JPH04137357A - Welding method of electrode plate group for lead storage battery - Google Patents

Abstract

PURPOSE:To obtain a strap of an excellent anticorrosion property and a high reliability by forming a covering layer of a lead-bismuth system alloy on the surface of the lug of each electrode plate, soaking and solidifying the lugs in a molten lead, and forming a weld between a starp and an electrode plate, an electrode pole, a strap, and the like. CONSTITUTION:In an electrode plate group welding method of a lead storage battery in a cast-on-strap method, covering layers 13 of a lead-bismuth alloy are formed on the surfaces of Jugs of electrode plates. And the lugs of the electrode plates are soaked and solidified in a molten lead. The lead-bismuth system alloy has a lower melting temperature lower than the lead alloy used for straps, electrode plate lugs, and the like, and the corrosion amount is less when it is placed at the positive electrode potential in a lead storage battery. Consequently, a corrosion along the covering layers 13 of the straps is eliminated, and straps of an excellent anticorrosion property and a high reliability can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing lead-acid batteries, and relates to an improvement in a method of welding electrode groups called the so-called cast-on-strap method.

Conventional technology and its problems Generally, as shown in Fig. 2, a lead-acid battery consists of an electrode plate group formed by alternately stacking a positive electrode plate 1, a separator 2, and a negative electrode plate 3.
It consists of straps 5, 5' for connecting the positive electrode plate lug 4 and negative electrode plate lug 4', respectively, and pole posts 6, 6' for taking out the current. Currently, there are two main methods of connecting ears of the same polarity to form a strap: burner welding and cast-on strapping.

An example of burner welding is a manual welding method.

This method is reliable but not suitable for mass production because the straps are formed manually by workers, and is mainly used for large lead-acid batteries and sealed lead-acid batteries for electric vehicles and stationary vehicles, which are produced in relatively small quantities. Used in the manufacturing process of storage batteries.

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On the other hand, the cast-on-strap method is a strap forming method that can be automated using a machine, and involves welding the strap and the pole plate lugs to each other and forming the strap and the pole pole at the same time. An example of a cast-on-strap procedure is shown below.

■Brushing (removal of dirt on the electrode plate surface) ■Cleaning with reducing solution (flux) (removal of oxides on the electrode plate lug surface) ■Breheating (removal of flux and preheating of the electrode plate lug) ■Mold (7) carving Injection of molten lead into the molten lead (2) The inverted electrode plate ear is immersed in molten lead to solidify, and a schematic diagram of the step (2) before immersion is shown in Figure 3.

Since the cast-on-strap method uses the heat of molten lead to melt the ears, the heat capacity tends to be insufficient to melt the large plates, so it is difficult to use for relatively small batteries. For example, it was only used in lead-acid batteries for automobiles. On the other hand, in sealed lead-acid batteries, because it is not possible to use a bell-antimony alloy for the grid or strap due to battery performance, a lead-calcium alloy or a lead-tin alloy with a low tin content is used. These alloys had high melting temperatures, and cast-on-strap methods lacked heat capacity and were difficult to weld.

In recent years, as demands for pollution-free and energy-saving technologies have increased, demand for electric vehicles has increased, and it has become necessary to mass-produce large lead-acid batteries. In addition, there is a strong demand for maintenance-free batteries for emergency power sources, household electrical equipment, etc., and demand for sealed lead-acid batteries is rapidly increasing. Since conventional manual welding methods cannot meet the demands of mass production, it has become essential to develop a cast-on-strap method for large lead-acid batteries and sealed lead-acid batteries.

As mentioned above, in the cast-on-strap method, the plate lugs are melted using only the heat of molten lead, so the larger the plate lugs become, and the higher the melting temperature of the plate lugs, the more difficult welding becomes. It's coming. Figure 4 shows the conventional cast-on-strap method for electric vehicles! 9 is a cross-sectional view of the strap of a storage battery, in which a blowhole 8 and a negative meniscus 9 are formed. Blowholes are formed when molten lead solidifies before the air that is drawn in when the plate is immersed, or the gas generated by the decomposition of the reducing solution (flux) used to clean the plate edges, is not removed. It is thought that this is to store it away. On the other hand, the negative meniscus is caused by the electrode plate lugs immersed in the molten ship solidifying before fully fusing with the molten lead.

