软接触电磁连铸过程中结晶器及初生坯壳的传热

为了解高频磁场对软接触电磁连铸结晶器及初生坯壳传热行为的影响,用有限元二维数值模拟方法计算了软接触连铸过程中结晶器及初生坯壳的传热.得知在高频磁场（f=20 kHz）作用下,电磁场的感应加热会减少连铸初生坯壳的厚度、提高连铸坯的表面温度,并大幅度提高分瓣结晶器铜壁的温度.     

Mold Simulator Study on the Initial Solidification of Molten Steel Near the Corner of Continuous Casting Mold

Metallurgical and Materials Transactions B - Corner cracks are one of the most widespread surface defects of continuous casting slabs, and they are especially severe for peritectic steels and...     

钢的连铸过程结晶器与铸坯之间的传热分析

针对连铸过程中的结晶器传热模型，分析总结了结晶器与坯壳之间的热阻构成，并研究了结晶器壁和坯壳界面热流的影响因素，为传热模型的求解和结晶器锥度的优化设计提供了理论依据。     

Effect of Induction Heat on Initial Solidification During Electromagnetic Continuous Casting of Steel

 Aiming at the process of electromagnetic continuous casting (EMCC), a three dimensional finite element model on electromagnetic field and temperature field was developed through the commercial software ANSYS to investigate the effects of induction heat of high frequency electromagnetic field on the early solidification process of molten steel in soft contact mold under various conditions of exciting current parameters. The results show that the induction heat has significant effects on the early solidification process, which appear as increasing the billet surface temperature, thinning the initial solidified shell and lowering the starting point of the initial solidification. The increases of exciting current frequency and density make the effects of induction heat on solidification process increased remarkably. Especially, with the increase of exciting current frequency, the early solidification process and shell growth become non-uniform in billet circumferential direction. Morever, if the exciting current density exceeds a certain value, there occurs a high temperature region in the top of molten steel column, and then the initial solidification rate is decreased greatly.     

Heat Transfer and Deformation Behavior of Shell Solidification in Wide and Thick Slab Continuous Casting Mold

With the considerations of the behaviors of shell deformation, mold flux film and air gap dynamic distribution in shell/mold gap, a two dimensional slice-travel transient thermo-mechanical coupled model of simulation shell solidification in wide and thick slab continuous casting mold was developed by using the commercial program ANSYS. The evolutions of strand-mold system thermal behaviors, including the air gap formation and the mold flux film dynamical distribution in shell/mold gap and shell temperature field, and the evolutions of shell deformation and stress distribution of peritectic steel solidified in a 2120 mm wide and 266 mm thick slab continuous casting mold were analyzed. The results show that the air gap formation and the thick mold flux film distribution mainly concentrate in the regions 0–21 mm and 0–7 mm, 0–120 mm and 0–100 mm off the shell wide and narrow faces corners, and thus the hot spots are given rise to form in the regions 15–55 mm and 15–50 mm off the shell wide and narrow face corners. The shell server deformation occurs in the off-corners in the middle and lower parts of the mold. The stress evolution in shell surface is tensile stress, while that in shell solidification front is compressive stress.     

Heat Transfer and Deformation Behavior of Shell Solidification in Wide and Thick Slab Continuous Casting Mold

With the considerations of the behaviors of shell deformation, mold flux film and air gap dynamic distribution in shell/mold gap, a two dimensional slice-travel transient thermo-mechanical coupled model of simulation shell solidification in wide and thick slab continuous casting mold was developed by using the commercial program ANSYS. The evolutions of strand-mold system thermal behaviors, including the air gap formation and the mold flux film dynamical distribution in shell/mold gap and shell temperature field, and the evolutions of shell deformation and stress distribution of peritectic steel solidified in a 2120 mm wide and 266 mm thick slab continuous casting mold were analyzed. The results show that the air gap formation and the thick mold flux film distribution mainly concentrate in the regions 0–21 mm and 0–7 mm, 0–120 mm and 0–100 mm off the shell wide and narrow faces corners, and thus the hot spots are given rise to form in the regions 15–55 mm and 15–50 mm off the shell wide and narrow face corners. The shell server deformation occurs in the off-corners in the middle and lower parts of the mold. The stress evolution in shell surface is tensile stress, while that in shell solidification front is compressive stress.     

