Heat-resisting steel, heat treatment method for heat-resisting steel and high-temperature steam turbine rotor

Abstract

A heat-resisting steel consisting of, in percentage by weight, 0.25 to 0.35 of C, 0.15 or less of Si, 0.2 to 0.8 of Mn, 0.3 to 0.6 of Ni, 1.6 to 1.9 of Cr, 0.26 to 0.35 of V, 0.6 to 0.9 of Mo, 0.9 to 1.4 of W, less than 0.01 of Ti, 0.001 to 0.007 of N, 1.3 to 1.4 of a total of Mo and W/2 and the balance of Fe and inevitable impurities, wherein the heat-resisting steel consists of a bainite single phase structure securing 3.5 or more of a total amount of precipitates as 1.0 or more of Fe, 0.8 to 0.9 of Cr, 0.4 to 0.5 of Mo, 0.3 to 0.5 of W and 0.2 or more of V in percentage by weight are moved into the precipitates after a tempering heat treatment.

1 . A heat-resisting steel consisting of, in percentage by weight, 0.25 to 0.35 of C, 0.15 or less of Si, 0.2 to 0.8 of Mn, 0.3 to 0.6 of Ni, 1.6 to 1.9 of Cr, 0.26 to 0.35 of V, 0.6 to 0.9 of Mo, 0.9 to 1.4 of W, less than 0.01 of Ti, 0.001 to 0.007 of N, 1.3 to 1.4 of a total of Mo and W/2 and the balance of Fe and inevitable impurities, wherein the heat-resisting steel consists of a bainite single phase structure securing 3.5 or more of a total amount of precipitates as 1.0 or more of Fe, 0.8 to 0.9 of Cr, 0.4 to 0.5 of Mo, 0.3 to 0.5 of W and 0.2 or more of V in percentage by weight are moved into the precipitates after a tempering heat treatment.  
   
   
       2 . A heat-resisting steel according to  claim 1 , wherein the Ti and/or N is replaced by Fe and C.  
   
   
       3 . A heat-resisting steel according to  claim 1  or  2 , 
 wherein the heat-resisting steel has a tempered bainite single phase structure having a prior austenite grain diameter of 100 μm or less in average, and the precipitate types are not changed even if M, RC type precipitates, M, VC, R type precipitates, M, QC type precipitates and MC type precipitates are deposited in the bainite single phase structure and exposed to high-temperature steam of a prescribed temperature for 100,000 hour equivalent.    
   
   
       4 . A heat-resisting steel consisting of, in percentage by weight, 0.25 to 0.35 of C, 0.15 or less of Si, 0.2 to 0.8 of Mn, 0.3 to 0.6 of Ni, 1.6 to 1.9 of Cr, 0.26 to 0.35 of V, 0.6 to 0.9 of Mo, 0.9 to 1.4 of W, less than 0.01 of Ti, 1.3 to 1.4 of a total of Mo and W/2 and the balance of Fe and inevitable impurities, wherein the heat-resisting steel consists of a bainite single phase structure securing 3.5 or more of a total amount of precipitates as 1.0 or more of Fe, 0.8 to 0.9 of Cr, 0.4 to 0.5 of Mo, 0.3 to 0.5 of W and 0.2 or more of V in percentage by weight are moved into the precipitates after a tempering heat treatment.  
   
   
       5 . A heat-resisting steel according to  claim 4 , wherein the Ti and/or N is replaced by Fe and C.  
   
   
       6 . A heat-resisting steel according to  claim 4  or  5 , wherein the heat-resisting steel has a tempered bainite single phase structure having a prior austenite grain diameter of 100 μm or less in average, and the precipitate types are not changed even if M, RC type precipitates, M, VC, R type precipitates, M,QC type precipitates and MC type precipitates are deposited in the bainite single phase structure and exposed to high-temperature steam of a prescribed temperature for 100,000 hour equivalent.  
   
   
       7 . A heat-resisting steel consisting of, in percentage by weight, 0.25 to 0.35 of C, 0.15 or less of Si, 0.2 to 0.8 of Mn, 0.3 to 0.6 of Ni, 1.6 to 1.9 of Cr, 0.26 to 0.35 of V, 0.6 to 0.9 of Mo, 0.9 to 1.4 of W, 0.001 to 0.007 of N, 1.3 to 1.4 of a total of Mo and W/2 and the balance of Fe and inevitable impurities, wherein the heat-resisting steel consists of a bainite single phase structure securing 3.5 or more of a total amount of precipitates as 1.0 or more of Fe, 0.8 to 0.9 of Cr, 0.4 to 0.5 of Mo, 0.3 to 0.5 of W and 0.2 or more of V in percentage by weight are moved into the precipitates after a tempering heat treatment.  
   
