EP0471662B1 - Verfahren zum Beizen von Edelstahl - Google Patents

Verfahren zum Beizen von Edelstahl Download PDF

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Publication number
EP0471662B1
EP0471662B1 EP91890156A EP91890156A EP0471662B1 EP 0471662 B1 EP0471662 B1 EP 0471662B1 EP 91890156 A EP91890156 A EP 91890156A EP 91890156 A EP91890156 A EP 91890156A EP 0471662 B1 EP0471662 B1 EP 0471662B1
Authority
EP
European Patent Office
Prior art keywords
pickling
sulfuric acid
neutral electrolyte
acid
pretreatment
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
EP91890156A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0471662A3 (en
EP0471662A2 (de
Inventor
Gerald Dr. Dipl.-Ing. Maresch
Erich Mahr
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 Patentverwaltungs GmbH
Original Assignee
Andritz Patentverwaltungs GmbH
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Andritz Patentverwaltungs GmbH filed Critical Andritz Patentverwaltungs GmbH
Publication of EP0471662A2 publication Critical patent/EP0471662A2/de
Publication of EP0471662A3 publication Critical patent/EP0471662A3/de
Application granted granted Critical
Publication of EP0471662B1 publication Critical patent/EP0471662B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • C25F1/04—Pickling; Descaling in solution
    • C25F1/06—Iron or steel

Definitions

  • the invention relates to a method for pickling stainless steel, preferably stainless steel hot strip, in which the stainless steel is subjected to electrolytic pickling with neutral electrolyte, as well as an aftertreatment with mixed acid, nitric acid or a mixture of iron fluoride (FeF3) and hydrofluoric acid, which is carried out using electricity or can be done without power.
  • a method for pickling stainless steel preferably stainless steel hot strip
  • the stainless steel is subjected to electrolytic pickling with neutral electrolyte, as well as an aftertreatment with mixed acid, nitric acid or a mixture of iron fluoride (FeF3) and hydrofluoric acid, which is carried out using electricity or can be done without power.
  • the material is pickled in aqueous solutions of neutral alkali salts of mineral acids and then in aqueous solutions of mineral acids, preferably sulfuric acid, both treatment stages being electrolytic, i.e. done using electricity.
  • An aqueous sodium sulfate solution is preferably used as the neutral electrolyte and the current densities are in the range between 5 and 15 A / dm 2. Higher current densities are possible in principle, but are not used due to the higher voltage required due to the poor conductivity of the stainless steel.
  • mixed acid preferably includes a mixture of nitric acid and hydrofluoric acid.
  • Current pickling in mixed acid is not common because of the problems with the electrode material, which is said to be resistant to current and acid.
  • the pickling time in neutral electrolyte and mixed acid is approximately 120 seconds for approximately 3 mm thick stainless steel hot strip. Approx. 240 seconds for 6 mm thick stainless steel hot strip and even up to 270 seconds for ferritic hot strip of quality AISI 430 and more rational production, the demand for shorter pickling processes persisted.
  • Japanese patent application No. 55 - 50 468 describes a purely chemical process for pickling chromium-containing stainless steel. In each case, it is initially electrolessly pickled in hydrochloric acid or sulfuric acid and then aftertreated to achieve a particular degree of whiteness with Fe (NO3) 3, with Fe2 (SO4) 3 or (NH4) 2S2O8 solution. The scale is removed and a bare, white surface is achieved without electricity and only by the oxidizing aftertreatment with salts of trivalent iron or with persulfates.
  • the method mentioned can only be carried out with ferritic stainless steel, since austenitic stainless steels also contain chromium, but because of the additional alloy element nickel, the scale is constructed in a completely different way and cannot be removed solely by the pickling method described.
  • the object of the invention is therefore a method of the type mentioned in the introduction, in which a reduction in the duration of treatment can be achieved while maintaining or even increasing the good pickling effect achieved to date.
  • the object is achieved in that the pickling with neutral electrolyte precedes a pretreatment with sulfuric acid.
  • the pretreatment with sulfuric acid is carried out at a temperature of 60 to 95 ° C, preferably between 75 and 85 ° C.
  • the concentration of sulfuric acid is between 200 and 500 g / l, preferably between 300 and 400 g / l.
  • the pretreatment with sulfuric acid is between 5 and 30% of the total treatment time, and the pickling in neutral electrolyte is between 25 and 50% of the total treatment time.
  • the advantage of the three-stage pickling process according to the invention is that it can be used both for austenitic (AISI 304 and 316) and for ferritic stainless steel grades (AISI 430) and the pickling time is greatly reduced for both stainless steel grades.
  • the short pretreatment of the stainless steel according to the invention with preferably dilute sulfuric acid before entering the neutral electrolyte can reduce the pickling time in the neutral electrolyte and in the subsequent mixed acid, as a result of which a substantial increase in performance is achieved in the existing systems with the same space requirement.
  • newly designed systems with the same performance as existing systems can be dimensioned much smaller and therefore economically more economical and cost-saving.
  • the pickling effect can also be improved in the process according to the invention by brushing the pickled material between the individual treatments.
  • Brushing can take place either between the pretreatment with sulfuric acid and the neutral electrolyte stain, between neutral electrolyte stain and the aftertreatment in mixed acid or on both occasions as well as in the rinse after the treatment with mixed acid. This brushing has no effect on the pickling time, but reduces the acid consumption because loosely adhering scale is removed.
  • a stainless steel hot strip of quality AISI 304, 3.1 mm thick was initially in sulfuric acid, with a concentration of 350g / l a temperature of 85 ° C, and then in mixed acid with a concentration of 25g / l HF and 150 g / l HNO3, at a temperature of 55 ° C, pickling, the pickling time a total of 180 sec. and the ratio of pickling times 2: 1 was.
  • neutral electrolyte here Na2SO4 with a concentration of 150 g / l
  • the pickling time could be reduced to 120 seconds, the ratio of the treatment times now being 1: 1.
  • the polarization of the band changed from anodic, with a current density of 10A / dm2, to cathodic, with 20A / dm2, and then back to anodic with 10A / dm2.
  • the temperature of the neutral electrolytes was 80 ° C. After installing a sulfuric acid pretreatment stage, the subsequent pickling time in the neutral electrolyte could be shortened and the total pickling time reduced to a total of 90 seconds, the ratio of the pickling times in the individual steps now being 1: 2: 4.
  • the concentrations and temperatures also corresponded to the values given above in the method according to the invention.
  • a stainless steel hot strip of quality AISI 316 L, 6 mm thick was subjected to the same three pickling processes as in exemplary embodiment 1, with the same process parameters.
  • the pickling time could be reduced from 360 seconds in sulfuric acid and mixed acid to 240 seconds in neutral electrolyte and mixed acid and further to 140 seconds in the case of pretreatment with sulfuric acid stain with neutral electrolyte and aftertreatment with mixed acid.
  • the pickling times for the first two pickling processes were each about 270 seconds.
  • the treatment time could be reduced to 210 seconds.

