Manufacturing equipment for galvanized steel sheet, and manufacturing method of galvanized steel sheet
AssigneeNippon Steel & Sumitomo Metal Corporation
InventorsNobuyoshi Okada, Masanori Hoshino, Atsushi Sakatoku
Life of this patent
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Abstract
A manufacturing equipment for galvanized steel sheet includes coating tub to coat steel sheet dipped in coating bath wherein the bath including molten zinc and Al is stored at bath temperature T1, separating tub to separate by a flotation top-dross by precipitating the top-dross in the bath wherein the bath transferred from the coating tub is stored at bath temperature T2 lower than T1, adjusting tub to dissolve dross wherein the bath transferred from the separating tub is stored at bath temperature T3 higher than T2 and Fe of the bath is unsaturated, and circulator to circulate the bath in order of the coating tub, the separating tub, and the adjusting tub.
Claims6
A manufacturing method of a galvanized steel sheet, the manufacturing method comprising:
- circulating a coating bath which is a molten metal including a molten zinc and a molten aluminum in order of a coating tub, a separating tub, and an adjusting tub;
- coating a steel sheet which is dipped in the coating bath at the coating tub in which the coating bath transferred from the adjusting tub is stored at a predetermined bath temperature T1;
- separating by a flotation a top-dross which is precipitated at the separating tub in which the coating bath transferred from the coating tub to the separating tub is stored at a bath temperature T2 which is lower than the bath temperature T1 of the coating tub;
- dissolving a residual dross at the adjusting tub in which the coating bath transferred from a lower part of the separating tub is stored at a bath temperature T3 which is higher than the bath temperature T2 of the separating tub;
- and
- decreasing a temperature of the coating bath of the separating tub to a temperature lower than a temperature of the coating bath of the coating tub, thereby preventing a formation of bottom-dross, and removing top-dross separated by the flotation,
- wherein an aluminum concentration in the coating bath of the separating tub is more than 0.14% by mass,
- wherein an aluminum concentration in the coating bath of the coating tub is 0.15% to 0.25% by mass, and
- wherein a first zinc-included-metal which includes an aluminum with a concentration higher than the aluminum concentration of the coating bath in the coating tub is supplied to the adjusting tub and is not supplied to the separating tub.
Dependencies are inferred from the claim text.