EP1023959A2 - Composite article prepared by powder metallurgy and process for its manufacture - Google Patents

Abstract

The invention relates to a powder-metallurgically produced composite material comprising a matrix made of a metal with a melting point of at most 1200 ° C and a granular additive embedded in this matrix and comprising at least two refractory components, characterized in that the refractory components are in the form of mixed crystals or intermetallic phases . In one embodiment, a or a first group of refractory components has a melting point of 1,500 to 2,400 ° C. and a second or a second group of refractory components have a melting point of more than 2,400 ° C. The composite material is produced by mixing a powdery mixture converts the refractory components into a mixed crystal or an intermetallic phase by heating and combines the powder obtained from this by cooling and crushing by powder metallurgy with a metal matrix with a melting point of at most 1200 ° C. The composite material of the invention is suitable as a switch contact for vacuum interrupters.

Description

The invention relates to powder-metallurgically produced composite materials, comprising a matrix in which a granular additive is embedded, which consists of at least two refractory components, which as mixed crystals or there are intermetallic phases. The invention further relates to a Processes for their production and their use as contact materials, preferably in electrical vacuum interrupters.

• geringer Materialabbrand,
• ausreichendes Schaltvermögen,
• geringe Schweißneigung,
• niedriger elektrischer Widerstand,
• gute Durchschlagfestigkeit (Spannungsfestigkeit),
• niedriger Abreißstrom.

Vacuum contact pads form the heart of the switching chambers in electrical vacuum switches and, according to the state of the art, generally consist of an arc-resistant, granular component (refractory metals such as W, Mo or Cr), embedded in a low-melting metal matrix with high conductivity (e.g. Ag, Cu or their alloys). The properties of the contact materials are subject to high and sometimes conflicting requirements, such as

• low material burn-off,
• sufficient switching capacity,
• low tendency to sweat,
• low electrical resistance,
• good dielectric strength (dielectric strength),
• low breaking current.

For medium-voltage vacuum circuit breakers in the range> 12 kV to approx. 30 kV and higher have proven to be particularly useful for CuCr composites proven. CuCr materials have very good current interruption properties and good dielectric strength (dielectric reconsolidation). At the in this required performance range is the small number of 10,000 switching cycles the erosion resistance of CuCr materials is sufficient.

In the low voltage range <1,000 V, the use of Vacuum contactors are becoming increasingly important. The used in this area Sagittarius have to withstand 1,000,000 or more switching cycles, and that Tear current should be as low as possible. To those used here As a result, vacuum materials have additional main requirements.

High-performance materials for this area are pure W / Cu, WC / Ag, WC / Cu Form or with other additives. The matrix component is particularly effective here Ag has a good current breaking behavior, while the high-melting component W or WC minimizes arcing under the influence of an arc.

• Bei zunehmender Spannung findet die Verwendung einer reinen Wolframkomponente ihre Begrenzung durch erhöhte Neigung zur Elektronenemission. Diese ist der Refraktärnatur des Wolframs (Smp 3.410 ° C) zuzuschreiben. Die Spannungsfestigkeit im Vakuum wird hierdurch geschwächt.
• Bei niedrigen Spannungen findet umgekehrt die Verwendung einer reinen Cr-Refraktär-Komponente ihre Begrenzung durch die mangelhafte Abbrandfestigkeit, die sich durch die aufsummierte Abbrandrate bei hohen Schaltspielen ergibt.

For the remaining gap between 1,000 and 12,000 V, it is difficult to design contact materials that meet the constantly increasing requirements for switching chambers for vacuum contactors due to the opposite properties of the pure refractory components W and Cr:

• With increasing voltage, the use of a pure tungsten component is limited by an increased tendency to electron emission. This is due to the refractory nature of the tungsten (mp 3,410 ° C). This weakens the dielectric strength in a vacuum.
• Conversely, at low voltages, the use of a pure Cr refractory component is limited by the inadequate erosion resistance, which results from the accumulated erosion rate at high switching cycles.

It would now be conceivable to mix the two differently melting metal parts Cr and W a refractory component quasi synthetic to set an optimal profile for the desired voltage range Melting point (i.e. for the switching property the erosion resistance) and Electron emission (i.e. dielectric strength) would result. Im switching electrical contact should reflect the negative properties of the previous Contact materials used (for Cr due to the low Melting point the high burn rate, at W due to the high Melting point the high electron emission or the low Voltage resistance) neutralize.

