EP0974680B1 - Process for the electrolytic production of cyanide in nitrocarburizing molten baths - Google Patents

Process for the electrolytic production of cyanide in nitrocarburizing molten baths Download PDF

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Publication number
EP0974680B1
EP0974680B1 EP99112333A EP99112333A EP0974680B1 EP 0974680 B1 EP0974680 B1 EP 0974680B1 EP 99112333 A EP99112333 A EP 99112333A EP 99112333 A EP99112333 A EP 99112333A EP 0974680 B1 EP0974680 B1 EP 0974680B1
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Prior art keywords
cyanide
nitrocarburizing
melts
production
cyanate
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EP99112333A
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German (de)
French (fr)
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EP0974680A1 (en
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Ulrich Dr. Baudis
Mandy Doose
Karl-Otto Prof. Prietzel
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Durferrit GmbH Thermotechnik
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Durferrit GmbH Thermotechnik
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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
    • C23C8/52—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 more than one element being applied in one step
    • C23C8/54—Carbo-nitriding
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals

Definitions

  • the invention relates to a method for electrolytic Production of cyanide in molten salts which cyanate and optionally contain carbonate and which to Nitrocarburizing steel are provided.
  • the usage behavior of components is largely determined by determines the behavior of the component surface. To increase the wear and corrosion resistance as well as the The nitriding or Nitrocarburizing of steel applied industrially.
  • the Salt bath technology plays an important role in this on.
  • the main components of these salt baths are the cyanates and carbonates of the alkali metals potassium and sodium.
  • Electrolysis is carried out in the cyanate-containing nitrocarburizing melt.
  • Both the crucible used and electrode sheets made of suitable metal or metal alloys introduced into the bath can be used as electrodes.
  • Corrosion-resistant materials such as, in particular, titanium or nickel materials and high-chromium steels, tantalum or graphite are provided as electrode materials.
  • the electrodes each consist of a sheet metal with a welded-on electrode rod of the same material. The surface of the sheets need only be roughly ground. Finishing is advantageous but not necessary. A rectifier is used as the current source.
  • the nitriding salt melt is electrolyzed with a current density of 4 to 100 A / dm 2 over a period of 1 to 12 hours at temperatures between 450 and 650 ° C.
  • a cyanide content of 1 to 5% by weight, preferably 2 to 4% by weight, is generated.
  • the nitrocarburizing salt is added without cyanide salts melted down.
  • the electrodes in the Crucible hung in, over copper lines with the Rectifier connected and the desired current set.
  • the control of the cyanide and cyanate content takes place via the usual determination methods.
  • Figure 1 shows schematically the experimental setup used.
  • The is in a crucible (1) Nitrocarburizing melt (2).
  • Nitrocarburizing melt (2) There are two in the melt (2) sheets (3, 3 ') which act as electrodes and which have a welded round rod are provided as power supply lines, hooked in using the brackets (4, 4 '). About the Round bars are supplied with electricity (5).

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  • Chemical & Material Sciences (AREA)
  • Metallurgy (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Electrochemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Electrolytic Production Of Metals (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)

Abstract

In order to shorten the waiting times until the equilibrium between cyanate and cyanide is established and to limit the use of substances and products containing cyanide for nitrocarburizing in salt melts, melts containing only cyanate and optionally carbonate are electrolyzed at a current density of 4 to 100 A/dm2 of electrode area to form an advantageous cyanide content of 1 to 5 wt. %.

Description

Die Erfindung betrifft ein Verfahren zur elektrolytischen Erzeugung von Cyanid in Salzschmelzen welche Cyanat und gegebenenfalls Carbonat enthalten und welche zum Nitrocarburieren von Stahl vorgesehen sind.The invention relates to a method for electrolytic Production of cyanide in molten salts which cyanate and optionally contain carbonate and which to Nitrocarburizing steel are provided.

