EP0370897A1 - Method for the preparation of electrical contact material, and method of making a contact element incorporating such a material - Google Patents

Method for the preparation of electrical contact material, and method of making a contact element incorporating such a material Download PDF

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Publication number
EP0370897A1
EP0370897A1 EP89403211A EP89403211A EP0370897A1 EP 0370897 A1 EP0370897 A1 EP 0370897A1 EP 89403211 A EP89403211 A EP 89403211A EP 89403211 A EP89403211 A EP 89403211A EP 0370897 A1 EP0370897 A1 EP 0370897A1
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EP
European Patent Office
Prior art keywords
silver
oxide
approximately
contact
temperature
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Granted
Application number
EP89403211A
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German (de)
French (fr)
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EP0370897B1 (en
Inventor
Gérard Fontet
Michel Leclercq
Jacques Muniesa
Thierry Pagnier
René Tretarre
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Telemecanique SA
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Telemecanique Electrique SA
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Classifications

    • 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
    • H01H1/0237—Composite material having a noble metal as the basic material and containing oxides
    • H01H1/02372—Composite material having a noble metal as the basic material and containing oxides containing as major components one or more oxides of the following elements only: Cd, Sn, Zn, In, Bi, Sb or Te
    • H01H1/02376—Composite material having a noble metal as the basic material and containing oxides containing as major components one or more oxides of the following elements only: Cd, Sn, Zn, In, Bi, Sb or Te containing as major component SnO2
    • 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
    • B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
    • B22F9/20—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from solid metal compounds
    • B22F9/22—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from solid metal compounds using gaseous reductors
    • 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
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/12—Both compacting and sintering
    • B22F3/16—Both compacting and sintering in successive or repeated steps
    • B22F3/164—Partial deformation or calibration
    • B22F2003/166—Surface calibration, blasting, burnishing, sizing, coining
    • 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
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/24—After-treatment of workpieces or articles
    • B22F2003/248—Thermal after-treatment
    • 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
    • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
    • B22F2998/10—Processes characterised by the sequence of their steps

Definitions

  • the present invention relates generally to the manufacture of electrical contacts, for example in the form of pads, suitable for use in switching devices with successive openings and closings.
  • It relates more precisely to improvements to a process for preparing a contact material and to the manufacture of contact elements such as pellets, bars or the like incorporating such a material.
  • the most frequently used contact materials in low-voltage electromechanical devices are silver / metal oxide composite materials, denoted AgMeO n .
  • Silver is an excellent electrical conductor, does not oxidize in air and has sufficient malleability to withstand without damage the many mechanical shocks to which it is exposed in such an environment.
  • the metal oxide is present mainly to reduce the risks of welding compared to the case where pure silver is used.
  • these composite materials have lower rates of arc erosion than that of pure silver.
  • the object of the present invention is to overcome these drawbacks of the prior art and to propose a preparation process which makes it possible to obtain a contact material of the Ag-SnO type type having improved properties.
  • the Applicant despite the drawbacks linked to the use of SnO2 alone in the silver-based composite material, as mentioned above, continued its research on the AgSnOn composite material and discovered that, under certain conditions , one could obtain with an AgSnO2 composite a mechanical and electrical behavior at least as satisfactory as that of AgCdO, and this without the need to add additional oxides such as WO3 or MoO3 to avoid arc problems .
  • the present invention mainly relates to a process for the preparation of a contact material consisting of silver and tin oxide, characterized in that it comprises the steps consisting in: - Prepare an aqueous solution containing dissolved silver nitrate and suspended tin oxide particles, the size of said particles, measured in terms of specific surface area according to the BET method, being between approximately 2 and 6 m2 / g , - precipitate the silver nitrate into silver hydroxide by rapid addition of a strong base and stirring, silver hydroxide, unstable, gradually transforming into silver oxide, - remove the ions in solution, then the water, to obtain a dry product, and - heat the dry product to a temperature of around 200 to 500 ° C to reduce the silver oxide to silver metal.
  • Preferred aspects of the preparation process according to the invention are also the following: - in the final contact material, the silver is present in a proportion of the order of 84 to 92% by weight, the remainder being tin oxide, - the strong base is concentrated soda, - The step of heating the dry product is carried out at a temperature and for a duration such that it leads to an agglomeration of silver and tin oxide.
  • the invention also relates to the manufacture of contact elements incorporating the material prepared by the above process, as well as a thin underlay of pure silver. More specifically, a method is proposed, characterized in that the material and the undercoat are subjected to the following operations: - compression at around 3t / cm2; - sintering for 30 to 40 min at a temperature of the order of 840 ° C; - first calibration at around 10 t / cm2; - first annealing for approximately 30 minutes at approximately 900 ° C; - second calibration at around 12 t / cm2; and - second annealing for approximately 30 minutes at approximately 940 ° C.
  • a manufacturing process is also proposed, characterized in that it comprises the steps consisting in: - add a small proportion of copper oxide to the prepared material, - compress the material obtained with said undercoat to shape said element, and heat said element to a temperature between 940 and 960 ° C, to lead to the formation of a minority liquid phase in which the element is sintered.
  • Preferred aspects of this manufacturing process are: - copper oxide is added to the material prepared by adding copper nitrate to the aqueous solution, which, during the precipitation step, precipitates into copper hydroxide, which transforms into copper oxide, - copper oxide is present in the prepared material in a proportion of the order of 0.1 to 1.0% by weight, - it includes a subsequent compression calibration step, - it includes a final stress relieving annealing step, - For the manufacture of bars, it further comprises at least one succession of rolling and annealing steps.
  • the research carried out by the Applicant has made it possible to discover that it is possible to produce contact elements made of AgSnO2 silver-tin oxide composite material having performances equivalent or superior to those of silver-cadmium oxide contacts, both in as regards the welds as erosion, and this with contact resistances lowered to acceptable levels.
  • Requirements (a) and (c) appear to be antagonistic, hence the need to find a compromise by playing in particular on the size of the tin oxide grains, the size of the silver grains simultaneously remaining relatively small.
  • the pellet is very hard and therefore very brittle, with a high contact resistance and therefore a risk of overheating, but nevertheless with a very low dynamic weld risk.
  • the grains of Sn02 are larger, the pellet is more malleable and withstands impact well, and the contact resistance becomes weaker; but the risks of dynamic welding are then greatly increased.
  • an aqueous phase precipitation process of the silver oxide in an aqueous suspension of tin oxide powder is used. having the specified particle size.
  • a silver and tin oxide powder is prepared according to a method of precipitation in aqueous phase of the silver oxide Ag20 in a suspension of tin oxide powder having the particle size indicated above.
  • the principle is as follows: the desired quantity of powdered tin oxide is added to an aqueous solution of silver nitrate.
  • the silver oxide is precipitated by adding a strong base such as sodium hydroxide to this solution, which gives the following reaction: (AgNO3) + (NaOH) ⁇ ⁇ AgOH> + (NaNO3) (1) or () designates the species in solution and ⁇ > designates insoluble species.
  • the silver hydroxide AgOH is unstable and subsequently gives silver oxide, according to the following reaction: 2 ⁇ AgOH> ⁇ ⁇ Ag2O> + (H2O) (2)
  • the product obtained is a suspension of Ag2O (and optionally, depending on the degree of evolution of reaction (2), AgOH) and SnO2 in water with a high content of Na+ and NO3 ⁇ ions.
  • the silver oxide In the powder obtained, it is then necessary to convert the silver oxide into silver metal. This operation is carried out by reducing heat treatment of the silver oxide, at a temperature of the order of 200 to 500 ° C. This step also allows agglomeration of the powder, which advantageously makes it distributable in an automatic machine.
  • the amounts of silver nitrate and tin oxide in the starting solution are such that, in the final material, there are approximately 84 to 92% by weight of silver, the balance being tin oxide.
  • a contact pad is conventionally made up of a sub-layer of pure silver, with a thickness of the order of a few hundred ⁇ m, which makes it possible to braze the pad on its support, and of a layer of material. contact, for example from 1 to 3 mm thick.
  • This process is advantageous in that the density gains are obtained essentially during the compression and calibration operations. This means that the high temperature sintering of the material is very slow, and that few bonds form between the silver grains. The brittleness of the pellet obtained is certainly increased, but remains low enough for the electrical behavior to be better than with a contact material of the silver-cadmium oxide type.
  • a liquid sintering technique is used according to the invention, which makes it possible to considerably increase the sintering speeds and the quality of the sintered product obtained.
  • the formation of a liquid phase is obtained by adding to the composite, before sintering, copper oxide CuO. It was not possible to determine whether the liquid formed was an Ag-O or Ag-Cu-O mixture, but it was nevertheless verified that the liquid phase then formed in air at around 940 ° C, or 20 ° C below the silver melting temperature.
  • the copper oxide is added in a proportion of between 0.1 and 1.0% by weight, for example of the order of 0.2%.
  • a remarkable sintering of the pellets is then observed by bringing them to a temperature between the temperature of formation of the liquid, ie 940 ° C., and the melting temperature of the silver, ie 960 ° C.
  • a temperature of the order of 940 to 950 ° C. In a few minutes, the actual density of the Ag-SnO2 mixture becomes practically equal to its theoretical density.
  • a very malleable material is obtained, which makes it possible to considerably simplify the subsequent operations, such as for example the calibration of the individual pellets or the lamination of bars.
  • the copper oxide is added in the desired proportion during the precipitation described above in connection with the process for obtaining the contact material.
  • the necessary quantity of copper is added in the form of copper nitrate Cu (NO3) 2 which is dissolved together with the silver nitrate. Analogously to what happens to silver, it is formed during the reaction with sodium hydroxide copper hydroxide Cu (OH) 2, which will transform into CuO during heat treatments of the powder.
  • the copper oxide is added in an amount sufficient for the sintering to take place in the liquid phase, but that this amount is so small that the copper oxide has little influence on the electrical behavior of the pellet or bar obtained.
  • a series of advantageous steps can be as follows: - compression at 3 t / cm2, - liquid phase sintering at 940 ° C, - calibration at 12 t / cm2.
  • the following sequence of steps can be used: - compression at around 2 to 3 t / cm2, - liquid phase sintering at 940 ° C, - succession of rolling-annealing to obtain the desired section, - cutting of the pellets.
  • the pellets all had the same dimensions.
  • Test 100A the opening of the contact was carried out under a current of 100 A effective and the closing under a current of 600 A effective, with a predetermined rebound identical for all the samples.
  • the force necessary to open the contacts was measured (welding force dynamic), the contact resistance and three times during the test, the contact erosion was determined, determined in terms of weight loss at each closing / opening, by weighing.
  • the pellets produced in accordance with the invention are greater than at least one of the pellets of the prior art, this superiority being most marked for the 1000 A test.

