Method for pickling steel plate and pickling apparatus

Patent metadata

Field	Value
Publication number	US-12091757-B2
Application number	US-202017607781-A
Country	US
Kind code	B2
Filing date	Jan 9, 2020
Priority date	Jan 9, 2020
Publication date	Sep 17, 2024
Grant date	Sep 17, 2024

Abstract

A method for pickling a steel plate having a first steel plate portion and a second steel plate portion which is connected to a tail end of the first steel plate portion and which requires a longer time for pickling than the first steel plate portion when pickled under the same condition includes: a step of pickling the steel plate by immersing the steel plate in an acid solution in at least one pickling tank while conveying the steel plate; a step of circulating the acid solution, through a circulation line connected to any of the at least one pickling tank, between the pickling tank and an oxidizing device disposed in the circulation line; a step of oxidizing Fe2+ in the acid solution to Fe3+ by the oxidizing device using a gaseous oxidant; and a feeding start step of, upon switching from pickling of the first steel plate portion to pickling of the second steel plate portion, starting feeding of a liquid oxidant for oxidizing Fe2+ in the acid solution to Fe3+ to any of the at least one pickling tank or to the circulation line.

First claim

The invention claimed is:

1. A method for pickling a steel plate having a first steel plate portion and a second steel plate portion which is connected to a tail end of the first steel plate portion and which requires a longer time for pickling than the first steel plate portion when pickled under the same condition, comprising:
a step of pickling the steel plate by immersing the steel plate in an acid solution in at least one pickling tank while conveying the steel plate;
a step of circulating the acid solution, through a circulation line connected to any of the at least one pickling tank, between the pickling tank and an oxidizing device disposed in the circulation line;
a step of oxidizing Fe 2+ in the acid solution to Fe 3+ by the oxidizing device using a gaseous oxidant; and
a feeding start step of, upon switching from pickling of the first steel plate portion to pickling of the second steel plate portion, starting feeding of a liquid oxidant for oxidizing Fe 2+ in the acid solution to Fe 3+ to any of the at least one pickling tank or to the circulation line.

2. The method for pickling a steel plate according to claim 1 ,
wherein feeding of the liquid oxidant to the at least one pickling tank or the circulation line is started within a period of time during which a first connection portion being a connection portion connecting the first steel plate portion and the second steel plate portion exists in the at least one pickling tank.

3. The method for pickling a steel plate according to claim 1 , further comprising:
a speed reduction step of, upon switching from pickling of the first steel plate portion to pickling of the second steel plate portion, reducing a conveyance speed of the steel plate.

4. The method for pickling a steel plate according to claim 3 , further comprising:
a step of obtaining information on a position, in a conveyance direction, of a first connection portion being a connection portion connecting the first steel plate portion and the second steel plate portion; and
a step of deciding a timing to reduce the conveyance speed of the steel plate on the basis of the information.

5. The method for pickling a steel plate according to claim 3 , further comprising:
a step of, after the feeding start step and the speed reduction step, increasing the conveyance speed of the steel plate.

6. The method for pickling a steel plate according to claim 1 , further comprising
a step of, upon switching from pickling of the first steel plate portion to pickling of the second steel plate portion, increasing at least one of a supply amount of the gaseous oxidant to the acid solution by the oxidizing device or a circulation flow rate of the acid solution between the oxidizing device and the at least one pickling tank to increase a concentration of Fe 3+ in the acid solution in the pickling tank.

7. The method for pickling a steel plate according to claim 1 , further comprising:
a step of, during pickling of the steel plate in the at least one pickling tank, stopping supply of the liquid oxidant to the at least one pickling tank or the circulation line.

8. The method for pickling a steel plate according to claim 7 ,
wherein the steel plate includes a third steel plate portion which is connected to a tail end of the second steel plate portion and which requires a shorter time to be pickled than the second steel plate portion when pickled under the same condition, and
wherein the method further comprises a step of, upon switching from pickling of the second steel plate portion to pickling of the third steel plate portion, reducing at least one of a supply amount of the gaseous oxidant to the acid solution by the oxidizing device or a circulation flow rate of the acid solution between the oxidizing device and the at least one pickling tank to reduce a concentration of Fe 3+ in the acid solution in the pickling tank.

9. The method for pickling a steel plate according to claim 8 , further comprising:
a step of, upon switching from pickling of the second steel plate portion to pickling of the third steel plate portion, increasing a conveyance speed of the steel plate.

10. The method for pickling a steel plate according to claim 1 ,
wherein the at least one pickling tank includes a plurality of pickling tanks arranged along a conveyance direction of the steel plate,
wherein the method includes a step of transferring the acid solution in the pickling tank positioned at a downstream side in the conveyance direction to the pickling tank positioned at an upstream side in the conveyance direction, and
wherein the feeding start step includes feeding the liquid oxidant to at least one of the plurality of pickling tanks or to the circulation line connected to the at least one of the plurality of pickling tanks.

11. The method for pickling a steel plate according to claim 10 ,
wherein feeding of the liquid oxidant to the plurality of pickling tanks or the circulation line connected to the pickling tanks is started sequentially in an order of passing of a first connection portion being a connection portion connecting the first steel plate portion and the second plate portion.

12. The method for pickling a steel plate according to claim 1 , further comprising:
a step of obtaining information on a position of a first connection portion in the conveyance direction, the first connection portion being a connection portion connecting the first steel plate portion and the second plate portion; and
a step of deciding a timing to start supply of the liquid oxidant on the basis of the information.

13. The method for pickling a steel plate according to claim 1 , further comprising:
a step of detecting a concentration of Fe 3+ in the acid solution in the pickling tank; and
a step of deciding a supply amount of the liquid oxidant on the basis of a difference between the detected concentration of Fe 3+ and a target concentration of Fe 3+ in the acid solution in the pickling tank for pickling of the second steel plate portion.

14. The method for pickling a steel plate according to claim 1 , further comprising:
a step of, during pickling of the second steel plate portion and after stopping supply of the liquid oxidant to the at least one pickling tank or to the circulation line, adjusting at least one of a supply amount of the gaseous oxidant or a circulation flow rate of the acid solution between the oxidizing device and the at least one pickling tank so as to maintain a concentration of Fe 3+ in the acid solution in the pickling tank within a predetermined range including a target concentration of Fe 3+ in the acid solution in the pickling tank for pickling of the second steel plate portion.

15. A pickling apparatus for pickling a steel plate having a first steel plate portion and a second steel plate portion which is connected to a tail end of the first steel plate portion and which requires a longer time for pickling than the first steel plate portion when pickled under the same condition, comprising:
at least one pickling tank storing an acid solution;
a conveyance part configured to convey the steel plate while immersing the steel plate in the acid solution in the at least one pickling tank;
a circulation line for circulating the acid solution inside any of the at least one pickling tank, the circulation line being connected to the at least one pickling tank;
an oxidizing device disposed in the circulation line and configured to oxidize Fe 2+ in the acid solution to Fe 3+ by using a gaseous oxidant; and
a liquid oxidant feeding part capable of feeding a liquid oxidant for oxidizing Fe 2+ in t

Assignees

• Primetals Tech Japan Ltd

Inventors

• Tsuji Kosei
• Nakatsuka Ryusuke
• Yoshikawa Masashi
• Hirata Takuya

Classifications

• C23G3/025

  Details of the apparatus, e.g. linings or sealing means · CPC title

• C23G3/021 Primary

  by dipping · CPC title

• C23G1/088

  solutions containing organic acids · CPC title

• C23G1/085

  solutions containing HNO3 · CPC title

• C23G1/083

  solutions containing H3PO4 · CPC title