EP0311134B1 - Powder-metallurgically produced electrical contact material comprising silver and graphite, and process for producing it - Google Patents
Powder-metallurgically produced electrical contact material comprising silver and graphite, and process for producing it Download PDFInfo
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- EP0311134B1 EP0311134B1 EP88116746A EP88116746A EP0311134B1 EP 0311134 B1 EP0311134 B1 EP 0311134B1 EP 88116746 A EP88116746 A EP 88116746A EP 88116746 A EP88116746 A EP 88116746A EP 0311134 B1 EP0311134 B1 EP 0311134B1
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- silver
- powder
- material according
- graphite
- copper
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H1/00—Contacts
- H01H1/02—Contacts characterised by the material thereof
- H01H1/021—Composite material
- H01H1/027—Composite material containing carbon particles or fibres
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/16—Making metallic powder or suspensions thereof using chemical processes
- B22F9/30—Making metallic powder or suspensions thereof using chemical processes with decomposition of metal compounds, e.g. by pyrolysis
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C32/00—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ
- C22C32/0084—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ carbon or graphite as the main non-metallic constituent
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C5/00—Alloys based on noble metals
- C22C5/06—Alloys based on silver
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H1/00—Contacts
- H01H1/02—Contacts characterised by the material thereof
- H01H1/021—Composite material
- H01H1/023—Composite material having a noble metal as the basic material
Definitions
- the invention is based on a powder-metallurgically produced material for electrical contacts made of silver with 2 to 7% by weight of graphite and with an additive which increases the strength of the material.
- Composite materials made of silver with 2 to 7% by weight of graphite are used for electrical contacts in circuit breakers and in circuit breakers.
- contact pieces made of silver graphite combine a low tendency to weld silver graphite against copper or against silver-plated copper with the opposite contact piece in the contact material pairing that is usually used, with a low contact resistance after an arc effect on the contacting surface.
- contact pieces made of silver graphite are subject to a relatively high erosion. The result is that with increasing switching numbers, the switching chamber in which the contact pieces are accommodated is metallized by silver, which evaporates under the influence of an arc, and sooty by released graphite. This reduces the dielectric strength of the switching chamber.
- Another proposal is to manufacture contact pieces from a silver-copper-graphite fiber composite material by filling graphite powder into a double-jacket tube, the inner wall of which is made of copper and the outer wall of which is silver; the double-walled tube is closed and extruded into a thinner rod, which is then cut into shorter pieces, which are put into a silver tube, which is closed at the ends and then reshaped by extrusion.
- a contact material with a fine fiber structure is obtained (K. Müller and D. Stöckel "THE IRE PROCESS FOR THE MANUFACTURE OF SILVERBASED COMPOSITE CONTACT MATERIALS" Proceedings of the 13th International Conference on Electric Contact Phenomena, Chicago, 1984, pp.
- contact materials made of 45% silver, 50% tungsten and 5% graphite as well as made of 88% silver, 10% nickel and 2% graphite are known, which lie at the edge of the composition range claimed below and by mixing of powders of their components, pressing, sintering and re-pressing of contact pieces.
- the present invention is based on the object of making available a material for electrical contacts made of silver with graphite and an additive which increases the strength of the material, in which low contact resistance, low tendency to weld and low erosion (high Service life) in a similar advantageous manner as in the known silver-copper-graphite fiber composite material; however, the new contact material is said to be more economical to produce than the known fiber composite material.
- the material should contain at least 0.5% by weight of a base metal in order to be able to bring about an appreciable increase in strength. However, the material should not contain more than 50% by weight of one or more base metals, since otherwise the contact resistance will increase too much, in particular due to the formation of base metal oxides.
- Particularly suitable base metals are one or more of the metals from the group of copper, nickel, iron, manganese, zinc, tungsten and molybdenum, copper being particularly preferred and the proportion of the base metal in the material preferably being 10 to 25% by weight.
- base metals those which do not form an alloy with silver or, at best, a precipitation alloy at low temperature, and thereby cause the material to harden.
- base metals those which have the highest possible electrical conductivity.
