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+0.5W) 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 for a gas turbine disc, comprising, by weight, 0.05 to 0.30% C, not more than 0.50% Si, 0.05 to 0.30% 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 0.22% of Nb, 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, where the square value does not exceed 1.8, and   wherein an amount ratio of Mo/(Mo+0.5W) is not less than 0.75.   
   
   
       2 . (canceled) 
   
   
       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 - 7 . (canceled) 
   
   
       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 - 14 . (canceled) 
   
   
       15 . A gas turbine disc formed of a heat resisting martensitic steel made by a method as set forth in  claim 1 . 
   
   
       16 . A gas turbine disc formed of a heat resisting martensitic steel made by a method as set forth in  claim 3 . 
   
   
       17 . A gas turbine disc formed of a heat resisting martensitic steel made by a method as set forth in  claim 8 .