EP0077926B1 - Process to suppress surface deposits during salt bath nitriding of structural parts - Google Patents

Process to suppress surface deposits during salt bath nitriding of structural parts Download PDF

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Publication number
EP0077926B1
EP0077926B1 EP82108892A EP82108892A EP0077926B1 EP 0077926 B1 EP0077926 B1 EP 0077926B1 EP 82108892 A EP82108892 A EP 82108892A EP 82108892 A EP82108892 A EP 82108892A EP 0077926 B1 EP0077926 B1 EP 0077926B1
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EP
European Patent Office
Prior art keywords
nitriding
salt bath
bath
selenium
iron
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
EP82108892A
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German (de)
French (fr)
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EP0077926A1 (en
Inventor
Johannes Dr. Müller
Helmut Dr. Kunst
Christian Scondo
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Evonik Operations GmbH
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Degussa GmbH
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Publication of EP0077926A1 publication Critical patent/EP0077926A1/en
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    • 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
    • C23C8/42—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 only one element being applied
    • C23C8/48—Nitriding
    • C23C8/50—Nitriding of ferrous surfaces

Abstract

Low cyanide nitriding salt baths which are composed of alkali cyanate and alkali carbonate and used for treating components made of steel and iron produce coatings on the surface of the component in some cases and can lead to problems in the use of the components. A satisfactory surface quality can be obtained from nitriding salt baths which additionally contain 0.5 to 100 ppm of selenium.

Description

Die Erfindung betrifft ein Verfahren zur Unterdrückung von schädlichen Oberflächenbelägen beim Salzbad nitrieren auf Bauteilen aus Stahl und Eisen.The invention relates to a method for suppressing harmful surface coverings in the salt bath nitriding on components made of steel and iron.

Das Salzbadnitrieren wird heute weltweit angewandt, um die Verschleißeigenschaft und die Dauerfestigkeit von Bauteilen aus Stahl und Eisen zu verbessern. Auch zur Verbesserung der Korrosionsbeständigkeit von Bauteiloberflächen aus Stahl und Eisen findet das Salzbadverfahren mehr und mehr Anwendungen, wobei die Entwicklung eines speziellen Salzbades zum Abkühlen derTeile nach dem Nitrieren (DE-A-2 934 113) dazu geführt hat, daß die der Nitrierverbindungsschicht eigenen Korrosionseigenschaften noch deutlich verbessert werden können. Damit gewinnt das Verfahren der Salzbadnitrierung große Bedeutung auch für Anwendungsgebiete, wo ansonsten die Verwendung des selten und teuren Chroms erforderlich ist.Salt bath nitriding is used today worldwide to improve the wear properties and fatigue strength of components made of steel and iron. The salt bath process is also used more and more to improve the corrosion resistance of component surfaces made of steel and iron, whereby the development of a special salt bath for cooling the parts after nitriding (DE-A-2 934 113) has led to the corrosion properties inherent in the nitriding compound layer can still be significantly improved. This means that the process of salt bath nitriding is also of great importance for areas of application where the use of the rare and expensive chromium is otherwise required.

Ursprünglich wurden zum Zwecke des Salzbadnitrierens Bäder verwendet, die hohe Anteile an Cyanid enthielten. Das zum Nitrieren notwendige Cyanat wurde durch Belüftung erzeugt, außerdem wurden diese Bäder in Titantiegeln betrieben.Baths containing high levels of cyanide were originally used for the purpose of salt bath nitriding. The cyanate required for nitriding was generated by aeration, and these baths were also operated in titanium crucibles.

Die steigenden Anforderungen an möglichst niedrige Umweltbelastung haben dazu geführt, daß die hochcyanidhaltigen Salzbäder durch praktisch cyanidfreie Bäder ersetzt worden sind, bei denen zudem das Regenerieren der Bäder mit Hilfe eines organischen Stoffes erfolgt, womit die Bildung von giftigen Altsalzen vermieden werden kann (DE-A-2 310 815).The increasing demands for the lowest possible environmental impact have led to the fact that the high-cyanide salt baths have been replaced by practically cyanide-free baths, in which the baths are also regenerated with the help of an organic substance, with which the formation of toxic old salts can be avoided (DE-A -2 310 815).