- copper proves to be an optimal base metal additive, whereby a part of the copper, preferably only a portion of 2 to 3% by weight of the material, may be present as copper oxide (CuO), thereby ensuring that the contact pieces are not welded is increased. Because of the simultaneous considerable copper content, there is no need to set the copper oxide content as high as that of the prior art silver-copper oxide-graphite contact materials, so that its disadvantages do not apply to a contact material according to the invention with a low copper oxide content.
- the materials according to the invention can be produced, at least in principle, like conventional silver-graphite materials by powder metallurgy by pressing powder mixtures, sintering and post-compression, if very fine-grained (average particle size smaller than approx. 0.5 ⁇ m) silver powder, copper powder and graphite powder are mixed with one another , pressed to shaped bodies, sintered and post-compressed, the compression should be so strong that the pore volume of the material is not more than 2%.
- a particularly advantageous method for producing the material according to the invention is the subject of claim 13.
- Advantageous further developments of this method are specified in the further subclaims.
- a silver powder, a base metal powder and a graphite powder are not mixed with one another and pressed to form shaped bodies, but instead a powder of a precipitation alloy made of silver is produced with the base metal and this is mixed with graphite powder; molded bodies are then pressed, sintered and post-compressed therefrom, the compression being so strong that the pore volume is less than 2%.
- a particularly suitable method for obtaining such an alloy powder is spray pyrolysis (US-A-3 510 291, EP-0012 202 A1, DE-29 29 630 C2).
- a solution which contains a silver salt and one or more base metal salts in solution is sprayed into a hot reaction vessel.
- the salts are decomposed therein and the solvent evaporated, and an extraordinarily fine-grained alloy powder precipitates, which is particularly suitable for the production of the material according to the invention.
Abstract
Description
Die Erfindung geht aus von einem pulvermetallurgisch hergestellten Werkstoff für elektrische Kontakte aus Silber mit 2 bis 7 Gew.-% Graphit und mit einem die Festigkeit des Werkstoffes steigernden Zusatz.The invention is based on a powder-metallurgically produced material for electrical contacts made of silver with 2 to 7% by weight of graphite and with an additive which increases the strength of the material.
Verbundwerkstoffe aus Silber mit 2 bis 7 Gew.-% Graphit finden für elektrische Kontakte in Leistungsschaltern und in Leitungsschutzschaltern Verwendung. Kontaktstücke aus Silber-Graphit verbinden für diesen Verwendungszweck eine geringe Neigung, in der üblicherweise eingesetzten Kontaktwerkstoffpaarung Silber-Graphit gegen Kupfer oder gegen versilbertes Kupfer mit dem gegenüberliegenden Kontaktstück zu verschweißen, mit einem geringen Kontaktwiderstand nach einer Lichtbogeneinwirkung auf die kontaktgebende Fläche. Nachteilig ist allerdings, dass Kontaktstücke aus Silber-Graphit einem verhältnismässig hohen Abbrand unterliegen. Das führt dazu, dass mit zunehmenden Schaltzahlen die Schaltkammer, in der die Kontaktstücke untergebracht sind, durch Silber, welches unter Lichtbogeneinwirkung verdampft, metallisiert wird und durch freigesetzten Graphit verrußt. Dadurch sinkt die Spannungsfestigkeit der Schaltkammer.Composite materials made of silver with 2 to 7% by weight of graphite are used for electrical contacts in circuit breakers and in circuit breakers. For this purpose, contact pieces made of silver graphite combine a low tendency to weld silver graphite against copper or against silver-plated copper with the opposite contact piece in the contact material pairing that is usually used, with a low contact resistance after an arc effect on the contacting surface. However, it is disadvantageous that contact pieces made of silver graphite are subject to a relatively high erosion. The result is that with increasing switching numbers, the switching chamber in which the contact pieces are accommodated is metallized by silver, which evaporates under the influence of an arc, and sooty by released graphite. This reduces the dielectric strength of the switching chamber.
