电渣重熔过程中夹杂物的控制

电渣重熔过程中非金属夹杂物的去除主要发生在自耗电极端头熔滴形成期以及熔滴滴落穿过熔渣层阶段。电渣重熔过程中原生夹杂物去除的同时将产生新的夹杂物,为了有效地控制电渣锭中的夹杂物,使用复合脱氧剂对自耗电极进行终脱氧,采用合理的重熔速度、熔渣的化学组成和供电制度,以及严格控制电渣炉内氧位。     

电渣重熔去除夹杂的机理

在现代电冶金中,电渣重熔是有效地去除钢中非金属夹杂物主要手段之一。但电渣重熔去除夹杂物机理的研究还存在着分岐。电渣重熔有三个阶段:1.电极端头熔滴形成期;2.熔滴滴落穿过渣池阶段;3.铸锭顶端液态金属熔池凝固阶段。为了查明哪一阶段是精炼主要阶段。我们制取了自耗电极原始金属;电极端头金属熔化薄膜;渣池中的金属熔滴及凝固铸锭金属试样。用金相法,化学分析法及放射性同位素(Zr~(95)O_2)方法测定各阶段提纯效果及夹杂物去向。研究得出结论:电渣重熔去除钢中非金属夹杂物主要发生在电极熔化端头。上述结论在工业试验中得到进一步验证。     

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.     

轴承钢电渣重熔过程中氧的控制及作用研究

研究了不同氧含量（（５～４０）×１０－６）的自耗电极及重熔渣系对轴承钢氧含量、夹杂物和疲劳性能的影响，结果表明：①无论用高氧含量（＞３０×１０－６）自耗电极还是低氧含量（＜１０×１０－６）自耗电极重熔，电渣钢中氧含量都保持在（１５～３０）×１０－６；②影响电渣钢中氧含量的决定因素是渣中的ａＦｅＯ值，自耗电极中的原始氧含量影响较小；③电渣重熔过程中，自耗电极中原始夹杂可基本去除，重熔钢中的夹杂主要是金属熔池冷却结晶过程中新生成的。     

电渣重熔钢液洁净度控制研究进展

电渣重熔工艺能够显著去除钢中的非金属夹杂物、降低钢中的总氧含量。本文阐述了电渣重熔过程中非金属夹杂物的去除机理、夹杂物成分和含量的控制以及电渣重熔过程中氧含量的控制,介绍了电渣重熔过程钢液洁净度控制的研究进展,提出了进一步提高电渣重熔过程钢液洁净度水平的研究方向。     

电渣重熔钢中非金属夹杂物含量及成分的控制

在电渣重熔过程中，控制自耗电极冶炼的脱氧制度并配合电渣重熔渣系的选择，可以有目的地控制电渣重熔钢中非金属夹杂物的含量和成分。对于滚珠轴承钢ＺＧＣｒ１５，当自耗电极用钢采用Ｓｉ－Ｆｅ、Ｓｉ－Ｃａ脱氧并用酸性渣重熔可以获得最佳精炼效果，使钢中夹杂物转变为硅酸盐类塑性夹杂物。上述结论在工业生产中已得到验证。     

电渣重熔高氮钢的洁净度研究

对高氮钢电渣重熔前后夹杂物进行对比研究,分析不同渣系和自耗电极氧含量对重熔后夹杂物的影响。研究发现,不同渣系对电渣钢的洁净度影响很大,适当提高w(CaO)/w(Al2O3)可有效降低电渣锭中的夹杂物和全氧量。不同氧含量的自耗电极进行重熔后,电渣锭全氧量及夹杂物种类和组成成分差别不大,夹杂物成分中w(MnO)/w(MnO+Al2O3)≈0.23~0.32,自耗电极中的氧含量与电渣重熔的洁净度没有直接关系,采用氧质量分数为(40~100)×10-6的不同自耗电极,电渣重熔后氧质量分数始终保持在(20~30)×10-6。     

电渣重熔过程夹杂物运动行为的数值模拟

采用欧拉-拉格朗日法,建立三维瞬态数学模型研究电渣重熔过程中非金属夹杂物的运动行为,并考虑重力、浮力、阻力、升力、附加质量力以及独特的电磁压力对夹杂物运动轨迹方程的影响。电磁压力是由于非金属夹杂物与钢液之间巨大的电导率差而产生的,该力可使非金属夹杂物向壁面定向运动,从而促进夹杂物去除。考察了5种粒径的夹杂物在电流强度为1 200、1 500和1 800A时的运动行为和去除率,并进行了实验验证。结果表明,超过90%的夹杂物在渣池与空气接触面和渣池与结晶器侧壁接触面上被捕获,剩余夹杂物仍随熔渣运动,不到4%的夹杂物会穿过渣金界面进入钢锭中。直径大的夹杂物去除率大于直径小的夹杂物。随着电流强度的增加,不同粒径夹杂物的去除率均有所增加。     

