心,渣池的平均温度随电流的增大而升高。金属熔池为扁平的U形轮廓,当电流升高时熔池加深并且加宽。     

Effects of electrode configuration on electroslag remelting process of M2 high-speed steel ingot

The electrode configuration determines the thermophysical field during the electroslag remelting(ESR) process and affects the final microstructure of the ingot. In this work, ingot with a diameter of 400 mm was prepared with two electrode configuration modes of single power ESR process, namely one electrode(OE) and two series-connected electrodes(TSCE). Finite element simulation was employed to calculate the electromagnetic field, flow field and temperature field of the ESR system. The results show that the temperature of the slag pool and the metal pool of the TSCE process is lower and more uniform than that of the OE process.The calculated temperature distribution of the ingot could be indirectly verified from the shape of the metal pool by the experiment. The experimental results show that the depth of the metal pool in the OE ingot is about 160 mm, while the depth of the TSCE ingot is nearly 40 mm shallower than that of the OE ingot. Microstructural comparisons indicate that coarse eutectic carbides are formed in the center of the OE ingot, whereas more even eutectic carbides appear in the center of the TSCE ingot. In general, compared with the OE process, the TSCE process is preferred to remelt high speed steel ingots.     

电渣重熔体系内磁场的数学模拟

基于Ｍａｘｗｅｌｌ方程组及有关的电磁场理论，提出了更切合实际情况的电渣重熔体系内磁场的数学模型，并应用于结晶器直径２００ｍｍ的实验室重熔装置．对直径７６ｍｍ低碳低合金钢电极的重熔过程（３０００Ａ（有效值），ＣａＦ２＋３０ｍａｓｓ％Ａｌ２Ｏ３＋２０ｍａｓｓ％ＣａＯ渣系），结果表明，磁场强度的幅模在电极内沿端部锥体形成方向不断增大，至接近锥顶处达最大值，约为２．６×１０４Ａ／ｍ，此后在渣池、锭子熔池、液固两相区和固态锭子内沿轴向向下逐渐减小；沿半径方向，在电极和渣池内呈现一峰值，在液、固金属区内则单调增大至边界条件限定值．对在直径１４０ｍｍ的结晶器中以直径８０ｍｍ的电极和ＣａＦ２＋ＣａＯ＋Ａｌ２Ｏ３＋ＭｇＯ渣系生产高速钢（Ｍ２）锭的过程，以该模型估计的重熔体系渣池和金属熔池内磁场强度（幅模）的大小和分布与实测结果较相吻合．该模型可作为研究电渣重熔体系内熔体流动，传热和传质过程的基础．     

电渣熔铸渣池深度对钢锭等效应力场影响的模拟

针对电渣熔铸钢锭各部位温差大,易产生热应力及测量困难的特点,采用大型有限元分析软件ANSYS,对电渣熔铸过程中不同渣池深度时的钢锭等效应力场进行了模拟研究,得出钢锭最大等效应力与渣池深度之间存在二次函数关系。模拟结果与实际相吻合,运用此模型可预报钢锭应力场状况,对实际生产提供参考。     

Effect of harmonic magnetic field and pulse magnetic field on microstructure of high purity Cu during electromagnetic direct chill casting

The effects of two types of magnetic fields, namely harmonic magnetic field (HMF) and pulse magnetic field (PMF) on magnetic flux density, Lorentz force, temperature field, and microstructure of high purity Cu were studied by numerical simulation and experiment during electromagnetic direct chill casting. The magnetic field is induced by a magnetic generation system including an electromagnetic control system and a cylindrical crystallizer of 300 mm in diameter equipped with excitation coils. A comprehensive mathematical model for high purity Cu electromagnetic casting was established in finite element method. The distributions of magnetic flux density and Lorentz force generated by the two magnetic fields were acquired by simulation and experimental measurement. The microstructure of billets produced by HMF and PMF casting was compared. Results show that the magnetic flux density and penetrability of PMF are significantly higher than those of HMF, due to its faster variation in transient current and higher peak value of magnetic flux density. In addition, PMF drives a stronger Lorentz force and deeper penetration depth than HMF does, because HMF creates higher eddy current and reverse electromagnetic field which weakens the original electromagnetic field. The microstructure of a billet by HMF is composed of columnar structure regions and central fine grain regions. By contrast, the billet by PMF has a uniform microstructure which is characterized by ultra-refined and uniform grains because PMF drives a strong dual convection, which increases the uniformity of the temperature field, enhances the impact of the liquid flow on the edge of the liquid pool and reduces the curvature radius of liquid pool. Eventually, PMF shows a good prospect for industrialization.