Es hat nicht an Versuchen gefehlt, die elektrische Lebensdauer von Kontaktstücken aus Silber-Graphit zu verlängern. So ist es bekannt, dem Werkstoff ungefähr 5 Gew.-% Kupferoxid (CuO) zuzusetzen (DE-Z "Elektrische Energie-Technik" 26, (1981) Heft 2, Seite 9-15). Ein Zusatz von Kupferoxid kann zwar die Lebensdauer verlängern, hat jedoch auch Nachteile, weil er die Lötbarkeit der Kontaktstücke verschlechtert und thermisch nicht besonders stabil ist, so dass die Kontaktstücke elektrisch nicht sehr hoch belastbar sind.There has been no lack of attempts to extend the electrical life of silver graphite contact pieces. So it is known, the material about 5 wt .-% copper oxide (CuO) to be added (DE-Z "Electrical Energy Technology" 26, (1981) Issue 2, page 9-15). Adding copper oxide can extend the service life, but it also has disadvantages because it worsens the solderability of the contact pieces and is not particularly thermally stable, so that the contact pieces cannot be subjected to very high electrical loads.
Ein anderer Vorschlag geht dahin, Kontaktstücke aus einem Silber-Kupfer-Graphit-Faserverbundwerkstoff herzustellen, indem in ein Doppelmantelrohr, dessen innere Wand aus Kupfer und dessen äußere Wand aus Silber besteht, Graphit-pulver eingefüllt wird; das Doppelmantelrohr wird verschlossen und durch Strangpressen in einen dünneren Stab umgeformt, welcher anschließend in kürzere Stücke zerteilt wird, die man in ein Silberrohr steckt, welches an den Enden verschlossen und erneut durch Strangpressen umgeformt wird. In mehreren solchen Schritten kommt man auf diese Weise zu einem Kontaktwerkstoff mit feiner Faserstruktur (K. Müller und D. Stöckel "THE IRE PROCESS FOR THE MANUFACTURE OF SILVERBASED COMPOSITE CONTACT MATERIALS" Proceedings of the 13. International Conference on Electric Contact Phenomena, Chicago, 1984, S. 237-242). Aus einem solchen Faserverbundwerkstoff hergestellte elektrische Kontakte verbinden in zufriedenstellender Weise hinreichend geringe Verschweißneigung mit niedrigem Kontaktwiderstand und niedrigem Abbrand; nachteilig ist jedoch, dass derartige Werkstoff durch ein sehr aufwendiges Verfahren hergestellt werden müssen, so dass sie trotz ihrer guten Eigenschaften bisher wenig praktische Anwendung gefunden haben.Another proposal is to manufacture contact pieces from a silver-copper-graphite fiber composite material by filling graphite powder into a double-jacket tube, the inner wall of which is made of copper and the outer wall of which is silver; the double-walled tube is closed and extruded into a thinner rod, which is then cut into shorter pieces, which are put into a silver tube, which is closed at the ends and then reshaped by extrusion. In several such steps, a contact material with a fine fiber structure is obtained (K. Müller and D. Stöckel "THE IRE PROCESS FOR THE MANUFACTURE OF SILVERBASED COMPOSITE CONTACT MATERIALS" Proceedings of the 13th International Conference on Electric Contact Phenomena, Chicago, 1984, pp. 237-242). Electrical contacts made from such a fiber composite material satisfactorily combine a sufficiently low tendency to weld with low contact resistance and low erosion; it is disadvantageous, however, that such material must be produced by a very complex process, so that despite their good properties have so far found little practical application.
Aus METALS HANDBOOK, 9.ed. Vol.3, 1980,p.662,679,680 sind bereits Kontaktwerkstoffe aus 45 % Silber, 50 % Wolfram und 5 % Graphit sowie aus 88 % Silber, 10 % Nickel und 2 % Graphit bekannt, die am Rand des nachfolgend beanspruchten Zusammensetzungsbereichs liegen und durch Mischen von Pulvern ihrer Bestandteile, Pressen, Sintern und Nachpressen von Kontaktstücken hergestellt werden.From METALS HANDBOOK, 9.ed. Vol.3, 1980, p.662,679,680, contact materials made of 45% silver, 50% tungsten and 5% graphite as well as made of 88% silver, 10% nickel and 2% graphite are known, which lie at the edge of the composition range claimed below and by mixing of powders of their components, pressing, sintering and re-pressing of contact pieces.
