SiMo DUCTILE IRON CASTINGS IN GAS TURBINE APPLICATIONS

Abstract

A cast article of a ductile iron wherein the ductile iron includes carbon from about 2.8 to 3.7 w/o, silicon from about 3.0 to 3.5 w/o, molybdenum from 0.8 to 1.5 w/o, magnesium from about 0.025 to 0.60 w/o, sulfur less than 0.01 w/o and nickel from about 0.0 to 1.3 w/o, the remaining content being iron is provided. The cast article is suitable for a gas turbine casing. A method of manufacturing a cast article is also provided.

1 . A gas turbine casing comprising:
 a cast ductile iron wherein the ductile iron comprises: carbon from about 2.8 to 3.7 weight percent, silicon from about 3.0 to 3.5 weight percent, molybdenum from about 0.8 to 1.5 weight percent, magnesium from about 0.025 to 0.60 weight percent, sulfur less than about 0.01 weight percent and nickel from about 0.0 to 1.3 weight percent, the remaining content being iron.   
     
     
         2 . The gas turbine casing of  claim 1 , further comprising phosphorous, titanium, vanadium and tin each at weight percent of less than about 0.05. 
     
     
         3 . The gas turbine casing of  claim 1 , further comprising aluminum, copper and chromium each at weight percent of less than about 0.1. 
     
     
         4 . The gas turbine casing of  claim 1 , further comprising manganese at weight percent of less than about 0.15. 
     
     
         5 . The gas turbine casing of  claim 1  further comprising tungsten at a weight percent of less than about 0.05. 
     
     
         6 . A gas turbine casing comprising:
 a cast ductile iron wherein the ductile iron comprises: carbon from about 2.8 to 3.7 weight percent, silicon from about 3.0 to 3.5 weight percent, molybdenum from about 0.8 to 1.5 weight percent, magnesium from about 0.025 to 0.60 weight percent, sulfur less than 0.01 weight percent, nickel from about 0.0 to 1.3 weight percent, phosphorous less than about 0.05 weight percent, titanium less than about 0.05 weight percent, vanadium less than about 0.05 weight percent, tin less than about 0.05 weight percent, aluminum less than about 0.10 weight percent, copper less than about 0.10 weight percent, chromium less than about 0.10 weight percent, manganese less than about 0.15 weight percent, tungsten less than about 0.05 weight percent, the remaining content being iron.   
     
     
         7 . A method of manufacturing a component, the method comprising:
 melting ductile iron comprising carbon, magnesium, sulfur and nickel, the remaining content being iron to form a melt;   adding inoculants and treatment alloys to the melt;   adding molybdenum to the melt; and   casting the melt to form the component wherein the component comprises carbon from about 2.8 to 3.7 weight percent, silicon from about 3.0 to 3.5 weight percent, molybdenum from about 0.8 to 1.5 weight percent, magnesium from about 0.025 to 0.60 weight percent, sulfur less than 0.01 weight percent and nickel from about 0.0 to 1.3 weight percent, the remaining content being iron.   
     
     
         8 . The method of  claim 7  further comprising:
 annealing the component after casting the melt. 
 
     
     
         9 . The method of  claim 8 , wherein the annealing comprises:
 holding the component at 900° C. for at least 7 hours;   cooling the component to 720° C. and holding for at least 2 hours;   cooling the component to 690° C. and holding for at least 8 hours.   
     
     
         10 . The method of  claim 7  wherein the component comprises a gas turbine casing. 
     
     
         11 . The method of  claim 7 , wherein the component comprises phosphorous, titanium, vanadium, and tin each at weight percent of less than about 0.05. 
     
     
         12 . The method of  claim 7 , wherein the component comprises aluminum, copper and chromium each at weight percent of less than about 0.1. 
     
     
         13 . The method of  claim 7 , wherein the component comprises manganese at weight percent of less than about 0.15. 
     
     
         14 . The method of  claim 7  wherein the component comprises tungsten at a weight percent of less than about 0.05. 
     
     
         15 . The method of  claim 7  wherein the inoculants comprise ferrosilicon. 
     
     
         16 . The method of  claim 15  wherein the inoculants further comprise calcium, germanium, strontium and rare earth elements. 
     
     
         17 . The method of  claim 7  wherein the treatment alloys comprises magnesium and nickel. 
     
     
         18 . The method of  claim 7  further comprising;
 stress relief annealing at about 650 to 750° C. for 1 hour per inch thickness of the component. 
 
     
     
         19 . The method of  claim 7  wherein the casting comprises placement of large cast blocks to remove heat.