   
       8 . A heat-resisting steel according to  claim 7 , wherein the Ti and/or N is replaced by Fe and C.  
   
   
       9 . A heat-resisting steel according to  claim 7  or  8 , wherein the heat-resisting steel has a tempered bainite single phase structure having a prior austenite grain diameter of 100 μm or less in average, and the precipitate types are not changed even if M, RC type precipitates, M, VC, R type precipitates, M, QC type precipitates and MC type precipitates are deposited in the bainite single phase structure and exposed to high-temperature steam of a prescribed temperature for 100,000 hour equivalent.  
   
   
       10 . A heat treatment method for a heat-resisting steel, comprising: 
 heating to 980 to 1030° C. a steel ingot which consists of, in percentage by weight, 0.25 to 0.35 of C, 0.15 or less of Si, 0.2 to 0.8 of Mn, 0.3 to 0.6 of Ni, 1.6 to 1.9 of Cr, 0.26 to 0.35 of V, 0.6 to 0.9 of Mo, 0.9 to 1.4 of W, less than 0.01 of Ti, 0.001 to 0.007 of N, 1.3 to 1.4 of a total of Mo and W/2 and the balance of Fe and inevitable impurities, cooling such that a cooling speed at the center portion of the steel ingot becomes at least 20° C./h or more, and conducting a tempering treatment.    
   
   
       11 . A heat treatment method for a heat-resisting steel, comprising: 
 heating to 980 to 1030° C. a steel ingot which consists of, in percentage by weight, 0.25 to 0.35 of C, 0.15 or less of Si, 0.2 to 0.8 of Mn, 0.3 to 0.6 of Ni, 1.6 to 1.9 of Cr, 0.26 to 0.35 of V, 0.6 to 0.9 of Mo, 0.9 to 1.4 of W, less than 0.01 of Ti, 1.3 to 1.4 of a total of Mo and W/2 and the balance of Fe and inevitable impurities, cooling such that a cooling speed at the center portion of the steel ingot becomes at least 20° C./h or more, and conducting a tempering treatment.    
   
   
       12 . A heat treatment method for a heat-resisting steel, comprising: 
 heating to 980 to 1030° C. a steel ingot which consists of, in percentage by weight, 0.25 to 0.35 of C, 0.15 or less of Si, 0.2 to 0.8 of Mn, 0.3 to 0.6 of Ni, 1.6 to 1.9 of Cr, 0.26 to 0.35 of V, 0.6 to 0.9 of Mo, 0.9 to 1.4 of W, 0.001 to 0.007 of N, 1.3 to 1.4 of a total of Mo and W/2 and the balance of Fe and inevitable impurities, cooling such that a cooling speed at the center portion of the steel ingot becomes at least 20° C./h or more, and conducting a tempering treatment.    
   
   
       13 . A high-temperature steam turbine rotor comprising a heat-resisting steel which consists of, in percentage by weight, 0.25 to 0.35 of C, 0.15 or less of Si, 0.2 to 0.8 of Mn, 0.3 to 0.6 of Ni, 1.6 to 1.9 of Cr, 0.26 to 0.35 of V, 0.6 to 0.9 of Mo, 0.9 to 1.4 of W, less than 0.01 of Ti, 0.001 to 0.007 of N, 1.3 to 1.4 of a total of Mo and W/2 and the balance of Fe and inevitable impurities, 
 wherein the heat-resisting steel consists of a bainite single phase structure securing 3.5 or more of a total amount of precipitates as 1.0 or more of Fe, 0.8 to 0.9 of Cr, 0.4 to 0.5 of Mo, 0.3 to 0.5 of W and 0.2 or more of V in percentage by weight are moved into the precipitates after a tempering heat treatment.    
   
   
       14 . A high-temperature steam turbine rotor according to  claim 13 , 
 wherein a total amount of the precipitates secured after operating for 100,000 hour equivalent is 2.8% or more in the vicinity of a portion of the high-temperature steam turbine rotor exposed to steam of the maximum temperature at the time of a steady operation.    
   
