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
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C32/00—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ
  • C22C32/001—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with only oxides
  • C22C32/0015—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with only oxides with only single oxides as main non-metallic constituents
  • C22C32/0021—Matrix based on noble metals, Cu or alloys thereof

Definitions

• the invention relates to a material for electrical contacts, in particular for contact pieces in low-voltage switching devices, which consists of silver, tin oxide and other additives.
• the invention relates to a method for manufacturing contact pieces from this material and to the associated contact piece.
• contact materials based on silver metal oxides (AgMeO), in particular AgCdO, have proven to be particularly advantageous in the past.
• AgMeO silver metal oxides
• cadmium is known to be one of the toxic heavy metals and when the contact pieces Cd0 are burned off, it is also released to the surrounding area, efforts have been underway for some time to replace the Cd0 with other metal oxides.
• These materials are said to have an arc burn-up that is just as small, as well as low welding power and, in particular, low heating in the case of continuous current flow, like the known AgCdO materials for contact pieces.
• AgSn0 2 contacts have a lower erosion compared to AgCd0, which leads to an increased contact life. Therefore, the size of the required contact pieces can advantageously be reduced in comparison to AgCd0, as a result of which a not inconsiderable saving in silver is achieved.
• EP-B1-00 24 349 a material based on AgSn0 2 is known in which the excess temperature is reduced compared to the pure AgSn0 2 by adding tungsten oxide (W0 3 );
• EP-B1-00 39 429 proposes bismuth oxide (Bi 2 0 3 ) as a further additive, with which the welding force is to be influenced in a favorable manner without increasing the contact resistance.
• EP-A1-00 56 857 states that the overtemperature behavior can also allegedly be improved by molybdenum oxide (Mo03) and / or germanium oxide (Ge0 2 ).
• Mo03 molybdenum oxide
• Ge0 2 germanium oxide
• Mo03 deteriorates the erosion behavior of AgSn0 2 in such a way that the contact life falls far below that of AgCd0.
• These disadvantages do not occur when using Ge0 2 ; however, due to the high price of germanium oxide, which is a multiple of that of silver, the contact piece becomes significantly more expensive. This is the economic advantage when using AgSn0 2 , namely a saving of silver due to the low erosion hold against AgCdO, largely canceled.
• the object of the invention is therefore to develop an electrical contact material based on silver and tin oxide, in which the overtemperature is reduced compared to the known AgSn0 2 material by admixing further additives, neither deteriorating the contact life nor making the material excessively expensive .
• the additives in combination are oxides of the metals tantalum (Ta205), copper (Cu0) and bismuth (Bi 2 0 3 ).
• tungsten or oxygen-containing tungsten compounds can also be present.
• the new material contains 5 to 20 mass% Sn0 2 , 0.1 to 5 mass% Ta 2 O 5 , 0.1 to 5 mass% Cu0, 0.1 to 5 mass% Bi 2 O 3 and the rest silver. If tungsten is present, its proportion is 0.05 to 3% by mass.
• the invention shows in particular the advantageous property of tantalum oxide in connection with predetermined amounts of Cu0, Bi 2 0 3 and optionally tungsten in the case of contact materials based on silver-tin oxide.
• contact materials also contain tantalum oxide to use.
• tantalum is used either as cadmium tantalum oxide or as tantalum oxide in conjunction with at least germanium. Because of the favorable wetting properties of the tantalum oxide, the contact erosion is favorably influenced in the material there. It has not yet been recognized that tantalum oxide can be used as an additive in silver-tin oxide-based contact materials.
• the materials according to the invention can be produced by known powder metallurgical processes. For example, to manufacture contact pieces, the material is subjected to extrusion into a strip after sintering. Contact pieces cut from this tape can be hard-soldered onto the contact carriers of conventional switching devices.
