DE19608490C1 - Contact material made of silver and active components, molded part made therefrom and process for producing the molded part - Google Patents

Abstract

Contact materials with an oxide active component have the disadvantage of a shorter shelf life, principally in comparison with contact materials with a metal active component for which allowance has to be made for a higher tendency to fuse. The invention proposes a silver contact material which includes as active components a metal and an oxide of the metal, the sum of the material proportions of the metal and the oxide being between 1 % and 50 %. The invention also proposes a process for producing a moulded piece from the contact material. Said contact material generally has more favourable switching properties than a contact material with metal or metal-oxide active components and is therefore particularly suitable for a power switch in power engineering.

Description

The invention relates to a contact material made of silver and Active components. The invention further relates to a one Contact material existing fitting and a process to produce such a fitting.

For a contact piece in a low-voltage switchgear Energy technology, e.g. B. in a circuit breaker or in a Contactor, have contact materials made of silver that themselves in certain active components to improve Switching characteristics have been different for a long time proven. Both metals and Me are active components talloxide known. Representative of the metallic contact mechanism Silver materials are, for example, silver-nickel materials fe (AgNi) and silver-iron materials (AgFe). As representative of the oxidic contact materials is a silver Iron oxide material (AgFe₂O₃) called.

From US 5,198,015 is a contact material on silver basis, which has a mass fraction of 0.5-39.9% Nickel and a mass fraction of 0.14-7% nickel oxide points.

Silver-nickel contact materials in particular have good ones Switching properties, but it is disadvantageous that the during manufacture or during operation due to abrasion Ending nickel dust as well as the switching product Nickel oxide harmful effects on human org can have nism.

Standardized test methods for determining the switching properties Properties of a contact material can be found in INT. J. Pow  Metallurgy and Powder Technology, Vol. 12 (1976), 219-228.

Contact materials that contain active components in addition to silver which have no harmful effect on human Have organism are z. B. a silver-iron-rhenium contact material from EP 0 586 411 B1 and the already mentioned Silver-iron oxide contact material from DE 41 17 311 A1. The switching properties of the contact materials mentioned read each by adding additional active components ten, e.g. B. zirconium oxide (ZrO₂), yttrium oxide (Y₂O₃) and iron wool framat (FeWo₄), improve. The mass fraction of such additional active components are usually between 0.01% and 5%.

Oxidic contact materials, d. H. Contact materials with me active components, are characterized by a ge rings tendency to weld and meet the requirements Life out. Metallic contact materials have one very long life, especially with small currents, zei However, they tend to have a higher tendency to weld than that oxidic contact materials.

The object of the invention is a nickel-free contact mechanism Specify silver fabric with active components, which ge less than a metallic contact material Tendency to sweat and to an oxidic contact mechanism fabric has a longer lifespan and thus overall has better switching properties. Object of the invention it is also a manufacturing process for a molding from such a contact material and a shaped piece the contact material, in particular a contact piece ben, which is characterized by the improved switching properties especially for a circuit breaker in energy technology net.  

This problem is solved with regard to the contact material through a contact material made of silver with another Metal and an oxide of the other metal as active components ten, the sum of the mass fractions of the metal and the Oxide is between 1% and 50% and the metal is iron and the metal oxide is iron oxide.

The invention is based on the idea that a contact material, which as active components is both a metal and also contains an oxide of this metal, the inexpensive switching element properties of a contact material with a metallic effect components with the favorable switching properties of a con cycle material with active metal oxide components nigt. Extensive studies show that such a Contact material is characterized by a very low welding egg excellence with a long service life. Skull effects of iron or iron oxide on human beings Chen organism are also not known.

The iron oxide can be either Fe₂O₃ or Fe₃O₄ gene, advantageously it is a mixture of Fe₂O₃ and Fe₃O₄, as ver in the trade easily and inexpensively is available.

