基于抽锭电渣重熔过程渣壳动态形成和热/力耦合行为的高氮护环空心锭表面质量控制方法研究

The purpose of this project is to explore a new electroslag remelting (ESR) method for production of high quality and near net shape high nitrogen steel hollow ingot for retaining ring on the basis of traditional ESR theory and technology. The choosing principle of slag for ESR retaining ring steel hollow ingot will be established through the investigation of slag. Research of this project will be carry out by using the method of combining mathematical model with experimental research. The mathematical model will be developed to investigate the dynamic formation of slag shell during the new technology process. The dynamic formation process and mechanism of slag shell will be clarified, to master the effective method for controlling good surface quality through the process control of solidification condition to form suitable thickness and uniform slag shell. The quantitative relation of process conditions, dynamic formation of slag shell and the hollow ingot surface quality will be established. The mathematical model will be developed to investigate thermal/mechanical coupling behavior during the new technology process. The solidification shrinkage behavior and air gap formation process of hollow ingot will be clarified. The quantitative relation of process conditions, thermal/mechanical coupling behavior and friction behavior will be established. The influence and control mechanism of process parameters on the dynamic formation behavior of slag shell and thermal/mechanical coupling behavior will be revealed. All of the research results of this project can effectively guide the ESR hollow ingot surface quality control theory and technology foundation, which has the great significance on meeting the needs of high quality hollow ingot in national major projects in our country.

本项目旨在传统电渣重熔理论和技术基础上，探索一种制备高质量、近终型高氮护环空心锭的新方法。课题将开展重熔高氮护环钢空心锭渣系组元研究，确定抽锭式电渣重熔高氮护环钢用渣系组元选配原则。采用数学模型与实验研究相结合的方法，开展新工艺下渣壳动态形成行为，阐明渣壳动态形成过程和机理，探索通过工艺控制渣壳厚度适宜、分布均匀的凝固条件，形成良好表面质量的有效方法，建立协调工艺条件、渣壳动态形成行为与铸锭表面质量控制的量化关系；开展凝固过程热/力耦合行为模拟，阐明空心钢锭凝固收缩行为和气隙的形成过程，建立协调工艺条件、热/力耦合数学模型和摩擦行为的量化关系。揭示工艺参数对重熔过程渣壳动态形成行为和凝固热/力耦合行为影响规律及其调节控制机制。该项目研究成果为有效的指导电渣重熔高氮护环钢空心锭表面质量控制方法奠定理论和技术基础，对我国生产高品质空心锭，满足国家重大项目需要具有重大意义。

电渣重熔空心锭技术是工业生产空心钢锭的有效途径，一种制备高质量、近终型高氮护环空心锭的新方法。.课题开展了重熔高氮护环钢空心锭渣系组元研究，确定抽锭式电渣重熔高氮护环钢用渣系组元选配原则。研究表明最适合的渣系组元含量为w(CaF2)=50%~60%，w(Al2O3)=20%~25%，w(CaO)=15%~20%，w(MgO)=5%，w(SiO2)=3%~4%，在此范围内可以有效抑制钢中的增Al，提高钢锭质量。.构建了电渣重熔空心钢锭渣皮动态行为模型，讨论了电极布置和电流对多物理场与渣皮厚度的影响规律。模拟结果表明：当改变电极布置时，渣池与熔池区域中的最高温度随着电极数目的减小而升高，渣池区域中的湍流速率随着电极数目的减小而变大，金属熔池的深度与两相区宽度随着电极数目的减少变大，渣皮厚度会随着电极数目的减少而变厚。当改变电流大小时，渣池与熔池区域中的最高温度随着电流的增大而升高，渣池区域中的湍流速率随着电流的增大而变大，金属熔池的深度与两相区宽度随着电流的增大而变大，渣皮厚度会随着电流的增大而变薄。.构建了电渣重熔空心钢锭热力耦合行为模型，讨论了内结晶器锥角、电流和钢种对重熔体系多物理场的影响。计算结果表明：在相同电流下，随着内结晶器锥角增加，金属熔池逐渐加深，气隙宽度增加，换热系数减少；随着重熔电流的增加，金属熔池逐渐变深，气隙宽度增加，换热系数减少；P91钢金属熔池深度小于1Mn18Cr18N钢，气隙宽度更大，换热系数更小。电渣重熔1Mn18Cr18N空心钢锭的最佳工艺参数为：渣池深度为90 mm、采用八电极布置、内结晶器锥角1.5°、重熔电流为5000 A。.研究了电渣重熔空心钢锭工艺参数对工艺参数对渣壳动态形成和凝固过程气隙形成的影响规律，定量考察了电渣重熔高氮护环钢空心锭过程工艺参数与实测数据结果，为优化工艺参数提供了理论依据。.依托该项目，发表SCI论文7篇，专著1部，申请专利7项，科研奖励1项。该项目研究成果为有效地指导大型管坯电渣重熔生产奠定理论和技术基础，对我国生产高品质厚壁管，满足国家重大项目需要具有重大意义。