Method for decarburization of rotor forging

Abstract

Disclosed herein is a method for decarburization of a rotor forging. In one aspect, a location for applying a weld prep to a rotor forging is identified. The rotor forging is decarburized at the identified location of the weld prep to attain a predetermined carbon content.

1 . A method, comprising:
 obtaining a rotor forging;   identifying a location for applying a weld prep to the rotor forging; and   decarburizing the rotor forging at the identified location for the weld prep to obtain a customizable carbon content thereat, the customizable carbon content at the weld prep location including a carbon content that matches or is below a carbon content of another rotor forging that is configured to be welded with the rotor forging at the weld prep location.   
     
     
         2 . The method according to  claim 1 , wherein the decarburizing comprises placing the rotor forging in a heating unit having an atmosphere tailored to increase a thermodynamic driving force for diffusion of carbon from the forging. 
     
     
         3 . The method according to  claim 1 , wherein the decarburizing comprises applying a slurry. 
     
     
         4 . The method according to  claim 3 , wherein the slurry comprises elements and compounds with a high affinity for carbon. 
     
     
         5 . The method according to  claim 1 , wherein the decarburizing of the rotor forging causes carbon in the forging to diffuse to the surface to form a scale thereon. 
     
     
         6 . The method according to  claim 5 , further comprising removing the scale from the surface of the rotor forging. 
     
     
         7 . The method according to  claim 1 , wherein the decarburizing of the rotor forging at the identified location for the weld prep comprises selectively decarburizing the weld prep to have a lower carbon content than a carbon content of a region in the rotor forging that is remote from the weld prep location. 
     
     
         8 . The method according to  claim 1 , wherein the rotor forging has been partially processed prior to being obtained. 
     
     
         9 . The method according to  claim 8 , further comprising rough machining the partially processed rotor forging to expose a surface that will eventually be machined into the weld prep, wherein the rough machining occurs prior to decarburizing the rotor forging. 
     
     
         10 . The method according to  claim 9 , further comprising applying a heat treatment to the rough-machined rotor forging, wherein the heat treatment is used to perform the decarburization. 
     
     
         11 . The method according to  claim 10 , further comprising machining the weld prep after applying the heat treatment. 
     
     
         12 . The method according to  claim 11 , further comprising decarburizing the machined weld prep in response to determining that the machined prep contained a non-desirable carbon content. 
     
     
         13 . The method according to  claim 1 , wherein the rotor forging has been fully processed prior to being obtained. 
     
     
         14 . The method according to  claim 13 , further comprising rough machining the fully processed rotor forging to expose an envelope of where the weld prep will be located. 
     
     
         15 . The method according to  claim 14 , wherein the decarburizing occurs after rough machining the fully processed rotor forging. 
     
     
         16 . A rotor forging made from the method of  claim 1  having a customizable carbon content. 
     
     
         17 . A method for decarburizing a turbine rotor forging, comprising:
 obtaining a first turbine rotor forging having a first carbon content;   identifying a location for applying a weld prep to the first turbine rotor forging, the identified location forming a root path for welding the first turbine rotor forging to a second turbine rotor forging having a second carbon content; and   decarburizing the identified weld prep location of the first turbine rotor forging to change the properties of the first rotor forging at the identified weld prep location to have a customized carbon content that matches or is below the second carbon content of the second turbine rotor forging.   
     
     
         18 . The method according to  claim 17 , wherein the decarburizing comprises placing the first turbine rotor forging in a furnace having an atmosphere tailored to increase a thermodynamic driving force for diffusion of carbon from the first turbine rotor forging and applying a heat treatment focused on the identified weld prep location. 
     
     
         19 . The method according to  claim 17 , wherein the decarburizing comprises applying a slurry containing elements and compounds with a high affinity for carbon to the identified weld prep location. 
     
     
         20 . The method according to  claim 17 , wherein the decarburizing comprises applying a slurry containing elements and compounds with a high affinity for carbon to the identified weld prep location, placing the first turbine rotor forging in a furnace having an atmosphere tailored to increase a thermodynamic driving force for the diffusion of carbon from the first turbine rotor forging and applying a heat treatment focused on the identified weld prep location.