Work hardenable yield ratio control steel and method for manufacturing the same

摘要

A method of preparing a yield ratio control steel according to the present invention includes the steps of: preparing a rod material by rolling or drawing alloy steel including 0.10-0.40 wt% of C, 0.90-1.50 wt% of Mn, 0.50-2.50 wt% of Si, 0-0.060 wt% (exclusive of 0 wt%) of Al, and the remainder consisting of Fe and inevitable impurities; performing primary heat treatment maintained for a predetermined time at a temperature of A_c1 to (A_cl + A_c3)/2 based on the transformation temperatures of A_c1 and A_c3 by heating the material; and performing secondary heat treatment by cooling the material to a temperature of (25°C + Ms)/2 to Ms based on a Martensitic transformation starting point (Ms) and maintaining the temperature for a predetermined time.