High-Strength, High-Toughness Steel Wire Rod, and Method for Manufacturing Same

Abstract

Provided are a high-strength, high-toughness steel wire rod and a method of manufacturing the same. The steel wire rod has a composition including 0.07 wt % to 0.14 wt % of aluminum (Al) and nitrogen (N) wherein Al:N (where Al and N denote wt % of each element) is in a range of 15:1 to 25:1. Since a steel wire rod having sufficient strength and toughness improvement effects can be obtained with a simple alloy component, a steel wire rod capable of allowing processing such as cold forging to be performed without an additional heat treatment may be provided.

1 . A high-strength, high-toughness steel wire rod comprising:
 aluminum (Al) in a range of about 0.07 wt % to about 0.14 wt %; and   nitrogen (N),   wherein Al:N (where Al and N denote a wt % of each element) is in a range of about 15:1 to about 25:1.   
     
     
         2 . The high-strength, high-toughness steel wire rod of  claim 1 , wherein a sum of Ti, Nb, and V contents is about 0.01 wt % or less. 
     
     
         3 . The high-strength, high-toughness steel wire rod of  claim 1 , further comprising about 0.15 wt % to about 0.3 wt % of carbon (C), about 0.05 wt % to about 0.15 wt % of silicon(Si), about 1.0 wt % to about 3.0 wt % of manganese (Mn), about 0.02 wt % or less of phosphorous (P), or about 0.02 wt % or less of sulfur (S). 
     
     
         4 . The high-strength, high-toughness steel wire rod of  claim 1 , wherein fine AlN-based nanoprecipitates having a size of about 130 nm or less are formed in the steel wire rod. 
     
     
         5 . The high-strength, high-toughness steel wire rod of  claim 1 , wherein the steel wire rod has a microstructure comprising ferrites having an area fraction of between about 50% and about 70% and pearlites having an area fraction of between about 30% and about 50%. 
     
     
         6 . The high-strength, high-toughness steel wire rod of  claim 1 , wherein the steel wire rod has a tensile strength range of about 600 MPa to about 700 MPa and an elongation range of about 20% to about 30%. 
     
     
         7 . A method of manufacturing a high-strength, high-toughness steel wire rod comprising:
 finishing rolling a steel having a composition of  claim 1  in a temperature range of about 850° C. to about 1050° C.; and   cooling the steel at a cooling rate of about 5° C./s or less.   
     
     
         8 . The method of  claim 7 , wherein the steel further comprises about 0.15 wt % to about 0.3 wt % of C, about 0.05 wt % to about 0.15 wt % of Si, about 1.0 wt % to about 3.0 wt % of Mn, about 0.02 wt % or less of P, or about 0.02 wt % or less of S. 
     
     
         9 . The high-strength, high-toughness steel wire rod of  claim 2 , further comprising about 0.15 wt % to about 0.3 wt % of carbon (C), about 0.05 wt % to about 0.15 wt % of silicon (Si), about 1.0 wt % to about 3.0 wt % of manganese (Mn), about 0.02 wt % or less of phosphorous (P), or about 0.02 wt % or less of sulfur (S). 
     
     
         10 . The high-strength, high-toughness steel wire rod of  claim 2 , wherein fine AlN-based nanoprecipitates having a size of about 130 nm or less are formed in the steel wire rod. 
     
     
         11 . The high-strength, high-toughness steel wire rod of  claim 2 , wherein the steel wire rod has a microstructure comprising ferrites having an area fraction of between about 50% and about 70% and pearlites having an area fraction of between about 30% and about 50%. 
     
     
         12 . The high-strength, high-toughness steel wire rod of  claim 2 , wherein the steel wire rod has a tensile strength range of about 600 MPa to about 700 MPa and an elongation range of about 20% to about 30%. 
     
     
         13 . A method of manufacturing a high-strength, high-toughness steel wire rod comprising:
 finishing rolling a steel having a composition of  claim 2  in a temperature range of about 850° C. to about 1050° C.; and   cooling the steel at a cooling rate of about 5° C./s or less.   
     
     
         14 . The method of  claim 13 , wherein the steel further comprises about 0.15 wt % to about 0.3 wt % of C, about 0.05 wt % to about 0.15 wt % of Si, about 1.0 wt % to about 3.0 wt % of Mn, about 0.02 wt % or less of P, or about 0.02 wt % or less of S.