EP0216067B1 - Procédé et appareil pour l'élimination de nitrite de métal alcalin de bains salins contenant du nitrate - Google Patents

Procédé et appareil pour l'élimination de nitrite de métal alcalin de bains salins contenant du nitrate Download PDF

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Publication number
EP0216067B1
EP0216067B1 EP86110169A EP86110169A EP0216067B1 EP 0216067 B1 EP0216067 B1 EP 0216067B1 EP 86110169 A EP86110169 A EP 86110169A EP 86110169 A EP86110169 A EP 86110169A EP 0216067 B1 EP0216067 B1 EP 0216067B1
Authority
EP
European Patent Office
Prior art keywords
bath
nitrite
nitrate
salt
salt bath
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
Application number
EP86110169A
Other languages
German (de)
English (en)
Other versions
EP0216067A1 (fr
Inventor
Helmut Dr. Kunst
Christian Scondo
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.)
Houghton Durferrit degussa-Huels AG GmbH
Original Assignee
Degussa 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 Degussa GmbH filed Critical Degussa GmbH
Priority to AT86110169T priority Critical patent/ATE43647T1/de
Publication of EP0216067A1 publication Critical patent/EP0216067A1/fr
Application granted granted Critical
Publication of EP0216067B1 publication Critical patent/EP0216067B1/fr
Expired legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/56—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering characterised by the quenching agents
    • C21D1/607—Molten salts
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/34—Methods of heating
    • C21D1/44—Methods of heating in heat-treatment baths
    • C21D1/46—Salt baths
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/40—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using liquids, e.g. salt baths, liquid suspensions

Definitions

  • the invention relates to a method for removing alkali nitrite from nitrate-containing salt baths used for cooling components after nitriding and a corresponding device.
  • DE-PS 2514 398 describes a salt bath for cooling bath nitrided components made of iron and steel, which contains sodium and potassium hydroxide with about 10% alkali nitrate.
  • This salt bath is being used to an increasing extent in industry in order to convert the cyanide and cyanate residues adhering to the bath-nitrided components when they are removed from the nitriding bath and thus to render them harmless.
  • These salt baths became particularly important when it emerged that under changed treatment conditions a significant increase in the corrosion resistance of nitrided components can be achieved.
  • the procedure is usually such that the workpieces remain in the cooling bath operated at a temperature of 330 to 400 ° C. until they have reached its temperature and the detoxification reaction or the anti-corrosion treatment has been completed. Then the workpieces are removed from the cooling bath and cooled in cold water. If the cooling bath contains nitrite, this accumulates in the water used for cooling. Accordingly, this water must also be detoxified. This additional operation can be saved if the formation of the nitrite can be prevented or the nitrite can be destroyed immediately after its formation.
  • nitrite formed in the salt bath is oxidized there to nitrate.
  • air is preferably blown through the bath during the breaks.
  • This bath regeneration is most effective when the air flows through the salt bath in a very fine distribution.
  • This can best be achieved with an annular ventilation pipe, which is attached below the circulation stirrer usually present in such gene conditions.
  • the annular ventilation pipe (4) is provided on the surface facing the circulation stirrer (3) with bores (5) so that the air emerging therefrom is passed directly into the circulation stirrer (3) and is distributed by it in the bath (2), which is in a crucible (1).
  • the amount of air required naturally depends primarily on the amount of nitrite formed and thus on the amount of nitriding salt introduced into the cooling bath, ultimately on the size, shape and amount of the components treated. Arithmetically, this results in an air requirement of approximately 1,625 liters per kg of sodium nitrite to be oxidized. With the device described, a degree of utilization of 60 to 80% is achieved, which is why in practice 2,000 to 2,700 liters of air per kg of sodium nitrite are required.
  • the absolute amount of NaN0 2 formed was 18 kg, the calculated air volume 29,250 liters. Here too, double air volume was used first. However, this large cooling bath had two circulators, so the ventilation was also carried out via two ventilation pipes. 1,220 liters of air were introduced per hour into each ventilation pipe. In this case too, it was found that the nitrite was completely converted after 15 hours, which corresponds to a degree of utilization of almost 80%. The composition of the bath after aeration corresponded to the specified starting composition except for slight differences.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Inorganic Compounds Of Heavy Metals (AREA)
  • Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)

