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

Abstract

The present invention relates to a steel composition for bearing having improved fatigue durability and a method of manufacturing the same. The steel composition comprises: an amount of about 0.08 to 1.0 wt % of carbon (C); an amount of about 0.9 to 1.6 wt % of silicon (Si); an amount greater than 0 wt % and of about 0.03 wt % or less of phosphorus (P); an amount greater than 0 wt % and of about 0.01 wt % or less of sulfur (S); an amount of about 0.01 to 0.1 wt % of copper (Cu); an amount of about 0.01 to 0.06 wt % of aluminum (Al); an amount greater than 0 wt % and of about 0.006 wt % or less of nitrogen (N); an amount greater than 0 wt % and of about 0.001 wt % or less of oxygen (O); one or more selected from the group consisting of: an amount of about 0.5 to 1.00 wt % of manganese (Mn), an amount of about 0.1 to 0.6 wt % of nickel (Ni), an amount of about 1.4 to 1.55 wt % of chromium (Cr), an amount of about 0.2 to 0.5 wt % of molybdenum (Mo), and an amount greater than 0 wt % and of about 0.4 wt % or less of vanadium (V); and iron (Fe) constituting the balance of the weight of the steel composition, all wt % based on the total weight of the alloy steel composition

What is claimed is: 
     
         1 . A steel composition for bearing, comprising:
 an amount of about 0.8 to 1.0 wt % of carbon (C);   an amount of about 0.9 to 1.6 wt % of silicon (Si);   an amount greater than 0 wt % and of about 0.03 wt % or less of phosphorus (P);   an amount greater than 0 wt % and of about 0.01 wt % or less of sulfur (S);   an amount of about 0.01 to 0.1 wt % of copper (Cu);   an amount of about 0.01 to 0.06 wt % of aluminum (Al);   an amount greater than 0 wt % and of about 0.006 wt % or less of nitrogen (N);   an amount greater than 0 wt % and of about 0.001 wt % or less of oxygen (O); and   iron (Fe) constituting the balance of the weight of the steel composition,   all wt % based on the total weight of the steel composition.   
     
     
         2 . The steel composition of  claim 1 , further comprising: an amount of about 0.5 to 1.00 wt % of manganese (Mn), based on the total weight of the steel composition. 
     
     
         3 . The steel composition of  claim 1 , further comprising: an amount of about 0.1 to 0.6 wt % of nickel (Ni), based on the total weight of the steel composition. 
     
     
         4 . The steel composition of  claim 1 , further comprising: an amount of about 1.4 to 1.55 wt % of chromium (Cr), based on the total weight of the steel composition. 
     
     
         5 . The steel composition of  claim 1 , further comprising: an amount of about 0.2 to 0.5 wt % of molybdenum (Mo), based on the total weight of the steel composition. 
     
     
         6 . The steel composition of  claim 1 , further comprising: an amount greater than 0 wt % and of about 0.4 wt % or less of vanadium (V), based on the total weight of the steel composition. 
     
     
         7 . The steel composition of  claim 1 , further comprising: one or more selected from the group consisting of: an amount of about 0.5 to 1.00 wt % of manganese (Mn), an amount of about 0.1 to 0.6 wt % of nickel (Ni), an amount of about 1.4 to 1.55 wt % of chromium (Cr), an amount of about 0.2 to 0.5 wt % of molybdenum (Mo), and an amount greater than 0 wt % and of about 0.4 wt % or less of vanadium (V), all wt % based on the total weight of the steel composition. 
     
     
         8 . The steel composition of  claim 1 , consisting essentially of:
 an amount of about 0.08 to 1.0 wt % of carbon (C);   an amount of about 0.9 to 1.6 wt % of silicon (Si);   an amount greater than 0 wt % and of about 0.03 wt % or less of phosphorus (P);   an amount greater than 0 wt % and of about 0.01 wt % or less of sulfur (S);   an amount of about 0.01 to 0.1 wt % of copper (Cu);   an amount of about 0.01 to 0.06 wt % of aluminum (Al);   an amount greater than 0 wt % and of about 0.006 wt % or less of nitrogen (N);   an amount greater than 0 wt % and of about 0.001 wt % or less of oxygen (O); and   iron (Fe) constituting the balance of the weight of the steel composition,   all wt % based on the total weight of the steel composition.   
     