An attempt in this direction is described in EP-A-0 083 245, which i.a. a CuCrW alloy disclosed, which in a manner known per se powder metallurgical way by pressing the metal powder mixture as well Sintering in solid or liquid Cu phase is produced. Purpose of this publication is the production of a fine-grained composite. This is supposed to be through the Formation of a complete solid solution of the refractory metals in one another Caused by the metals W and Cr crystallizing in a cubic system become.

In order to test the usability of this teaching, according to the information from Composites made of CuCrW. After sintering in the liquid Cu phase the W grains can be found in their original shape and size Cr. The W-Cr particles are embedded in the Cu matrix (Figure 1). A mixed crystal from W and Cr of the kind postulated in the publication could in no case be detected. From a metallurgical point of view, this is not surprising since at a melting temperature of 1,100 to 1,200 ° C (above Cu liquidus) no conversion of tungsten with chromium is expected.

X-ray fluorescence analyzes of the material Cu 71% / Cr 24% / W 5% produced in accordance with the publication showed that the tungsten was insoluble in the surrounding matrix of Cr and Cu up to the detection limit. The total analysis over a Cr area of 10 x 14 µm ² shows pure Cr, ie W is below the detection limit of <0.1% (Figure 2). Conversely, no diffusion of Cr into the W particles could be detected: a point analysis shows pure W, ie Cr is below the detection limit of <0.1% (Figure 3). Thus a mutual penetration of the refractory metals Cr and W, ie mixed crystal formation, does not appear to be feasible in this way. There is no teaching in this document to achieve improved switching properties by mixing the refractory components Cr and W as intimately as possible and by using the different properties of the two pure components.

EP-A-0 668 599 similarly discloses a contact material made of CuCr with an additional auxiliary component from the group of tungsten, molybdenum, tantalum and niobium, which by diffusion of the refractory components in the liquid copper phase and subsequent quenching as a fine-grain distribution of the arc-resistant components in the Cu Matrix is generated.
For a CuCrW material, a mutual diffusion of Cr and W and an arc-resistant grain of Cr and W are described. The invention aims essentially at a fine-grained distribution of the individual refractory components in the metal matrix. The formation of mixed crystals or intermetallic phases of the refractory components with one another is not described.

The special requirements for materials for vacuum contactors for use in the voltage range between 1,000 and 12,000 V are therefore Mixtures of Cr and W described in Cu matrix not solved.

It is therefore an object of the invention to include a composite material a low-melting, current-carrying matrix made of, for example, Cu or Ag and to provide a granular additive from refractory components that the mentioned requirements for vacuum circuit breakers and vacuum contactors is sufficient, i.e. both high dielectric strength and thus low Electron emission, as well as excellent erosion resistance and thus for use in particular in the voltage range from 1,000 to 12,000 V. is suitable.

Another object of the invention is to provide a method for Manufacture of such composite materials, which is carried out in an economical manner can be.

Finally, the object of the invention is a composite material for use as a contact material, preferably as a switching contact for vacuum interrupters in Voltage range from 1,000 - 12,000V, to provide.

These tasks were solved by the surprising finding that a Material with advantageous properties is obtained when the refractory portion no longer consists of particles of one or more refractory components, but when mixed crystals or intermetallic phases from at least two Refractory components are present, these being preferred Embodiment have significantly different melting points. It is from the point of view of metal science, the formation of a α phase, consisting of the pure or highly concentrated refractory component, not always avoidable. It is crucial, however, that it is also used for Formation of mixed crystals or intermetallic phases of the used Refractory components come, which leads to significantly improved properties (e.g. low electron emission) of the composite material. Preferably should Compositions can be selected that support the formation of α-phases exclude.

According to the desired material properties are not, as in State of the art, by joint sintering, alloying additional components in the low melting matrix or through Mixing of different high-melting powder components set, but are replaced by pre-alloyed refractory components (in the form of Mixed crystals or intermetallic phases) modified.

The invention thus relates to a powder metallurgy Composite material comprising a matrix of a metal with a Melting point of at most 1,200 ° C and one embedded in this matrix Comical addition of at least two refractory components is characterized in that the refractory components in the form of mixed crystals or intermetallic phases.

Preferred embodiments of the composite material of the invention are The subject matter of claims 2-8. Among them, one is particularly preferred Composite material in which a or a first group of refractory components a melting point of 1,500 to 2,400 ° C and a second or a second Group of refractory components has a melting point of over 2,400 ° C.

