Bearing pressure-resistant member and process for making the same

Abstract

A bearing pressure-resistant member, including a matrix and a carbide dispersed in the matrix, the carbide having an average particle size of not more than 0.3 μm. A carbon (C) content in an outer surface of the bearing pressure-resistant member is in a range of 0.6 to 1.5 mass percent. A process for making the bearing pressure-resistant member including subjecting a workpiece containing C to either of gas carburizing and gas carbonitriding to enhance the C content in the outer surface of the workpiece to 0.6 to 1.5 mass percent, holding the workpiece at a first temperature not more than an Ac 1 transformation point under reduced pressure, heating the workpiece to a second temperature not less than the Ac 1 transformation point under reduced pressure, followed by holding the workpiece at the second temperature, and subjecting the workpiece to quenching.

1 - 7 . (Canceled)  
     
     
         8 . A process for making a bearing pressure-resistant member, comprising: 
 subjecting a workpiece containing C to either of gas carburizing and gas carbonitriding to enhance a C content in an outer surface of the workpiece to 0.6 to 1.5 mass percent;    holding the workpiece at a first temperature not more than an Ac 1  transformation point under reduced pressure;    heating the workpiece to a second temperature not less than the Ac 1  transformation point under reduced pressure, followed by holding the workpiece at the second temperature; and    subjecting the workpiece to quenching.    
     
     
         9 . The process as claimed in  claim 8 , wherein the workpiece is made of a mechanical structural steel containing Cr in an amount ranging from 1.2 to 3.2 mass percent and Mo in an amount ranging from 0.25 to 2.0 mass percent, the first temperature is in a range of 600° C. to 750° C. which is reached by heating the workpiece at a rate of 0.2° C. to 30° C. per minute in a temperature range of 500° C. to 650° C., and the second temperature is in a range not less than the Ac 1  transformation point but not more than a predetermined temperature T represented by the following formula:  
         T(° C.)=675+120.Si(%)−27.Ni(%)+30.Cr(%)+215.Mo(%)−400V (%).  
     
     
         10 . The process as claimed in  claim 9 , wherein the rate of heating the workpiece in the temperature range of 500° C. to 650° C. is in a range of 0.2° C. to 5° C. per minute.  
     
     
         11 . A process for making a bearing pressure-resistant member, comprising: 
 heating a workpiece made of a mechanical structural steel containing C in an amount ranging from 0.6 to 1.5 mass percent, to a first temperature of 600° C. to 750° C. wherein the workpiece is heated at a rate of 0.2° C. to 30° C. per minute in a temperature range of 500° C. to 650° C.;    holding the workpiece at the first temperature;    heating the workpiece to a second temperature not less than an Ac 1  transformation point and not more than an Acm transformation point, followed by holding the workpiece at the second temperature; and    subjecting the workpiece to quenching.    
     
     
         12 . The process as claimed in  claim 11 , further comprising subjecting the workpiece to either of carburizing and carbonitriding to enhance the C content in an outer surface of the workpiece to 0.6 to 1.5 mass percent before heating the workpiece to the first temperature.  
     
     
         13 . The process as claimed in  claim 11 , wherein the rate of heating the workpiece in the temperature range of 500° C. to 650° C. is in a range of 0.2° C. to 5° C. per minute.  
     
     
         14 . A process for making a bearing pressure-resistant member, comprising: 
 heating a workpiece made of a mechanical structural steel containing C in an amount ranging from 0.6 to 1.5 mass percent, Cr in an amount ranging from 1.2 to 3.2 mass percent, and Mo in an amount ranging from 0.25 to 2.0 mass percent, to a first temperature of 600° C. to 750° C. under reduced pressure wherein the workpiece is heated at a rate of 0.2° C. to 30° C. per minute in a temperature range of 500° C. to 650° C. under reduced pressure;    holding the workpiece at the first temperature;    heating the workpiece to a second temperature not less than an Ac 1  transformation point and not more than a predetermined temperature T represented by the following formula:      T(° C.)=675+120.Si(%)−27.Ni(%)+30.Cr(%)+215.Mo(%)−400V(%);    holding the workpiece at the second temperature; and    subjecting the workpiece to quenching.    
     
     
         15 . The process as claimed in  claim 14 , further comprising subjecting the workpiece to either of carburizing and carbonitriding to enhance the C content in an outer surface of the workpiece to 0.6 to 1.5 mass percent before heating the workpiece to the first temperature.  
     
     
         16 . The process as claimed in  claim 14 , wherein the rate of heating the workpiece in the temperature range of 500° C. to 650° C. is in a range of 0.2° C. to 5° C. per minute.