EP2831298A1

EP2831298A1 - Contact material

Info

Publication number: EP2831298A1
Application number: EP13715919.0A
Authority: EP
Inventors: Michael Bender
Original assignee: Umicore AG and Co KG
Current assignee: Saxonia Technical Materials GmbH
Priority date: 2012-03-26
Filing date: 2013-03-26
Publication date: 2015-02-04
Anticipated expiration: 2033-03-26
Also published as: CN104245976B; US20150060741A1; EP2831298B1; CN104245976A; EP2644723A1; EP2644723B1; WO2013144112A1; US9928931B2

Abstract

The present application relates to a new contact material, methods for the production of said contact material, and the use of said contact material.

Description

Contact material

For the production of electrical contacts in low-voltage switchgear, silver / metal and silver / metal oxide composites have proven themselves. The most commonly used silver / metal composite is silver / nickel, the main application of which is at lower currents.

Certain additives, such as WO3 or M0O3, have proven themselves in switching devices that have to withstand high thermal loads. Especially good proved

AgSnÜ2 with these additives in switchgear with rated currents of more than 100 A and under so-called AC4 load. At lower switching currents, however, the life of these materials is relatively short.

The AgSn02W03 Mo03 material is produced by powder metallurgy using the extrusion technique. The powder metallurgical production has the advantage that additives of any kind and quantity can be used. Thus, the material can be targeted to certain properties, e.g. Verschweißkraft or heating, to be optimized. In addition, the combination of powder metallurgy with the extrusion technology allows a particularly high efficiency in the production of the contact pieces. An internally oxidized AgSnO 2 In 2 O 3 material is also used. This

Material described in DE-OS 24 28 147, in addition to 5-10% Sn0 ₂ still contains 1 -6% In2Ü3. A targeted change in the concentrations of oxide additives to certain

It is not always possible to influence switching properties because of the oxidation kinetics.

In DE-OS 27 54 335 a contact material is described, which contains in addition to silver 1, 6 to 6.5 B12O3 and 0.1 to 7.5 SnO 2. This material can be produced both by internal oxidation and powder metallurgy. Such high B12O3

However, contents lead to embrittlement, so that the material can only be produced by individual sintering, but not by the more economical extrusion technique. From US 4,680,162 an internally oxidized AgSn02 material is known in the

Tin contents of more than 4.5% may contain additions of 0.1-5 indium and 0.01-5 bismuth. The metal alloy powder is compacted and then internally oxidized. These additives inhibit the inhomogeneous oxide precipitations customary in internal oxidation. Optimal contact properties shows this Material not.

The paper "Investigation into the Switching Behavior of New Silver-Tin Oxide Contact Materials in Proc. Of the 14th Int. Conf. On El. Contacts, Paris, 1988 June 20-24, pp. 405-409" discloses Switching behavior of powder-metallurgically produced electrical contacts of silver-tin oxide reported that may contain two further oxides from the series bismuth oxide, indium oxide, copper oxide, molybdenum oxide or tungsten oxide, wherein the exact composition of these materials nothing is said.

No. 4,695,330 describes a special process for producing an internally oxidized material with 0.5-12 tin, 0.5-15 indium and 0.01-1.5 bismuth. The powder metallurgical production of contact materials based on silver-tin oxide by mixing the powder, cold isostatic pressing, sintering and extrusion to semi-finished products is known for example from DE 43 19 137 and DE 43 31 526.

From US 4,141,727 contact materials of silver are known which contain bismuth tin oxide as a mixed oxide powder. Furthermore, in DE 29 52 128, the tin oxide powder is annealed at 900 ° C. to 900 ° C. before mixing with silver powder.

Due to increasing demands on the contact materials, the known materials do not always meet the requirements or for all applications.

Description 1. Electric, cadmium-free contact material containing at least one metal and magnesium stannate Mg 2 SnO 4.

2. Contact material according to item 1, wherein the metal is silver or a silver alloy.

3. Contact material according to item 1 or 2, wherein 0.2 to 60 percent by volume of magnesium stannate are included.

4. Contact material according to one or more of the items 1 to 3, wherein 5 wt .-% to 60 wt .-% magnesium stannate are included.

