STEEL WIRE ROD FOR HARD DRAWN SPRING, DRAWN WIRE ROD FOR HARD DRAWN SPRING AND HARD DRAWN SPRING, AND METHOD FOR PRODUCING HARD DRAWN SPRING

摘要

A steel wire rod for a spring for use in producing a hard drawn spring, which comprises, in mass %, C: 0.5 % or more and less than 0.7 %, Si: 1.4 to 2.5 %, Mn: 0.5 to 1.5 %, Cr: 0.05 to 2.0 % and V: 0.05 to 0.40 %, and has the area rate Rp of a pearlite structure satisfying the following formula (1): Rp (area %) = 55 x [C] + 61 ... (1) wherein [C] represents the content (mass %) of C. A hard drawn spring produced by using the above steel wire rod exhibits the fatigue strength and resistance to setting which are comparable or superior to those of a spring produced through drawing an oil tempered steel wire rod.