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1.
基于建立的连铸中间包及结晶器内钢液混合过程的物理模型,开发了板坯连铸异钢种连浇过程混浇坯长度及成分变化模型。以某钢厂单流板坯连铸机220 mm×1560 mm断面Q235与Q335Ti钢的混浇过程为研究对象,采用水模型试验结合数值模拟确定模型的关键参数,并通过开展现场试验对混浇坯取样验证模型的准确性。结果证明:混浇坯成分取样与模型预测的成分偏差小于5%,且模型预测的混浇坯长度与人工确定的一致。故采用该模型可跟踪不同混浇工况下中间包内及铸流上钢液的混合行为,准确预测混浇坯的长度以及成分变化规律。采用该模型研究了拉速及中间包内剩余钢液质量对混交坯长度及不同浇注长度铸坯C元素质量分数变化的影响规律。发现当拉速保持不变时,中间包内剩余钢液越多,混浇坯越长;当中间包内剩余钢液质量保持不变时,拉速越大混浇坯越短。相比而言,中间包内剩余钢液质量比拉速对混浇坯长度的影响更大。另外当拉速不变时,随着中间包内剩余钢液质量的增加,C元素质量分数由0.16%变化到0.18%的速率减慢;当中间包内剩余钢液质量不变时,随着拉速的增加,C元素质量分数由0.16%变化到0.18%的速率增加。因此异钢种连浇过程,适当提高拉速以及减少中间包内剩余钢液质量,可有效减少混浇坯长度,成分变化速率降低。 相似文献
2.
Mathematical models have been developed and applied to investigate the composition distributions that arise during steel grade
changes in the continuous slab casting processes. Three-dimensional (3-D) turbulent flow and transient mixing phenomena in
the mold and the strand were calculated under conditions corresponding to a sudden change in grade. The composition distribution
in the final slab was then predicted. Reasonable agreement was obtained between predicted and experimental concentration profiles
in the slab centerlines. Intermixing in the center extends many meters below the transition point, while intermixing at the
surface extends above. Higher casting speed increases the extent of intermixing. Mold width, ramping of casting speed, and
nozzle design have only small effects. Slab thickness, however, significantly influences the intermixing length of the slab.
The axial transport of solute due to turbulent eddy motion was found to be many orders of magnitude greater than molecular
diffusion and thus dominates the resulting composition distribution. Different elements, therefore, exhibited the same mixing
behavior under the same casting conditions, despite having different molecular properties. Numerical diffusion caused by the
finite difference schemes was investigated and confirmed to be much less important than turbulent diffusion. In the lower
portion of the strand (lower than 3 m below the meniscus), the convection and diffusion can be reasonably approximated as
one-dimensional (1-D) axial flow. 相似文献
3.
For a two‐strand slab caster and a tundish capacity of 50 t the transition zone between two heats of different chemical composition was experimentally defined. The distribution of various elements was measured. The transition curves also show the penetration depth of the casting stream using a bifurcated submerged nozzle. This is basic information for the calculation of the mixing zone. Knowledge of the permissible composition ranges permits optimisation of the usable length of the strand. The impact of ladle change on oxide cleanness is analysed as well. 相似文献
4.
The flow characteristic and temperature characteristic of steel liquid in tundish at asymmetric casting were studied using SolidWorks, ANSYS, etc.It has an important impact on flow field in tundish for asymmetry casting of conticaster, which can lead to the change of tundish temperature distribution. When a strand of conticaster on one side is closed, the flow rate of steel liquid can be reduced and more backflow regions can be formed in this side of tundish. Simultaneously, the region of lower temperature steel liquid in middle part of tundish moves to the other side obviously, and the phenomenon is more noteworthy when an edge strand of conticaster is closed. 相似文献
5.
The mixing process in a 1:3 scaled water model of a single‐strand tundish for the production of stainless steel is investigated using the combined DPIV/PLIF (Digital Particle Image Velocimetry/Planar Laser Induced Fluorescence) technique. The velocities in the water model are measured in different light sheet planes up to a size of 300 mm · 1100 mm by the conventional DPIV method. The variation of the time‐dependent concentration field is measured in the same plane by the PLIF method. The tracers are polyamide particles for DPIV and a rhodamine 6G solution as fluorescent dye for PLIF. Due to the special calibration procedure of the DPIV/PLIF system, the optical, geometrical and physical parameters do not have to be determined analytically, thus leading to reliable results. The experiments are carried out with a turbulent Reynolds number of Re = 5000 and show that the mixing process correlates with the quasi steady‐state flow pattern. The residence time of some water region in the tundish model is significantly longer than the mean residence time (θ < 5). Such information is important for the steel production because the number of mixed slabs produced during sequence casting with a grade change is closely related to the mixing of the tundish melt. The presented laser‐optical investigations have been used to establish the combination of DPIV and PLIF technique. The results of combined DPIV/PLIF measurements will be used to validate numerical simulations of the mixing processes in water models of metallurgical reactors. 相似文献
6.
