GB2197342A - Lead base arsenic-tin alloy - Google Patents

Abstract

Arsenic-tin-lead alloy comprising from about 0.3 to about 0.8 wt% arsenic, from about 1.5 to about 3.0 wt% tin, and the balance lead is provided. Grids, straps, intercell connectors, element posts, bushings, and terminal components for lead-acid batteries comprising the alloy, as well as lead-acid batteries comprising such components also are provided. Welding rods composed of the alloy are provided as well.

Description

SPECIFICATION Lead base arsenic-tin alloy useful for forming battery components This invention relates generally to alloy compositions and, more particularly, to alloy compositions useful in forming battery components and for welding such components. It also relates to lead-acid storage batteries comprising components formed from the novel alloys.

BACKGROUND OF THE INVENTION Lead-acid batteries typically comprise electrochemical components set within a container having a sealed cover. The interior of the container typically is divided by partition walls into a series of cells, and within each cell is disposed an electrode stack in contact with electrolyte, e.g., a sulfuric acid based electrolyte.

The electrode stacks comprise alternate positive and negative plates and a separator between each adjacent plate pair. The plates themselves comprise a grid which supports electrochemically active material, typically lead oxides or lead oxides containing some finely divided metallic lead.

The grids generally incorporate an integral lug on their upper end.

The positive and negative plates of each cell stack are connected in parallel across the top of their grid lugs, respectively, by positive and negative conductive straps. An intercell connector, as its name implies, is used to connect, in series, the electrode stacks in adjoining cells. The positive and negative straps, respectively, in each of the two terminal cells are electrically connected to positive and negative terminals, typically through, inter alia, element posts integrally formed with the straps. It is common for the terminals to be formed, at least partially, from the element posts and bushings mounted in the container or cover wall.

The grids, straps, intercell connectors, element posts, bushings, and terminals are made from a variety of lead alloys, and there has been, and is continuing development of lead alloys for such components. For convenience, such battery components which typically are formed of lead alloys shall be referred to collectively as lead alloy battery (LAB) components. Although the alloys are composed primarily of lead, pure lead is poorly suited for LAB components, and it must be alloyed with other metals to improve its castability and mechanical properties. More particularly, antimony long has been used to simplify casting of lead into LAB components and to harden it sufficiently to enable such components to withstand the rigors of modern assembly techniques and battery service conditions.Lead alloys comprising higher concentrations of antimony, however, are not entirely compatible, in an electrochemical sense, within a lead-acid system.

During cycling, positive LAB components, primarily the positive grids, if composed of lead alloys comprising antimony, are susceptible to electrochemical attack and corrosion in the presence of surfuric acid electrolyte. Moreover, under such conditions antimony from the positive grids can migrate to the negative plates, "poisoning" them and causing increased cell selfdischarge and higher levels of water loss during recharging. Much effort has been directed, therefore, to overcoming the corrosion/poisoning effect of antimony in lead alloys.

One basic approach involves the addition of other metals to the basic antimony-lead alloy which reduces the susceptability of the alloy to corrosion. Such metals include, in various amounts, silver, U.S. Pat. 2,333,072 to L. Lighton, arsenic, U.S. Pat. 2,678,341 to H. Stoertz, silver and arsenic, U.S. Pat. 2,678,340 to H. Stoertz, and tin, U.S. Pat. 2,821,565 to J. Lander et al. Another approach has been to eliminate antimony altogether, and various antimony-free lead alloys are known, e.g., various silver-arsenic-tin-lead alloys, U.S. Pat. 2,820,079 to H. Zahn, aluminum-calcium-lead alloys, U.S. Pat. 3,920,473 to R. Sims, silver-tin-telurium-arsenic-lead alloys, U.S. Pat. 4,092,462 to H. Giess et al., and zinc-tin-lead alloys, U.S. Pat. 4,035,556 to J.

Duddy et al.

