本研究的目的是为了支持API推荐规程934-F（在启动和关闭期间为高温氢气服务中的重壁反应堆确定最低增压温度（MPT）的指南），旨在为确定避免回火脆化2¼Cr-1Mo钢在高压氢气环境中的焊缝金属和基板内部氢辅助开裂（IHAC）所需的最低加压温度奠定技术基础。 亚临界裂纹扩展开始的临界条件及其对溶解氢浓度、温度和钢纯度/回火脆性的依赖性，对于压力容器的安全运行尤为重要。第二个目标是改进用于IHAC服务建模的断裂力学适用性基础数据库。这两种分析均基于IHAC（KIH）的保守上升位移阈值应力强度因子。 本研究完成了五项任务，得出的结论足以在MPT上确定RP 934-F，从而保守地避免2¼Cr-1Mo钢中的IHAC。任务1——总结和澄清第二阶段JIP研究中使用的技术方法、假设、数据和建模结果，以定量确定IHAC阈值应力强度KIH的H浓度和温度依赖性，以及中等杂质2¼Cr的MPT浓度依赖性- 1Mo钢。任务2——基于对II期后IHAC数据的新分析，验证KIH和临界温度与H浓度的II期相关性。任务3:通过使用JIP第一阶段数据描述回火脆性和IHAC之间的相互作用，以预测现代钢纯度的影响，加强KIH与裂纹尖端H浓度的第二阶段分析，从而提高MPT。任务4——建立基于氢损伤机制的KIH和裂纹尖端应力场/微观结构之间的主相关性- 捕获H，以开发一个H浓度相似参数，用于厚壁反应器FFS和MPT的工程分析。任务5——通过考虑IHAC的最新理论和微观力学建模，验证基于经验的趋势和预测，即温度和钢纯度对阈值应力强度的影响。

The objective of this study, in support of API Recommended Practice 934-F (Guidance for Establishing a Minimum Pressurization Temperature (MPT) for Heavy Wall Reactors in High-temperature Hydrogen Service During Startups and Shutdowns), is to establish the technical basis for determining a minimum pressurization temperature necessary to avoid Internal Hydrogen-assisted Cracking (IHAC) of weld metal and base plate of temper-embrittled 2¼Cr-1Mo steel in high-pressure H2 service. The threshold condition for the onset of subcritical crack propagation, and its dependencies on dissolved hydrogen concentration, temperature, and steel purity/temper embrittlement, are targeted as particularly important to pressure vessel safe operations.A second objective is to improve the underlying database for fracture mechanics fitness-for-service modeling of IHAC. Both analyses are built on the conservative rising-displacement threshold stress intensity factor for IHAC (KIH). This investigation has accomplished five tasks, leading to conclusions that are sufficient to establish RP 934-F on MPT to conservatively avoid IHAC in 2¼Cr-1Mo steel.Task 1—Summarize and clarify the technical approach, assumptions, data, and modeling results used in Phase II JIP research to quantitatively establish the H concentration and temperature dependencies of the threshold stress intensity, KIH, for IHAC and the concentration dependence of MPT for moderate-impurity 2¼Cr-1Mo steel.Task 2—Validate the Phase II correlation of KIH and critical temperature vs H concentration, based on new analyses of post-Phase-II IHAC data.Task 3—Enhance the Phase II analysis of KIH vs crack tip H concentration, and thus MPT, by describing the interaction between temper embrittlement and IHAC using JIP Phase I data so as to predict the influence of modern steel purity.Task 4—Build on the hydrogen-damage-mechanism-based master correlation between KIH and crack tip stress field/microstructure-trapped H to develop an H concentration similitude parameter that is useful in engineering analysis of thick-wall reactor FFS and MPT.Task 5—Validate the empirically based trends and predictions of the effects of temperature and steel purity on the threshold stress intensity through consideration of state-of-the-art theory and micromechanical modeling of IHAC.