During battery operation, such straps tend to allow sulfuric acid, which is an electrolyte, to enter the blowhole or the ear-strap joint, which can lead to corrosion and damage to the strap.

In order to improve the welding condition, a method has been proposed in which a coating layer of a low melting point alloy is applied to the surface of the plate lug before the lug is immersed in molten lead. This involves dividing the joint into two parts: the plate lug and the covering layer, and the covering layer and the strap.The plate lug and the strap are connected by firmly joining each part. .

As a low melting point alloy, for example, a Sn-40% circular alloy has very good bonding properties with the electrode plate lugs, and its melting temperature is about 18%.
Melts at 0℃! ! ! Molten lead solidifies because it is much lower than lead (the melting temperature of Pb-4%9 alloy is approximately 300°C).
Even when the strap is being formed, the area near the surface of the electrode plate edge coated with the CHI alloy coating remains in a molten state until the end. In this way, the plate lugs are kept in a molten state for a sufficient period of time to remove gas and melt the plate lugs, so that the bonded state of the plate lugs and straps is maintained in the finished strap, as shown in Figure 5. It becomes very good, there are no blowholes, and a positive meniscus 10 can be seen.

However, a new problem has arisen regarding the corrosion resistance of the one-yen alloy. FIG. 6 is a cross-sectional view of a strap after an overcharge test of a battery manufactured by the cast-on-strap method using a 5n-40% alloy for the coating layer of the electrode tab. It is believed that the following reaction proceeds in 5n-Pb alloy in sulfuric acid.

5n(S) -5n2++2e -0,141V(v
s, H2) (1) Sn+H,O→ SnO+2H" +28 -0.104V (2) S
r+ 24' + 2 H20→ SnO2+4H" +2e -0,094V (3
)PbSO, +2H20→ Pb0t +4H"+SO4"-+2e 1.69
0V (4) Compared to the potential generated by pbo2 (formula (4)), the potential for Sn", SnO, and SnO2 generation is (1)
, T2), as shown in equation (3), it is very base, so 5
Pb O2 where n-Pb alloy is positive i#l potential of lead battery
When placed at a generation potential, reactions (1), (2), +3) tend to proceed, resulting in so-called corrosion. In Figure 6, Sn
- Corrosion 12 is progressing along the Pb alloy layer 11,
Some of the plates are seen coming loose from the ears or straps, which can cause lead-acid batteries to reach premature end of their lifespans.

Means for Solving Problems The present invention solves the above-mentioned problems and provides a highly reliable strap with excellent corrosion resistance.

The gist is that in the cast-on-strap method for welding a group of electrode plates for a lead-acid battery, a coating layer of a lead-bismuth alloy is formed on the ear surface of each electrode plate, and each electrode plate on which the coating layer is formed is The method involves welding the strap and the electrode plate together and forming pole columns, straps, etc. by immersing the ear part in a molten vessel and solidifying it.

Example The welding method of the present invention will be explained below based on examples.

Example 1 For the reasons mentioned above, it is required that the coating layer applied to the electrode plate lugs in advance satisfy the following conditions.

The melting temperature is lower than that of the lead alloy used for strip f+1 Nislap, electrode plate lugs, etc.

Condition 2: Positive [! When placed at a potential, the amount of corrosion should be small.

As a result of examining various alloys that meet these two conditions, it was found that lead-bismuth alloys are effective.

In lead-bismuth alloys, when the amount of bismuth is less than about 55% by weight, the melting temperature decreases as the amount of bismuth increases. For example, in lead-32% and sumas alloy, pb-so%
It has a melting temperature of about 180°C, which is the same as the steel alloy.

Therefore, Pb-30%B1, Pb-50%Bi and P
b-Alloys A, B and C of 70% Bi were selected and the following tests were conducted to investigate the corrosion resistance of these alloys. Each alloy was continuously energized (70 mA) in sulfuric acid with a specific gravity of 1.28 at 75°C.
/ctg2×10 days rSfl> and repeated charging and discharging [1000-15001'1V (VS,)19/
H92So, )X800%:] was conducted to investigate the amount of corrosion after the test. For comparison, base metal E (40%) and Pb-4%9 alloy for grid were also tested at the same time. 5n
Table 1 shows the results of comparing each alloy, with the amount of corrosion of the -40% metal alloy set as 100.

