EP0359736A1 - Method of electrolytically pickling special steel - Google Patents

Method of electrolytically pickling special steel Download PDF

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Publication number
EP0359736A1
EP0359736A1 EP89890225A EP89890225A EP0359736A1 EP 0359736 A1 EP0359736 A1 EP 0359736A1 EP 89890225 A EP89890225 A EP 89890225A EP 89890225 A EP89890225 A EP 89890225A EP 0359736 A1 EP0359736 A1 EP 0359736A1
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solution
stainless steel
nano3
naf
aqueous
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EP89890225A
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German (de)
French (fr)
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EP0359736B1 (en
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Gerald Dipl.-Ing. Dr. Tech. Maresch
Ulrich Krupicka
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Andritz AG
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Andritz AG
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    • 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.
  • 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 in water by adding the respective nitrates or fluorides in the desired amount.
  • 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 Na2SO, 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 / dm2 and in the same temperature range as in Example 1, but there was no emission of nitrous gases in the suction system.

Abstract

In a method of electrolytically pickling steel strip, in particular hot-rolled special steel strip, the hot-rolled special steel strip is alternately pickled anodically and cathodically in an aqueous solution of Na2SO4 and then in an aqueous solution of NaNO3 and NaF, whereby the formation of hazardous nitrous gases is prevented.

Description

Der Erfindung betrifft ein Verfahren zum elektrolytischen Beizen von Edelstahlband, insbesondere von Edelstahl-Warmband, bei welchem das Edelstahl-Warmband vorerst in einer wässrigen neutralen Lösung von Na₂SO₄ abwechselnd anodisch und kathodisch gebeizt wird.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.

Verfahren zum elektrolytischen Beizen von Edelstahl in verschiedenen Säuren, wie beispielsweise Schwefelsäure oder Salpetersäure, sind seit vielen Jahren bekannt und haben sich bereits weltweit durchgesetzt. Derartige Verfahren benötigen jedoch als nachfolgenden Schritt eine Behandlung in einer Mischsäure, wie beispielsweise einer Mischung von Salpetersäure und Flußsäure, um die chromverarmte Schicht an der Oberfläche zu entfernen. Ein seit längerer Zeit bekanntes Problem bei diesen Verfahren liegt nun darin, daß bei dieser Säurenachbehandlung gefährliche Gase,wie nitrose Gase, frei werden.Processes for the electrolytic pickling of stainless steel in various acids, such as sulfuric acid or nitric acid, have been known for many years and have already become established worldwide. However, as a subsequent step, such processes require treatment in a mixed acid, such as, for example, a mixture of nitric acid and hydrofluoric acid, in order to remove the chromium-depleted layer on the surface. A problem with these processes which has been known for a long time now lies in the fact that dangerous gases, such as nitrous gases, are released during this acid aftertreatment.

Infolgedessen wurden verschiedene Verfahren entwickelt, um diese nitrosen Gase durch Zusatz von Harnstoff oder Wasserstoffperoxid zur Mischsäure zu vermeiden.As a result, various methods have been developed to avoid these nitrous gases by adding urea or hydrogen peroxide to the mixed acid.

Des weiteren wurde versucht, den Edelstahl in einer wässrigen Neutralsalzlösung vorzubehandeln und anschließend mit Mischsäure fertigzubeizen. So beschreiben etwa die AT-PS 252 685 und die AT-PS 240 674 zweistufige elektrolytische Beizverfahren, wobei das erste Beizbad eine wässrige Lösung eines neutralen Alkalisalzes einer Mineralsäure, vorzugsweise Natriumsulfat ist. Anschließend folgt eine elektrolytische Beize in wässrigen Lösungen von Mineralsäuren, wofür Schwefel-, Salpeter-, Salz- oder Mischsäuren als Beispiele angegeben werden. In all diesen genannten Verfahren ist es jedoch nicht oder nur unzureichend gelungen, die Bildung giftiger Dämpfe, unter anderem nitroser Gase, wirksam zu verhindern.Furthermore, attempts were made to pretreat the stainless steel in an aqueous neutral salt solution and then to finish-pickle it with mixed acid. For example, 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.

