Heat resisting steel, gas turbine using the steel, and components thereof

Abstract

The invention is of a heat resisting martensitic steel comprising, by weight, 0.05 to 0.30% C, not more than 0.50% Si, not more than 0.60% Mn, 8.0 to 13.0% Cr, 0.5 to 3.0% Ni, 1.0 to 3.0% Mo, 0.1 to 1.5% W, 0.5 to 4% Co, 0.05 to 0.35% V, 0.02 to 0.30% in total of one or two elements selected from the group consisting of Nb and Ta, and 0.02 to 0.10% N, wherein a value of the square of a difference between the Ni amount and the Co amount, and the Ni amount are not more than values determined by a straight line drawn on a point A (1.0, 2.7%) and a point B (2.5, 1.0%) in the orthogonal coordinates shown in the attached drawing of FIG. 2 which represents a relationship between the above square value and the Ni amount, and an amount ratio of Mo/(Mo+0.5 W) is not less than 0.5. The heat resisting steel is suitably used in various components of a gas turbine.

1 . A heat resisting martensitic steel comprising, by weight, 0.05 to 0.30% C, not more than 0.50% Si, not more than 0.60% Mn, 8.0 to 13.0% Cr, 0.5 to 3.0% Ni, 1.0 to 3.0% Mo, 0.1 to 1.5% tungsten (W), 0.5 to 4% Co, 0.05 to 0.35% vanadium (V), 0.02 to 0.30% in total of one or two elements selected from the group consisting of Nb and Ta, and 0.02 to 0.10% nitrogen (N), wherein 
 a value of the square of a difference between the Ni amount and the Co amount, and the Ni amount are not more than values determined by a straight line drawn on a point A (1.0, 2.7%) and a point B (2.5, 1.0%) in the orthogonal coordinates shown in the attached drawing of  FIG. 2  which represents a relationship between the above square value and the Ni amount, and wherein    an amount ratio of Mo/(Mo+0.5 W) is not less than 0.5.    
     
     
         2 . A heat resisting steel according to  claim 1 , wherein the square value is not more than 1.8.  
     
     
         3 . A heat resisting martensitic steel according to  claim 1 , which further comprises, by weight, not more than 1.5% Re, and 0.001 to 0.015% boron (B).  
     
     
         4 . A heat resisting martensitic steel comprising, by weight, 0.05 to 0.30% C, not more than 0.50% Si, not more than 0.60% Mn, 8.0 to 13.0% Cr, 0.5 to 3.0% Ni, 1.0 to 3.0% Mo, 0.1 to 1.5% W, 0.5 to 4% Co, 0.05 to 0.35% V, 0.02 to 0.30% in total of one or two elements selected from the group consisting of Nb and Ta, and 0.02 to 0.10% nitrogen (N), wherein an amount ratio of W/Mo, and the Mn amount are not more than values determined by a straight line drawn on a point C (1.3, 0.15%) and a point D (2.5, 0.37%) in the orthogonal coordinates shown in the attached drawing of  FIG. 4  which represents a relationship between the amount ratio and the Mn amount.  
     
     
         5 . A heat resisting martensitic steel according to  claim 4 , wherein an amount ratio of Mo/Mo+0.5 W, and the Mn amount are not less than values determined by a straight line drawn on a point E (0.25, 0.4%) and a point F (0.7, 0.15%) in the orthogonal coordinates shown in the attached drawing of  FIG. 6  which represents a relationship between the amount ratio and the Mn amount.  
     
     
         6 . A heat resisting martensitic steel according to  claim 4 , which further comprises, by weight, at least one element of not more than 1.5% Re and 0.001 to 0.015% boron (B).  
     
     
         7 . A heat resisting martensitic steel according to  claim 5 , which further comprises, by weight, at least one of not more than 1.5% Re and 0.001 to 0.015% boron (B).  
     
     
         8 . A heat resisting martensitic steel according to  claim 1 , which further comprises, by weight, at least one of not more than 0.5% Cu, not more than 0.5% Ti, not more than 0.2% Al, not more than 0.1% Zr, not more than 0.1% Hf, not more than 0.01% Ca, not more than 0.01% Mg, not more than 0.01% yttrium (Y), and not more than 0.01% of a rare earth element.  
     
     
         9 . A heat resisting martensitic steel according to  claim 4 , which further comprises, by weight, at least one of not more than 0.5% Cu, not more than 10.5% Ti, not more than 0.2% Al, not more than 0.1% Zr, not more than 0.1% Hf, not more than 0.01% Ca, not more than 0.01% Mg, not more than 0.01% yttrium (Y), and not more than 0.01% of a rare earth element.  
     
