EP0113474A2 - Regenerator for carburizing salt baths and process for making it - Google Patents
Regenerator for carburizing salt baths and process for making it Download PDFInfo
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- EP0113474A2 EP0113474A2 EP83112965A EP83112965A EP0113474A2 EP 0113474 A2 EP0113474 A2 EP 0113474A2 EP 83112965 A EP83112965 A EP 83112965A EP 83112965 A EP83112965 A EP 83112965A EP 0113474 A2 EP0113474 A2 EP 0113474A2
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- EP
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- Prior art keywords
- regeneration
- salt baths
- baths
- moles
- cyanide
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- 150000003839 salts Chemical class 0.000 title claims abstract description 27
- 238000005255 carburizing Methods 0.000 title claims abstract description 10
- 238000000034 method Methods 0.000 title claims description 9
- 230000008929 regeneration Effects 0.000 claims abstract description 26
- 238000011069 regeneration method Methods 0.000 claims abstract description 26
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 claims abstract description 24
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 22
- 239000000203 mixture Substances 0.000 claims abstract description 16
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 12
- 150000001875 compounds Chemical class 0.000 claims abstract description 8
- 150000002894 organic compounds Chemical class 0.000 claims abstract description 7
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 6
- QGBSISYHAICWAH-UHFFFAOYSA-N dicyandiamide Chemical compound NC(N)=NC#N QGBSISYHAICWAH-UHFFFAOYSA-N 0.000 claims abstract description 6
- 229910052742 iron Inorganic materials 0.000 claims abstract description 6
- 239000010959 steel Substances 0.000 claims abstract description 6
- 229920000877 Melamine resin Polymers 0.000 claims abstract description 3
- JDSHMPZPIAZGSV-UHFFFAOYSA-N melamine Chemical compound NC1=NC(N)=NC(N)=N1 JDSHMPZPIAZGSV-UHFFFAOYSA-N 0.000 claims abstract description 3
- 238000000197 pyrolysis Methods 0.000 claims description 11
- 238000006243 chemical reaction Methods 0.000 claims description 9
- 229920002866 paraformaldehyde Polymers 0.000 claims description 7
- 238000002360 preparation method Methods 0.000 claims description 6
- 229930040373 Paraformaldehyde Natural products 0.000 claims description 5
- 239000007859 condensation product Substances 0.000 claims description 3
- 230000001172 regenerating effect Effects 0.000 claims description 3
- XFXPMWWXUTWYJX-UHFFFAOYSA-N Cyanide Chemical compound N#[C-] XFXPMWWXUTWYJX-UHFFFAOYSA-N 0.000 abstract description 17
- 239000000126 substance Substances 0.000 abstract description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical group [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 abstract description 4
- 238000005121 nitriding Methods 0.000 abstract description 3
- XZMCDFZZKTWFGF-UHFFFAOYSA-N Cyanamide Chemical compound NC#N XZMCDFZZKTWFGF-UHFFFAOYSA-N 0.000 abstract description 2
- 238000010000 carbonizing Methods 0.000 abstract description 2
- 239000006260 foam Substances 0.000 abstract description 2
- 239000007795 chemical reaction product Substances 0.000 abstract 1
- LELOWRISYMNNSU-UHFFFAOYSA-N hydrogen cyanide Chemical compound N#C LELOWRISYMNNSU-UHFFFAOYSA-N 0.000 description 18
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 8
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 7
- MNWBNISUBARLIT-UHFFFAOYSA-N sodium cyanide Chemical compound [Na+].N#[C-] MNWBNISUBARLIT-UHFFFAOYSA-N 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- XLJMAIOERFSOGZ-UHFFFAOYSA-M cyanate Chemical compound [O-]C#N XLJMAIOERFSOGZ-UHFFFAOYSA-M 0.000 description 6
- 235000010299 hexamethylene tetramine Nutrition 0.000 description 6
- VKYKSIONXSXAKP-UHFFFAOYSA-N hexamethylenetetramine Chemical compound C1N(C2)CN3CN1CN2C3 VKYKSIONXSXAKP-UHFFFAOYSA-N 0.000 description 6
- 230000003647 oxidation Effects 0.000 description 6
- 238000007254 oxidation reaction Methods 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 5
- 229920000642 polymer Polymers 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 229910021529 ammonia Inorganic materials 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 230000008030 elimination Effects 0.000 description 3
- 238000003379 elimination reaction Methods 0.000 description 3
- 239000000155 melt Substances 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- 231100000331 toxic Toxicity 0.000 description 3
- 230000002588 toxic effect Effects 0.000 description 3
- 241000219112 Cucumis Species 0.000 description 2
- 235000015510 Cucumis melo subsp melo Nutrition 0.000 description 2
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 2
- FJJCIZWZNKZHII-UHFFFAOYSA-N [4,6-bis(cyanoamino)-1,3,5-triazin-2-yl]cyanamide Chemical compound N#CNC1=NC(NC#N)=NC(NC#N)=N1 FJJCIZWZNKZHII-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 239000003513 alkali Substances 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- WDIHJSXYQDMJHN-UHFFFAOYSA-L barium chloride Chemical compound [Cl-].[Cl-].[Ba+2] WDIHJSXYQDMJHN-UHFFFAOYSA-L 0.000 description 2
- 229910001626 barium chloride Inorganic materials 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 239000004202 carbamide Substances 0.000 description 1
- 125000005588 carbonic acid salt group Chemical group 0.000 description 1
- 238000003763 carbonization Methods 0.000 description 1
- 150000003857 carboxamides Chemical class 0.000 description 1
- 238000003776 cleavage reaction Methods 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 230000007717 exclusion Effects 0.000 description 1
- 239000000543 intermediate Substances 0.000 description 1
- 229920002521 macromolecule Polymers 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 230000000802 nitrating effect Effects 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 229910000069 nitrogen hydride Inorganic materials 0.000 description 1
- 231100000252 nontoxic Toxicity 0.000 description 1
- 230000003000 nontoxic effect Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 239000012495 reaction gas Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 239000011833 salt mixture Substances 0.000 description 1
- 230000007017 scission Effects 0.000 description 1
- 229910000029 sodium carbonate Inorganic materials 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 239000010891 toxic waste Substances 0.000 description 1
- 150000003918 triazines Chemical class 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Classifications
-
- 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 regeneration agents for salt baths for carburizing iron and steel parts in the form of polymeric organic compounds and a process for their production.