Die Aufgabe der vorliegenden Erfindung liegt nun darin, ein Verfahren zu elektrolytischen Beizen von Edelstahlbändern zu schaffen, bei welchem in der Nachbehandlung die Bildung nitroser Gase vollständig vermieden wird, welches des weiteren mit einem geringen Kosten- und Arbeitsaufwand arbeitet und ein zunderfreies, hell glänzendes Edelstahlband liefert.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.

Diese Aufgabe wird bei einem Verfahren der eingangs genannten Art erfindungsgemäß dadurch gelöst, daß das Edelstahl-Warmband anschließend in einer wässrigen Neutralsalzlösung, welche die selben Anionen enthält wie die herkömmliche HNO₃/HF-Mischsäure, abwechselnd anodisch und kathodisch gebeizt wird, wobei nach einem weiteren Merkmal die wässrige Neutralsalzlösung eine Lösung von NaNO₃ und NaF ist.This object is achieved according to the invention in a process of the type mentioned at the outset in that the stainless steel hot strip is then alternately anodically and cathodically pickled in an aqueous neutral salt solution which contains the same anions as the conventional HNO.sub.3 / HF mixed acid, after another Feature the aqueous neutral salt solution is a solution of NaNO₃ and NaF.

Ein weiteres Merkmal des erfindungsgemäßen Verfahrens liegt darin, daß die Konzentration an NaNO₃ zwischen 100 und 400 g/l, vorzugsweise 200 bis 300 g/l und die Konzentration von NaF Zwischen 10 und 100 g/l, vorzugsweise zwischen 40 und 60 g/l beträgt.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.

Nach einem weiteren Merkmal des erfindungsgemäßen Verfahrens beträgt die Temperatur in der Lösung von NaNO₃ und NaF zwischen 20 und 90°C, vorzugsweise zwischen 60 und 80°C.According to a further feature of the method according to the invention, the temperature in the solution of NaNO₃ and NaF is between 20 and 90 ° C, preferably between 60 and 80 ° C.

Als weiteres Merkmal des erfindungsgemäßen Verfahrens ist vorgesehen, daß die anodische und die kathodische Stromdichte beim elektrolytischen Beizen in der Lösung von NaNO₃ und NaF zwischen 1 und 50 A/dm², vorzugsweise zwischen 10 und 30 A/dm² beträgt.As a further feature of the method according to the invention it is provided that 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.

Nachdem das verzunderte Edelstahlband in einer wässrigen Lösung von Na₂SO₄ abwechselnd anodisch und kathodisch gebeizt wurde, wird es gespült und mit Kunststoffbürsten gebürstet. Hierauf wird es zur Entfernung des restlichen anhaftenden Zunders in einer wässrigen Neutralsalzlösung, welche die selben Anionen enthält wie die herkömmliche Salpeter-Flußsäure-Mischung, abwechselnd anodisch und kathodisch gebeizt. Vorzugsweise wird zu diesem Zweck eine Lösung von NaNO₃ und NaF angesetzt. Nach der anschließenden Schlußspülung, welche ebenfalls eine mechanische Bandreinigung mit Bürsten enthält, erhält man ein zunderfreies, hell glänzendes Edelstahlband.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. After the subsequent final rinse, which also contains mechanical belt cleaning with brushes, a scale-free, bright, shiny stainless steel belt is obtained.