     
         9 . The steel composition of  claim 1 , consisting essentially of:
 an amount of about 0.08 to 1.0 wt % of carbon (C);   an amount of about 0.9 to 1.6 wt % of silicon (Si);   an amount greater than 0 wt % and of about 0.03 wt % or less of phosphorus (P);   an amount greater than 0 wt % and of about 0.01 wt % or less of sulfur (S);   an amount of about 0.01 to 0.1 wt % of copper (Cu);   an amount of about 0.01 to 0.06 wt % of aluminum (Al);   an amount greater than 0 wt % and of about 0.006 wt % or less of nitrogen (N);   an amount greater than 0 wt % and of about 0.001 wt % or less of oxygen (O);   one or more selected from the group consisting of: an amount of about 0.5 to 1.00 wt % of manganese (Mn), an amount of about 0.1 to 0.6 wt % of nickel (Ni), an amount of about 1.4 to 1.55 wt % of chromium (Cr), an amount of about 0.2 to 0.5 wt % of molybdenum (Mo), and an amount greater than 0 wt % and of about 0.4 wt % or less of vanadium (V); and   iron (Fe) constituting the balance of the weight of the steel composition,   all wt % based on the total weight of the steel composition.   
     
     
         10 . A method of manufacturing a bearing steel, the method comprising:
 manufacturing a wire rod comprising an alloy steel composition;   heat-treating the wire rod for primary spheroidizing;   wire drawing the heat-treated wire rod;   secondary heat-treating the wire-drawn wire rod for secondary spheroidizing;   forging the secondary heat-treated wire rod;   quenching the forged wire rod; and   tempering the quenched wire rod,   wherein the alloy steel composition comprises: an amount of about 0.08 to 1.0 wt % of carbon (C); an amount of about 0.9 to 1.6 wt % of silicon (Si); an amount greater than 0 wt % and of about 0.03 wt % or less of phosphorus (P); an amount greater than 0 wt % and of about 0.01 wt % or less of sulfur (S); an amount of about 0.01 to 0.1 wt % of copper (Cu); an amount of about 0.01 to 0.06 wt % of aluminum (Al); an amount greater than 0 wt % and of about 0.006 wt % or less of nitrogen (N); an amount greater than 0 wt % and of about 0.001 wt % or less of oxygen (O); and iron (Fe) constituting the balance of the weight of the steel composition, all wt % based on the total weight of the alloy steel composition.   
     
     
         11 . The method of  claim 10 , wherein the alloy steel composition further comprises one or more selected from the group consisting of: an amount of about 0.5 to 1.00 wt % of manganese (Mn), an amount of about 0.1 to 0.6 wt % of nickel (Ni), an amount of about 1.4 to 1.55 wt % of chromium (Cr), an amount of about 0.2 to 0.5 wt % of molybdenum (Mo), and an amount greater than 0 wt % and of about 0.4 wt % or less of vanadium (V), all wt % based on the total weight of the alloy steel composition. 
     
     
         12 . The method of  claim 10 , wherein the heat-treating for the primary spheroidizing is performed at a temperature of about 720 to 850° C. for about 4 to 8 hours. 
     
     
         13 . The method of  claim 10 , wherein the secondary heat-treating for the secondary spheroidizing is performed at a temperature of about 720 to 850° C. for about 4 to 8 hours. 
     
     
         14 . The method of  claim 10 , wherein the quenching is performed at a temperature of about 840 to 860° C. for about 0.5 to 2 hours. 
     
     
         15 . The method of  claim 10 , wherein the tempering is performed at a temperature of about 150 to 190° C. for about 0.5 to 2 hours. 
     
     
         16 . The method of  claim 10 , wherein the bearing steel contains a complex carbide. 
     
     
         17 . The method of  claim 16 , wherein the complex carbide comprises one or more selected from the group consisting of M 3 C, M 7 C 3 , and M 23 C 6  carbides, and MC carbides, wherein M is a metal or a transition metal. 
     
     
         18 . The method of  claim 16 , 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) and the M of the MC carbide is one or more selected from the group consisting of vanadium (V) and molybdenum (Mo). 
     
     
         19 . A vehicle part that comprises a steel composition of  claim 1 . 
     
     
         20 . The vehicle part of  claim 19 , wherein the vehicle part is a bearing of an engine or a transmission.