High-carbon steel wire rod of high ductility

Abstract

A high-carbon steel wire rod of high ductility for steel cord and the like is provided that experiences little breakage during drawing. The high-carbon steel wire rod of high ductility is a high-carbon steel wire rod fabricated by hot rolling that that has a carbon content of 0.7 mass % or greater, wherein 95% or greater of the wire rod metallographic structure is pearlite structure and the maximum pearlite block size of pearlite at the core of the hot-rolled wire rod is 65 μm or less. The high-carbon steel wire rod of high ductility has a tensile strength in a range of {248+980×(C mass %)}±40 MPa} and a reduction of area of {72.8−40×(C mass %) %} or greater. The high-carbon steel wire rod of high ductility is characterized in that the average pearlite block size at the core of the hot-rolled wire rod constituted by ferrite grain boundaries of an orientation difference of 9 degrees or greater as measured with an EBSP analyzer is 10 μm or greater and 30 μm or less.

1 - 6 . (canceled) 
     
     
         7 . A method of production of a high-carbon steel wire rod of high ductility, comprising the steps of: preparing steel comprised of, by mass %,
 C: 0.7 to 1.1%,   Si: 0.1 to 1.0%,   Mn: 0.1 to 1.0%,   P: 0.02% or less,   S: 0.02% or less,   O: 18 to 30 ppm, and   N: 0 to 40 ppm,   with a balance of Fe and unavoidable impurities, conducting a hot rolling the steel at a hot finish temperature of 800° C. or greater and 1050° C. or less,   carrying out coiling the hot rolled steel at 800° C. to 830° C. within 10 seconds,   conducting Stelmor cooling or direct patenting the coiled steel by immersion in 500 to 570° C. molten salt,   wherein 95% or greater of the wire rod metallographic structure is pearlite structure,   maximum pearlite block size at a core of a cross-section perpendicular to the wire rod axis is 65 μm or less,   a tensile strength in the range of {248+980×(C mass %)}±40 MPa} and   a reduction of area of the wire rod of {72.8−40×(C mass %) %} or greater.   
     
     
         8 . A method of production of a high-carbon steel wire rod of high ductility according to  claim 7 , wherein the wire rod further comprises, in mass %, one or more of
 Cr: 0.05 to 1.0%   Mo: 0.05 to 1.0%,   Cu: 0.05 to 1.0%,   Ni: 0.05 to 1.0%,   Ti: 0.005 to 0.1%, and   B: 0.0005 to 0.006%.   
     
     
         9 . A method of production of a high-carbon steel wire rod of high ductility according to  claim 7  or  8 , wherein an average pearlite block size at the core of the cross-section perpendicular to the wire rod axis is 10 μm or greater and 30 μm or less. 
     
     
         10 . A method of production of a high-carbon steel wire rod of high ductility according to  claim 7  or  8 , wherein the wire rod metallographic structure includes pro-euctoid ferrite at a volume percentage of 2% or less.