Modified 1% crmov rotor steel

Abstract

A modified 1% CrMoV steel of particular use in steam and gas turbine rotors contains from about 0.20 percent to about 0.35 percent carbon, less than about 0.1 percent manganese, from about 1.5 percent to about 6.5 percent nickel, from about 0.8 percent to about 2.0 percent chromium, from about 0.9 percent to about 2.0 percent molybdenum, from about 0.1 percent to about 0.4 percent vanadium, from zero to about 0.07 percent columbium, less than about 0.12 percent silicon, less than about 0.006 percent phosphorus, less than about 0.002 percent sulfur, less than about 0.005 percent antimony, less than about 0.010 percent arsenic, less than about 0.010 percent tin, less than about 0.10 percent copper, less than about 0.010 percent aluminum, balance iron totalling 100 percent, with all percentages by weight. Selected compositions of this steel can be processed to have a 50% fracture appearance transition temperature of less than ambient temperature, and do not exhibit temper embrittlement after extended periods of elevated temperature exposure. The hardenability and creep rupture properties of the modified steel are better than, or equivalent to, those of the standard 1% CrMoV steels, which are brittle at ambient temperatures and subject to temper embrittlement.