Patent ID: 11827950

Abstract:
Provided is a method of manufacturing a high strength steel sheet having excellent workability, including: reheating a steel slab; hot-rolling the reheated steel slab at an Ar3 transformation point or higher; coiling in a temperature range of 400 to 700° C.; primary cooling at a cooling rate of 0.1° C./s or less to room temperature; producing a cold rolled steel sheet at a cold reduction ratio of 40 to 70%; continuously annealing the cold rolled steel sheet in a temperature range of Ac1+30° C. to Ac3−20° C.; secondary cooling at a cooling rate of 10° C./s or less to 630 to 670° C.; third cooling to 400 to 500° C. at a cooling rate of 5° C./s or more in a hydrogen; maintaining for 70 seconds or more; hot-dip galvanizing; and performing a final cooling to Ms or less at a cooling rate of 1° C./s or more.