Das Gebrauchsverhalten von Bauteilen wird maßgeblich durch das Verhalten der Bauteiloberfläche bestimmt. Zur Erhöhung des Verschleiß- und Korrosionswiderstandes sowie der Dauerfestigkeit wird seit langem das Nitrieren bzw. Nitrocarburieren von Stahl industriell angewendet. Die Salzbadtechnologie nimmt dabei eine bedeutende Stellung ein. Die Hauptkomponenten dieser Salzbäder sind die Cyanate und Carbonate der Alkalimetalle Kalium und Natrium.The usage behavior of components is largely determined by determines the behavior of the component surface. To increase the wear and corrosion resistance as well as the The nitriding or Nitrocarburizing of steel applied industrially. The Salt bath technology plays an important role in this on. The main components of these salt baths are the cyanates and carbonates of the alkali metals potassium and sodium.

Es sind bisher einige Patente bekannt, wie z.B. FR 9309706 oder US-Patent 5,518,605, die sich mit der Durchführung von Elektrolysen in Nitriersalzschmelzen beschäftigen. Diese Erfindungen betreffen aber einzig und allein die Verbesserung der nitrocarburierten Oberfläche von Bauteilen. Die Bauteile bzw. Chargen selbst werden dabei anodisch oder kathodisch geschaltet. Weiterhin sind Patente zur Badkontrolle solcher Schmelzen, wie z.B. DE 24 13 643 oder DE 25 29 412, unter Ausnutzung elektrochemischer Potentialmessung mit verschiedensten Elektroden geläufig.Some patents are known, e.g. FR 9309706 or US Patent 5,518,605, which deals with the implementation of Employ electrolysis in nitriding salt melts. This However, inventions only concern those Improvement of the nitrocarburized surface of Components. The components or batches themselves are included switched anodically or cathodically. There are also patents for bath control of such melts, e.g. DE 24 13 643 or DE 25 29 412, using electrochemical Potential measurement with various electrodes common.

Ein Verfahren zur gezielten Herstellung von Cyanid durch Elektrolyse aus den Bestandteilen der Nitrocarburierschmelzen ist demgegenüber bislang nicht bekannt. Im Gegenteil, viele Verfahrensvarianten der Salzbadnitrocarburierung zielen aus Umwelt- und Arbeitssicherheitsgründen darauf ab, Cyanide in diesen Schmelzen zu vermeiden. Die Grundlage der vorliegenden Erfindung ist demgegenüber die Erkenntnis, daß zur Erzielung optimaler Gebrauchsfähigkeit (Verschleißminderung, Korrosionsschutz) der nitrierten Bauteile eine gewisse Menge an Cyanid in den Nitrocarburierschmelzen von großem Vorteil ist. Nun ist es seit langem gängige Praxis, Nitrocarburierschmelzen cyanidfrei einzuschmelzen, weil die Produkte auf diese Weise ungefährlich transportiert und gelagert werden können. Die heute üblicherweise benutzten Einschmelzsalze und Nachfüllsalze sind völlig cyanidfrei. Das für eine optimale Nitrierung vorteilhafte Cyanid bildet sich erst im Laufe einiger Tage bei Betriebstemperatur durch allmählichen Zerfall des Cyanats bis zur Einstellung eines Gleichgewichtes gemäß der Reaktion: OCN-  CN- + ½ O2 In contrast, a process for the targeted production of cyanide by electrolysis from the constituents of the nitrocarburizing melts is not known. On the contrary, many process variants of salt bath nitrocarburization aim to avoid cyanides in these melts for environmental and occupational safety reasons. In contrast, the basis of the present invention is the knowledge that a certain amount of cyanide in the nitrocarburizing melts is of great advantage in order to achieve optimum usability (wear reduction, corrosion protection). It has long been common practice to melt nitrocarburizing melts free of cyanide, because in this way the products can be transported and stored safely. The melting salts and refill salts that are commonly used today are completely cyanide-free. The cyanide, which is advantageous for optimal nitration, only forms in the course of a few days at operating temperature through gradual decomposition of the cyanate until equilibrium is established according to the reaction: OCN -  CN - + ½ O 2

