Patent ID: 9206489
Filing Date: 2015-12-08
Classification: C21D,C22C,Y02P

Abstract:
1. A method of manufacturing a high strength steel wire for cold forging, comprising the steps of: cold-drawing 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; 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; cooling the wire rod in the heated state by water or oil; executing a tempering process by heating the wire rod to 500° C. to the A1 transformation point for 30-90 seconds including a holding time at such a temperature; cooling the heated wire rod by water to achieve a wire rod with a tensile strength of 1,100-1,400 MPa; and cold-drawing the wire rod at an area reduction rate in excess of 25% and up to 40% to yield a tensile strength of 1,200-1,600 MPa.