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工艺的精炼效率。模拟结果表明,随着电极旋转,熔滴数量增多,尺寸变小,渣池内的温度分布变得均匀,当电极的转速由0 r/min提高至20和50 r/min,熔池深度由81 mm降至78和61 mm,熔池形状逐渐变得浅平,有利于提高电渣重熔铸锭的质量。     

17-7PH沉淀硬化不锈钢电渣重熔过程洁净度的变化

采用35 t电弧炉-AOD脱碳-LF精炼-模铸工艺制备了17-7PH沉淀硬化不锈钢自耗电极,并通过气体保护电渣炉重熔得到了2 t重的电渣锭。利用ASPEX扫描电镜分析了电渣重熔前后17-7PH钢中夹杂物数量、尺寸、成分的变化规律,并采用SEM-EDS进一步观察夹杂物的形貌及组成。研究结果发现,电渣重熔后,O含量由6.6×10^-6降至5.7×10^-6,N含量由200×10^-6降至180×10^-6。重熔前后夹杂物的类型没有变化,重熔后总的夹杂物数量大幅减少,特别是大颗粒夹杂物的数量明显减少、尺寸减小。电渣锭中总的夹杂物以AlN夹杂物为主,其尺寸较大、数量最多。为了提高17-7PH钢电渣锭的洁净度,应尽可能减少自耗电极中的N含量,以减少电渣重熔过程AlN夹杂物的生成量。     

Effect of initial large-sized inclusion content on inclusion removal during electroslag remelting of H13 die steel

The current paper focuses on the influence of initial large-sized inclusion content in the consumable electrode on inclusion removal during electroslag remelting (ESR) of H13 die steel. Considering the relationship between the inclusion size and the interfacial energy change of the slag/inclusion/steel system during the inclusion transfer across the steel/slag interface, the thermodynamic conditions for inclusion removal from steel to the slag were put forward. The results showed that the content of large-sized inclusions in final ESR ingot was decreased by approximately 13.66% with the increase in large-sized inclusion content in the consumable electrode from 11.36?mg/10?kg to 16.50?mg/10?kg. The interfacial energy change of the slag/inclusion/steel system decreases with the increase in inclusion radius during the absorption process of inclusions by slag, which is beneficial for inclusion removal.     

炼钢造渣物料高温热焓值的试验测定

为确切了解转炉炼钢过程中各种物料的加入给炼钢熔池温度带来的影响,对影响熔池温度的造渣材料的热焓值进行了测定。结果表明,各种物料在炼钢温度下的吸热程度不同,石灰、轻烧白云石、镁球的吸热温度区间为350~500℃,每吨物料的温降分别为4.8、6.6和5.6℃;石灰石的吸热温度为726℃,每吨物料的温降为7.9℃;烧结矿、废钢、炉渣的吸热温度为1300~1400℃,每吨物料的温降为5.6、1.4和1.1℃。根据测定结果,结合铁水成分和现场实际数据,预测转炉终点钢水温度的模型,为提高转炉终点钢水温度精确控制和优化工艺参数提供依据。     

电源频率对电渣重熔锭质量的影响

 研究了不同频率对电渣锭质量的影响。研究结果发现：电源频率的降低导致了渣池电磁搅拌的强烈,促进了渣池的温度均匀,因而降低了金属熔池深度;随着电源频率的降低,铸锭中的氧含量明显增高,这主要是由于在渣池中的部分氧化物发生了电解反应,导致了氧进入钢中,增加了钢中的夹杂物含量。     

电渣重熔体系渣池运动分析及数学模型发展

对电渣重熔过程中渣池运动的驱动力进行了分析，并对电渣重熔体系的数学模型进行了回顾和评价。结果表明，引起渣池运动的因素主要包括渣池中的电磁力和渣池温度不均匀分布而产生的对流运动；电极端部形状对渣池电磁场分布有一定影响，进而影响渣池的运动。最后提出了改进和渣池运动数学模型     

Distribution law of flow field and temperature field in electroslag remelting withdrawal process