   
       15 . A high-temperature steam turbine rotor according to claims  13  and  14 , 
 wherein the high-temperature steam turbine rotor has a tempered bainite single phase structure having a prior austenite grain diameter of 100 μm or less in average, and the precipitate types are not changed even if M, RC type precipitates, M, VC, R type precipitates, M, QC type precipitates and MC type precipitates are deposited in the bainite single phase structure and exposed to steam of the maximum temperature for 100,000 hour equivalent at the time of a steady operation.    
   
   
       16 . A high-temperature steam turbine rotor according to  claim 13 , wherein the Ti and/or N is replaced by Fe and C.  
   
   
       17 . A high-temperature steam turbine rotor, comprising a heat-resisting steel which consists of, in percentage by weight, 0.25 to 0.35 of C, 0.15 or less of Si, 0.2 to 0.8 of Mn, 0.3 to 0.6 of Ni, 1.6 to 1.9 of Cr, 0.26 to 0.35 of V, 0.6 to 0.9 of Mo, 0.9 to 1.4 of W, less than 0.01 of Ti, 1.3 to 1.4 of a total of Mo and W/2 and the balance of Fe and inevitable impurities, 
 wherein the heat-resisting steel consists of a bainite single phase structure securing 3.5 or more of a total amount of precipitates as 1.0 or more of Fe, 0.8 to 0.9 of Cr, 0.4 to 0.5 of Mo, 0.3 to 0.5 of W and 0.2 or more of V in percentage by weight are moved into the precipitates after a tempering heat treatment.    
   
   
       18 . A high-temperature steam turbine rotor according to  claim 17 , 
 wherein a total amount of the precipitates secured after operating for 100,000 hour equivalent is 2.8% or more in the vicinity of a portion of the high-temperature steam turbine rotor exposed to steam of the maximum temperature at the time of a steady operation.    
   
   
       19 . A high-temperature steam turbine rotor according to claims  17  and  18 , 
 wherein the high-temperature steam turbine rotor has a tempered bainite single phase structure having a prior austenite grain diameter of 100 μm or less in average, and the precipitate types are not changed even if M, RC type precipitates, M, VC, R type precipitates, M, QC type precipitates and MC type precipitates are deposited in the bainite single phase structure and exposed to steam of the maximum temperature for 100,000 hour equivalent at the time of a steady operation.    
   
   
       20 . A high-temperature steam turbine rotor according to  claim 17 , wherein the Ti and/or N is replaced by Fe and C.  
   
   
       21 . A high-temperature steam turbine rotor, comprising a heat-resisting steel which consists of, in percentage by weight, 0.25 to 0.35 of C, 0.15 or less of Si, 0.2 to 0.8 of Mn, 0.3 to 0.6 of Ni, 1.6 to 1.9 of Cr, 0.26 to 0.35 of V, 0.6 to 0.9 of Mo, 0.9 to 1.4 of W, 0.001 to 0.007 of N, 1.3 to 1.4 of a total of Mo and W/2 and the balance of Fe and inevitable impurities, wherein the heat-resisting steel consists of a bainite single phase structure securing 3.5 or more of a total amount of precipitates as 1.0 or more of Fe, 0.8 to 0.9 of Cr, 0.4 to 0.5 of Mo, 0.3 to 0.5 of W and 0.2 or more of V in percentage by weight are moved into the precipitates after a tempering heat treatment.  
   
   
       22 . A high-temperature steam turbine rotor according to  claim 21 , 
 wherein a total amount of the precipitates secured after operating for 100,000 hour equivalent is 2.8% or more in the vicinity of a portion of the high-temperature steam turbine rotor exposed to steam of the maximum temperature at the time of a steady operation.    
   
   
       23 . A high-temperature steam turbine rotor according to claims  21  and  22 , 
 wherein the high-temperature steam turbine rotor has a tempered bainite single phase structure having a prior austenite grain diameter of 100 μm or less in average, and the precipitate types are not changed even if M, RC type precipitates, M, VC, R type precipitates, M, QC type precipitates and MC type precipitates are deposited in the bainite single phase structure and exposed to steam of the maximum temperature for 100,000 hour equivalent at the time of a steady operation.    
   
   
       24 . A high-temperature steam turbine rotor according to  claim 21 , wherein the Ti and/or N is replaced by Fe and C.