The amount of corrosion of Alloy A in Table 1 was 55% after continuous energization and 28% after repeated charging and discharging, which was considerably lower than that of 5n-40% Alloy E. In alloy B in which the amount of B1 was 50%, the amount of corrosion slightly increased, but it was considerably less than that of the alloy layer. Alloy C is an alloy with a Bi content of 70%, but the amount of corrosion is 75% after continuous energization and 40% after repeated charging and discharging, compared to alloy A.
The amount of corrosion was slightly larger than B. Therefore, it seems that the amount of corrosion increases as the amount of Bi increases.
The B1 content is desirably 55% or less at which the melting temperature is the lowest.

In alloys A and B, which are products of the present invention, there is no significant difference in the amount of corrosion compared to lattice alloy E.

A summary of melting temperatures and corrosion resistance is shown in Table 2. Regarding corrosion resistance, ○ indicates good, Δ indicates slightly poor,
The X marks are bad.

The lead-bismuth alloy, which is the product of the present invention shown in Table 2 tlQ, 1.2, has a melting temperature similar to or lower than that of the 5n-Pb alloy, which is considerably lower than the melting temperature of the lattice alloy.
is met. It was also found that the corrosion resistance was superior to that of the 9-gate alloy, and that it had almost the same corrosion resistance as that of the lattice alloy. Therefore, condition 2 is also satisfied.

Example 2 Next, a forklift battery (VCF-3, approximately 200 Ah) was actually produced using alloys A, B, and E tested in Example 1, and the strap was evaluated. PB-4% alloy was used for the electrode plate ears and strap molten lead. In order to accelerate strap corrosion, an overcharging test was conducted at high temperature (75°C, 40A x 1 month). Figure 1 shows a cross-sectional view of the strap after the test of a battery using Alloy C. FIG. 6 is a sectional view of a strap of a battery whose electrode plate lugs were coated with 40% metal alloy and which were assembled and tested under the same conditions. In the strap shown in Fig. 6, corrosion progresses along the 5n-Pb alloy layer, and some electrode plate lugs are completely detached, but in the strap of the present invention, which has a bald area in Fig. 1, the plate lug coating layer 13 It was in very good condition with no corrosion observed along the edges. In addition, the strap condition of the battery using Alloy B was also good as in the case of N011.

Example 3 A sealed lead-acid battery (12V, 40^h) using Alloy A was produced and the strap was evaluated. A lead-calcium alloy was used for the electrode plate lug, and a tin-1% tin alloy was used for the molten lead strap. And high temperature overcharge test 111 (75°C, 1
0Ax1 month). As a result, as in the case of Example 2, the strap was in very good condition with almost no corrosion observed.

Effects of the Invention As is clear from the above embodiments, according to the present invention, a highly reliable strap with excellent corrosion resistance can be produced, and its industrial value is extremely large.

[Brief explanation of the drawings] Fig. 1 is a cross-sectional view of the strap part of the product of the present invention after an overcharge test, Fig. 2 is a cross-sectional view of a general lead-acid battery, and Fig. 3 is an explanation of the cast-on-strap method. Fig. 4 is a cross-sectional view of the strap in a bad condition with blowholes and negative meniscus due to the conventional cast-on-strap method, and Fig. 5 shows the 5n-Pb alloy coating layer on the electrode plate edge. Figure 6 is a cross-sectional view of the strap made by applying 5n-Pb.
It is a cross-sectional view after an overcharge test of a strap made by applying an alloy coating layer to the electrode plate lugs. 1...Positive electrode plate, 2... Separator, 3... Negative electrode plate, 4... Positive electrode plate Ear, 4'... Negative electrode plate lug, 5... Positive electrode strap, 5'... Negative electrode strap, 6... Positive electrode column, 6' River negative electrode column, 7... Mold, 8... Blow Hole, 9... Negative meniscus, 10... Positive meniscus, 11... 5n-Pb alloy 4.12... Corroded part, 13... Electrode plate edge coating layer 1st turn Ya concave diagram λ Otsu diagram

Claims (1)

[Claims] 1. In the cast-on-strap welding method for lead-acid battery plates, a coating layer of a lead-bismuth alloy is formed on the surface of the tab of each plate, and each plate on which the coating layer is formed is A method for welding a group of electrode plates for a lead-acid battery, characterized in that the strap and the electrode plates are welded together and the electrode poles, straps, etc. are formed by immersing and solidifying the ears in molten lead.