Ferritic heat-resistant steel and method for production thereof
View Patent ↗A ferritic heat-resistant steel, which exhibits excellent creep characteristics even at a high temperature exceeding 600° C., comprises, on the basis of percent by weight, 1.0 to 13% of chromium, 0.1 to 8.0% of cobalt, 0.01 to 0.20% of nitrogen, 3.0% or less of nickel, 0.01 to 0.50% of one or more of elements selected from a group consisting of vanadium, niobium, tantalum, titanium, hafnium, and zirconium that are MX type precipitate forming elements, and 0.01% or less of carbon and a balance being substantially iron and inevitable impurities, wherein the MX type precipitates precipitate on grain boundaries and in entire grains and the grain boundary existing ratio of an M 23 C 6 type precipitate precipitating on the grain boundaries is 50% or less.
1. Ferritic heat-resistant steel comprising, on the basis of percent by weight,
1.0 to 13% of chromium,
0.1 to 8.0% of cobalt,
0.01 to 0.088% of nitrogen,
3.0% or less of nickel,
0.01 to 0.060% of niobium and
0.01 to 0.50% of one or more elements selected from a group consisting of vanadium, tantalum, titanium, hafnium, and zirconium that are MX precipitate forming elements,
0.0 1% or less of carbon
and a balance being substantially iron and inevitable impurities,
wherein MX precipitates precipitate on grain boundaries and in entire grains, and the grain boundary existing ratio of an M 23 C 6 precipitate precipitating on the grain boundaries is 50% or less.
2. The ferritic heat-resistant steel according to claim 1 , further comprising 0.001 to 0.030% of boron on the basis of percent by weight.
3. The ferritic heat-resistant steel according to claim 1 , further comprising one or both of 0.1 to 3.0% of molybdenum or 0.1 to 4.0% of tungsten on the basis of the percent by weight.
4. A method of manufacturing ferritic heat-resistant steel according to claim 1 , comprising the step of molding a material after it has been melted and then subjecting the molded material to a solution treatment at a temperature of 1000° C. to 1300° C.
5. The method of manufacturing ferritic heat-resistant steel according to claim 4 , wherein a temper treatment is executed at a temperature of 500° C. to 850° C. after the completion of solution treatment.
6. The ferritic heat-resistant steel according to claim 2 , further comprising one or both of 0.1 to 3.0% of molybdenum or 0.1 to 4.0% of tungsten on the basis of the percent by weight.
7. A method of manufacturing ferritic heat-resistant steel according to claim 2 , comprising the step of molding a material after it has been melted and then subjecting the molded material to a solution treatment at a temperature of 1000° C. to 1300° C.
8. A method of manufacturing ferritic heat-resistant steel according to claim 3 , comprising the step of molding a material after it has been melted and then subjecting the molded material to a solution treatment at a temperature of 1000° C. to 1300° C.
9. A method of manufacturing ferritic heat-resistant steel according to claim 6 , comprising the step of molding a material after it has been melted and then subjecting the molded material to a solution treatment at a temperature of 1000° C. to 1300° C.