- Salt baths for carburizing iron and steel parts in hardening technology generally consist of a mixture of alkali cyanide as an effective carburizing substance, barium chloride as a carrier melt and alkali carbonate. They are operated at a temperature of 800 to 950 ° C. At this temperature, carbon preferably diffuses into the surface of the workpieces suspended in the melt for about 1 to 5 hours. Subsequent quenching of the carburized workpieces results in a high hardness and high wear resistance. During the operation of the salt bath, however, there is a gradual oxidation of the cyanide by atmospheric oxygen to carbonate, which is ineffective for the carbonation process.
- the polymeric regeneration agents according to the invention thus enable problem-free regeneration of carburizing salt baths.
- the good coal effect of these baths is not affected by the regeneration.
- the regeneration agents according to the invention for carbonic salt baths can advantageously be prepared by reacting about 6 moles of formaldehyde with 3 moles of dicyandiamide or 6 moles of cyanamide or 2 moles of melamine or corresponding mixtures of these compounds at temperatures of 300 to 600 ° C., followed by pyrolysis treatment of the resinous condensation products with the exclusion of oxygen in the same temperature range.
- the formaldehyde is preferably used in the form of solid paraformaldehyde and the pyrolysis is carried out in a nitrogen atmosphere.
- the gross composition of the regeneration agent thus obtained can be changed by varying the pyrolysis conditions (temperature and pyrolysis time) and by varying the mixing ratio of the starting materials.
- the reaction and pyrolysis are preferably carried out at 400 to 500 ° C. for a period of 10 to 60 minutes.
- the addition of the formaldehyde can be varied in the range from 5 to 7 moles.
- This polymer is a deep black substance that is practically insoluble in common solvents. It has no optically recognizable melting point and decomposes slowly and exothermically in air at temperatures above 610 ° C.
- the material properties do not allow a clear structure determination with the usual analytical methods.
- ammonia, urotropin, water and traces of hydrocyanic acid in the preparation show that the compounds according to the invention must have a completely different structure than the white and water-soluble formaldehyde resins which occur as intermediates.
- the following table shows the advantages of the regeneration agent according to the invention compared to the substances melon and polymeric hydrocyanic acid used in nitrating salt baths.
- the same weight amounts of regenerating agent are added to commercially available carbonic salt baths which have been in operation for a long time and which still contained 9.0% cyanide and 0% cyanate.
- the increase in cyanide and cyanate values was measured 5 minutes after the regeneration agent was added.
- the marginal oxidation to be observed metallographically is directly related to the cyanate content of the bath.
- the following examples are intended to describe in more detail the preparation of the regenerants according to the invention.
- the reaction gas is passed through dust chambers to separate entrained solid particles and then into a torch.
- the analysis of the compounds produced by the above methods is very difficult, in particular in the determination of z.
- the values of x vary between 3 and 5 and the values of y between 5 and 8, depending on the manufacturing conditions.
- the values of z have to be estimated more or less.
