Systems and methods for improving iron-based camshaft fatigue life

Abstract

A method of casting a camshaft including iron includes determining a cooling rate profile based on a chemical composition of the camshaft and a target bearing life of the camshaft. The method includes casting the camshaft including cooling the camshaft in a chiller based on the cooling rate profile. The method includes imparting the camshaft with a microstructure comprising carbide, ledeburite, pearlite, ausferrite, or combinations thereof.

1 . A method of casting a camshaft comprising iron, comprising:
 determining a cooling rate profile based on a chemical composition of the camshaft and a target bearing life of the camshaft;   casting the camshaft including cooling the camshaft in a chiller based on the cooling rate profile; and   imparting the camshaft with a microstructure comprising ledeburite, carbide, and pearlite.   
     
     
         2 . The method of  claim 1 , further comprising austempering the camshaft to homogenize the pearlite. 
     
     
         3 . The method of  claim 1 , wherein the cooling rate profile includes a cooling rate that changes over time. 
     
     
         4 . The method of  claim 1 , wherein the cooling rate profile includes a cooling rate that is constant over time. 
     
     
         5 . The method of  claim 1 , wherein the cooling rate profile is determined further based on a geometry of the chiller, a size of the chiller, a wall thickness of the chiller, a mass of the camshaft, a thickness of the camshaft, a size of the camshaft, a target hardness of the camshaft, or combinations thereof. 
     
     
         6 . The method of  claim 1 , wherein cooling the camshaft decreases an amount of graphite nodules in the microstructure of the camshaft. 
     
     
         7 . The method of  claim 1 , wherein casting the camshaft further includes pouring molten iron into a mold before cooling the camshaft such that the cooled camshaft comprises chilled ductile iron. 
     
     
         8 . The method of  claim 1 , wherein imparting the camshaft with the microstructure includes realizing the microstructure based on the chemical composition of the camshaft and the cooling of the camshaft according to the cooling rate profile. 
     
     
         9 . A method of casting a camshaft comprising iron, comprising:
 determining a cooling rate profile based on a chemical composition of the camshaft and a target bearing life of the camshaft;   casting the camshaft including cooling the camshaft in a chiller based on the cooling rate profile;   imparting the camshaft with a microstructure comprising carbide and ledeburite; and   austempering the camshaft to treat the microstructure.   
     
     
         10 . The method of  claim 9 , wherein the cooling rate profile includes a cooling rate that varies over time. 
     
     
         11 . The method of  claim 9 , wherein imparting the camshaft with the microstructure produces a first amount of carbide and a second amount of ledeburite, the second amount being greater than the first amount. 
     
     
         12 . The method of  claim 9 , wherein imparting the camshaft with the microstructure forms pearlite in the microstructure. 
     
     
         13 . The method of  claim 12 , wherein austempering the camshaft transforms the pearlite in the microstructure into ausferrite. 
     
     
         14 . The method of  claim 9 , wherein cooling the camshaft includes treating the camshaft in the chiller at different temperatures over different periods of time. 
     
     
         15 . The method of  claim 9 , wherein cooling the camshaft is further based on a wall thickness of the chiller. 
     
     
         16 . The method of  claim 9 , wherein casting the camshaft further includes pouring molten iron into a mold before cooling the camshaft. 
     
     
         17 . The method of  claim 9 , wherein imparting the camshaft with the microstructure includes realizing the microstructure based on the chemical composition of the camshaft and the cooling rate profile. 
     
     
         18 . A method of casting a camshaft comprising iron, comprising:
 determining a cooling rate profile based on a chemical composition of the camshaft and a target bearing life of the camshaft;   casting the camshaft including cooling the camshaft in a chiller based on the cooling rate profile;   imparting the camshaft with a microstructure comprising ledeburite, carbide, and pearlite; and   austempering the camshaft to form ausferrite in the microstructure.   
     
     
         19 . The method of  claim 18 , wherein imparting the camshaft with the microstructure forms lamellar-growth ledeburite and rod-growth ledeburite in the microstructure. 
     
     
         20 . The method of  claim 18 , wherein austempering the camshaft homogenizes the pearlite in the microstructure to form the ausferrite.