Heat-resisting steel and method of manufacturing the same

Abstract

Provided is a heat-resisting steel, which can be operated stably under a high-temperatures steam environment and which provides an excellent economic advantage. The particular heat-resisting steel comprises 0.25 to 0.35% by mass of C, not more than 0.15% by mass of Si, 0.2 to 0.8% by mass of Mn, 0.3 to 0.6% by mass of Ni, 1.6 to 1.9% by mass of Cr, 0.26 to 0.35% by mass of V, 0.6 to 1.1% by mass of Mo, 0.6 to 1.4% by mass of W, 1.3 to 1.4% by mass of Mo+W/2, and the balance of Fe and unavoidable impurities.

What is claimed is:  
     
         1 . A heat-resisting steel, comprising 0.25 to 0.35% by mass of C, not more than 0.15% by mass of Si, 0.2 to 0.8% by mass of Mn, 0.3 to 0.6% by mass of Ni, 1.6 to 1.9% by mass of Cr, 0.26 to 0.35% by mass of V, 0.6 to 1.1% by mass of Mo, 0.6 to 1.4% by mass of W, 1.3 to 1.4% by mass of Mo+W/2, and the balance of Fe and unavoidable impurities.  
     
     
         2 . A heat-resisting steel according to  claim 1 , further comprising 0.002 to 0.008% by mass of N.  
     
     
         3 . A heat-resisting steel according to  claim 1 , further comprising 0.001 to 0.004% by mass of B.  
     
     
         4 . A heat-resisting steel according to  claim 1 , further comprising 0.002 to 0.008% by mass of N and 0.001 to 0.004% by mass of B.  
     
     
         5 . A heat-resisting steel, comprising 0.25 to 0.35% by mass of C, not more than 0.15% by mass of Si, 0.2 to 0.8% by mass of Mn, 0.3 to 0.6% by mass of Ni, 1.6 to 1.9% by mass of Cr, 0.23 to 0.30% by mass of V, 0.6 to 1.1% by mass of Mo, 0.6 to 1.4% by mass of W, 0.001 to 0.008% by mass of Nb, 1.3 to 1.4% by mass of Mo+W/2, and the balance of Fe and unavoidable impurities.  
     
     
         6 . A heat-resisting steel according to  claim 5 , further comprising 0.002 to 0.008% by mass of N.  
     
     
         7 . A heat-resisting steel having precipitates of M 7 C 3  type, MX type and M 23 C 6  type, which are precipitated within the crystal grains or at the crystal grain boundaries as a result of a hot forging treatment, an annealing treatment, a normalizing treatment, a quenching treatment and a tempering treatment applied in the order mentioned to a steel comprising 0.25 to 0.35% by mass of C, not more than 0.15% by mass of Si, 0.2 to 0.8% by mass of Mn, 0.3 to 0.6% by mass of Ni, 1.6 to 1.9% by mass of Cr, 0.26 to 0.35% by mass of V, 0.6 to 1.1% by mass of Mo, 0.6 to 1.4% by mass of W, 1.3 to 1.4% by mass of Mo+W/2, and the balance of Fe and unavoidable impurities, the sum of said precipitates falling within a range of 0.5% to 2.0% by mass.  
     
     
         8 . A heat-resisting steel having precipitates of M 7 C 3  type, MX type and M 23 C 6  type, which are precipitated within the crystal grains or at the crystal grain boundaries as a result of a hot forging treatment, an annealing treatment, a normalizing treatment, a quenching treatment and a tempering treatment applied in the order mentioned to a steel comprising 0.25 to 0.35% by mass of C, not more than 0.15% by mass of Si, 0.2 to 0.8% by mass of Mn, 0.3 to 0.6% by mass of Ni, 1.6 to 1.9% by mass of Cr, 0.23 to 0.30% by mass of V, 0.6 to 1.1% by mass of Mo, 0.6 to 1.4% by mass of W, 0.001 to 0.008% by mass of Nb, 1.3 to 1.4% by mass of Mo+W/2, and the balance of Fe and unavoidable impurities, the sum of said precipitates falling within a range of 0.5% to 2.0% by mass.  
     
