2.3t电渣锭重熔过程电极插入深度的数学模型和应用

利用Fluent软件中的MHD模块模拟得到电渣重熔稳态冶炼条件下不同电极插入深度的渣池电阻值,通过将渣池电阻值与电力制度相联系,建立了电极插入深度的数学模型。在特钢厂2.3 t电渣锭重熔稳态冶炼条件下,电极插入深度模型计算值为14.4 mm,现场测量值为14 mm,相对误差很小,在轴承钢G20CrNi2Mo现有的电力制度(58 V,9000 A)情况下,维持正常冶炼的最小渣量为24.3 kg/t,2.3 t电渣锭重熔的合理工艺为电压58 V,电流9 000 A,渣量30 kg/t,电极插入深度14.4 mm。     

工艺参数对电渣重熔空心钢锭凝固过程影响的数值模拟

凝固过程的控制对于保证和提高钢锭的质量十分重要,电渣重熔空心钢锭过程的凝固控制主要是对电渣重熔过程中金属熔池形状和深度进行控制,尤其以熔池深度作为凝固控制的主要参数.本文基于ANSYS和CFX软件对电渣重熔空心钢锭的凝固过程进行数值模拟研究,通过改变渣池深度、电极插入深度、电极布置方式来比较不同工艺参数对电渣重熔空心钢锭金属熔池形状的影响.模拟结果表明,在相同输入功率下,随着渣池深度的增加,金属熔池逐渐变浅;随电极插入深度的加深,金属熔池逐渐变深;十电极布置方式比八电极布置的金属熔池深,但渣/金界面的温度变化相对较小.     

电渣重熔过程渣/金界面行为的模拟

建立了电渣重熔体系下三维数学模型,以电渣重熔渣池、钢液为研究对象,利用Fluent商业软件,基于VOF多相流模型,对电渣重熔系统渣金两相流场进行模拟计算.计算结果表明:熔炼初期,金属电极采用薄膜熔化,从两端开始熔化并以小液滴的形式掉落,随着熔炼的进行,电极中部也开始产生小熔滴,最终在中心处形成一个大熔滴掉落,此后进入稳定熔炼期.对比不同电极端部形状,电极端部为圆头时比电极端部为平头时熔滴更容易在电极中心汇聚,渣金界面波动更大;对比不同电极插入深度,插入位置浅,熔滴通过渣层时间长,渣金界面波动更大;对比不同熔速,熔速为0.15 kg/s时,熔滴产生后,一滴一滴不连续掉落,这样熔滴可以与渣充分反应;加大熔速至0.20 kg/s时,可见熔滴成股流下,大熔速下,熔滴进入金属熔池时速度较大,渣金界面波动更大.     

多电极电渣重熔系统电磁场和焦耳热场研究

多电极电渣重熔系统比单电极系统具有感抗小、电耗低、熔化率高等特点,目前广泛应用于生产大型钢锭.掌握多电极电渣重熔系统中电磁场的分布情况对于提高钢锭质量和节省电能都很重要.本文以多电极电渣重熔工艺中电极、渣池和钢锭为研究对象,建立了能够考虑集肤效应的三维谐波电磁场数学模型,采用Maxwell方程、Lorentz定律和Joule定律分析了渣、钢锭和电极的磁场、电磁力、电流密度和焦耳热功率密度分布.结果表明:电流的最大值出现在电极内侧,与渣池的交界面处;由于电极的自感和互感的相互作用,两对电极内侧的磁感应强度增大,外侧的磁感应强度减小;焦耳热的最大值出现在渣中,电极底部内侧与渣的交界处.参数研究还发现:当源电流增大时,在电极内靠近壁面处的电流呈线性增大;当频率大于等于35 Hz时,在电极内部电流密度趋向线性分布;当电极侵入深度增大或渣层的厚度减小时,渣池中焦耳热的最大值增大.     

