15CrMoR is a medium-temperature hydrogen-resistant pressure vessel steel widely used in the petrochemical and power generation industries for reactors, boilers, and other high-temperature, high-pressure equipment. Its designation indicates a carbon content of approximately 0.15%, with chromium (Cr) and molybdenum (Mo) as primary alloying elements, and "R" signifying its application for pressure vessels. The typical chemical composition includes 0.12–0.18% C, 0.80–1.20% Cr, and 0.45–0.60% Mo, with low phosphorus and sulfur content to enhance performance.
In high-temperature hydrogen service, 15CrMoR demonstrates several key capabilities. The material maintains high creep rupture strength at temperatures up to 550°C. It exhibits excellent resistance to hydrogen corrosion and hydrogen embrittlement, attributed to the stabilizing effect of chromium and molybdenum carbides. The steel is typically supplied in the normalized and tempered condition (930°C normalizing + ≥650°C tempering), which refines the grain structure and improves toughness.
However, 15CrMoR is not without limitations in hydrogen service. The material has a significant hardenability tendency due to its alloy content and relatively high carbon equivalent, making it susceptible to delayed cracking. Hydrogen embrittlement remains a critical concern, particularly in welded joints where hydrogen atoms can accumulate in the weld metal and heat-affected zone under high-temperature, high-pressure hydrogen environments, potentially leading to hydrogen-induced cracking. Case studies have reported cracking failures in 15CrMoR desulfurization tanks after extended service in hydrogen-rich environments at operating temperatures around 310°C and hydrogen concentrations of approximately 98.9%. To mitigate these risks, proper welding procedures with preheating (≥120°C), interpass temperature control (120–250°C), and post-weld heat treatment (620–680°C) are essential.
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