JPH11250894A - Lead-acid battery, and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve corrosion resistance of a lead-acid battery group weld part comprising grid edge parts and a strap of different alloy compositions in which both are welded with each other by preliminarily avoiding interganular corrosion generated because of a granular structure. SOLUTION: A grid lug part 2 close to a junction boundary of the grid lug part 2 with a strap 3 is formed to have a fibrous structure 1 in a perpendicular direction in a thickness direction of it and in a length direction of the lug part 2. For this purpose, a process of obtaining a multi-layer structure part comprising the fibrous structure 1 coated with low fusing point alloy 4, a process of bringing a molten pool of alloy to be the strap 3 in contact with the multi-layer structure lug part, and fusing low fusing point alloy 4 while restricting fusing and recrystallization of the part of the fibrous structure 1 to weld and integrate the strap 3 and the multi-layer structure lug part with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a lead storage battery and a method for manufacturing the same.

[0002]

2. Description of the Related Art Lead-acid batteries for automobiles have a Pb-S
The mainstream is a hybrid type using a lattice of a b-based alloy and a lattice of a Pb-Ca-based alloy for the negative electrode, or a calcium battery using a lattice of a Pb-Ca-based alloy for both electrodes. ing. Currently, Pb-Sb-based alloys or Pb-Sn-based alloys are mainly used for straps for bundling the lugs of the same polarity electrode plates in the battery electrode group. Welding (hereinafter abbreviated as “group welding” when bundling the grid body ears of the same polarity electrode plates in the battery electrode group). Also, the vicinity of the joint interface between the grid body ears and the strap is abbreviated as “group welded part”. ), A method called the cast-on-strap method in which the grid body ears are immersed in a molten strap alloy having the composition described above and cast in place, or placed near the grid body ears and lead is melted with a burner. The burner welding method for welding is mainly used. In a lead-acid battery, when this group weld once comes into contact with the electrolyte and then is exposed from the electrolyte, the sulfuric acid concentration at that part increases, and a local battery is formed between the grid body ears and the strap, which leads to electrochemical formation. Reaction promotes intergranular corrosion. This is due to the fact that the lattice member ears and the straps usually have different alloy compositions. For this reason, there are problems such as the ear part being cut off, an electric spark being generated due to the poor joint state, reacting with the gas in the battery case, causing an explosion accident, and starting failure.

When the grid is an expanded grid, it is common to use a rolled sheet as the grid material, and the metal structure is a fibrous structure. When performing group welding by the above-described method, a certain amount of heat must be applied in order to perform welding so as to obtain a good metallurgical connection between the lattice member ears and the strap. Conventionally, this calorific value melts the ears of the lattice body.
Recrystallization causes the fibrous structure to be lost, resulting in a granular structure as shown in FIG. In this granular structure, the corrosion proceeds along the grain boundaries of the particles, that is, so-called intergranular corrosion is likely to progress, and the corrosion resistance is inferior to that of the fibrous structure. Conventionally,
As means for improving the corrosion resistance of the lattice member ears which causes such a problem, means for coating a group welded portion with a Pb-Sn alloy as shown in FIG. 3 (Japanese Patent Application Laid-Open No. 8-236101) has been proposed. .

[0004]

In the above-described means for improving the corrosion resistance, the Pb-Sn-based alloy may not be sufficiently coated on the group-welded portion in some cases. Therefore, if the ears of the lattice have a granular structure, once the electrolyte enters the grain boundaries, grain boundary corrosion proceeds. The problem to be solved by the present invention is
Prevent intergranular corrosion caused by the granular structure,
The purpose is to improve the corrosion resistance of the group welds.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a lead-acid battery according to the present invention, in which the lattice member ears 2 and the strap 3 have different alloy compositions and are welded to each other, is provided. The lattice body ear portion near the joint interface between the strap 2 and the strap 3 has a fibrous structure 1 along the ear length direction. The fibrous structure 1 is, for example, a metal structure shown in FIG. 1 which is found in a rolled metal, and may be called a rolled structure. If the lattice member ears 2 and the straps 3 have different alloy compositions, when the electrolytic solution comes into contact with the group welds, a local battery is formed there, and corrosion proceeds there. When the potential difference between the lattice member ears 2 and the strap 3 is small, the rate of progress of corrosion is also low, and is not so much a problem. However, when the potential difference is large, it is a problem. The difference in the alloy composition of the extent that the problem is not considered,
For example, a Pb-0.1Ca-0.5Sn alloy and a Pb-
Difference from 0.8Ca-0.5Sn alloy, or Pb-
1.65Sb-0.02Se alloy and Pb-2.7Sb-
This is the difference from the 0.02Se alloy. Further, the difference in the alloy composition that is regarded as a problem is, for example, Pb-0.1
Ca-0.5Sn alloy and Pb-2.7Sb-0.02
This is the difference from the Se alloy.

