大型多层复合钢锭中多层界面行为及其调控机制的相关基础研究

Heavy casting and forging is one of the key components for nuclear power, petrochemical, ship and other major equipment manufacturing, high-quality steel ingot preparation used for large castings and forgings has become an important bottleneck restricting for the development of our country’s industry. Due to the segregation of elements, it is difficult to prepare high-quality steel ingots by conventional methods. This paper presents a new idea for the preparation of heavy ingots by electroslag multi-layer cladding method, which provides a new way for the preparation of high quality heavy ingots. This paper will focus on the influence of power supply parameters, melting rate, slag and withdrawing speed on the surface quality, internal quality and composite interface quality of multi-layer cladding ingot and its control mechanism. The impact of research work, especially the subsequent compound on the previous composite interface, will be one of the key research contents of this project. Based on the research of hot workability and heat treatment system of multi-layer cladding ingot, the evolution and the mechanism of thermal processing and heat treatment on the interface quality of multi-layer cladding ingot will be discussed. In addition, the mathematic model of composite process will be established, and the influence of stress field and heat affected zone on the quality of multilayer cladding interface will be analyzed combined with experimental study in this paper. The successful implementation of this project will promote the development of China's large-scale high-quality steel ingot manufacturing level, has important theoretical and practical significance.

大型铸锻件是核电、石化、船舶等重大装备制造业的关键部件之一，大型铸锻件用优质大钢锭的制备已经成为制约我国相关行业发展的重要瓶颈。由于元素偏析，传统方法很难制备出高质量的大型钢锭。本课题提出电渣多层复合法制备高品质大型多层复合钢锭的新思路，课题将围绕多次复合过程供电参数、熔速、渣系、抽锭速度等因素对多层复合钢锭表面质量、内部质量、复合界面质量的影响规律及其调控机制、后续复合过程中热影响区和热应力对已形成复合界面的影响等方面开展研究工作。通过热加工性能和热处理制度的研究，揭示热加工和热处理对多层复合钢锭结合界面质量的演变规律及其调控机制。建立复合过程相关数学模型，结合实验研究，分析多层复合界面的应力及热影响区对多层复合界面质量的影响规律，建立电渣多层复合制备多层复合钢锭的相关理论体系。课题的实施将为我国大型优质钢锭的制造提供重要理论基础，具有重要的理论和现实意义。

由于元素偏析，传统工艺技术很难制备出高质量的大型钢锭，电渣复合法是一种“以小制大”制备大型铸锭的创新方法。本项目紧密围绕渣系优化设计、装备、供电模式、铸锭质量及复合铸锭热处理制度等关键工艺技术开展研究。.建立了电渣复合专用渣系设计方法，开展了电渣复合渣系熔化温度、黏度、表面张力等多种物性参数研究，重点围绕电渣复合过程渣系吸收溶解典型非金属夹杂物的热力学及动力学行为开展创新研究，揭示了渣系吸收溶解夹杂物的影响因素及相关机理，为电渣复合过程提供基础保障。基于导电结晶器电渣复合制备复合铸锭的工艺理论、核心装备为研究内容，深入研究了复合铸锭界面宏观形成过程、供电参数、复合铸锭制备、界面结合质量及结合机理、导电结晶器结构设计理论、磁场调控复合铸锭结合界面质量技术，阐明了采用复合装备外磁场调控、多电流出口布置以及结晶器内电流分布对复合铸锭质量的影响规律，为制备出周向和轴向结合界面熔合线均一及结合质量稳定的复合铸锭奠定了坚实的理论基础。.开展了一次复合和二次复合铸锭制备实验研究，掌握了影响复合界面质量的关键因素及调控措施，揭示了电渣复合过程中复合界面结合机理为冶金结合，复合界面无缩孔、夹渣及大颗粒非金属夹杂物、力学性能良好，复合界面两侧元素存在浓度差时，元素在复合界面处呈梯度过渡，过渡层宽度为数百微米尺度。复合时，供电功率分配应采用“先高后低”递减方式控制，内层金属最佳熔化深度为5±3 mm。复合铸锭整体及差温处理对复合铸锭热处理制度的研究表明，通过合理的热处理制度可以使铸锭从外层到内层按照金属成分特点实现强度和韧性的梯度变化。差温热处理更适合于双金属复合铸锭的热处理，而整体热处理适合于单一材质的多层复合铸锭的热处理。.综上所述，本项目关于电渣复合装备、工艺及复合机理的相关研究成果，为该技术工业化奠定了良好的基础。