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Phenolic Resins Or Amino Resins (AREA)
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
- Polymers With Sulfur, Phosphorus Or Metals In The Main Chain (AREA)
- Separation, Recovery Or Treatment Of Waste Materials Containing Plastics (AREA)
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
- Manufacture And Refinement Of Metals (AREA)
Abstract
Zur Regenerierung von Salzbädern zur Nitrierung von Teilen aus Eisen und Stahl sind polymere organische Substanzen bekannt, die aber nicht in Kohlungssalzbädern verwendet werden können, da mit ihnen nur geringe Mengen des kohlungsaktiven Cyanids entstehen, die Bäder schäumen und Kohlerückstände gebildet werden. Ein ausgezeichnetes Regenerierungsmittel für Kohlungssalzbäder erhält man, wenn man polymere organische Verbindungen der Bruttozusammensetzung [C6HxNy]z verwendet, mit x = 3 - 5, y = 5 - 8 und z = 10 - 10,000. Diese Verbindungen erhält man durch Umsetzung von Formaldehyd mit Cyanamid und/oder Dicyandiamid und/oder Melamin und pyrolytische Zersetzung des Umsetzungsproduktes bei 300 bis 600 °C.Polymeric organic substances are known for the regeneration of salt baths for the nitriding of parts made of iron and steel, but these cannot be used in carburizing salt baths, since they produce only small amounts of the carbonizing cyanide, foam the baths and form carbon residues. An excellent regeneration agent for carbonic salt baths can be obtained by using polymeric organic compounds with the gross composition [C6HxNy] z, with x = 3 - 5, y = 5 - 8 and z = 10 - 10,000. These compounds are obtained by reacting formaldehyde with cyanamide and / or dicyandiamide and / or melamine and pyrolytically decomposing the reaction product at 300 to 600 ° C.
Description
Die Erfindung betrifft Regenerierungsmittel für Salzbäder zum Aufkohlen von Eisen- und Stahlteilen in Form polymerer organischer Verbindungen und ein Verfahren zu deren Herstellung.The invention relates to regeneration agents for salt baths for carburizing iron and steel parts in the form of polymeric organic compounds and a process for their production.
Salzbäder zum Aufkohlen von Eisen-und Stahlteilen in der Härtereiteohnik bestehen im allgemeinen aus einem Gemisch von Alkalicyanid als wirksamer Kohlungssubstanz, Bariumchlorid als Trägerschmelze und Alkalicarbonat. Sie werden bei einer Temperatur von 800 bis 950 °C betrieben. Bei dieser Temperatur diffundiert bevorzugt Kohlenstoff in die Oberfläche der für etwa 1 bis 5 Stunden in die Schmelze eingehängten Werkstücke ein. Durch anschließendes Abschrecken der aufgekohlten Werkatücke wird eine hohe Randhärte und hohe Verschleißfestigkeit erzielt. Während des Betriebes des Salzbades findet jedoch -eine allmähliche Oxidation des Cyanids durch Luftsauerstoff zu Carbonat statt, das für den Xohlungsvorgang unwirksam ist.Salt baths for carburizing iron and steel parts in hardening technology generally consist of a mixture of alkali cyanide as an effective carburizing substance, barium chloride as a carrier melt and alkali carbonate. They are operated at a temperature of 800 to 950 ° C. At this temperature, carbon preferably diffuses into the surface of the workpieces suspended in the melt for about 1 to 5 hours. Subsequent quenching of the carburized workpieces results in a high hardness and high wear resistance. During the operation of the salt bath, however, there is a gradual oxidation of the cyanide by atmospheric oxygen to carbonate, which is ineffective for the carbonation process.
Weil die Bäder dadurch inaktiv werden, mußte die ursprüngliche Dadzusammensetzung bisher von Zeit zu Zeit durch Zusatz von Cyanid oder oyanidhaltigen Salzgemischen wieder hergestellt werden. Für jede Regenerierung mußte ein Teil des Salzes aus dem Bad ausgetragen und als hochgiftiges Altsalz verworfen werden. Diese Betriebsweise hat jedoch den Nachteil, daß hochgiftige Abfallsalze entsorgt werden müssen und daß giftiges Cyanid als Regenerierungsmittel gelagert werden muß. Es ist daher bereits vorgeschlagen worden (DE-PS 23 10 815),zur Regenerierung von Salzbädern für die Nitrierung von Werkstücken polymere Triazinverbindungen, polymere Cyanwasserstoffsäure und polymere Carbonsäureamide (DE-PS 24 09 285) zu verwenden. Diese Zusätze haben den Vorteil, daß sie ungiftig sind. Sie sind im Prinzip auch für Kohlungssalzbäder verwendbar. Bei Zugabe dieser Verbindungen wird das durch Oxidation entstandene, für die Kohlung unwirksame Carbonat im Salzbadtiegel selbst wieder in kohlungsaktives Cyanid zurückverwandelt. Bei dieser Betriebsweise entfällt daher das Ausschöpfen von Abfallsalzen und das Lagern von Cyanid.Because the baths become inactive as a result, the original dad composition had to be replaced from time to time by adding cyanide or salt mixtures containing oyanide be restored. For each regeneration, part of the salt had to be removed from the bath and discarded as highly toxic old salt. However, this mode of operation has the disadvantage that highly toxic waste salts have to be disposed of and that toxic cyanide has to be stored as a regenerating agent. It has therefore already been proposed (DE-PS 23 10 815) to use polymeric triazine compounds, polymeric hydrocyanic acid and polymeric carboxamides (DE-PS 24 09 285) for the regeneration of salt baths for the nitriding of workpieces. These additives have the advantage that they are non-toxic. In principle, they can also be used for carbonic salt baths. When these compounds are added, the carbonate in the salt bath crucible, which is formed by oxidation and is ineffective for carbonization, is converted back into carbon-active cyanide. With this mode of operation, there is no need to exhaust waste salts and store cyanide.