Da Cyanide in Nitrierbädern bei Temperaturen zwischen 550° C und 650° C stark reduzierend wirken, Cyanate andererseits eher dazu tendieren, Sauerstoff abzugeben, zeigen die nur wenig Cyanid enthaltenden Nitrierbäder die Tendenz, gelegentlich die Nitrierverbindungsschicht derart stark zu oxidieren, daß auch nach dem Abkühlen und Waschen der Bauteile auf der Oberfläche ein schwer zu entfernender, staubförmiger Belag zurückbleibt. Oft sind solche Beläge für die Weiterverwendung des nitrierten Bauteiles nicht akteptabel, da sie z. B. bei Hydraulikaggregaten in den Ölstrom gelangen und an empfindlichen Stellen, z. B. an Lagern, zu abrasivem Verschleiß führen können. Um derartige Effekte zu vermeiden, ist oft ein zeitaufwendiges Reinigen der Teile notwendig.Since cyanides in nitriding baths have a strongly reducing effect at temperatures between 550 ° C and 650 ° C, on the other hand cyanates tend to give off oxygen, the nitriding baths containing little cyanide tend to occasionally oxidize the nitriding compound layer so strongly that even after cooling and washing the components on the surface leaves a difficult to remove, dust-like coating. Such coverings are often not acceptable for further use of the nitrided component, since they are e.g. B. in hydraulic units in the oil flow and at sensitive points, for. B. on bearings, can lead to abrasive wear. In order to avoid such effects, time-consuming cleaning of the parts is often necessary.

Außerdem kann es zur Bildung von rostroten Oberflächenbelägen kommen, wenn Bauteile, die in einem derartigen Nitrierbad behandelt wurden, in ein Abkühlbad übergeführt werden.In addition, rust-red surface deposits can form if components which have been treated in such a nitriding bath are transferred to a cooling bath.

Ein Nitrierbad, das sich in einem für die Oberflächenqualität der nitrierten Bauteile schädlichen, oxidierenden Zustand befindet, ist u. a., dadurch charakterisiert, daß eine Stahlfolie aus einem Stahl mit 0,05% Kohlenstoff nach einer Behandlungsdauer von 90 Minuten einen Gewichtsverlust in der Größenordnung von bis zu einigen 100 mg/dm2 zeigt, die Behandlung der gleichen Stahlfolie unter Bedingungen, die die Bildung von Belägen verhindert, zu einer Gewichtszunahme bis zu ca. 70 mg/dm2 führt. Es ist bisher jedoch nicht möglich vorauszubestimmen, wann ein Bad gute und wann es nicht akzeptable Ergebnisse im Hinblick auf Oberflächensauberkeit hervorruft.A nitriding bath which is in an oxidizing state which is detrimental to the surface quality of the nitrided components is characterized, inter alia, in that a steel foil made of a steel with 0.05% carbon has a weight loss of the order of magnitude after a treatment time of 90 minutes to some 100 mg / dm 2 shows that treating the same steel foil under conditions that prevent the formation of deposits leads to a weight gain of up to approx. 70 mg / dm 2 . So far, however, it has not been possible to predict when a bathroom will produce good and unacceptable results in terms of surface cleanliness.

Solche Salzbäder mußten bisher auf umständlicher und kostenintensiver Weise durch Hochheizen und Entschlammen soweit regeneriert werden, daß sie wieder gute Ergebnisse in bezug auf die Oberflächensauberkeit der nitrierten Bauteile aufwiesen. Diese günstigen Eigenschaften zeigten die so regenerierten Salzbäder jedoch nur relativ kurze Zeit und mußten dann entweder erneut regeneriert oder neu angesetzt werden.Until now, such salt baths had to be regenerated in a cumbersome and cost-intensive manner by heating and desludging to such an extent that they again had good results with regard to the surface cleanliness of the nitrided components. However, the salt baths regenerated in this way showed these favorable properties only for a relatively short time and then either had to be regenerated again or prepared again.