     
         10 . A gas turbine comprising: 
 a turbine stub shaft;    a plurality of turbine discs connected to the turbine stub shaft by turbine stacking bolts via turbine spacers;    turbine blades each implanted in the respective disc to rotate by high-temperature combustion gas generated in a combustion device;    a distant piece connected to the turbine discs;    a plurality of compressor rotors connected to the distant piece;    compressor blades which are implanted to compressor discs constituting the respective compressor rotor, and which compress air; and    a compressor stub shaft connected to the compressor rotors, wherein    at least one of the turbine discs, the distant piece, the turbine spacers, the compressor disc at a last stage, and the turbine stacking bolts is made of a martensitic steel comprising, by weight, 0.05 to 0.30% C, not more than 0.50% Si, not more than 0.60% Mn, 8.0 to 13.0% Cr, 0.5 to 3.0% Ni, 1.0 to 3.0% Mo, 0.1 to 1.5% W, 0.5 to 4% Co, 0.05 to 0.35% vanadium (V), 0.02 to 0.30% in total of one or two elements selected from the group consisting of Nb and Ta, and 0.02 to 0.10% nitrogen (N), wherein    a value of the square of a difference between the Ni amount and the Co amount, and the Ni amount are not more than values determined by a straight line drawn on a point A (1.0, 2.7%) and a point B (2.5, 1.0%) in the orthogonal coordinates shown in the attached drawing of  FIG. 2  which represents a relationship between the above square value and the Ni amount, and an amount ratio of Mo/(Mo+0.5 W) is not less than 0.5; or    an amount ratio of W/Mo, and the Mn amount are not more than values determined by a straight line drawn on a point C (1.3, 0.15%) and a point D (2.5, 0.37%) in the orthogonal coordinates shown in the attached drawing of  FIG. 4  which represents a relationship between the amount ratio and the Mn amount; or    an amount ratio of Mo/(Mo+0.5 W), and the Mn amount are not less than values determined by a straight line drawn on a point E (0.25, 0.4%) and a point F (0.7, 0.15%) in the orthogonal coordinates shown in the attached drawing of  FIG. 6  which represents a relationship between the amount ratio and the Mn amount.    
     
     
         11 . A disc for a gas turbine, which is a disc member comprising a circumferential implanting section for a turbine blade, and a plurality of bores receiving a plurality of stacking bolts by which a plurality of the disc members are integrally fastened to one another, wherein 
 the disc is made of a martensitic steel comprising, by weight, 0.05 to 0.30% C, not more than 0.50% Si, not more than 0.60% Mn, 8.0 to 13.0% Cr, 0.5 to 3.0% Ni, 1.0 to 3.0% Mo, 0.1 to 1.5% tungsten (W), 0.5 to 4% Co, 0.05 to 0.35% vanadium (V), 0.02 to 0.30% in total of one or two elements selected from the group consisting of Nb and Ta, and 0.02 to 0.10% nitrogen (N), wherein    a value of the square of a difference between the Ni amount and the Co amount, and the Ni amount are not more than values determined by a straight line drawn on a point A (1.0, 2.7%) and a point B (2.5, 1.0%) in the orthogonal coordinates shown in the attached drawing of  FIG. 2  which represents a relationship between the above square value and the Ni amount, and an amount ratio of Mo/(Mo+0.5 W) is not less than 0.5; or    an amount ratio of W/Mo, and the Mn amount are not more than values determined by a straight line drawn on a point C (1.3, 0.15%) and a point D (2.5, 0.37%) in the orthogonal coordinates shown in the attached drawing of  FIG. 4  which represents a relationship between the amount ratio and the Mn amount; or    an amount ratio of Mo/(Mo+0.5 W), and the Mn amount are not less than values determined by a straight line drawn on a point E (0.25, 0.4%) and a point F (0.7, 0.15%) in the orthogonal coordinates shown in the attached drawing of  FIG. 6  which represents a relationship between the amount ratio and the Mn amount.    
     