• Powders of the components A g , Sn0 2 , Ta 2 0 5 , Cu0 and Bi 2 0 3 are used as starting materials, a composition in mass fractions of 91.4% Ag, 7.5% Sn02, 0.5% Ta 2 O 5 , 0.3% Cu0 and 0.3% B1203 is selected.
• the powder batch is mixed and then subjected to powder metallurgical process steps from pressing, sintering and post-pressing with the usual pressures and temperatures: For example, 200 MPa have been used for pressing the powder, for sintering 850 - 900 C at one hour in air and 600 MPa for repressing have been shown to be suitable values.
• a strip as a semi-finished product is produced from the blank by extrusion at 700 ° C, from which contact pieces with a parallel structure can be separated.
• the contact pieces manufactured in this way can be hard-soldered directly onto the contact carriers of a conventional switching device.
• Powders of the components are used as in Example 1, with a composition in proportions by mass of 87.7% Ag, 10.5% Sn0 2 , 0.8% Ta 2 0 5 , 0.5% Cu0 and 0.5% Bi 2 0 3 is selected.
• the further production steps correspond to those of Example 1.
• Powder of components A g , Sn0 2 , Ta 2 0 5 , CuO, Bi 2 0 3 and additionally powder of pure tungsten are used as starting materials. For example, a mixture with mass fractions of 91.7% Ag, 7.0% Sn0 2 , 0.5% Ta205, 0.3% CuO, 0.3% Bi 2 0 3 and 0.2% W is selected.
• the powder batch is mixed and then subjected to the usual powder metallurgical process steps from pressing, sintering and post-pressing.
• a strip as a semi-finished product is produced from the blank by extrusion, from which contact pieces with a parallel alignment structure can be separated.
• Powders of the components are used as in Example 3, but now a composition in bulk proportions with 87.5% Ag, 10.5% Sn0 2 , 0.8% Ta 2 0 59 0.5% CuO, 0.4% Bi 2 0 3 and 0.3% W is selected.
• the contact pieces were connected until the original button was remelted due to arcing. This required a few thousand switching operations. Under the highest continuous current load permitted for the switchgear, the temperature on the movable contact piece was measured directly below the contact pieces. It has been shown that the influence of the contact material can best be detected at this point.
• the measured temperatures at the terminals via the V are ertechnische Kunststoff AgSn0 2 W0 3 11.5 0.5 33% higher than for AgCd012, while the pure AgSn02 plant Taffe by more than 44% higher. It can be seen that the materials according to the invention have excess temperatures which are between 7 and 23% lower than that of Comparative material AgSn0 2 11.5 W0 3 0.5 and thus at best reach the temperatures of AgCd0.
• the materials according to the invention with added tungsten compared to AgSn0 2 11.5 W0 3 0.5 have a longer lifespan at a lower excess temperature, while the materials according to the invention without tungsten are characterized by a lack of material displacement, very favorable excess temperature and a longer lifespan compared to AgCd0, which however are not completely reached the values of AgSn0 2 11.5 W0 3 0.5.
• the percentage composition of the material with the special oxide combination Sn0 2 , Ta 2 0 5 , Cu0 and B1 2 0 3 and optionally W can be varied further.
• Bi203 and optionally 0.05 to 1% by mass tungsten can be added either as pure tungsten or as tungsten oxide (WO 3 ) or other oxygen-containing tungsten compounds without the properties of the contact material being impaired.
• the material costs of the individual additional components are only about 40% compared to Ge0 2, which has so far been found to be particularly favorable. This enables the object of the invention to create an inexpensive contact material with favorable temperature behavior. Overall, suitable contact pieces for switching devices can now be produced.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Composite Materials (AREA)
• Contacts (AREA)

Applications Claiming Priority (4)

Publications (3)

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• 1984
  • 1984-12-18 EP EP84115754A patent/EP0152606B1/fr not_active Expired
  • 1984-12-18 DE DE8484115754T patent/DE3466122D1/de not_active Expired
• 1985
  • 1985-01-23 US US06/693,717 patent/US4565590A/en not_active Expired - Fee Related

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