抽锭电渣重熔过程的流场和温度场的分布规律

建立抽锭电渣重熔过程多物理场三维数值模型,采用商业软件ANSYS对抽锭电渣重熔体系的流场和温度场进行了模拟计算。比较分析了不同电极浸入深度和不同渣池深度下抽锭电渣重熔过程的流场、温度场和金属熔池结构。通过实验测定抽出结晶器时的钢锭表面温度,验证了模拟结果的准确性。研究结果表明,抽锭电渣重熔过程的渣池内有2对漩涡生成,一对大的漩涡逆时针转动,另外一对小的漩涡顺时针转动;熔渣的速度随着电极浸入深度的增加而增大,随着渣池深度的增加而减小;渣池内有2个高温区,渣池内的温度高于金属熔池的温度;抽锭电渣重熔体系(电极、渣池和钢锭)的温度随着电极浸入深度的增加而上升,随着渣池深度的增加而下降。     

辊芯表层电渣加热渣池热电场及影响因素的数学模拟

在建立辊芯表层电渣加热物理模型和数学模型的基础上,利用大型有限元软件ANSYS对辊芯表层加热系统中渣池热电场及影响因素进行了模拟研究。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。     

电渣重熔过程中焦耳热与温度场的有限元分析

建立了电渣重熔过程中的电磁场与温度场的耦合数学模型,利用商业软件ANSYS对包括电极、渣池和钢锭的一体化电渣重熔系统电磁场、焦耳热场和温度场进行有限元计算,并分析冷却水温对重熔系统温度的影响.结果表明:重熔系统中的焦耳热主要分布在渣池中,其最大值出现在渣池与电极端口接触处,即电流密度最大处;重熔系统的最高温度出现在电极...     

基于电热场耦合条件下稀土电解槽电极结构优化模拟

以3kA钕电解槽为研究模型,考虑到电热场在电解过程中的相互影响,运用COMSOL有限元模拟软件建立了的电热耦合模型,并对不同配比的电极插入深度、极间距进行仿真模拟。结果表明,在一定槽电压下,电极插入深度与极间距之间存在配比关系,配比关系影响电流和温度分布。电热场耦合后,在4.2V槽电压下,电极插入深度为220 mm、极间距75 mm时的电流效率较高,电解过程更加稳定。     

T型结晶器电渣重熔复合轧辊渣池热电场的数值模拟

针对自耗电极环形焊接、T型结晶器抽锭电渣重熔制备复合轧辊的过程,利用ANSYS软件,建立了三维有限元模型,对渣池中的电位、电流密度和温度场的分布,以及电极位置变化的影响进行了数值模拟。计算过程采用热电耦合法,并考虑了电场的集肤效应。模拟结果表明,集肤效应的最强位置和最大电流都集中在自耗电极的表面;高温区在自耗电极和辊芯之间;电极位置的变化对渣池的电流密度分布影响比较大,当自耗电极与辊芯的距离增加10 mm时,渣池内最高温度降低20 K,上层渣池的平均温度有所提高。最后对数值模拟结果进行试验验证。     

固定自耗电极充填法电渣熔铸铸锭底部成形性研究

用固定自耗电极充填法电渣熔铸了横断断面为400 mm×60 mm的板形铸锭,用实验与数值模拟方法研究了铸锭底部成形性。结果表明:固定自耗电极充填法电渣熔铸板形铸锭时熔铸过程稳定、可控,表面质量良好;熔铸铸锭时,固定电极底部斜度有利于固定自耗电极平稳地进入电渣,其斜度的大小直接影响铸锭底部的成形性,斜度越大铸锭底部成形性越差。铸锭底部形状数值模拟结果与实验结果基本吻合。     

旋转电极电渣重熔过程熔滴滴落及熔池形状的模拟

建立了瞬态三维耦合数学模型以探索旋转电极对电渣重熔过程中电磁场、流场、温度场和熔池形状的影响.通过求解麦克斯韦方程组得到电磁场的相关信息,利用VOF方法描述金属熔滴的运动,采用焓-多孔介质模型计算凝固过程.当电极旋转,金属熔滴在离心力作用下,从电极边缘抛出,增加了金属熔滴在渣池中停留的时间与沿途路径,有利于提高电渣重熔...     

