Cast austenitic stainless steels (CASS) are materials used to fabricate many important safety-related components in the primary circuits of light water reactors since the early 1970’s. The primary circuit, which transports heated water by nuclear reaction to steam generators, is subjected to in-service temperatures between 285 °C and 325 °C. Under these conditions, CASS undergo thermal aging which may significantly affect their mechanical properties and more especially their fracture toughness. From a metallurgical point of view, the changes in mechanical properties are attributable to several solid-state phase transformation processes including the spinodal decomposition of the ferritic phase and the precipitation of G phase. The kinetics of these phase transformations depends primarily on the time and temperature of aging, secondly on the chemical composition of the heat (chromium, molybdenum, silicon and nickel contents) and thirdly on the heat treatments performed during component manufacturing. The prediction of the long-term behavior of CASS is an important industrial issue for nuclear power plant operators. In the early 1980’s, Electricité De France (EDF) engaged an unparalleled laboratory aging program that is still in progress. Presently, some materials have been aged for more than 200,000 h at low temperatures. The results of this program allow the development of prediction models for Charpy-impact energies, $J-R$ curves and thermoelectric power values much more precise than those proposed so far, based on aging at 400 °C and rarely exceeding 30,000 h. These prediction models are described in this paper.

自1970年代初以来，铸造奥氏体不锈钢（CASS）是用于制造轻水反应堆一次回路中许多重要的与安全相关的组件的材料。通过核反应将热水输送到蒸汽发生器的主回路处于285°C至325°C的使用温度下。在这些条件下，CASS经历了热老化，这可能会严重影响其机械性能，尤其是其断裂韧性。从冶金学的角度来看，机械性能的变化可归因于几种固态相变过程，包括铁素体相的旋节线分解和G相的析出。这些相变的动力学主要取决于老化的时间和温度，其次是热量的化学成分（铬，钼，硅和镍的含量），其次是在零件制造过程中进行的热处理。对CASS长期行为的预测是核电厂运营商的重要工业问题。在1980年代初期，法国电力公司（EDF）开展了一项无与伦比的实验室老化计划，该计划仍在进行中。目前，某些材料在低温下已老化200,000小时以上。该程序的结果允许开发夏比冲击能量的预测模型，对CASS长期行为的预测是核电厂运营商的重要工业问题。在1980年代初期，法国电力公司（EDF）开展了一项无与伦比的实验室老化计划，该计划仍在进行中。目前，某些材料在低温下已老化200,000小时以上。该程序的结果允许开发夏比冲击能量的预测模型，对CASS长期行为的预测是核电厂运营商的重要工业问题。在1980年代初期，法国电力公司（EDF）开展了一项无与伦比的实验室老化计划，该计划仍在进行中。目前，某些材料在低温下已老化200,000小时以上。该程序的结果允许开发夏比冲击能量的预测模型，$Ĵ-\mathrm{[R}$基于400°C的老化和极少超过30,000 h的曲线，曲线和热电功率值比迄今提出的精确得多。这些预测模型在本文中进行了描述。