Aus der DE-A-2 141 409 sind bereits Kontaktwerkstoffe aus 50 bis 80 % Silber, 1 bis 4 % Graphit, 20 bis 45 % Nickel und Kontaktwerkstoffe aus 5 bis 30 % Silber, 0,5 bis 50 % Graphit, Rest Nickel bekannt, welche durch Mischen von Pulvern ihrer Bestandteile, Kalt- und Heißpressen von Kontaktstücken daraus hergestellt werden. Dabei ist bei der zuletzt genannten Zusammensetzung angegeben, dass die Pulver feindispers sein sollen, welches in einem Beispiel dadurch erläutert wird, dass höchstens 95 % und mindestens 75 % der Teilchen durch ein Sieb mit der Maschengröße 0045 durchgehen. Damit liegen die Teilchengrößen im üblichen Bereich von einigen 10 µm. Entsprechendes wird man auch im Fall der aus dem METALS HANDBOOK bekannten Kontaktwerkstoffe unterstellen dürfen, bei denen über die Teilchengroße keine Angaben gemacht sind.Contact materials made of 50 to 80% silver, 1 to 4% graphite, 20 to 45% nickel and contact materials made of 5 to 30% silver, 0.5 to 50% graphite, the rest of nickel are already known from DE-A-2 141 409 , which are produced by mixing powders of their components, cold and hot pressing of contact pieces. In the case of the last-mentioned composition, it is stated that the powders should be finely dispersed, which is explained in one example by the fact that at most 95% and at least 75% of the particles pass through a sieve with mesh size 0045. The particle sizes are in the usual range of a few 10 µm. The same can be assumed in the case of the contact materials known from the METALS HANDBOOK, for which no details are given about the particle size.
Eine Erhöhung der Festigkeit wird bei diesen vorbekannten Silber-Graphit-Werkstoffen mit Nickel oder Wolfram in dem erwünschten Ausmaß aber nicht erzielt.However, an increase in strength is not achieved to the desired extent with these previously known silver graphite materials with nickel or tungsten.
Der vorliegenden Erfindung liegt die Aufgabe zugrunde, einen Werkstoff für elektrische Kontakte aus Silber mit Graphit und einem die Festigkeit des Werkstoffs steigernden Zuatz verfügbar zu machen, in welchem sich niedriger Kontaktübergangswiderstand, geringe Verschweißneigung und geringer Abbrand (hohe Lebensdauer) in ähnlich vorteilhafter Weise miteinander verbinden wie in dem bekannten Silber-Kupfer-Graphit-Faserverbundwerkstoff; der neue Kontaktwerkstoff soll jedoch wirtschaftlicher herstellbar sein als der bekannte Faserverbundwerkstoff.The present invention is based on the object of making available a material for electrical contacts made of silver with graphite and an additive which increases the strength of the material, in which low contact resistance, low tendency to weld and low erosion (high Service life) in a similar advantageous manner as in the known silver-copper-graphite fiber composite material; however, the new contact material is said to be more economical to produce than the known fiber composite material.
Diese Aufgabe wird gelöst durch einen Werkstoff mit den im Patentanspruch 1 angegebenen Merkmalen. Vorteilhafte Weiterbildungen der Erfindung sind Gegenstand der Unteransprüche.This object is achieved by a material with the features specified in claim 1. Advantageous developments of the invention are the subject of the dependent claims.
Überraschenderweise hat es sich gezeigt, dass man die Lebensdauer von Kontaktstücken aus einem Silber-Graphit-Werkstoff ohne Nachteil für den Kontaktwiderstand verbessern kann, wenn man einen Unedelmetallzusatz zum Werkstoff verwendet und dafür sorgt, dass dieser sehr fein verteilt im Werkstoff vorliegt, nämlich in höchstens 5·10⁻¹⁰ mm³, vorzugsweise höchstens 0,5·10⁻¹⁰ mm³ großen Teilchen. Für die Teilchengrößen wurde eine Volumenangabe gewählt, weil die Teilchen in unterschiedlicher Form vorliegen können, sowohl in Form von Teilchen, deren Durchmesser in alle Richtungen in derselben Größenordnung liegen, als auch in Form von langgestreckten Teilchen.Surprisingly, it has been shown that the service life of contact pieces made of a silver graphite material can be improved without disadvantage for the contact resistance if one uses a base metal additive to the material and ensures that it is very finely distributed in the material, namely in at most 5 · 10 ·¹⁰ mm³, preferably at most 0.5 · 10⁻¹⁰ mm³ large particles. A volume was given for the particle sizes chosen because the particles can exist in different forms, both in the form of particles whose diameters lie in the same order of magnitude in all directions and in the form of elongated particles.
