铝铸轧铸咀型腔熔体流动水模拟

根据Ｆｒｏｕｄｅ数相似准则,做了铝铸轧铸咀型腔体流动的水模拟实验,其结论：现有 咀出口处熔体流动速度相对误差达１９％以上,不能满足超薄快速铸轧工艺的需要。     

超薄快速铸轧过程轧制压力分布的数学模型与实验研究(Ⅲ)——铸造区与轧制区轧制压力仿真研究

在建立了铸造区，轧制区轧制压力模型的基础上，对常规铸轧条件进行了仿真计算，计算结果与实测数据相吻合，从而验证了模型的正确性，在此基础上，对超薄快速铸轧条件进行了虚拟仿真研究，研究结果表明：不增强铸轧辊内，外冷却能力的条件下，而仅仅减薄铸轧 板坯厚度即可提高铸轧速度，在其它工艺参数保持不变，且保持出口温度与常规铸轧时基本相近的出口温度时，铸轧 厚度 薄时轧制压力比常规铸轧高，随着铸轧速度与铸轧区增大，铸轧坯厚度减薄，铸轧 辊径增大，轧制压力峰值增大。     

铝连续铸轧铸嘴型腔的数值模拟及其结构优化

采用低雷诺数k-ε湍流模型建立了一种铝合金连续铸轧使用的铸嘴型腔三维流动与传热数学模型,并对所建立的数学模型进行了计算机模拟,得出这种铸嘴型腔内铝熔体温度和速度的分布规律。通过现场温度测量实验验证,实测结果与模拟结果基本吻合。根据模拟结果,对原铸嘴边部尺寸进行改进,并对新改进的铸嘴进行模拟,结果显示与改进前相比,铸嘴型腔内部速度分布更加合理,出口处边部与中部的温度差减小了,并在实际生产中得到了验证。     

铸轧机在我国的应用及其发展趋势

介绍了连续铸轧机在我国铝加工业中的应用及发展状况、同国外铸轧机的差距，以及提高国产铸轧机装机水平的途径。同时提出超薄带坯的铸轧将是连续铸轧技术今后的发展趋势。     

电解铝液直接生产超薄箔坯料的熔体质量控制

针对电解铝液直接铸轧坯生产超薄铝箔坯料过程中所存在的质量缺陷,结合铸轧法生产铝箔坯料所采用电解铝液的特点,全面分析了生产过程中铝合金熔体处理工艺对熔体质量的影响因素,并研究制定了相应的铝熔体处理措施。有效改善了熔体质量,消除/减少了电解铝液生产超薄铝箔坯料的质量问题,实现了低成本、高效率、高品质、稳定生产超薄箔坯料的目标。     

超薄快速铸轧过程轧制压力分布的数学模型与实验研究（Ⅰ）——铸造区轧制压力分布的数学模型

超薄快速铸轧速度可达常规铸轧速度的十几倍,甚至二十几倍,在快速铸轧条件下铸造区长度将增加,其轧制压力分布对总轧制力的影响就不可忽略。因此建立该区的轧制压力分布模型是必须的,本文利用切块法推导出超薄快速铸轧过程铸造区（结晶区）内微元体静力平衡微分方程,并利用龙格-库塔法对该微分方程进行数值求解,即可求出铸造区轧制压力分布,该模型同样适用于常规铸轧条件。     

法国彼施涅公司开发超薄高速铝带坯连续铸轧技术的进展

法国彼施涅公司开发超薄高速铝带坯连续铸轧技术的进展法国彼施涅公司已在Ｎｅｕｆ—Ｂｒｉｓａｃｈ的Ｒｈｅｎａｌｕ厂安装一台Ｊｕｍｂｏ３ＣＭ双辊式超薄高速铝带坯连续铸轧机，并于１９９６年６月试车投产。该铸轧机的宽度为２０２０ｍｍ，最小铸轧带坯厚度可达１ｍｍ...     