Die CH-A-359 339 beschreibt Salzbäder, mit denen sich die Verschleißfestigkeit der Oberfläche verbessern läßt. Diese Bäder enthalten 20 bis 30% Alkalicyanid, 15 bis 50% Alkalicyanat, Alkalichloride, Alkalicarbonate und 0,1 bis 5% Selen oder Tellur. Selen und Tellur dringen dabei in die Oberflächenschicht ein und bewirken eine hohe Widerstandsfähigkeit gegen Verschleiß. Die Bildung von schädlichen Oberflächenschichten können diese Bäder aber nicht verhindern.CH-A-359 339 describes salt baths with which the wear resistance of the surface can be improved. These baths contain 20 to 30% alkali cyanide, 15 to 50% alkali cyanate, alkali chlorides, alkali carbonates and 0.1 to 5% selenium or tellurium. Selenium and tellurium penetrate into the surface layer and have a high resistance to wear. These baths cannot prevent the formation of harmful surface layers.

Es war daher Aufgabe der vorliegenden Erfindung, ein Verfahren zur Unterdrückung von schädlichen Oberflächenschichten beim Salzbadnitrieren von Bauteilen aus Stahl und Eisen zu schaffen.It was therefore an object of the present invention to provide a method for suppressing harmful surface layers during salt bath nitriding of components made of steel and iron.

Diese Aufgabe wurde erfindungsgemäß dadurch gelöst, daß zum Nitrieren ein Salzbad aus 0,01 bis 3% Cyanid in Form von Alkalicyanid, 25-45% Cyanat in Form von Alkalicyanat, 0,5 bis 100 ppm Selen in Form von Selenverbindungen und/oder elementarem Selen, Rest Alkalicarbonat, verwendet wird.This object was achieved in that for nitriding a salt bath of 0.01 to 3% cyanide in the form of alkali cyanide, 25-45% cyanate in the form of alkali cyanate, 0.5 to 100 ppm selenium in the form of selenium compounds and / or elemental Selenium, balance alkali carbonate, is used.

Das Selen bzw. die Selenverbindungen können dabei dem flüssigen Salzbad direkt zugesetzt werden, oder man verwendet beim Einschmelzen des Bades Salze, denen bereits während ihrer Herstellung entsprechende Mengen Selen beigegeben wurden.The selenium or selenium compounds can be added directly to the liquid salt bath, or salts are used to melt the bath, to which appropriate amounts of selenium have already been added during their production.

Vorzugsweise liegt die Badtemperatur zwischen 550 und 650° C.The bath temperature is preferably between 550 and 650 ° C.

Außerdem verwendet man vorteilhafterweise einen Salzbadtiegel, der möglichst eisenfrei ist. Bewährt haben sich dabei Tiegel aus Titan oder aus nahezu eisenfreien Chrom-Nickel-Legierungen, die allerdings auch bis zu 10 Gew.-% Eisen enthalten können.In addition, it is advantageous to use a salt bath crucible that is as free of iron as possible. Crucibles made from titanium or from virtually iron-free chromium-nickel alloys have proven successful, although they can also contain up to 10% by weight of iron.

Die erfindungsgemäßen Gehalte an Selen oder Selenverbindungen verhindern in den Nitriersalzbädern nachhaltig die Bildung von Belägen auf der Oberfläche der nitrierten Bauteile.The contents of selenium or selenium compounds according to the invention permanently prevent the formation of deposits on the surface of the nitrided components in the nitriding salt baths.

Folgende Beispiele sollen das erfindungsgemäße Verfahren näher erläutern:The following examples are intended to explain the process according to the invention in more detail:

Beispiel 1example 1

Ein umweltfreundliches, cyanidarmes Nitrierbad wird in einem elektrisch beheizten Ofen in einem Titantiegel mit den Abmessungen 35/ 70 cm betrieben. Das Bad hatte folgende Zusammensetzung: 38% CNO-, 0,5% CN-, etwa 15% Carbonat, Rest Natrium und Kalium.An environmentally friendly, low-cyanide nitriding bath is operated in an electrically heated furnace in a titanium crucible with the dimensions 35/70 cm. The bath had the following composition: 38% CNO-, 0.5% CN-, about 15% carbonate, balance sodium and potassium.