Modeling of Electromagnetic Field and Liquid Metal Pool Shape in an Electroslag Remelting Process with Two Series-Connected Electrodes

A three-dimensional finite-element model has been developed to understand the electromagnetic field and liquid metal pool shape in an electroslag remelting (ESR) process with two series-connected electrodes. The magnetic vector potential is introduced into the Maxwell’s equations, and the nodal-based method is used to solve a three-dimensional harmonic electromagnetic field. The heat transfer of the solidifying processes of ingot is modeled by a source-based enthalpy method, and the Joule heating is included in an inner source. The results show the main part of the current flows through the slag cap and a little enters into ingot in a two-series-connected electrode ESR system. As the interaction of self-induced and mutual-induced of two electrodes occurs, the skin effect is significantly suppressed by the neighbor effect. A symmetrical pattern of magnetic flux density in a two-series-connected electrode ESR system is displayed. The magnetic flux density between two electrodes is reinforced and reduced at the outside of two electrodes. The maximum Joule heat power density is located at the interface of slag and electrodes, and it decreases with an increase of the electrode immersion depth. The averaged Joule heat power density increases when slag cap thickness is reduced. With the increase of ingot height, the liquid metal pool shape changes from arc shaped to “V” shaped. When the ingot height is more than the diameter in the ESR processes, the liquid metal pool shape is constant.     

Numerical simulation of inclusion movement in electroslag remelting process

A comprehensive three- dimensional mathematical model, which adopted the Euler- Lagrange approach, was developed to study the motion of inclusions in electroslag remelting (ESR) process. The gravity, buoyancy, drag, added mass, lift and electromagnetic pressure forces were taken into account for the solution of inclusion trajectories. Due to the great difference between the conductivity of non- metallic inclusion and molten metal, the non- metallic inclusion would be drove to migrate to the mold wall by the electromagnetic pressure force. The movement behavior and removal rate of inclusions with different diameters were investigated in detail while the current ranged from 1200A to 1800A. The results show that more than 90% inclusions are captured by the top surface of the slag pool and the slag/mold wall. Only a small part of the inclusions are still suspended in the slag, and less than 4% inclusions would pass through slag/metal interface and enter into the metal pool. The removal rate of inclusions with larger diameter is higher than that of smaller diameter in the remelting process. With the increase of the current intensity, the removal rates of the inclusions with all diameters increase.     

Numerical Study on the Effect of Low-Frequency Power Supply on Desulfurization in the Electroslag Remelting Process

In the electroslag remelting (ESR) process, low-frequency power supply can significantly reduce power consumption and achieve three-phase balance of power supply. Therefore, a transient coupling model of fluid flow, heat transfer, and component transport in the ESR process, which is coupled to the electromagnetic field calculated using Maxwell 3D software, is established to study the influence of low-frequency power supply on desulfurization. When a 50 Hz power supply is used, a skin effect is observed in the metal, and the direction of the Lorentz force at the slag/metal interface changes. However, this effect becomes less pronounced with decreasing current frequency. Sulfur is mainly transferred at the electrode tip, and the desulfurization rate is approximately 50%. Electrochemical reactions mainly occur at the electrode tip/slag interface and the metal pool/slag interface. The removal rate of sulfur using direct current (DC) power supply is less than that using an alternating current power supply. The DC reverse polarity power supply leads to higher desulfurization rate than DC straight polarity, which is 74% and 31%, respectively. The sulfur removal rate increases from 81.37% to 84.59% as the frequency decreases from 50 to 2 Hz because of the longer electrochemical reaction time at this lower frequency.     

大型钢锭电渣重熔工艺数学模型的建立及模拟计算

 基于传热学基本理论,建立了80 t级三相电渣炉大型钢锭电渣重熔过程数学模型,并通过工业生产75t TP316LN奥氏体不锈钢钢锭验证模型,研究了大型电渣钢锭温度场分布情况及二次晶间距的变化情况。结果表明：渣池中心部位温度达1800℃,自上而下沿着传热方向中心线温度逐渐降低;金属熔池最深处达1500mm,大约等于钢锭直径的0.8倍;金属熔池上方具有50mm圆柱段以保证渣皮薄而均匀;二次枝晶间距大小由钢锭外侧边缘向中心部位呈递增趋势,模拟结果与实际生产情况吻合。     