Furthermore, a method for producing the composite material mentioned provided, which is characterized in that one powdery mixture of at least two refractory components Heating converts to a mixed crystal or an intermetallic phase and that powder obtained therefrom by cooling and crushing powder metallurgical route with a matrix metal with a melting point of connects at most 1,200 ° C.

Preferred embodiments of the method are the subject of the claims 10 and 11.

Another object of the invention is the use of the above Composite material as an electrical contact material, preferably as a switch contact for vacuum interrupters, especially in the voltage range from 1,000 to 12,000 V.

Figur 1:

ein Schliffbild eines Cu Cr W-Verbundes gemäß EP-A-0 083 245;

Figur 2:

eine Röntgenfluoreszenz-Summenanalyse von Cr aus dem Cu Cr W-Verbund gemäß EP-A-0 083 245;

Figur 3:

eine Röntgenfluoreszenz-Punktanalyse von W aus dem Cu Cr W-Verbund gemäß EP-A-0 083 245;

Figur 4:

ein Schliffbild von Cr W 70/30-Mischkristallen aus Beispiel 1;

Figur 5:

ein Schliffbild von Cr W 70/30-Mischkristallen mit dendritischer Unterstruktur aus Beispiel 1;

Figur 6:

eine Röntgenfluoreszenz-Summenanalyse von Cr und W aus CrW 70/30-Mischkristallen aus Beispiel 1;

Figur 7:

eine Verteilungsanalyse für W aus Cr W 70/30-Mischkristallen aus Beispiel 1; die weißen Punkte bezeichnen W, die großen schwarzen Flecken sind Poren im Schmelzkuchen;

Figur 8:

eine Röntgenfluoreszenz-Summenanalyse von Cr und W aus CrW 70/30-Mischkristallen mit chromreicher Unterstruktur aus Beispiel 1;

Figur 9:

ein Schliffbild von Cr W-Mischkristallen in Cu-Matrix aus Beispiel 2;

Figur 10:

eine Röntgenfluoreszenz-Summenanalyse einer intermetallischen Cr₂Ta-Phase aus Beispiel 3;

Figur 11:

eine REM-Aufnahme von Cr₂Ta-Körnern in Cr-Matrix aus Beispiel 3;

Figur 12:

ein Schliffbild von Cr W C 70/28.2/1.8-Mischkarbid mit dendritischer Unterstruktur aus Beispiel 4;

Figur 13:

ein Schliffbild von Cr W C 61/28/11 Mischkarbid aus Beispiel 4

The attached drawing shows:

Figure 1:

a micrograph of a Cu Cr W composite according to EP-A-0 083 245;

Figure 2:

an X-ray fluorescence sum analysis of Cr from the Cu Cr W composite according to EP-A-0 083 245;

Figure 3:

an X-ray fluorescence point analysis of W from the Cu Cr W composite according to EP-A-0 083 245;

Figure 4:

a micrograph of Cr W 70/30 mixed crystals from Example 1;

Figure 5:

a micrograph of Cr W 70/30 mixed crystals with dendritic substructure from Example 1;

Figure 6:

an X-ray fluorescence sum analysis of Cr and W from CrW 70/30 mixed crystals from Example 1;

Figure 7:

a distribution analysis for W from Cr W 70/30 mixed crystals from Example 1; the white dots indicate W, the large black spots are pores in the melt cake;

Figure 8:

an X-ray fluorescence sum analysis of Cr and W from CrW 70/30 mixed crystals with a chromium-rich substructure from Example 1;

Figure 9:

a micrograph of Cr W mixed crystals in Cu matrix from Example 2;

Figure 10:

an X-ray fluorescence sum analysis of an intermetallic Cr ₂ Ta phase from Example 3;

Figure 11:

an SEM image of Cr ₂ Ta grains in a Cr matrix from Example 3;

Figure 12:

a micrograph of Cr WC 70 / 28.2 / 1.8 mixed carbide with dendritic substructure from Example 4;

Figure 13:

a micrograph of Cr WC 61/28/11 mixed carbide from Example 4

The invention will now be explained in detail below.

The powder metallurgy composite of the present invention comprises a matrix of a metal with a melting point of at most 1200 ° C, in which a granular addition of at least two refractory components is embedded, the refractory components mixed crystals or include intermetallic phases from each other.

