基于长水口吹氩微气泡形成和湍流破碎的应用基础研究

The project aims to propose a novel approach for producing argon micro-bubbles in liquid steel, considering the current research, existing problems and future development of the high efficiency and low cost clean steel production technique. The high speed shearing flow in ladle shroud could inhibit interfacial effect during bubble formation. The initial bubble could be further refined owing to the bubble break-up by turbulent flow, so as to remove the small inclusions in liquid steel, as well as remain a stabilized slag-metal interface. The project simulates the non-wetting interface between liquid steel and refractory nozzles at room temperature, through introducing the surface treatment method in metallurgical research. The impacting mechanism of interfacial wettability on bubble nucleation and growth in shearing flow can be clarified through physical experiments coupled with numerical simulations. The mechanism of non-fully bubble break-up by actual turbulence flow can be revealed, as well. On the basis of above works, the project will establish a mathematical model to characterize the process of bubble formation and bubble break-up in turbulent liquid steel, furthermore, optimize the argon blowing parameters to meet the requirement of “ inclusion removal and slag eye inhibition”. Some new scientific issues are involved in this project, which could enrich the theory system of bubble dynamic. The project result can provide technical guidance for optimizing the argon blowing schemes in tundishes, and hopefully realize the deep cleaning of liquid steel with low cast. Hence, the project achievement will be valuable not only in theory, but also in industrial applications.

本项目结合“高效低成本洁净钢冶炼”这一钢铁行业关键技术的研究现状、存在的问题及未来的发展趋势，提出适用于实际钢液环境的中间包微气泡吹氩新构思。拟通过钢包长水口内高速流体的剪切作用抑制气泡生成过程的界面效应，利用湍流的破碎作用进一步细化气泡，从而在有效去除钢中小颗粒夹杂物的同时维持渣层的稳定。项目将化工领域常用的表面处理技术引入冶金研究中，在冷态条件下模拟耐火材料气孔与钢液之间的非润湿界面，通过物理实验结合数值模拟，阐明剪切流中界面润湿性对气泡形核、长大过程的影响机理，揭示实际湍流条件下气泡的非完全破碎机制，进而构建表征湍流钢液中气泡生成和破碎过程的数学模型，并基于“去夹杂，控渣眼”的思想对吹氩参数进行多目标优化。项目研究涉及诸多新的科学问题，将丰富气泡动力学的理论体系，研究成果可为优化中间包吹氩工艺条件提供相关技术指导，有望在较低成本条件下实现钢液的深度净化，具有理论与应用的双重价值。

惰性微气泡能够通过表面吸附和尾流夹带作用去除钢中的小颗粒夹杂物，是净化钢液的有效手段，但现有的中间包吹氩方式受制于钢液与喷嘴间的界面效应，难以在实际钢液环境中实现微气泡吹氩。本项目结合“高效低成本洁净钢冶炼”这一钢铁行业关键技术的研究现状及发展趋势，提出适用于实际钢液环境的中间包微气泡吹氩新构想。项目通过数值模拟与物理实验相结合的手段，系统阐明了非润湿条件下剪切流中气泡的形成机理，揭示了实际湍流中气泡的非完全破碎机制，明确了湍流耗散率的大小、衰减梯度和湍流破碎时间对气泡破碎程度的影响，最终建立了描述熔池内气泡终点尺寸的数学模型。再此基础上，通过优化的APSIII微粒子检测系统，探明了微气泡吹氩中间包内夹杂物的去除情况，耦合VOF和DPM模型，揭示了微气泡吹氩条件下中间包内渣-金界面的运动行为，明确了渣眼形成的临界条件。研究结果表明，钢包长水口吹氩，能够通过长水口内钢液的剪切作用和湍流破碎作用，在实际钢液环境中生成大量平均尺寸低至1.54mm的弥散微气泡。采用新型冲击板代替湍流控制器，能够抑制气泡在熔池内的二次碰撞，扩大气泡的分布范围，提高气泡群对钢液的整体扫略效率，将夹杂物残留量降低40.43%。中间包渣眼的形成取决穿过渣层的临界气体通量，微气泡吹氩能够降低单个气泡对渣层的冲击作用并分散整体气泡群对渣层的冲击，从而有效抑制渣眼的形成，使钢液出口温降减小1.6K。项目研究成果丰富了冶金过程中气-液两相流动的理论体系，为高品质洁净钢的大规模生产奠定了理论基础。