TERNARY CALCIUM-TIN-LEAD ALLOY

ALLIAGE TERNAIRE DE CALCIUM, D'ETAIN ET DE PLOMB

English Abstract

ABSTRACT OF THE DISCLOSURE
Ternary lead alloys having from above 0.1 to
about 0.20% by weight calcium and from about 0.01 to
about 0.50% by weight tin, the percentages being based
upon alloy weight. The alloys are particularly suitable
for use in grids of conventional and maintenance free
lead-acid batteries. Grids of the novel alloys exhibit
improved stiffness and handleability and may be cast at
commercially acceptable speeds.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A lead-acid battery wherein at least one grid is
made of a ternary lead base alloy consisting essentially of lead,
from above 0.1 to about 0.20% by weight calcium and from about 0.01
to about 0.50% by weight tin, the percentages of the calcium and
tin being based on the alloy weight.
2. A lead-acid battery according to Claim 1 wherein the
positive grid is made of a ternary lead base alloy consisting
essentially of lead, from about 0.1 to about 0.20% by weight calcium
and from about 0.01 to about 0.50% by weight tin, the percentages
of the calcium and tin being based on the alloy weight.
3. A lead-acid battery according to Claim 1 wherein the
negative grid is made of a ternary lead base alloy consisting
essentially of lead, from above 0.1 to about 0.20% by weight calcium
and from about 0.01 to about 0.50% by weight tin, the percentages
of the calcium and tin being based on the alloy weight.
4. A directly cast battery grid for use in a lead-acid
battery system, said grid being made of a ternary lead base alloy
consisting essentially of lead, from about 0.10 to about 0.20% by
weight calcium and from about 0.01 to about 0.50% by weight tin,
the percentages of the calcium and tin being based on the alloy
weight.

Description

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The present invention xelates to ternary lead
base alloys having from above 0.1 to about 0.20% by weight
calcium and from about 0.01 to about 0.50% by weight tin,
based upon alloy weight.
Copending Canadian Patent Application No~ 209,677
filed September 20, 1974 and assigned to the present applicant,
discloses a lead base alloy containing 0.06%-0.10% calcium
and 0.10%-0.40~ tin which can be advantageously utilized to
form lead-acid battery grids that are particularly useful
in the preparation of maintenance free batteries having
excellent capacity reten~ion characteristics. head-calcium
alloys containing this amount of tin have a remarkably
improved resistance to drossing, thus permitting rapid casting
and accurate calcium content control. Batteries prepared with
grids fabricated from this alloy have unexpectedly improved
capacity retention characteristics.
While such alloys do provide suitable materials for
forming battery grids, there remains a desire to produce grids
which have improved stifness and handleability characteristics
and which can be rapidly cast into grids at the rapid speeds
used in commercial applications. It would be desirable, for
example, to provide an alloy which is capable of being cast
into grids at the rate of about 10 to 15 castings/minute.
It is accordingly an object of the present invention
to provide an alloy capable of being used to ~orm the grids
for lead-acid storage batteries of both the conventional and
maintenance free types.
28 Another object provides such an alloy characterized
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by the ability to form gxids having improved sti~fness and
handleability characteristics.
A still further object of this invention lies in
the provision of an alloy capable of being cast into grids
at commercially acceptable speeds.
Yet another and more specific object is to provide
an alloy which is capable of being rapidly cast into relatively
thin grids.
In brief, the present invention is predicated on the
discovery that highly desirable grids can be provided by
utiliæing a lead base alloy containing from above 0.1 to about
0;20% by weight calcium and from about 0.01 to about 0.50% by
weight tin, the percentages of each of the alloying constituents
being based upon the weight of the alloy. Grids formed from
such alloys have superior stiffness and handleability charac-
teristics, and the grids can be formed at the rate of 10 to
15 castings per minute with no difficulty.
For positive grids it is preferred to maintain the
calcium content below about 0.15% by weight of the alloy.
The tin content of the alloy can vary from about 0.01
to about 0.5% by weight of the alloy, but it is preferred to
maintain the tin content in the range of from about 0.10 to
about 0.35% based upon the weight of the alloy. Tin contents
within this range provide the desired performance characteristics
for the grids.
The alloys according to the present invention may be
cast directly into highly satisfactory grids. In contrast
it has been ound that ~rids which are directly cast from
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alloys having higher quantities o tin are deficient in certain
properties such as instantaneous strength and corrosion re-
sistance. For this reason, such alloys are unsuitable for
direct casting of battery grids and partiLcularly unsuitable
for direct casting of grids for use in maintenance-free batteries.
On the other hand, when the grids are fabricated by
- working after casting, a higher level of tin, for example 1~
or so, is preferred to provide desirable grid characteristics.
The alloys used for the grids in accordance with
the present invention can contain negligible amounts of im-
purities such as are typically found in commercially available
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battery grade lead. While impurities may be contained in
the other alloying constituents which are used, the relatively
smaller amounts of these constituents make the typical
impurities less important than those contained in the grade
of lead employed. Although ternary alloys are contemplated
herein, it should be appreciated that the alloys of the present
invention can include other ingredients so long as the~ do not
significantly adversely affect the desirable features attributable
to the present invention.
The alloys descrLbed herein may be produced in the
conventional manner by adding the alloying constituents in the
prescribed amounts to the molten lead and then mixing until the
mass is homogeneous. Production of the grids using the alloy
can then be accomplished by commercially used high speed grid
manufacturing techniques. Casting temperatures of from about
750F. to about 850F. into appropriate molds maintained at
a temperature of about 350 to 450~. have been found to be
satisfactory.
Thus, as has been seen, the present invention provides
an alloy which can be rapidly cast with low dross formation to
form grids having desirable performance characteristics. The
grids have good corrosion resistance and are quite useful as
positive grids. The handleability and stiffness characteristics
of grids employing the alloys of the present invention are
superior and thus they are also useful as negative grids. More-
over, such characteristics allow the formation of relatively
thin grids (e.g. - grids having thicknesses of about 0.060 inch
or less) at cor~mercially acceptable speeds of from 10 to 15
2~ castings/minute.
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