Relatively low-melting ones are suitable as the matrix of the composite material Metals with good electrical conductivity, as they are usually used for Vacuum contact pads are used. Cu is preferred as matrix material, Ag or Al. Alloys of these metals can also be used without that the proportions are critical.

Examples of refractory components that are suitable for use in the Compounds of the invention are suitable, namely the metals of groups V b V, Nb and Ta, and Vl b of the periodic table, namely Cr, Mo and W. In addition to the Metals in elemental form can also be nitrides, carbides, silicides or borides these metals (hereinafter referred to as "hard materials") and mixtures thereof or mixtures of the hard materials with the metals. The Use of the hard materials mentioned can change the properties of the Composite material, such as its weight, positively affect. The metals Cr and W are preferred as refractory components.

The quantity ratio of the refractory metals or hard materials used is not critical as long as it is guaranteed that by heating these components a Mixed crystal or an intermetallic phase is obtained. Within that The quantitative ratios of the metals or hard materials in certain limits wide ranges fluctuate. It is also within the scope of the invention if the ratio is such that only partly mixed crystals or intermetallic phases arise while an excess Metal component remains partially as a pure substance.

The refractory component is preferably at least 1, preferably at least 5, more preferably at least 10 and in particular at least 50% by weight from mixed crystals and intermetallic phases. The is particularly preferably Refractory portion to more than 90% and especially completely as a mixed crystal or intermetallic phase.

The term "mixed crystals" are homogeneous solid solutions To understand refractory metals or hard materials, their places in the crystal lattice the atoms of the different metals are occupied. The atoms forming hard materials with a small radius, can be placed on metal interstitial spaces Host grid be stored; see. Römpp Lexikon Chemie, 10th edition 1998, p. 2705.

"Intermetallic phases" are chemical compounds of two or more metallic elements whose structure is distinct from that of the metals differs. In addition to phases with a stoichiometric composition according to the existing valences, there are also those in which these exact composition just a special case in a broad Represents area of homogeneity. Specific examples of the intermetallic phases are the Laves phases, Hume Rothery phases and Zintl phases; see. Rompp Lexicon Chemie, 10th edition 1998, p. 1943.

The share of the refractory components in the total mass of the Composite is not particularly critical, but is typically 15 to 80, preferably 25 to 50 wt .-%. The proportion is accordingly Matrix metals usually 20 to 85, preferably 50 to 75 wt .-%.

In a preferred embodiment, the composite of the invention contains at least one refractory component with a melting point in the relatively low range of 1,500 to 2,400 ° C and at least one second refractory component with a relatively high melting point in the range of over 2,400 ° C. Examples of refractory components with a The melting point in the former range are Cr and Nb, while examples of the usable refractory components with a melting point above 2,400 ° C Metals are Ta, Mo and W. Preferred metal with lower melting point is Cr, preferred metal with a higher melting point is W. Also in this The embodiment is the quantitative ratio of the refractory components preferably such that when heated at least to a significant extent Mixed crystal or an intermetallic phase is formed.

From a practical point of view, it is desirable to have the respective amounts to select the refractory components so that they can be used with acceptable aparative Effort can be melted together. Accordingly, mixtures are made 10 to 90, preferably 30 to 70% by weight of the lower melting Refractory component, e.g. Chromium and 10 to 90, preferably 30-70 wt .-% of higher melting refractory component, e.g. Tungsten. Particularly suitable a mixture of about 70 wt .-% Cr and 30 wt .-% W. In particular the amounts of the refractory components are selected such that the higher melting refractory in combination with the lower melting refractory component completely with formation of mixed crystals or intermetallic phases.

• Sintern in fester Phase:
  Ein Metallpulver der niedrig schmelzenden Matrix und das erhaltene Mischkristallpulver werden gemischt, gepreßt und unterhalb des Schmelzpunktes des Matrixmetalls, bevorzugt unter Hochvakuum gesintert.
• Sintern in flüssiger Phase:
  Das erhaltene Mischkristallpulver wird gepreßt und bevorzugt unter Hochvakuum mit dem geschmolzenen Matrixmetall getränkt.