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)
  • Heat Treatment Of Steel (AREA)
  • Treatment Of Steel In Its Molten State (AREA)
  • Heat Treatment Of Strip Materials And Filament Materials (AREA)
  • Chemical Treatment Of Metals (AREA)
EP91890156A 1990-07-27 1991-07-17 Verfahren zum Beizen von Edelstahl Expired - Lifetime EP0471662B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AT1579/90 1990-07-27
AT0157990A AT395601B (de) 1990-07-27 1990-07-27 Verfahren zum beizen von edelstahl

Publications (3)

Publication Number Publication Date
EP0471662A2 EP0471662A2 (de) 1992-02-19
EP0471662A3 EP0471662A3 (en) 1992-05-20
EP0471662B1 true EP0471662B1 (de) 1995-09-13

Family

ID=3516469

Family Applications (1)

Application Number Title Priority Date Filing Date
EP91890156A Expired - Lifetime EP0471662B1 (de) 1990-07-27 1991-07-17 Verfahren zum Beizen von Edelstahl

Country Status (10)

Country Link
US (1) US5130000A (es)
EP (1) EP0471662B1 (es)
JP (1) JP2721053B2 (es)
KR (1) KR100218840B1 (es)
AT (2) AT395601B (es)
DE (1) DE59106467D1 (es)
ES (1) ES2079634T3 (es)
RU (1) RU2085616C1 (es)
UA (1) UA25894A1 (es)
ZA (1) ZA915877B (es)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT402737B (de) * 1992-04-29 1997-08-25 Andritz Patentverwaltung Verfahren zum diskontinuierlichen beizen von metallischen platten, insbesondere aus edelstahl
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
KR20080048148A (ko) * 2006-11-28 2008-06-02 주식회사 한울로보틱스 로봇의 터치 스크린 보호장치
BR112014007132A2 (pt) 2011-09-26 2017-04-04 Ak Steel Properties Inc decapagem de aço inoxidável em um banho de ácido ele-trolítico, oxidante
CN104593857A (zh) * 2014-12-16 2015-05-06 张家港浦项不锈钢有限公司 铁素体不锈钢加工方法
RU2578623C1 (ru) * 2014-12-30 2016-03-27 Публичное акционерное общество "Ашинский металлургический завод" Способ электролитической очистки от окалины ленточного проката
CN109267142A (zh) * 2018-09-26 2019-01-25 中国民航大学 一种沉淀硬化型不锈钢常温电解酸洗方法

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5550468A (en) * 1978-10-11 1980-04-12 Kawasaki Steel Corp Pickling method for cr base stainless steel
US4415415A (en) * 1982-11-24 1983-11-15 Allegheny Ludlum Steel Corporation Method of controlling oxide scale formation and descaling thereof from metal articles
JPS61266588A (ja) * 1985-05-22 1986-11-26 Nisshin Steel Co Ltd ステンレス鋼の脱スケ−ル方法
AT387406B (de) * 1987-05-07 1989-01-25 Andritz Ag Maschf Verfahren zum elektrolytischen beizen von chromhaeltigem edelstahl
JPS63295011A (ja) * 1987-05-26 1988-12-01 Nisshin Steel Co Ltd ステンレス鋼の脱スケ−ル装置
JPH0759759B2 (ja) * 1988-10-29 1995-06-28 株式会社日立製作所 焼鈍されたステンレス鋼帯の脱スケール方法及び装置

Also Published As

Publication number Publication date
JPH04232299A (ja) 1992-08-20
UA25894A1 (uk) 1999-02-26
KR100218840B1 (ko) 1999-09-01
ATE127866T1 (de) 1995-09-15
EP0471662A3 (en) 1992-05-20
ES2079634T3 (es) 1996-01-16
RU2085616C1 (ru) 1997-07-27
AT395601B (de) 1993-02-25
ATA157990A (de) 1992-06-15
EP0471662A2 (de) 1992-02-19
JP2721053B2 (ja) 1998-03-04
US5130000A (en) 1992-07-14
KR920002826A (ko) 1992-02-28
ZA915877B (en) 1992-04-29
DE59106467D1 (de) 1995-10-19

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