Die obengenannten Regeneriermittel werden in der Praxis jedoch überwiegend nur zur Regenerierung von Nitriersalzbädern bei Temperaturen um 580 C eingesetzt. Bei Verwendung dieser Stoffe zur Regenerierung von Kohlungssalzbädern bei 800 bis 950 °C tritt nämlich eine Reihe von Nachteilen auf, die ihren Einsatz in der Technik bislang verhindert haben.In practice, however, the abovementioned regeneration agents are predominantly used only for the regeneration of nitriding salt baths at temperatures around 580 C. When these substances are used to regenerate carbonic acid salt baths at 800 to 950 ° C, there are a number of disadvantages which have hitherto prevented their use in technology.
So entstehen bei Verwendung von Melon oder polymerem Harnstoff als Regenerierungsmittel in Kohlungsbädern bei 800 bis 950 C nur geringe Mengen des kohlungsaktiven Cyanids, aber große Mengen Cyanat, das nur teilweise und langsam zu Cyanid zerfällt und in Kohlungssalzbädern unerwünscht ist, da es die Kohlungswirkung negativ beeinflusst und zu Randoxidationen am Stahl führt. Außerdem tritt durch den Zerfall des Cyanate bei den hohen Temperaturen der Kohlungsbäder ein starkes Schäumen des Salzbädes auf, das zum Überlaufen der Schmelze führen kann. Ferner verläuft die Umsetzung dieser Regenerierungsmittel mit der Schmelze überaus heftiglThus, when using melon or polymeric urea as regeneration agent in carbonation baths at 800 to 950 ° C., only small amounts of the carbonizing cyanide are formed, but large amounts of cyanate, which only partially and slowly decomposes to cyanide and in carbonation salt baths is undesirable because it negatively affects the carburizing effect and leads to edge oxidation on the steel. In addition, due to the decomposition of the cyanate at the high temperatures of the carbonation baths, the salt bath is foamed to a great extent, which can lead to the melt overflowing. Furthermore, the implementation of these regenerants with the melt is extremely violent
Bei Verwendung der bekannten polymeren Cyanwasserstoffsäure (Azulminsäure) treten die obigen Schwierigkeiten zwar in geringerem Umfang auf, dafür entstehen aber andere Probleme. So bildet Azulminsäure bei der Reaktion mit Carbonat neben Cyanid beträchtliche Mengen an Kohlenstoff, wodurch sich eine dichte Baddecke ausbildet, die die Regenerierung erschwert. Die Cyanidausbeute ist daher unbefriedigend. Außerdem erfordert die Herstellung der polymeren Blausäure umfangreiche Sicherheitsmaßnahmen und großen apparativen Aufwand, da von dem hochgiftigen Cyanwasserstoff ausgegangen werden muß.When using the known polymeric hydrocyanic acid (azulmic acid), the above difficulties occur to a lesser extent, but other problems arise for this. In addition to cyanide, azulmic acid forms considerable amounts of carbon in the reaction with carbonate, which creates a dense bath cover that makes regeneration difficult. The cyanide yield is therefore unsatisfactory. In addition, the production of the polymeric hydrocyanic acid requires extensive safety measures and a large outlay on equipment, since the highly toxic hydrogen cyanide must be assumed.
Es war daher Aufgabe der vorliegenden Erfindung, Regenerierungsmittel für Salzbäder zum Aufkohlen von Eisen-und Stahlteilen in Form polymerer organischer Verbindungen zu finden, die eine praktisch vollständige Um- wandlung von Carbonat in Cyanid bewirken, kein Über- schäumen des Salzbades verursachen, keine Kohlerück- stande bilden und gefahrlos herzustellen sind. Diese Aufgabe wurde erfindungsgemäß dadurch gelöst, daß die polymeren organischen Verbindungen eine Bruttozusammensetzung [C6HxNy]z besitzen, wobei x=3-5, y=5-8 und z= 10 bis 10.000 betragen. Daneben kann die Substanz noch bis 1 % Sauerstoff in gebundener Form enthalten.It was therefore an object of the present invention to find regeneration agents for salt baths for carburizing iron and steel parts in the form of polymeric organic compounds which bring about a virtually complete conversion of carbonate to cyanide, do not cause the salt bath to foam up, form and are safe to manufacture. This object was achieved according to the invention in that the polymeric organic compounds have a gross composition [C 6 H x N y ] z , where x = 3-5, y = 5-8 and z = 10 to 10,000. In addition, the Substance still contain up to 1% oxygen in bound form.
