中锰钢薄板坯连铸结晶器区钢液凝固传热机理

For achieving the industrial application of thin slab continuous casting and rolling process of medium manganese steels, the control of molten steel solidification and heat transfer in mold zone is the key to improve the casting process and surface quality of thin slab for medium manganese steels. Therefore, the present work focuses on the mechanism of solidification and heat transfer in thin slab casting mold for medium manganese steels based on the solidification characteristics of medium manganese steel and the practice of thin slab casting. The mutual influences of shell growth and steel flow under dynamic high cooling rate will be investigated to clarify the characteristics of metal flow, solidification, and heat transfer in thin slab continuous casting mold. The flow pattern and dynamic heat transfer of non-reactive slag during mold oscillation will be studied to obtain reasonable slag properties and mold oscillation parameters for uniform lubrication and heat transfer conditions of thin slab casting mold. Based on the analysis of thin slab solidification shrinkage and mold deformation at high temperature, the method for mold internal shape design to ensure efficient heat transfer and uniform solidification will be established. Finally, the mechanism of high efficiency solidification and heat transfer in thin slab casting mold for medium manganese steels will be illustrated, which will lay a theoretical and technical foundation for the application of thin casting process of medium manganese steels.

针对促进实现中锰钢薄板坯连铸连轧工艺工业应用的目标，解决中锰钢薄板坯连铸工艺顺行与铸坯表面质量控制难题，结晶器区钢液的凝固传热控制是关键。为此本项目立足于中锰钢凝固特性和薄板坯连铸生产实际，开展中锰钢薄板坯连铸结晶器区钢液凝固传热机理研究，揭示动态高冷速条件下中锰钢坯壳凝固与钢液流动传热的相互影响机制，阐明中锰钢薄板坯连铸结晶器内钢液流动与凝固传热特征；明确结晶器振动作用下非反应性保护渣流动形态及动态传热规律，获得确保中锰钢薄板坯连铸结晶器内渣道均匀润滑与传热行为的保护渣物性和结晶器振动工艺参数；探明中锰钢薄板坯凝固热/力学行为及结晶器高温变形规律，获得高效传热和铸坯均匀生长的中锰钢薄板坯结晶器内腔形状的确定方法，最终确立中锰钢薄板坯连铸结晶器区钢液高效凝固传热机理，为中锰钢薄板坯连铸工艺的应用奠定理论和技术基础。

针对促进实现中锰钢薄板坯连铸连轧工艺工业应用的目标，解决中锰钢薄板坯连铸工艺顺行与铸坯表面质量控制难题，结晶器区钢液的凝固传热控制是关键。本项目立足于中锰钢凝固特性和薄板坯连铸生产实际，开展了中锰钢薄板坯连铸结晶器区钢液凝固传热机理研究，揭示了薄板坯结晶器内中锰钢坯壳凝固与钢液流动传热的相互影响机制，阐明了中锰钢薄板坯连铸结晶器内钢液流动与界面波动特征；描述了动态高冷速下保护渣在结晶器内的熔化与流动行为，以及结晶器内钢渣反应特征及渣层内成分分布规律，分析了保护渣物性参数对液渣膜厚度、保护渣流动速度和液位波动的影响规律；对比研究了锰含量、过热度及拉速等对中锰钢薄板坯结晶器区钢液凝固传热行为特征的影响。本项目研究主要包括以下几部分重要结果：(1) 薄板坯结晶器内钢液呈现具有随机性的非对称流动行为特征，三维模型流场较二维模型冲击深度更浅，且自由液面流速和波动幅度更大；(2) 凝固坯壳会对结晶器内钢液流动造成挤压，导致回流呈扁平状，在拉坯作用下使自由液面角部附近形成一个小回流；(3) 结晶器四周钢液和保护渣的凝固导致钢渣界面反应速率较慢，液面波动增加了反应速率了界面更新率，在波峰处的反应速率更快；(4) 在熔渣池的横截面上，MnO浓度由水口向结晶器窄面逐渐降低，熔渣池上层的成分分布更加均匀，固态渣膜为不同反应阶段含不同MnO含量的液渣凝固而成；(5) 相较于低碳钢，中锰钢在窄面中心处坯壳温度更高，而在结晶器出口处坯壳温度更低，且坯壳横向温差大于20℃，这种温度不均匀性是造成铸坯表面纵裂纹的主要原因。项目研究结果为进一步认识中锰钢薄板坯连铸结晶器区钢液高效凝固传热行为提供了理论依据和技术基础。