Claims
- 1. A process for pickling stainless steel strip in a continuous fashion comprising the steps of:a. heating a pre-pickling tank, said pre-pickling tank containing an aqueous pre-pickling solution consisting of sulfuric acid and hydrofluoric acid and immersing said strip in said pre-pickling tank; b. immersing said strip in a pickling tank after step a, said pickling tank containing an aqueous pickling solution consisting of sulfuric acid, hydrofluoric acid and stabilized hydrogen peroxide; and c. removing heat from the pickling solution of step b.
- 2. The process of claim 1 wherein a heat exchanger is external to and coupled to said pickling tank, and the heat exchanger is arranged in a re-circulating loop so that at any time, a portion of the aqueous pickling solution from said pickling tank is routed through the heat exchanger and the resulting aqueous solution is deposited back into said pickling tank through at least one inlet located inside said pickling tank.
- 3. The process of claim 1 wherein the concentration of stabilized hydrogen peroxide in said pickling tank is from about 5 g/L to about 50 g/L.
- 4. The process of claim 1 wherein the concentration of stabilized hydrogen peroxide in said pickling tank is from about 5 g/L to less than 10 g/L.
- 5. The process of claim 1 wherein said strip is scrubbed after step a, and prior to immersion in said pickling tank.
- 6. The process of claim 2 wherein said heat exchanger and a filtration device is external to and coupled to the pickling tank.
- 7. The process of claim 5 wherein said strip is immersed in a de-smutting tank prior to being scrubbed, said de-smutting tank containing an aqueous solution consisting of hydrogen peroxide, sulfuric acid and hydrofluoric acid.
- 8. The process of claim 7 wherein the aqueous solution in said pre-pickling tank consists of from about 90 g/l to about 200 g/l sulfuric acid and from about 10 g/l to about 60 g/l hydrofluoric acid.
- 9. The process of claim 7 wherein overview solution from the picking tank is channeled into the de-smutting tank.
- 10. The process of claim 8 wherein the aqueous solution in the pre-pickling tank is maintained at a temperature of from about 54° C. to about 77° C.
- 11. The process of claim 10 wherein the sulfuric acid in the pickling tank has a concentration of from about 20 g/l to about 60 g/l and the hydrofluoric acid in the pickling tank has a concentration of from about 2 g/l to about 50 g/l.
- 12. The process of claim 11 wherein the aqueous solution in the pickling tank is maintained at a temperature of from about 20° C. to about 60° C.
- 13. The process of claim 12 wherein the aqueous solution in the pickling tank is maintained at a temperature of from about 35° C. to about 50° C.
- 14. A process for pickling hot rolled and annealed stainless steel strip in a continuous fashion comprising the steps of:a. heating a pre-pickling tank, said pre-pickling tank containing an aqueous solution consisting of sulfuric acid and hydrofluoric acid, and immersing said strip in said pre-pickling tank; and b. immersing said strip in a pickling tank, after step a, said pickling tank containing an aqueous solution consisting of sulfuric acid, hydrofluoric acid and from about 5 g/l to less than 10 g/l of hydrogen peroxide. c. removing heat from the pickling solution of step b.
- 15. The process of claim 14 wherein said strip is scrubbed after step a and prior to immersion in said pickling tank.
- 16. The process of claim 15 wherein said strip is immersed in a de-smutting tank prior to being scrubbed, said de-smutting tank containing an solution consisting of hydrogen peroxide, sulfuric acid and hydrofluoric acid.
- 17. The process of claim 16 wherein the aqueous solution in said pre-pickling tank consists of from about 90 g/l to about 200 g/l sulfuric acid and from about 10 g/l to about 60 g/l hydrofluoric acid.
- 18. The process of claim 17 wherein the aqueous solution in the pre-pickling tank is maintained at a temperature of from about 54° C. to about 77° C.
- 19. The process of claim 18 wherein the sulfuric acid in the pickling tank has a concentration of from about 20 g/l to about 60 g/l and the hydrofluoric acid in the picking tank has a concentration of from about 2 g/l to about 50 g/l.
- 20. The process of claim 19 wherein the aqueous solution in the pickling tank is maintained at a temperature of from about 20° C. to about 60° C.
- 21. The process of claim 20 wherein the aqueous solution in the pickling tank is maintained at a temperature of from about 35° C. to about 50° C.
- 22. The process of claim 21 wherein overflow solution from the pickling tank is channeled into the de-smutting tank.
- 23. The process of claim 22 wherein a filtration device and a heat exchanger are external to and coupled to the pickling tank, and the filtration device and heat exchanger are arranged in a re-circulating loop so that at any time, a portion of the aqueous pickling solution from the pickling tank is routed through the filtration device and heat exchanger and the resulting aqueous solution is deposited back into the pickling tank through at least one inlet located inside the pickling tank.
Parent Case Info
This application is based on and claims priority from U.S. provisional Patent Application Serial No. 60/282,565, Vijay N. Madi, Jerald W. Leeker, Clayton A. Van Scoy, filed Apr. 9, 2001.
US Referenced Citations (36)
Foreign Referenced Citations (8)
Number |
Date |
Country |
582121 |
Feb 1994 |
EP |
910356 |
Nov 1962 |
GB |
55018552 |
Feb 1980 |
JP |
55050468 |
Apr 1980 |
JP |
61049706 |
Mar 1986 |
JP |
A-2122087 |
May 1990 |
JP |
11269677 |
Oct 1999 |
JP |
WO 02081777 |
Oct 2002 |
WO |
Provisional Applications (1)
|
Number |
Date |
Country |
|
60/282565 |
Apr 2001 |
US |