Eine Stahlfolie mit einem Kohlenstoffgehalt von 0,05%, 90 Minuten in diesem Bad behandelt und in Wasser abgekühlt, zeigte einen Gewichtsverlust von 185 mg/dm2. Zu gleicher Zeit behandelte Bauteile aus Stahl wiesen an der Oberfläche einen schwarzen abwischbaren Belag auf.A steel foil with a carbon content of 0.05%, treated in this bath for 90 minutes and cooled in water, showed a weight loss of 185 mg / dm 2. Steel components treated at the same time had a black wipeable coating on the surface.

Dem Bad wurden dann mit Hilfe eines Löffels ca. 1,44 g SeOz zugesetzt (d. H. bei 85 kg Salzinhalt entsprechend 12 ppm).About 1.44 g of SeOz was then added to the bath using a spoon (i.e. with 85 kg salt content corresponding to 12 ppm).

Eine nach dem Selenzusatz wie oben durchgeführte Probe ergab bei der Folie eine Gewichtszunahme um 51 mg/dm2. Gleichzeitig mitbehandelte Bauteile aus Stahl hatten eine hellgraue, völlig belagfreie Oberfläche. Die günstige Wirkung dieses Selenzusatzes hält für viele Wochen an.A sample carried out after the selenium addition as above resulted in a weight gain of 51 mg / dm 2 for the film . At the same time, components made of steel had a light gray, completely deposit-free surface. The beneficial effects of this selenium additive last for many weeks.

Beispiel 2Example 2

Einem Nitriersalzbad gemäß Beispiel 1, welches sich in einem Zustand befindet, der durch einen Gewichtsverlust der Stahlfolie gekennzeichnet ist, werden 1,86 g Natriumselenit zugesetzt. Die daraufhin behandelten Folien zeigen eine Gewichtszunahme, die behandelten Bauteile weisen ebenfalls eine saubere Oberfläche auf.1.86 g of sodium selenite are added to a nitriding salt bath according to Example 1, which is in a state which is characterized by a loss in weight of the steel foil. The films subsequently treated show an increase in weight, and the treated components also have a clean surface.

Beispiel 3Example 3

Einer Produktionscharge von 1 t des obengenannten Salzes werden 14,4 g Selendioxid zugesetzt. Bei der Verwendung eines solchen Salzes im praktischen Betrieb kommt es in keinem Falle mehr zum Auftreten von Badzuständen, die durch Gewichtsverluste an einer Stahlfolie gekennzeichnet sind.14.4 g of selenium dioxide are added to a production batch of 1 t of the salt mentioned above. When such a salt is used in practical operation, bath conditions characterized by weight losses on a steel foil no longer occur.

Claims (3)

1. A process for suppressing harmful surface coating during salt bath nitriding of building parts consisting of iron and steel, characterised in that a salt bath is used for nitriding which consists of from 0.01 to 3% of cynanide in the form of alkali metal cyanide, from 25 to 45% cyanate in the form of alkali metal cyanate, from 0.5 to 100 ppm selenium in the form of selenium compounds and/or elementary selenium and the remainder alkali metal carbonate.
2. A process according to claim 1, characterised in that the temperature of the bath is from 550 to 650° C.
3. A process according to claims 1 and 2, characterised in that the bath is operated in a crucible of titanium or an almost iron-free chronium- nickel alloy.
EP82108892A 1981-10-24 1982-09-25 Process to suppress surface deposits during salt bath nitriding of structural parts Expired EP0077926B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19813142318 DE3142318A1 (en) 1981-10-24 1981-10-24 SALT BATH FOR NITRATING IRON MATERIALS
DE3142318 1981-10-24

Publications (2)

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EP0077926A1 EP0077926A1 (en) 1983-05-04
EP0077926B1 true EP0077926B1 (en) 1985-12-04

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US (1) US4492604A (en)
EP (1) EP0077926B1 (en)
JP (1) JPS5877567A (en)
AT (1) ATE16821T1 (en)
AU (1) AU555316B2 (en)
BR (1) BR8206180A (en)
CA (1) CA1208527A (en)
DE (2) DE3142318A1 (en)
DK (1) DK156491C (en)
EG (1) EG15636A (en)
ES (1) ES516409A0 (en)
FI (1) FI70053C (en)
HU (1) HU188217B (en)
IN (1) IN155704B (en)
PT (1) PT75706B (en)
RO (1) RO85594B (en)
TR (1) TR21943A (en)
YU (1) YU43102B (en)
ZA (1) ZA826635B (en)