Abstract

L'invention concerne un procédé de préparation d'un matériau de contact constitué par de l'argent et de l'ooxyde d'étain. Selon l'invention, il comprend les étapes consistant à : - préparer une solution aqueuse contenant du nitrate d'argent dissout et des particules d'oxyde d'étain en suspension, la taille desdites particules, mesurée en termes de surface spécifique selon la méthode BET, étant comprise entre environ 2 et 6 m²/g, - faire précipiter le nitrate d'argent en hydroxyde d'argent par addition rapide d'une base forte et brassage, l'hydroxyde d'argent, instable, se formant progressivement en oxyde d'argent, - éliminer les ions en solution, puis l'eau, pour obtenir un produit sec, - chauffer le produit sec à une température d'environ 200 à 500°C pour réduire l'oxyde d'argent en argent métal. Application à la fabrication de contacts électriques d'ouverture-fermeture dans les appareils électromécaniques.The invention relates to a method for preparing a contact material consisting of silver and tin oxide. According to the invention, it comprises the stages consisting in: - preparing an aqueous solution containing dissolved silver nitrate and suspended tin oxide particles, the size of said particles, measured in terms of specific surface according to the method BET, being between approximately 2 and 6 m² / g, - precipitate the silver nitrate into silver hydroxide by rapid addition of a strong base and stirring, the silver hydroxide, unstable, gradually forming in silver oxide, - remove the ions in solution, then water, to obtain a dry product, - heat the dry product to a temperature of about 200 to 500 ° C to reduce the silver oxide to silver metal . Application to the manufacture of electrical opening-closing contacts in electromechanical devices.

Description

La présente invention a trait d'une façon générale à la fabrication de contacts électriques, par exemple sous forme de pastilles, appropriés pour être utilisés dans des dispositifs de commutation à ouvertures et fermetures successives.The present invention relates generally to the manufacture of electrical contacts, for example in the form of pads, suitable for use in switching devices with successive openings and closings.

Elle concerne plus précisément des perfectionnements à un procédé de préparation d'un matériau de contact et à la fabrication d'éléments de contact tels que des pastilles, barreaux ou analogues incorporant un tel matériau.It relates more precisely to improvements to a process for preparing a contact material and to the manufacture of contact elements such as pellets, bars or the like incorporating such a material.

Lors de l'ouverture ou de la fermeture sous courant d'un appareil de commande électromécanique, il se produit un arc électrique. Les établissements répétés de tels arcs sont désavantageux en ce qu'ils provoquent une érosion progressive des contacts, ainsi qu'une modification de la composition des surfaces de contact, qui conduit elle-même à des variations de la résistance de contact et donc à des risques d'échauffement, indésirables du point de vue de la sécurité. En outre et surtout, la présence de tels arcs à la fermeture risque de provoquer un collage ou soudure dynamique des deux éléments de contact.When an electromechanical control device is opened or closed under current, an electric arc occurs. The repeated establishment of such arcs is disadvantageous in that it causes a progressive erosion of the contacts, as well as a modification of the composition of the contact surfaces, which itself leads to variations in the contact resistance and therefore to risk of overheating, undesirable from a safety point of view. In addition and above all, the presence of such arcs at closure risks causing dynamic bonding or welding of the two contact elements.

Les matériaux de contact les plus fréquemment utilisés dans les appareils électromécaniques à basse tension sont des matériaux composites argent/oxyde métallique, notés AgMeOn. L'argent est un excellent conducteur électrique, ne s'oxyde pas à l'air et possède une malléabilité suffisante pour supporter sans dommages les nombreux chocs mécaniques auquels il est exposé dans un tel environnement. L'oxyde métallique est présent principalement pour diminuer les risques de soudure par rapport au cas où l'on utilise de l'argent pur. Par ailleurs, ces matériaux composites présentent des taux d'érosion par l'arc inférieurs à celui de l'argent pur.The most frequently used contact materials in low-voltage electromechanical devices are silver / metal oxide composite materials, denoted AgMeO n . Silver is an excellent electrical conductor, does not oxidize in air and has sufficient malleability to withstand without damage the many mechanical shocks to which it is exposed in such an environment. The metal oxide is present mainly to reduce the risks of welding compared to the case where pure silver is used. Furthermore, these composite materials have lower rates of arc erosion than that of pure silver.