In the method for manufacturing a lead-acid battery according to the present invention which realizes the above-described structure, the lattice body ears 2 have a fibrous structure 1 extending along the length of the ears, and the surface thereof has a melting point higher than that of the lattice body ears 2. A step of obtaining a multi-layered lug covered with a low lead alloy (hereinafter abbreviated as low-melting alloy 4); and bringing the molten alloy serving as the strap 3 into contact with the multi-layered lug to melt the fibrous structure 1 A step of melting the lead alloy having a low melting point while suppressing recrystallization, and welding and integrating the strap 3 and the multi-layer structure ear portion; The multilayer structure refers to a structure including two or more layers. A specific example of the low melting point alloy 4 is as follows: Sn is 20 to 30 wt% (melting point: 255 to 280 ° C.)
Or, it is a lead alloy containing 75 to 80 wt% (melting point: 205 to 210 ° C.). Generally 3wt% by weight for strap alloy
% Pb-Sb alloy containing about Sb is used. Since the melting point of this alloy is about 325 ° C., the molten metal supply temperature during group welding needs to be higher. At this time, if the melting point of the low melting point alloy 4 disposed on the surface of the ear portion is too low, the layer of the low melting point alloy 4 on the surface is easily melted and flow easily at the time of group welding. It is difficult to fulfill the role of obtaining a metallurgical bond between the alloy and the strap alloy. Therefore, the composition of the low melting point alloy 4 disposed on the surface of the ear portion is 2% by the Sn content ratio in the above Pb-Sn alloy.
It is preferably about 0 to 30 wt% or about 75 to 80 wt%.

In order to maintain the fibrous structure 1 of the lattice member ears 2 after group welding, the amount of heat given to the lattice member ears 2 during group welding should be such that the portion does not melt and recrystallize. It needs to be suppressed. Therefore, by arranging a low melting point alloy 4 on the lug surface 2 such that sufficient metallurgical bonding can be obtained even when group welding is performed at a low temperature on the lug surface 2, the internal fibrous structure can be maintained. As a result, a group weld having excellent corrosion resistance can be obtained. Even if there is a difference in the alloy composition which is regarded as a problem by maintaining the fibrous structure in the group weld even after the group weld, the corrosion resistance is improved because the electrolyte does not easily enter the inside of the group weld, even if there is a problem with the alloy composition. You will not be seen. That is, the allowable range of the combination of the lattice body and the alloy of the strap that is not regarded as a problem is widened. For this reason, by applying the configuration of the present invention, intergranular corrosion caused by the granular structure as shown in FIG. 2 can be avoided beforehand, and the corrosion resistance of the group weld can be improved.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS 8 mm thick Pb-0.1Ca-
Slab of 0.5Sn alloy (melting point approx.
m of Pb-20Sn alloy (melting point about 280 ° C) from both sides, and 0.8m by cold rolling with a roller
m to obtain a rolled sheet having a Pb-20Sn foil of about 100 μm on the surface. The sheet is press-punched in the shape of a lattice-shaped ear part 2, and the ear part is formed of D-size Pb.
It welded to the negative electrode plate of the expanded lattice of -0.8Ca-0.5Sn by arc welding. The group welding of the negative electrode plates was performed by an overflow type cast-on machine by a cast-on method (cast-in). The alloy composition of the strap body is Pb-2.7Sb-0.02Se (melting point about 325 ° C),
The molten metal supply temperature is 340 ° C., the mold temperature is 140 ° C., and the group is welded to the negative electrode plate to maintain the fibrous structure of the lug of the negative electrode plate. I got The negative electrode plate and D-sized Pb-1.65Sb-0.0
A known positive electrode plate using a cast lattice of 2Se (the same composition is also used for the lugs), and in combination with a strap of Pb-2.75Sb-0.02Se alloy, four positive electrode plates and five negative electrode plates A group was formed, and this was placed in a battery case made of polypropylene. The separator was a bag-shaped separator made of polyethylene, in which a negative electrode plate was housed, and a glass fiber plate-like buffer was inserted between the separator and the positive electrode plate. A dilute sulfuric acid solution having a specific gravity of 1.225 was injected into the battery container, and the solution was heated at 40 ° C., 1
After carrying out formation by supplying electricity for 8 hours at 8A, the specific gravity was adjusted to adjust the final specific gravity to 1.280. Further, the electrolyte surface was adjusted to 2 to 3 mm from the lower surface of the strap, and the group weld was exposed from the electrolyte. Thereafter, the opening of the battery case was sealed with a lid to obtain the battery of the present invention.