As the first document for the production of the composite material according to the invention, completely or almost completely homogeneous mixed crystals or intermetallic phases are produced by intimately mixing at least two refractory components as a powder and quickly melting, homogenizing and without using a suitable process which can produce a high energy density in the melting volume significant segregations can be cooled down quickly. The cooling rate should be greater than 100K / min, otherwise the polygonal structure tends to separate. The cooled melt cake is then comminuted in a suitable manner and a mixed crystal powder is sieved according to the required grain size. The mixed crystal powder obtained is further processed by powder metallurgy in one of the following ways together with a low-melting, highly electrically conductive matrix metal to give the desired composite:

• Solid phase sintering:
  A metal powder of the low-melting matrix and the mixed crystal powder obtained are mixed, pressed and sintered below the melting point of the matrix metal, preferably under a high vacuum.
• Sintering in the liquid phase:
  The mixed crystal powder obtained is pressed and preferably impregnated with the molten matrix metal under high vacuum.

The shaped bodies obtained from the sintering process are, due to the preferred high vacuum treatment, low in gas compared to parts conventionally sintered under protective gas, ie they contain reduced residual gas fractions of O ₂ , N ₂ or H ₂ . These blanks are further processed by machining finishing in the form of disks, rings or the like into suitable contact pieces which are used in vacuum interrupters.

The composite material of the present invention takes place as a contact material for example in vacuum interrupters. They are particularly suitable Composites of the invention for use in the stress range of 1,000 up to 12,000 V and here it is again the composite materials made of at least each a refractory component with a melting point in the range of 1,500 up to 2,400 ° C and at least one refractory component with a melting point of over 2,400 ° C, the mixed crystals or intermetallic phases of these Refractory components with melting points in each of the above Have areas.

The following non-limiting examples illustrate some preferred ones Embodiments of the invention:

Example 1:

70% by weight Cr metal powder (Cr: ≥ 99.8% by weight)
and 30% by weight of W metal powder (W: ≥ 99.95% by weight)
are mixed, pressed and melted under vacuum or protective gas. The melt is quenched and solidified as quickly as possible (cooling rate> 100 K / min). The resulting mixed crystals of W and Cr are almost homogeneous in their composition and show only weak inhomogeneities with regard to the mutual distribution of the individual components. The solidified melt shows a uniformly formed polygonal grain structure (FIG. 4). The metal grains W or Cr originally used have completely dissolved in the melt and can no longer be detected in the melt cake.

With slow cooling (cooling rate <100 K / min.) This tends to uniform polygonal structure for segregation, a dendritic forms Substructure (Figure 5).

These results can be confirmed by scanning electron microscopy as follows:

The sum analysis over a larger area of 0.5 x 0.7 mm ² defines the weight ratio Cr / W as 70/30 according to the weight (Figure 6). A distribution analysis W in Cr shows an essentially uniform distribution of W in Cr (FIG. 7). This area corresponds to that of a uniform polygonal structure as in FIG. 4.

A determined maximum deviation from this ideal composition is shown by the sum analysis over a small area 20 × 28 μm ² on a substructure designed as dendrite with Cr = 54 and W = 46% by weight (FIG. 8). This area corresponds to a section of mixed crystal with a substructure as in FIG. 5.

The melt cake is then broken up and ground. The Mixed crystal powder obtained is sieved to ≤ 160 microns and in the solid phase sintered. For this purpose, 75% by weight of Cu metal powder and 25% by weight of that obtained CrW mixed crystal powder mixed, pressed and below the melting point sintered by copper under high vacuum.

Example 2:

A CrW mixed crystal powder is prepared as described in Example 1, to ≤ 160 µm sieved and sintered in the liquid phase. For this purpose, the CrW mixed crystal powder obtained pressed in the manner and under high vacuum with liquid Copper soaked that a fitting in the composition Cu 60 wt .-% Cr / W 40% by weight is obtained (FIG. 9).

Example 3:

65% by weight of Cr metal powder (Cr ≥ 99.8% by weight) and 35% by weight Tantalum metal powder (Ta ≥ 99.9 wt .-%) are pressed and under vacuum or Shielding gas melted.

The analysis of the melt cake obtained shows polygonal, primarily precipitated grains of the intermetallic phase Cr ₂ Ta in the composition CrTa 37/63% by weight (corresponding to 67 at.% Cr and 33 at.% Ta) (see FIG. 10). These are surrounded by a matrix of Cr metal (Figure 11). This test result follows from the preselected composition of the green body from the metal components Cr and Ta close to the eutectic composition with ≈ 34% by weight tantalum. (see Massalski et al., Binary Alloy Phase Diagrams, Second Edition Vol. 2, p. 1339).