Recently, renewed attention has been focused on lead alloys in conjunction with improving low maintenance and maintenance free lead-acid storage batteries. Lead-acid batteries evolve oxygen and hydrogen, with concommitant water loss, during charging of the battery. If they are to be maintenance free; obviously, the water loss from gas evolution during charging must be minimized. It is well known that water loss may be minimized by increasing the hydrogen overpotential of the negative half-cell, which itself is significantly affected by the alloy composition of the negative grid. The hydrogen overpotential of antimony is low. Thus, the problem of excessive water loss, as well as the corrosion/poisoning effect discussed above, has motivated- workers in the art to develop low antimony and antimony free lead alloys.

Examples of low antimony alloys include the copper-arsenic-tin-antimony-lead alloys disclosed in U.S. Pat. 4,376,093 to R. Prengaman. Many antimony-free alloys also are known, including calcium-lead and calcium-tin-lead alloys, as disclosed in U.S. Pat. 4,401,730 to J. Szymborski et al.

Notwithstanding the discussion above focusing on electrochemical compatibility, the castability and mechanical properties of proposed lead alloys must not be overlooked if they are to be used successfully in lead-acid batteries. For example, in U.S. Pat. 4,207,097 to S. Fukuda et al., issued June 10, 1980, the presence of antimony was noted as a cause of increased water loss.

The inventors therein went on to state: "Pb-Sn-As alloy has been proposed which has the advantages of possessing fairly good mechanical properties, ensuring inhibited self-discharge when used for batteries and having a prolonged over-discharge cycle life involving deep discharge. Nevertheless, it has been found that when the alloy is cast into a grid, cracks are liable to develop in the grid during the casting process. The grid will then be unable to hold the active material effectively and will have a lower current collecting ability.

* * * When containing 0.1% or more of As, the Pb-Sn-As alloys are susceptible to cracking.

Col. 1, Ins 48-57, col. 4, Ins 62-64. It was further disclosed therein that the addition of aluminum or copper inhibited the cracking effect, with the resulting alloys comprising 0.01 to 0.1 wt% aluminum or copper, 0.1 to 3.0 wt% of tin, 0.1 to 0.3 wt% arsenic, and the balance lead.

Arsenic-tin-lead alloys. containing 0.1-0.3% arsenic, 0.3-3.0% tin and the balance lead have been reported in 95 CHEM. ABSTRACTS 83699u-v (1981). That reference also discloses that grids were made of those alloys, but that expensive treatment after casting was required, i.e., heat treatment and rolling.

A current trend in lead-acid battery design is to provide specialized alloys for the positive and negative grids. A particularly advantageous configuration for sealed, maintenance free, recombinant lead-acid batteries using that approach is disclosed in Szymborski '730. As disclosed therein, a calcium-tin-lead alloy may be used to form the negative grids. Such alloys, while providing good results in the negative grid are not necessarily suitable for use in other LAB components. During welding, as is typical in forming the straps and/or intercell connectors, a significant amount of calcium in the calcium-tin-lead alloys is oxidized, thereby hindering the creation of a smooth weld.

Accordingly, a different alloy preferably is considered for use in the intercell connectors and straps, e.g., a low antimony alloy. Such alloys are readily castable into LAB components having excellent mechanical properties. Despite the shortcomings of antimony in lead alloys noted above, the risk of corrosion/poisoning from antimony in straps is not great in recombinant batteries. The absolute and relative surface areas of straps, as compared to the grids, is small.

Moreover, there is substantially no free electrolyte in recombinant batteries. The major portion of the electrolyte, i.e., approximately 70%, is absorbed between the plates in highly absorbent microfine glass fiber separator material. Thus, straps in a recombinant battery are in less intimate contact with electrolyte, and antimony migration from the straps is more difficult.

A low antimony lead alloy was evaluated in a battery constructed generally according to the disclosure of Szymborski '730. The strap alloy comprised about 0.1 wt% arsenic, about 0.4 wt.% tin, about 3.0 wt% antimony, and the balance lead. The negative grid alloy nominally comprised from about 0.1 to about 0.15 wt% calcium, from about 0.1 to about 0.4 wt% tin, and the balance lead. The positive grid material nominally comprised about 0.025 wt% selenium, about 0.01 wt% silver, about 0.12 wt% aresenic, about 0.4 wt% tin, about 1.5 wt% antimony, and the balance lead. From the standpoint of the recognized problems of corrosion/poisoning and overgassing, this low arsenic-tin-antimony-content lead alloy performed well.Unexpectedly, however, it was observed that corrosion developed at the interface of the negative grid lugs and negative straps and soon spread through the negative grid lugs and negative straps causing battery failure. Moreover, the corrosion was nonuniform, resulting in earlier and less predictable failure. This corrosion is particularly surprising since it is not observed in wet batteries combining the same alloys.

