Wire rod for steel wire, and steel wire

Abstract

An object of the present invention is to provide a wire rod for a steel wire, which is excellent in low cycle fatigue characteristics and is useful as a material for a high-strength steel wire such as a wire rope or a PC steel wire, and to provide a steel wire that can exhibit such characteristics. A wire rod for a steel wire of the present invention comprises by mass: C: 0.70 to 1.3%; Si: 0.1 to 1.5%; Mn: 0.1 to 1.5%; N: 0.001 to 0.006%; Al: 0.001 to 0.10%; Ti: 0.02 to 0.20%; B: 0.0005 to 0.010%; P: 0% or more and 0.030% or less; and S: 0% or more and 0.030% or less, with the balance being iron and inevitable impurities, wherein, the wire rod has pearlite as a main phase, an area ratio of proeutectoid ferrite is 1.0% or less, and an average thickness of the proeutectoid ferrite is 5 μm or less.

1 . A wire rod, comprising by mass:
 C: 0.70 to 1.3%;   Si: 0.1 to 1.5%;   Mn: 0.1 to 1.5%;   N: 0.001 to 0.006%;   Al: 0.001 to 0.10%;   Ti: 0.02 to 0.20%;   B: 0.0005 to 0.010%;   P: 0% or more and 0.030% or less; and   S: 0% or more and 0.030% or less, with the balance being iron and inevitable impurities, wherein:   the wire rod has pearlite as a main phase,   an area ratio of proeutectoid ferrite is 1.0% or less, and   an average thickness of the proeutectoid ferrite is 5 μm or less.   
     
     
         2 . The wire rod according to  claim 1 , further comprising at least one selected from a group consisting of (a), (b), (c) and (d) below by mass:
 (a) at least one of Cr: more than 0% and 1.0% or less, and V: more than 0% and 0.5% or less;   (b) at least one of Ni: more than 0% and 0.5% or less, and Nb: more than 0% and 0.5% or less;   (c) Co: more than 0% and 1.0% or less; and   (d) at least one of Mo: more than 0% and 0.5% or less, and Cu: more than 0% and 0.5% or less.   
     
     
         3 . The wire rod according to  claim 1 , wherein a content of a solid solution B is 0.0003% by mass or more. 
     
     
         4 . A steel wire that is produced from the wire rod of  claim 1  and that has a 100,000 cycle fatigue strength σ that satisfies a relationship of formula (1) below with tensile strength TS:
   σ>0.45TS  (1).
 
 
     
     
         5 . The wire rod according to  claim 2 , wherein a content of a solid solution B is 0.0003% by mass or more. 
     
     
         6 . A steel wire that is produced from the wire rod of  claim 2  that has a 100,000 cycle fatigue strength σ that satisfies a relationship of formula (1) below with tensile strength TS:
   σ>0.45TS  (1).
 
 
     
     
         7 . The wire rod according to  claim 1 , wherein the mass of Cr is more than 0% and 1.0% or less. 
     
     
         8 . The wire rod according to  claim 1 , wherein the mass of V is more than 0% and 0.5% or less. 
     
     
         9 . The wire rod according to  claim 1 , wherein the mass of Ni is more than 0% and 0.5% or less. 
     
     
         10 . The wire rod according to  claim 1 , wherein the mass of Nb is more than 0% and 0.5% or less. 
     
     
         11 . The wire rod according to  claim 1 , wherein the mass of Co is more than 0% and 1.0% or less. 
     
     
         12 . The wire rod according to  claim 1 , wherein the mass of Mo is more than 0% and 0.5% or less. 
     
     
         13 . The wire rod according to  claim 1 , wherein the mass of Cu is more than 0% and 0.5% or less. 
     
     
         14 . A carbon steel comprising by mass:
 C: 0.70 to 1.3%;   Si: 0.1 to 1.5%;   Mn: 0.1 to 1.5%;   N: 0.001 to 0.006%;   Al: 0.001 to 0.10%;   Ti: 0.02 to 0.20%;   B: 0.0005 to 0.010%;   P: 0% or more and 0.030% or less; and   S: 0% or more and 0.030% or less, with the balance being iron and inevitable impurities;   wherein said carbon steel has pearlite as a main phase and an area ratio of proeutectoid ferrite is 1.0% or less, wherein an average thickness of the proeutectoid ferrite is 5 μm or less.