EP0291493B1 - Procédé de découpage électrolytique d'acier inoxydable contenant du chrome - Google Patents

Procédé de découpage électrolytique d'acier inoxydable contenant du chrome Download PDF

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Publication number
EP0291493B1
EP0291493B1 EP88890097A EP88890097A EP0291493B1 EP 0291493 B1 EP0291493 B1 EP 0291493B1 EP 88890097 A EP88890097 A EP 88890097A EP 88890097 A EP88890097 A EP 88890097A EP 0291493 B1 EP0291493 B1 EP 0291493B1
Authority
EP
European Patent Office
Prior art keywords
solution
na2so4
redox potential
acid
pickling
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
Application number
EP88890097A
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German (de)
English (en)
Other versions
EP0291493A1 (fr
Inventor
Gerald Dipl.-Ing. Dr. Techn. Maresch
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Andritz AG
Original Assignee
Andritz AG
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Filing date
Publication date
Application filed by Andritz AG filed Critical Andritz AG
Publication of EP0291493A1 publication Critical patent/EP0291493A1/fr
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Classifications

    • 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
    • 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 process for the electrolytic pickling of chromium-containing stainless steel, in which firstly in an aqueous Na2SO4 solution and then in acid, preferably mixed acid, optionally pickled without current.
  • acid preferably mixed acid
  • Such a method is described in AT-PS 252.685, hydrofluoric acid plus nitric acid being used as the mixed acid.
  • the scale is removed, while in the second step the chrome-depleted layer underneath the scale, which is formed during the annealing process, is detached.
  • This method has established itself worldwide, for example for pickling stainless steel strips, but has the disadvantage that the Cr in the scale through the current to the CrO 2- 4th is oxidized, while Fe dissolved as Fe (OH) 3 precipitates immediately.
  • the CrO formed 2- 4th remains in solution and is only dragged out when desludging or with the stainless steel belt and only then detoxified by reducing agents. For this, reduction with an aqueous FeSO4 solution in the pH range of 0-2 or 7-8 has mainly prevailed. In both cases, neutralization must then be carried out again in order to precipitate all metal ions in the solution as hydroxides. In addition, if there is a very large, sudden attack of CrO 2- 4th solutions always contain the risk of a breakthrough of CrO 2- 4th given, which then came into the sewage. Another disadvantage of the process is that only a fraction of the CrO 2- 4th is removed from the aqueous solution of Na2SO4, but the rest increases the concentration in the solution and leads to increased attack on plastic pipes and pumps.
  • the object of the invention is to provide a method of type mentioned, which avoids the disadvantages mentioned.
  • aqueous Na2SO4 solution acid and reducing agent are added according to the pH and redox potential, so that a CrO 2- 4th -free pickling solution is achieved.
  • the pH of the solution is less than 3, preferably 1.5 to 2.5, advantageously 2, by adding H2SO4.
  • the oxidation of these substances also forms Na2SO4, which again serves as the conductive salt in the Na2SO4 solution and by suitable choice of the pH of this solution it is possible to let the dissolved Fe3+ precipitate as Fe (OH) 3 after the solubility has been exceeded , whereby the solution does not have to be completely discarded at a certain Fe concentration, but only has to be freed from the Fe (OH) 3 sludge.
  • the concentration of Na2SO4 in the solution is 10 to 250g / l, preferably 170 to 200g / l.
  • the pH for these reactions is chosen to be less than 3, preferably 1.5 to 2.5, advantageously 2.
  • the reaction rate in the solution is sufficiently high and the redox potential measured against a calomel electrode in the CrO 2- 4th containing solution 50 to 100mV larger than in the CrO 2- 4th -free solution.
  • the redox potential measured against a calomel electrode in the CrO 2- 4th containing solution 50 to 100mV larger than in the CrO 2- 4th -free solution.
  • other, analyt in addition to the redox potential, other, analyt.
  • the addition of reducing agent was stopped until the redox potential again 620 mV had risen. After about another 4 hours the analyte was. certain Cr6+ concentration o, 11 g Cr6+ / l.
  • solid Na2S2O5 in an amount of 0.9 g Na2S2O5 (62%) per liter, the redox potential could be set to 520 mV again, measured against a calomel electrode, and no Cr6+ could be detected analytically.
  • the pH of the solution dropped from 2.0 to 1.9.
  • the stainless steel strip was free of scale and silvery after treatment with acid or mixed acid.

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)
  • Inorganic Compounds Of Heavy Metals (AREA)
  • Treatment Of Sludge (AREA)
  • Preparation Of Compounds By Using Micro-Organisms (AREA)

Claims (3)

  1. Procédé pour le décapage électrolytique d'acier fin contenant du chrome, selon lequel on décape éventuellement sans courant tout d'abord dans une solution aqueuse de Na₂SO₄ et ensuite dans de l'acide de préférence un mélange d'acide, caractérisé en ce que la valeur du pH de la solution aqueuse Na₂SO₄, par addition de H₂SO₄ est ramenée en dessous de 3, de préférence de 1,5 à 2,5, de manière appropriée à 2, en ce que le potentiel Rédox de la solution est mesuré contre une électrode calomel et qu'on ajoute suffisamment d'acide et de réducteur pour réduire le chrome hexavalent, jusqu'a ce que le potentiel Rédox diminue de 50 à 100 mV et en ce que le potentiel Rédox est maintenu à la valeur atteinte de manière à obtenir une solution de décapage exempte de CrO₄²⁻.
  2. Procédé selon la revendication 1, caractérisé en ce qu'une substance du groupe NaxHySzOv est utilisée en tant que réducteur, où on a l'égalité x = 0 à 2, y = 0 à 2, z = 1 à 6 et v = 2 à 6, et qu'au moment de la réaction, du Na₂SO₄ se forme également.
  3. Procédé selon la revendication 1, caractérisé en ce que la concentration de Na₂SO₄ de la solution est déterminée de 100 à 250 g/l de préférence de 170 à 200 g/l.
EP88890097A 1987-05-07 1988-04-20 Procédé de découpage électrolytique d'acier inoxydable contenant du chrome Expired - Lifetime EP0291493B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AT1147/87 1987-05-07
AT0114787A AT387406B (de) 1987-05-07 1987-05-07 Verfahren zum elektrolytischen beizen von chromhaeltigem edelstahl

