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。     

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。     

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。     

Simulation of electro-slag re-melting process of 120 t large ingot for nuclear power station and its application

Further research on metallic materials for the super critical rotator and the main pipe line of a nuclear power station is very important for developing the nuclear power industry.In this study,the mathematical model for 120 t large ingot was established,and the computer program ESR3D was developed to simulate the whole electroslag re-melting (ESR) process.This includes the electrode melting,metallic droplet falling,metal pool forming,metal pool and slag pool rising and moving,installation of top crystallizer,ingot solidifying,etc.The simulated average melting rate of the electrode was in good agreement with that in practical production.The optimized parameters were used to produce 80-120 t large ingots,and the quality of the ingots satisfied the specifications of nuclear power and the super critical generating unit.     

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.     

A CELLULAR AUTOMATON-APPROACH TO SIMULATION OF GRAIN STRUCTURE DEVELOPMENT IN ELECTROSLAG CASTING

1.IntroductionElectroslagcastingcanproducepartsofgoodquality,ofwhichthemechanicalpropertiesarecomparablewithorsuperiortothoseofforgedproducts.Ithasbeenmoreandmoreutilizedtomakestructuresofcriticalimportance,whichconventionallywoulddoubtlesslybemadebyforging.Understandingandcontrolofmicrostructures,especiallyshape,sizeandorientationofcrystallitesinelectroslagcastingarethereforemoreandmoreimportantforsafetyconcernintheirapplication.Experimentalstudiesofthegrainstructuresandtheirdependenceonvario…     

熔池深度随电渣重熔过程变化规律的数模研究

通过数据的数学处理,找出了熔池深度与锭高和重熔电流间的规律.这一数学模式可用于描述和预示任意重熔电流时的最大熔池深度及随锭高增长熔池深度变化的趋向.熔池的深浅,影响金属结晶生长方向改变及夹杂物和气体的去除过程.合理控制重熔电流与熔池深度,对改善ESR锭铸态组织和材料品质是有益处的.     

NUMERICAL SIMULATION OF TEMPERATURE FIELDS IN ELECTROSLAG REMELTING SLAB INGOTS

The method based on transient heat transfer model is adopted to simulate electro-slag remelting process. The calculated results of the model show that the process is in the quasi-steady state, and the shape of pool remains unchanged when the height of ingot is approximately 2.5-3 times the thickness of slab ingot. The change in the shape of pool is found to be strongly dependent on the pattern of melting rate, and hence, the power input; the depth of the molten pool increases with the increase in melting speed. It is concluded that a transient heat transfer model has to be used to obtain reliable input information for the entire, operatina time.     

数值模拟电极缩孔对IN718合金电渣重熔过程的影响

利用自主开发的ESR过程仿真软件,针对直径430 mm的IN718合金铸锭,通过设计不同形状尺寸的电极缩孔,进行电渣重熔过程的数值模拟计算和分析。结果表明,基于电磁场、流场和温度场等多物理场耦合计算自主开发的ESR数学模型及仿真软件,可以用于ESR冶炼全过程数值模拟,模型计算的熔池形状和深度、二次枝晶臂间距分布规律与实际剖锭分析结果接近。电极中存在缩孔改变了电极与渣池的接触面积,从而显著影响渣池的焦耳热和电磁力分布,而缩孔沿电极轴向尺寸的变化对二者分布的影响则很少。在恒熔速条件下,当缩孔半径小于0.025 m时,缩孔对熔炼过程几乎没有影响;当缩孔尺寸继续增大时,渣池温度场和流场发生明显改变,渣池温度逐步升高,中心向下流速相对减弱;电极缩孔尺寸变化对熔池温度场及两相区尺寸影响不明显。缩孔半径尺寸对电流和功率等熔炼参数的影响呈非线性关系,临界变化值约为0.05 m,当缩孔半径低于临界值时,对电流和功率等影响较小;高于临界值时,随着缩孔半径增加,电流和功率显著增加,并且增速不断加快。从工艺过程控制稳定性角度而言,该尺寸电极缩孔半径应控制在0.05 m以下。     

用模铸八角锭作为自耗电极生产H13钢电渣重熔锭

通过调整电渣重熔时的冶炼工艺参数,直接以截面差异较大的5.0 t模铸八角锭作为电渣重熔用自耗电极,生产出了质量优良的H13钢电渣重熔锭。该工艺可降低生产成本、缩短生产周期。     

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．     

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.     

Ti60合金VAR熔炼过程熔体流动与宏观偏析的数值模拟研究

真空自耗电弧熔炼 (Vacuum arc Remelting,VAR) 是生产钛合金铸锭最常用的方式之一,但由于其熔炼过程温度高且不透明,通过实验研究其熔炼过程中流体流动行为和宏观偏析存在困难。基于此,本工作以Ti60高温钛合金为例,通过数值模拟方法对VAR熔炼过程展开研究,同时探讨了熔炼电流和磁场搅拌强度对流体流动行为和宏观偏析的影响。结果表明,VAR熔炼钛合金时,熔池形状由“扁平状”逐渐向“V形”转变;凝固结束后铸锭锭底和边部Zr元素含量低,中心和冒口含量高。熔炼电流产生的洛伦兹力使熔体沿逆时针流动,且熔炼电流越大,熔体流动更剧烈;同时也导致铸锭中心和冒口处出现更为严重的宏观偏析。搅拌磁场产生的洛伦兹力作用于整个熔池,不仅促进了熔池上部熔体的流动,也有利于熔池下部熔体的流动;当无搅拌磁场和搅拌磁场较大时,都会导致Zr元素在铸锭中产生较为严重的宏观偏析。为有效控制VAR熔炼钛合金时宏观偏析缺陷的产生,应采取小熔炼电流和合适的搅拌强度。     

