连铸喷淋结晶器的传热数学模型

针对铸坯在结晶器内的凝固特性，建立了喷淋冷却结晶顺的传热数学模型。并数值计算了普通循环水冷结晶器与喷淋冷却结晶器的冶金参数，讨论分析，比较了两种冷却方式的冶金效果。     

小方坯连铸机喷淋结晶器的研究

建立小方坯喷淋结晶器凝固传热数学模型，模拟计算了铸坯温度场、坯壳厚度、热流场，坯壳与铜壁间气隙厚度。计算坯壳厚度与实测坯壳厚度基本吻合；与普通水缝式结晶器相比，铸坯温度场均匀，坯壳厚度均匀，冷却强度有所提高。     

连铸喷淋冷却结晶器的应用及研究

涟钢三炼钢厂小方坯连铸机采用了喷淋冷却结晶器,研究分析了拉速、中间罐浇铸温度、水压与水流量对该结晶器平均热流量的影响,以及水质对喷淋冷却结晶器的影响。使用这种结晶器后,连铸的产量及铸坯质量大大提高。     

喷淋结晶器的研究开发和应用

本文介绍了国内第一台小方坯连铸机喷淋水冷管式结晶器的研究开发和应用情况。这种新型结晶器采用射流冲击强化传热技术,冷却强度高,并且按铸坯凝固传热的工艺要求分段控制冷却强度,实现了“无压力”冷却。     

连铸喷淋结晶器的传热实验研究

在冷态实验基础上，对喷淋冷却结晶器进行了传热实验，根据实验结果，对结晶器温度，热流，换热系数，水流密度等参数之间的相互影响关系进行了分析，讨论；为喷淋结晶器的设计，工业应用提供了理论依据。     

含硫45钢铸坯缺陷分析与工艺优化

含硫45钢(/%:0.42～0.50C,0.17～0.37Si,0.50～0.80Mn,≤0.035P,0.035～0.045S)的Φ44 mm轧材探伤合格率低,轧材表面存在裂纹缺陷,通过分析是由150 mm×150 mm铸坯缺陷导致的。对铸坯表面酸洗发现裂纹缺陷,采用金相显微镜对裂纹进行分析。分析认为是由结晶器铜管R角太小、角部冷却太强、保护渣熔化不好、传热和润滑效果差以及二次冷却不均匀导致的。通过对结晶器铜管、保护渣及二次冷却水量进行工艺优化,改善结晶器冷却传热和二冷段喷淋冷却效果,提高铸坯冷却均匀性,使得铸坯缺陷明显改善,轧材合格率大幅提高。     

方坯结晶器

1 前言 结晶器是连铸机中最重要的部件之一。从传热学角度讲,它是个热交换器,由流经它的冷却水带出钢水凝固潜热,使钢水凝固成具有一定厚度坯壳的铸坯。结晶器对铸坯表面质量优劣,连铸生产正常与否有着直接和重要的关系。 对结晶器的技术要求,主要包括以下几个方面: (1)传热性能好,冷却强度可调钢水在结晶器内凝固成坯壳,其传热路     

日本住友金属公司开发用高速水膜强冷铸坯的新型结晶器

1前言采用一般间接冷却型结晶器进行高速连铸时，因铸坯收缩形成的铸坯表面与结晶器内壁间的气隙增大了传热阻力（结晶器出口处的导热系数仅为450～800W／m2K），高温且薄的凝固壳难于承受钢水静压力；现用的喷雾冷却也不易确保对铸坯的高冷却能力。为了在高速连铸时强冷结晶器下部铸坯，住友公司将其开发的上下两段结构新型结晶器用于0．17％C钢的板坯连铸试验，获得了良好的效果。2新结晶器构造上段仍采用间接冷却方式，长400。。m、断面尺寸24OXSOmm；下段用螺栓和支撑七段的框架相连结，在铸坯的各宽面各设置3块，各窄面各设置1块共…     