Vorzugsweise verwendet man Verbindungen der Zusammensetzung [C6H3N7]z, wobei z=10 bis 10.000 ist. Besonders bewährt haben sich Polymere mit z zwischen 100 und 1.000. Die Bestimmung von z ist dabei aber sehr schwierig. Es ist daher möglich, daß auch Verbindungen mit anderen z-Verten gut eingesetzt werden können.Compounds of the composition [C 6 H 3 N 7 ] z are preferably used, where z = 10 to 10,000. Polymers with z between 100 and 1,000 have proven particularly successful. The determination of z is very difficult. It is therefore possible that compounds with other z-verts can also be used well.
Diese polymeren Verbindungen setzen sich mit dem Carbonat im Kohlungssalzbad in ruhiger Reaktion und mit sehr guter Ausbeute zu Cyanid um, wobei weder Kohlenstoffrückstände noch störende Cyanatanteile entstehen.These polymeric compounds react with the carbonate in the carbonation salt bath in a calm reaction and with very good yield to cyanide, with neither carbon residues nor disruptive cyanate components.
Die erfindungsgemäßen polymeren Regenerierungsmittel ermöglichen somit eine problemlose Regenerierung von Kohlungssalzbädern. Die gute Kohluagswirkung dieser Bäder wird durch die Regenerierung dabei nicht beeinträchtigt.The polymeric regeneration agents according to the invention thus enable problem-free regeneration of carburizing salt baths. The good coal effect of these baths is not affected by the regeneration.
Die erfindungsgemäBen Regenerierungsmittel für Kohlungssalzbäder lassen sich vorteilhafterweise durch Umsetzung von etwa 6 Mol Formaldehyd mit 3 Mol Dicyandiamid oder 6 Mol Cyanamid oder 2 Mol Melamin oder entsprechenden Gemischen dieser Verbindungen bei Temperaturen von 300 bis 600 °C herstellen, mit nachfolgender Pyrolysebehandlung der harzartigen Kondensationaprodukte unter Sauerstoffausschluß im gleichen Temperaturbereich. Vorzugsweiee wird der Formaldehyd in Form von festem Paraformaldehyd eingesetzt und die Pyrolyse in einer Stickstoffatmosphäre durchgeführt.The regeneration agents according to the invention for carbonic salt baths can advantageously be prepared by reacting about 6 moles of formaldehyde with 3 moles of dicyandiamide or 6 moles of cyanamide or 2 moles of melamine or corresponding mixtures of these compounds at temperatures of 300 to 600 ° C., followed by pyrolysis treatment of the resinous condensation products with the exclusion of oxygen in the same temperature range. The formaldehyde is preferably used in the form of solid paraformaldehyde and the pyrolysis is carried out in a nitrogen atmosphere.
Die Bruttozusammensetzung des so erhaltenen Regenerierungsmittels läßt sich durch Variation der Pyrolysebedingungen (Temperatur und Pyrolysedauer) und durch Variation des Mischungsverhältnisses der Ausgangsstoffe verändern. Vorzugsweise wird die Umsetzung und Pyrolyse bei 400 bis 500 o durchgeführt, während einer Dauer von 10 bis 60 Minuten. Die Zugabe des Formaldehyds kann man im Bereich von 5 bis 7 Mol variieren.The gross composition of the regeneration agent thus obtained can be changed by varying the pyrolysis conditions (temperature and pyrolysis time) and by varying the mixing ratio of the starting materials. The reaction and pyrolysis are preferably carried out at 400 to 500 ° C. for a period of 10 to 60 minutes. The addition of the formaldehyde can be varied in the range from 5 to 7 moles.
Als besonders geeignet hat sich die Umsetzung von 2 Mol Paraformaldehyd mit 1 Mol Dicyandiamid bei einer Pyrolysetemperatur von 400 oC und einer Pyrolysedauer von 30 Minuten erwiesen. Hierbei bilden sich zunächst unter Wasserabspaltung die an sich bekannten harzartig-klebrigen weißen Dicyandiamid-Formaldehyd-Kondensationsprodukte (vgl. R. Wegler u. H. Herlinger in Houben-Weyl, Band 14/2, Makromolekulare Stoffe II, S. 382 ff, Stgt. 1963), die bei den Pyrolysetemperaturen unter Abspaltung von Wasserdampf, Ammoniak, Urotropin und geringen Mengen von Blausäure zu einem schwarzen Polymerisat der Zusammensetzung [C6H3N7], z=100 - 1000, weiterreagieren.The reaction of 2 moles of paraformaldehyde with 1 mole of dicyandiamide at a pyrolysis temperature of 400 ° C. and a pyrolysis time of 30 minutes has proven to be particularly suitable. In this process, the resinous-sticky white dicyandiamide-formaldehyde condensation products known per se form firstly with elimination of water (see R. Wegler and H. Herlinger in Houben-Weyl, Volume 14/2, Macromolecular Substances II, p. 382 ff, Stgt . 1963), which react further at the pyrolysis temperatures with elimination of water vapor, ammonia, urotropin and small amounts of hydrocyanic acid to give a black polymer of the composition [C 6 H 3 N 7 ], z = 100-1000.
