EXCELLENT COLD-WORKABILITY EXHIBITING HIGH-STRENGTH STEEL, WIRE OR STEEL BAR OR HIGH-STRENGTH SHAPED ARTICLE, AND PROCESS FOR PRODUCING THEM

摘要

There are provided an excellent cold-workability exhibiting high-strength steel wire or steel bar, or high-strength shaped article and a process for producing them. In particular, there is provided a process comprising carrying out hot working at 350 to 800° C. of a steel ingot, cast slab, steel slab or steel semifinished product having a C content of not greater than the solid solution limit of carbon of ferrite phase at Ae₁ point and not greater than 0.010 mass % and being free of any cementite, or having a C content of 0.01 to 0.45 mass % to thereby obtain a material whose average crystal grain diameter in a cross section perpendicular to the longitudinal direction is ≦3 μm, and thereafter carrying out cold working of the material to thereby attain formation of a ferrite structure whose average crystal grain diameter in a cross section perpendicular to the longitudinal direction is ≦500 nm.