Jusqu'à présent, la plupart des contacts des appareils de commande de puissance étaient réalisés en matériau composite argent oxyde de cadmium (AgCdO). Mais du fait de la toxicité du cadmium, et également pour améliorer la qualité des matériaux, on a cherché à remplacer le cadmium par un autre métal. L'étain s'est révélé convenable sur un certain nombre de points.Until now, most of the contacts of power control devices have been made of silver cadmium oxide (AgCdO) composite material. But because of the toxicity of cadmium, and also to improve the quality of materials, we sought to replace the cadmium by another metal. Tin has proven to be suitable on a number of points.

Cependant, il s'est avéré que les matériaux AgSnO₂ avaient tendance à provoquer une augmentation de l'échauffement dans les appareils, à cause d'un accroissement de la résistance de contact entre deux pastilles en vis-à-vis.However, it turned out that AgSnO₂ materials tended to cause an increase in heating in the devices, due to an increase in the contact resistance between two pellets facing each other.

C'est pour pallier cet inconvénient que l'on ajoute à l'élément de contact, de façon connue, un autre oxyde, généralement WO₃ ou MoO₃.It is to overcome this drawback that we add to the contact element, in known manner, another oxide, generally WO₃ or MoO₃.

Cet ajout est cependant désavantageux en ce qu'il complique la fabrication des contacts et la rend plus coûteuse .This addition is however disadvantageous in that it complicates the manufacture of the contacts and makes it more expensive.

La présente invention a pour but de pallier ces inconvénients de la technique antérieure et de proposer un procédé de préparation qui permette d'obtenir un matériau de contact de type Ag-SnO₂ ayant des propriétés améliorées.The object of the present invention is to overcome these drawbacks of the prior art and to propose a preparation process which makes it possible to obtain a contact material of the Ag-SnO type type having improved properties.

Plus précisément, la Demanderesse, malgré les inconvénients liés à l'emploi de SnO₂ seul dans le matériau composite à base d'argent, tels que mentionnés plus haut, a poursuivi ses recherches sur le matériau composite AgSnO₂ et a découvert que, sous certaines conditions, l'on pouvait obtenir avec un composite AgSnO₂ un comportement mécanique et électrique au moins aussi satisfaisant que celui de AgCdO, et ceci sans qu'il soit nécessaire d'ajouter des oxydes additionels tels que WO₃ ou MoO₃ pour éviter les problèmes d'arcs.More specifically, the Applicant, despite the drawbacks linked to the use of SnO₂ alone in the silver-based composite material, as mentioned above, continued its research on the AgSnOn composite material and discovered that, under certain conditions , one could obtain with an AgSnO₂ composite a mechanical and electrical behavior at least as satisfactory as that of AgCdO, and this without the need to add additional oxides such as WO₃ or MoO₃ to avoid arc problems .

Ainsi, la présente invention concerne principalement un procédé de préparation d'un matériau de contact constitué par de l'argent et de l'oxyde d'étain, caractérisé en ce qu'il comprend les étapes consistant à :
- préparer une solution aqueuse contenant du nitrate d'argent dissout et des particules d'oxyde d'étain en suspension, la taille desdites particules, mesurée en termes de surface spécifique selon la méthode BET, étant comprise entre environ 2 et 6 m²/g,
- faire précipiter le nitrate d'argent en hydroxyde d'argent par addition rapide d'une base forte et brassage, l'hydroxyde d'argent, instable, se transformant progressivement en oxyde d'argent,
- éliminer les ions en solution, puis l'eau, pour obtenir un produit sec, et
- chauffer le produit sec à une température d'environ 200 à 500°C pour réduire l'oxyde d'argent en argent métal.Thus, the present invention mainly relates to a process for the preparation of a contact material consisting of silver and tin oxide, characterized in that it comprises the steps consisting in:
- Prepare an aqueous solution containing dissolved silver nitrate and suspended tin oxide particles, the size of said particles, measured in terms of specific surface area according to the BET method, being between approximately 2 and 6 m² / g ,
- precipitate the silver nitrate into silver hydroxide by rapid addition of a strong base and stirring, silver hydroxide, unstable, gradually transforming into silver oxide,
- remove the ions in solution, then the water, to obtain a dry product, and
- heat the dry product to a temperature of around 200 to 500 ° C to reduce the silver oxide to silver metal.

Des aspect préférés du procédé de préparation selon l'invention sont en outre les suivants :
- dans le matériau de contact final, l'argent est présent en une proportion de l'ordre de 84 à 92% en poids, le reste étant de l'oxyde d'étain,
- la base forte est de la soude concentrée,
- l'étape de chauffage du produit sec est effectuée à une température et pendant une durée telles qu'elle conduit à une agglomération de l'argent et de l'oxyde d'étain.Preferred aspects of the preparation process according to the invention are also the following:
- in the final contact material, the silver is present in a proportion of the order of 84 to 92% by weight, the remainder being tin oxide,
- the strong base is concentrated soda,
- The step of heating the dry product is carried out at a temperature and for a duration such that it leads to an agglomeration of silver and tin oxide.

L'invention concerne également la fabrication d'éléments de contact incorporant le matériau préparé par le procédé ci-dessus, ainsi qu'une sous-couche mince d'argent pur. Plus précisément, il est proposé un procédé caractérisé en ce qu'on soumet le matériau et la sous-couche aux opérations suivantes :
- compression à environ 3t/cm²;
- frittage pendant 30 à 40 mn à une température de l'ordre de 840°C;
- premier calibrage à environ 10 t/cm²;
- premier recuit pendant environ 30 mn à environ 900°C;
- second calibrage à environ 12 t/cm²; et
- second recuit pendant environ 30 mn à environ 940°C.The invention also relates to the manufacture of contact elements incorporating the material prepared by the above process, as well as a thin underlay of pure silver. More specifically, a method is proposed, characterized in that the material and the undercoat are subjected to the following operations:
- compression at around 3t / cm²;
- sintering for 30 to 40 min at a temperature of the order of 840 ° C;
- first calibration at around 10 t / cm²;
- first annealing for approximately 30 minutes at approximately 900 ° C;
- second calibration at around 12 t / cm²; and
- second annealing for approximately 30 minutes at approximately 940 ° C.

Il est également proposé un procédé de fabrication caractérisé en ce qu'il comprend les étapes consistant à :
- ajouter au matériau préparé une faible proportion d'oxyde de cuivre,
- comprimer le matériau obtenu avec ladite sous-­couche pour mettre en forme ledit élément, et chauffer ledit élément à une température comprise entre 940 et 960°C, pour conduire à la formation d'une phase liquide minoritaire dans laquelle l'élément est fritté.A manufacturing process is also proposed, characterized in that it comprises the steps consisting in:
- add a small proportion of copper oxide to the prepared material,
- compress the material obtained with said undercoat to shape said element, and heat said element to a temperature between 940 and 960 ° C, to lead to the formation of a minority liquid phase in which the element is sintered.