Die Neutralsalzlösung wird im allgemeinen durch Zugabe der jeweiligen Nitrate bzw. Fluoride in der gewünschten Menge in Wasser hergestellt. Jedoch sind auch andere Herstellwege möglich, insbesondere im Zuge von Versuchsanlagen kleiner Dimensionen, wo z.B. ein Neutralisieren von HNO₃/HF-Mischsäure mit Alkalilaugen erfolgen kann. Wirtschaftliche Überlegungen führen zur Verwendung der Natriumsalze, da diese preislich am günstigsten sind, doch ist die Verwendung von Nitraten und Fluoriden mit anderen Kationen, wie etwa Kalium, genausogut möglich.The neutral salt solution is generally prepared in water by adding the respective nitrates or fluorides in the desired amount. However, 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.

Durch die elektrolytische Beize mit NaNO₃ und NaF wird die Bildung von nitrosen Gasen vermieden, da das Edelstahlband nicht in Säure gebeizt wird, sondern die Säure nur dort, wo sie benötigt wird, durch Elektrolyse hergestellt wird.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.

Ein weiterer Vorteil dieses erfindungsgemäßen Verfahrens liegt darin, daß der gelöste Zunder nicht als Salz in Lösung geht und somit Säure verbraucht, sondern gleich als Hydroxid ausfällt.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.

Dieser beim Beizen entstehende Metallhydroxidschlamm wird durch mechanische Methoden, wie beispielsweise Filter, Eindicker oder Zentrifugen, von der Lösung abgetrennt. Damit wird nicht nur der Chemikalienverbrauch reduziert, sondern es entstehen auch leicht deponierbare Metallhydroxide.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.

Nachfolgend werden anhand von Ausführungsbeispielen weitere Einzelheiten bzw. Vorteile des vorliegenden erfindungsgemäßen Verfahrens beschrieben:Further details and advantages of the method according to the invention are described below using exemplary embodiments:

Beispiel 1:Example 1:

Ein Edelstahl-Warmband der Qualität AISI 304 wurde in einer kombinierten Glüh- und Beizlinie vor dem Beizen bestrahlt, um den Zunder an der Oberfläche teilweise zu entfernen und anschließend elektrolytisch in einer wässrigen Na₂SO₄-Lösung, einer Konzentration von 150 g/l mit 10 A/dm² abwechselnd anodisch und kathodisch gebeizt, wobei die Temperatur im Bereich zwischen 60 und 80°C gehalten wurde. Zum Vergleich mit dem erfindungsgemäßen Verfahren wurde das Edelstahlband zuerst auf rein chemische Weise im selben Temperaturbereich in einer wässrigen Lösung von 150 g/l HNO₃ und 25 g/l HF zur Entfernung der chromverarmten Schicht fertig gebeizt. Das Band war zunderfrei, doch entstanden beim Beizen in der Säure nitrose Gase in einer Konzentration von 500 - 800 ppm, die in der Abgasreinigungsanlage aus dem Abgas entfernt werden mußten.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 Na₂SO, 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. For comparison with the inventive method, 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.

Beispiel 2:Example 2:

Bei der gleichen Anlage und unveränderten Parametern wurde zur Verringerung der Emission an nitrosen Gasen dem zweiten Beizbad eine wässrige 10-20%ige Lösung von Harnstoff zugesetzt, wodurch die Konzentration an nitrosen Gasen von 500 - 800 ppm auf 100 - 150 ppm verringert wurde, aber nicht vollständig vermieden werden konnte.With the same system and unchanged parameters, 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.

Beispiel 3:Example 3:

Um ein Band nunmehr nach dem Verfahren gemäß der Erfindung behandeln zu können, wurde die Säure anschließend mit Natronlauge neutralisiert sodaß eine wässrige, neutrale Lösung mit einer Konzentration von 200 g/l NaNO₃ und 50 g/l NaF erhalten wurde. Der Beizbottich wurde mit Elektroden ausgestattet und diese an einen Gleichrichter angeschlossen. Bei gleicher Behandlungsgeschwindigkeit in der Anlage wurde bei einer Stromdichte von 20 A/dm² und in demselben Temperaturbereich wie in Beispiel 1 ebenfalls ein zunderfreies Band erhalten, es kam jedoch zu keiner Emission von nitrosen Gasen in der Absauganlage.In order to be able to treat a tape now by the method according to the invention, 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. At the same treatment speed in the system, a scale-free band was also obtained at a current density of 20 A / dm² and in the same temperature range as in Example 1, but there was no emission of nitrous gases in the suction system.

