EP0359736B1 - Verfahren zum elektrolytischen Beizen von Edelstahl - Google Patents
Verfahren zum elektrolytischen Beizen von Edelstahl Download PDFInfo
- Publication number
- EP0359736B1 EP0359736B1 EP89890225A EP89890225A EP0359736B1 EP 0359736 B1 EP0359736 B1 EP 0359736B1 EP 89890225 A EP89890225 A EP 89890225A EP 89890225 A EP89890225 A EP 89890225A EP 0359736 B1 EP0359736 B1 EP 0359736B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- solution
- nano3
- naf
- special steel
- aqueous
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D1/00—Electroforming
- C25D1/04—Wires; Strips; Foils
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
- C25F1/00—Electrolytic cleaning, degreasing, pickling or descaling
- C25F1/02—Pickling; Descaling
- C25F1/04—Pickling; Descaling in solution
- C25F1/06—Iron or steel
Definitions
- the invention relates to a method for the electrolytic pickling of stainless steel strip, in particular stainless steel hot strip, in which the stainless steel hot strip is initially anodically and cathodically pickled in an aqueous neutral solution of Na2SO4.
- AT-PS 252 685 and AT-PS 240 674 describe two-stage electrolytic pickling processes, the first pickling bath being an aqueous solution of a neutral alkali salt of a mineral acid, preferably sodium sulfate. This is followed by electrolytic pickling in aqueous solutions of mineral acids, examples of which are sulfuric, nitric, hydrochloric or mixed acids. In all of the above-mentioned processes, however, it has not or only insufficiently been possible to effectively prevent the formation of toxic vapors, including nitrous gases.
- the object of the present invention is to provide a method for electrolytic pickling of stainless steel strips, in which the formation of nitrous gases is completely avoided in the aftertreatment, which furthermore with a low cost and Workload works and delivers a scale-free, bright shiny stainless steel band.
- aqueous neutral salt solution which contains the same anions as the conventional HNO3 / HF mixed acid, after another Characteristic the aqueous neutral salt solution is a solution of NaNO3 and NaF.
- Another feature of the method according to the invention is that the concentration of NaNO3 between 100 and 400 g / l, preferably 200 to 300 g / l and the concentration of NaF between 10 and 100 g / l, preferably between 40 and 60 g / l is.
- the temperature in the solution of NaNO3 and NaF is between 20 and 90 ° C, preferably between 60 and 80 ° C.
- the anodic and cathodic current density during electrolytic pickling in the solution of NaNO3 and NaF is between 1 and 50 A / dm2, preferably between 10 and 30 A / dm2.
- the scaled stainless steel strip After the scaled stainless steel strip has been alternately anodically and cathodically pickled in an aqueous solution of Na2SO4, it is rinsed and brushed with plastic brushes. Thereupon it is alternately anodically and cathodically pickled to remove the remaining adhering scale in an aqueous neutral salt solution which contains the same anions as the conventional nitric-hydrofluoric acid mixture.
- a solution of NaNO3 and NaF is preferably prepared for this purpose.
- the neutral salt solution is generally prepared by adding the respective nitrates or fluorides in the desired amount in water.
- other manufacturing methods are also possible, especially in the course of small-scale test facilities, where e.g. a neutralization of HNO3 / HF mixed acid with alkali can be done.
- Economic considerations lead to the use of sodium salts, since these are the cheapest in terms of price, but the use of nitrates and fluorides with other cations, such as potassium, is just as possible.
- the electrolytic pickling with NaNO3 and NaF prevents the formation of nitrous gases, since the stainless steel strip is not pickled in acid, but the acid is only produced where it is needed by electrolysis.
- Another advantage of this method according to the invention is that the dissolved scale does not dissolve as a salt and thus consumes acid, but instead precipitates out as a hydroxide.
- This metal hydroxide sludge formed during pickling is separated from the solution by mechanical methods such as filters, thickeners or centrifuges. This not only reduces the consumption of chemicals, it also creates easily depositable metal hydroxides.
- a stainless steel hot strip of quality AISI 304 was irradiated in a combined annealing and pickling line before pickling in order to partially remove the scale on the surface and then electrolytically in an aqueous Na2SO4 solution, a concentration of 150 g / l with 10 A / dm2 alternately anodically and cathodically pickled, keeping the temperature in the range between 60 and 80 ° C.
- the stainless steel strip was first pickled in a purely chemical manner in the same temperature range in an aqueous solution of 150 g / l HNO3 and 25 g / l HF to remove the chromium-depleted layer.
- the tape was scale-free, but when pickling in the acid nitrous gases were produced in a concentration of 500 - 800 ppm, which had to be removed from the exhaust gas in the exhaust gas cleaning system.
- a 10-20% aqueous solution of urea was added to the second pickling bath to reduce the emission of nitrous gases, but the concentration of nitrous gases was reduced from 500-800 ppm to 100-150 ppm, but could not be completely avoided.
- the acid was then neutralized with sodium hydroxide solution so that an aqueous, neutral solution with a concentration of 200 g / l NaNO3 and 50 g / l NaF was obtained.
- the pickling tub was equipped with electrodes and these were connected to a rectifier.
- a scale-free band was also obtained at a current density of 20 A / dm 2 and in the same temperature range as in Example 1, but there was no emission of nitrous gases in the suction plant.
