Abstract: The invention provides a ferritic heat-resistant steel whose creep rupture ductility in a long-term region is improved without detrimental to creep strengths. The ferritic heat-resistant steel has a chemical composition comprising, in % by mass, C: 0.03 to 0.15, Si: 0 to 0.8, Mn: 0.1 to 0.8, Cr: 8.0 to 11.5, Mo: 0.2 to 1.5, (W: 0.4 to 3.0), V: 0.1 to 0.4, Nb: 0.02 to 0.12 N: 0.02 to 0.10 with the balance of iron and inevitable impurities. This steel has a tempered martensite microstructure, and has an improved creep rupture ductility even when there is a load within the elastic limits at temperatures at which the ferritic heat-resistant steel is used, because internal strain or internal stress induced by martensitic transformation is relaxed or released by an intermediate tempering heat treatment in a two-phase state temperature in which a portion of an austenitic phase undergoes martensitic transformation.

Abstract: The invention provides a ferritic heat-resistant steel whose creep rupture ductility in a long-term region is improved without detrimental to creep strengths. The ferritic heat-resistant steel has a chemical composition comprising, in % by mass, C: 0.03 to 0.15, Si: 0 to 0.8, Mn: 0.1 to 0.8, Cr: 8.0 to 11.5, Mo: 0.2 to 1.5, (W: 0.4 to 3.0), V: 0.1 to 0.4, Nb: 0.02 to 0.12 N: 0.02 to 0.10 with the balance of iron and inevitable impurities. This steel has a tempered martensite microstructure, and has an improved creep rupture ductility even when there is a load within the elastic limits at temperatures at which the ferritic heat-resistant steel is used, because internal strain or internal stress induced by martensitic transformation is relaxed or released by an intermediate tempering heat treatment in a two-phase state temperature in which a portion of an austenitic phase undergoes martensitic transformation.

Abstract: A heat-resistant component for a chemical processing apparatus is formed from a ferritic Cr-steel that contains Cr in an amount of from 13% by weight to 30% by mass. The ferritic Cr-steel has a creep rate of 1×10?51h or less at 700° C. under stress of 100 MPa, and an oxidation weight gain of 10 mg/cm2 or less after being maintained in a 650° C. water vapor for 1,000 h. The heat-resistant component for a chemical processing apparatus is produced by hot working the ferritic Cr-steel in a temperature range of 850 to 1,200° C., forming the ferritic Cr-steel into a component shape, subjecting the steel to an annealing treatment in a temperature range of 1,000 to 1,250° C., and cooling the steel to 400° C. or less at a cooling rate of 100° C./min or higher.

Abstract: A ferritic Cr-steel for a heat-resistant precision component contains Cr in an amount of from 13% by mass to 30% by mass, and has a thermal expansion coefficient of 15×10?6 or less in a temperature range of from room temperature to 800° C., and a minimum creep rate of 1×10?4/h or less at 700° C. under stress of 100 MPa. The ferritic Cr-steel for a heat-resistant precision component is produced by hot working a ferritic Cr-steel in a temperature range of 850 to 1,200° C., forming the ferritic Cr-steel into a predetermined shape, subjecting the steel to an annealing treatment in a temperature range of 1,000 to 1,250° C., and cooling the steel to 400° C. or less at a cooling rate of 100° C./min or higher. The production of the ferritic Cr-steel realizes a heat-resistant precision component, such as the rotor, disc, and blade of a turbine, that can withstand use under high temperatures above 600° C.

Abstract: The invention provides a ferritic heat-resistant steel having excellent high-temperature oxidation resistance, especially excellent steam oxidation-resistant characteristics. In high-Cr ferritic heat-resistant steel, ultra-fine oxide particles having a size of not larger than 1 ?m are formed just below the oxide films and formed on the steel base, whereby the adhesiveness between the films and the base is enhanced. The ferritic heat-resistant steel contains Cr in an amount of from 8.0 to 13.0% by weight, and at least one of Rh and Ir in a total amount of from 0.3 to 5.0% by weight.

Abstract: The invention provides a ferritic heat-resistant steel having excellent high-temperature oxidation resistance, especially excellent steam oxidation-resistant characteristics. In high-Cr ferritic heat-resistant steel, ultra-fine oxide particles having a size of not larger than 1 &mgr;m are formed just below the oxide films and formed on the steel base, whereby the adhesiveness between the films and the base is enhanced. The ferritic heat-resistant steel contains Cr in an amount of from 8.0 to 13.0% by weight, and at least one of Rh and Ir in a total amount of from 0.3 to 5.0% by weight.

Abstract: The invention provides a ferritic heat-resistant steel having excellent high-temperature oxidation resistance, especially excellent steam oxidation-resistant characteristics. In high-Cr ferritic heat-resistant steel, ultra-fine oxide particles having a size of not larger than 1 &mgr;m are formed just below the oxide films and formed on the steel base, whereby the adhesiveness between the films and the base is enhanced. The ferritic heat-resistant steel contains Cr in an amount of from 8.0 to 13.0% by weight, and at least one of Rh and Ir in a total amount of from 0.3 to 5.0% by weight.

Abstract: The invention provides a ferritic heat-resistant steel having excellent high-temperature oxidation resistance, especially excellent steam oxidation-resistant characteristics. In high-Cr ferritic heat-resistant steel, ultra-fine oxide particles having a size of not larger than 1 &mgr;m are formed just below the oxide films and formed on the steel base, whereby the adhesiveness between the films and the base is enhanced. The ferritic heat-resistant steel contains Cr in an amount of from 8.0 to 13.0% by weight, and at least one of Rh and Ir in a total amount of from 0.3 to 5.0% by weight.