Beispiel 4:Example 4:

Die Versuche wurden mit identischen Parametern wie in den ersten drei Beispielen bei einem ferritischen Warmband der Qualität AISI 430 wiederholt. Beim Beizen mit Säure entstanden dabei 3000 -5000 ppm nitrose Gase, die durch Zugabe von Harnstoff auf 500 - 750 ppm reduziert werden konnten. Wurde dagegen die Nachbehandlung mit einer wässrigen NaNO₃- und NaF-Lösung durchgeführt, entstanden keine nitrogen Gase und das Edelstahlband war bei gleicher Behandlungslänge und Anlagengeschwindigkeit ebenfalls zunderfrei.The tests were repeated with identical parameters as in the first three examples with a ferritic hot strip of quality AISI 430. When pickling with acid, 3000 to 5000 ppm of nitrous gases were generated, which could be reduced to 500 to 750 ppm by adding urea. In contrast, if the aftertreatment was carried out with an aqueous NaNO₃ and NaF solution, none were formed nitrogen gases and the stainless steel strip were also scale-free with the same treatment length and line speed.

Beispiel 5:Example 5:

Beide Edelstahlbänder wurden im Kaltwalzwerk gewalzt, anschließend geglüht und nochmals gebeizt. Auch hier entstanden bei der Nachbehandlung in der NaNO₃-NaF-Lösung keine nitrosen Gase, während beim Beizen in Säure bei AISI 304 300 - 500 ppm und bei AISI 430 800 - 1000 ppm nitroser Gase im Abgas gemessen wurden.Both stainless steel strips were rolled in the cold rolling mill, then annealed and pickled again. Here, too, no nitrous gases were formed during the aftertreatment in the NaNO₃-NaF solution, while 300-500 ppm and AISI 430 800-1000 ppm nitrous gases were measured in the exhaust gas when pickling in acid.

Claims (5)

