Steel wire material and method for manufacturing same

Abstract

The steel wire material of the present invention contains 0.05 to 1.2% of C (mass %; same for the chemical components hereafter), 0.01 to 0.5% of Si, 0.1 to 1.5% of Mn, 0.02% or less (but not 0%) of P, 0.02% or less (but not 0%) of S, and 0.005% or less (but not 0%) of N, with the balance being iron and inevitable impurities. The wire material has a scale layer that is no thicker than 7.0 μm or less. The scale layer has an FeO percentage of 30 to 80 vol % and an Fe 2 SiO 4 percentage of less than 0.1 vol %. The scale layer that is formed will not peel when cooled after hot rolling or during storage and transport, but will easily peel during mechanical descaling.

1 . A steel wire material comprising, by mass % based on the total mass of the steel wire material:
 C: 0.05-1.2%;   Si: 0.01-0.5%;   Mn: 0.1-1.5%;   P: 0.02% or less (not including 0%);   S: 0.02% or less (not including 0%); and   N: 0.005% or less (not including 0%); with the remainder being iron and unavoidable impurities, wherein   a scale with 7.0 μm or less thickness is included,   FeO ratio inside the scale is 30-80 vol %, and   Fe 2 SiO 4  ratio is less than 0.1 vol %.   
     
     
         2 . The steel wire material according to  claim 1 , further comprising, by mass % based on the total mass of the steel wire material, at least one selected from the group of (1) (2), (3), (4), (5), and (6):
 (1) Cr: 0.3% or less (not including 0%) and/or Ni: 0.3% or less (not including 0%);   (2) Cu: 0.2% or less (not including 0%);   (3) At least one element selected from a group consisting of Nb, V, Ti, Hf and Zr by 0.1% or less (not including 0%) in total;   (4) Al: 0.1% or less (not including 0%);   (5) B: 0.005% or less (not including 0%); and   (6) Ca: 0.01% or less (not including 0%) and/or Mg: 0.01% or less (not including 0%).   
     
     
         3 . A method for manufacturing a steel wire material, the method comprising:
 hot rolling steel of the chemical composition according to  claim 1 , to obtain a hot rolled steel;   thereafter winding up the hot rolled steel at 750-880° C., to obtain a wound steel; and   cooling the wound steel while injecting a gas mixture of oxygen and an inert gas whose oxygen fraction is less than 20 vol % or an inert gas.   
     
     
         4 . The method for manufacturing according to  claim 3 , wherein the inert gas is nitrogen.