OBJECTS OF THE INVENTION Accordingly, it is an object of the subject invention to provide an alloy which is electrochemi cally compatible with, and in particular, is less susceptable to corrosion in a lead-acid battery. A related and more specific object is to provide such an alloy which is electrochemically compatible with, and in particular, is less susceptible to corrosion in a sealed, maintenance free, recombinant lead-acid battery wherein the negative grids are composed of a lead alloy comprising calcium.

A further object of the subject invention is to provide an alloy which can be cast easily without subsequent treatment into LAB components which have sufficiently durable mechanical properties such that they can withstand the rigors of modern assembly techniques and battery service conditions.

Another object is to provide LAB components which are electrochemically compatible with, and in particular, are less susceptible to corrosion in a lead-acid battery. A related and more specific object is to provide LAB components which are electrochemically compatible with, and in particular, are less susceptible to corrosion in a sealed, maintenance-free, recombinant leadacid battery wherein the negative grids are composed of a lead alloy comprising calcium.

A further object of the subject invention is to provide LAB components which are easily cast without subsequent treatment and have sufficiently durable mechanical properties such that they can withstand the rigors of modern assembly techniques and battery service conditions.

An additional object of the subject invention is to provide a lead-acid battery comprising LAB components which are electrochemically compatible, and in particular, are less susceptible to corrosion. A related and more specific object is to provide sealed, maintenance-free, recombinant lead-acid batteries comprising such LAB components.

Yet another object is to provide lead-acid batteries comprising LAB components which are easily cast without subsequent treatment and have sufficiently durable mechanical properties such that they can withstand the rigors of modern assembly techniques and battery service conditions. A related and more specific object is to provide sealed, maintenance-free, recombinant lead-acid batteries comprising such LAB components.

Other objects and advantages of the present invention will be apparent to those skilled in the art upon reading the following description of the invention.

SUMMARY OF THE INVENTION The subject invention is predicated on the discovery that, for reasons presently unclear, when lead alloys comprising calcium are used in negative grids, the presence of any alloying amounts of antimony in the negative straps will cause undesirable corrosion of those LAB components in sealed, recombinant lead-acid batteries.Notwithstanding the teaching of Fukuda '097, wherein it was disclosed that arsenic-tin-lead alloys containing more than 0.1 wt% arsenic could not be cast into relatively thin grids without unacceptable cracking, the subject invention also evolves from the unexpected discovery that certain arsenic-tin-lead alloys containing more than 0.1 wt% arsenic may be cast successfully into relatively thicker LAB components (and, consequently, more susceptible to cracking), such as straps, without cracking and without subsequent treatment and that these novel alloys are less susceptible to corrosion when used in conjunction with negative grids made of lead alloys comprising calcium.

Accordingly, the subject invention is directed to a lead alloy comprising from about 0.3 to about 0.8 wt% arsenic, from about 1.5 to about 3.0 wt% tin, and the balance lead. A preferred embodiment of the subject invention is directed to a lead alloy comprising about 0.5 wt% arsenic, about 2.25 wt% tin, and the balance lead.

The present invention also is directed to a lead-acid battery comprising a container having a sealed cover, the interior of which is divided into a plurality of cells; electrode stacks disposed within each cell, which electrode stacks comprise a plurality of alternating positive and negative plates comprising grids having an integral lug on their upper end and supporting active material, separators between each adjacent plate pair, and a positive and a negative strap, wherein the positive and negative plates are connected electrically across the grid lugs, respectively, by the positive and negative straps; intercell connectors electrically connecting adjacent electrode stacks; a positive and a negative element post electrically connected, respectively, to the positive strap of one terminal cell electrode stack and the negative strap of the other terminal cell electrode stack; and a positive and a negative terminal electrically connected, respectively, to the positive and negative element posts; wherein at least one of the battery components selected from the group consisting of the grids, straps, intercell connectors, element posts, and terminals is composed of the novel alloy of the subject invention.