5. Contact material according to one or more of the items 1 to 3, wherein 0.5 wt .-% to 13 wt .-% magnesium stannate are included. Contact material according to one or more of the items 1 to 3, wherein 0.5 wt .-% to 5 wt .-% magnesium stannate are included. Contact material according to one or more of the items 1 to 6, wherein at least 60 wt .-% of the magnesium stannate present in the contact material has a particle size of 1 μηι or more. Contact material according to one or more of the items 1 to 7, wherein the magnesium stannate present in the contact material wholly or partially has a particle size of 20 nm to 1 μηι. Contact material according to one or more of the items 1 to 8, wherein the magnesium stannate present in the contact material wholly or partially has a particle size of 100 nm to 900 nm. Contact material according to one or more of the items 1 to 9, containing further oxides. Contact material according to one or more of the items 1 to 10, wherein additionally borrowed oxides from the group consisting of magnesium oxide, copper oxide, bismuth oxide, tellurium oxide, tin oxide, indium oxide, tungsten oxide, molybdenum oxide, their mixed oxides or combinations thereof are included. Contact material according to one or more of the items 1 to 1 1, wherein the further oxides, individually or in combination, may be contained in amounts of 0.5 wt .-% to 30 wt .-%. Contact material according to one or more of the items 1 to 12, wherein the further oxides, individually or in combination, in amounts of 2 wt .-% to 20 wt .-% or from 0.5 wt .-% to 7 wt .-% may be included. Contact material according to one or more of the items 1 to 13, being used as further oxides tin oxide, optionally with indium oxide and / or tellurium oxide.

Contact material according to one or more of the items 1 to 14, wherein at least 60 wt .-% of existing in the contact material further oxides have a particle size of 1 μηι or more. 16. Contact material according to one or more of the items 1 to 14, wherein the further oxides particle sizes of 20 nm to 2 μηι or 50 nm to less than 2000 nm, or 100 nm to 1800 nm or 200 nm to 900 nm.

17. Contact material according to one or more of the items 1 to 14, wherein 60% of the further oxides have particle sizes of 100 nm to 900 nm.

18. Contact material according to one or more of the items 1 to 17, wherein the total oxide content is up to 60 wt .-%.

19. Contact material according to one or more of items 1 to 18, obtainable by powder metallurgy production. 20. Use of a contact material according to one or more of items 1 to 19 for the production of electrical contact pieces.

21. Electrical contact containing a contact material according to one or more of items 1 to 19.

22. Moving contact piece of a switching device or electrical switching device, containing an electrical contact according to item 21.

23. A process for the preparation of a contact material of metal and magnesium stannate Mg2Sn04 by mixing powdered magnesium stannate

Mg 2 SnO 4 or a magnesium stannate precursor compound with at least one metal powder and optionally further oxides, pressing the mixture to obtain a compact and sintering the compact around a sintered compact.

24. Method according to item 23, wherein the resulting sintered compact is shaped, in particular extruded, in a further process step,

25. The method of item 23, wherein the sintered compact is a contact piece. 26. The method of item 25, wherein the sintered article additionally contains copper oxide.

27. Contact material, obtainable by a method according to points 23 or 24. Detailed description

It was the object to provide a new metal composite, which shows when used as contact material in electrical switching devices over common silver-based silver-tin oxide composite materials improved burn-off behavior and a lower contact resistance. This object is achieved by a metal composite material containing at least one metal and magnesium stannate. Magnesium stannate, Mg 2 SnC 4, is a compound known from the literature, whose preparation is described, for example, in Materials in Electronics, 16 (2005), pages 193 to 196, Journal of Power Sources 97-98 (2001), pages 223-225 or Ceramics International 27 (2001), pages 325 to 334. For the preparation of this compound can

Magnesium oxide MgO and tin oxide SnÜ2 in the corresponding molar ratio (ie MgO: SnC> 2 = 2: 1) are intensively mixed (for example by wet or dry grinding), optionally dried and then for about 15 to about 25 hours at temperatures of about 1200 ° C calcined to about 1600 ° C. In general, there are no special requirements for the atmosphere, so that it is possible to calcine in air. In this way, a mixture of magnesium stannate and magnesium oxide can be obtained as shown in Figure 1, with about 4.4% magnesium oxide present with about 95.6% magnesium stannate. By using an excess of about 10% magnesium oxide, up to 98% Mg2SnO4 magnesium stannate can be achieved.

