Processing for cast components

Abstract

Methods and apparatus for cast metallic components with improved fatigue characteristics. Some embodiments include cryogenic processing of the cast material, such as aluminum C355, 354, or A354, and alloys such as Inconel 713C, IN713LC, IN-738, IN-100 or GMR235 prior to or after machining of the cast component. Other embodiments include an object cast from an aluminum compound including up to 1 percent scandium, 1 percent lithium, or combinations of the two.

1 . A method for manufacturing a centrifugal compressor, comprising: 
 casting a compressor wheel from aluminum;    cooling the cast wheel to a temperature less than about −150 degrees Centigrade; and    machining the wheel after said cooling.    
   
   
       2 . The method of  claim 1  wherein the aluminum is selected from the group including C355, 354, and A354.  
   
   
       3 . The method of  claim 1  wherein the aluminum includes more than about one-tenth percent by weight of lithium.  
   
   
       4 . The method of  claim 1  wherein the aluminum includes more than about one-tenth percent by weight of scandium.  
   
   
       5 . The method of  claim 1  which further comprises heating the compressor wheel to precipitation harden the aluminum after said cooling.  
   
   
       6 . The method of  claim 5  which further comprises heating the cast wheel to a solution heat treatment temperature before said cooling.  
   
   
       7 . The method of  claim 6  wherein the aluminum is selected from the group including C355, 354, and A354.  
   
   
       8 . The method of  claim 7  which further comprises hot isostatic processing of the wheel before said cooling.  
   
   
       9 . The method of  claim 1  which further comprises heating the compressor wheel to precipitation harden the aluminum before said cooling.  
   
   
       10 . The method of  claim 9  which further comprises heating the cast wheel to a solution heat treatment temperature before said heating.  
   
   
       11 . The method of  claim 10  wherein the aluminum is selected from the group including C355, 354, and A354.  
   
   
       12 . The method of  claim 11  which further comprises hot isostatic processing of the wheel before said cooling.  
   
   
       13 . The method of  claim 1  wherein said cooling includes maintaining a temperature less than about −150 degrees Centigrade for more than about eight hours.  
   
   
       14 . The method of  claim 13  wherein said cooling is to a temperature less than about −180 degrees Centigrade and greater than about −200 degrees Centigrade.  
   
   
       15 . The method of  claim 1  which further comprises hot isostatic processing of the wheel before said cooling.  
   
   
       16 . The method of  claim 1  which further comprises heating the cast wheel to a solution heat treatment temperature before said cooling.  
   
   
       17 . The method of  claim 1  which further comprises heat treating the cast wheel after said cooling and before said machining  
   
   
       18 . The method of  claim 17  wherein said heat treating is chosen from the group of annealing at a temperature less than about 145 degrees Centigrade and precipitation hardening at a temperature greater than about 145 degrees Centigrade.  
   
   
       19 . The method of  claim 17  wherein said cooling is a first cooling of the cast wheel and which further comprises a second cooling of the cast wheel to a temperature less than about −150 degrees Centigrade after said heat treating and before said machining.  
   
   
       20 . A method for manufacturing an object, comprising: 
 casting the object from a metal;    cryogenically processing the cast object to a temperature less than about −150 degrees Centigrade; and    precipitation hardening the cast object after said cryogenically processing.    
   
   
       21 . The method of  claim 20  wherein the metal is a castable aluminum containing more than about four percent by weight of silicon.  
   
   
       22 . The method of  claim 20  wherein the aluminum is a castable aluminum that includes more than about one-tenth percent by weight of lithium.  
   
   
       23 . The method of  claim 20  wherein the aluminum is a castable aluminum that includes more than about one-tenth percent by weight of scandium.  
   
   
       24 . The method of  claim 20  wherein said precipitation hardening includes heating the cast object to more than about 145 degrees Centigrade.  
   
   
       25 . The method of  claim 20  wherein said casting is with aluminum material chosen from the group of C355, 354, and A354.  
   
   
       26 . The method of  claim 20  wherein said casting is with material chosen from the group of nickel based alloys.  
   
   
       27 . The method of  claim 26  wherein said casting is with material chosen from the group of IN 713C, IN 713LC, IN-738, IN-100 and GMR235.  
   
   
       28 . The method of  claim 20  wherein said casting is with material including GMR235.  
   
   
       29 . The method of  claim 20  wherein the object is a compressor wheel.  
   
   
       30 . The method of  claim 20  wherein the object is a turbine wheel.  
   
   
       31 . A castable composition comprising from about four percent by weight to about twelve percent by weight silicon, more than eighty percent by weight aluminum, and more than about 0.1 percent and less than about 1 percent chosen from the group including scandium and lithium.  
   
   
       32 . The composition of  claim 31  which includes from about four percent to about eight percent silicon and more than about eighty five percent by weight aluminum.  
   
   
       33 . The composition of  claim 31  which further comprises more than about one percent by weight copper.