铝铸轧用铸嘴技术发展状况

阐述了铸嘴型腔布流的重要性，分析了布流不当引起的铸坯缺陷，总结了铸嘴技术发展状况及其特点。     

铝铸轧用铸嘴的优化设计

通过对铝合金连续铸轧机生产原理的了解和对典型铸嘴结构性能的分析及研究,对铸嘴的整体结构、内部型腔、布流系统及分流块进行了设计和选材.采用AutoCAD2008的绘图功能,进行几何造型设计,得到了一个较为实用、高效的铸轧机铸嘴.并对二级和三级分流块优缺点进行比较,分析了对铸嘴材料进行表面涂覆的可行性.     

镁合金双辊铸轧铸嘴内部熔体流动数值模拟

分析了铸嘴内部分流结构对型腔内镁合金熔体流场、温度场产生的影响.采用有限差分的SOLA-VOF法,建立镁合金双辊铸轧立板过程中流动区域的三维流场与温度场耦合模型,在相同的铸轧立板条件下(前箱液面高度、前箱熔体温度固定),数值模拟了不同形状的铸嘴型腔结构对熔体流动速度及温度分布的影响.模拟结果表明,分流块的大小、形状及位置对温度场及流动场影响显著,采用小尺寸、多数量的分流块将有利于在铸嘴型腔内形成均匀的流动场和温度场.通过工艺试验,验证了模拟结果,根据模拟结果改进了铸嘴内部结构,使金属熔体流场、温度场分布均匀,获得了高质量的镁合金铸轧板材.     

铸轧工艺参数对铝熔体流热场影响的模拟研究

利用Fluent流体模拟软件对1030铝合金铸轧流热场进行数值模拟分析,进而分析铸轧速度和浇注温度对熔体流热场影响的规律。结果发现,Hunter式铸嘴型腔中铝熔体的流场受铸轧速度影响较大,占据主导作用。铸轧生产时,若铸轧速度越慢,则铝熔体有充分的时间进行分配,铸嘴出口处中部与两侧边部之间铝液的速度差越小,但会导致铝液在铸嘴内滞留的时间长、温降大;浇注温度对铝熔体的流、热场影响十分有限,仅影响边部区域的速度场、铸嘴整体温度分布。当铸轧速度为1.2 m/min、浇注温度为695℃时有利于熔体在铸嘴型腔内的流动和充型,有利于铸嘴布流稳定以及保证板坯的质量。     

铝铸轧铸嘴分流块对型腔流场影响的研究

根据有效雷诺数Ｒｅｅｆｆ相似准则,做了铝铸轧铸嘴型腔熔体流动的水模拟实验,实验结果显示铸嘴型腔熔体流动行为受分流块相对位置、分流块结构尺寸、分流块数目影响很大,认为：使用小尺寸分流块,或适当增加分流块数目以及对于渐扩式侧壁的铸嘴型腔,转动分流块使其平行于侧壁,都能够获得更均匀的出口分布速度。     

铝铸轧铸嘴壁面复合传热分析

分析了铸嘴壁面复合传热方式,计算了不同导热系数和不同壁面厚度的壁面传热率,通过分析得出结论：铸嘴材料导热系数和铸嘴壁厚度尺寸对壁面传热率影响大,铸嘴型腔温度对壁面传热率影响小,对于同一材料和壁面厚度尺寸的铸嘴,常规铸轧和超薄快速铸轧的热损失基本相同。     

3003铝合金铸轧熔体流热场的数值模拟研究

采用FLUENT流体计算软件对3003铝合金铸轧流热场进行了数值模拟分析.结果 表明:铝熔体在铸嘴型腔内的流动属于湍流向层流的过渡流,应用FLUENT中的低雷诺数K-E湍流模型的计算结果精度高,收敛性好;熔体在铸嘴型腔内流动容易产生涡流,其原因是熔体通过分流块间隙时总是紧贴间隙一侧分流块的轮廓流动,导致另一侧区域充型不...     