Des aspects préférés de ce procédé de fabrication sont les suivants :
- l'oxyde de cuivre est ajouté au matériau préparé par addition de nitrate de cuivre dans la solution aqueuse, qui, lors de l'étape de précipitation, précipite en hydroxyde de cuivre, lequel se transforme en oxyde de cuivre,
- l'oxyde de cuivre est présent dans le matériau préparé en une proportion de l'ordre de 0,1 à 1,0% en poids,
- il comprend une étape ultérieure de calibrage par compression,
- il comprend une étape finale de recuit de libération des contraintes,
- pour la fabrication de barreaux, il comprend en outre au moins une succession d'étapes de laminage et de recuit.Preferred aspects of this manufacturing process are:
- copper oxide is added to the material prepared by adding copper nitrate to the aqueous solution, which, during the precipitation step, precipitates into copper hydroxide, which transforms into copper oxide,
- copper oxide is present in the prepared material in a proportion of the order of 0.1 to 1.0% by weight,
- it includes a subsequent compression calibration step,
- it includes a final stress relieving annealing step,
- For the manufacture of bars, it further comprises at least one succession of rolling and annealing steps.

D'autres aspects, buts et avantages de la présente invention apparaîtront mieux à la lecture de la description détaillée suivante de formes de réalisation préférées de celle-ci, donnée à titre d'exemple non limitatif.Other aspects, aims and advantages of the present invention will appear better on reading the following detailed description of preferred embodiments thereof, given by way of nonlimiting example.

Les recherches menées par la Demanderesse ont permis de découvrir qu'il était possible de réaliser des éléments de contact en matériau composite argent-oxyde d'étain AgSnO₂ présentant des performances équivalentes ou supérieures à celles des contacts en argent-oxyde de cadmium, tant en ce qui concerne les soudures que l'érosion, et ceci avec des résistances de contact abaissées jusqu'à des niveaux acceptables.The research carried out by the Applicant has made it possible to discover that it is possible to produce contact elements made of AgSnO₂ silver-tin oxide composite material having performances equivalent or superior to those of silver-cadmium oxide contacts, both in as regards the welds as erosion, and this with contact resistances lowered to acceptable levels.

Conformément à un aspect essentiel de la présente invention, ces caractéristiques avantageuses sont obtenues :

  • (a) en utilisant des grains d'argent et d'oxyde d'étain très fins, avec une taille de grains de l'ordre du micron ou moins, et
  • (b) en effectuant une dispersion très poussée des deux constituants.
In accordance with an essential aspect of the present invention, these advantageous characteristics are obtained:
  • (a) using very fine silver and tin oxide grains, with a grain size of the order of one micron or less, and
  • (b) by carrying out a very thorough dispersion of the two constituents.

Dans le même temps, il est nécessaire (c) de choisir une taille de grains assez grosse pour que les caractéristiques mécaniques de la pastille soient convenables, et en particulier qu'elle résiste aux chocs mécaniques en ne présentant pas une dureté trop élevée.At the same time, it is necessary (c) to choose a sufficiently large grain size so that the mechanical characteristics of the pellet are suitable, and in particular that it resists mechanical shock by not having too high a hardness.

Les exigences (a) et (c) apparaissent antagonistes, d'où la nécessite de trouver un compromis en jouant en particulier sur la taille des grains d'oxyde d'étain, la taille des grains d'argent restant simultanément relativement petite.Requirements (a) and (c) appear to be antagonistic, hence the need to find a compromise by playing in particular on the size of the tin oxide grains, the size of the silver grains simultaneously remaining relatively small.

Plus précisément, si les grains de SnO₂ sont très fins, la pastille est très dure et donc très cassante, avec une résistance de contact élevée et donc un risque d'échauffement, mais cependant avec un risque de soudure dynamique très réduit. Au contraire , si les grains de Sn0₂ sont plus gros, la pastille est plus malléable et résiste bien aux chocs, et la résistance de contact devient plus faible; mais les risques de soudure dynamique sont alors fortement accrus.More precisely, if the SnO₂ grains are very fine, the pellet is very hard and therefore very brittle, with a high contact resistance and therefore a risk of overheating, but nevertheless with a very low dynamic weld risk. On the contrary, if the grains of Sn0₂ are larger, the pellet is more malleable and withstands impact well, and the contact resistance becomes weaker; but the risks of dynamic welding are then greatly increased.

Les études de la Demanderesse ont démontré qu'un compromis satisfaisant était obtenu en utilisant pour la préparation du matériau une poudre de SnO₂ dont la taille de particules, mesurée en termes de surface spécifique selon méthode BET, va de 2 à 6 m²/g.The Applicant's studies have demonstrated that a satisfactory compromise was obtained by using SnO₂ powder for the preparation of the material, the particle size of which, measured in terms of specific surface area according to BET method, ranges from 2 to 6 m² / g.

Conformément à un aspect essentiel de la présente invention, pour otenir également une finesse appropriée des grains d'argent, on utilise un processus de précipitation en phase aqueuse de l'oxyde d'argent dans une suspension aqueuse de poudre d'oxyde d'étain ayant la granulométrie spécifiée.In accordance with an essential aspect of the present invention, to also obtain an appropriate fineness of the silver grains, an aqueous phase precipitation process of the silver oxide in an aqueous suspension of tin oxide powder is used. having the specified particle size.

On va décrire ci-dessus un exemple d'une mise en oeuvre concrète de ce procédé de préparation.We will describe above an example of a concrete implementation of this preparation process.

EXEMPLEEXAMPLE

Une poudre d'argent et d'oxyde d'étain est préparée selon un procédé de précipitation en phase aqueuse de l'oxyde d'argent Ag₂0 dans une suspension de poudre d'oxyde d'étain ayant la granulométrie indiquée plus haut.A silver and tin oxide powder is prepared according to a method of precipitation in aqueous phase of the silver oxide Ag₂0 in a suspension of tin oxide powder having the particle size indicated above.

Le principe en est le suivant : on ajoute à une solution aqueuse de nitrate d'argent la quantité désirée d'oxyde d'étain en poudre. La précipitation de l'oxyde d'argent s'effectue en ajoutant à cette solution une base forte telle que de la soude, ce qui donne la réaction suivante :
(AgNO₃) + (NaOH)→<AgOH> + (NaNO₃)      (1)
où
( ) désigne les espèces en solution et
< > désigne les espèces insolubles.The principle is as follows: the desired quantity of powdered tin oxide is added to an aqueous solution of silver nitrate. The silver oxide is precipitated by adding a strong base such as sodium hydroxide to this solution, which gives the following reaction:
(AgNO₃) + (NaOH) → <AgOH> + (NaNO₃) (1)
or
() designates the species in solution and
<> designates insoluble species.