双辊铸轧铝合金中分流块对温度场影响的数值模拟研究

文章采用有限元方法,在大型通用有限元分析软件ANSYS中建立双辊轧制模拟的三维模型。重点研究铸嘴型腔中不同分流块的数目及分布对温度场、出口温度和出口速度的影响,以及对不同工艺条件下凝固行为的分析。研究结果表明,铝熔体在单个分流块的作用下分布更加均衡,避免了宽度方向上温差过大以及流动过程中出现较大的波动,其中板带表面和心部的出口温度、出口速度均匀性对于提高铸轧铝合金板带的质量有很大影响。实验结果为初步的,为提高铸轧板带质量提供理论和技术支撑。     

铝薄带快速铸轧技术研究

常规连续铸轧工艺存在铸轧速度低、生产率不高的问题.为此,华北铝业有限公司、中南大学和涿神公司合作开发研制了中国第一台超薄快速铸轧机,于2001年12月至2006年进行了多次工业试验,成功地生产出厚度为3.0 mm的铝箔毛料,最大铸轧速度达到4.7 m/min,产能提高了20%,并生产出合格的0.007mm铝箔.这些试验对今后的工业生产有一定指导意义.     

超薄快速铸轧过程轧制压力分布的数字模型与实验研究（Ⅱ）——轧制区轧制压力的解析计算模型

超薄快速铸轧条件下轧制区内温度梯度很大,其轧制压力是温度的强耦合函数。本文在利用切块法推导出超薄快速铸轧过程轧制区的静力平衡微分方程的基础上,利用温度分布的线性假设建立了变形抗力关于位置坐标的简化模型,由此可根据铸轧条件下混合摩擦条件求出了各相应摩擦条件下的平衡微分方程的解析解,即获得轧制区轧制压力分布的解析计算模型,该模型同样适用于常规铸轧条件下的铸轧仿真研究。     

高压水除鳞喷嘴与射流特性的试验研究

在热轧板带生产尤其是薄板坯连铸连轧工艺中 ,除鳞是提高产品表面质量的关键工序之一 ,目前国内外普遍采用高压水除鳞技术。其中除鳞喷嘴的结构直接影响到射流的打击力及其分布形式 ,对除鳞效果起决定性作用。对高压水除鳞喷嘴的结构及其和水射流的特性之间的关系进行了大量的试验研究 ,总结出了射流散射角、喷射宽度方向特性、轴心打击力的变化规律 ,并对喷嘴结构参数的选择提出了见解。     

A Numerical Simulation of Transport Phenomena During the Horizontal Single Belt Casting Process Using an Inclined Feeding System

Horizontal single belt casting (HSBC) has great potential to replace current conventional continuous casting (CCC) processes for sheet metal production, by directly casting 3 to 1 mm sheet for the automobile industry. In the present paper, two-dimensional mathematical models were developed to study transport phenomena, for the case of an inclined wall feeding system for a liquid aluminum wrought alloy (AA6111). Based on the commercial software ANSYS FLUENT 14.5 and user-defined functions, a two-layer turbulence model was used to examine the fluid flow emanating from a slot nozzle set above a water-cooled, high-speed, steel belt. The Volume of Fluid (VOF) method was used to predict the shape of the melt-air interface. A transformed coordinate system (x′, y′) was established in order to analyze the fluid flow on the inclined wall of the feeding system. The total pressure gauge gradient (?p_total/?x) was used to describe the behavior of the melt film inside the slot nozzle of the head box. The modeling results show that during the melt film falling process, the total gauge pressure varies within the slot nozzle, which can decrease the stability of the falling film. The first impingement between the falling film and the inclined refractory wall of the feeding system gives rise to a local oscillation, and this influences the stability of the melt film moving downwards. At the rear meniscus position between the inclined wall and the moving belt, there is a clear vibration of the air-melt interface, together with a recirculation zone. The weak vibration of the air-melt interface could be induced by the periodic variation of the melt-air interface. Moreover, the formation of tiny air pockets is predicted. Finally, on the inclined wall of the feeding system, a suitable length of the transition area is needed to avoid over-acceleration of the melt film due to the force of gravity.     

