High-strength steel wire

Abstract

A high-strength steel wire includes a predetermined chemical composition. In the high-strength steel wire, a metallographic microstructure includes a pearlite structure of not less than 95% by area, an average aspect ratio R of a pearlite block, measured in a surface layer in a cross section in an axial direction including an axis of the steel wire, is 2.0 or more, assuming that a diameter of the steel wire is D, a ratio of an average aspect ratio measured in the surface layer to an average aspect ratio measured at a position of 0.25D is 1.1 or more in the cross section in the axial direction including the axis of the steel wire, and a tensile strength of the steel wire is 1,800 MPa or more.

1 . A high-strength steel wire comprising a chemical composition comprising, in terms of % by mass:
 C: from 0.70 to 1.20%,   Si: from 0.10 to 2.00%,   Mn: from 0.20 to 1.00%,   P: 0.030% or less,   S: 0.030% or less,   N: from 0.0010 to 0.0100%,   Al: from 0 to 0.100%,   Cr: from 0 to 2.00%,   V: from 0 to 0.30%,   B: from 0 to 0.0050%,   Ti: from 0 to 0.050%,   Nb: from 0 to 0.050%,   Zr: from 0 to 0.050%,   Ni: from 0 to 2.00%,   Cu: from 0 to 1.00%,   Sn: from 0 to 0.50%,   Mg: from 0 to 0.010%, and   Ca: from 0 to 0.010%,   the balance being Fe and impurities, wherein:   a metallographic microstructure comprises a pearlite structure having an area ratio of 95% or more,   an average aspect ratio R of a pearlite block, measured in a surface layer in a cross section in an axial direction including an axis of the steel wire, is 2.0 or more,   assuming that a diameter of the steel wire is D, a ratio of an average aspect ratio of pearlite block, measured in the surface layer, to an average aspect ratio of pearlite block, measured at a position of 0.25D, is 1.1 or more in the cross section in the axial direction including the axis of the steel wire, and   a tensile strength of the steel wire is 1,800 MPa or more.   
     
     
         2 . The high-strength steel wire according to  claim 1 ,
 wherein the chemical composition comprises, in terms of % by mass, one or more of:   Al: from 0.005 to 0.100%,   Cr: from 0.01 to 2.00%,   V: from 0.01 to 0.30%,   B: from 0.0001 to 0.0050%,   Ti: from 0.001 to 0.050%,   Nb: from 0.001 to 0.050%,   Zr: from 0.001 to 0.050%, or   Ni: from 0.01 to 2.00%.   
     
     
         3 . The high-strength steel wire according to  claim 1 , wherein a content of Al in the chemical composition is, in terms of % by mass, from more than 0.005 to 0.100%. 
     
     
         4 . The high-strength steel wire according to  claim 1 , wherein the steel wire has a diameter of from 2.5 mm to 9.5 mm. 
     
     
         5 . The high-strength steel wire according to  claim 2 , wherein a content of Al in the chemical composition is, in terms of % by mass, from more than 0.005 to 0.100%. 
     
     
         6 . The high-strength steel wire according to  claim 2 , wherein the steel wire has a diameter of from 2.5 mm to 9.5 mm. 
     
     
         7 . The high-strength steel wire according to  claim 3 , wherein the steel wire has a diameter of from 2.5 mm to 9.5 mm.