双辊铸轧机铸嘴料的国产化

介绍了国产化铸嘴料的成分、制造工艺和主要性能。使用结果表明，国产化铸嘴料可完全替代法国进口的铸嘴料用于铝板坯的铸轧生产。     

海外文献速报

<正>20140201章旭文,林惠娟,许富渊,等.水平连铸过程中坩埚设计对铸嘴出口流场分布的影响.铸造工程学刊,2013,39(1):1-8.在水平连铸中,薄带厚度均匀性依赖于铸嘴出口流场及铜轮转速与品质的稳定。其中,铸嘴出口流场的稳定性与坩埚液位高度或压力有关。模拟结果显示,当坩埚液位高度低于14cm时,铸嘴出口速度呈现不均匀的情况,会导致薄带有不均匀甚至破洞的可能。根据毛细数(Capillary Number,CA)分析结果,当CA值小于0.015且铸嘴长宽比(L4/B)大于30的情况下,坩埚内流体则无法顺利经铸嘴流出。     

双带式非晶带材连铸熔池热流耦合数值模拟

以制备新型双带式非晶锆合金带材连铸机的熔池为研究对象,基于VOF算法,考虑了外界气体层与熔池自由液面的相互作用,建立了熔池内流动和传热的三维耦合模型,对比分析了采用传统楔形布流系统和新型布流系统时熔池流场和温度场的分布情况。结果表明,采用新型布流系统进行浇注时,熔池侧封区域的自由液面更为平稳且熔池出口处的轴向最大温差从30℃减小到15℃左右,验证了新型布流系统的合理性。     

Numerical simulation on electromagnetic field,flow field and temperature field in semisolid slurry preparation by A-EMS

A two-dimensional computational model coupling an annular electromagnetic stirring (A-EMS) with a macroscopic heat and fluid flow analysis in Al-alloys semisolid slurry preparation was developed. The dynamic evolutions of the electromagnetic field, flow field, and temperature field were presented successfully by commercial software ANSYS 10.0 with corresponding experimental verification. A horizontally rotational electromagnetic field and, thereby, a more intensive velocity field were uniformly distributed in the stirred melt even at commercial frequency, and thus, a lower temperature difference in the stirred melt and subsequent uniformly fine microstructures were obtained compared with the normal electromagnetic stirring. The simulation results were in good agreement with experimental ones.     

Development and application of coupling model of aluminum thin-gauge high-speed casting

Based on the analyses of aluminum melt flow, solidification, heat transfer during the process of twin-roll casting, a coupling mathematical model of aluminum thin-gauge high-speed casting was developed, which included the casting roller shell. At the same time, Galerkin method was adopted to solve the coupling model. The fluid field and temperature field of aluminum melt in casting zone, the temperature field and thermal stress field of roller shells were simulated by the coupling model. When the casting velocity is 7 m/min, and the thickness of strip is 2 mm, the circumfluent area comes into being in the casting zone, and the mushy zone dominates the casting zone, while the temperature of melt decreases rapidly as it approaches the rollers. The temperature of the roller shell varies periodically with the rotation of roller, and reaches the highest temperature in the casting zone, while the temperature of roller shell decreases gradually as it leaves the casting zone. The difference of thermal stress between the inner surface and outer surface of the roller shell is very large, and the outer surface suffers tensile-compressive stress.     

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。     

Numerical simulation of electromagnetic and flow fields of TiAI melt under electric field

This article aims at building an electromagnetic and fluid model, based on the Maxwell equations and Navier-Stokes equations, in TiAI melt under two electric fields. FEM (Finite Element Method) and APDL (ANSYS Parametric Design Language) were employed to perform the simulation, model setup, loading and problem solving. The melt in molds of same cross section area with different flakiness ratio (i.e. width/depth) under the load of sinusoidal current or pulse current was analyzed to obtain the distribution of electromagnetic field and flow field. The results show that the induced magnetic field occupies sufficiently the domain of the melt in the mold with a flakiness ratio of 5:1. The melt is driven bipolarly from the center in each electric field. It is also found that the pulse electric field actuates the TiAI melt to flow stronger than what the sinusoidal electric field does.     

Numerical simulation of electro-magnetic and flow fields of TiAl melt under electric field

This article aims at building an electromagnetic and fluid model, based on the Maxwell equations and Navier-Stokes equations, in TiAl melt under two electric fields.FEM (Finite Element Method) and APDL (ANSYS Parametric Design Language) were employed to perform the simulation, model setup, loading and problem solving.The melt in molds of same cross section area with different flakiness ratio (i.e.width/depth) under the load of sinusoidal current or pulse current was analyzed to obtain the distribution of electromagnetic field and flow field.The results show that the induced magnetic field occupies sufficiently the domain of the melt in the mold with a flakiness ratio of 5:1.The melt is driven bipolarly from the center in each electric field.It is also found that the pulse electric field actuates the TiAl melt to flow stronger than what the sinusoidal electric field does.     

