Bearing steel with improved insulation performance

Abstract

A bearing steel has improved insulation performance by forming a continuous insulating film. The bearing steel includes 0.65 to 1.0 mass % of carbon (C), 1.6 to 2.0 mass % of chromium (Cr), 1.5 to 3.0 mass % of aluminum (Al), 0.8 to 1.2 mass % of manganese (Mn), 0.7 to 1.0 mass % of silicon (Si), 0.1 to 0.3 mass % of nickel (Ni), 0.08 to 0.12 mass % of molybdenum (Mo), and a balance of iron (Fe), in which an oxynitride layer including a nitride layer and an oxide layer is formed on the surface of a material.

1 . A bearing steel, comprising:
 a steel comprising 0.65 to 1.0 mass % of carbon (C), 1.6 to 2.0 mass % of chromium (Cr), 1.5 to 3.0 mass % of aluminum (Al), 0.8 to 1.2 mass % of manganese (Mn), 0.7 to 1.0 mass % of silicon (Si), 0.1 to 0.3 mass % of nickel (Ni), 0.08 to 0.12 mass % of molybdenum (Mo), and a balance of iron (Fe); and   an oxynitride layer comprising a nitride layer and an oxide layer formed on a surface of the steel.   
     
     
         2 . The bearing steel of  claim 1 , wherein the steel comprises 0.025 mass % or less of phosphorus (P), 0.02 mass % or less of sulfur (S), 0.01 mass % or less of nitrogen (N), and 0.0020 mass % or less of oxygen (O). 
     
     
         3 . The bearing steel of  claim 1 , wherein the nitride layer is located between the oxide layer and the surface of the steel, and comprises at least one selected from the group consisting of Fe 2 N, Fe 3 N, Fe 4 N, and combinations thereof. 
     
     
         4 . The bearing steel of  claim 1 , wherein the oxide layer is located on an uppermost surface of the bearing steel, and comprises at least one selected from the group consisting of Fe 3 O 4 , Fe 2 O 3 , and combinations thereof. 
     
     
         5 . The bearing steel of  claim 1 , wherein a thickness of the oxynitride layer is 10 to 30 μm. 
     
     
         6 . The bearing steel of  claim 1 , wherein a thickness of the oxide layer is 4 μm or less. 
     
     
         7 . The bearing steel of  claim 1 , wherein the steel is heat-treated at a temperature of 850° C. to 950° C. 
     
     
         8 . The bearing steel of  claim 1 , wherein the steel is configured such that the oxynitride layer is formed on the surface by oxynitriding treatment. 
     
     
         9 . The bearing steel of  claim 1 , wherein the bearing steel has a surface hardness of 650 Hv or more as measured according to ISO 6507-1. 
     
     
         10 . The bearing steel of  claim 1 , wherein the bearing steel has a sheet resistance of 50 Ω·cm 2  or more as measured according to ASTM F1711-96.