Zur Verkürzung der Wartezeiten bis zur Gleichgewichtseinstellung besteht die Möglichkeit, Cyanid in Form von Kalium- und Natriumcyanid nachträglich zuzugeben oder beim Einschmelzen bzw. mit dem Nachfüllsalz einzuschmelzen. Das größte Problem stellen dabei der Transport, die Lagerung und das Handling der cyanidhaltigen Produkten dar. Bisweilen wird auch versucht, durch Zugabe von Eisenspänen oder Einfahren von Schrott mit hoher spezifischer Oberfläche die Gleichgewichtseinstellung Cyanat/Cyanid zu beschleunigen. Alles dies ist jedoch keine befriedigende Lösung für das Problem, in kurzer Zeit ein cyanidfrei eingeschmolzenes Nitrierbad mit einem für optimale Resultate erforderlichen Gehalt an Cyanid anzureichern. Derzeit ist keine alternative Möglichkeit bekannt, Cyanid in ausreichender Menge auf anderem Wege in solchen Schmelzen zu erzeugen.To reduce waiting times until Equilibrium is possible, cyanide subsequently in the form of potassium and sodium cyanide add or when melting or with the refill salt melt down. The biggest problem is the Transport, storage and handling of the cyanide Products. Sometimes an attempt is also made by adding of iron shavings or scrap scrap with high specific surface area the equilibrium setting Accelerate cyanate / cyanide. However, all of this is not satisfactory solution to the problem in a short time Nitriding bath melted free of cyanide with a for optimal results required cyanide content to enrich. There is currently no alternative known to cyanide in sufficient quantities in another way to produce such melts.

Es war daher Aufgabe der vorliegenden Erfindung, ein Verfahren zur Erzeugung von Cyanid in Nitrocarburierschmelzen ohne Verwendung cyanidhaltiger Stoffe zu entwickeln, das mit geringem Zeitaufwand durchführbar ist und eine anschließende Nitrocarburierung von Bauteilen nicht beeinträchtigt. It was therefore an object of the present invention Process for the production of cyanide in Nitrocarburizing melts without the use of cyanide Develop fabrics that take up little time is feasible and a subsequent nitrocarburization not affected by components.

Diese Aufgabe wird erfindungsgemäß dadurch gelöst, daß in der cyanathaltigen Nitrocarburierschmelze eine Elektrolyse durchgeführt wird. Als Elektroden können sowohl der eingesetzte Tiegel als auch in das Bad eingeführte Elektrodenbleche aus geeignetem Metall oder Metallegierungen verwendet werden. Als Elektrodenmaterialien sind korrosionsbeständige Werkstoffe wie insbesondere Titan- oder Nickel-Werkstoffe sowie hochchromhaltige Stähle, Tantal oder Graphit vorgesehen Die Elektroden bestehen jeweils aus einem Blech mit angeschweißtem Elektrodenstab des selben Werkstoffes. Die Oberfläche der Bleche braucht nur grob geschliffen zu sein. Eine Feinbearbeitung ist vorteilhaft, aber nicht notwendig. Als Stromquelle wird ein Gleichrichter eingesetzt. Die Nitriersalzschmelze wird mit einer Stromdichte von 4 bis 100 A/dm2 über einen Zeitraum von 1 bis 12 Stunden bei Temperaturen zwischen 450 und 650°C elektrolysiert. Hierbei wird ein Cyanidgehalt von 1 bis 5 Gew.%, vorzugsweise 2 bis 4 Gew.%, erzeugt.This object is achieved in that electrolysis is carried out in the cyanate-containing nitrocarburizing melt. Both the crucible used and electrode sheets made of suitable metal or metal alloys introduced into the bath can be used as electrodes. Corrosion-resistant materials such as, in particular, titanium or nickel materials and high-chromium steels, tantalum or graphite are provided as electrode materials. The electrodes each consist of a sheet metal with a welded-on electrode rod of the same material. The surface of the sheets need only be roughly ground. Finishing is advantageous but not necessary. A rectifier is used as the current source. The nitriding salt melt is electrolyzed with a current density of 4 to 100 A / dm 2 over a period of 1 to 12 hours at temperatures between 450 and 650 ° C. A cyanide content of 1 to 5% by weight, preferably 2 to 4% by weight, is generated.