Turbulence flow and heat transfer of aluminum melt in tip cavity in process of thin-gauge high-speed casting

The uniformity of flow distribution of aluminum melt in tip cavity is a precondition to decide whether or not thin-gauge high-speed casting can be accomplished smoothly. The laws of aluminum melt flow and heat transfer in tip cavity can be found out through numerical simulation, which gives theoretical basis for solving the problem of the flow distribution of melt in tip cavity. A mathematical model with a low Reynolds number k--ε model for turbulence flow and heat transfer of aluminum melt in tip cavity was developed. The finite difference method was used to calculate the flow field and temperature field of aluminum melt in tip cavity. The phenomena and characteristics of turbulence flow and heat transfer were analyzed, including the characteristics of temperature distribution of turbulence similar to that of laminar flow. The simulation results are in good agreement with the experimental results for flow velocities and temperature at the exit of tip, which verifies the validity of the simulation results.     

离心铸造钛合金熔体充型流动物理模拟相似理论及实验研究

借助相似物理模拟理论,研究离心铸造钛合金熔体充型流动物理模拟相似准则。并采用相似物理模拟的方法,研究离心力场下钛合金熔体充型流动过程中,熔体流动的变化规律。实验结果表明:离心力场下物理模拟钛合金熔体充型流动时,同时满足Cn准则和雷诺准则;模拟流体充型流动时,沿着横浇道后壁进行充型;流体的自由液面是以转轴为圆心的规则圆弧面;流体横截面面积随着旋转速度和充型长度的增加相应减小;转速越高,在同一时间内,充填速度和长度越小。     

浇注速度对铸件充型过程流场影响的数值模拟

基于ANSYS软件的CFD模块,利用不可压缩流体的流动控制方程和标准的K-ε模型,以1623K的HT150金属液为对象,对不耦合温度场时铸件充型过程的二维流场进行数值模拟,考察了浇注速度的影响。结果表明,浇注速度对流场的影响显著。当浇注速度较低(0.7m/s)时,金属液充型平稳,基本上不存在卷气现象,自由表面几乎一直保持水平状态直到充型结束,但在充型开始到整个直浇道被金属液填满的过程中发生多次流体分离现象。随浇注速度的提高,流体分离现象显著降低甚至消失,金属液与型壁碰撞加强,卷气的倾向增强。当浇注速度为1.3m/s,金属液与型壁撞击强烈,卷气明显,充型过程极不平稳,自由表面波动剧烈。综合比较的结果表明较为合适的浇注速度为1.0m/s。     

EBCHR熔铸TA10钛合金非对称流动及凝固过程数值模拟

熔池中的流动是影响电子束冷床炉熔铸铸锭质量的一个非常重要因素。本工作通过建立三维非稳态模型研究电子束冷床炉熔铸钛扁锭过程中的流动及熔池形态变化，采用混合欧拉-拉格朗日算法模拟非稳态凝固过程。通过设置一系列的能量输入策略，分析了不同电子枪功率下的结晶器内的非对称流动特征、温度场及熔池形态变化。研究结果表明流动及传热共同导致了非对称熔池的形成。钛液从溢流口进入结晶器后，一部分向下流动侵蚀凝固坯壳，一部分由于不同温度下的密度差受到的浮力返回了液面。凝固坯壳被侵蚀后变薄影响对称性，返回液面的钛液改变了液面温度影响了能量吸收效率及液面温度分布。通过优化电子枪的能量输入策略，可以有效的改善熔池的对称性，避免因熔池不对称导致的熔铸缺陷的出现。     

CFD技术在铝电解中的应用

计算流体力学(CFD)是研究流动、传热及化学反应过程的常用方法,目前在轻金属冶金领域逐渐得到科研工作者的重视并显示出广阔的应用前景.本文由电解槽内熔体流场和温度场两个方面的数值模拟,阐述了其在电解铝行业的应用现状.