JPH04358034A - Lead-base alloy for storage battery - Google Patents

Abstract

PURPOSE:To obtain a storage battery having long service life by constituting a lead-base alloy of specific mass percentages of Ca, Sn, Al, Bi, and the balance Pb. CONSTITUTION:The lead-base alloy for storage battery has a composition consisting of, by mass, 0.01-0.50% Ca, 0.05-5.0% Sn, 0.001-0.20% Al, 0.001-1.0% Bi, and the balance Pb. By this method, the occurrence of voids and cavities can be remarkably inhibited even if this alloy is applied to a plate substrate for maintenance free storage battery.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention relates to the improvement of lead-based alloys for storage batteries, and in particular to the improvement of lead-based alloys for storage batteries, and in particular for forming substrates for electrode plates of storage batteries by applying pressure to the molten alloy and forcing the molten metal into a mold. It is an object of the present invention to provide a lead-based alloy having performance suitable for pressurized manufacturing methods (die-casting, rotating drum continuous casting).

0002

[Prior Art] Conventionally, this type of lead-based alloy has mainly focused on mechanical strength, so Sb is 4.5 to 8.0.
Lead-based alloys containing a large amount, such as % by mass, are known.

However, when this alloy is applied to the electrode plate substrate of a storage battery, the above-mentioned Sb causes self-discharge of the battery, which not only reduces the capacity but also causes severe discharge in the fully charged state and overcharged state. This caused a cushing phenomenon and required water replenishment. Replenishing this water had a completely opposite effect on the electrode plate substrates of maintenance-free batteries, which do not require water replenishment and are currently the mainstream of storage batteries.

Therefore, as a lead-based alloy containing no Sb, for example, Ca
0.01-0.5% by mass, Sn2.05-5.0% by mass
, 0.005 to 0.15% by mass of Al, and the balance Pb. A lead-based alloy for storage batteries has been proposed.

[0005] However, when a substrate is made using this alloy, the molten metal of the alloy is forcibly injected into a rotating mold to continuously form the substrate, and the solidified crystal structure of the obtained substrate is examined using a microscope. As a result, a diameter of approximately 0.0 mm was found within the coagulated tissue.
It was observed that many fine voids with a diameter of 5 mm or less were almost spherical. Furthermore, it was confirmed that in the alloy composition within the above range, these voids were generated not only in one part but throughout the alloy.

As a method for quantitatively understanding the amount of voids, we conducted a total gas analysis of an alloy sample containing voids. As a result, we found that the total gas amount of an alloy sample containing voids was determined by the fact that there were no voids at all. The amount was about 2 to 3 times the total amount of gas in the alloy sample, which was not observed.

The total amount of gas was measured by a high-temperature vacuum method in which the gas contained in the sample was released by melting the sample and the amount of gas was measured. This method calculates the amount of gas contained in a sample from the difference between the degree of vacuum in the exhaust pipe system before heating the sample and the degree of vacuum in the exhaust pipe system after heating.

[0008] When a lead-based alloy is cast by the pressurized method as described above, voids and cavities are likely to be formed within the alloy. The reason for this is that when the molten metal of the alloy is injected into the mold, significant turbulence occurs in the molten metal, and the solidified structure becomes a fine dentrite-like structure of crystal grains with short main axes and side branches of dendrites and broken morphology. Furthermore, the turbulent flow of the molten metal causes air to be entrained and gas to enter, resulting in the formation of voids and cavities.

[0009] These voids and cavities are distributed almost uniformly as if air is formed between the dentrite crystals when the total gas amount ratio is less than 1.90, but when the total gas amount ratio is less than 1.9
When it is 0 or more, spherical voids are scattered in the shape and the dentrite-like crystals are divided, resulting in a non-uniform solidified structure.

[0010] Furthermore, such a solidified structure causes deterioration of the creep characteristics and corrosion resistance of the alloy.

That is, the relationship between the total gas amount ratio and the creep strength ratio is expressed as shown in FIG. Further, the creep strength ratio is defined as shown in the following equation.