Finally, this invention also is directed to individual battery components, including, but not limited to grids, straps, intercell connectors, element posts, bushings, terminals, and the parts from which they may be formed during battery assembly which are composed of the novel alloy of the subject invention.

While the subject invention will be described further primarily by reference to specific embodiments thereof, it is not intended to be limited thereto. Other embodiments and modifications will be apparent to the worker in the art.

BRIEF DESCRIPTION OF THE DRA WINGS Figure 1 is a perspective view of a preferred embodiment of a strap/intercell connector of the subject invention illustrating its general configuration as successfully cast in Example 2.

Figure 2 is a perspective view of a strap/element post of the subject invention illustrating its general configuration as successfully cast in Example 2.

Figures 3-5 are photomicrographs, taken at 100 power, of the novel alloys and conventional alloy compared in Example 3 and demonstrate the improved grain structure of the novel alloys.

DETAILED DESCRIPTION OF THE INVENTION The novel alloy of the subject invention comprises from about 0.3 to about 0.8 wt% arsenic, from about 1.5 to about 3.0 wt% tin, and the balance lead, preferably about 0.5 wt% arsenic, about 2.25 wt% tin, and the balance lead. While it is very difficult to separate the effects of tin and arsenic on the properties of lead and the underlying theory has not been fully elucidated, general comments may be made. Tin is electrochemically compatible in a lead-acid system, yet contributes good castability and mechanical properties to lead. Below about 1.5 wt% tin, it would be expected that the novel alloys would be unacceptably soft, while more than about 3.0 wt% of this relatively expensive component would not be expected to contribute benefits commensurate with the increased cost.The presence of arsenic also imparts improved mechanical properties, and serves to refine the grain size of the novel alloy, thereby ensuring that corrosion, if not eliminated altogether, will be more uniform and predictable. It would be expected that arsenic levels below about 0.3 wt% would not impart adequate strength, while levels above about 0.8 wt% would render the novel alloy unacceptably brittle.

The alloy of the subject invention preferably is made from corroding grade, primary or secondary lead, i.e., lead meeting ASTM standard B29-55. Accordingly, it contains at least 99.93 wt% lead and may contain various trace metals such as silver, bismuth, copper, iron, nickel tellurium, zinc, cadmium, and antimony. Such lead is widely available from a number of commercial sources. Other grades of lead may be used, however, provided care is taken in ensuring that the presence of trace metals therein does not interfere with the beneficial properties imparted by the specified concentrations of tin and arsenic. Similarly, metallic tin and arsenic are commercially available, as are tin-lead and arsenic-lead master alloys, and may be used in the novel alloy of the subject invention. Preferably, if used, the metallic tin and arsenic is at least about 99.9% pure.As in selecting lead sources, whether using arsenic and tin as metals or in master alloy, care should be taken to ensure that the presence of trace metals therein is not incompatible with the novel alloy.

The novel alloy may be prepared by conventional methods of alloying lead well known to those skilled in the art, e.g., as disclosed in 12 KIRK-OTHMER ENCYCLOPEDIA OF CHEMICAL TECHNOLOGY 255-56 (J. Wiley & Sons, Inc., New York, NY 1967). In general, such methods include adding commercially available arsenic, tin, lead-arsenic master alloy, or lead-tin master alloy, as needed and desired, to molten lead. The molten alloy is heated to a temperature sufficiently high to ensure homogeneous alloying, generally from about 720C to about 940OF, with or without stirring.

