High-strength wire rod for cold heading with superior heat treatment characteristics and resistance of hydrogen-delayed fracture characteristics, heat-treated component, and method for manufacturing same

Abstract

Disclosed in the present specification are: a high-strength wire rod for cold heading, having superior heat treatment characteristics and resistance of hydrogen-delayed fracture characteristics, the rod being applicable to a bolt, etc.; a heat-treated component; and a method for manufacturing the same. According to an exemplary embodiment, the high-strength wire rod for cold heading with superior heat treatment characteristics and resistance of hydrogen-delayed fracture characteristics comprises, by wt %, 0.3-0.6% of C, 0.05-0.3% of Si, 0.2-1.0% of Mn, 0.5-2.0% of Cr, 0.5-2.0% of Mo, 0.02-0.05% of Al, 0.01-0.03% of N, and Fe and other impurities as the balance, and has a microstructure comprising, by area fraction, 80% or more of bainite, 1-15% of pearlite and 0.1-2% of martensite, and comprises 2×10 19 /m 3 or more of aluminum nitride having a diameter of 5-50 nm.

1 . A high-strength wire rod for cold heading with superior heat treatment characteristics and resistance of hydrogen-delayed fracture characteristics, which comprises, by wt %, 0.3-0.6% of C, 0.05-0.3% of Si, 0.2-1.0% of Mn, 0.5-2.0% of Cr, 0.5-2.0% of Mo, 0.02-0.05% of Al, 0.01-0.03% of N, and Fe and other impurities as the balance, and has a microstructure comprising, by area fraction, 80% or more of bainite, 1-15% of pearlite and 0.1-2% of martensite, and comprises 2×10 19 /m 3  or more of aluminum nitride having a diameter of 5-50 nm. 
     
     
         2 . The high-strength wire rod for cold heading with superior heat treatment characteristics and resistance of hydrogen-delayed fracture characteristics according to  claim 1 , which has a prior austenite average grain size of 10 μm or smaller. 
     
     
         3 . The high-strength wire rod for cold heading with superior heat treatment characteristics and resistance of hydrogen-delayed fracture characteristics according to  claim 1 , wherein the martensite is comprised of 60% or higher in the prior austenite grain boundary. 
     
     
         4 . A method for manufacturing a high-strength wire rod for cold heading with superior heat treatment characteristics and resistance of hydrogen-delayed fracture characteristics, comprising:
 heating a billet comprising, by wt %, 0.3-0.6% of C, 0.05-0.3% of Si, 0.2-1.0% of Mn, 0.5-2.0% of Cr, 0.5-2.0% of Mo, 0.02-0.05% of Al, 0.01-0.03% of N and Fe and other impurities as the balance at 1000-1200° C.,   hot rolling at a finish hot rolling temperature of 750-950° C., and   cooling at a cooling rate of 0.2-1.0° C./s,   wherein the cooled wire rod has a microstructure comprising, by area fraction, 80% or more of bainite, 1-15% of pearlite and 0.1-2% of martensite, and comprises 2×10 19 /m 3  or more of aluminum nitride having a diameter of 5-50 nm.   
     
     
         5 . A heat-treated component with superior heat treatment characteristics and resistance of hydrogen-delayed fracture characteristics, which comprises, by wt %, 0.3-0.6% of C, 0.05-0.3% of Si, 0.2-1.0% of Mn, 0.5-2.0% of Cr, 0.5-2.0% of Mo, 0.02-0.05% of Al, 0.01-0.03% of N and Fe and other impurities as the balance, and has a microstructure comprising, by area fraction, 90% or more of tempered martensite, and comprises 2×10 19 /m 3  or more of aluminum nitride having a diameter of 5-50 nm. 
     
     
         6 . The heat-treated component with superior heat treatment characteristics and resistance of hydrogen-delayed fracture characteristics according to  claim 5 , which has a prior austenite average grain size of 5 μm or smaller. 
     
     
         7 . The heat-treated component with superior heat treatment characteristics and resistance of hydrogen-delayed fracture characteristics according to  claim 5 , which has a tensile strength of 1400 MPa or higher and an impact toughness of 60 J or higher. 
     
     
         8 . A method for manufacturing a heat-treated component with superior heat treatment characteristics and resistance of hydrogen-delayed fracture characteristics, comprising:
 preparing a wire rod comprising, by wt %, 0.3-0.6% of C, 0.05-0.3% of Si, 0.2-1.0% of Mn, 0.5-2.0% of Cr, 0.5-2.0% of Mo, 0.02-0.05% of Al, 0.01-0.03% of N and Fe and other impurities as the balance and having a microstructure comprising, by area fraction, 80% or more of bainite, 1-15% of pearlite and 0.1-2% of martensite, wherein the martensite is comprised of 60% or higher in the prior austenite grain boundary into a steel wire by conducting spheroidization heat treatment and drawing once or more times,   preparing the prepared steel wire into a component by conducting cold heading,   heating the prepared component at 800-900° C. for 1,000-2,000 seconds,   quenching the heated component at 50-150° C., and   tempering the quenched component at 500-600° C. for 3,000-10,000 seconds.