Process for producing high-strength, low yield ratio and high ductility dual-phase structure steel sheets

摘要

Process for producing a high strength, low yield ratio and high ductility dual-phase structure steel sheet having a structure composed mainly of a ferrite phase and a rapidly cooled transformation phase and having excellent formability with a tensile strength of 40 kg/mm2 or higher. The process comprises cooling the continuously annealed steel sheet under the following conditions: (1) 1 DEG C./second