The molten alloy may be cast into suitable molds to form LAB components as they would be present in the finished battery, or parts from which such LAB components may be formed by additional procedures during battery assembly, or it may be cast into pigs for subsequent remelting and casting. As used herein, however, for the sake of convenience, it shall be undestood that a reference to LAB components collectively or individually, unless the context clearly indicates only one or the other is intended, shall include not only the component as it is present in a finished battery, but also such assembly parts. Moreover, as Example 2 illustrates, a single casting process may yield both a finished component and an assembly part for another component. It also is well known that LAB assembly parts may be welded during assembly with the aid of welding rods.Accordingly, the novel alloys may be cast into such welding rods as well.

Preferably, when casting the novel alloy into LAB components or assembly parts, care should be taken to prevent excessive molten metal temperatures since this may accelerate dross generation and elemental loss. Conventional casting methods may be used and are well known to the worker in the art. Further treatment, such as heat treatment or rolling, is not needed, although such treatment may be used if desired.

As the circumstances surrounding the subject discovery would suggest, preferred embodiments are directed to LAB components, such as battery straps, composed of the novel alloy for use in sealed, maintenance-free, recombinant lead-acid batteries comprising negative grids composed of a lead alloy comprising calcium. Such embodiments are particularly preferred also because the selective strap and grid lug corrosion caused by the interaction of antimony in the negative straps with calcium in the negative grid lugs is exacerbated when the temperature rises above the usual ambient temperatures. For a number of reasons, during recharging the temperature of negative straps in recombinant batteries is significantly higher than in wet batteries.

Nevertheless, the properties of the novel alloy of the subject invention are such that in general it is advantageously adaptable for use in other LAB components and in other types of batteries.

The general construction of lead-acid batteries, as partially described hereinabove, is well known and forms no part of the subject invention. Likewise, LAB components per se are well known, as are their specific configurations and fabrication methods. In fact, a wide variety of configurations for LAB components are Inown, e.g., as disclosed in U.S. Pat. to W.

Kump et al. (Serial No. 770,946 filed August 30, 1985) (element posts, bushings, terminals), and U.S. Pat. 4,406,057 to T. Oswald et al. (element stacks) (see also application of J. Klang et al., Serial No, 352,924, filed Feb. 26, 1982, referred to therein). The particular configuration of a lead-acid battery and of its LAB components, as is well known, will vary among various battery types, such as float versus deep-cycle, wet versus recombinant, and maintenance free or low maintenance, according to the particular performance characteristics which are to be optimized.

While generally, the novel alloy of the subject invention may be used in the wide variety of conventional LAB components and conventional batteries, it is understood that this is not a claim to general superiority in every application. For example, while it is believed the novel alloy may be used to form grids, at present the cost of tin is sufficiently high that its use in grids may be discouraged for economic reasons. Moreover, a variety of alloys are known to be useful and, for mechanical or electrochemical reasons, may be preferred in particular LAB components used in batteries having specialized performance characteristics. Indeed, the trend is toward providing a different lead alloy for one or more of the LAB components in a battery. Accordingly, a novel LAB component of the subject invention may be used in combination with LAB components of other alloys.The grid alloy may be selected, for example, to enhance certain performance characteristics, while utilizing the novel alloy in the straps, even while using yet another alloy, perhaps more durable, in the bushings and terminals. Other factors, such as assembly methods, may influence the choice of alloys. For example, if the straps and intercell connectors are to be integrally formed, choosing the novel alloy for the straps would dictate its use in the intercell connectors as well. In light of the disclosure herein, the worker in the art can be guided by well known principles in utilizing the novel alloy to best advantage.

A particularly preferred embodiment, however, is directed to a sealed, maintenance-free, recombinant lead-acid battery constructed generally in accordance with the disclosure of Szymborski '079. In this preferred embodiment the positive grid alloy is a low antimony lead alloy comprising from about 0.008 to about 0.012 wt% silver, from about 0.023 to about 0.04 wt% selenium, from about 0.08 to about 0.16 wt% arsenic, from about 0.30 to about 0.55, preferably about 0.45 wt% tin, from about 1.2 to about 1,5, preferably about 1.5 wt% antimony, and the balance lead. The negative grid alloy is a calcium-tin-lead alloy comprising from about 0.06 to about 0.2, preferably about 0.15 wt% calcium, from about 0.1 to about 0.5, preferably about 0.2 to about 0.3 wt% tin, and the balance lead.The bushings and terminals are composed of alloy comprising from about 0.08 to about 0.16, preferably about 0.12 wt% arsenic, from about 0.2 to about 0.3, preferably about 0.25 wt% tin, from about 4.5 to about 4.8, preferably about 4.65 wtGó antimony, and the balance lead.