连铸坯凝固过程中传输现象基础知识系列讲座 第十七讲 影响结晶器传热的因素

结晶器传热是连铸过程中最为复杂和重要的现象之一。影响结晶器传热的因素很多，如铸坯的拉速、钢的成分以及结晶器的结构等。合理地控制结晶器的传热状态，对提高铸坯产品质量、防止漏钢起着十分重要的作用。     

连铸坯凝固过程中传输现象基础知识系列讲座

在连铸过程中吉晶器的传热速度对铸坯的表面质量和防止漏钢都具有十分重要的影响。介绍了结晶器的传热机制，并对结晶器热流的特点进行了总结和分析。     

中薄板坯高拉速连铸结晶器平均热流研究

对引进的中薄板坯高拉速铸机结晶器平均热流进行了研究，分析了拉速、冷却水量、结晶器锥度、浇注温度等因素对平均热流的影响，并对其一些传热特点进行了讨论。     

铸模工艺及浇铸控制对铜模使用寿命的影响

铜模使用寿命是阳极板浇铸除合格率外的另一重要指标参数,影响吨铜生产成本。本文简要从铸模过程、铜水温度控制、铜水成分控制、冷却水喷淋控制及喷涂液五个方面阐述对铜模使用寿命的影响。高纯度、低杂质的铜水是确保铜模使用寿命的前提,铜水浇铸温度控制在1200±10℃,浇铸模温保持在120℃~180℃,规范的铸模过程控制及适宜的铜水温度是铜模浇铸成功的基础,精准的冷却水喷淋系统控制和有效的喷涂效果是提高铜模使用寿命的关键保证。     

连续铸钢过程中结晶器的传热研究

 为了研究结晶器内壁温度的分布,设计了模拟结晶器工作过程的实验装置,并进行了实验。实验结果表明,结晶器内壁温度趋近于冷却水温度。基于实验,推导了结晶器边界等效导热系数。该系数用于解决金属和冷却水之间的传热,即反映结晶器的传热能力。用等效导热系数处理结晶器的边界传热,对包括结晶器在内的连铸凝固进程温度场进行数值模拟既简单又方便,并且计算结果与实验结果符合。还讨论了拉坯速度和冷却水流量对结晶器温度场的影响。     

Two-dimensional heat transfer model for secondary cooling of continuously cast beam blanks

Abstract

A two-dimensional heat transfer model was developed for the secondary cooling system during beam blank continuous casting. The finite element method was used to calculate the heat transfer. Accurate cooling boundary conditions in the secondary cooling zone are involved, including spray water cooling, water evaporation cooling, radiation cooling and roll contact cooling in the casting direction and non-uniform distribution of spray water flow density in the cross-section. The causes of longitudinal crack at the fillet during Q235 steel continuous casting were analysed on the basis of the simulation of the developed model, and then the spray water flow and the transverse nozzle layout were optimised. Practical results show that the surface quality of the beam blank improved after optimisations. Numerical results from the present model were validated using previous experimental measurements, which show good agreement.     

冷却工艺对高速连铸结晶器传热的影响

为了分析冷却水的供水工艺对结晶器铜壁和冷却水温度场的影响,基于结晶器铜壁热电偶实测温度,构建铸坯/铜壁传热反问题和铜壁/冷却水正问题数学模型,采用ANSYS建立铸坯/铜壁/冷却水数值分析模型,对薄板坯结晶器温度场进行耦合传热分析,解析不同冷却工艺对高速薄板坯连铸结晶器内传热行为的影响.结果表明,水缝内冷却水流动方向对铜...     

Heat Withdrawal in the Mold in Continuous Casting of Steel. Review and Analysis

Two principal methods are used to investigate the heat transfer in the continuous casting mold. The direct way is to measure cooling water temperatures, mold wall temperatures, strand temperatures and shell thickness in actual operation, and then deduce from these data the correlations for heat flux densities. The other way is to investigate the “unit operations” of heat transfer theoretically or experimentally in the laboratory, viz. heat transfer through a layer of casting flux or of gas, and heat transfer in a copper wall cooled on one side by water. The results obtained in this approach can then be used to explain the data determined with the direct method and to optimize the heat transfer behaviour of the mold in the machine. In the first part of this paper some unit operations are discussed and engineering formulae are given for computation of the heat resistances of the gap and the copper/water system. In the second part of the paper the available operational data on heat flux density are analysed. Algorithms are presented for computation of local and average heat flux density as functions of casting speed, carbon content of the steel and composition of the casting flux. Finally, values of shell thickness are computed with the correlation for heat flux density and are compared with the measured data.     