In this embodiment, the configuration of the group welded portion according to the present invention is applied to only the negative electrode, but the present invention can be applied to only the positive electrode or both the positive electrode and the negative electrode. In the present example, the lattice body ear 2 is
Although the low-melting-point alloy has a two-layer structure on the surface of the ear, the low-melting-point alloy may have a structure of two or more layers having different compositions.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A lead storage battery (battery A) to which the manufacturing method described in the embodiment of the present invention is applied, and a lead storage battery (battery B) to which the manufacturing method described in an example of JP-A-8-236101 is applied. And were compared. At this time, the electrolyte surfaces of the batteries A and B were kept at a position of 2 to 3 mm from the lower surface of the strap. When the electrolytic solution is injected into the battery case described above, the group weld portion is once in contact with the electrolytic solution, and thereafter, the group weld portion is exposed from the electrolytic solution. Battery B was formed by adjusting the heat of the burner such that the lattice-shaped ear portion had a granular structure and the entire welded portion between the lattice and the strap was covered with Pb-50Sn (melting point: about 220 ° C.). A battery was fabricated under the same conditions as Battery A except for the group welding conditions. FIG. 3 is a schematic view of a group welded portion of the battery B.

Batteries A and B were placed in an 80 ° C. water bath at 2.3
It was subjected to a corrosion resistance test in which one cycle of discharging at 200 A for 2 seconds after applying a constant voltage overcharge of 110 h at V was one cycle (n = 12). After 12 cycles of this test,
In battery B, nine out of twelve batteries were cut due to corrosion in the group weld due to deterioration of the electrode plate, and discharge was impossible.
However, in the battery A according to the present invention, no breakage due to corrosion was observed in the group weld, and all the batteries could be discharged even after 12 cycles.

[0012]

According to the present invention, intergranular corrosion caused by a granular structure can be avoided beforehand, and the corrosion resistance of the group weld can be improved.

[Brief description of the drawings]

FIG. 1 is a view showing a group welded portion according to the present invention.

FIG. 2 is a diagram showing a conventional group weld.

FIG. 3 is a diagram showing a conventional group weld.

[Explanation of symbols]

 1. 1. Fibrous tissue Lattice body ears 3. Strap 4. Low melting point alloy

Claims (3)

[Claims] 1. A lead-acid battery in which a lattice body ear part and a strap have different alloy compositions and are welded to each other, wherein the lattice body ear part near a joint interface between the lattice body ear part and the strap is an ear. A lead-acid battery having a fibrous structure along a length direction. 2. A method for manufacturing a lead-acid battery, wherein a lattice body ear part and a strap have different alloy compositions and have a step of welding them, wherein the lattice body ear part removes a fibrous structure along a length direction of the ear part. A step of obtaining a multi-layered lug whose surface is covered with a lead alloy having a lower melting point than the latticed lug; and bringing the multi-layered lug into contact with the molten alloy to be the strap, A method for producing a lead storage battery, comprising a step of melting the low-melting-point lead alloy while suppressing melting and recrystallization, and welding and integrating the strap and the multilayer structure ear. 3. A lead alloy having a lower melting point than the lattice member ears,
3. The method according to claim 2, wherein the lead alloy is a lead alloy containing 20 to 30 wt% or 75 to 80 wt% of n.