In accordance with the subject invention, the straps are composed of an arsenic-tin-lead alloy comprising from about 0.3 to about 0.8, preferably about 0.5 with arsenic, from about 1.5 to about 3.0, preferably about 2.25 wt% tin, and the balance lead. The straps may be formed by burning, but preferably are formed by cast-welding, i.e., inserting the grid lugs into the molten alloy as the strap is cast. Further treatment after casting is not necessary. The intercell connectors and element posts are formed as integral parts of the straps, and thus are composed of the novel alloys as well. It has been found that the straps, intercell connectors, and element posts thus formed of the novel alloy exhibit excellent mechanical properties during assembly and in battery service.Moreover, while not compromising the overall performance of the battery in any significant way, they possess the improved corrosion resistance properties of the novel alloys.

The invention is described further by reference to the following examples. They are not intended to limit the scope of the invention; rather, they are presented merely to facilitate the practice of the invention by those of ordinary skill in the art and to further disclose the inventors best mode of doing so.

Example 1 Various lead based alloys were cast as ASTM tensile test specimens having a reduced size, central portion with a cross section of 0.5 x 0. 125 inch and a 2 inch gauge length. In essence, two novel alloys of the subject invention were compared to a conventional arsenic-tin-antimonylead alloy which had: been used with general success in battery straps, excepting the corrosion problems in conjunction with grid calcium noted above. The nominal compositions of the novel alloys (Specimens 1 and 2) were as follows: 0.3 wt% arsenic, 2.25 wt% tin, balance lead; 0.5 wt% arsenic, 2.25 wt% tin, balance lead. The nominal composition of the conventional alloy (Specimen 3) was 0.1 wt% arsenic, 0.4 wt% tin, 3.0 wt% antimony, balance lead. Actual compositions are set forth below in Table I.

An Instron tensile tester, Model No. 1123, manufactured by Instron Corp., 2500 Washington Street, Canton, Massachusetts 02021, was used to generate the typical stress versus strain diagram for the specimens, from which the 0.5% yield strength (YS), ultimate tensile strength (UTS), and strain-to-faiiure (STF) were calculated. Specimens were tested as cast, i.e., within one hour after casting, twenty-four hours after casting, and forty-eight hours after casting.

A Knoop Micro Hardness tester, Model No. M11-1600-1001 Micromet, manufactured by Adolph I. Buehler Inc., 2120 Greenwood Street, Evanston, Illinois 60204, was used to determine the hardness of the specimens. The measurement was made approximately four days after casting using a diamond pyramid tip under a twenty gram load.

The results of the tensile and hardness tests, as well as approximate freezing ranges, are set forth below in Table 1.

Purushothama Rao/AUT-8602/22795 TABLE I Specimen Composition Time Ys UTS STF Hardness Approximate (psi) (psi) (%) (96 hr) Freezing Range 1 (novel) 0.30 As, 2.53 Sn, Pb as cast 1520 3936 33 14 593-604 F (actual) 24 hr 1482 3990 40 48 hr 1653 4043 38 2 (novel) 0.58 As, 2.23 Sn, Pb as cast 1872 4576 26 15 600-592 F (actual) 24 hr 1797 4485 26 48 hr 1733 4416 24 3 (conventional) 0.1 As, 0.4 Sn, 3.0 Sb, Pb as cast 1776 5680 18 18 615-600 F (nominal) 24 hr 1867 5387 15 48 hr 2200 5556 15 As indicated by the results in Table I, the properties of the novel alloy compare favourably to the conventional alloy which has been used successfully, from a mechanical standpoint, in LAB components. It would be expected, therefore, that the novel alloy also would be used successfully in forming LAB components.