A Ta-rich starting composition up to a composition with 63-66% by weight Ta increases the proportion of the Cr ₂ Ta phase at the expense of the Cr phase up to pure Cr ₂ -Ta.

The melt cake is, as stated in Example 1 or 2, crushed and with Cu or Ag using powder metallurgy to form a metal composite processed further.

Example 4:

70% by weight of Cr metal powder and 30% by weight of WC powder are mixed and pressed and melted under vacuum or protective gas. The high-melting toilet goes completely in solution in the Cr melt that forms first. The Melt cake solidifies to a CrW mixed carbide with the nominal Composition Cr 70 / W 28.2 / C 1.8% by weight. Metallographic analysis shows local depending on the management of the solidification and cooling process Inhomogeneities in the form of smaller or larger dendrites (Figure 12). The higher melting refractory toilet has been completely in the new Mixed carbide dissolved.

The carbon content in the mixed carbide can be increased if the pure Cr metal is replaced by the relatively low-melting Cr ₃ C ₂ (mp. 1,850 ° C). This corresponds to the condition of claim 3. The melt cake then solidifies with a nominal composition of 61% by weight Cr, 28% by weight W and 11% by weight C (FIG. 13). Here, too, the original carbides have completely dissolved in favor of a new mixed carbide.

The melt cake is, as stated in Example 1 or 2, crushed and with Cu or Ag using powder metallurgy to form a metal composite processed further.

In a similar but not restrictive manner, carbides such as VC, NbC, TaC, TiC, nitrides such as TiN and TaN, silicides such as Ta ₂ Si and V ₃ Si and borides such as TiB ₂ can be used instead of the refractory components used here.

Example 5:

As stated in Example 4, further melt cakes are made in the Compositions CrNb 50/50% by weight and CrMo 70/30% by weight mixed, pressed, melted, then crushed, sieved and added to the respective Processed combined with Cu or Ag.

Claims (14)

Composite material produced by powder metallurgy, comprising a matrix made of a metal with a melting point of at most 1200 ° C and one granular addition of at least two embedded in this matrix Refractory components, characterized in that the Refractory components mixed crystals or intermetallic phases from each other. Composite material according to claim 1, characterized in that the proportion the refractory components 15-80, preferably 25-50% by weight, and the Proportion of the matrix 20-85, preferably 50-75% by weight, based on the Total mass of the composite material. Composite material according to one of claims 1 to 2, characterized characterized in that a or a first group of refractory components a melting point in the range from 1,500 to 2,400 ° C and a second or a second group of refractory components have a melting point Have 2,400 ° C. Composite material according to one of claims 1 to 3, characterized characterized in that the higher melting refractory component in Complete connection with the lower melting refractory component in the form of the formation of mixed crystals or intermetallic phases dissolves. Composite material according to one of claims 1 to 4, characterized characterized in that the matrix of at least one of the metals Cu, Ag and Al exists. Composite material according to one of claims 1 to 5, characterized characterized in that the refractory components from metals of group V b, (V, Nb, Ta) and Vl b (Cr, Mo, W) of the periodic table and their Nitrides, carbides, silicides, borides and mixtures thereof are selected. Composite material according to one of claims 1 to 6, characterized characterized in that the lower melting refractory component in an amount of 10-90, preferably 30-70 wt .-% based on the All of the refractory components are present. Composite material according to one of claims 1 to 7, characterized characterized in that a lower melting refractory component Cr and is a higher melting refractory component W. Method for producing a composite material according to one of the Claims 1 to 8, characterized in that a powdered Mix at least two refractory components by heating them into one Mixed crystal or an intermetallic phase converts and that powder obtained by cooling and grinding on powder metallurgical Away with a matrix metal with a melting point of connects at most 1,200 ° C. A method according to claim 9, characterized in that a mixture one or a first group of refractory components with a Melting point from 1,500 to 2,400 ° C and a second or a second Group of refractory components with a melting point of over 2,400 ° C. A method according to claim 9 or 10, characterized in that the Manufactured under protective gas or high vacuum. Use of a composite material according to one of claims 1 to 8 as electrical contact material. Use of a composite material according to one of claims 1 to 8 as a switching contact for vacuum interrupters. Use of a composite material according to claim 13 in Voltage range from 1,000 to 12,000 V.

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