Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention relates to an integrated electricalcontact material, and more particularly, it relates to an
electrical contact material integrated from Ag-SnO alloy piece
materials. This invention is also related to a method of
i producing this material, and also a composite electrical contact
made therewith.
` Ag-SnO alloy contact materials made by internal
oxidation were disclosed by the present inventor, for example
in United States Letters Patent N. 3,933,485. Those alloys,
which have metal oxides precipitated therein as the result of
internal oxidation, are composed of 1.5 - 10% by weight of tin,
0.5 - 6% by weight of indium, a trace amount of less than 0.5%
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~ by weight of iron family element metals, and the balance of
`; silver, and are advantageously utilizable in the present inven-
tion.
It has been affirmed by the present inventor through
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a number of experiments that Ag-SnO alloys are comparable with
or superior to Ag-CdO alloys in their various characteristics.
But, the former has the drawback in the manufacturing thereof
that the diffusion velocity of oxygen for the internal oxidation
of Ag-Sn alloys (for example, oxygen diffusion into the internal
alloy structures under an atmospheric condition of about 700C)
` is comparatively slower than that for Ag-Cd, viz., about half
it,~ of the latter's. This means that it takes a considerably long
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period of time to have Ag-Sn alloy of comparatively large
dimensions internally oxidized, and that the internal oxidation
,!,~,. of such alloy i~ sometimes incomplete.
; In order to overcome such drawbacks which are somewhat ~`
inherent to Ag-SnO alloys, and also in order to obtain advanta-
geously Ag-SnO alloy contact material of comparatively large
dimensions, the inventor has made this invention, in which a
number of pieces of Ag-SnO alloys (Ag - Sn 1.5-10% - In 0.5 - 5% -
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Ni or Co less than 0.5%), each having dimensions which enable
each piece to be completely internally oxidized in a compara-
tively short period of time, and which pieces are, for example,
in the shape of thin plates, wires, or granules, are congrega-
ted or assembled together under pressure into a desired mass
or shape, and are heated at a temperature of about the melting
point of silver, viz., 960C.
This integration step can be performed also by
congregating said number of Ag-SnO alloy pieces with silver,
copper, or alloys thereof, whereby it is possible to produce
composite contact materials having large dimensions or mass,
and being composed of said silver, copper or their alloys,
which are clad with Ag-SnO alloy materials. When copper is
utilized as a base for the integrated material of this invention,
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` said heat-treatment temperature shall preferably be about the
eutectic temperature of silver and copper, viz., 779C.
The electrical contact material thus obtained and
;~ integrated from Ag-SnO alloy pieces or materials, with or
;'?'~ without a base portion of silver, copper or their alloys, may
be subjected to heat-rolling or extrusion so as to shape the
contact material to a plate or wire of desired dimensions. In
; this instance, the aforementioned heat-treatment under the
melting point of silver would be conducted together with said
rolling or extrusion.
' It has been found from durability tests that the
integrated Ag-SnO alloy electrical contact made in accordance
with this invention i9 superior, especially with respect to its
contact resistance, to the corresponding Ag-SnO alloy contact
which is internally oxidized solidly as a unit, when the
30 contacts have comparatively large dimensions. This is because,
when a Ag-SnO alloy of relatively large dimensions is internally
oxidized primarily as a whole, the internal oxidation becomes
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incomplete, as aforementioned, resulting in making its inner
portion less hard, while its contact pressure decreases along
with wear of the contact, whereby contact resistance thereof
becomes large, resulting in undersireable welding thereof. On
the contrary, the novel contact disclosed herein has no such
phenomena, since it has even hardness throughout its mass
; and life.
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Working principles on which this invention has been
made are enumerated as follows:
(l) Metal oxides of the Ag-SnO having the afore-
mentioned compositions are stable above 700C and even above
the melting point of silver, 960C;
(2) Metal oxides precipitated in said Ag-SnO alloy
`~ are far harder than those of Ag-CdO alloy, and are about one ~
tenth of the latter in size. Hence, they and their dispersion -
phases within the alloy structures remain same even after
rolling or extrusion thereof. In addition, these extremely
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~ minute and hard metal oxides work to prevent congregated alloy
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pleces from sliding relative to each other when they are
20 subjected to pressure, whereby their fresh abutting surfaces
~; are kept fresh and active. This effect is noticea~e especially
when the present invention integrated material i9 made with
copper as a base thereof, and
(3) Stresses produced in the integrated Ag-SnO alloy
materials are relieved with a rolling or extrusion operation,
' since the operation can be held at a temperature about the
partial melting point of silver. This i~ also on account of
the discontinuation of silver grain boundaries within alloy
; structures, produced with hot-rolling or extrusion.