The use of water cooling during the continuous casting of steel and aluminum alloys

In both continuous casting of steel slabs and direct chill (DC) casting of aluminum alloy ingots, water is used to cool the mold in the initial stages of solidification, and then below the mold, where it is in direct contact with the newly solidified surface of the metal. Water cooling affects the product quality by (1) controlling the heat removal rate that creates and cools the solid shell and (2) generating thermal stresses and strains inside the solidified metal. This work reviews the current state-of-the-art in water cooling for both processes, and draws insights by comparing and contrasting the different practices used in each process. The heat extraction coefficient during secondary cooling depends greatly on the surface temperature of the ingot, as represented by boiling water-cooling curves. Thus, the heat extraction rate varies dramatically with time, as the slab/ingot surface temperature changes. Sudden fluctuations in the temperature gradients within the solidifying metal cause thermal stresses, which often lead to cracks, especially near the solidification front, where even small tensile stresses can form hot tears. Hence, a tight control of spray cooling for steel, and practices such as CO₂ injection/pulse water cooling for aluminum, are now used to avoid sudden changes in the strand surface temperature. The goal in each process is to match the rate of heat removal at the surface with the internal supply of latent and sensible heat, in order to lower the metal surface temperature monotonically, until cooling is complete.     

莱钢4^#矩形坯连铸机二冷水动态控制模型

根据传热学原理,研究从钢水进入结晶器后开始,经过二冷段冷却成铸坯这一阶段的热传导状态,建立传热模型,然后采用差分方法对传热模型进行数字化处理,形成可用于过程控制的连铸机二冷水动态控制模型。该模型在莱钢4^#连铸机上得到具体实现,并取得良好控制效果。     

Determination of interface heat transfer coefficient between aluminum casting and graphite mold

To produce castings of titanium, nickel, copper, aluminum, and zinc alloys, graphite molds can be used, which makes it possible to provide a high cooling rate. No die coating and lubricant are required in this case. Computer simulation of casting into graphite molds requires knowledge of the thermal properties of the poured alloy and graphite. In addition, in order to attain adequate simulation results, a series of boundary conditions such as heat transfer coefficients should be determined. The most important ones are the interface heat transfer coefficient between the casting and the mold, the heat transfer coefficient between the mold parts, and the interface heat transfer coefficient into the environment. In this study, the interface heat transfer coefficient h between the cylindrical aluminum (99.99%) casting and the mold made of block graphite of the GMZ (low ash graphite) grade was determined. The mold was produced by milling using a CNC milling machine. The interface heat transfer coefficient was found by minimizing the error function reflecting the difference between the experimental and simulated temperatures in a mold and in a casting during pouring, solidification, and cooling of the casting. The dependences of the interface heat transfer coefficient between aluminum and graphite on the casting surface temperature and time passed from the beginning of pouring are obtained. It is established that, at temperatures of the metal surface contacting with a mold of 1000, 660, 619, and 190°C, the h is 1100, 4700, 700, and 100 W/(m² K), respectively; i.e., when cooling the melt from 1000°C (pouring temperature) to 660°C (aluminum melting point), the h rises from 1100 to 4700 W/(m² K), and after forming the metal solid skin on the mold surface and decreasing its temperature, the h decreases. In our opinion, a decrease in the interface heat transfer coefficient at casting surface temperatures lower than 660°C is associated with the air gap formation between the surfaces of the mold and the casting because of the linear shrinkage of the latter. The heat transfer coefficient between mold parts (graphite–graphite) is constant, being 1000 W/(m² K). The heat transfer coefficient of graphite into air is 12 W/(m² K) at a mold surface temperature up to 600°C.