U.S. patent number 3,913,201 [Application Number 05/365,842] was granted by the patent office on 1975-10-21 for bonded material for electrical contact pieces.
This patent grant is currently assigned to Siemens Aktiengesellschaft. Invention is credited to Rudolf Scherbaum, Horst Schreiner.
United States Patent |
3,913,201 |
Schreiner , et al. |
October 21, 1975 |
Bonded material for electrical contact pieces
Abstract
Bonded or compound material for electrical contact pieces,
consisting of silver as an original metal with up to 20% by weight
of at least one finely divided metal oxide, such as CdO, SnO.sub.2,
ZnO, MgO and/or NiO, and up to 15% by weight of finely divided
lead.
Inventors: |
Schreiner; Horst (Nuremberg,
DT), Scherbaum; Rudolf (Regensburg, DT) |
Assignee: |
Siemens Aktiengesellschaft
(Berlin and Munich, DT)
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Family
ID: |
27181188 |
Appl.
No.: |
05/365,842 |
Filed: |
June 1, 1973 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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839050 |
Jul 3, 1969 |
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Foreign Application Priority Data
Current U.S.
Class: |
428/546;
428/539.5; 252/514 |
Current CPC
Class: |
C22C
32/0021 (20130101); H01H 1/0237 (20130101); Y10T
428/12014 (20150115) |
Current International
Class: |
H01H
1/0237 (20060101); C22C 32/00 (20060101); H01H
1/02 (20060101); B22F 001/00 (); H01B 001/02 () |
Field of
Search: |
;29/182.5,182.2 ;75/206
;752/514,519,520,521 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1,032,519 |
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Jun 1966 |
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GB |
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1,248,303 |
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Aug 1967 |
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DT |
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Primary Examiner: Padgett; Benjamin R.
Assistant Examiner: Hunt; B. H.
Attorney, Agent or Firm: Lerner; Herbert L.
Parent Case Text
This is a continuation-in-part application of application Ser. No.
839,050, filed July 3, 1969 now abandoned.
Claims
We claim:
1. Bonded material, particularly for electrical contact pieces,
consisting of silver, from 0.5 to 20% by weight of one finely
distributed metal oxide selected from CdO, SnO.sub.2, ZnO, MgO and
NiO and mixtures thereof, and from 3 to 15% by weight of finely
divided lead uniformly embedded in said silver.
Description
AgNi 10 and AgCdO 10 are frequently used as bonded or compound
material for electrical contact pieces. These contact pieces cannot
completely prevent the welding of the contact pieces, particularly
in short-circuit switching conditions, during the switching-on and
switching-off of short circuits. In the case of automatic switches
or power-protection switches, this fact can lead to disturbances of
the operation or to failure of the apparatus.
Even the known sinter materials used for electrical contact pieces
which are comprised of silver with 0.5 to 20% lead content, wherein
the lead is finely distributed in the silver sinter and is
essentially embedded in an undissolved condition, do not yield
sufficiently satisfactory results during the operation of
air-controlled AC automatic devices or automatic switches.
To reduce the welding tendency, sintered materials were suggested
whose original or base material of silver contained metal oxide and
graphite particles which had been very uniformly installed.
Although this material helped to reduce the welding property, it
increased the burn-off.
The object of the present invention is to provide a compound or
bonded material, which is particularly suitable for electrical
contact pieces and which does not entail the aforementioned
disadvantages. The bonded material, according to the invention, is
comprised of silver as the original metal, into which from 0.5 to
20% by weight of at least one finely divided metal oxide and from 3
to 15% by weight of finely divided lead, preferably between 3 and
10% by weight, are uniformly embedded. Electrical contact pieces
comprised of bonded material of the present invention comply with
all switching requirements for the most minute automatic switches,
without welding of the contact pieces. In addition to the small
welding property associated with switches during short circuits,
particular mention should be made with regard to the small contact
burn-off under rated current, and the relatively low contact
resistance as well as the slight contact heating, caused
thereby.
Particularly suitable metal oxides are, for example, CdO,
SnO.sub.2, ZnO, MgO or NiO. One or several of the metal oxides can
be embedded, in fine distribution, along with the lead, in the
original silver metal. Especially favorable were found to be
electrical contact pieces comprised of combinations AgCdO 10 Pb 5;
AgSnO.sub.2 6 Pb 5; AgMgO 1 NiO 1 Pb 10, whereby the numbers relate
to % by weight. The numbers used with other materials in the
specification have the same meaning. Of the metal oxide component
of the bonded material of the invention, the preferred range for
CdO, SnO.sub.2 and ZnO is 5% to 15% by weight, and for MgO and NiO
is 0.05% to 2% by weight.