水平连铸40Cr圆坯凝固特性的研究

以40Cr圆坯水平连铸工艺为研究对象,采用射钉试验、红外测温试验、硫印试验及酸浸低倍试验研究了40Cr圆坯的凝固传热过程.通过本研究得出40Cr圆坯在拉速V=1.99(m/min),浇注温度T=1544℃,中间包过热度AT=52℃的拉坯参数下,钢坯的液芯长度为L=17.47m,铸坯的中心疏松为1.5级,中心裂纹为1.5级.试验结果表明,射钉法可以有效分析连铸坯的凝固传热过程,为高效连铸生产提供可靠的理论参考.     

A 3D Mathematical Modeling on Meniscus Solidification and Heat Transfer in Continuous Casting Chamfered Mold of Slab

Herein, a 3D mathematical model is established to elucidate the meniscus solidification and heat transfer in the chamfered mold. The fluid flow, heat transfer, the solidification of steel, the oscillation of the mold, and the steel–slag interfacial tension are considered, and the meniscus behavior on different longitudinal sections and cross sections is discussed. Under the influence of the upper roll flow, the height of the steel level increases from submerged entry nozzle to narrow face, which affects the distribution of the oscillation mark on the surface of the shell. With the mold chamfer and two new corners, the thickness of the slag film at the corner 1 with angle of 123.7° is the largest, and the shell thickness is the smallest, which is related to the 3D profile of the meniscus near the corner. The largest heat flux is located at 10–14 mm below the initial level of liquid steel and is below 3.0 MW m⁻². The heat flux at the corner 1 with small obtuse angle is the smallest on the same cross section, indicating that small obtuse angle near the corner resulted in the low heat transfer.     

连铸结晶器保护渣渣膜传热特性研究进展

传统保护渣主要以CaO和SiO₂为基料,辅以适量助熔剂如CaF2等构成;而无氟保护渣则是选用B₂O₃、TiO₂等合适的助熔剂来替代CaF₂达到绿色环保的目的。从保护渣的碱度、化学成分和结晶性能三方面,分别综述了传统含氟渣系CaO-SiO₂-CaF₂和新型无氟渣系CaO-SiO₂-B₂O₃、CaO-SiO_2-TiO₂渣膜传热的影响规律,总结了近十年来冶金工作者对含氟和无氟保护渣渣膜传热的研究成果,得出无氟保护渣结晶矿相中硅硼酸钙和钙钛矿与传统保护渣中枪晶石具有相似的结晶行为,B₂O₃和TiO₂的含量在4%~8%和3%~11%可有效控制传热,从而减少铸坯纵裂纹的发生。并提出了开发新型高效无氟保护渣的进一步研究方向,即无氟渣中氟化物替代物的迁移赋存规律对渣膜传热性能的影响机理。     

单辊薄带连铸凝固传热数学模型

本文以单辊薄带连铸机为研究对象,通过建立传热数学模型,结合热态试验,找出带厚与工艺因素之间的关系,从而为生产出较好质量带坯提供工艺参数。     

水平连铸结晶器内真实换热边界计算及传递模型

连铸结晶器内冷却水的流动、传热和金属液的传热、凝固全耦合计算时,模型计算效率低、收敛性差,而不考虑真实冷却水流场只进行金属液传热-凝固耦合时,模型计算精度较低,可将冷却水流动-传热和金属液传热-凝固过程分别建模,并基于二次开发的温度场量原位传递程序,将模型串联耦合。结果表明,通过耦合流场计算得到的真实冷却边界替代传统均匀界面换热系数的边界条件施加方式,在保证模型计算效率和计算精度的前提下,可准确模拟铸坯晶粒的尺寸、取向和数量,经试验验证,模拟结果与试验结果高度吻合。     

A Study for Initial Solidification of Sn-Pb Alloy During Continuous Casting: Part II. Effects of Casting Parameters on Initial Solidification and Shell Surface

The initial shell solidification of liquid steel in the mold has significant influence on both surface and internal quality of the final slab, and it is mainly determined by the high transient high temperature thermodynamics occurring in the mold. This study investigated the effects of casting parameters like casting temperature, mold oscillation frequency, and stroke on the initial solidification of a Sn-Pb alloy through the use of a mold simulator to allow the clear understanding of the inter-relationship between irregular shell solidification, heat transfer, negative strip time (NST), and casting conditions. Results suggested that the shell surface oscillation marks (OMs) are strongly depending upon the fluctuations of meniscus responding temperatures and heat flux. An abrupt sudden fluctuation of high frequency temperature and heat flux at the meniscus during the NST would deteriorate the shell surface and leads to deep OMs. The fluctuations of responding temperature and heat flux are determined by the NST, meniscus solidification, and oil infiltration, which in turn are influenced by casting conditions, like casting temperature, oscillation frequency, stroke, etc.     