L'hydroxyde d'argent AgOH est instable et donne par la suite de l'oxyde d'argent, selon la réaction suivante :
2<AgOH>→<Ag₂O> + (H₂O)      (2)The silver hydroxide AgOH is unstable and subsequently gives silver oxide, according to the following reaction:
2 <AgOH> → <Ag₂O> + (H₂O) (2)

Afin d'obtenir des grains fins d'Ag₂O, il est nécessaire suivant ce procédé :
- d'opérer à basse température, par exemple de l'ordre de 0 à 40°C, et notamment à température ambiante,
- d'utiliser des solutions très concentrées,
- de faire réagir la soude avec le nitrate d'argent de façon rapide et homogène, ce qui nécessite un brassage continu de la solution et un apport rapide de la soude.In order to obtain fine grains of Ag₂O, it is necessary according to this process:
to operate at low temperature, for example of the order of 0 to 40 ° C., and in particular at ambient temperature,
- to use very concentrated solutions,
- To react the soda with the silver nitrate quickly and homogeneously, which requires continuous stirring of the solution and a rapid supply of soda.

Après la réaction, le produit obtenu est une suspension de Ag₂O (et éventuellement, selon le degré d'évolution de la réaction (2), de AgOH) et de SnO₂ dans une eau à forte teneur en ions Na⁺ et NO₃⁻.After the reaction, the product obtained is a suspension of Ag₂O (and optionally, depending on the degree of evolution of reaction (2), AgOH) and SnO₂ in water with a high content of Na⁺ and NO₃⁻ ions.

On élimine ces ions par une succession de lavages et de séparations.These ions are eliminated by a succession of washes and separations.

Après la dernière séparation, on obtient une pâte contenant de 20 à 95% d'eau, qui est éliminée par séchage, selon tout procédé approprié tel que séchage en étuve ou sous vide. On obtient ainsi une poudre.After the last separation, a paste containing 20 to 95% of water is obtained, which is removed by drying, according to any suitable process such as drying in an oven or under vacuum. A powder is thus obtained.

Dans le cas où le chauffage s'effectue par apport de chaleur, il est important d'effectuer celui-ci aussi rapidement que possible, afin de limiter la croissance des grains d'oxyde d'argent.In the case where the heating is carried out by adding heat, it is important to carry out this as quickly as possible, in order to limit the growth of the silver oxide grains.

Dans la poudre obtenue, il faut alors convertir l'oxyde d'argent en argent métal. Cette opération est effectuée par traitement thermique réducteur de l'oxyde d'argent, à une température de l'ordre de 200 à 500°C. Cette étape permet également une agglomération de la poudre, ce qui la rend avantageusement distribuable dans une machine automatique.In the powder obtained, it is then necessary to convert the silver oxide into silver metal. This operation is carried out by reducing heat treatment of the silver oxide, at a temperature of the order of 200 to 500 ° C. This step also allows agglomeration of the powder, which advantageously makes it distributable in an automatic machine.

De façon préférée, les quantités de nitrate d'argent et d'oxyde d'étain dans la solution de départ sont telles que, dans le matériau final, on trouve environ de 84 à 92% en poids d'argent, le complément étant de l'oxyde d'étain.Preferably, the amounts of silver nitrate and tin oxide in the starting solution are such that, in the final material, there are approximately 84 to 92% by weight of silver, the balance being tin oxide.

On va maintenant décrire deux procédés préférés pour la fabrication de pastilles ou de barreaux de contact incorporant le matériau de contact dont l'obtention a été décrite ci-dessus.We will now describe two preferred methods for the manufacture of pads or contact bars incorporating the contact material, the production of which has been described above.

Une pastille de contact est constituée conventionnellement d'une sous-couche d'argent pur, d'une épaisseur de l'ordre de quelques centaines de µm, qui permet de braser la pastille sur son support, et d'une couche de matériau de contact, par exemple de 1 à 3 mm d'épaisseur.A contact pad is conventionally made up of a sub-layer of pure silver, with a thickness of the order of a few hundred μm, which makes it possible to braze the pad on its support, and of a layer of material. contact, for example from 1 to 3 mm thick.

L'assemblage de deux composants de ce type est réalisé conventionnellement par compression, frittage et calibrage, ce qui donne de bonnes qualités d'adhérence.The assembly of two components of this type is conventionally carried out by compression, sintering and calibration, which gives good qualities of adhesion.

Cependant, il s'est avéré qu'un tel processus connu n'était pas bien adapté au nouveau matériau de contact conforme à l'invention; il est apparu en effet que les deux parties du comprimé ont chacune un comportement bien différent lors du frittage : la sous-couche d'argent se fritte jusqu'à la densité théorique avec une faible diminution de volume, tandis que la couche de AgSnO₂ se fritte avec une importante réduction de volume sans toutefois atteindre la densité théorique. Il en résulte qu'après frittage, les pastilles présentent une forme de dôme marquée.However, it turned out that such a known process was not well suited to the new contact material according to the invention; it appeared in fact that the two parts of the tablet each have a very different behavior during sintering: the silver undercoat sintered to the theoretical density with a slight reduction in volume, while the layer of AgSnO₂ sintered with a significant reduction in volume without however reaching the theoretical density. As a result, after sintering, the pellets have a marked dome shape.

En outre, du fait de la fragilité de la partie de contact en AgSnO₂ de la pastille, une déformation trop importante au cours du processus de frittage conduit à une fissuration de la pastille lorsqu'on la soumet à une nouvelle compression pour la rendre plane (calibrage).In addition, due to the fragility of the AgSnO₂ contact part of the pellet, too much deformation during the sintering process leads to a cracking of the pellet when it is subjected to a new compression to make it flat (calibration).

Conformément à un aspect de la présente invention, on prévoit pour fabriquer les pastilles une suite d'étapes permettant d'amener lesdites pastilles à leur densité maximale de façon progressive. Plus précisément, on utilise selon l'invention la succession d'étapes suivantes :
- compression à environ 3t/cm²;
- frittage pendant 30 à 40 mn à une température de l'ordre de 840°C;
- premier calibrage à environ 10 t/cm²;
- premier recuit pendant environ 30 mn à environ 900°C;
- second calibrage à environ 12 t/cm²; et
- second recuit pendant environ 30 mn à environ 940°C.According to one aspect of the present invention, provision is made for manufacturing the pellets a series of steps making it possible to bring said pellets to their maximum density gradually. More precisely, the following succession of steps is used according to the invention:
- compression at around 3t / cm²;
- sintering for 30 to 40 min at a temperature of the order of 840 ° C;
- first calibration at around 10 t / cm²;
- first annealing for approximately 30 minutes at approximately 900 ° C;
- second calibration at around 12 t / cm²; and
- second annealing for approximately 30 minutes at approximately 940 ° C.

Ce procédé est avantageux en ce que les gains en densité sont obtenus essentiellement lors des opérations de compression et de calibrage. Cela signifie que le frittage à haute température du matériau est très lent, et que peu de liaisons se forment entre les grains d'argent. La fragilité de la pastille obtenue est certes augmentée, mais reste assez faible pour que le comportement électrique soit meilleur qu'avec un matériau de contact de type argent-oxyde de cadmium.This process is advantageous in that the density gains are obtained essentially during the compression and calibration operations. This means that the high temperature sintering of the material is very slow, and that few bonds form between the silver grains. The brittleness of the pellet obtained is certainly increased, but remains low enough for the electrical behavior to be better than with a contact material of the silver-cadmium oxide type.

On va décrire ci-dessous, selon un autre aspect essentiel de l'invention, un second procédé de fabrication de pastilles comportant le nouveau matériau de contact décrit plus haut.We will describe below, according to another essential aspect of the invention, a second method of manufacturing pellets comprising the new contact material described above.

