Patent ID: 8734599

Claim:
A steel wire rod for a high strength and high toughness spring having excellent cold workability, the steel wire rod having a composition comprising: in weight %, C: 0.4 to 0.7%, Si: 1.5 to 3.5%, Mn: 0.3 to 1.0%, Cr: 0.01 to 1.5%, Ni: 0.01 to 1.0%, Cu: 0.01 to 1.0%, B: 0.008 to 0.02%, Al: 0.02 to 0.1%, O: 0.0020% or less, P: 0.02% or less, S: 0.02% or less, N: 0.02% or less, remainder Fe, and other unavoidable impurities, having an internal structure formed of ferrite and pearlite, the internal structure in which prior austenite grain size is 8 μm or less, wherein the steel wire rod has a tensile strength less than 1000 MPa after hot rolling and peeling and shaving the hot rolled steel wire rod without annealing thereof, and wherein the unannealed steel wire rod has an unsoftened structure.