Alexander Braun Marek Warzecha Herbert Pfeifer 《Metallurgical and Materials Transactions B》2010,41(3):549-559
This article presents computational and water model studies of the three-dimensional turbulent fluid flow in a two-strand
tundish for steady-state and transient casting conditions. First, it presents the flow field measurements obtained at a 1:3-scale
water model of the tundish with the particle-image velocimetry (PIV) method during steady-state casting. The PIV measurements
were performed using the Reynolds-similarity criterion. Thereafter, numerical simulation is carried out with the computational
fluid dynamic software, FLUENT, using the realizable k-ε turbulence model. The numerical model is validated using the measurement results obtained with the water model. The results
of the numerical calculations are in good agreement with the PIV measurements. On this basis, the validated numerical model
is adapted to simulate the 1:1-scale steel flow with boundary conditions that are derived from the real casting process. The
nonisothermal, unsteady numerical calculations concerning the cooling process of steel melt inside the tundish are done for
a 1:1-scale industrial facility—a 69-t two-strand tundish with a 380-t ladle. The influence of transient boundary conditions
at the outlet of the tundish (one blocked strand) on the flow structure and mixing process of fluid during the casting process
are investigated. The evaluation of the flow structure is performed using a zonal method, which relates the fluid flow with
the mixing processes. 相似文献
7.
摘要:多流中间包各流钢水流动与温度状态差异是造成高端特殊钢连铸坯质量一致性差的重要原因之一。针对国内某钢厂特殊钢大方坯连铸用4流T型中间包边部流和中部流实测温差较大问题(4~7℃),基于实际工况特点,进行了中间包冶金行为的热流体动力学数值模拟研究,揭示了原型中间包边流水口响应慢及各流一致性差的原因;提出一种控制钢水流动和流间温差的内腔结构改进措施,可使包内钢液温度均匀性得到明显改善。其中,理论最小流间温差可降低到1℃以内,实测流间温差在0~3℃之间,较原型大大减小。同时指出,基于热流体动力学数值模拟优化中间包结构、提升多流中间包全铸流冶金效果一致性在特殊钢长材生产中具有重要意义。 相似文献
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随着钢铁工业的发展,人们对钢的质量要求越来越高,连铸中间包结构是和连铸坯最终质量形成相关的一个重要因素。试验以某厂四流小方坯中间包为原型,1∶3的比例制作了有机玻璃水模型,在不同的中间包结构下,KCl做示踪剂,采用"刺激—响应"技术测得流体的平均停留时间;黑墨水做显示剂显示流场。试验结果表明:采用"V"型挡墙开两孔时,钢液的平均停留时间短,滞止时间短,死区体积比例大。"V"型挡墙只开上孔时,能够很好的优化中间包,改善钢液的流动状态,使钢液的平均停留时间延长58.85 s,死区体积比例减小10.06%;同时还保证了各流之间的均匀性,即各流之间的温度、成分差异较小。 相似文献
10.
通过建立连铸中间包钢液混合的数学模型,推导出连铸过程中钢液过渡状态成分的数学公式,分析了其变化的规律,提出了控制连铸坯质量的建议. 相似文献
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The paper shows the results of the research obtained by physical and mathematical modeling of steel flow and mixing in the tundish. Two‐strand continuous casting tundish was under consideration. It has been working in one of polish steel plants. The change of concast slab assortment was caused by the changeable market terms. So, the tundish with the new system of steel flow controller was needed. Up to now baffles with the notch have played this role. Their placement cause the excessive consumption of the lining of the tundish front line. As a consequence the turbulence inhibitor (TI) was applied. Four different types of this inhibitor were designed. As a result of the experimental measurements and numerical simulations, the RTD curves of F‐type were obtained. Basing on these curves time constants for examined types were determined. Additionally, the research results were complemented by the E‐type curves. The percentage participations of dead volume flow, dispersed plug flow, and well‐mixed volume flow were calculated. The research gives possibility to estimate the designed TIs and their influence on the tundish work. 相似文献
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Marcela B. Goldschmit Sergio P. Ferro Guillermo F. Walter Virginia G. Aranda Jorge A. Tena Morelos 《Metallurgical and Materials Transactions B》2001,32(3):537-546
The grade transition process in a four line round billets continuous caster was analyzed. A numerical model was developed
to determine, quickly and accurately, the length and location of intermixed steel in the bar. The model is based on “tank
in series” or “volumes” mathematical models and was calibrated with physical water model measurements and full three-dimensional
(3-D) turbulent numerical calculations. Comparison of the model with measurements performed on intermixed steel bars is also
presented. The good agreement between these plant measurements and the numerical results validated the model. The model was
implemented on PCs with a visual interface that allowed the easy input and output of data, and the program is operated in
a steel shop. Finally, the code was employed to evaluate different strategies to fill the tundish during grade transitions.