Example 2 Novel alloy having a nominal composition of 0.5 wt% arsenic, 2.25 wt% tin, and balance lead were cast into the battery straps, intercell connectors, and element posts, shown in Figs. 1 and 2, using a casting machine, Model No. MaCast On 320, manufactured by MAC Equipment Company, Inc., 2775 Meadow Brook Road, Benton Harbor, Michigan 49022. The machine utilizes a water cooled mold maintained from about 275 to about 380OF. The casting temperature was from about 725 to about 775OF. There was no treatment after casting.

As can be seen from Figs. 1 and 2, respectively, straps and intercell connectors and straps and element posts were cast as integral pieces. The strap/intercell connector 1 of Fig. 1 generally comprises a solid rectangular shaped strap portion 2, which in essence comprises the strap as present in the finished battery. Upstanding from the upper surface of the strap portion 2 and at one end is a tombstone-shaped intercell connector portion 3 from which the intercell connector in the finished battery is made. Grids (not shown) were inserted in an inverted position into the molten strap/intercell connector as it was being cast, i.e., grids were castwelded with the strap/intercell connector, and after completion of the casting process, the grids, when placed in the upright position, project downward from the lower surface of the strap portion 2.The approximate dimensions of the strap portion 2 were 0.25"x0.94"x 1.88". The approximate dimensions of the intercell connector portion 3 were 0.19"x0.94"x0.85".

The strap/element post 4 of Fig. 2, as shown therein, comprises a strap portion 5 from the upper surface of which projects an element post portion 6. As in Fig. 1, because they were cast-welded with the strap/element posts, grids (not shown) project downward from the lower surface of the strap portion 5. The external dimensions of the strap portion 5 are generally the same as those for the strap portion 2 of the strap/intercell connector shown in Fig. 1, excepting of course the generally triangular projection from which the element post portion 6 projects. The element post portion 6 is approximately 0.6" in diameter, being only slightly tapered, and is approximately 1.6" high.

The resulting strap/intercell connectors and strap/element posts showed no evidence of cracking, notwithstanding the disclosure of Fukuda '097 wherein it was reported that grids could not be cast from arsenic-tin-lead alloys containing more than 0.1 wt% arsenic without cracking.

Moreover, notwithstanding the disclosure of CHEM. ABSTRACTS, cited above, no subsequent treatment was needed to avoid cracking or otherwise improve the mechanical properties of the LAB components. This was particularly unexpected because the straps are much thicker, approximately 400% thicker, than the typical grid and cracking generally is exascerbated by increasing thickness.

Example 3 Photomicrographs of Specimens 1-3 of Example 1 were taken at 100 power. Those photomicrographs are reproduced, respectively, in Figs. 3-5. As shown therein, the novel alloy exhibits exceptionally fine microstructure, especially as compared to the conventional alloy, of which staps are known to corrode after being cast-welded to negative grids composed of lead alloys comprising calcium. Accordingly, while a significant tendency to corrode is not expected of the novel alloy because of the electrochemical compatability of tin, it is expected that any corrosion which occurs will be more uniform due to the highly refined grain structure of the novel alloy.

Claims (32)

1. A lead alloy comprising from about 0.3 to about 0.8 wt% arsenic, from about 1.5 to about 3.0 wt% tin, and the balance lead.

2. The alloy of claim 1, comprising 0.5 wt% arsenic, about 2.25 wt% tin, and the balance lead.

3. A lead-acid battery comprising a container having a cover, the interior of which is divided into a plurality of cells; electrode stacks disposed within each cell, which electrode stacks comprise a plurality of alternating positive and negative plates comprising grids having an integral lug on their upper end and supporting active material, separators between adjacent plate pairs, and a positive and a negative strap, wherein said positive and negative plates are connected electrically across said grid lugs, respectively, by said positive and negative straps; intercell connectors electrically connecting adjacent electrode stacks; a positive and a negative element post electrically connected, respectively, to the positive strap of one terminal cell electrode stack and the negative strap of the other terminal cell electrode stack; and a positive and a negative terminal electrically connected, respectively, to said positive and negative element posts; wherein at least one of the battery components selected from the group consisting of said grids, straps, intercell connectors, element posts, and terminals is composed of the lead alloy of claim 1.

