Low Alloy Steels with Enhanced Toughness and Fatigue Strength at High Hardness

Abstract

Methods of forming low alloy steels and steels produced by such methods are provided. Various alloy additions and elements, as well as heating and tempering times and method steps are provided herein. Methods and materials of the present disclosure provide for enhanced fatigue at high hardness as compared with more brittle conventional steels.

What is claimed is: 
     
         1 . A method of forming a steel alloy, comprising:
 providing a carbon steel with between approximately 0.40 and approximately 0.60 carbon by weight percent;   adding at least one of manganese, nickel, molybdenum, and tungsten as an alloy addition wherein the at least one alloy addition comprises not more than approximately 2.2 weight percent of the combined carbon steel and the alloy addition;   austenitizing the carbon steel and the at least one alloy addition for between 1500 seconds and 2000 seconds at 900 degrees Celsius and at 1150 degrees Celsius;   quenching the carbon steel and the at least one alloy addition in the presence of helium;   tempering the carbon steel and the at least one alloy addition at a temperature between approximately 150 degrees Celsius and 250 degrees Celsius;   performing a further austenitizing step comprising at least one of induction heating and direct-resistance heating; and   quenching and tempering the carbon steel and the at least one alloy addition at between approximately 150 degrees Celsius and 250 degrees Celsius.   
     
     
         2 . The method of  claim 1 , wherein the at least one of induction heating and direct-resistance heating comprises providing the carbon steel and the at least one alloy addition at 850 degrees Celsius for 2 seconds, at 950 degrees Celsius for 10 seconds, and 1050 degrees Celsius for 1000 seconds. 
     
     
         3 . The method of  claim 1 , wherein the step of quenching and tempering the carbon steel and the at least one alloy addition is performed at a temperature of approximately 200 degrees Celsius. 
     
     
         4 . The method of  claim 1 , wherein at least one of the austenitizing steps is performed with a GLEEBLE™ direct resistance heating system. 
     
     
         5 . A method of forming a steel alloy, comprising:
 providing a carbon steel;   adding an alloy addition wherein the one alloy addition comprises not more than approximately 2.0 weight percent of the combined carbon steel and the alloy addition;   austenitizing the carbon steel and the at least one alloy addition for at least approximately 1,000 seconds at a temperature of at least 900 degrees Celsius;   quenching the carbon steel and the at least one alloy addition;   tempering the carbon steel and the at least one alloy addition at a temperature of not more than approximately 250 degrees Celsius;   performing a second austenitizing step; and   further quenching and tempering the carbon steel and the at least one alloy addition at a temperature of not more than approximately 250 degrees Celsius.   
     
     
         6 . The method of  claim 5 , wherein the carbon steel comprises between approximately 0.40 and approximately 0.60 carbon by weight percent. 
     
     
         7 . The method of  claim 5 , wherein the alloy addition comprises at least one of manganese, nickel, molybdenum, and tungsten. 
     
     
         8 . The method of  claim 5 , wherein at least one of the austenitizing steps is performed with a GLEEBLE™ direct resistance heating system. 
     
     
         9 . The method of  claim 5 , wherein the carbon steel and the at least one alloy addition are austenitized for between approximately 1500 seconds and 2000 seconds. 
     
     
         10 . The method of  claim 5 , wherein the step of quenching is performed in the presence of helium. 
     
     
         11 . The method of  claim 5 , wherein the second austenitizing step comprises at least one of induction heating and direct-resistance heating.