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DE3403463A1 (en) * 1984-02-01 1985-08-08 Kraftwerk Union AG, 4330 Mülheim MATERIAL MATERIALS FOR HIGH-LOADED MACHINE ELEMENTS
US5707460A (en) * 1995-07-11 1998-01-13 Porter-Cable Corporation Method of producing parts having improved wear, fatigue and corrosion resistance from medium alloy, low carbon steel and parts obtained therefrom
DE60042630D1 (en) * 1999-05-28 2009-09-10 Honda Motor Co Ltd Process for producing laminated rings and molten salt composition for use in this process
US6645566B2 (en) * 1999-06-01 2003-11-11 Jong Ho Ko Process for heat treatment nitriding in the presence of titanium and products produced thereby
JP2003502085A (en) * 1999-06-14 2003-01-21 コーニンクレッカ フィリップス エレクトロニクス エヌ ヴィ MRI apparatus having anti-jamming supply leads for electrically connected equipment
US6746546B2 (en) * 2001-11-02 2004-06-08 Kolene Corporation Low temperature nitriding salt and method of use
KR100513563B1 (en) * 2002-05-21 2005-09-09 고종호 A process for Heat treatment by Nitriding of base metals in the presence of Titanium
US20070013279A1 (en) * 2004-03-23 2007-01-18 Macmillan Michael Bathroom cabinet and method of installation
JP4943018B2 (en) * 2006-02-23 2012-05-30 ヤマハリビングテック株式会社 Bathroom mirror and bathroom mirror mounting structure
US7438769B2 (en) * 2006-04-18 2008-10-21 Philos Jongho Ko Process for diffusing titanium and nitride into a material having a coating thereon
US7732014B2 (en) 2006-04-18 2010-06-08 Philos Jongho Ko Process for diffusing titanium and nitride into a material having a generally compact, granular microstructure
FR2972459B1 (en) 2011-03-11 2013-04-12 Hydromecanique & Frottement FOUNDED SALT BATHS FOR NITRIDING STEEL MECHANICAL PARTS, AND METHOD FOR IMPLEMENTING THE SAME
CN103122446A (en) * 2013-02-02 2013-05-29 大连经济技术开发区圣洁真空技术开发有限公司 Quantitative titanium nitriding carbonitriding technique
CN103882370A (en) * 2014-03-24 2014-06-25 合肥美桥汽车传动及底盘系统有限公司 42CrMo or 40Cr steering knuckle nitrocarburizing treatment process

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DE2934113C2 (en) * 1979-08-23 1985-05-09 Degussa Ag, 6000 Frankfurt Process for increasing the corrosion resistance of nitrided components made of ferrous materials

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Publication number Publication date
ATE16821T1 (en) 1985-12-15
FI70053B (en) 1986-01-31
DE3267827D1 (en) 1986-01-16
RO85594B (en) 1985-03-30
ZA826635B (en) 1983-07-27
TR21943A (en) 1985-11-28
FI823106L (en) 1983-04-25
PT75706B (en) 1985-06-28
YU237482A (en) 1985-03-20
DK156491C (en) 1990-02-12
AU555316B2 (en) 1986-09-18
ES8401531A1 (en) 1983-12-01
DK470282A (en) 1983-04-25
RO85594A (en) 1985-03-15
JPS5877567A (en) 1983-05-10
JPH0217622B2 (en) 1990-04-23
EP0077926A1 (en) 1983-05-04
US4492604A (en) 1985-01-08
EG15636A (en) 1989-01-30
FI823106A0 (en) 1982-09-08
ES516409A0 (en) 1983-12-01
DK156491B (en) 1989-08-28
DE3142318A1 (en) 1983-05-05
BR8206180A (en) 1983-09-20
HU188217B (en) 1986-03-28
YU43102B (en) 1989-02-28
IN155704B (en) 1985-02-23
CA1208527A (en) 1986-07-29
FI70053C (en) 1986-09-12
PT75706A (en) 1982-11-01
AU8841182A (en) 1983-04-28

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