EXAMPLE 1
- An alloy of Ag - Sn 5% - In 1.7% - Ni 0.3% (in weight)
was rolled to a plate of lmm in thickness. The plate was cut
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to small plates of 60mm in width and 300 mm in length. The
small plates wère subjected to an internal oxidation at lO
oxidizing atm. and at the temperature of 700C for 40 hours.
Both surfaces of the small plates thus internally oxidized were
cleaned by 5% nitric acid solution.
A piece of silver plate of the same size as said
small plates, and ten pieces of said Ag-SnO small plates were
placed one above the other in layers, the silver plate being
, .,
the bottom-most layer. These assembled or congregated plates
were heated at the temperature of 800C for lO minutes, while
,
they were kept under a pressure of lton/cm . The plates inte-
grated in this manner to a mass were preheated to 800C and
rolled to a plate of 2mm in thickness, from which contacts of
6mm in diameter were punched out. Said contacts of the present
.s~
invention, and other contacts of the same size and composition
, which were internally oxidized as a unit at said size, were
tested regarding their performances as prescribed in A.S.T.M.
Test conditions were as follows:
Voltage A.C. : 220V
Current: 50 amps
,~ Load: reactor Pf = 0.2
~` Frequency: 60 times per minute
' Switching cycles: lOO,OOO
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; Contact preseure: 100 g
Results were as follows:
`~ Present Invention Normally oxidized
Aq-SnO alloY contact Aa-SnO alloy contact
Welding 7 8
., (times)
Contact pressure 2.0m-~ 3.5m~Z
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Wear Loss 23mg 25mg
EXAMPLE 2
An alloy of the composition as in Example l was
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; processed to a wire of 2mm in diameter. This wire was cut into
short wires of 300 mm in length. The short wires were subjected
to an internal oxidation at 3atm. of oxygen and at the tempera-
ture of 700C for 20 hours. After washing them with an acid
they were assembled or congregated into a bundle 50mm in
diameter. This bundle was subjected to a hot extrusion at the
temperature of 800C, whereby six pieces of wire of 4mm in
diameter were obtained. These wires were processed to form a
tape of 0.5mm in thickness and 4mm in width, while being
repeatedly subjected to annealing. To one of the surfaces of
this tape a different tape of the same dimensions, and composed
of Cu-Ni (30%) alloy, was press joined, while the tapes were
heated to a temperature of about 850C. The abutting surfaces
had eutectic structures which assured a strong joint.
The tape-shaped Ag-SnO alloy contact material thus
obtained had better elongation than Ag-SnO alloy contact
;~ materials of the type which were conventionally internally
oxidized. Contrary to conventionally oxidized Ag-SnO alloy
materials, which have poor tensile strength and are apt ~-
to have cracks when they are cut to a desired length, the
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present invention products were able to be welded to contact
leaves, and they were continuously cut to a predetermined
length.
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i EXAMPLE 3
An alloy of Ag - Sn 8% - In 3% - Ni 0.3% (in weight)
was prepared and melted. It was atomized by a blast of nitrogen
gas to produce granules of 0.3 to l.5mm in diameterO They were
`; subjected to an internal oxidation step in an oxidizing atmos- -
phere and at the temperature of 700C for 6 hours. They were
washed by an acid and congregated or assembled into the form
of a disk of 6mm in diameter and 2mm in thickness, with silver
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powders of one tenth of the total weight being placed at the
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bottom~ This disk-shaped contact was pressed under 3 tons,
and then sintered for 3 hours at the temperature of 900C and
under the flow of oxygen. This product was finally shaped
under the pressure of 5 tons.
' It was found from tests that said disk-shaped contact
'~ made in accordance with the present invention had contact
~ resistances as low as 30 to 50% of conventional ones.
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