STEEL WIRE ROD HAVING EXCELLENT COLD FORGEABILITY AFTER LOW TEMPERATURE ANNEALING AND METHOD FOR PRODUCING THE SAME, AND METHOD FOR PRODUCING STEEL WIRE ROD HAVING EXCELLENT COLD FORGEABILITY

摘要

PROBLEM TO BE SOLVED: To provide a steel wire rod which allows the temperature of annealing for softening before cold forging to be reduced, and achieves excellent cold forgeability after annealing, and to provide a method for producing the same.;SOLUTION: The steel wire rod has a composition comprising, by mass, 0.005 to 0.60% C, 0.01 to 0.40% Si, 0.20 to 1.80% M, ≤0.040% P, ≤0.050% S and 0.0005 to 0.0300% N, and the balance Fe with inevitable impurities, and has a metallic structure composed of a pro-eutectoid ferrite structure, a pearlitic structure and a bainitic structure, wherein the volume ratio of the pearlitic structure is 1.40×C(%)×100% or more, the volume ratio of the pro-eutectoid ferrite is (1-1.25×(C%))×50% or less (including 0%), and the volume ratio of the bainitic structure is ≤20% or less (including 0%), and the steel wire rod has a tensile strength of 340+920×Ceq. MPa or more.;COPYRIGHT: (C)2010,JPO&INPIT