Der Werkstoff soll wenigstens 0,5 Gew.-% eines Unedelmetalls enthalten, um eine nennenswerte Festigkeitssteigerung bewirken zu können. Der Werkstoff soll aber nicht mehr als 50 Gew.-% eines oder mehrerer Unedelmetalle enthalten, da sonst ein zu starker Anstieg des Kontaktwiderstandes, insbesondere durch Bildung von Unedelmetalloxiden auftritt.The material should contain at least 0.5% by weight of a base metal in order to be able to bring about an appreciable increase in strength. However, the material should not contain more than 50% by weight of one or more base metals, since otherwise the contact resistance will increase too much, in particular due to the formation of base metal oxides.
Der Graphitzusatz soll die Verschweißneigung reduzieren und soll deshalb nicht weniger als 2 Gew.-% betragen. Er soll andererseits nicht mehr als 7 Gew.-% betragen, da sonst die Festigkeit des Werkstoffes herabgesetzt wird und der Abbrand ansteigt.The addition of graphite should reduce the tendency to weld and should therefore not be less than 2% by weight. On the other hand, it should not be more than 7% by weight, since otherwise the strength of the material is reduced and the burn-up increases.
Als Unedelmetalle eignen sich besonders eines oder mehrere der Metalle aus der Gruppe Kupfer, Nickel, Eisen, Mangan, Zink, Wolfram und Molybdän, wobei Kupfer besonders bevorzugt ist und der Anteil des Unedelmetalls im Werkstoff vorzugsweise 10 bis 25 Gew.-% beträgt.Particularly suitable base metals are one or more of the metals from the group of copper, nickel, iron, manganese, zinc, tungsten and molybdenum, copper being particularly preferred and the proportion of the base metal in the material preferably being 10 to 25% by weight.
Im Hinblick auf die angestrebte Festigkeitssteigerung des Werkstoffes ist es von Vorteil, als Unedelmetalle solche auszuwählen, die bei niedriger Temperatur mit Silber keine Legierung oder allenfalls eine Ausscheidungslegierung bilden und dadurch eine Härtung des Werkstoffes bewirken. In diesem Zusammenhang sie namentlich auf die Unedelmetalle Kupfer und Nickel hingewiesen. Ausserdem ist es von Vorteil, als Unedelmetalle solche auszuwählen, die eine möglichst hohe elektrische Leitfähigkeit haben. Als optimaler Unedelmetallzusatz erweist sich nach den vorstehend erwähnten Auswahlkriterien das Kupfer, wobei ein Teil des Kupfers, vorzugsweise nur ein Anteil von 2 bis 3 Gew.-% am Werkstoff, als Kupferoxid (CuO) vorliegen darf, wodurch die Sicherheit gegen ein Verschweißen der Kontaktstücke erhöht wird. Wegen des gleichzeitigen beachtlichen Kupferanteils besteht keinerlei Notwendigkeit, den Kupferoxidanteil so hoch anzusetzen wie bei den zum Stand der Technik gehörenden Silber-Kupferoxid-Graphit-Kontaktwerkstoffen, so dass dessen Nachteile für einen erfindungsgemäßen Kontaktwerkstoff mit geringem Kupferoxidanteil nicht zutreffen.In view of the desired increase in the strength of the material, it is advantageous to select as base metals those which do not form an alloy with silver or, at best, a precipitation alloy at low temperature, and thereby cause the material to harden. In this context, she specifically referred to the base metals copper and nickel. In addition, it is advantageous to select as base metals those which have the highest possible electrical conductivity. According to the selection criteria mentioned above, copper proves to be an optimal base metal additive, whereby a part of the copper, preferably only a portion of 2 to 3% by weight of the material, may be present as copper oxide (CuO), thereby ensuring that the contact pieces are not welded is increased. Because of the simultaneous considerable copper content, there is no need to set the copper oxide content as high as that of the prior art silver-copper oxide-graphite contact materials, so that its disadvantages do not apply to a contact material according to the invention with a low copper oxide content.
