Raw blank for vacuum carburization and method for producing same

Abstract

A raw blank for vacuum carburization is provided. The raw blank for vacuum carburization has a chemical composition containing, by mass, C: 0.13 to 0.28%, Si: 0.01 to 1.20%, Mn: 0.10 to 1.50%, P: 0.030% or less, S: 0.050% or less, Cr: 0.30 to 2.20%, Al: 0.027 to 0.090%, N: 0.0060 to less than 0.0140%, and, as an optional element, Mo: 0.60% or less, the remainder being Fe and unavoidable impurities, and satisfying the following formula (1). AlN precipitates having an equivalent circle diameter of 100 nm or more exist at 1.5 pieces/100 μm 2 or less in a cross section of the raw blank. Al×N≤0.00090  (1) It is noted that element symbols in the formula (1) denote a value of content (% by mass) of each element.

1 . A raw blank for vacuum carburization, having:
 a chemical composition containing, by mass, C: 0.13 to 0.28%, Si: 0.01 to 1.20%, Mn: 0.10 to 1.50%, P: 0.030% or less, S: 0.050% or less, Cr: 0.30 to 2.20%, Al: 0.027 to 0.090%, N: 0.0060 to less than 0.0140%, and, as an optional element, Mo: 0.60% or less, the remainder being Fe and unavoidable impurities, and satisfying the following formula (1),   wherein AlN precipitates having an equivalent circle diameter of 100 nm or more exist at 1.5 pieces/100 μm 2  or less in a cross section of the raw blank:
   Al×N≤0.00090  (1)
 
   
       wherein element symbols in the formula (1) denote a value of content (% by mass) of each element. 
     
     
         2 . A method for producing the raw blank for vacuum carburization according to  claim 1 , the method comprising:
 heating a steel material having the chemical composition to a temperature of 1100° C. or higher to perform final hot working; and   thereafter cooling the steel material subjected to the final hot working to 900° C. at a cooling rate of 1° C./sec or more.