The indicated advantages appear to be obtainable through the
special structural build-up, in a composition according to the
invention. This can be obtained for example by mixing fine-grained
electrolysis-silver powder or precipitated silver powder with a
finely divided metal oxide and a lead powder < 60 .mu.m.
Following an intensive blending, this is condensed by pressing into
a contact-stable pressed body.
However, the AgMeO powder, wherein Me represents a metal such as
Cd, Mg, etc., can also be produced as a bonded powder, through
precipitation mixing. The bonded powder is virtually blended with a
lead powder < 60 .mu.m and the powder mixture is condensed, by
pressing, into a compressed body with stable edges. The
precipitation mixture, e.g., of AgCdO bonded powder, can be
obtained from an aqueous solution of the nitrates, with NaOH, by
precipitating the hydroxides with NaOH and thereafter thermally
dissociating the hydroxides in an oxidizing atmosphere.
Finally the silver-metal oxide bonded powder (e.g., AgCdO 10
powder) can be produced through a mechanical break-up of the melt
of AgMe (e.g., AgCd 9 alloy), which can result from blowing apart
or from a mechanical reduction of falling molten stream
(centrifugal powder or pressure atomizer powder). Following the
interior oxidation of the AgMe powder into AgMeO (e.g., AgCdO 10),
the bonded powder is mixed with lead powder < 60 .mu.m and the
mixture is condensed, by pressing, into a compressed body with
stable edges.
The rest of the method is the same in all cases. The compressed
body is sintered in a neutral atmosphere (nitrogen or argon) and is
stabilized thereby. The sintered, formed contact body can be
calibrated by subsequent cold pressing and be further compressed
thereby.
In an example of the bonded or compound material of the invention,
AgCdOPb was formed from a starting material consisting of a powder
mixture of AgCdO 10% by weight and Pb 5% by weight. The powder
mixture was compressed at a pressure of 6 tons/cm.sup.2. A pressure
density of 9.3 to 9.7 g/cm.sup.3 and a degree of volumetric filling
that was 0.907 to 0.946 resulted therefrom. Subsequently, the
compressed mixture was sintered at a temperature of 650.degree.C in
a nitrogen atmosphere for a period of 30 minutes. The resulting
density was 8.5 to 8.9 g/cm.sup.3, corresponding to a degree of
volumetric filling of 0.830 to 0.868. The sintered body had from 15
to 17% pores. In a subsequent compression at 6.8 t/cm.sup.2, the
sintered body attained a theoretical density of 10.25
g/cm.sup.3.
The invention, together with additional objects and advantages
thereof, will be more clearly understood from the following
description of the bonded material when read in connection with the
accompanying drawing, wherein:
FIGS. 1, 2 and 3 are micrographs of the structure of the bonded or
compound material AgCdOPb respectively at magnifications of 500 :
1, 200 : 1 and 100 : 1.
Referring now to the Figures of the drawing, there is shown therein
metallographically an example of the bonded or compound material of
the invention. In the view of largest magnification of FIG. 1, the
silver matrix of the material AgCdOPb appears white, while the
discrete lead inclusions are shown as finely divided black
particles, and the metal oxide, CdO, is gray as well as linear in
appearance. From FIGS. 2 and 3 of lesser magnification it is
plainly apparent that the lead and the CdO are substantially
uniformly distributed over the entire cross section containing the
matrix of Ag.
A particular advantage of the contact pieces according to the
present invention is in the coating of the conventional carrier
metals. While, for example, contact pieces comprised of AgCdO 10
must be plated, because of their poor wettability, with a layer of
a good solderable metal, the AgCdO Pb (AgMeO Pb) appears to have,
even as a one-layer contact piece, during its hard soldering upon a
conventional carrier metal, such as copper, brass, bronze, CuBe,
etc., an impeccable wetting through the hard solder and, therefore,
excellent soldering characteristics. The good wettability during
hard soldering, which can be effected for example at 615.degree.C,
is ensured by the uniformly distributed lead. The hard soldering
can also be effected, e.g., with silfos solder (a
phosphorus-containing silver hard solder). Contact pieces, which
are in a sintered state, are also suitable for hard soldering upon
the carrier metal. The final condensation into the virtually
pore-free contact pieces results during the soldering process, on a
welding machine, whereby heating is effected by two metallic
electrodes, with a direct current passage, by means of contact
pressure across the electrodes or, immediately following the hard
soldering, by a subsequent cold pressing process.
* * * * *