Creep strength ratio=C(G>1)/C(G=
0) However, C (G = 1) is the total gas amount ratio, C (G > 1) is the total gas amount ratio, and the creep strength of the material with G > 1 is the total When the gas amount ratio is less than 1.90, the creep strength ratio is approximately 1. In other words, the creep strength of a material with a total gas amount ratio G of 1<G<1.9 is approximately equal to the creep strength of a material with G=1, or if G exceeds 1.9, the creep strength ratio becomes greater than 1. . In other words, the creep strength of materials whose G (total gas amount ratio) exceeds 1.9 is G = 1.
This shows that the creep strength is smaller than the creep strength of the material. This low creep strength means that the material elongates,
Since the amount of deformation is large, it is necessary for the elongation deformation of the lead-based alloy material for storage batteries to be as small as possible, and therefore a total gas ratio of less than 1.90 is desired. there were.

[0013]

[Problems to be Solved by the Invention] As a result of intensive research in view of the current situation, the present invention has been developed to provide a storage battery with excellent mechanical strength without forming voids in the substrate even when the substrate is cast using a pressure method. This is a lead-based alloy developed.

[0014]

[Means for Solving the Problems] The present invention provides Ca0.01~
0.50% by mass, Sn0.05-5.0% by mass, Al0
．． This is a lead-based alloy for storage batteries consisting of 0.001 to 0.20% by mass, 0.001 to 1.0% by mass of Bi, and the balance Pb.

[0015]

[Function] The present invention adds Bi to the above-mentioned known lead-based alloy, and by adding Bi, the growth of dentrite crystals becomes faster than when no Bi is added, and as a result, the flow of the molten metal is improved. However, B
As the amount of i added increases, the value of the total gas amount ratio decreases and the creep characteristics also improve.

[0016]Then, the content of Bi is 0.001 to 1.0.
The reason why it is limited to % by mass is that if it is less than 0.001% by mass, the above effect will be extremely weak, and if it exceeds 1.0% by mass, the effect of the total gas ratio will not improve significantly.

In the present invention, is it possible to improve mechanical strength by adding Ca? The effect is weak and 0.50% by mass
This is because even if the casting temperature is exceeded, a good cast product cannot be obtained at a low casting temperature, and on the other hand, when the casting temperature is raised, oxidation occurs and the loss of Ca increases.

[0018] Also, the addition of Sn improves the flowability and mechanical strength of the alloy and further suppresses the generation of voids, which is why the amount added is limited to 0.05 to 5.0% by mass. If it is less than 0.05% by mass, the effect is weak, and if it exceeds 5.0% by mass, there is almost no improvement in the effect of suppressing void generation, and the corrosion resistance is poor due to the increase in the amount of Sn, which is preferable. do not have.

Furthermore, the addition of Al prevents the loss of Ca due to oxidation of the molten metal, reduces the strain rate dependence of tensile strength, and improves creep properties. The reason for limiting it to .50% by mass is
If it is less than 0.01% by mass, the effect is weak and 0.5
This is because if it exceeds 0% by mass, the effect of reducing the strain rate dependence described above will not be noticeable.

[0020]

[Example] A lead-based alloy of the present invention having the composition shown in Table 1 was obtained by adding Ca, Sn, Al and Bi to molten lead, respectively.
Molten metals of these alloys were press-fitted into molds to produce electrode plate substrates for storage batteries, and the quality of the substrates was determined by measuring the total gas amount ratio in the solidified structure.

[0021] In Table 1, a cold-rolled plate made of a lead-based alloy (standard alloy) containing no voids was prepared and compared with the lead-based alloy of the present invention.

[0022]

[Table 1]

As is clear from Table 1, according to the lead-based alloy for storage batteries of the present invention, by adding a specified amount of Bi, the total gas amount ratio is significantly lower than that of the comparative example lead-based alloy. We were able to reduce the value to less than 1.90. It was confirmed that this improved creep properties and corrosion resistance.

[0024]

Effects of the Invention As detailed above, the lead-based alloy for storage batteries of the present invention can be applied to the electrode plate substrates of maintenance-free storage batteries, and the generation of voids and cavities can be significantly suppressed, resulting in long-life storage batteries. It is very useful.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between creep strength ratio and total gas amount ratio.

Claims (1)

[Claims] Claim 1: 0.01 to 0.50% by mass of Ca, Sn
A lead-based alloy for storage batteries consisting of 0.05 to 5.0% by mass, 0.001 to 0.20% by mass of Al, 0.001 to 1.0% by mass of Bi, and the balance Pb.