Claims (3)

1. Procédé d'élimination de nitrites alcalins de bains salins utilisés pour le refroidissement de pièces de construction après la nitration, caractérisé en ce que le nitrite formé dans le bain salin est oxydé là en nitrate.
2. Procédé selon la revendication 1, caractérisé en ce que de l'air est soufflé pour l'oxydation des nitrites en nitrates pendant les arrêts de fonctionnement à travers le bain salin.
3. Dispositif pour l'exécution du procédé selon les revendications 1 et 2, consistant en un creuset avec agitateur de révolution, caractérisé en ce qu'un tube d'aération annulaire (4) pourvu d'orifices (5) est appliqué en-dessous de l'agitateur planétaire (3) dans le bain salin (2).
EP86110169A 1985-09-24 1986-07-24 Procédé et appareil pour l'élimination de nitrite de métal alcalin de bains salins contenant du nitrate Expired EP0216067B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT86110169T ATE43647T1 (de) 1985-09-24 1986-07-24 Verfahren und vorrichtung zur entfernung von alkalinitrit aus nitrathaltigen salzbaedern.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3533935 1985-09-24
DE3533935A DE3533935C1 (de) 1985-09-24 1985-09-24 Verfahren und Vorrichtung zur Entfernung von Alkalinitrit aus nitrathaltigen Salzbaedern

Publications (2)

Publication Number Publication Date
EP0216067A1 EP0216067A1 (fr) 1987-04-01
EP0216067B1 true EP0216067B1 (fr) 1989-05-31

Family

ID=6281734

Family Applications (1)

Application Number Title Priority Date Filing Date
EP86110169A Expired EP0216067B1 (fr) 1985-09-24 1986-07-24 Procédé et appareil pour l'élimination de nitrite de métal alcalin de bains salins contenant du nitrate

Country Status (5)

Country Link
US (1) US4717429A (fr)
EP (1) EP0216067B1 (fr)
JP (1) JPH076055B2 (fr)
AT (1) ATE43647T1 (fr)
DE (2) DE3533935C1 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6117249A (en) * 1998-02-13 2000-09-12 Kerk Motion Products, Inc. Treating metallic machine parts
US6746546B2 (en) * 2001-11-02 2004-06-08 Kolene Corporation Low temperature nitriding salt and method of use
SE530783C2 (sv) * 2007-01-16 2008-09-09 Westinghouse Electric Sweden Spridargaller för positinering av bränslestavar

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3793208A (en) * 1973-01-04 1974-02-19 Park Chem Co Method of rectifying commercial salt baths
DE2340405C3 (de) * 1973-08-09 1978-05-03 Ekkehard 7050 Waiblingen Mohr Verfahren zum Aufbereiten von Spiil- und Abwässern aus Salzbadhärtereien
US4149702A (en) * 1976-03-25 1979-04-17 Park Chemical Company Method and apparatus for recycling heat treating salts
DE2930442A1 (de) * 1978-07-29 1980-02-07 Furukawa Electric Co Ltd Abwasserbehandlungsverfahren
DE2852475C2 (de) * 1978-12-05 1980-05-22 Deutsche Gold- Und Silber-Scheideanstalt Vormals Roessler, 6000 Frankfurt Verfahren zur automatisch steuerbaren Entgiftung von Nitritionen enthaltenden Abwässern
JPS5929317B2 (ja) * 1979-05-16 1984-07-19 大阪瓦斯株式会社 廃水処理方法
US4396439A (en) * 1981-08-21 1983-08-02 Park Chemical Company Recovery and recycle of nitrate and nitrite salts from chloride containing quench bath solids
US4568352A (en) * 1984-05-24 1986-02-04 Olin Corporation Alkali metal nitrate purification

Also Published As

Publication number Publication date
DE3533935C1 (de) 1986-06-05
DE3663688D1 (en) 1989-07-06
ATE43647T1 (de) 1989-06-15
JPS6286152A (ja) 1987-04-20
US4717429A (en) 1988-01-05
JPH076055B2 (ja) 1995-01-25
EP0216067A1 (fr) 1987-04-01

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