SA508Gr.4N钢大型铸锭层状铸造及其界面熔合与成分协调原理

SA508Gr.4N钢(简称5084钢)被认为是下一代核反应堆压力容器首选的结构材料，然而其高合金化使得大型铸锭制备中易产生严重的非均质性问题而影响最终产品的性能，并严重制约后续热加工方法和工艺窗口的选择。申请人团队前期基于增材制造理念提出了将大铸锭“化整为零”分步浇注、逐层凝固、按需/定位/定时补给的层状铸造（简称LC）方法，有效降低了铸锭的宏观偏析等缺陷，有望解决其大型铸锭的非均质性问题。.本项目以5084钢为研究对象，拟对LC面临的界面熔合及溶质迁移问题开展深入研究：构建铸造成锭过程集浇注、凝固全流程耦合的枝晶生长/熔化及多缺陷耦合预测模型；探究LC不同金属液浇入状态下的枝晶生长-重熔-再生长机制及溶质的混合与迁移原理；发展浇注控制、单元离散与溶质控制模型，构建熔炼、浇注、凝固全过程数字化平台。从而发展和完善制备5084钢高均质化大型铸锭LC新技术理论基础，并促进其产业化应用。

SA508 Gr.4N steel has been considered as the primary choice for the new generation of nuclear reactor pressure vessel steel. However, serious inhomogeneity of SA508 Gr.4N heavy steel ingots, which results from the ingot solidification process due to its big volume and high alloying, will not only affect their subsequent processing but also the performance of the final products..Based on the concept of additive manufacturing, the applicant team proposed a new pouring method, called layered casting, which can effectively reduce the casting defects such as macrosegregation of the ingots, and is expected to solve the problem of heterogeneity of large ingots. For this method, the alloy melt is poured into the mould step by step, so that the melt can be solidified layer by layer. The alloy component will also be adjusted based on the instantaneous solute content of the residual unsolidified melt. .Current research will take the SA508 Gr.4N steel as the research object and carry out in-depth research on the interfacial fusion and composition coordination problems faced by layered casting. Main research contents are 1) to construct the dendrite growth & remelting model and the multi-defects coupled model for the whole process of pouring and solidification in the process of layered casting; 2) to investigate the mechanism of dendrite growth-remelting-regrowth and the principle of mixing and migration of solutes under different liquid metal pouring states of layered casting; 3) to develop pouring control, unit discrete and solute control models, and build a digital platform for the whole process of smelting, pouring and solidification. By completing the above researches, the layered casting theory and key technologies for preparing SA508 Gr.4N steel high-homogenization large ingots will be developed and improved.