Il est à noter que ce procédé de fabrication, contrairement au premier (dans lequel le produit final n'est pas laminable), va permettre de réaliser des contacts sous forme de barreaux. Il permet également de diminuer le nombre d'étapes nécessaires pour la fabrication.It should be noted that this manufacturing process, unlike the first (in which the final product is not laminable), will make it possible to make contacts in the form of bars. It also makes it possible to reduce the number of steps necessary for manufacturing.

On fait appel selon l'invention à une technique de frittage en phase liquide, qui permet d'augmenter considérablement les vitesses de frittage et la qualité du fritté obtenu.A liquid sintering technique is used according to the invention, which makes it possible to considerably increase the sintering speeds and the quality of the sintered product obtained.

Plus précisément, on fait en sorte de créer une phase liquide très minoritaire dans le matériau Ag-SnO₂ à fritter. Les grains baignent alors dans un liquide qui autorise des évolutions beaucoup plus rapides, tour en assurant que la forme de la pièce soit conservée.More precisely, we make sure to create a very minor liquid phase in the Ag-SnO₂ material to be sintered. The grains are then immersed in a liquid which allows much faster development, ensuring that the shape of the part is preserved.

De façon concrète, la formation d'une phase liquide est obtenue en ajoutant au composite, avant frittage, de l'oxyde de cuivre CuO. Il n'a pas été possible de déterminer si le liquide formé était un mélange Ag-O ou Ag-Cu-O, mais on a néanmoins vérifié que la phase liquide se formait alors sous air à environ 940°C, soit 20°C en-dessous de la température de fusion de l'argent.Concretely, the formation of a liquid phase is obtained by adding to the composite, before sintering, copper oxide CuO. It was not possible to determine whether the liquid formed was an Ag-O or Ag-Cu-O mixture, but it was nevertheless verified that the liquid phase then formed in air at around 940 ° C, or 20 ° C below the silver melting temperature.

De façon préférée, l'oxyde de cuivre est ajouté en une proportion comprise entre 0,1 et 1,0% en poids, par exemple de l'ordre de 0,2%. On observe alors un frittage remarquable des pastilles en les portant à une température comprise entre la température de formation du liquide, soit 940°C, et la température de fusion de l'argent, soit 960°C. On peut choisir par exemple une température de l'ordre de 940 à 950°C. En quelques minutes, la densité réelle du mélange Ag-SnO₂ devient pratiquement égale à sa densité théorique. De plus, malgré la taille de grains initiale relativement fine, on obtient un matériau très malléable, qui permet de simplifier sensiblement les opérations ultérieures, comme par exemple le calibrage des pastilles individuelles ou le laminage de barreaux.Preferably, the copper oxide is added in a proportion of between 0.1 and 1.0% by weight, for example of the order of 0.2%. A remarkable sintering of the pellets is then observed by bringing them to a temperature between the temperature of formation of the liquid, ie 940 ° C., and the melting temperature of the silver, ie 960 ° C. One can choose for example a temperature of the order of 940 to 950 ° C. In a few minutes, the actual density of the Ag-SnO₂ mixture becomes practically equal to its theoretical density. In addition, despite the relatively fine initial grain size, a very malleable material is obtained, which makes it possible to considerably simplify the subsequent operations, such as for example the calibration of the individual pellets or the lamination of bars.

Selon une autre caractéristique préférée, on ajoute l'oxyde de cuivre dans la proportion voulue au cours de la précipitation décrite plus haut en relation avec le procédé d'obtention du matériau de contact. A cet effet, la quantité nécessaire de cuivre est ajoutée sous forme de nitrate de cuivre Cu(NO₃)₂ qui est mis en solution en même temps que le nitrate d'argent. De façon analogue à ce qui se passe pour l'argent, il se forme lors de la réaction avec la soude de l'hydroxyde de cuivre Cu(OH)₂, qui se transformera en CuO lors des traitements thermiques de la poudre.According to another preferred characteristic, the copper oxide is added in the desired proportion during the precipitation described above in connection with the process for obtaining the contact material. To this end, the necessary quantity of copper is added in the form of copper nitrate Cu (NO₃) ₂ which is dissolved together with the silver nitrate. Analogously to what happens to silver, it is formed during the reaction with sodium hydroxide copper hydroxide Cu (OH) ₂, which will transform into CuO during heat treatments of the powder.

On obtient ainsi une dispersion optimale du CuO dans le mélange, avec en conséquence une répartition régulière du liquide formé dans celui-ci et un effet homogène de liaison des grains lors du frittage.An optimal dispersion of the CuO in the mixture is thus obtained, with consequently a regular distribution of the liquid formed therein and a homogeneous grain bonding effect during sintering.

Il est à noter ici que l'oxyde de cuivre est ajouté en une quantité suffisante pour que le frittage ait lieu en phase liquide, mais que cette quantité est si faible que l'oxyde de cuivre n'a que peu d'influence sur le comportement électrique de la pastille ou du barreau obtenu.It should be noted here that the copper oxide is added in an amount sufficient for the sintering to take place in the liquid phase, but that this amount is so small that the copper oxide has little influence on the electrical behavior of the pellet or bar obtained.

Avec l'amélioration décrite ci-dessus du procédé de fabrication des pastilles, une suite d'étapes avantageuse peut être la suivante :
- compression à 3 t/cm²,
- frittage en phase liquide à 940°C,
- calibrage à 12 t/cm².With the improvement described above of the process for manufacturing the pellets, a series of advantageous steps can be as follows:
- compression at 3 t / cm²,
- liquid phase sintering at 940 ° C,
- calibration at 12 t / cm².

Si nécessaire, on pourra y ajouter une étape finale de recuit de libération des contraintes de calibrage.If necessary, we can add a final annealing step to release the calibration constraints.

Pour la fabrication de pastilles à partir de barreaux, on peut utiliser la succession d'étapes suivante :
- compression à environ 2 à 3 t/cm²,
- frittage en phase liquide à 940°C,
- succession de laminages-recuits pour obtenir la section souhaitée,
- découpe des pastilles.For the production of pellets from bars, the following sequence of steps can be used:
- compression at around 2 to 3 t / cm²,
- liquid phase sintering at 940 ° C,
- succession of rolling-annealing to obtain the desired section,
- cutting of the pellets.

On a indiqué dans le tableau I ci-après les performances comparées de deux pastilles de contact obtenues conformément aux deux procédés de fabrication décrits ci-­dessus (échantillons 1 et 2) avec deux pastilles de contact réalisées avec des matériaux de contact de l'art antérieur, à savoir un matériau argent-oxyde de cadmium à 12% et un matériau argent-oxyde d'étain-oxyde de tungstène du commerce (échantillons A et B).The comparative performances of two contact pads obtained in accordance with the two manufacturing methods described above (samples 1 and 2) with two contact pads made with contact materials of the art have been indicated in table I below. prior art, namely a 12% silver-cadmium oxide material and a commercial silver-tin oxide-tungsten oxide material (samples A and B).

Les pastilles présentaient toutes les mêmes dimensions.The pellets all had the same dimensions.

Dans un premier essai (Essai 100A), l'ouverture du contact a été effectuée sousun courant de 100 A efficaces et la fermeture sous un courant de 600 A efficaces, avec un rebond prédéterminé identique pour tous les échantillons.In a first test (Test 100A), the opening of the contact was carried out under a current of 100 A effective and the closing under a current of 600 A effective, with a predetermined rebound identical for all the samples.

