A heat resistant martensitic stainless steel having an improved creep rupture strength is described. This steel consists of, in weight percent, 0.05% to 0.12% carbon, not more than 0.5% silicon, not more than 1.5% manganese, not more than 1.5% nickel, 9.0 to 13.0% chromium, 0.5 to 2.0% molybdenum, 0.05 to 0.50% vanadium, not more than 0. 15% nitrogen, and, if desired, at least one of 0.02 to 0.50% columbium, 0. 02 to 0.5% tantalum, 0.5 to 2.0% tungsten, and 0.0003 to 0.0100% boron, with the balance being iron and incidental or inevitable impurities, and wherein the weight ratio of carbon to nitrogen (C/N) is not more than 3:1.
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