     
         12 . A gas turbine distant piece which is a cylindrical member comprising protrusions provided at both opposite ends of the cylindrical member; a plurality of bores in one of the protrusions, which receive a plurality of stacking bolts by which the cylindrical member is integrally fastened to turbine discs, and a plurality of other bores in the other protrusion, which receive a plurality of other stacking bolts by which the cylindrical member is integrally fastened to compressor discs, wherein the gas turbine distant piece is made of a martensitic steel comprising, by weight, 0.05 to 0.30% C, not more than 0.50% Si, not more than 0.60% Mn, 8.0 to 13.0% Cr, 0.5 to 3.0% Ni, 1.0 to 3.0% Mo, 0.1 to 1.5% tungsten (W), 0.5 to 4% Co, 0.05 to 0.35% vanadium (V), 0.02 to 0.30% in total of one or two elements selected from the group consisting of Nb and Ta, and 0.02 to 0.10% nitrogen (N), and wherein 
 a value of the square of a difference between the Ni amount and the Co amount, and the Ni amount are not more than values determined by a straight line drawn on a point A (1.0, 2.7%) and a point B (2.5, 1.0%) in the orthogonal coordinates shown in the attached drawing of  FIG. 2  which represents a relationship between the above square value and the Ni amount, and an amount ratio of Mo/(Mo+0.5 W) is not less than 0.5; or    an amount ratio of W/Mo, and the Mn amount are not more than values determined by a straight line drawn on a point C (1.3, 0.15%) and a point D (2.5, 0.37%) in the orthogonal coordinates shown in the attached drawing of  FIG. 4  which represents a relationship between the amount ratio and the Mn amount; or    an amount ratio of Mo/(Mo+0.5 W), and the Mn amount are not less than values determined by a straight line drawn on a point E (0.25, 0.4%) and a point F (0.7, 0.15%) in the orthogonal coordinates shown in the attached drawing of  FIG. 6  which represents a relationship between the amount ratio and the Mn amount.    
     
     
         13 . A gas turbine compressor disc which is a disc member comprising 
 a circumferential implanting section for a compressor blade, and a plurality of bores receiving a plurality of stacking bolts by which a plurality of the disc members are integrally fastened to one another, wherein the gas turbine compressor disc is made of a martensitic steel comprising, by weight, 0.05 to 0.30% C, not more than 0.50% Si, not more than 0.60% Mn, 8.0 to 13.0% Cr, 0.5 to 3.0% Ni, 1.0 to 3.0% Mo, 0.1 to 1.5% tungsten (W), 0.5 to 4% Co, 0.05 to 0.35% vanadium (V), 0.02 to 0.30% in total of one or two elements selected from the group consisting of Nb and Ta, and 0.02 to 0.10% nitrogen (N), and wherein    a value of the square of a difference between the Ni amount and the Co amount, and the Ni amount are not more than values determined by a straight line drawn on a point A (1.0, 2.7%) and a point B (2.5, 1.0%) in the orthogonal coordinates shown in the attached drawing of  FIG. 2  which represents a relationship between the above square value and the Ni amount, and an amount ratio of Mo/(Mo+0.5 W) is not less than 0.5; or    an amount ratio of W/Mo, and the Mn amount are not more than values determined by a straight line drawn on a point C (1.3, 0.15%) and a point D (2.5, 0.37%) in the orthogonal coordinates shown in the attached drawing of  FIG. 4  which represents a relationship between the amount ratio and the Mn amount; or    an amount ratio of Mo/(Mo+0.5 W), and the Mn amount are not less than values determined by a straight line drawn on a point E (0.25, 0.4%) and a point F (0.7, 0.15%) in the orthogonal coordinates shown in the attached drawing of  FIG. 6  which represents a relationship between the amount ratio and the Mn amount.    
     
     
         14 . A gas turbine stacking bolt which is a bar member comprising a screw portion at one end thereof, and a polygonal head portion at the other end, wherein the gas turbine stacking bolt is made of a martensitic steel comprising, by weight, 0.05 to 0.30% C, not more than 0.50% Si, not more than 0.60% Mn, 8.0 to 13.0% Cr, 0.5 to 3.0% Ni, 1.0 to 3.0% Mo, 0.1 to 1.5% tungsten (W), 0.5 to 4% Co, 0.05 to 0.35% vanadium (V), 0.02 to 0.30% in total of one or two elements selected from the group consisting of Nb and Ta, and 0.02 to 0.10% nitrogen (N), and wherein 
 a value of the square of a difference between the Ni amount and the Co amount, and the Ni amount are not more than values determined by a straight line drawn on a point A (1.0, 2.7%) and a point B (2.5, 1.0%) in the orthogonal coordinates shown in the attached drawing of  FIG. 2  which represents a relationship between the above square value and the Ni amount, and an amount ratio of Mo/(Mo+0.5 W) is not less than 0.5; or    an amount ratio of W/Mo, and the Mn amount are not more than values determined by a straight line drawn on a point C (1.3, 0.15%) and a point D (2.5, 0.37%) in the orthogonal coordinates shown in the attached drawing of  FIG. 4  which represents a relationship between the amount ratio and the Mn amount; or    an amount ratio of Mo/(Mo+0.5 W), and the Mn amount are not less than values determined by a straight line drawn on a point E (0.25, 0.4%) and a point F (0.7, 0.15%) in the orthogonal coordinates shown in the attached drawing of  FIG. 6  which represents a relationship between the amount ratio and the Mn amount.