Which is more commonly used, 3Cr1Mo or 2 1/4Cr1Mo steel?

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In industrial applications, 2 1/4Cr-1Mo steel (i.e., 2.25Cr-1Mo steel) is widely used in the petroleum refining sector, such as in hydrogen desulfurization processes and in the reactors and thick-walled pressure vessels of hydrocracking units, due to its mature manufacturing processes, excellent overall performance, and low cost. It is suitable for moderately harsh operating conditions with temperatures of around 400–450°C and pressures of 8–18 MPa, and it is one of the most widely used chromium-molybdenum heat-resistant steels globally. In contrast, although 3Cr-1Mo steel exhibits better resistance to hydrogen erosion and creep strength at higher temperatures (up to 510°C) and under higher hydrogen pressures, making it suitable for extreme operating conditions such as coal liquefaction and heavy oil hydrogenation, its application range is relatively limited. It is mainly used in specific high-end devices where higher material properties are required, and its prevalence is lower than that of 2 1/4Cr-1Mo steel. Furthermore, 2 1/4Cr-1Mo steel possesses good weldability and hardenability in the manufacture of large forgings, enabling the production of forgings up to 300 mm thick, which further enhances its engineering versatility. Therefore, overall, 2 1/4Cr-1Mo steel is more widely and commonly used in practical industry.