Zu Beginn wird das Nitrocarburiersalz ohne die Zugabe cyanidischer Salze eingeschmolzen. Nach Einstellung des Cyanatgehaltes auf 36-38 % werden die Elektroden in den Tiegel eingehängt, über Kupferleitungen mit dem Gleichrichter verbunden und der gewünschte Strom eingestellt. Die Kontrolle des Cyanid- und Cyanatgehaltes erfolgt über die üblichen Bestimmungsmethoden.To begin with, the nitrocarburizing salt is added without cyanide salts melted down. After discontinuing the Cyanate content to 36-38%, the electrodes in the Crucible hung in, over copper lines with the Rectifier connected and the desired current set. The control of the cyanide and cyanate content takes place via the usual determination methods.

Figur 1 zeigt schematisch den verwendeten Versuchsaufbau.Figure 1 shows schematically the experimental setup used.

In einem Tiegel (1) befindet sich die Nitrocarburierschmelze (2). In die Schmelze (2) sind zwei als Elektroden fungierende Bleche (3, 3'), die mit einem angeschweißten Rundstab als Stromzuführungen versehen sind, mittels der Halterungen (4, 4') eingehängt. Über die Rundstäbe wird der Strom zugeführt (5). The is in a crucible (1) Nitrocarburizing melt (2). There are two in the melt (2) sheets (3, 3 ') which act as electrodes and which have a welded round rod are provided as power supply lines, hooked in using the brackets (4, 4 '). About the Round bars are supplied with electricity (5).

Die folgenden Beispiele sollen das erfindungsgemäße Verfahren näher erläutern:The following examples are intended to illustrate the invention Explain the procedure in more detail:

Beispiel 1:Example 1:

Es wurden in einem 18/30-Titantiegel (Durchmesser 18 cm, Tiefe 30 cm) 12 kg Nitrocarburiersalz eingeschmolzen. Gearbeitet wurde bei 580 °C Badtemperatur. Als Elektroden wurden zwei Inconel -Bleche (100x200x2 mm) eingesetzt, welche mittels Kupferleitungen von 5 mm Durchmesser an den Gleichrichter angeschlossen waren. Nach Einstellung des Cyanatgehaltes auf 37,0 ± 0,5 % mit Hilfe eines handelsüblichen Regeneratormittels und der Überprüfung des Anfangscyanidgehaltes (< 0,1 % bzw. nicht nachweisbar) wurde mit der Elektrolyse begonnen. Es wurde ein Strom der Stromstärke 70 A, entsprechend einer Stromdichte von ca. 17 A/dm2, eingestellt. Die Elektrolyse lief über einen Zeitraum von 6,5 Stunden. Die Cyanidbestimmung ergab das für dieses Beispiel in Tabelle 1 aufgeführte Ergebnis.12 kg of nitrocarburizing salt were melted in an 18/30 titanium crucible (diameter 18 cm, depth 30 cm). Work was carried out at a bath temperature of 580 ° C. Two Inconel sheets (100x200x2 mm) were used as electrodes, which were connected to the rectifier by means of copper cables with a diameter of 5 mm. After adjusting the cyanate content to 37.0 ± 0.5% using a commercially available regenerator and checking the initial cyanide content (<0.1% or undetectable), the electrolysis was started. A current of 70 A, corresponding to a current density of approximately 17 A / dm 2 , was set. The electrolysis was carried out over a period of 6.5 hours. The cyanide determination gave the result shown in Table 1 for this example.