Dieses Polymerisat ist eine tiefschwarze, in den gängigen Lösungsmitteln praktisch unlösliche Substanz. Sie besitzt keinen optisch erkennbaren Schmelzpunkt und zersetzt sich langsam und exotherm an Luft bei Temperaturen oberhalb 610 °C.This polymer is a deep black substance that is practically insoluble in common solvents. It has no optically recognizable melting point and decomposes slowly and exothermically in air at temperatures above 610 ° C.
Die Materialeigeaechaften lassen keine eindeutige Strukturermittlung mit den gängigen analytiaahen Methoden zu. Die Bruttozusammensotzung und die erwähnten Materialeigenschaften, insbesondere die Unlöslichkeit und die schwarze Farbe sowie die Abspaltung von Ammoniak, Urotropin, Wasser und Spuren von Blausäure bei der Herstellung zeigen jedoch, daß die erfindungsgemäßen Verbindungen eine völlig andere Struktur aufweisen müssen, als die als Zwischenprodukte auftretenden weißen und wasserlöslichen Formaldehydharze.The material properties do not allow a clear structure determination with the usual analytical methods. The gross composition and the material properties mentioned, in particular the insolubility and the black color and the cleavage However, ammonia, urotropin, water and traces of hydrocyanic acid in the preparation show that the compounds according to the invention must have a completely different structure than the white and water-soluble formaldehyde resins which occur as intermediates.
Die Vorteile des erfindungsgemäßen Regenerierungsmittels im Vergleich zu den in Nitriersalzbädern eingesetzten Substanzen Melon und polymere Blausäure zeigt folgende Tabelle. Dazu werden gleiche Gewichtsmengen an Regenerierungsmittel in handelsübliche Kohlungssalzbäder gegeben, die längere Zeit in Betrieb waren und noch 9,0 % Cyanid und 0 % Cyanat enthielten. Der Anstieg der Cyanid- und Cyanatwerte wurde 5 Minuten nach Zugabe des Regenerierungsmittels gemessen.
Die metallographiach zu beobachtende Randoxidation steht im direkten Zusammenhang mit dem Cyanatgehalt des Bades. Folgende Beispiele sollen die Herstellung der erfindungsgemäßen Regenerierungsmittel näher beschreiben.The marginal oxidation to be observed metallographically is directly related to the cyanate content of the bath. The following examples are intended to describe in more detail the preparation of the regenerants according to the invention.
Kleinere Mengen des erfindungsgemäßen Regenerierungsmittels können wis folgt hergestellt werden:
- 1. Man vermischt 4,2 kg Dicyandiamid mit 3,0 kg Paraformaldehyd möglichst innig. Dieses Gemisch wird in einem eisernen Tiegel unter Stickstoffbeschleierung langsam auf 400 oC erhitzt. Es tritt Reaktion unter Abspaltung von Wasserdampf ein. Im Wasserdampf sind geringe Mengen Ammoniak, Urotropin und Blausäure enthalten. Die zunächst weiße, harzartige, aufgeblähte Reaktionsmasse verfärbt sich mit steigender Temperatur zunehmend dunkler und wird bei Erreichen von 400 oC schwarz, spröde und fest. Sie wird mechanisch im Tiegel zerstoßen und noch 20 Minuten bei 450 oC getempert. Dieses Material besitzt die Formel [C6HxNy]z, x = 3 - 5, y = 5 - 8, z = 10 - 10.000. Bei der Reaktion werden 3,6 kg Wasserdampf frei. Die Ausbeute beträgt 60 % der Theorie.
- 2. Technisch erfolgt die Herstellung kontinuierlich in einem mit Stickstoff gespülten elektrisch auf 400 - 450 oC beheizten Reaktorrohr. Das Gemisch von Dicyandiamid und Paraformaldehyd im Mol-Verhältnis 1:2 wird automatisch über eine Schleuse in den Reaktor eingetragen. Es reagiert dort nach Erreichen der an- gegebenen Temperatur unter Abspaltung von 2 Mol Wasserdampf und geringen Mengen NH3, HCN und Urotropin zu dem Polymerisat [C6H3N7 z,]z = 10 - 10.000. Dieses Produkt wird durch eine bewegte Welle im Reaktor gebrochen und über eine zweite Schleuse pulverförmig ausgetragen.
- 1. Mix 4.2 kg of dicyandiamide with 3.0 kg of paraformaldehyde as intimately as possible. This mixture is slowly heated to 400 o C in an iron crucible with nitrogen blanketing. A reaction occurs with the elimination of water vapor. Small amounts of ammonia, urotropin and hydrocyanic acid are contained in the water vapor. The initially white, resin-like, inflated reaction mass turns increasingly darker with increasing temperature and becomes black, brittle and solid when 400 o C is reached. It is mechanically crushed in the crucible and annealed at 450 o C for a further 20 minutes. This material has the formula [C 6 H x N y ] z , x = 3 - 5, y = 5 - 8, z = 10 - 10,000. The reaction releases 3.6 kg of water vapor. The yield is 60% of theory.