Application of swirling flow nozzle and investigation of superheat dissipation casting for bloom continuous casing

A swirling flow nozzle (SFN) has been proposed and designed for bloom continuous casting based on the idea that the melt flow pattern in the mould region can be controlled by changing the jet direction from outlets of the submerged entry nozzle. The simulated and plant trial results show that, as compared to the conventional straight nozzle, the oversized shrinkage porosity along with centre cracking at the strand cross-section is removed, and the maximum segregation degree fluctuation range of solute element C is reduced from 0.17 to 0.05. The positive effect is attributed to the remarkable superheat dissipation effect of horizontal swirling flow generated by SFN, which is reduced by 10.6 K as compared to the normal nozzle. Moreover, the adoption of SFN can further enhance the metallurgical effect of in-mould electromagnetic stirring (M-EMS), where both better chemical homogeneity and soundness of bloom castings can be obtained by the combined adoption of SFN and M-EMS.     

Macrosegregation Improvement by Swirling Flow Nozzle for Bloom Continuous Castings

Based on mathematical model coupling electromagnetism, fluid flow, heat transfer, and solute transport, the metallurgical performances of conventional straight nozzle, swirling flow nozzle (SFN), and M-EMS have been evaluated and compared. The soundness improvement of bloom castings has been investigated by casting tests of adopting the newly designed SFN. As compared to the normal nozzle, center porosity has been eliminated along with the popular center radial crack, and a better chemical homogeneity was obtained by employing the SFN accordingly, where the maximum segregation degree of C and S at the strand cross section is decreased from 1.28 to 1.02 and from 1.32 to 1.06, respectively. Combined with the results of numerical simulation, the positive effect obtained can be attributed to the remarkable superheat dissipation under the implementation of SFN, where, compared with the normal nozzle, the melt superheat degree at the mold exit is reduced by 15.5 K, 9.8 K, and 17.3 K (15.5 °C, 9.8 °C, and 17.3 °C) under the other three casting measures of SFN, normal nozzle with M-EMS, and SFN with M-EMS, respectively.     

Effect of holding time and surface cover in ladles on liquid steel flow in continuous casting tundishes

Mathematical modeling of fluid flow and heat transfer of melt in a typical two-strand slab caster tundish has been done for a complete casting sequence. The complete casting sequence consists of 1 minute of tundish emptying period during the ladle transfer operation followed by 1 minute of tundish filling period by the new ladle and pouring at the normal operating level of the tundish for 46 minutes. The effect of varying ladle stream temperature conditions on the melt flow and heat transfer in the continuous casting tundish has been studied. When the ladle stream temperature decreases appreciably over the casting period, corresponding to heat loss of the melt in the ladle from the top free surface, the incoming melt temperature becomes lower than that of the melt in the bulk of the tundish after about 30 minutes from the start of teeming. This results in melt flow along the bottom of the tundish instead of the normal free surface directed flow. The ladle melt stream temperature shows little variability when the ladle has an insulated top. Corresponding to this situation, the temperature of the incoming melt remains higher than that of the melt in the bulk of the tundish and the normal free surface directed flow is maintained throughout the casting period. The product cast under such condition is expected to have a uniformly low inclusion content. The heat loss condition from the top of the ladle has been shown to be the dominant factor in determining fluid flow and heat-transfer characteristics of the melt in the tundish rather than the holding time of the melt in the ladle. Formerly Graduate Student, Department of Materials Science and Engineering, Ohio State University     

Design of coolant disks for the production of amorphous alloys

The thermal operating conditions of coolant disks (without internal cooling) for the production of amorphous and microcrystalline strip are analyzed. The thermal balance conditions of the disk are calculated in producing strip of different width, at different melt flow rates. It is established that such disks may be used in small machines with the casting of 2 kg of metal per working cycle. To increase the mass of cast metal and the strip width, the disk diameter or the working surface area must be increased, while the melt flow rate from the nozzle and the disk speed must be reduced.     