The “double dilution” process, which consists of filling the tundish in two steps, proved to be useful to reduce the amount
of downgraded steel. 相似文献
15.
Induction heating (IH) electromagnetic field has a significant positive effect on the uniform temperature distribution in tundishes and decreases molten steel superheat to improve the quality of billets in continuous casting. To achieve the effect of electromagnetic force and Joule heating for molten steel in a channel-type IH tundish, a magnetohydrodynamic model is developed and validated by industrial experiment data. The molten steel in the tundish channel has a rotating velocity under the off-centre electromagnetic force. Its flow pattern consists of two contra-rotating vortices close to the outlet zone of the channels. The upper and lower vortices in the tundish channel change with time. The temperature distribution in the cross-sections is almost stable, and the maximum temperature increases by 30.1°C. Molten steel runs upward after flowing past the tundish channel, whose density decreases because of IH. The upward motion changes when the electromagnetic force acts on the molten steel. Results reveal that electromagnetic force has a significant effect on the flow of molten steel in the tundish, and that flow pattern varies in the tundish with or without electromagnetic force under Joule heating. 相似文献
16.
Lifeng Zhang 《国际钢铁研究》2005,76(11):784-796
Inclusions in the steel in a four‐strand continuous casting tundish, billet and wire products are firstly investigated with industrial trials, and the fraction of inclusions removed in terms of total oxygen in the tundish is measured. Then the 3‐dimenional fluid flow, heat transfer and inclusion motion in the tundish are numerically simulated. The κ‐? two‐equation model is used to model turbulence. Inclusion motion and trajectories are calculated by considering drag force and buoyancy force, coupling the effect of turbulent fluctuation (Random Walk Model). The effect of strands‐blocking on the fluid flow, heat transfer and inclusion removal is studied. A new design of tundish is proposed focusing on removing more inclusions from the molten steel. 相似文献
17.
Minimization of transition slabs in continuous casting operations is critical for optimum quality and productivity. The number of these slabs is closely related to the tundish geometry and operating practice. Therefore, tundish flow and mixing with various tundish configurations and different tundish operating levels are investigated through computer simulation. Residence time distributions and transitional concentration profiles are predicted. Finally, practical operations for a grade change to reduce transition slabs are assessed. 相似文献
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《钢铁冶炼》2013,40(3):159-166
AbstractIn the continuous casting process, the tundish acts as a continuous molten steel distribution vessel. The importance of the tundish during the molten steel delivery becomes more significant when it supplies liquid steel to more than one mould. In the present work, a water model of a six strand billet caster tundish has been used to study the effect of strand blockage on the residence time distribution (RTD) characteristics at the strands. All the experiments were performed under steady state conditions. Potassium chloride was used as a tracer for the study. The effects of blockage on the strand dissimilarity among the open strands were also studied. Both single and dual strand blockage experiments were performed. Blockage of strands deteriorated the RTD characteristics at the open strands. The results reveal the most preferred options for strand blockage when the plant operation needs to do so. 相似文献
20.
通道式感应加热是近年来得到快速推广应用的中间包冶金新技术,其通道常为直通式结构。然而对于多流狭长型中间包,这种结构会造成包内各流钢水流动和温度差异大,从而影响铸坯质量的稳定性和一致性。为此,提出了一种分口通道结构,并以国内某钢厂一需要改造的6流中间包为原型,通过物理模拟方法探究了通道孔径、角度等对钢水流动的影响,且与常规直通道结构进行了对比。结果表明,分口两孔径分别为90、60 mm并配合挡坝结构的A1D方案可明显改善整个中间包的流动均匀性,各水口RTD曲线几乎重合。该结构应用于某厂重轨钢生产,铸坯质量稳定,各流钢水温差为0~3 ℃,取得了良好的应用效果。研究为该类中间包的结构设计提供了新的思路和方法,同时也表明传统的物理模拟方法仍可用于指导感应加热中间包的设计和优化。 相似文献