Carburized steel and method of manufacturing the same

Abstract

A carburized steel composition of the present invention comprises: silicon (Si) in an amount of about 0.7 to 1.3 wt %, nickel (Ni) in an amount of about 0.15 to 0.5 wt %, chromium (Cr) in an amount of about 2.0 to 2.8 wt %, molybdenum (Mo) in an amount of about 0.15 to 0.5 wt %, vanadium (V) in an amount of about 0.02 to 0.1 wt % and nitrogen (N) in an amount of about 0.01 to 0.02 wt %, and iron (Fe) constituting the remaining balance of the carburized steel composition, all the wt % based on the total weight of the carburized steel composition.

What is claimed is: 
     
         1 . A carburized steel composition, comprising:
 silicon (Si) in an amount of about 0.7 to 1.3 wt %;   nickel (Ni) in an amount of about 0.15 to 0.5 wt %;   chromium (Cr) in an amount of about 2.0 to 2.8 wt %;   molybdenum (Mo) in an amount of about 0.15 to 0.5 wt %;   vanadium (V) in an amount of about 0.02 to 0.1 wt %;   nitrogen (N) in an amount of about 0.01 to 0.02 wt %; and   iron (Fe) constituting remaining balance of the carburized steel composition,   all the wt % based on the total weight of the carburized steel composition.   
     
     
         2 . The carburized steel composition of  claim 1 , wherein for the carburized steel composition, the following Formula 1 has a value of about 12.5 to 14 from the contents of Si, Ni, Cr, Mo, V and N:
   (⅝*(1+log√[Si]))*(log([Ni])+10))+2*(1+log([Cr]))+√([Mo])*5+√([V])*3+√([N])*100  Formula 1=
   wherein in the Formula 1, [Si], [Ni], [Cr], [Mo], [V] and [N] refer to the contents (wt %) of Si, Ni, Cr, Mo, V and N, respectively.   
     
     
         3 . The carburized steel composition of  claim 1 , further comprising:
 carbon (C) in an amount of about 0.15 to 0.25 wt %;   manganese (Mn) in an amount of about 0.3 to 1.0 wt %;   phosphorous (P) in an amount of about 0.03 wt % or less but greater than 0 wt %;   sulfur (S) in an amount of about 0.03 wt % or less but greater than 0 wt %;   copper (Cu) in an amount of about 0.3 wt % or less but greater than 0 wt %;   niobium (Nb) in an amount of about 0.01 to 0.05 wt %, and   aluminum (Al) in an amount of about 0.01 to 0.05 wt %,   all the wt % based on the total weight of the carburized steel composition.   
     
     
         4 . The carburized steel composition of  claim 1 , consisting essentially of:
 silicon (Si) in an amount of about 0.7 to 1.3 wt %;   nickel (Ni) in an amount of about 0.15 to 0.5 wt %;   chromium (Cr) in an amount of about 2.0 to 2.8 wt %;   molybdenum (Mo) in an amount of about 0.15 to 0.5 wt %;   vanadium (V) in an amount of about 0.02 to 0.1 wt %;   nitrogen (N) in an amount of about 0.01 to 0.02 wt %; and   iron (Fe) constituting remaining balance of the carburized steel composition,   all the wt % based on the total weight of the carburized steel composition.   
     
     
         5 . The carburized steel composition of  claim 1 , consisting essentially of:
 silicon (Si) in an amount of about 0.7 to 1.3 wt %;   nickel (Ni) in an amount of about 0.15 to 0.5 wt %;   chromium (Cr) in an amount of about 2.0 to 2.8 wt %;   molybdenum (Mo) in an amount of about 0.15 to 0.5 wt %;   vanadium (V) in an amount of about 0.02 to 0.1 wt %;   nitrogen (N) in an amount of about 0.01 to 0.02 wt %;   carbon (C) in an amount of about 0.15 to 0.25 wt %;   manganese (Mn) in an amount of about 0.3 to 1.0 wt %;   phosphorous (P) in an amount of about 0.03 wt % or less but greater than 0 wt %,   sulfur (S) in an amount of about 0.03 wt % or less but greater than 0 wt %;   copper (Cu) in an amount of about 0.3 wt % or less but greater than 0 wt %;   niobium (Nb) in an amount of about 0.01 to 0.05 wt %,   aluminum (Al) in an amount of about 0.01 to 0.05 wt %, and   iron (Fe) constituting remaining balance of the carburized steel composition,   all the wt % based on the total weight of the carburized steel composition.   
     
     
         6 . A method of manufacturing a carburized steel, comprising:
 carburizing a steel material comprising silicon (Si) in an amount of about 0.7 to 1.3 wt %, nickel (Ni) in an amount of about 0.15 to 0.5 wt %, chromium (Cr) in an amount of about 2.0 to 2.8 wt %, molybdenum (Mo) in an amount of about 0.15 to 0.5 wt %, vanadium (V) in an amount of about 0.02 to 0.1 wt % and nitrogen (N) in an amount of about 0.01 to 0.02 wt %, and iron (Fe) constituting remaining balance of the carburized steel composition, all the wt % based on the total weight of the steel material,   wherein the carburizing is carried out at a heat treatment temperature of about 930 to 1050° C.   
     
     
         7 . The method of  claim 6 , wherein for the steel material, the following Formula 1 has a value of about 12.5 to 14 from the contents of Si, Ni, Cr, Mo, V, N:
   (⅝*(1+log√[Si]))*(log([Ni])+10))+2*(1+log([Cr]))+√([Mo])*5+√([V])*3+√([N])*100  Formula 1=
   wherein in the Formula 1, [Si], [Ni], [Cr], [Mo], [V] and [N] refer to the contents (wt %) of Si, Ni, Cr, Mo, V and N, respectively.   
     
     
         8 . The method of  claim 6 , wherein a carbon potential (CP) in the carburizing is of about 0.85 to 1.1. 
     
     
         9 . The method of  claim 6 , wherein the steel material further comprises: carbon (C) in an amount of about 0.15 to 0.25 wt %, manganese (Mn) in an amount of about 0.3 to 1.0 wt %, phosphorous (P) in an amount of about 0.03 wt % or less but greater than 0 wt %, sulfur (S) in an amount of about 0.03 wt % or less but greater than 0 wt %, cupper (Cu) in an amount of about 0.3 wt % or less but greater than 0 wt %, niobium (Nb) in an amount of about 0.01 to 0.05 wt %, and aluminum (Al) in an amount of about 0.01 to 0.05 wt %, all the wt % based on the total weight of the steel material. 
     
     
         10 . The method of  claim 6 , further comprising:
 nitriding the steel materials, after the carburizing.   
     
     
         11 . The method of  claim 10 , wherein the nitriding is carried out at a temperature in a range of about 820 to 870° C. under an atmosphere containing ammonia gas (NH 3 ) in an amount of about 0.5 to 2 vol %. 
     
     
         12 . The method of  claim 11 , wherein the steel material is manufactured into a predetermined gear shape by any one or more of forging, normalizing, annealing and processing. 
     
     
         13 . A vehicle part comprising a carburized steel composition of  claim 1 . 
     
     
         14 . The vehicle part of  claim 13  is a gear. 
     
     
         15 . A vehicle comprising a vehicle part of  claim 13 .