WIRE ROD AND BAR STEEL FOR COLD FORGING, EXCELLENT IN CU AGE HARDENABILITY, AND THEIR PRODUCTION

摘要

PROBLEM TO BE SOLVED: To provide a wire rod and a bar steel for cold forging, capable of effectively utilizing Cu age hardenability even if the application of another solid solution heat treatment causing an increase in cost is omitted in the case of a wire rod and a bar steel steel in which cooling velocity after hot rolling cannot be secured sufficiently, and also to provide an effective method for manufacturing such a wire rod and a bar steel for cold forging. ;SOLUTION: This steel is a low carbon steel which has a composition containing, by mass, ≥0.1% Mn, ≤2.0% (not including 0%) Cu, and ≤2.0% (not including 0%) Ni and also has a structure containing ferrite of ≥20 μm ASTM average grain size by ≥50 area%. After rolling is applied to the steel stock having the above chemical composition, the resultant rolled stock is held at ≥800°C for at least 2 sec.;COPYRIGHT: (C)1998,JPO