An improvement in the switching properties of the contact mechanism substance is reached if it has at least one more Has active component or minor component. Especially before it is partial if the minimum component is a transitional measure tall or an oxide containing the transition metal is where at the mass fraction of the minimum component between 0.01% and 5%, preferably between 0.01% and 2%. The switching lower compo, which has a particularly favorable effect on properties nents are e.g. B. zirconium oxide (ZrO₂), yttrium oxide (Y₂O₃), Rheni Umoxid (ReO₂), rhenium (Re), iron tungstate (FeWO₄) and Wis Mutz Zirconate (2Bi₂O₃ × 3ZrO₂). These are minor components also in combination favorable for the switching properties of the Contact material.  

To solve the problem related to a fitting, it becomes according to the invention, a fitting made of a contact material which includes silver, iron and iron oxide, the Sum of the mass fractions of iron and iron oxide between between 1% and 50%. The fitting is advantageous fortunately produced by powder metallurgy. The powder Tallurgical manufacturing process is still below ago explained.

For use in a power engineering switchgear, especially for a circuit breaker, is the fitting advantageously in the form of a contact piece. The contact piece can also be made with a layer Pure silver for the safe connection of the contact piece with the Pad should be provided by brazing.

Regarding the process for producing a molding the object is achieved in that a Powder mixture made of silver, iron and iron oxide det and powder metallurgically processed to the molding becomes.

For the production of a molded part from a contact material are essentially two different powder metallurgical Process known. In the compression molding technique, the pulvermi pressing by compression molding into a molding which by sintering and possibly further pressing to the finished shape piece is processed. As mentioned earlier, for the Production of a fitting in the form of a contact piece Shaped with an additional layer of pure silver for si cheren connection of the contact piece with the pad Brazing to be pressed. In one using the compression molding technique manufactured molding are the powdered added Active components with uniform grain size evenly without Macroscopic orientation distributed over the silver matrix before, and the structure of the fitting is largely isotropic.  

In the extrusion technique, the powder mixture is initially too a porous compact or slug pressed and / or gesin tert. The compact or slug is, if necessary, with a layer made of pure silver, extruded into one strand, from which the fittings are separated and possibly one subsequent treatment.

In a fitting manufactured using the extrusion technique are the powder grains of the active components and possibly the Sil bers deformed or aligned in the direction of extrusion, where form an anisotropic, namely line structure det.

Due to the structure of a contact material, d. H. through the Size and by the distribution of the active components in the Silver matrix, its electrical switching properties, e.g. B. erosion, contact resistance and tendency to weld, measured probably determined.

Metal powders are usually down to a medium Grain size of about 5 microns commercially available. Because metal oxide powders are available whose average grain size is essential is less than 1 µm, can be achieved by using Metal oxide powder instead of metal powder and subsequent re production of the metal oxide to achieve a contact material which is the average grain size of the metallic active components is in the nanometer range. Such a contact material with a fine structure has more favorable switching properties on as a contact material with a coarse structure. It can also when using metal oxide powders under less strict transport and processing regulations worked because, unlike metal oxide powders, there are many metals powder are self-igniting. This way reduce manufacturing costs.

The switching properties of a fitting are correspondingly made of the contact material improved by a cost-effective  manufacturing process in which a first powder mix formed from silver and iron oxide and in which he most powder mixture that reduces iron oxide to iron, from the first pulvermi changed by this reduction and a second powder mixture formed from iron oxide is and the second powder mixture powder metallurgically to the Fitting is processed.

An undesirable oxidation or reduction of the metal oxide to prevent in further procedural steps, it is from Advantage if the sintering process of the manufacturing process takes place under inert gas or vacuum.

The following is an embodiment of the invention hand of a figure and by examining results explained. It shows:

Fig. 1 The structure of a silver-iron-iron oxide Kon contact material produced according to the invention by the extrusion technology parallel to the extrusion direction.

