Bearing steel having improved fatigue durability and method of manufacturing the same

Abstract

Disclose is an alloy composition for bearing steel having improved fatigue durability and a method of manufacturing the bearing steel comprising the same. The alloy composition comprises: based on a total weight of the alloy composition, an amount of about 0.8 to 1.0 wt % of carbon (C), an amount of about 0.35 to 0.9 wt % of silicon (Si), an amount of about 0.5 to 1.0 wt % of manganese (Mn), an amount of about 0.6 to 1.5 wt % of nickel (Ni), an amount of about 1.2 to 1.55 wt % of chromium (Cr), an amount of about 0.2 to 0.5 wt % of molybdenum (Mo), an amount of about 0.01 to 0.06 wt % of aluminum (Al), an amount of about 0.01 to 0.1 wt % of copper (Cu), and iron (Fe) constituting the balance of the weight of the alloy composition. Preferred alloy composition can provide improved strength, hardness, and fatigue life due to spheroidized carbide complex.

What is claimed is: 
     
         1 . An alloy composition for bearing steel, comprising:
 an amount of about 0.8 to 1.0 wt % of carbon (C);   an amount of about 0.35 to 0.9 wt % of silicon (Si);   an amount of about 0.5 to 1.0 wt % of manganese (Mn);   an amount of about 0.6 to 1.5 wt % of nickel (Ni);   an amount of about 1.2 to 1.55 wt % of chromium (Cr);   an amount of about 0.2 to 0.5 wt % of molybdenum (Mo);   an amount of about 0.01 to 0.06 wt % of aluminum (Al);   an amount of about 0.01 to 0.1 wt % of copper (Cu); and   iron (Fe) constituting the balance of the weight of the alloy composition,   all the wt % based on the total weight of the alloy composition.   
     
     
         2 . The alloy composition of  claim 1  further comprising one or more selected from the group consisting of an amount of more than 0 wt % and about 0.38 wt % or less of vanadium (V) and an amount of more than 0 wt % and about 0.02 wt % or less of niobium (Nb), all the wt % based on the total weight of the alloy composition. 
     
     
         3 . The alloy composition of  claim 1 , wherein the alloy composition further comprises an amount of about 0.006 wt % or less of nitrogen (N), an amount of about 0.001 wt % or less of oxygen (O), an amount of about 0.03 wt % or less of phosphorus (P), and an amount of about 0.01 wt % or less of sulfur (S), all the wt % based on the total weight of the alloy composition. 
     
     
         4 . The alloy composition of  claim 1 , consisting essentially of:
 an amount of about 0.8 to 1.0 wt % of carbon (C);   an amount of about 0.35 to 0.9 wt % of silicon (Si);   an amount of about 0.5 to 1.0 wt % of manganese (Mn);   an amount of about 0.6 to 1.5 wt % of nickel (Ni);   an amount of about 1.2 to 1.55 wt % of chromium (Cr);   an amount of about 0.2 to 0.5 wt % of molybdenum (Mo);   an amount of about 0.01 to 0.06 wt % of aluminum (Al);   an amount of about 0.01 to 0.1 wt % of copper (Cu); and   iron (Fe) constituting the balance of the weight of the alloy composition,   all the wt % based on the total weight of the alloy composition.   
     
     
         5 . The alloy composition of  claim 1 , consisting essentially of:
 an amount of about 0.8 to 1.0 wt % of carbon (C);   an amount of about 0.35 to 0.9 wt % of silicon (Si);   an amount of about 0.5 to 1.0 wt % of manganese (Mn);   an amount of about 0.6 to 1.5 wt % of nickel (Ni);   an amount of about 1.2 to 1.55 wt % of chromium (Cr);   an amount of about 0.2 to 0.5 wt % of molybdenum (Mo);   an amount of about 0.01 to 0.06 wt % of aluminum (Al);   an amount of about 0.01 to 0.1 wt % of copper (Cu);   one or more selected from the group consisting of an amount of more than 0 wt % and about 0.38 wt % or less of vanadium (V) and an amount of more than 0 wt % and about 0.02 wt % or less of niobium (Nb), and   iron (Fe) constituting the balance of the weight of the alloy composition,   all the wt % based on the total weight of the alloy composition.   
     
     
         6 . A method of manufacturing a bearing steel, comprising:
 heat-treating a wire rod comprising an alloy composition, at a temperature of 720 to 850° C. for 4 to 8 hours to spheroidize a complex carbide;   wire-drawing the heat-treated wire rod;   secondarily heat-treating the wire-drawn wire rod at a temperature of 720 to 850° C. for 4 to 8 hours to spheroidize the complex carbide;   forging the secondary heat-treated wire rod to form the bearing steel; and   quenching, rapidly cooling, and tempering the formed bearing steel, wherein the alloy composition comprises: based on a total weight of the alloy composition, an amount of about 0.8 to 1.0 wt % of carbon (C), an amount of about 0.35 to 0.9 wt % of silicon (Si), an amount of about 0.5 to 1.0 wt % of manganese (Mn), an amount of about 0.6 to 1.5 wt % of nickel (Ni), an amount of about 1.2 to 1.55 wt % of chromium (Cr), an amount of about 0.2 to 0.5 wt % of molybdenum (Mo), an amount of about 0.01 to 0.06 wt % of aluminum (Al), an amount of about 0.01 to 0.1 wt % of copper (Cu), and iron (Fe) constituting the balance of the weight of the alloy composition.   
     
     
         7 . The method of  claim 6 , wherein the alloy composition further comprises one or more selected from the group consisting of an amount of more than 0 wt % and about 0.38 wt % or less of vanadium (V) and an amount of more than 0 wt % and about 0.02 wt % or less of niobium (Nb), all the wt % based on the total weight of the alloy composition. 
     
     
         8 . The method of  claim 6 , wherein the quenching is performed at a temperature of 840 to 860° C. for 0.5 to 2 hours, and the tempering is performed at a temperature of 150 to 190° C. for 0.5 to 2 hours. 
     
     
         9 . The method of  claim 6 , wherein the complex carbide comprises one or more selected from the group consisting of M 3 C, M 7 C 3 , M 23 C 6 , and MC carbides, wherein M is a metal or a transition metal. 
     
     
         10 . The method of  claim 9 , wherein the M of the M 3 C, M 7 C 3 , and M 23 C 6  carbides is one or more selected from the group consisting of chromium (Cr), iron (Fe), and manganese (Mn). 
     
     
         11 . The method of  claim 9 , wherein the M of the MC carbide is one or more selected from the group consisting of chromium (Cr), iron (Fe), vanadium (V), niobium (Nb), and molybdenum (Mo). 
     
     
         12 . A vehicle part that comprises an alloy composition of  claim 1 . 
     
     
         13 . The vehicle part of  claim 12 , wherein the vehicle part is a bearing of an engine or a transmission.