Abstract: A method of manufacturing high strength steel wire for cold forging containing 0.15-0.40 wt % of C, less than 1.5 wt % of Si, 0.30-2.0 wt % of Mn, less than 0.03 wt % of P, and less than 0.03 wt % of S. After initial cold-drawing, the wire rod is heated in a series of high frequency induction heating devices over the Ac3 transformation point for 30-90 seconds. The wire rod is then rapidly cooled and tempered at a temperature of from 500° C. to the A1 transformation point for 30-90 seconds. The wire rod is then cooled to achieve a tensile strength of 1,100-1, 400 MPa. The wire rod is then cold-drawn at an area reduction rate in excess of 25% and up to 40% to yield a tensile strength of 1,200-1,600 MPa, with improved service life of the mold.

Abstract: The present invention relates to a pre-heat treatment steel wire with high strength for a cold forging which is used as a material for an engine, chassy and parts (bolts and shafts) of a steering device. The method includes: cold drawing of a wire rod containing 0.15-0.40 wt % of C, less than 1.5 wt % of Si, 0.30-2.0 wt % of Mn, less than 0.03 wt % of P, less than 0.03 wt % of S and the remainder including Fe and unavoidable impurities; rapidly heating the cold drawn wire rod in a series of high frequency induction heating devices over Ac3 transformation point for 30-90 seconds and maintaining such a heated state; rapidly cooling the wire rod in the heated state by water or oil; executing a tempering process by heating the wire rod to 500° C.

Abstract: Disclosed is a steel wire for cold forging, which has excellent low temperature impact properties, and a method of producing the same. The steel wire consists of 0.10-0.40 wt % C, 1.0 wt % or less of Si, 0.30 - 2.0 wt % Mn, 0.03 wt % or less of P, 0.03 wt % or less of S, and the balance of Fe and impurities. The steel wire has an austenite grain size of 5-20 ?m, impact absorption energy of 60 J/cm2 or more at ?40° C., and tensile strength of 70-130 kgf/mm2. A steel material for cold forming according present invention has impact toughness that is greatly superior to a conventional spheroidized material or non-heat treated steel at a low temperature of ?40° C.

Abstract: Steel wires and steel rods with excellent cold forging properties and used in a manufacture of various machine components, which have relatively high strengths, are disclosed. The steel wires are produced by maintaining a product (n×YS) of a yield strength (YS) and a work hardening coefficient (n) obtained by a tensile test of the steel wire within a range of 4.0-11.0 kgf/mm2, without a need of additional quenching and tempering treatments after cold forging. There is no need to perform heating for spheroidizing annealing for a long time, and it is possible to produce quenched and tempered steel wires having excellent cold forging properties by quenching and tempering treatments in a short period of time.

Abstract: Steel wires and steel rods with excellent cold forging properties and used in a manufacture of various machine components, which have relatively high strengths, are disclosed. The steel wires are produced by maintaining a product (n×YS) of a yield strength (YS) and a work hardening coefficient (n) obtained by a tensile test of the steel wire within a range of 4.0-11.0 kgf/2, without a need of additional quenching and tempering treatments after cold forging. There is no need to perform heating for spheroidizing annealing for a long time, and it is possible to produce quenched and tempered steel wires having excellent cold forging properties by quenching and tempering treatments in a short period of time.