     
         9 . A method of manufacturing a heat-resisting steel, comprising manufacturing by an electroslag remelting process a steel comprising 0.25 to 0.35% by mass of C, not more than 0.15% by mass of Si, 0.2 to 0.8% by mass of Mn, 0.3 to 0.6% by mass of Ni, 1.6 to 1.9% by mass of Cr, 0.26 to 0.35% by mass of V, 0.6 to 1.1% by mass of Mo, 0.6 to 1.4% by mass of W, 1.3 to 1.4% by mass of Mo+W/2, and the balance of Fe and unavoidable impurities.  
     
     
         10 . A method of manufacturing a heat-resisting steel, comprising manufacturing by an electroslag remelting process a steel comprising 0.25 to 0.35% by mass of C, not more than 0.15% by mass of Si, 0.2 to 0.8% by mass of Mn, 0.3 to 0.6% by mass of Ni, 1.6 to 1.9% by mass of Cr, 0.23 to 0.30% by mass of V, 0.6 to 1.1% by mass of Mo, 0.6 to 1.4% by mass of W, 0.001 to 0.008% by mass of Nb, 1.3 to 1.4% by mass of Mo+W/2, and the balance of Fe and unavoidable impurities.  
     
     
         11 . A method of manufacturing a heat-resisting steel, comprising applying a quenching treatment to a steel comprising 0.25 to 0.35% by mass of C, not more than 0.15% by mass of Si, 0.2 to 0.8% by mass of Mn, 0.3 to 0.6% by mass of Ni, 1.6 to 1.9% by mass of Cr, 0.26 to 0.35% by mass of V, 0.6 to 1.1% by mass of Mo, 0.6 to 1.4% by mass of W, 1.3 to 1.4% by mass of Mo+W/2, and the balance of Fe and unavoidable impurities, the initiating temperature of said quenching treatment falling within a range of 970° C. to 1,020° C.  
     
     
         12 . A method of manufacturing a heat-resisting steel according to  claim 11 , wherein said steel further comprises 0.002 to 0.008% by mass of N.  
     
     
         13 . A method of manufacturing a heat-resisting steel according to  claim 11 , wherein said steel further comprises 0.001 to 0.004% by mass of B.  
     
     
         14 . A method of manufacturing a heat-resisting steel according to  claim 11 , wherein said steel further comprises 0.002 to 0.008% by mass of N and 0.001 to 0.004% by mass of B.  
     
     
         15 . A method of manufacturing a heat-resisting steel, comprising applying a quenching treatment to a steel comprising 0.25 to 0.35% by mass of C, not more than 0.15% by mass of Si, 0.2 to 0.8% by mass of Mn, 0.3 to 0.6% by mass of Ni, 1.6 to 1.9% by mass of Cr, 0.23 to 0.30% by mass of V, 0.6 to 1.1% by mass of Mo, 0.6 to 1.4% by mass of W, 0.001 to 0.008% by mass of Nb, 1.3 to 1.4% by mass of Mo+W/2, and the balance of Fe and unavoidable impurities, the initiating temperature of said quenching treatment falling within a range of 1,020° C. to 1,050° C.  
     
     
         16 . A method of manufacturing a heat-resisting steel according to  claim 15 , wherein said steel further comprises 0.002 to 0.008% by mass of N.  
     
     
         17 . A method of manufacturing a heat-resisting steel according to  claim 11 , wherein the cooling rate in said quenching treatment is set at 100° C./hour or more.  
     
     
         18 . A method of manufacturing a heat-resisting steel according to  claim 15 , wherein the cooling rate in said quenching treatment is set at 100° C./hour or more.