The present patent application also relates to the use of a contact material containing at least one metal and magnesium stannate for the production of electrical contact pieces, as well as electrical contacts containing such a contact material as further described. In particular silver or silver alloys can be used as the metal. Well suited, for example, silver-nickel alloys. Silver alone also has excellent properties for many applications. Cadmium, on the other hand, is not included and may be present in the maximum range of unavoidable impurities. Magnesium stannate may generally be used in amounts of 0.02 to 60% by volume, or 0.02% by volume, in particular 0.2% by volume, to 25% by volume, (= up to 13% by weight), in particular 2% by volume .%, to 25 vol.%, or 0.02 vol.%, in particular 0.2 vol.%, To 60 vol.%. (= to% by weight), in particular 2% by volume, up to 60% by volume. or 0.02% vol. especially 0.2% by volume, up to 5% by volume (= 2.34% by weight). The amounts of magnesium stannate Mg.sub.2SnO.sub.4 to be added can be selected according to the application in advantageous amounts, with the addition of about 0.02% by volume to 25% by volume (.about.0-13% by weight) or 0.5% by weight being used for extruded materials. % to 13 wt., for individually pressed materials (similar to known Ag / W and Ag / WC materials) 0.02% to 60% by volume. (= 0-40 wt%) or 0.5 wt% to 40 wt%. When using magnesium stannate Mg2SnÜ4 as an additive 0.5 wt .-% to 5

Wt .-%, or 0.5 wt .-% to 1 wt .-% or 1 wt .-% to 2.5 wt .-% or 0.02 vol.% To 5 vol.% (= 0 - 2 , 34 wt.%) Particularly suitable. The magnesium stannate Mg2SnÜ4 is present in the contact material as a disperse phase, while the metal forms the continuous phase. The magnesium stannate Mg 2 Sn 4 can have particle sizes of at least 1 μm. In particular, at least 60% of the magnesium stannate have particle sizes of 1 μm or more, which is advantageous in particular in the case of reshaping further processing, for example by extrusion. If contact pieces are individually sintered, instead of or in combination with magnesium stannate, Mg 2 Sn 4 with a particle size of 1 μm or more may also be used

Particle sizes of 20 nm to 1 μηη or 50 nm to less than 1000 nm, in particular 100 nm to 900 nm are used. In this case, advantageously 60% of the magnesium stannate have particle sizes of 100 nm to 900 nm. In addition, the contact material may have further oxides. In particular, the contact material may additionally contain oxides from the group consisting of magnesium oxide, copper oxide, bismuth oxide, tellurium oxide, tin oxide, indium oxide, tungsten oxide, molybdenum oxide or combinations thereof, their mixed oxides or combinations thereof. For example, Bi ₆ WO ₂ may be present as mixed oxide. The above oxides may be present individually or in total in amounts of from 0.5% to 30% by weight, or in amounts from 2% to 20% by weight, up to 7% by weight, in particular be contained up to 2 wt .-%, or in amounts of 0.5 wt .-% up to 7 wt .-% or in amounts of 0.5 wt .-% up to 2 wt .-%. In one embodiment, tin oxide is optionally used with indium oxide, tellurium oxide or both as further oxides. In a further embodiment, the total oxide content, ie the combined content of magnesium stannate, is Mg 2 SnO 4 up to 60% by weight. In one embodiment, at least 60% of the further oxide, that is, for example, of the tin oxide, has particle sizes of 1 μm or more, which is advantageous, in particular, in the case of reshaping further processing, for example by extrusion.

In one embodiment, the further oxide can also be used particle sizes of 20 nm to 2 μηη or 50 nm to less than 2000 nm, in particular 100 nm to 1800 nm or 200 nm to 900 nm. In this case, advantageously 60% of the further oxide particle sizes of 100 nm to 900 nm.