Die erfindungsgemäßen Werkstoffe können zumindest prinzipiell wie herkömmliche Silber-Graphit-Werkstoffe auf pulvermetallurgischem Wege durch Pressen von Pulvermischungen, Sintern und Nachverdichten hergestellt werden, wenn man sehr feinkörniges (mittlere Teilchengröße kleiner als ca. 0,5 µm) Silberpulver, Kupferpulver und Graphitpulver miteinander mischt, zu Formkörpern preßt, sintert und nachverdichtet, wobei die Verdichtung so stark sein sollte, dass das Porenvolumen des Werkstoffs nicht mehr als 2 % beträgt.The materials according to the invention can be produced, at least in principle, like conventional silver-graphite materials by powder metallurgy by pressing powder mixtures, sintering and post-compression, if very fine-grained (average particle size smaller than approx. 0.5 μm) silver powder, copper powder and graphite powder are mixed with one another , pressed to shaped bodies, sintered and post-compressed, the compression should be so strong that the pore volume of the material is not more than 2%.
Ein besonders vorteilhaftes Verfahren zum Herstellen des erfindungsgemäßen Werkstoffes ist jedoch Gegenstand des Patentanspruches 13. Vorteilhafte Weiterbildungen dieses Verfahrens sind in den weiteren Unteransprüchen angegeben. Nach diesem Verfahren werden nicht ein Silberpulver, ein Unedelmetallpulver und ein Graphitpulver miteinander gemischt und zu Formkörpern gepreßt, sondern es wird zunächst ein Pulver einer Ausscheidungslegierung aus Silber mit dem Unedelmetall hergestellt und dieses mit Graphitpulver gemischt; daraus werden dann Formkörper gepreßt, gesintert und nachverdichtet, wobei die Verdichtung so stark sein sollte, dass das Porenvolumen weniger als 2% beträgt. Ein besonders geeignetes Verfahren zum Gewinnen eines solchen Legierungspulvers ist die Sprühpyrolyse (US-A-3 510 291, EP-0012 202 A1, DE-29 29 630 C2). Dabei wird eine Lösung, welche ein Silbersalz und ein oder mehrere Unedelmetallsalze gelöst enthält, in ein heißes Reaktionsgefäß eingesprüht. Darin werden die Salze zersetzt und das Lösungsmittel verdampft und es fällt ein außerordentlich feinkörniges Legierungspulver aus, welches für die Herstellung des erfindungsgemäßen Werkstoffes besonderes geeignet ist.A particularly advantageous method for producing the material according to the invention is the subject of claim 13. Advantageous further developments of this method are specified in the further subclaims. According to this process, a silver powder, a base metal powder and a graphite powder are not mixed with one another and pressed to form shaped bodies, but instead a powder of a precipitation alloy made of silver is produced with the base metal and this is mixed with graphite powder; molded bodies are then pressed, sintered and post-compressed therefrom, the compression being so strong that the pore volume is less than 2%. A particularly suitable method for obtaining such an alloy powder is spray pyrolysis (US-A-3 510 291, EP-0012 202 A1, DE-29 29 630 C2). A solution which contains a silver salt and one or more base metal salts in solution is sprayed into a hot reaction vessel. The salts are decomposed therein and the solvent evaporated, and an extraordinarily fine-grained alloy powder precipitates, which is particularly suitable for the production of the material according to the invention.
- 1. Durch Verdüsen einer schmelzflüssigen Legierung aus Silber mit 20 Gew.-% Kupfer wird ein AgCu20-Pulver mit einer mittleren Teilchengröße von höchstens 10 µm erzeugt. 96 Gew.-Teile dieses Legierungspulvers werden mit 4 Gew.-Teilen eines feinen Graphitpulvers (mittlere Teilchengröße ungefähr 1 µm) gemischt. Aus der Pulvermischung werden durch kaltisostatisches Pressen mit einem Druck von 5·10⁻⁷ N·m⁻² Formkörper gepreßt, bei einer Temperatur von 700° C eine Stunde lang in Stickstoffatmosphäre gesintert und anschließend durch Strangpressen mit einem Umformverhältnis von 30:1 unter Nachverdichtung zu einem flachen Rechteckprofil umgeformt.1. By spraying a molten alloy of silver with 20 wt .-% copper, an AgCu20 powder with an average particle size of at most 10 microns is generated. 96 parts by weight of this alloy powder are mixed with 4 parts by weight of a fine graphite powder (average particle size approximately 1 μm). Shaped bodies are pressed from the powder mixture by cold isostatic pressing at a pressure of 5 · 10 · N · m⁻², sintered at a temperature of 700 ° C for one hour in a nitrogen atmosphere and then by extrusion with a forming ratio of 30: 1 with post-compression formed into a flat rectangular profile.