方坯连铸凝固传热的复合数值模拟

根据连铸机特点和铸流场特性，在拉坯方向上将整个铸流长度划分为上部计算域和下部计算域。对于铸坯温度场的数值模拟，上部计算域充分耦合钢液对流对传热的影响，采用了三维稳态流动传热耦合模型；下部计算域则将铸流场对传热的影响考虑为有效导热系数，并忽略拉坯方向上的传热效果，采用了二维非稳态有效导热系数模型。计算过程和结果表明，采用此复合模拟方法保证了数值模拟的准确性并降低了仿真程序的计算成本。     

Influence of Electropulsing Treatment on the Initial Solidification of Molten Steel During Continuous Casting

Metallurgical and Materials Transactions B - An electropulsing-assisted mold simulator (EPMS) technique was developed to investigate the effect of pulsed electric current on the initial...     

Study of the Effects of the Mold Surface and Solid Mold Flux Crystallization on Radiative Heat Transfer Rates in Continuous Casting

Radiative heat transfer plays a crucial role in the meniscus area of a steel continuous casting machine. However, the study of radiation across the mold flux and copper molds is very difficult due to the harsh environment and highly transient nature of the phenomena in continuous casting molds. By using an infrared radiation emitter, a radiative heat flux was able to be applied to a copper mold with different top surfaces to observe their effects on the radiative heat transfer. The mold surface was covered with solid slag disk subjected to the radiative heat flux to simulate the radiative heat transfer phenomena in continuous casting. The solid slag disk could either be glass or a mixture of glass and precipitated crystals. The effect of full crystallization of a slag disk was to reduce the heat transfer rate by 20.5%, as compared with a completely glassy sample.     

基于Fluent对水平连铸结晶器温度场分布及传热的研究

以水平连铸圆坯连铸生产工艺为研究对象,采用Fluent数值模拟软件凝固传热模型并结合射钉试验共同研究了管坯在不同拉坯工艺条件下,结晶器内的温度场分布与凝固传热过程,并对不同拉坯参数下铸坯试样进行了检测分析。研究发现：水平连铸拉坯工艺参数：拉速V=2．13m／min,浇注温度T=1544℃,中间包过热度△T=40℃的拉坯参数下,结晶器内的温度场分布均匀稳定,铸坯质量好,产量高。研究表明,采用Fluent数值模拟软件凝固传热模型并结合射钉试验可以有效分析在不同拉坯工艺条件下水平连铸结晶器内的温度场分布及凝固传热过程,并进一步制定合理的拉坯工艺参数,降低管坯质量缺陷的发生,提高铸坯质量。     

Study of the Effect of Mold Corner Shape on the Initial Solidification Behavior of Molten Steel Using Mold Simulator

The chamfered mold with a typical corner shape (angle between the chamfered face and hot face is 45 deg) was applied to the mold simulator study in this paper, and the results were compared with the previous results from a well-developed right-angle mold simulator system. The results suggested that the designed chamfered structure would increase the thermal resistance and weaken the two-dimensional heat transfer around the mold corner, causing the homogeneity of the mold surface temperatures and heat fluxes. In addition, the chamfered structure can decrease the fluctuation of the steel level and the liquid slag flow around the meniscus at mold corner. The cooling intensities at different longitudinal sections of shell are close to each other due to the similar time-average solidification factors, which are 2.392 mm/s^1/2 (section A-A: chamfered center), 2.372 mm/s^1/2 (section B-B: 135 deg corner), and 2.380 mm/s^1/2 (section D-D: face), respectively. For the same oscillation mark (OM), the heights of OM roots at different positions (profile L1 (face), profile L2 (135 deg corner), and profile L3 (chamfered center)) are very close to each other. The average value of height difference (H_D) between two OMs roots for L1 and L2 is 0.22 mm, and for L2 and L3 is 0.38 mm. Finally, with the help of metallographic examination, the shapes of different hooks were also discussed.