Beispiel 2:Example 2:

Es wurden wiederum in einem 18/30-Titantiegel 12 kg Nitrocarburiersalz eingeschmolzen. Die Badtemperatur betrug ebenfalls 580 °C. Als Elektroden dienten ein Nickelblech der Abmessungen 100x200x2 mm als Anode und der Titantiegel als Kathode. Die Elektroden waren mittels Kupferleitungen von 5 mm Durchmesser an den Gleichrichter angeschlossen. Nach Einstellung des Cyanatgehaltes auf den Sollwert von 37,0 ± 0,5 % mit Hilfe eines Regeneratormittels und der Überprüfung des Anfangscyanidgehaltes (< 0,1 % bzw. nicht nachweisbar) wurde mit der Elektrolyse begonnen. Es wurde ein Strom der Sromstärke 20 A, entsprechend einer Stromdichte von ca. 4,9 A/dm2,bezogen auf die Anode, aufgebracht. Die Elektrolyse lief über einen Zeitraum von 6 Stunden. Die Cyanidbestimmung ergab das in Tabelle 1 aufgeführte Ergebnis. erzeugte Cyanidgehalte für Beispiel 1 und 2 Versuch Erzeugter Cyanidgehalt zu verschiedenen Versuchszeiten in % 0 h 0,33 h 0,66 h 1,0 h 2,0 h 3,0 h 4,0 h 5,0 h 6,0 h 6,5 h Beispiel 1 Inconel gegen Inconel 0,0 0,3 0,5 0,7 1,3 1,9 2,3 2,7 - 3,2 17,0 A/dm2 Beispiel 2 Nickel gegen Titantiegel 0,0 0,1 0,2 0,3 0,4 0,6 0,8 0,9 1,1 - 4,9 A/dm2 Again, 12 kg of nitrocarburizing salt were melted in an 18/30 titanium crucible. The bath temperature was also 580 ° C. A nickel sheet measuring 100x200x2 mm served as electrodes and the titanium crucible as cathode. The electrodes were connected to the rectifier by means of 5 mm diameter copper lines. After setting the cyanate content to the target value of 37.0 ± 0.5% with the aid of a regenerator and checking the initial cyanide content (<0.1% or undetectable), the electrolysis was started. A current of 20 A current, corresponding to a current density of approximately 4.9 A / dm 2 , based on the anode, was applied. The electrolysis was carried out over a period of 6 hours. The cyanide determination gave the result listed in Table 1. generated cyanide contents for Examples 1 and 2 attempt Cyanide content generated at various test times in% 0 h 0.33 h 0.66 h 1.0 h 2.0 h 3.0 h 4.0 h 5.0 h 6.0 h 6.5 h example 1 Inconel vs. Inconel 0.0 0.3 0.5 0.7 1.3 1.9 2.3 2.7 - 3.2 17.0 A / dm 2 Example 2 Nickel against titanium crucibles 0.0 0.1 0.2 0.3 0.4 0.6 0.8 0.9 1.1 - 4.9 A / dm 2

Die Werte sind in Figur 3 graphisch dargestellt und zeigen, in welchem Umfang sich in einer Nitrocarburier-Schmelze bei Durchführung einer Elektrolyse, in Abhängigkeit von der verwendeten Stromdichte und der Zeit Cyanid bildet. Die Zeit zur Bildung einer bestimmten Menge Cyanid kann durch Erhöhung der Stromdichte verkürzt werden. Günstig ist die Kombination zweier Inconel Bleche als Anode und Kathode. Typisch ist außerdem, daß das eingesetzte Cyanat in etwa doppelter Geschwindigkeit umgesetzt wird, wie in Figur 2 dargestellt ist. Die Bildung von Cyanid erfolgt also zu Lasten des Cyanats. Für eine anschließende Nitrocarburierung wird auf den üblicherweise geeigneten Cyanatgehalt von 35-38 % regeneriert.The values are shown graphically in FIG. 3 and show to what extent in a nitrocarburizing melt Carrying out an electrolysis, depending on the current density used and the time forms cyanide. The It can take time to form a certain amount of cyanide Increasing the current density can be shortened. It is cheap Combination of two Inconel sheets as anode and cathode. It is also typical that the cyanate used is approximately double speed is implemented, as in Figure 2 is shown. The formation of cyanide thus occurs Loads of cyanate. For a subsequent one Nitrocarburizing is usually carried out on the most suitable Cyanate content of 35-38% regenerated.