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
- Electroplating Methods And Accessories (AREA)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AT0225888A AT391486B (de) | 1988-09-14 | 1988-09-14 | Verfahren zum elektrolytischen beizen von edelstahlband |
AT2258/88 | 1988-09-14 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0359736A1 EP0359736A1 (de) | 1990-03-21 |
EP0359736B1 true EP0359736B1 (de) | 1993-02-03 |
Family
ID=3530989
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP89890225A Expired - Lifetime EP0359736B1 (de) | 1988-09-14 | 1989-09-01 | Verfahren zum elektrolytischen Beizen von Edelstahl |
Country Status (9)
Country | Link |
---|---|
US (1) | US5022971A (fi) |
EP (1) | EP0359736B1 (fi) |
JP (1) | JPH0713320B2 (fi) |
KR (1) | KR950012425B1 (fi) |
AT (1) | AT391486B (fi) |
DE (1) | DE58903444D1 (fi) |
ES (1) | ES2039949T3 (fi) |
FI (1) | FI90093C (fi) |
ZA (1) | ZA896965B (fi) |
Families Citing this family (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH0774480B2 (ja) * | 1991-05-01 | 1995-08-09 | 中外炉工業株式会社 | ステンレス鋼帯の連続焼鈍酸洗設備 |
AT399167B (de) * | 1991-06-10 | 1995-03-27 | Andritz Patentverwaltung | Verfahren und vorrichtung zum elektrolytischen beizen von kontinuierlich durchlaufendem elektrisch leitendem gut |
ES2142018T3 (es) * | 1995-09-15 | 2000-04-01 | Mannesmann Ag | Procedimiento e instalacion para el tratamiento de productos en forma de fleje de acero inoxidable. |
US6096183A (en) * | 1997-12-05 | 2000-08-01 | Ak Steel Corporation | Method of reducing defects caused by conductor roll surface anomalies using high volume bottom sprays |
AT406486B (de) * | 1998-12-22 | 2000-05-25 | Andritz Patentverwaltung | Verfahren zum beizen von edelstahl |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
AT1461B (fi) * | 1899-06-12 | 1900-06-11 | Ver Elek Citaets Actien Ges | |
AT213190B (de) * | 1958-12-23 | 1961-01-25 | Othmar Ing Ruthner | Verfahren zum Beizen von legierten Stählen |
AT240674B (de) * | 1963-04-25 | 1965-06-10 | Othmar Ing Ruthner | Verfahren zum elektrolytischen Beizen von niedriglegierten und Kohlenstoffstählen |
AT252685B (de) * | 1964-12-22 | 1967-03-10 | Ruthner Ind Planungs Ag | Verfahren zum Beizen hochlegierter Stähle und Sonderlegierungen |
AT252674B (de) * | 1965-04-09 | 1967-03-10 | Othmar Matzke | Zur Aufnahme des Achsdruckes geeignete (lasttragende) Abrollverzahnung |
IT1047584B (it) * | 1975-09-26 | 1980-10-20 | Centro Speriment Metallurg | Metodo per migliorare la suscetti bilita dell acciaio ai rivestimenti |
FR2431554A1 (fr) * | 1978-07-20 | 1980-02-15 | Ruthner Industrieanlagen Ag | Procede pour le decapage electrolytique de bandes laf d'acier inoxydable |
AT387406B (de) * | 1987-05-07 | 1989-01-25 | Andritz Ag Maschf | Verfahren zum elektrolytischen beizen von chromhaeltigem edelstahl |
-
1988
- 1988-09-14 AT AT0225888A patent/AT391486B/de not_active IP Right Cessation
-
1989
- 1989-08-24 FI FI893978A patent/FI90093C/fi not_active IP Right Cessation
- 1989-09-01 DE DE8989890225T patent/DE58903444D1/de not_active Expired - Fee Related
- 1989-09-01 EP EP89890225A patent/EP0359736B1/de not_active Expired - Lifetime
- 1989-09-01 ES ES198989890225T patent/ES2039949T3/es not_active Expired - Lifetime
- 1989-09-06 KR KR89012905A patent/KR950012425B1/ko not_active IP Right Cessation
- 1989-09-08 JP JP1234527A patent/JPH0713320B2/ja not_active Expired - Lifetime
- 1989-09-13 US US07/406,342 patent/US5022971A/en not_active Expired - Fee Related
- 1989-09-13 ZA ZA896965A patent/ZA896965B/xx unknown
Also Published As
Publication number | Publication date |
---|---|
US5022971A (en) | 1991-06-11 |
ATA225888A (de) | 1990-04-15 |
FI893978A0 (fi) | 1989-08-24 |
ES2039949T3 (es) | 1993-10-01 |
KR900004969A (ko) | 1990-04-13 |
FI90093C (fi) | 1993-12-27 |
DE58903444D1 (de) | 1993-03-18 |
FI893978A (fi) | 1990-03-15 |
JPH02107800A (ja) | 1990-04-19 |
KR950012425B1 (en) | 1995-10-17 |
EP0359736A1 (de) | 1990-03-21 |
ZA896965B (en) | 1990-06-27 |
AT391486B (de) | 1990-10-10 |
FI90093B (fi) | 1993-09-15 |
JPH0713320B2 (ja) | 1995-02-15 |
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