Après chaque fermeture, on a mesuré la force nécessaire pour ouvrir les contacts (force de soudure dynamique), la résistance de contact et trois fois en cours d'essai, on a déterminé l'érosion des contacts, déterminée en termes de perte de poids à chaque fermeture/ouverture, par pesée.After each closing, the force necessary to open the contacts was measured (welding force dynamic), the contact resistance and three times during the test, the contact erosion was determined, determined in terms of weight loss at each closing / opening, by weighing.

Dans l'essai 1000 A, la fermeture des contacts a été effectuée sous 1000 A efficaces, et l'ouverture sous courant nul. Les mêmes mesures ont été effectuées.In the 1000 A test, the contacts were closed under 1000 A effective, and the opening under zero current. The same measurements were made.

On constate que, pour chaque type de mesure, les pas­tilles réalisées conformément à l'invention sont supérieures à au moins l'une des pastilles de l'art antérieur, cette supé­riorité étant la plus marquée pour l'essai 1000 A.It is noted that, for each type of measurement, the pellets produced in accordance with the invention are greater than at least one of the pellets of the prior art, this superiority being most marked for the 1000 A test.

Bien entendu, la présente invention n'est nullement limitée à la description ci-dessus, et l'homme de l'art saura y apporter toute variante ou modification conforme à son esprit. TABLEAU I Echantillon Matière (% en poids) Essai 100 A Essai 1000 A Taux * d'érosion Forces de soudure à 99,99% N Taux * d'érosion Forces de soudure à 95% N Rèsistance de contact mohms 1 Ag-SnO₂ 12% 12 6 32 0,38 2 Ag-SnO₂ 12% - CuO 0,2% 11 12 9 25 0,34 A Ag-CdO 12% 26 12 62 67 0,13 B Ag-SnO₂ - WO₃ disponible commercialement 10 10 172 26 0,43 * taux d'érosion en µg par opération fermeture/ouverture pour un couple de contacts. Of course, the present invention is in no way limited to the above description, and those skilled in the art will be able to make any variant or modification in accordance with its spirit. TABLE I Sample Material (% by weight) 100 A test 1000 A test Erosion rate * Welding forces at 99.99% N Erosion rate * Welding forces at 95% N Mohms contact resistance 1 Ag-SnO₂ 12% 12 6 32 0.38 2 Ag-SnO₂ 12% - CuO 0.2% 11 12 9 25 0.34 AT Ag-CdO 12% 26 12 62 67 0.13 B Ag-SnO₂ - WO₃ commercially available 10 10 172 26 0.43 * erosion rate in µg per closing / opening operation for a couple of contacts.

Claims (11)

1. Procédé de préparation d'un matériau de contact constitué par de l'argent et de l'oxyde d'étain, caractérisé en ce qu'il comprend les étapes consistant à :
- préparer une solution aqueuse contenant du nitrate d'argent dissout et des particules d'oxyde d'étain en suspension, la taille desdites particules, mesurée en termes de surface spécifique selon la méthode BET, étant comprise entre environ 2 et 6 m²/g,
- faire précipiter le nitrate d'argent en hydroxyde d'argent par addition rapide d'une base forte et brassage, l'hydroxyde d'argent, instable, se transformant progressivement en oxyde d'argent,
- éliminer les ions en solution, puis l'eau, pour obtenir un produit sec,
- chauffer le produit sec à une température d'environ 200 à 500°C pour réduire l'oxyde d'argent en argent métal.1. A method of preparing a contact material consisting of silver and tin oxide, characterized in that it comprises the steps consisting in:
- Prepare an aqueous solution containing dissolved silver nitrate and suspended tin oxide particles, the size of said particles, measured in terms of specific surface area according to the BET method, being between approximately 2 and 6 m² / g ,
- precipitate the silver nitrate into silver hydroxide by rapid addition of a strong base and mixing, the silver hydroxide, unstable, gradually transforming into silver oxide,
- remove the ions in solution, then the water, to obtain a dry product,
- heat the dry product to a temperature of around 200 to 500 ° C to reduce the silver oxide to silver metal. 2. Procédé selon la revendication 1, caractérisé en ce que, dans le matériau de contact final, l'argent est présent en une proportion de l'ordre de 84 à 92% en poids, le reste étant de l'oxyde d'étain.2. Method according to claim 1, characterized in that, in the final contact material, the silver is present in a proportion of the order of 84 to 92% by weight, the remainder being tin oxide . 3. Procédé selon l'une des revendications 1 et 2, caractérisé en ce que la base forte est de la soude concentrée.3. Method according to one of claims 1 and 2, characterized in that the strong base is concentrated soda. 4. Procédé selon l'une des revendications 1 à 3, caractérisé en ce que l'étape de chauffage du produit sec est effectuée à une température et une durée telles qu'elle conduit à une agglomération de l'argent et de l'oxyde d'étain.4. Method according to one of claims 1 to 3, characterized in that the step of heating the dry product is carried out at a temperature and a duration such that it leads to an agglomeration of silver and oxide of tin. 5. Procédé de fabrication d'un élément de contact tel qu'une pastille incorporant le matériau préparé par le procédé selon l'une des revendications 1 à 4, ainsi qu'une sous-couche mince d'argent pur, caractérisé en ce qu'on soumet le matériau et la sous-couche aux opérations suivantes :
- compression à environ 3t/cm²;
frittage pendant 30 à 40 mn à une température de l'ordre de 840°C;
- premier calibrage à environ 10 t/cm²;
- premier recuit pendant environ 30 mn à environ 900°C;
- second calibrage à environ 12 t/cm²; et
- second recuit pendant environ 30 mn à environ 940°C.5. A method of manufacturing a contact element such as a wafer incorporating the material prepared by the method according to one of claims 1 to 4, as well as a thin underlay of pure silver, characterized in that '' the material and the undercoat are subjected to the following operations:
- compression at around 3t / cm²;
sintering for 30 to 40 min at a temperature of the order of 840 ° C;
- first calibration at around 10 t / cm²;
- first annealing for approximately 30 minutes at approximately 900 ° C;
- second calibration at around 12 t / cm²; and
- second annealing for approximately 30 minutes at approximately 940 ° C. 6. Procédé de fabrication d'un élément de contact tel qu'une pastille ou un barreau incorporant le matériau préparé par le procédé selon l'une des revendications 1 à 4 ainsi qu'une sous-couche mince d'argent pur, caractérisé en ce qu il comprend les étapes consistant à :
- ajouter au matériau préparé une faible proportion d'oxyde de cuivre,
- comprimer le matériau obtenu avec ladite sous-­couche pour mettre en forme ledit élément, et chauffer ledit élément à une température comprise entre 940 et 960°C, pour conduire à la formation d'une phase liquide minoritaire dans laquelle l'élément est fritté.6. A method of manufacturing a contact element such as a wafer or a bar incorporating the material prepared by the method according to one of claims 1 to 4 as well as a thin underlay of pure silver, characterized in what it includes the steps of:
- add a small proportion of copper oxide to the prepared material,
- compress the material obtained with said undercoat to shape said element, and heat said element to a temperature between 940 and 960 ° C, to lead to the formation of a minority liquid phase in which the element is sintered . 7. Procédé selon la revendication 6, caractérisé en ce que l'oxyde de cuivre est ajouté au matériau préparé par addition de nitrate de cuivre dans la solution aqueuse, qui, lors de l'étape de précipitation, précipite en hydroxyde de cuivre, lequel est ensuite transformé en oxyde de cuivre.7. Method according to claim 6, characterized in that the copper oxide is added to the material prepared by addition of copper nitrate in the aqueous solution, which, during the precipitation step, precipitates into copper hydroxide, which is then transformed into copper oxide. 8. Procédé selon l'une des revendications 6 et 7, caractérisé en ce que l'oxyde de cuivre est présent dans le matériau préparé en une proportion de l'ordre de 0,1 à 1,0% en poids.8. Method according to one of claims 6 and 7, characterized in that the copper oxide is present in the prepared material in a proportion of the order of 0.1 to 1.0% by weight. 9. Procédé selon l'une des revendications 5 à 8, pour la fabrication de pastilles, caractérisé en ce qu'il comprend une étape ultérieure de calibrage par compression.9. Method according to one of claims 5 to 8, for the manufacture of pellets, characterized in that it comprises a subsequent step of calibration by compression. 10. Procédé selon la revendication 9, caractérisé en ce qu'il comprend une étape finale de recuit de libération des contraintes.10. Method according to claim 9, characterized in that it comprises a final annealing step of stress release. 11. Procédé selon l'une des revendications 5 à 8, pour la fabrication de barreaux à partir desquels des pastilles peuvent être découpées, caractérisé en ce qu'il comprend en outre au moins une succession d'étapes de laminage et de recuit.11. Method according to one of claims 5 to 8, for the manufacture of bars from which the pellets can be cut, characterized in that further comprises at least one succession of rolling and annealing steps.
EP89403211A 1988-11-22 1989-11-21 Method for the preparation of electrical contact material, and method of making a contact element incorporating such a material Expired - Lifetime EP0370897B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8815163 1988-11-22
FR8815163A FR2639466B1 (en) 1988-11-22 1988-11-22 PROCESS FOR PREPARING AN ELECTRICAL CONTACT MATERIAL AND METHOD FOR MANUFACTURING A CONTACT ELEMENT INCORPORATING SUCH A MATERIAL

