Drawn steel wire

Abstract

A drawn steel wire has a predetermined chemical composition; in a region of the drawn steel wire that is closer to an axis line than a depth of 100 μm from a surface of the drawn steel wire in a lengthwise-section that includes the axis line of the drawn steel wire, a metallographic structure includes 90% or more of a drawn pearlite by an area ratio; in a region of the drawn steel wire that is the depth of 100 μm from the surface of the drawn steel wire in the lengthwise-section, the metallographic structure includes 70% or more of the drawn pearlite by the area ratio; when D in units of millimeters represents a diameter of the drawn steel wire, σHV represents a standard deviation of a Vickers hardness of the surface of the drawn steel wire, and Rp0.2 represents a yield strength of the drawn steel wire, σHV<(−9500×ln(D)+30000) exp(−0.003×Rp0.2) is satisfied, and a tensile strength TS of the drawn steel wire is 1770 MPa or higher.

1 . A drawn steel wire comprising, as a chemical composition, by mass %:
 C: 0.75% to 1.10%,   Si: 0.10% to 1.40%,   Mn: 0.10% to 1.0%,   Al: 0% to 0.10%,   Ti: 0% to 0.10%,   Cr: 0% to 0.60%,   V: 0% to 0.10%,   Nb: 0% to 0.10%,   Mo: 0% to 0.20%,   W: 0% to 0.50%,   B: 0% to 0.0030%,   N: limited to 0.0060% or less,   P: limited to 0.030% or less,   S: limited to 0.030% or less, and   a remainder including Fe and impurities; wherein   in a region of the drawn steel wire that is closer to an axis line than a depth of 100 μm from a surface of the drawn steel wire in a lengthwise-section that includes the axis line of the drawn steel wire, a metallographic structure includes 90% or more of a drawn pearlite by an area ratio;   in a region of the drawn steel wire that is the depth of 100 μm from the surface of the drawn steel wire in the lengthwise-section, the metallographic structure includes 70% or more of the drawn pearlite by the area ratio;   when D in units of millimeters represents a diameter of the drawn steel wire, Gm/represents a standard deviation of a Vickers hardness of the surface of the drawn steel wire, and Rp 0.2  represents a yield strength of the drawn steel wire, Expression (1) is satisfied; and   a tensile strength of the drawn steel wire is 1770 MPa or higher.
   σ HV <(−9500 ×ln ( D )+30000)×exp(−0.003 ×Rp   0.2 )   (1)
 
   
     
     
         2 . The drawn steel wire according to  claim 1 , wherein the chemical composition includes, by mass %, at least one selected from the group consisting of
 Al: 0.001% to 0.10%,   Ti: 0.001% to 0.10%,   Cr: more than 0% and 0.60% or less,   V: more than 0% and 0.10% or less,   Nb: more than 0% and 0.10% or less,   Mo: more than 0% and 0.20% or less,   W: more than 0% and 0.50% or less, and   B: more than 0% and 0.0030% or less.   
     
     
         3 . The drawn steel wire according to  claim 1 , wherein a coating layer including one or more of Zn, Al, Cu, Sn, Mg, and Si on the surface of the drawn steel wire is provided. 
     
     
         4 . The drawn steel wire according to  claim 2 , wherein a coating layer including one or more of Zn, Al, Cu, Sn, Mg, and Si on the surface of the drawn steel wire is provided.