Method for manufacturing hot-dip galvanized steel sheet, and equipment for manufacturing hot-dip galvanized steel sheet

Patent metadata

Field	Value
Publication number	US-2025223682-A1
Application number	US-202318848912-A
Country	US
Kind code	A1
Filing date	Jan 27, 2023
Priority date	Apr 18, 2022
Publication date	Jul 10, 2025
Grant date	—

Abstract

It is proposed a method to enable manufacturing of a steel sheet having a beautiful coated layer, when applying hot-dip galvanizing to a steel sheet containing oxidizable elements. The method comprises: an electroplating step of, in a gap between a steel sheet and an electrode plate, forming Fe-based plating on the surface of the steel sheet through electroplating, by supplying an Fe-based plating solution; an annealing step of subjecting the steel sheet to heat treatment; and a hot dip coating step of applying hot-dip galvanizing to the steel sheet, and, in the electroplating step, a plating solution discharge rate, which is the ratio of the flow rate of the plating solution flowing out to the back side that is not facing the steel sheet of the electrode plate, to the flow rate of the plating solution supplied to the steel sheet, is less than 50%.

First claim

1 . A method for manufacturing a hot-dip galvanized steel sheet through:
an electroplating step of, in a gap between a continuously running steel sheet and an electrode plate placed along and opposite the steel sheet, forming Fe-based plating on the surface of the steel sheet through electroplating, by passing current using the electrode plate as an anode and the steel sheet as a cathode while supplying an Fe-based plating solution toward the steel sheet; an annealing step of subjecting the steel sheet after the electroplating step to heat treatment; and a hot dip coating step of applying hot-dip galvanizing to the steel sheet after the annealing step wherein, in the electroplating step, a plating solution discharge rate, which is the ratio of the flow rate of the plating solution flowing out to the back side that is not facing the steel sheet of the electrode plate, to the flow rate of the plating solution supplied to the steel sheet, is less than 50%.

2 . The method for manufacturing a hot-dip galvanized steel sheet according to claim 1 , wherein the plating weight of the Fe-based plating is 2.0 g/m 2 or more.

3 . The method for manufacturing a hot-dip galvanized steel sheet according to claim 1 , wherein the plating solution discharge rate is 10% or less.

4 . The method for manufacturing a hot-dip galvanized steel sheet according to claim 1 , wherein a plating solution flow rate Q (m 3 /min) per one side of the electrode plate satisfies the following formula (1):
Q≥60 WLH  (1),
where W is the width (m) of the steel sheet, L is the length (m) in the longitudinal direction of the electrode plate, and H is the distance (m) between the electrode plate and the steel sheet.

5 . The method for manufacturing a hot-dip galvanized steel sheet according to claim 1 , wherein the steel sheet has a chemical composition containing, in mass %: C: 0.3% or less; and one or more of Si and Mn in total: 1.0% to 6.0%.

6 . Equipment for manufacturing a hot-dip galvanized steel sheet, comprising:
an electroplating device that forms Fe-based plating on a steel sheet running continuously on a running line; an annealing device that subjects the steel sheet that has passed through the electroplating device to heat treatment; and a hot dip coating device that applies hot-dip galvanizing treatment to the steel sheet that has passed through the annealing device, wherein the electroplating device includes: an electrode plate placed along and opposite the running line of the steel sheet; and a jet nozzle that supplies an Fe-based plating solution from the electrode plate side toward the running line, the electrode plate is an anode and the steel sheet is a cathode, and a plating solution discharge rate, which is the ratio of the flow rate of the plating solution flowing out to the back side that is not facing the steel sheet of the electrode plate, to the flow rate of the plating solution supplied from the jet nozzle, is less than 50%.

7 . The equipment for manufacturing a hot-dip galvanized steel sheet according to claim 6 , wherein the electrode plate has at least one through-hole extending in a direction intersecting the running line and penetrating the electrode plate, and the injection nozzle is placed in at least one of the through-hole.

8 . The equipment for manufacturing a hot-dip galvanized steel sheet according to claim 6 , wherein the electroplating device includes a back plate and a jet flow header on the back side of the electrode plate, in this order from the running line side, a plurality of the jet nozzles extending through the back plate and the electrode plate are coupled to the jet flow header, the back plate is connected to the back of the electrode plate via an electrode connecting portion, and an insulating body is placed in a space between the back plate and the electrode plate due to the interposition of the electrode connecting portion.

9 . The equipment for manufacturing a hot-dip galvanized steel sheet according to claim 8 , wherein the electroplating device includes one or more plating cells in which a plurality of the electrode plates are assembled as an aggregation without gaps on one of the back plate.

10 . The equipment for manufacturing a hot-dip galvanized steel sheet according to claim 9 , wherein, in each of the plating cells, the jet flow header is divided into a plurality of pieces at locations that do not interfere with the electrode connecting portion.

11 . The equipment for manufacturing a hot-dip galvanized steel sheet according to claim 8 , wherein the jet flow header has a plating solution pipe that supplies a plating solution into the jet flow header, and the ratio Ak/An of the cross-sectional area Ak of the plating solution pipe to the total cross-sectional area An of jet orifices of the jet nozzles coupled to the jet flow header is 2.5 or more.

12 . The equipment for manufacturing a hot-dip galvanized steel sheet according to claim 6 , wherein the electroplating device and the annealing device are on an identical line.

13 . The equipment for manufacturing a hot-dip galvanized steel sheet according to claim 6 , wherein the electroplating device and the annealing device are on separate lines one another.

Assignees

• Jfe Steel Corp

Inventors

• Takeda Gentaro
• Aoyama Mai
• Takahashi Hideyuki
• Watanabe Maiko

Classifications

• C25D5/50

  by heat-treatment · CPC title

• C25D5/08

  Electroplating with moving electrolyte e.g. jet electroplating {(using locally applied jets of electrolyte C25D5/026)} · CPC title

• C25D7/0685

  Spraying of electrolyte · CPC title

• C25D7/0621

  In horizontal cells · CPC title

• C25D7/0642

  Anodes · CPC title