Im Anschluß an die Elektrolyse durchgeführte Nitrocarburierungen von Bauteilen verschiedener Werkstoffe ergaben, daß die Dicke und der Aufbau der Verbindungsschicht den erwarteten Werten entsprach, die sich ergeben, wenn das Cyanid in Substanz zugegeben worden wäre.Performed after electrolysis Nitrocarburizing of components of different materials revealed that the thickness and structure of the Link layer corresponded to the expected values that result when the cyanide has been added in bulk would.

Claims (6)

  1. Process for nitrocarburisation of components, characterised by the following method steps: production of cyanide in nitrocarburising melts, which contain cyanate, by electrolysis in the melt and subsequent nitrocarburisation of components by means of the nitrocarburising melts containing cyanide.
  2. Process according to claim 1, characterised in that, the cyanide is produced at a current density in the range of 4 to 100 A/dm2 over a period of 1 to 12 hours.
  3. Process according to claim 1 or 2, characterised in that, in the production of cyanide, titanium or nickel materials as well as high-chromium steels, tantalum or graphite are provided as electrode materials.
  4. Process according to one of claims 1 to 3, characterised in that, in the production of cyanide, the melt crucible acts as one of the electrodes.
  5. Process according to one of claims 1 to 4, characterised in that, in the production of cyanide, it is performed at temperatures of between 450 and 650° C.
  6. Process according to one of claims 1 to 5, characterised in that, a cyanide content of 1 to 5 wt.%, preferably of 2 to 4 wt.%, is produced.
EP99112333A 1998-07-18 1999-06-26 Process for the electrolytic production of cyanide in nitrocarburizing molten baths Expired - Lifetime EP0974680B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19832404 1998-07-18
DE19832404A DE19832404C1 (en) 1998-07-18 1998-07-18 Production of cyanide from nitrocarburised melts containing cyanate by electrolysis

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EP0974680A1 EP0974680A1 (en) 2000-01-26
EP0974680B1 true EP0974680B1 (en) 2002-10-09

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EP99112333A Expired - Lifetime EP0974680B1 (en) 1998-07-18 1999-06-26 Process for the electrolytic production of cyanide in nitrocarburizing molten baths

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US (1) US6159355A (en)
EP (1) EP0974680B1 (en)
JP (1) JP2000054109A (en)
AT (1) ATE225869T1 (en)
BR (1) BR9902971A (en)
CA (1) CA2277495A1 (en)
DE (2) DE19832404C1 (en)
ES (1) ES2183462T3 (en)
TR (1) TR199901661A2 (en)
ZA (1) ZA994621B (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1255438B (en) * 1965-04-28 1967-11-30 Degussa Process for nitriding and / or carbonitriding of metals, especially of iron and iron alloys, in fused salt baths containing alkali cyanide and alkali cyanate
ES437450A1 (en) * 1974-05-17 1976-12-01 Stephanois Rech Mec Method of maintaining at very low values the content of cyanide in salt baths containing cyanates
DE2529412A1 (en) * 1975-07-02 1977-01-20 Daimler Benz Ag Nitriding steel in a molten salt bath - controlled by measuring electromotive force between workpiece and a silver electrode in the bath
FR2708623B1 (en) * 1993-08-06 1995-10-20 Stephanois Rech Mec Nitriding process for ferrous metal parts, with improved corrosion resistance.

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TR199901661A2 (en) 2000-02-21
US6159355A (en) 2000-12-12
DE59902998D1 (en) 2002-11-14
EP0974680A1 (en) 2000-01-26
BR9902971A (en) 2000-04-25
CA2277495A1 (en) 2000-01-18
ATE225869T1 (en) 2002-10-15
JP2000054109A (en) 2000-02-22
ES2183462T3 (en) 2003-03-16
DE19832404C1 (en) 1999-10-21
ZA994621B (en) 2000-01-14

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