Cold heading wire for shortening the soft heat treatment time and its manufacturing method

摘要

PROBLEM TO BE SOLVED: To provide a wire rod for cold heading for shortening a soft heat treatment time and a method for manufacturing the same. SOLUTION: The wire rod for cold heading of the present invention has C: 0.15 to 0.5%, Si: 0.02 to 0.4%, Mn: 0.3 to 1.2% in weight%. , Al: 0.02-0.05%, P: 0.03% or less, S: less than 0.01%, N: less than 0.01%, consisting of the remaining Fe and other unavoidable impurities. The internal structure contains a proeutectoid ferrite structure of 20 to 90 area%, a bainite and martensite structure of 5 area% or less, and the remaining pearlite structure, and 80% or more of the equilibrium proeutectoid ferrite fraction has an average particle size of 5 μmm or less. It is a ferrite structure of the above, and the tensile strength of the wire rod is characterized by satisfying the following relational expression 1. [Relational formula 1] TS (MPa) ≧ 279 + 864 * ([C] + [Si] / 8 + [Mn] / 18) [Selection diagram] FIG. 2