A silver-iron-iron oxide plant is used as an exemplary embodiment fabric made. This is done with a powder mixture of silver (Ag) and the active components iron (Fe) and iron oxide (Fe₂O₃) as well as the other active components zirconium oxide (ZrO₂), Yttri Umoxid (Y₂O₃), rhenium oxide (ReO) and rhenium (Re) herge poses. The composition of the powder mixture is such that the sum of the mass fractions of the active components is iron (Fe) and iron oxide (Fe₂O₃) in the finished material 10% be carries, the mass fractions of iron (Fe) and iron oxides (Fe₂O₃) each amount to 5%. The sum of the masses parts of the other active components is 2%.

The powder mixture becomes a blank or slug processed and un according to the extrusion technique described ter is pressed into a shaped part under the usual conditions. All Sintering processes take place under inert gas in order to achieve a re  reduction of the iron oxide to iron or an oxidation of the egg prevent sens to iron oxide.

The contact material produced in this way is due to its Composition referred to as AgFe5F₂O₃5 material.

In Fig. 1 the structure of the AgFe5F₂O₃5 material according to the invention is shown in a micrograph parallel to the extrusion direction. The switching properties of the contact material are examined in comparative tests with known metallic or metal oxide contact materials.

This is done as a representative of the metallic contact materials an Ag (FeRe95 / 5) 8.8 contact material was used. The Spelling Ag (FeRe95 / 5) 8.8 draws a silver egg sen-rhenium contact material, the sum of the masses proportions of the active components iron (Fe) and rhenium (Re) 8.8% and the ratio of the mass fractions of iron (Fe) for rhenium (Re) 95 to 5 is selected. As a representative for a metal oxide contact material is a AgFe₂O₃5.4ZrO₂1 contact material used. Of the AgFe₂O₃5.4ZrO₂1 contact material is characterized by a Mass fraction of 5.4% iron oxide (Fe₂O₃) and 1% zirconium oxide (ZrO₂) off.

The test methods used in the comparative experiments are already described in the appraisal of the prior art. The AgFe5F₂O₃5 contact material according to the invention shows one less tendency to weld than the metallic one Ag (FeRe95 / 5) 8.8 contact material and a longer service life as the metal oxide AgFe₂O₃5.4ZrO₂1 contact material.

Due to the favorable switching properties, a such contact material in particular for use in circuit breakers in energy technology.

Claims (11)

1. Contact material made of silver with another metal and an oxide of the other metal as active components, the sum of the mass fractions of the metal and the oxide between 1% and 50%, characterized in that the white metal and iron oxide and the oxide iron oxide is. 2. contact material according to claim 1, characterized in that the iron is oxide Fe₂O₃ and / or Fe₃O₄. 3. Contact material according to one of the preceding claims with at least one other active component. 4. contact material according to claim 3, characterized in that the white tere active component is a transition metal or an over is transition metal containing oxide, the mass fraction of further active component is between 0.01% and 5% is preferably between 0.01% and 2%. 5. Contact material according to claim 4, characterized in that as further Active component zirconium oxide (ZrO₂), yttrium oxide (YO₂), rhenium oxide (ReO₂), rhenium (Re), iron tungstate (FeWO₄) and / or Bismuth zirconate (2Bi₂O₃ × 3ZrO₂) is provided. 6. fitting made of a contact material, which is silver, egg sen and iron oxide, the sum of the mass fractions of the metal and the oxide is between 1% and 50%. 7. fitting according to claim 6, which is made by powder metallurgy.   8. fitting according to claim 6 or 7, which as a contact piece for a switchgear of the energy technology nik, especially for a low-voltage switch forms is. 9. A method for producing a fitting from a con clock material, in which a powder mixture of silver Iron and formed from iron oxide and powder metallurgy too the fitting is processed. 10. A method for producing a fitting from a con clock material, in which a first powder mixture of silver and formed from iron oxide and in the first powder mixture the iron oxide is reduced to iron from which by this Reduction modified first powder mixture and from iron oxide a second powder mixture is formed and the second powder Mixing processed by powder metallurgy to the molding becomes. 11. The method according to claim 9 or 10, characterized in that the Verar processing of the powder mixture, sintering under inert gas or Vacuum includes.