Patent ID: 11859259
Assignee: NIPPON STEEL CORPORATION
Field: Materials, metallurgy (Chemistry)
Classification: CPC C  B | IPC B  C

Claim 13:
14. A manufacturing method of the zinc-plated steel sheet according to claim 2, the method comprising:
sequentially carrying out each of (I) to (IV) on the base steel sheet having said chemical composition:
(I) annealing the base steel sheet to form an annealed steel sheet under conditions of a heating temperature: an Ac3 point to 950° C. and a retention time in a temperature range of the Ac3 point to 950° C.: 1 to 500 s and maintaining a concentration of hydrogen in a furnace at 1.0 to 15.0 vol % at all times from when a base steel sheet temperature reaches 600° C. until when retention of the base steel sheet in the temperature range of the Ac3 point to 950° C. ends;
(II) retaining the annealed steel sheet in a temperature range of an Ms point to 600° C. for 20 to 500 s and maintaining the concentration of hydrogen in the furnace at 1.0 to 10.0 vol % at all times during the retention of the annealed steel sheet;
(III) immersing the annealed steel sheet in a hot-dip galvanizing bath to form a plated steel sheet, and then cooling the plated steel sheet until the plated steel sheet temperature reaches a temperature range of the Ms point −150° C. to the Ms point −30° C.; and
(IV) retaining the plated steel sheet in an atmosphere having a concentration of hydrogen of less than 0.50 vol % in a temperature range of 330° C. to 430° C. for 50 to 1000 s and then coiling the plated steel sheet in a coil shape thereby forming the zinc-plated steel sheet.