多孔水口对轴承钢280 mm x325 mm铸坯结晶器钢液流场和温度场的影响

采用数值模拟的方法对比分析了直通式、四孔式以及五孔式水口对GCr15轴承钢280 mm×325 mm坯连铸结晶器内钢液流场和温度场的影响。结果表明,当前常用的直通式水口对坯壳无冲刷,利于坯壳均匀生长,但钢液冲击深度大,在弯月面处速度小,不利于大方坯质量的提高。当采用四孔水口时,钢液热中心上移,钢液面处温度可提高8℃,钢液向上漩流增强,有利于降低结晶器内钢水过热及保护渣的熔化,但由于钢液对结晶器宽、窄面坯壳的冲刷致使冲击区域附近坯壳出现不同程度的零增长区域。当采用五孔水口时,除了钢液热中心上移,钢液向上漩流增强,由于侧孔钢液流速减小,对坯壳的冲刷减小,有利于保护渣的快速熔化、过热度的快速降低,坯壳的均匀生长,显著提高大方坯的质量。     

Physical and Numerical Simulation of Fluid Flow and Solidification at the Twin‐Roll Strip Casting Process

The fluid flow in a twin‐roll strip caster is investigated by physical and numerical simulation on a 1:1‐scale water model. A laser‐optical measurement technique (Laser Doppler Anemometry ‐ LDA) is used to validate the numerical results for the water flow. The numerical simulations are then transferred to the melt flow in the strip caster. The investigations are focused on different SEN concepts (submerged entry nozzle), a single‐nozzle system with two outlet ports and a double‐nozzle system with one outlet port each. The Influence of these concepts on the velocity, turbulence, and temperature distribution inside the liquid pool between the casting rolls and on the solidification and growth of the strip shells are investigated by numerical simulations (Computational Fluid Dynamics ‐ CFD). The non‐isothermal melt flow is calculated considering the solidification enthalpy as well as the behaviour of the solidifying melt. In addition to the numerical simulations of the melt flow inside the pool the temperature distribution in the cast strip is simulated. The SEN concept directly correlates with the temperature distribution Inside the strip. Furthermore, the surface temperature of the strip below the outlet of the roll gap is measured using a line‐scanner and is compared with the CFD simulation. In order to simulate the shape of the free surface in the liquid pool, CFD simulations of the water flow in the physical model are carried out using a Volume of Fluid model (VoF). This two‐phase model is able to reproduce free surface waves.     

Steel Flow into a Mold from a Submerged Nozzle with Eccentric Outputs

The flow of steel melt into a mold has not been adequately studied. In general, analysis of the melt flow is a complex mathematical problem, and accordingly numerical modeling is employed. The present work employs Odinokov’s numerical method, which is based on a finite-difference form of the initial system of equations. This method has been successfully employed in continuum mechanics; in casting to determine the stress–strain state of shell-type molds; and in solving other technological problems. That suggests its universality. In the present work, it is applied to the hydrodynamic fluxes of liquid metal when steel is cast in a mold of rectangular cross section. The use of a submerged nozzle with eccentric holes for steel supply requires a three-dimensional mathematical model describing the metal fluxes into the mold. Odyssey software is used to simulate the processes in the mold. The calculation is based on the fundamental hydrodynamic equations and the proposed numerical model. The solution is obtained numerically and takes the form of a system of differential equations. The region of interest is divided into finite elements, and the system of equations is written in difference form for each element. The result obtained is the field of metal flow velocities into the mold. A numerical approach and a corresponding algorithm are developed for solution of the system of algebraic equations obtained and are incorporated in a computation program written in Fortran-4. By means of the mathematical model, the geometric dimensions of the mold and the cross section of the exit holes in the submerged nozzle may be varied. The model clarifies the pattern of metal flows, which affects the heat transfer by the mold walls, and permits determination of the optimal parameters of metal exit from the submerged nozzle in different casting conditions. As an example, the model is applied to steel casting in a mold of rectangular cross section (height 100 cm, horizontal dimensions 2000 × 40 cm). Steel flow from the submerged nozzle is eccentric in two directions within the horizontal plane. The results of solution are presented in graphic form. The pattern of metal fluxes into the mold is shown, and the magnitude and intensity of the fluxes is determined.