Patent ID: 10294542

Abstract:
A method is provided for producing a high-strength galvanized steel sheet having a microstructure that contains martensite in an area proportion of 20% or more and 60% or less and ferrite in an area proportion of 40% or more and 80% or less includes, in sequence, hot-rolling a steel slab containing a specific component composition, performing cold rolling, performing primary annealing, performing pickling, performing secondary annealing, and performing galvanizing treatment, in which in the primary annealing, heating is performed at an average heating rate of 0.1° C./sec. or more and less than 3° C./sec. in the temperature range of 600° C. to 750° C., an annealing temperature of 750° C. to 850° C. is maintained for 10 to 500 seconds, and then cooling is performed from the annealing temperature range to a cooling stop temperature of 600° C. or lower at an average cooling rate of 1 to 15° C./sec, in which in the pickling, the pickling weight loss of the steel sheet is 0.05 to 5 g/m2 in terms of Fe, in which in the secondary annealing, an annealing temperature of 750° C. to 850° C. is maintained for 10 to 500 seconds, and then cooling is performed from the annealing temperature at an average cooling rate of 1 to 15° C./s, and in which after the galvanizing treatment, cooling is performed at an average cooling rate of 5 to 100° C./sec.