- 2. Technically, the production takes place continuously in a nitrogen-purged reactor tube heated to 400-450 o C. The mixture of dicyandiamide and paraformaldehyde in a molar ratio of 1: 2 is automatically introduced into the reactor via a lock. After the specified temperature has been reached, 2 moles of water vapor and small amounts of NH 3 , HCN and urotropin are reacted to give the polymer [C 6 H 3 N 7 z ,] z = 10-10,000. This product is broken by a moving shaft in the reactor and discharged in powder form via a second lock.
Das Reaktionsgas wird zur Abscheidung mitgerissener Feststoffpartikel über Staubkammern und anschließend in eine Fackel geführt.The reaction gas is passed through dust chambers to separate entrained solid particles and then into a torch.
Die Analyse der nach den obigen Verfahren hergestellten Verbindungen ist insbesondere in der Bestimmung von z sehr schwierig. Die Werte von x schwanken zwischen 3 und 5 und die Werte von y zwischen 5 und 8, je nach den Herstellungsbedingungen. Die Werte von z müssen mehr oder weniger geschätzt werden.The analysis of the compounds produced by the above methods is very difficult, in particular in the determination of z. The values of x vary between 3 and 5 and the values of y between 5 and 8, depending on the manufacturing conditions. The values of z have to be estimated more or less.
Folgendes Beispiel zeigt die Anwendung des erfindungsgemäßen Regenerierungsmittels:
- In einem Tiegelofen werden 100 kg eines Kohlungssalzes der Zusammensetzung 40 % BaCl2, 50 % Na2CO3 und 10% NaCN aufgeschmolzen und auf 930 C erhitzt. Infolge der Aufkohlung der eingebrachten Chargen und durch Luftoxidation sinkt der Cyanidgehalt dieses Bades stündlich und kontinuierlich um etwa 0,15 %. Bei normaler Betriebsweise würde dieses Bad nach 24 Stunden nur noch 6,4 % NaCN enthalten und keine optimalen Kohlungsergebnisse mehr liefern.
- 100 kg of a carbonic salt of the composition 40% BaCl 2 , 50% Na 2 CO 3 and 10% NaCN are melted in a crucible furnace and heated to 930.degree. As a result of the carburization of the introduced batches and due to air oxidation, the cyanide content of this bath drops continuously and continuously by approximately 0.15%. Under normal operating conditions, this bath would only contain 6.4% NaCN after 24 hours and would no longer provide optimal coaling results.
Dieses Absinken des Cysnidgehalts wird durch Zugabe von 1.50 g/h des erfindungsgemäßen Regenerierungsmittel verhindert, da das bei der Oxidation von NaCN gebildete Carbonat durch das Regenerierungamittel wieder zu kohlungsaktivem NaCN zurückverwandelt wird. Auf diese Weise kann der optimale Cyanidgehalt von 10% NaCN stetig aufrecht erhalten werden.This drop in the cysnide content is prevented by adding 1.50 g / h of the regeneration agent according to the invention, since the carbonate formed during the oxidation of NaCN is converted back to carbon-active NaCN by the regeneration agent. In this way, the optimal cyanide content of 10% NaCN can be constantly maintained.
Claims (7)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AT83112965T ATE23054T1 (en) | 1983-01-08 | 1983-12-22 | CARBON SALT BATH REGENERATOR AND PROCESS FOR THEIR MANUFACTURE. |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3300488 | 1983-01-08 | ||
| DE19833300488 DE3300488A1 (en) | 1983-01-08 | 1983-01-08 | REGENERATION AGENT FOR CARBON SALT BATHS AND METHOD FOR THE PRODUCTION THEREOF |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| EP0113474A2 true EP0113474A2 (en) | 1984-07-18 |
| EP0113474A3 EP0113474A3 (en) | 1984-12-05 |
| EP0113474B1 EP0113474B1 (en) | 1986-10-22 |
Family
ID=6187925
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP83112965A Expired EP0113474B1 (en) | 1983-01-08 | 1983-12-22 | Regenerator for carburizing salt baths and process for making it |
Country Status (18)
| Country | Link |
|---|---|
| US (1) | US4509993A (en) |
| EP (1) | EP0113474B1 (en) |
| JP (1) | JPS59133363A (en) |
| AR (1) | AR241711A1 (en) |
| AT (1) | ATE23054T1 (en) |
| AU (1) | AU563807B2 (en) |
| BR (1) | BR8400058A (en) |
| CA (1) | CA1200472A (en) |
| DE (2) | DE3300488A1 (en) |