- 2. Eine gemeinsame Lösung von Silbernitrat und Kupfernitrat in Wasser wird mittels eines inerten Treibgases (z.B. Argon) in ein heißes Reaktionsgefäß eingesprüht, dessen Wandtemperatur unterhalb der Schmelztemperatur des Silbers und unterhalb der Schmelztemperatur des Kupfers liegt, beispielsweise bei 950° C, und in dem eine inerte Atmosphäre (z.B. Argon) vorliegt. In dem heißen Reaktionsgefäß zerfallen das Silbernitrat und das Kupfernitrat, das Wasser verdampft, und das freiwerdende Silber und Kupfer verbinden sich zu kleinen Teilchen, die ausfallen und ausgetragen werden. Es entsteht auf diese Weise ein Silber-Kupfer-Legierungspulver mit einer mittleren Teilchengröße von ungefähr 1 µm, wobei sich die Legierungszusammensetzung nach dem Gehalt der Lösung an Silbernitrat und Kupfernitrat richtet. Dieses Silberlegierungspulver kann wie im ersten Beispiel mit Graphitpulver gemischt und weiterverarbeitet werden.2. A common solution of silver nitrate and copper nitrate in water is sprayed by means of an inert propellant (eg argon) into a hot reaction vessel, the wall temperature of which is below the melting temperature of the silver and below the melting temperature of the copper, for example at 950 ° C., and in that there is an inert atmosphere (e.g. argon). In the hot reaction vessel, the silver nitrate and the copper nitrate, the water evaporates, and the released silver and copper combine to form small particles that precipitate and are discharged. This produces a silver-copper alloy powder with an average particle size of approximately 1 μm, the alloy composition depending on the silver nitrate and copper nitrate content of the solution. As in the first example, this silver alloy powder can be mixed with graphite powder and processed further.
Claims (15)
- Powder-metallurgically manufactured material for electric contacts made of silver with 2 to 7 % by weight graphite and with an additive which increases the strength of the material, characterized in that the additive consists of 0.5 to 50 % by weight of one or more base metals, which are present in the material as particles having sizes not in excess of 5 x 10⁻¹⁰ mm³ and in a uniform distribution.
- A material according to claim 1, characterized in that the base metal particles are smaller than 0.5 x 10⁻¹⁰ mm³.
- A material according to claim 1 or 2, characterized in that the silver is present as particles having a size not in excess of 5 x 10⁻¹⁰mm³, preferably not in excess of 0.5 x 10⁻¹⁰ mm³.
- A material according to any of the preceding claims, characterized in that its base metal content is 10 to 25% by weight.
- A process according to any of the preceding claims, characterized in that one or more of the metals of the group consisting of copper, nickel, iron, manganese, zinc, tungsten and molybdenum have been selected as base metals.
- A material according to any of the preceding claims, characterized in that such base metals have been selected which have a higher melting point than silver.
- A material according to any of the preceding claims, characterized in that such base metals have been selected which at 20°C have an electrical conductivity of at least 10 milliohm⁻¹mm⁻².
- A material according to any of the proceeding claims, characterized in that such base metals have been selected which at 20°C do not form an alloy with silver or, at best, form an alloy with silver by coprecipitation.
- A material according to any of the preceding claims, characterized in that copper has been selected as a base metal.
- A material according to claim 9, characterized in that a part of the copper is present as copper oxide (CuO).
- A material according to any of the preceding claims, characterized in that it has a porosity of less than 2%.
- A process of manufacturing a material according to any of the preceding claims in that a powder mixture is formed and is compacted to form shaped bodies, which are sintered and recompacted, characterized in that the powder mixture is formed in that a powder is produced which consists of a coprecipitated alloy of silver and the base metal and that alloy powder is mixed with the graphite powder.