The contact material can be obtained by a manufacturing method selected from powder metallurgy production, internal oxidation or combinations thereof. In powder metallurgical production of the material is by mixing a powder of the metal or an alloy with magnesium stannate Mg2Sn04 or a

Magnesium stannate precursor compound and optionally other oxides, cold sostatisches static compression of the powder mixture, and sintering at temperatures of about 500 ° C to about 940 ° C and optionally forming the sintered material, such as by extrusion to wires or profiles, the contact material. When

Magnesium stannate precursor compound can be used compounds different from magnesium stannate, which decompose under the process conditions in magnesium stannate and optionally other decomposition products. The further decomposition products must either be volatile in the process conditions or be substances whose presence does not disturb the properties of the product obtained, ideally substances whose presence is desired, such as the metal used or another oxide selected from the group consisting of magnesium oxide, copper oxide, Bismuth oxide, tellurium oxide, tin oxide, indium oxide, tungsten oxide, molybdenum oxide or their combinations, their mixed oxides or combinations thereof. Suitable compounds are, for example, alkoxides of tin and magnesium, such as, for example, hexakis (2-methyl-2-propanolato)] bis [(2-methyl-2-propanolato) tin] di-magnesium, CAS no. 139731-82-1.

It is useful if the magnesium stannate used or the magnesium stannate precursor compound and / or further oxides already before mixing with the powder of the metal or an alloy such as silver powder, the desired particle size or particle size distribution, or more than 60 % By weight already before mixing with the powder of the metal or an alloy, such as For example, silver powder, have a particle size of more than 1 μηη. In this case, too fine magnesium stannate or else other oxides can be coarsened by a heat treatment in which, for example, annealed at temperatures of about 700 ° C to about 1400 ° C until more than 60 wt.% Of magnesium stannate or other oxides have a particle size of more have 1 μηη. The use of these coarsened oxide powders, after sintering the compacts, provides a material which is more ductile than materials having smaller oxide particle sizes and therefore can be more easily deformed, which may be advantageous in further forming treatment, such as extrusion. In individual sintering of contacts, as described above, magnesium stannate (Mg 2 SnO 4) powders with smaller particle sizes may be used, in which case additives such as sintering activators are advantageous, for example copper oxide CuO, nanoscale silver powder or other nanomaterials. In this case, of course, magnesium stannate can be used in which 60 wt.% Even before mixing with the metal powder have a particle size of at least 1 μηη, but also magnesium stannate (Mg2Sn04), in which

60% of the magnesium stannate has particle sizes of 50 nm to less than 1000 nm, in particular 60% of the magnesium stannate particle sizes of 100 nm to 900 nm.

For example, when produced by internal oxidation, an alloy of silver with base metals is made pyrometallurgically and often heat-treated in pure oxygen under overpressure to form a contact material. Such processes are known from the literature and are described, for example, in EP 1505164 and EP 0508055.

In the production by internal oxidation in combination with powder metallurgy production, for example, as a powder of the metal or an alloy, a metal powder may be used which is e.g. contains further oxides which have been produced by internal oxidation, such as, for example, silver containing tin oxide. Further processing then proceeds by powder metallurgy, that is to say by addition of magnesium stannate and / or further oxides and / or metal powder, subsequent pressing, sintering and, if appropriate, forming, such as, for example, Extrusion.

In one embodiment, the contact material contains in particular silver and magnesium stannate and moreover only conventional impurities. In a Embodiment contains the contact material magnesium stannate in an amount of 0.2 to 20 wt .-% and ad 100 wt .-% silver and conventional impurities.

In a further embodiment of the invention, the contact material contains magnesium stannate, which has at least 60% of a particle size of 1 μm or more, in an amount of 0.2 to 20% by weight and ad 100% by weight of silver and conventional impurities.

Examples

example 1

Preparation of magnesium stannate 13.03 g SnO ₂ and 6.97 g MgO were weighed in and wet-ground for ₂ × 5 minutes at 250 rpm (Fritsch Pulverisette 5, 2 mm ZrO ₂ balls, dry isopropanol). The powder mixture is dried in a drying oven (temperature) and then comminuted with a mortar.

