A387 Grade 11 Class 2 alloy steel (ASTM standard), equivalent to 13CrMo4-5 (EN standard) and 12Cr1MoV (GB standard), is a chromium-molybdenum alloy steel specifically engineered for high-temperature and pressure service. It provides excellent creep strength, oxidation resistance, and thermal stability, making it ideal for use in boilers, pressure vessels, and heat exchangers.