【作者】 唐玲；

【导师】 姚曼； 王旭东；

【作者基本信息】 大连理工大学 ， 材料加工工程， 2012， 硕士

【摘要】 结晶器是连铸机的核心部件,实时、准确地了解结晶器传热、铸坯凝固及保护渣润滑状态,对于稳定和提高铸坯表面质量具有重要意义。目前,针对结晶器内传热与保护渣润滑行为的研究已取得很大进展,但大部分都在理想状态下进行,计算结果往往呈现均匀对称特征,不能真实反映实际工况。随着近年来结晶器“可视化”和“智能化”概念的提出,连铸现场对数值模拟准确性和实时性也提出了更为严苛的要求。针对上述问题,本文以板坯连铸结晶器为研究对象,建立了针对实测的结晶器传热反问题模型与方法,并采用基于OpenMP的并行计算技术,解决在线数值模拟“准确性”和“实时性”间的矛盾,开发出面向在线的连铸反问题方法。将模型应用至不同钢厂与铸机类型的离线模拟与在线检测,对方法的可行性和正确性进行论证。在此基础上,建立保护渣热态润滑模型,研究结晶器内保护渣膜的分布和润滑状态,讨论不同工艺及保护渣物性参数对结晶器内润滑行为的影响。最后,通过定义非均匀性评价方法和坯壳生长速率,分析并考察了结晶器内传热与润滑的非均匀性特征。基于实测的板坯连铸结晶器温度数据,建立传热反问题模型,结合OpenMP并行计算技术,划分结晶器和铸坯区域分配到4个CPU进行并行计算。结果表明,测点的温度计算值和实测值较为吻合,能够较为准确地反映结晶器内的传热状态；并行后的计算时间约为原来的1/4,基本满足在线计算的速度要求。目前嵌入反问题模型的结晶器监控集成系统已在钢厂调试运行,初步实现结晶器内温度、热流、铸坯凝固行为的在线可视化,对于预测铸坯裂纹、指导和优化连铸生产工艺具有积极意义。在温度场计算结果的基础上,建立保护渣热态润滑模型,计算结晶器/铸坯间的渣膜和气隙厚度分布。研究表明,针对本文计算的包晶钢种,液渣膜的分布与铸坯表面温度分布一致,结晶器上端的液渣膜厚度较厚,量级为0.1mm。随着铸坯表面温度降低,液渣膜逐渐消失。固渣膜较厚,约为0.5mm,在结晶器出口附近将高于1mm。保护渣熔化温度与黏度对渣膜分布影响显著,液渣膜厚度随拉速升高而变薄。此外,本文还尝试了一种计算结晶器/铸坯间气隙的新方法,为研究气隙行为提供新的思路。定义了结晶器内传热和润滑非均匀性的评价方法和坯壳生长速率,分析结晶器内传热的非均匀性特征。结果表明,弯月面附近坯壳厚度非均匀性波动较大；距离弯月面0-200mm的区域,坯壳生长速率波动剧烈且达到最大值。结晶器温度、热流、坯壳厚度和液渣膜厚度的不均匀性均随拉速增大,坯壳生长速率也随拉速的升高而增大。更多还原

【Abstract】 The mould is the core component of continuous caster. Understanding the status of heat transfer, solidification and lubrication within the mould exactly in real-time is very important for improving the slab’s quality. At present, there have been many researches about the heat transfer and lubrication behaviors in the mould, but most of them are studied under the idea condition, the calculated results of which are uniform and can’t reflect the real casting condition. With appearance of the conceptions of visualization and intellectualization in continuous casting, the’accuracy’and’real-time’of numerical simulation are more important at production field.In this paper, the mould of continuous slab caster is taken as the research object. Based on the measured data of mould temperature, an inverse problem model is established to analyze the mould heat transfer and the strand solidification. And combining the parallel technology of OpenMP, the conflict of accuracy results and quick computation will be resolved. Corresponding software is developed and applied to different plant and caster for off-line simulation and on-line detection, in order to verify the feasibility and validity of the model. Then the mathematical model of thermal state of slag lubrication is built to study the distribution of slag film and lubrication states, and the influence of process condition and physical properties of powder is also discussed. At last, the relative root mean square (rRMS) and the shell growth rate are presented to investigate the non-uniform characteristic of mould heat transfer and lubrication state.Based on the measured temperature data and OpenMP, an inverse problem model combining the parallel technology is developed, which is assigned to4CPU for parallel computing after domain decomposition of mould and strand. The results show that there is good agreement between the calculated temperature and the measured temperature, which could reflect the exact situation of heat transfer in the mould. And the computing time reduces three-quarters by using the parallel technology, basically meeting the velocity desire of on-line calculation. Now the software is applied in plants and it preliminarily realizes on-line visualization of the temperature, heat flux and strand solidification within mould, which could predict the generation of strand surface crack and optimize the process condition.The slag lubrication model is developed on the basis of temperature field to calculate the distribution of slag film and air-gap. The calculation results of peritectic steel in this paper show that the distributions of liquid slag film and strand surface temperature share similar characteristics. The liquid slag film at the upper part of the mould is thicker, the order of magnitude of which thickness is0.1mm. The liquid slag film disappears gradually when the strand surface temperature decreases. The thickness of solid slag film is about0.5mm, while it reaches1mm at the mould outlet. The status of slag film is affected obviously by the slag melting point and viscosity, and the liquid slag film thickness decreases when the casting speed increased. Furthermore, this paper proposes another method to analyze the air-gap between mould and strand.Non-uniformity and shell growth rate presenting in this paper are all defined to study the non-uniform behaviors in the mould. It shows that the non-uniformity of shell thickness near meniscus fluctuates severely, and the shell growth rate changes abruptly and reaches the maximum in the region of0-200mm below meniscus. The non-uniformity of mould temperature, heat flux, shell thickness and the liquid slag film increases with casting speed, as well as the fluctuation of shell growth rate.更多还原