The crushed powder mixture is calcined at 1400 ° C for 20 hours in air and then ground to a particle size (d50) of 2 μηη (Fritsch Pulverisette 5, 2 mm Zr0 ₂ balls, dry isopropanol). By X-ray diffraction on the reaction product and Rietveld refinement, the resulting product was found to consist of 95.6% dimagnesium stannate (Mg ₂ Sn0 ₄ ) and 4.4% cassiterite (SnO ₂ ). Preparation of the Contact Material Containing Mg ₂ SnO ₄

914.4 g of silver powder (Umicore, atomized silver powder, sieved to <42 μηη) with 17.07 volume percent Mg ₂ Sn0 ₄ powder (85.6 g) in a mixing unit (MTI mixer 8 min., 1000 U / min ) mixed. The powder mixture is filled into a plastic cylindrical shape and cold isostatically pressed into a bolt at a pressure of 800 bar. This stud is sintered for 2 h at 820 ° C and then extruded.

Comparative Example ₂ Production of the Contact Material Containing SnO ₂ 880 g of silver powder (same silver powder as in Example 1) are mixed with 120 g corresponding to 17.07% by volume Sn0 ₂ powder in a mixing unit (MTI mixer, 8 min., 1000 rpm). The powder mixture is filled into a plastic cylindrical shape and cold isostatically pressed into a bolt at a pressure of 800 bar. This stud is sintered for 2 h at 820 ° C and then extruded.

Tensile tests according to EN ISO 6892-1 were carried out with samples of both contact materials and the elongation at break for both contact materials was determined to be 27%. From the contact materials produced contact pieces are made after extrusion (5 mm wire, semi-finished, soldered and turned off, then switched) and with these contacts switching experiments in a circuit breaker with 500 circuits, a current of 350 A and Blasfeld: 30 mT / kA performed , The results are shown in FIGS. 2 and 3.

FIG. 2 shows the burnup in mg per switching operation for both contact materials which have an oxide content of 17.07% by volume. The lower column shows the change at the fixed contact, the upper column at the moving contact. It can be seen that the magnesium stannate (Mg 2 SnO 4) and silver based

Contact material shows improved burn-off properties.

FIG. 3 shows the contact resistances in mOhms for both contact materials, which are given as mean values (respectively right-hand column) and as 99% values. It can be seen that the averages are comparable, but the 99% values are significantly lower for the magnesium stannate (Mg 2 SnO 4) and silver-based contact material, and thus significantly improved over the silver-tin oxide material.

Claims

claims

1 . Electric, cadmium-free contact material containing at least one metal and magnesium stannate Mg2SnÜ4.

2. Contact material according to claim 1, wherein the metal is silver or a silver alloy.

3. Contact material according to claim 1 or 2, wherein 0.2 to 60 percent by volume of magnesium stannate are included.

4. Contact material according to one or more of claims 1 to 3, wherein 5 wt .-% to 60 wt .-% magnesium stannate are included.

5. Contact material according to one or more of claims 1 to 4, wherein at least 60 wt .-% of the magnesium stannate present in the contact material has a particle size of 1 μηη or more.

6. Contact material according to one or more of claims 1 to 4, wherein the magnesium stannate present in the contact material wholly or partially has a particle size of 20 nm to 1 μηη.

7. Contact material according to one or more of claims 1 to 6, wherein additional oxides from the group consisting of magnesium oxide, copper oxide, bismuth oxide, tellurium oxide, tin oxide, indium oxide, tungsten oxide, molybdenum oxide, their mixed oxides or combinations thereof are included.

8. Contact material according to one or more of claims 1 to 7, obtainable by powder metallurgical production.

9. Use of a contact material according to one or more of claims 1 to 8 for the production of electrical contact pieces.

10. An electrical contact containing a contact material according to one or more of claims 1 to 8.

1 1. Movable contact piece of a switching device or electrical switching device, comprising an electrical contact according to claim 10.

12. A process for the preparation of a contact material of metal and magnesium stannate Mg2SnÜ4 by mixing powdered magnesium stannate

Mg 2 Sn 4 or a magnesium stannate precursor compound with at least one metal powder and optionally further oxides, pressing the mixture to obtain a compact and sintering the compact around a sintered compact.

13. The method according to claim 12, wherein the resulting sintered compact is formed in a further process step, in particular extruded,

14. The method of claim 12, wherein the sintered compact is a contact piece.

15. The method of claim 14, wherein the sintered additionally contains copper oxide.

16. Contact material, obtainable by a method of claims 12 or 13.