- A process according to claim 12, characterized in that the shaped bodies are formed by cold isostatic pressing.
- A process according to claim 12 or 13, characterized in that the shaped bodies are recompacted by being extruded.
- A process according to any of claims 12 to 14, characterized in that the alloy powder is produced by a spraying and reacting process, in which a solution that contains a silver salt and a solution that contains one or more base metal salts are simultaneously sprayed in a hot reaction vessel.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AT88116746T ATE77657T1 (en) | 1987-10-09 | 1988-10-10 | POWDER METALLURGICALLY MANUFACTURED MATERIAL FOR ELECTRICAL CONTACTS MADE OF SILVER WITH GRAPHITE AND PROCESS FOR ITS MANUFACTURE. |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3734178 | 1987-10-09 | ||
| DE19873734178 DE3734178A1 (en) | 1987-10-09 | 1987-10-09 | POWDER METALLICALLY PRODUCED MATERIAL FOR ELECTRICAL CONTACTS MADE OF SILVER WITH GRAPHITE AND METHOD FOR THE PRODUCTION THEREOF |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0311134A1 EP0311134A1 (en) | 1989-04-12 |
| EP0311134B1 true EP0311134B1 (en) | 1992-06-24 |
Family
ID=6337969
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP88116746A Expired - Lifetime EP0311134B1 (en) | 1987-10-09 | 1988-10-10 | Powder-metallurgically produced electrical contact material comprising silver and graphite, and process for producing it |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0311134B1 (en) |
| AT (1) | ATE77657T1 (en) |
| DD (1) | DD275421A5 (en) |
| DE (2) | DE3734178A1 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3806573A1 (en) * | 1988-03-01 | 1989-09-14 | Siemens Ag | Pair of contacts |
| DE10318890B4 (en) * | 2003-04-17 | 2014-05-08 | Ami Doduco Gmbh | Electrical plug contacts and a semi-finished product for their production |
| CN105648261B (en) * | 2016-02-01 | 2018-02-16 | 重庆川仪自动化股份有限公司 | Silver-based commutator material and preparation method and purposes for high-voltage great-current |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CH301201A (en) * | 1944-11-14 | 1954-08-31 | Licentia Gmbh | Contact material for frequently operated contacts. |
| GB1059872A (en) * | 1963-06-04 | 1967-02-22 | Mitsuo Iwauchi | Method for manufacturing electrical material |
| DE2141409A1 (en) * | 1971-08-18 | 1973-03-01 | Ts Ni Awtomobil Nij I Awtomoto | METAL-CERAMIC SUBSTANCE FOR ELECTRICAL CONTACTS AND PROCESS FOR ITS PRODUCTION |
| DE2929630C2 (en) * | 1979-07-21 | 1983-12-15 | Dornier System Gmbh, 7990 Friedrichshafen | Process for the production of silver powder |
| US4699763A (en) * | 1986-06-25 | 1987-10-13 | Westinghouse Electric Corp. | Circuit breaker contact containing silver and graphite fibers |
-
1987
- 1987-10-09 DE DE19873734178 patent/DE3734178A1/en not_active Withdrawn
-
1988
- 1988-10-10 EP EP88116746A patent/EP0311134B1/en not_active Expired - Lifetime
- 1988-10-10 AT AT88116746T patent/ATE77657T1/en not_active IP Right Cessation
- 1988-10-10 DD DD88320604A patent/DD275421A5/en not_active IP Right Cessation
- 1988-10-10 DE DE8888116746T patent/DE3872338D1/en not_active Expired - Lifetime
Non-Patent Citations (1)
| Title |
|---|
| METAL HANDBOOK, Ninth Edition, Vol. 3, Dezember 1980, Metals Park, Ohio - W.H. Cubberly et al. "Electric-Contact Materials" Seiten 662, 672-681 * |
Also Published As
| Publication number | Publication date |
|---|---|
| DD275421A5 (en) | 1990-01-24 |
| DE3734178A1 (en) | 1989-04-20 |
| DE3872338D1 (en) | 1992-07-30 |
| EP0311134A1 (en) | 1989-04-12 |
| ATE77657T1 (en) | 1992-07-15 |
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