4. The lead-acid battery of claim 3, wherein said alloy comprises about 0.5 wt% arsenic, about 2.25 wt% tin, the balance lead.

5. The lead-acid battery of claim 3, wherein said battery component is a grid.

6. The lead-acid battery of claim 3, wherein said battery component is a strap.

7. The lead-acid battery of claim 3, wherein said battery component is an intercell connector.

8. The lead-acid battery of claim 3, wherein said battery component is an element post.

9. The lead-acid battery of claim 3, wherein said battery component is a terminal.

10. The lead-acid battery of claim 3, wherein said battery comprises a positive and a negative bushing mounted in the container or cover wall and electrically connected, respectively, to said positive and negative element posts and terminals, said bushings, being composed of a lead alloy comprising from about 0.3 to about 0.8 wt% arsenic, from about 1.5 to about 3.0 wtWo tin, and the balance lead.

11. A lead-acid battery comprising a container having a cover, the interior of which is divided into a plurality of cells; electrode stacks disposed within each cell, which electrode stacks comprise a plurality of alternating positive and negative plates comprising grids having an integral lug on their upper end and supporting active material, separators between adjacent plate pairs, and a positive and a negative strap, wherein said positive and negative plates are connected electrically across said grid lugs, respectively, by said positive and negative straps; intercell connectors electrically connecting adjacent electrode stacks; a positive and a negative element post electrically connected, respectively, to the positive strap of one terminal cell electrode stack and the negative strap of the other terminal cell electrode stack; and a positive and a negative terminal electrically connected, respectively, to said positive and negative element posts; wherein said negative grids are composed of a lead alloy comprising calcium and said straps are composed of the lead alloy of claim 1.

12. The battery of claim 11 wherein said strap is composed of a lead alloy comprising about 0.5 wt% arsenic, about 2.25 wt% tin, and the balance lead.

13. The lead-acid battery of claim 11, wherein said intercell connectors are composed of a lead alloy comprising from about 0.3 to about 0.8 wt% arsenic, from about 1.5 to about 3.0 wt% tin, and the balance lead.

14. The lead-acid battery of claim 12, wherein said intercell connectors are composed of a lead alloy comprising from about 0.3 to about 0.8 wt% arsenic, from about 1.5 to about 3.0 wt% tin, and the balance lead.

15. The lead-acid battery of claim 13, wherein said intercell connectors are composed of a lead alloy comprising about 0.5 wt% arsenic, about 2.25 wt% tin, and the balance lead.

16. The lead-acid battery of claim 14, wherein said intercell connectors is composed of a lead alloy comprising from about 0.5 wt% arsenic, from about 2.25 wt% tin, and the balance lead.

17. The lead-acid battery of claim 11, wherein said battery is a sealed, maintenance-free, recombinant lead-acid battery.

18. The lead-acid battery of claim 12, wherein said battery is a sealed, maintenance-free, recombinant lead-acid battery.

19. The lead-acid battery of claim 13, wherein said battery is a sealed, maintenance-free, recombinant lead-acid battery.

20. The lead-acid battery of claim 16, wherein said battery is a sealed, maintenance-free, recombinant lead-acid battery.

21. A component for a lead-acid battery selected from the group consisting of grids, straps, intercell connectors, element posts, bushings and terminals, wherein said component is composed of the lead alloy of claim 1.

22. The component of claim 21 wherein said alloy comprises about 0.5 wt% arsenic, about 2.25 wt% tin, and the balance lead.

23. The component of claim 21, wherein said component is a grid.

24. The component of claim 21, wherein said component is a strap.

25. The component of claim 22, wherein said component is a strap.

26. The component of claim 21, wherein said component is an intercell connector.

27. The component of claim 22, wherein said component is an intercell connector.

28. The component of claim 21, wherein said component is an element post.

29. The component of claim 21, wherein said component is a bushing.

30. The component of claim 21, wherein said component is a terminal.

31. A welding rod composed of the lead alloy of claim 1.

32. The lead alloy substantially as shown and described in the foregoing application.