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EP0370897A1 true EP0370897A1 (en) 1990-05-30
EP0370897B1 EP0370897B1 (en) 1993-02-03

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EP (1) EP0370897B1 (en)
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MX (1) MX170782B (en)

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WO2007112926A2 (en) * 2006-03-31 2007-10-11 Umicore S.A. Process for manufacture of silver-based particles and electrical contact materials
FR2916082A1 (en) * 2007-05-11 2008-11-14 Schneider Electric Ind Sas Preparing material for forming electrical contact pellet, comprises synthesizing powder, deagglomerating reinforcement particles, mixing the powder in silver nitrate solution, obtaining powder containing silver oxide particles and reducing
US7566437B2 (en) 2006-03-31 2009-07-28 Umicore Ag & Co. Kg Process for manufacture of silver-based composite powders for electrical contact materials and composite powders so produced
CN101649399B (en) * 2009-07-20 2010-12-29 温州宏丰电工合金股份有限公司 Preparation method of tin-oxygen-silver electric contact material
CN104475733A (en) * 2014-12-30 2015-04-01 桂林电器科学研究院有限公司 Preparation method of flake-like silver-nickel-tungsten electrical contact material

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EP0435655B1 (en) * 1989-12-26 1998-02-25 Sumitomo Metal Mining Company Limited Silver-metal oxide composite material and process for producing the same
US5286441A (en) * 1989-12-26 1994-02-15 Akira Shibata Silver-metal oxide composite material and process for producing the same
DE4142374A1 (en) * 1991-12-20 1993-06-24 Siemens Ag METHOD FOR PRELIMINATING CONTACT PIECES FOR ELECTRICAL SWITCHING DEVICES
TW272294B (en) * 1993-03-29 1996-03-11 Takahashi Yasunori
FR2793947B1 (en) * 1999-05-20 2002-03-15 Thermocompact Sa HIGH SENSITIVITY RELAY, AND METHOD FOR THE PRODUCTION THEREOF
US20050199094A1 (en) * 2003-09-09 2005-09-15 Noble Fiber Technologies, Inc. Method of producing metal-containing particles
US20100167051A1 (en) * 2006-03-31 2010-07-01 Goia Dan V Process for Manufacture of Silver-Based Particles and Electrical Contact Materials
CN103014395B (en) * 2012-12-09 2014-12-24 温州聚星电接触科技有限公司 Method for preparing efficient aerated mixed powder
CN104117684B (en) * 2014-08-11 2016-06-22 郴州市金贵银业股份有限公司 A kind of preparation method of tin-oxygen-silver electric contact material
CN104498914B (en) * 2014-12-22 2017-03-29 东北大学 A kind of method that sol-gel technique prepares siller tin oxide electric contact material
CN104493177A (en) * 2014-12-30 2015-04-08 桂林电器科学研究院有限公司 Preparation method of flakey silver and tungsten electrical contact material
CN104493173A (en) * 2014-12-30 2015-04-08 桂林电器科学研究院有限公司 Preparation method of flakey or rivet-shaped silver and tungsten electrical contact material
CN104493176A (en) * 2014-12-30 2015-04-08 桂林电器科学研究院有限公司 Method for preparing flaky silver-tungsten electrical contact material
CN104889416B (en) * 2015-05-04 2017-01-04 浙江大学 A kind of preparation method of silver tin ash intermediate composite granule
CN107502774B (en) * 2017-09-25 2019-05-17 深圳市英诺泰克科技有限公司 A kind of preparation method of silver tin oxide material

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WO2007112926A2 (en) * 2006-03-31 2007-10-11 Umicore S.A. Process for manufacture of silver-based particles and electrical contact materials
WO2007112926A3 (en) * 2006-03-31 2007-12-21 Umicore Ag & Co Kg Process for manufacture of silver-based particles and electrical contact materials
US7566437B2 (en) 2006-03-31 2009-07-28 Umicore Ag & Co. Kg Process for manufacture of silver-based composite powders for electrical contact materials and composite powders so produced
US7842274B2 (en) 2006-03-31 2010-11-30 Umicore, S.A. Process for manufacture of silver-based particles and electrical contact materials
FR2916082A1 (en) * 2007-05-11 2008-11-14 Schneider Electric Ind Sas Preparing material for forming electrical contact pellet, comprises synthesizing powder, deagglomerating reinforcement particles, mixing the powder in silver nitrate solution, obtaining powder containing silver oxide particles and reducing
CN101649399B (en) * 2009-07-20 2010-12-29 温州宏丰电工合金股份有限公司 Preparation method of tin-oxygen-silver electric contact material
CN104475733A (en) * 2014-12-30 2015-04-01 桂林电器科学研究院有限公司 Preparation method of flake-like silver-nickel-tungsten electrical contact material

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DE68904742D1 (en) 1993-03-18
DE68904742T2 (en) 1993-05-19
JP2877860B2 (en) 1999-04-05
JPH02225637A (en) 1990-09-07
US4971754A (en) 1990-11-20
FR2639466A1 (en) 1990-05-25
EP0370897B1 (en) 1993-02-03
MX170782B (en) 1993-09-14
FR2639466B1 (en) 1991-02-15

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