Carburized component and method of manufacturing the same

Abstract

This invention aims to provide a carburized component realizing a larger strength for power transmission components such as gears, and a method of manufacturing the same. The carburized component of this invention, aimed at realizing the object, consists essentially of, in % by mass and both ends inclusive, C: 0.1-0.30%, Si: 0.80-1.50%, Mn: 0.30-1.20%, Cr: 2.0-5.5%, and the balance of Fe and inevitable impurities; has a mean C concentration over the range from the surface of the steel to a depth of 0.2 mm after vacuum carburization of 1.2% or more and 3.0% or less, and has a ratio of a carbide area over the range from the surface to a depth of 50 μm of 15% or more and 60% or less, has the carbide precipitated in a finely dispersed manner so that the carbide having a grain size of 10 μm or less accounts for 90% or more of the entire portion, and has a depth of a grain boundary oxide layer below the surface of 1 μm or less.

1 . A carburized component consisting essentially of, in % by mass and both ends inclusive, C: 0.1-0.30%, Si: 0.80-1.50%, Mn: 0.30-1.20%, Cr: 2.0-5.5%, and the balance of Fe and inevitable impurities; 
 having a mean C concentration over the range from the surface of the steel to a depth of 0.2 mm after vacuum carburization of 1.2% or more and 3.0% or less, having a ratio of carbide area over the range from the surface to a depth of 50 μm of 15% or more and 60% or less, having the carbide precipitated in a finely dispersed manner so that the carbide having a grain size of 10 μm or less accounts for 90% or more of the entire portion, and having a depth of a grain boundary oxide layer of 1 μm or less.    
   
   
       2 . The carburized component as claimed in  claim 1 , further comprising either or both of Mo: 0.2 to 1.0% and V: 0.2 to 1.0%.  
   
   
       3 . A method of manufacturing a carburized component described in  claim 1 , subjecting steel containing the above-described steel ingredients to a primary carburization at a temperature of Acm or above, then rapidly cooling the steel to as low as point A1 or below, and then subjecting the steel to a secondary carburization at a temperature of point A1 or above and or Acm below.  
   
   
       4 . The method of manufacturing a carburized component as claimed in  claim 3 , wherein the carburization is carried out by vacuum carburization at 1,000 Pa or below.  
   
   
       5 . The method of manufacturing a carburized component as claimed in  claim 3 , further subjecting the steel to peening after the secondary carburization.