摘要
核反应堆压力容器(RPV)传统采用独立锻件通过焊缝连接的结构形式,由于焊缝为铸态金属组织,属失效分析中的薄弱环节,因此采用集成化锻造结构,确保承压焊缝质量,是提升RPV安全可靠性的重要方法.但是,集成化后的锻造结构存在几何异形、结构复杂、壁厚差异大等问题,其材料组织与性能调控难度大幅增加.针对上述问题,以核电RPV接管"set-on"结构形式为对象,基于结构导热微分及等温转变叠加理论,建立了锻造结构温度-组织-应力的多物理场耦合模型,以调质热处理的奥氏体化及淬火冷却两个阶段为对象,结合淬火冷却介质流-固耦合分析方法,获得锻造结构不同位置处材料组织与性能变化的定量规律,并明确了其关键影响因素.
Abstract
Recently,reactor pressure vessel ( RPV) is commonly assembled by single forgings with welding connections. As kind of cast structure,welding is the vulnerable spot for failure analysis. Hence,integrated forging for high welding quality can be adopted in order to promote the safety and reliability of RPV. But,problems like heteromorphic structure,complicated geometries and great wall thickness difference of integrated forging would cause the difficulties in metallographic phase and property modulation. For the"set-on"nozzle structure of NPP RPV,a temperature-phase-stress field coupling analysis model has been established on the basis of structure thermal conductivity calculus and austempering transformation theory. Combing with fluid-solid coupling analysis of quenching cooling medium,the quantitative discipline of phase change and property modulation has been obtained for both austenitizing and quenching process,and the key influence factors have been specified.
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