Publications (2)

Publication Number Publication Date
EP0291493A1 EP0291493A1 (fr) 1988-11-17
EP0291493B1 true EP0291493B1 (fr) 1994-08-17

Family

ID=3507621

Family Applications (1)

Application Number Title Priority Date Filing Date
EP88890097A Expired - Lifetime EP0291493B1 (fr) 1987-05-07 1988-04-20 Procédé de découpage électrolytique d'acier inoxydable contenant du chrome

Country Status (8)

Country Link
US (1) US4851092A (fr)
EP (1) EP0291493B1 (fr)
JP (1) JP2649380B2 (fr)
KR (1) KR960001599B1 (fr)
AT (1) AT387406B (fr)
DE (1) DE3851086D1 (fr)
ES (1) ES2058340T3 (fr)
FI (1) FI86649C (fr)

Families Citing this family (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT391486B (de) * 1988-09-14 1990-10-10 Andritz Ag Maschf Verfahren zum elektrolytischen beizen von edelstahlband
KR920003063B1 (ko) * 1990-02-28 1992-04-13 재단법인 한국화학연구소 신규한2-(2-이미다졸린-2-일)-3-(아미노옥소아세틸)-피리딘유도체와그염
AT395601B (de) * 1990-07-27 1993-02-25 Andritz Ag Maschf Verfahren zum beizen von edelstahl
JPH0762279B2 (ja) * 1991-08-02 1995-07-05 日本冶金工業株式会社 ステンレス鋼の中性塩電解脱スケール方法
TW401471B (en) * 1994-07-28 2000-08-11 Hitachi Ltd Treatment of neutral salt electrolyte, and treating device therefor, descaling of stanless steel and device therefor
AT401183B (de) * 1995-02-15 1996-07-25 Andritz Patentverwaltung Verfahren zur regeneration von elektrolyten, insbesondere na2so4 aus abbeizen von edelstahl, insbesondere edelstahlbändern
AT404030B (de) * 1995-02-15 1998-07-27 Andritz Patentverwaltung Verfahren zur beize von materialien aus stahl, insbesondere edelstahl
US5830291C1 (en) * 1996-04-19 2001-05-22 J & L Specialty Steel Inc Method for producing bright stainless steel
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
AT408451B (de) 1999-11-18 2001-12-27 Andritz Ag Maschf Verfahren zur herstellung von edelstahlbändern mit verbesserten oberflächeneigenschaften

Family Cites Families (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3025225A (en) * 1959-10-05 1962-03-13 Boeing Co Electrolytic acid descaling of metals
AT252685B (de) * 1964-12-22 1967-03-10 Ruthner Ind Planungs Ag Verfahren zum Beizen hochlegierter Stähle und Sonderlegierungen
US3715308A (en) * 1971-06-04 1973-02-06 Oxy Metal Finishing Corp Apparatus and process for treating toxic waste materials
JPS495866A (fr) * 1972-02-08 1974-01-19
JPS5047827A (fr) * 1973-08-31 1975-04-28
JPS5216863A (en) * 1975-07-28 1977-02-08 Onomichi Kumika Kogyo Kk Treating agent and method for wastewater containing hexa-chromium ions
JPS5256755A (en) * 1975-11-06 1977-05-10 Tokico Ltd Process for treating aqueous solution containing chromate ions which i ncludes insoluble heavy metal hydroxide
JPS5321078A (en) * 1976-08-11 1978-02-27 Hitachi Ltd Treating method for waste liquid for electrolytic processing
JPS5710200A (en) * 1980-06-20 1982-01-19 Matsushita Electric Ind Co Ltd Voice synthesizer
US4363709A (en) * 1981-02-27 1982-12-14 Allegheny Ludlum Steel Corporation High current density, acid-free electrolytic descaling process
JPS5956600A (ja) * 1982-09-27 1984-04-02 Sumitomo Metal Ind Ltd 片面電気メツキ鋼板の製造方法
US4415415A (en) * 1982-11-24 1983-11-15 Allegheny Ludlum Steel Corporation Method of controlling oxide scale formation and descaling thereof from metal articles
JPS60122092A (ja) * 1983-12-05 1985-06-29 Suirei:Kk ６価クロム含有排水の処理装置
JPS60234998A (ja) * 1984-05-02 1985-11-21 Chem Yamamoto:Kk 金属材表面の除染清浄化方法

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
A.ARANEO -"CHIMICA ANALITICA QUALITATIVA" LIBRERIA ED., p.112 *

Also Published As

Publication number Publication date
FI86649C (fi) 1992-09-25
EP0291493A1 (fr) 1988-11-17
AT387406B (de) 1989-01-25
JPS63286600A (ja) 1988-11-24
KR960001599B1 (ko) 1996-02-02
US4851092A (en) 1989-07-25
FI882098A (fi) 1988-11-08
ES2058340T3 (es) 1994-11-01
FI86649B (fi) 1992-06-15
FI882098A0 (fi) 1988-05-05
DE3851086D1 (de) 1994-09-22
KR880014141A (ko) 1988-12-23
JP2649380B2 (ja) 1997-09-03
ATA114787A (de) 1988-06-15

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