| ES (1) | ES528702A0 (en) |
| HU (1) | HU191261B (en) |
| IL (1) | IL70461A (en) |
| IN (1) | IN161676B (en) |
| MX (1) | MX169710B (en) |
| PT (1) | PT77901B (en) |
| SU (1) | SU1227120A3 (en) |
| YU (1) | YU43558B (en) |
| ZA (1) | ZA839274B (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB434961A (en) * | 1933-03-10 | 1935-09-12 | Du Pont | Improvements in or relating to the case-hardening of iron and steel |
| US4268323A (en) * | 1979-04-05 | 1981-05-19 | Kolene Corp. | Process for case hardening steel |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB379764A (en) * | 1930-06-07 | 1932-09-05 | Degussa | Improvements in or relating to the cementation of iron and steel and their alloys |
| US3303063A (en) * | 1964-06-15 | 1967-02-07 | Gen Motors Corp | Liquid nitriding process using urea |
| DE2234171C2 (en) * | 1972-07-12 | 1973-10-31 | Th. Goldschmidt Ag, 4300 Essen | Procedure for the joint disposal and / or processing of hard salt waste |
| US4019928A (en) * | 1973-03-05 | 1977-04-26 | Duetsche Gold- Und Silber-Scheideanstalt Vormals Roessler | Process for nitriding iron and steel in salt baths regenerated with triazine polymers |
| 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 |
| SU697603A1 (en) * | 1977-05-19 | 1979-11-15 | Предприятие П/Я Р-6500 | Melt for nitriding steel parts |
| SU775170A1 (en) * | 1979-01-16 | 1980-10-30 | Львовский Ордена Ленина Политехнический Институт | Steel cyaniding medium |
-
1983
- 1983-01-08 DE DE19833300488 patent/DE3300488A1/en not_active Withdrawn
- 1983-12-13 ZA ZA839274A patent/ZA839274B/en unknown
- 1983-12-15 SU SU833723480A patent/SU1227120A3/en active
- 1983-12-15 IL IL70461A patent/IL70461A/en not_active IP Right Cessation
- 1983-12-21 YU YU2480/83A patent/YU43558B/en unknown
- 1983-12-22 AT AT83112965T patent/ATE23054T1/en not_active IP Right Cessation
- 1983-12-22 DE DE8383112965T patent/DE3367113D1/en not_active Expired
- 1983-12-22 EP EP83112965A patent/EP0113474B1/en not_active Expired
- 1983-12-28 PT PT77901A patent/PT77901B/en not_active IP Right Cessation
- 1983-12-29 US US06/566,811 patent/US4509993A/en not_active Expired - Lifetime
- 1983-12-31 IN IN1605/CAL/83A patent/IN161676B/en unknown
-
1984
- 1984-01-04 MX MX199960A patent/MX169710B/en unknown
- 1984-01-04 AU AU23073/84A patent/AU563807B2/en not_active Ceased
- 1984-01-05 AR AR84295353A patent/AR241711A1/en active
- 1984-01-05 ES ES528702A patent/ES528702A0/en active Granted
- 1984-01-06 CA CA000444877A patent/CA1200472A/en not_active Expired
- 1984-01-06 BR BR8400058A patent/BR8400058A/en not_active IP Right Cessation
- 1984-01-06 JP JP59000344A patent/JPS59133363A/en active Granted
- 1984-01-06 HU HU8448A patent/HU191261B/en unknown
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB434961A (en) * | 1933-03-10 | 1935-09-12 | Du Pont | Improvements in or relating to the case-hardening of iron and steel |
| US4268323A (en) * | 1979-04-05 | 1981-05-19 | Kolene Corp. | Process for case hardening steel |
Non-Patent Citations (1)
| Title |
|---|
| ULLMANNS ENCYKLOP[DIE DER TECHNISCHEN CHEMIE, 4. Auflage, Band 7, 1974, Seiten 403-422; Aminoplaste, Verlag Chemie, Weinheim, DE; * |
Also Published As
| Publication number | Publication date |
|---|---|
| DE3300488A1 (en) | 1984-07-12 |
| ES8407106A1 (en) | 1984-09-01 |
| CA1200472A (en) | 1986-02-11 |
| EP0113474A3 (en) | 1984-12-05 |
| AU2307384A (en) | 1984-07-12 |
| ZA839274B (en) | 1984-10-31 |
| JPS59133363A (en) | 1984-07-31 |
| PT77901B (en) | 1986-04-11 |
| AR241711A1 (en) | 1992-11-30 |
| MX169710B (en) | 1993-07-19 |
| ATE23054T1 (en) | 1986-11-15 |
| IL70461A0 (en) | 1984-03-30 |
| DE3367113D1 (en) | 1986-11-27 |
| YU43558B (en) | 1989-08-31 |
| PT77901A (en) | 1984-01-01 |
| SU1227120A3 (en) | 1986-04-23 |
| HU191261B (en) | 1987-01-28 |
| US4509993A (en) | 1985-04-09 |
| YU248083A (en) | 1985-10-31 |
| ES528702A0 (en) | 1984-09-01 |
| JPH0524986B2 (en) | 1993-04-09 |
| EP0113474B1 (en) | 1986-10-22 |
| BR8400058A (en) | 1984-08-14 |
| AU563807B2 (en) | 1987-07-23 |
| IL70461A (en) | 1987-12-20 |
| IN161676B (en) | 1988-01-16 |
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