A three- dimensional mathematical model was developed to describe the interaction of multiple physical fields during the electroslag remelting withdrawal (ESRW) process. Flow fields and temperature fields of the ESRW system were simulated by commercial software ANSYS. The flow fields, temperature fields and the shapes of the molten pool during the ESRW process with different electrode immersed depths and slag heights were analyzed and compared. The temperature of ingot surface was measured, and the accuracy of simulation results was verified. The results show that there are two pairs of vortexes in slag bath during the ESRW process. A pair of large vortexes turns counterclockwise, and another pair of small vortexes rotates clockwise. The speed of slag increases with the increasing of immersion depths of the electrode, and decreases with the increasing of slag heights. There are two high temperature zones in the slag bath, and the temperature in the slag bath is higher than that in the metal bath. The temperature of ESRW system (electrode, slag bath and ingot) becomes higher with the increasing of immersion depths of the electrode, whereas becomes lower with increasing of slag heights.     

Steel Quality Improvement Potentials in the Continuous Casting Process Using State of the Art Refractory Flow Control Systems

In the continuous casting process for high quality steel grades, activities are mainly focused on avoiding reoxidation and promoting non-metallic inclusion removal during steel transfer from the ladle through the tundish to the mould. In this paper, methods to effectively control flow from the tundish to the continuous casting mould are described and specific state of the art refractory solutions are also introduced.     

Modification of Inclusions in Molten Steel by Mg-Ca Transfer from Top Slag: Experimental Confirmation of the ‘Refractory-Slag-Metal-Inclusion (ReSMI)’ Multiphase Reaction Model

High-temperature experiments and Refractory-Slag-Metal-Inclusion (ReSMI) multiphase reaction simulations were carried out to determine the effect of the ladle slag composition on the formation behavior of non-metallic inclusions in molten steel. Immediately after the slag-metal reaction, magnesium migrated to the molten steel and a MgAl₂O₄ spinel inclusion was formed due to a reaction between magnesium and alumina inclusions. However, the spinel inclusion changed entirely into a liquid oxide inclusion via the transfer of calcium from slag to metal in the final stage of the reaction. Calcium transfer from slag to metal was more enhanced for lower SiO₂ content in the slag. Consequently, the spinel inclusion was modified to form a liquid CaO-Al₂O₃-MgO-SiO₂ inclusion, which is harmless under steelmaking conditions. The modification reaction was more efficient as the SiO₂ content in the slag decreases.     

CAS OB精炼和连铸过程钢中夹杂物来源示踪研究

通过添加示踪剂研究CAS OB的精炼过程和连铸过程以及板坯钢样夹杂物来源。结果表明,精炼过程和钙处理后的钢中显微夹杂物均含有钢包渣示踪元素镧;中间包钢样中的显微夹杂物同时含有镧和中间包示踪元素铈;板坯中的显微夹杂物含有镧、铈、钾、钠中的几种,说明钢液脱氧产物与钢包渣、中间包覆盖剂、结晶器保护渣均产生了反应。板坯中大型夹杂物主要源于结晶器保护渣,其次源于钢包渣,少部分源于中间包覆盖剂;大型夹杂物同时含有钾、钠、镧、铈中的几种元素,说明大型夹杂物是脱氧产物与卷入钢液中的钢包渣、中间包覆盖剂、保护渣或中间包内衬蚀损产物相互反应的复杂夹杂物。     

Research Status of Numerical Simulation of Nonmetallic Inclusions Interfacial Removal

The removal of inclusions in liquid steel has always been the focus of research, and the removal of inclusions is mainly through the process of the inclusion through the slag–steel interface. The inclusion removal process can be subdivided into inclusions in molten steel grew up rise, in steel–slag interface through separation, adsorb dissolved in molten slag 3 steps. Based on the microscopic process of three steps, this article summarizes and discusses the mathematical model, fluid mechanics model, and experimental verification method of inclusion removal process, analyzes limiting and influencing factors of inclusion removal process, and comprehensively describes the numerical simulation research progress of inclusion removal process. With the development of numerical simulation techniques and experimental equipment, some progress has been made in the study of interfacial removal of inclusions. The inclusion interface removal behavior can be analyzed semiquantitatively based on dynamic force model. The computational fluid dynamics model has advantages in studying the phenomena of the inclusion interface, and the phase-field method is often used to simulate the removal process of the inclusion interface. The combination of water model and numerical simulation, high-temperature laser confocal method, and other methods is of great help to explore the interface behavior of inclusions.