Mathematical modelling of electroslag remelting P91 hollow ingots process with multi-electrodes

Abstract

Electroslag remelting (ESR) hollow ingot process with T-shape current supplying mould is a new metallurgical technology. A mathematical model was developed to describe the interaction of multiple physical fields of this process for studying the process technology. Maxwell, Navier-Stokes and heat transfer equations have been adopted in the model to analyse the electromagnetic field, magnetic driven fluid flow, buoyancy driven flow and heat transfer using finite element software ANSYS. Moreover, the model has been verified through the metal pool depth measurements, which were obtained during remelting of 10 electrodes into Φ900/500 mm hollow ingots of P91 steel, with a slag composition of 50–60 wt-% CaF₂, 10–20 wt-% CaO, 20–30 wt-% Al₂O₃, ≤8 wt-% SiO₂. There was a good agreement between the calculated results and the measured results. The calculated results show that the distribution of current density, magnetic induction intensity, electromagnetic force, Joule heating, fluid flow and temperature are symmetric but not uniform due to the multi-electrode arrangement in two symmetric groups. Simulation of the ESR hollow ingot process will help to understand the new technology process and optimise operating parameters.     

120t转炉高磷铁水冶炼高碳低磷钢生产实践

针对莱钢用高磷铁水冶炼高碳低磷钢容易出现终点碳过低和终点磷超标的问题,通过将脱磷渣碱度控制在1.5左右,实行双渣留渣工艺,提高前期底吹强度改善动力学条件,使用无氟化渣剂和增上滑板挡渣优化挡渣效果等措施,实现了高磷铁水冶炼低磷钢的高效生产。其中,终点磷质量分数可稳定控制在0.010%以下,脱磷率由89.80%提高到94.67%,终点碳质量分数控制在0.15%以上,钢水氧化性降低,钢包渣厚降低了40mm,精炼成白渣时间减少,满足了高碳低磷钢洁净度的要求,取得了良好的经济效益。     

电流对电渣重熔过程多场耦合行为和凝固参数影响的数值模拟

利用了FLUENT软件建立了电渣重熔(ESR)过程二维轴对称瞬态模型.使用有限体积法求解耦合的电磁场、动量和能量守恒方程,铸锭的凝固过程由焓-多孔介质模型处理,系统地研究了电流对电渣重熔GH984G凝固过程多场耦合行为和凝固参数的影响规律.模拟结果表明:电流由2.3kA增大为2.5kA,体系中电流密度、磁感应强度、洛伦...     

电渣重熔体系电毛细振荡的动态模拟

通过理论分析和交、直流电动态模拟试验证实了交流电渣重熔体系存在电毛细振荡;交流电频率越高,渣－金界面的振荡频率越大,振幅随之减小;在直流电渣重熔过程中,渣－金界面不存在电毛细振荡。     

Ti2AlNb合金锭真空自耗过程宏观偏析的数值模拟

Ti₂AlNb合金锭的真空电弧重熔(VAR)是一种超高温且不透明冶金过程,很难对这一过程中的熔体流动行为和宏观偏析的形成过程进行试验研究。发展了基于欧拉多相流的电磁场、温度场、流场、溶质场的多场强耦合数学模型,研究了真空自耗过程中的多物理场相互作用机制,对Ti₂AlNb合金锭中成分偏析形成过程及分布规律进行了预测。模拟结果表明,电磁力主要分布于熔池表面,自感电磁力推动金属液由中心向下流动而加深熔池;搅拌电磁力的离心效应则大幅提升熔池的温度场均匀度,促使熔池内金属液中的溶质混合均匀。尽管铸锭外围和中心分别形成了大范围的正、负偏析区,但区域内的成分较为均匀。在搅拌和沉降的作用下,金属熔池中的等轴晶极大地缩短了铸锭中的柱状晶区。该模型的模拟结果在熔池深度与宏观偏析分布方面与试验结果吻合良好,可进一步应用于预测和研究工业级大型铸锭中的成分偏析。