Reducing defects in remelting processes for high-performance alloys

Defect reduction is one of the most important goals in continuing research to improve remelting technologies, such as vacuum arc remelting, electroslag remelting, or hearth melting (plasma or electron beam), of specialty alloys. Ingot defects may originate from several sources in these processes, such as foreign materials in the melt stock or electrode, drop-in material from the furnace interior, and solidification defects. Laboratory-and industrial-scale melting experiments are used by Sandia National Laboratories and the Specialty Metals Processing Consortium to determine relationships between melt-processing conditions and defect formation. Examples described here include freckle formation, a solidification defect in large ingots of alloy 625 (electroslag remelting), and alloy 718 (vacuum arc remelting). These examples demonstrate how integrated melting experiments, process modeling, and ingot analysis can guide the control of melting conditions to reduce defects. Editor’s Note: A hypertext-enhanced version of this article, including video of the arc gap during the vacuum remelting of alloy 718, can be found on the TMS web site at www.tms.org/pubs/journals/JOM/9803/VanDenAvyle-9803.html. James A. Van Den Avyle earned his Ph.D. in metallurgical engineering at the Massachusetts Institute of Technology in 1975. He is currently a principal member of the technical staff at Sandia National Laboratories. John A. Brooks earned his Ph.D. in metallurgy at Carnegie Mellon University in 1981. He is currently a principal member of the technical staff at Sandia National Laboratories. Dr. Brooks is also a member of TMS. Adam C. Powell earned his Ph.D. in materials science and engineering from the Massachusetts Institute of Technology in 1997. He is currently a post-doctoral researcher in metallurgy at the National Institute of Standards and Technology. Dr. Powell is also a member of TMS.     

40CrNiMoA钢曲轴毛坯的试制

采用电弧炉冶炼+LF精炼+VD真空除气+电渣重熔工艺生产7吨级40CrNiMoA钢锭,并锻造了曲轴毛坯。提出了电极坯及电渣锭制备工艺制度,确定了锻造及锻后热处理工艺。各项技术指标均达到了质量要求。     

电渣熔铸异型件熔渣内溢现象

分析了异型电渣熔铸件生产过程中的熔渣内溢现象及形成因素.研究表明,更换电极中断功率操作后,供电工艺参数与结晶器冷却强度不匹配是导致结晶器内熔渣溢流的主要原因.从更换电极操作与熔铸工艺进行改进优化,改进后实际生产效果良好.     

电渣熔铸中电流对自耗电极端部锥角影响的研究

电渣熔铸就是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过程,自耗电极与渣池的接触界面是整个熔铸系统能量的入口,其形貌对熔铸过程的分析和研究非常重要.研究了在不同熔铸电流情况下自耗电极的熔化机理,模拟再现了自耗电极在高温渣池内的熔化流动且在末端形成锥形的过程,并进行了试验验证.通过对熔铸电流与自耗电极末端锥角的关系研究,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.     

电渣熔铸渣皮分层现象研究

研究电渣熔铸过程中渣皮的形成机理.通过电渣重熔钢锭渣皮逐层物化检测,提出在钢锭凝固过程中,在其上周缘存在"环形小熔池","小熔池"的形状和稳定性影响钢锭渣皮厚度和表面品质.采用过冷度大、熔点低的渣比过冷度小、熔点高的渣更易保证表面品质.     

3D numerical investigation of effects of density and surface tension on mixing time in bottom-blown gas-stirred ladles

In molten phase metallurgical processes, mixing via gas injection has a vital role in obtaining a homogeneous product. The efficiency of mixing depends on operational variables such as gas flow rate and slag height as well as physical properties of the molten phases. A numerical simulation is conducted to study the above parameters in the flow behavior of a bottom-blown bath. The molten metal and the slag are modeled by water and oil, respectively. The numerical results, particularly the mixing time, are validated against experimental data. The results show that mixing time increases as the slag height increases and decreases as the density of the slag material increases. The mixing time decreases with an increase in the density of the primary phase; however, it increases as the surface tension between air and water increases. A case with properties close to a real molten metal is also modeled. The performance of the system is influenced by the momentum rather than the dissipative forces. Thus, the effect of the density of the molten phase on the mixing process is more pronounced compared to the effect of the surface tension between the air and the molten phase.     

模铸中间包液面波动的物理模拟研究

以60 t模铸中间包为研究对象,研究了中间包熔池深度、浇注速度对中间包液面波动的影响,以及各种工况条件下的卷渣情况。同时,对比研究了敞流浇注和长水口保护浇注对中间包液面波动的影响。研究结果表明,模铸中间包采用敞流浇注方式时,由于浇注过程中注流卷吸空气,以及注流对中间包液面的冲击所引起的液面波动,将导致钢液二次氧化严重,降低钢锭质量。当中间包定径水口直径为45 mm、中间包熔池深度为1 600 mm~1 800 mm时,中间包液面波动最小,熔池深度小于1 000 mm时发生卷渣。当定径水口直径为50 mm、中间包熔池深度为1 600 mm~1 800 mm时,中间包液面波动最小,熔池深度小于1 200 mm时发生卷渣。当定径水口直径为55 mm、中间包熔池深度为1 800 mm时,中间包液面波动最小,在试验所考察的各熔池深度卷渣都较为严重。采用长水口保护浇注,液面波动很小,有利于减少钢液二次氧化,降低钢液卷渣几率,提高钢锭质量。