1. Verfahren zum elektrolytischen Beizen von Edelstahlband, insbesondere eines Edelstahl-Warmbander, bei welchem das Edelstahl-Warmband vorest in einer wässrigen neutralen Lösung von Na₂SO₄ abwechselnd anodisch und kathodisch gebeizt wird, wobei die Konzentration an Na₂SO₄ in der wässrigen Lösung zwischen 50 und 300 g/l, vorzugsweise zwischen 100 und 200 g/l, die Temperatur zwischen 20 und 90°C, vorzugsweise zwischen 60 und 80°C, und die anodische und die kathodische Stromdichte beim elektrolytischen Beizen zwischen 1 und 50 A/dm², vorzugsweise zwischen 10 und 30 A/dm², beträgt, dadurch gekennzeichnet, daß das EdelstahlWarmband anschließend in einer wässrigen Neutralsalzlösung, welche die selben Anionen enthält, wie die herkömmliche HNO₃/HF-Mischsäure, abwechselnd anodisch und kathodisch gebeizt wird.1. Process for the electrolytic pickling of stainless steel strip, in particular a stainless steel hot strip, in which the stainless steel hot strip is pre-etched alternately anodically and cathodically in an aqueous neutral solution of Na₂SO₄, the concentration of Na₂SO₄ in the aqueous solution being between 50 and 300 g / l, preferably between 100 and 200 g / l, the temperature between 20 and 90 ° C, preferably between 60 and 80 ° C, and the anodic and cathodic current density during electrolytic pickling between 1 and 50 A / dm², preferably between 10 and 30 A / dm², characterized in that the stainless steel hot band is then alternately anodically and cathodically pickled in an aqueous neutral salt solution which contains the same anions as the conventional HNO₃ / HF mixed acid. 2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß die wässrige Neutralsalzlösung eine Lösung von NaNO₃ und NaF ist.2. The method according to claim 1, characterized in that the aqueous neutral salt solution is a solution of NaNO₃ and NaF. 3. Verfahren nach Anspruch 2, dadurch gekennzeichnet, daß die Konzentration an NaNO₃ zwischen 100 und 400 g/l, vorzugsweise zwischen 200 und 300 g/l, und die Konzentration von NaF zwischen 10 und 100 g/l vorzugsweise zwischen 40 und 60 g/l, beträgt.3. The method according to claim 2, characterized in that the concentration of NaNO₃ between 100 and 400 g / l, preferably between 200 and 300 g / l, and the concentration of NaF between 10 and 100 g / l preferably between 40 and 60 g / l. 4. Verfahren nach Anspruch 2, dadurch gekennzeichnet, daß die Temperatur in der NaNO₃/NaF-Lösung zwischen 20 und 90 °C, vorzugsweise zwischen 60 und 80°C beträgt.4. The method according to claim 2, characterized in that the temperature in the NaNO₃ / NaF solution is between 20 and 90 ° C, preferably between 60 and 80 ° C. 5. Verfahren nach Anspruch 2, dadurch gekennzeichnet, daß die anodische und die kathodische Stromdichte beim elektrolytischen Beizen in der NaNO₃/NaF-Lösung zwischen 1 und 50 A/dm², vorzugsweise zwischen 10 und 30 A/dm², beträgt.5. The method according to claim 2, characterized in that the anodic and cathodic current density during electrolytic pickling in the NaNO₃ / NaF solution is between 1 and 50 A / dm², preferably between 10 and 30 A / dm².
EP89890225A 1988-09-14 1989-09-01 Method of electrolytically pickling special steel Expired - Lifetime EP0359736B1 (en)

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AT2258/88 1988-09-14
AT0225888A AT391486B (en) 1988-09-14 1988-09-14 METHOD FOR ELECTROLYTICALLY STICKING STAINLESS STEEL STRIP

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EP0359736A1 true EP0359736A1 (en) 1990-03-21
EP0359736B1 EP0359736B1 (en) 1993-02-03

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EP (1) EP0359736B1 (en)
JP (1) JPH0713320B2 (en)
KR (1) KR950012425B1 (en)
AT (1) AT391486B (en)
DE (1) DE58903444D1 (en)
ES (1) ES2039949T3 (en)
FI (1) FI90093C (en)
ZA (1) ZA896965B (en)

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AT399167B (en) * 1991-06-10 1995-03-27 Andritz Patentverwaltung METHOD AND DEVICE FOR ELECTROLYTICALLY STICKING CONTINUOUSLY CONTINUOUS ELECTRICALLY CONDUCTIVE GOODS
EP0763609B1 (en) * 1995-09-15 1999-12-15 MANNESMANN Aktiengesellschaft Process and apparatus for treating stainless-steel strips
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 (en) * 1998-12-22 2000-05-25 Andritz Patentverwaltung METHOD FOR STAINLESSING STAINLESS STEEL

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AT391486B (en) 1990-10-10
ES2039949T3 (en) 1993-10-01
KR900004969A (en) 1990-04-13
JPH0713320B2 (en) 1995-02-15
FI893978A (en) 1990-03-15
US5022971A (en) 1991-06-11
KR950012425B1 (en) 1995-10-17
FI90093B (en) 1993-09-15
JPH02107800A (en) 1990-04-19
DE58903444D1 (en) 1993-03-18
EP0359736B1 (en) 1993-02-03
ATA225888A (en) 1990-04-15
ZA896965B (en) 1990-06-27
FI893978A0 (en) 1989-08-24
FI90093C (en) 1993-12-27

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