JPH04366556A - Lead-acid battery electrode plate and its manufacture - Google Patents

Abstract

PURPOSE:To improve the high temperature durability of a lead-acid battery using a grating formed by expanding a rolled sheet of a lead-calcium alloy, and assist the development of a maintenance-free battery having the accommodative force to the battery environment which has been recently changed to a higher temperature. CONSTITUTION:The rolling of a sheet is conducted by use of a multistage roller, a proper value larger than 1 is basically selected as the advance ratio represented by the speed of the rolled and discharged sheet/the tangential linear speed of the roller, and the speed is suppressed lower than the speed inner part of a rolled body surface making contact with the roller. Thus, a manufacturing method capable of satisfactorily performing the rolling even in the area having 0.1% or more of calcium was developed. In this process, a manufacturing method commonly using the method of slipping the surface of the roller was also developed. Although this area was significantly corrosive in the past, a grating highly strong to elongation, resistant to corrosion, and resistant to the use under high temperature can be provided by forming a laminated fine crystal structure by the rolling method.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead-acid battery electrode plate widely used in automobiles, industry, and consumer electronics, and a method for manufacturing the same.

0002

BACKGROUND OF THE INVENTION In recent years, as the demand for maintenance-free lead-acid batteries has increased, lead-acid batteries have been developed that use alloys in the grid that do not contain antimony, which causes self-discharge and liquid loss.

Among them, the most practical battery system is the so-called calcium type, which uses a lead-calcium-tin alloy as the lattice alloy.

[0004] For this calcium type battery, attempts have been made to use the casting method, partly because conventional grids have historically been made using the casting method, but there have been problems with the castability of the grid and problems with corrosion resistance. Currently, a thick cast body is rolled with multi-stage rolling rollers to form a continuous sheet, which is then made into a mesh by applying a mechanical network development method commonly called expansion, and this is used as a grid. method has been adopted.

Strict selections have been made regarding the corrosion resistance of these alloys as well as their construction methods and productivity.

First of all, regarding corrosion resistance, it is 0.10 wt% (hereinafter referred to as %) due to the basic solid solution properties of this type of alloy.
In particular, there are test results in cast alloys showing that corrosion becomes extremely severe when the content exceeds 0.15%, and severe corrosion troubles have been encountered in practical applications such as automobiles. Based on these facts, the actual situation is that generally the area exceeding 0.10% has been regarded as a dangerous area.

[0007] On the other hand, problems with the construction method are that cracks occur in the sheet during slab rolling, and that bones break at various places even when expanded. The calcium content has a great effect on the ductility of the alloy; for example, when the calcium content is around 0.05 to 0.07%, the elongation at break (the ratio of the stretched dimension to the original dimension until it breaks when pulled) is large at about 20% and is easy to elongate, whereas in the region exceeding 0.10% it is as low as 7 to 8% at most. This can lead to increased risk of fractures and fractures.

For these reasons, the appropriate composition range has traditionally been considered to be 0.02% to 0.1% for calcium and 0.3% to 2.0% for tin, and within this matrix range, Furthermore, an appropriate tin/calcium ratio of 5 to 7 was introduced in search of ease of processing, and a number of additive components to strengthen the lattice and a technique for age hardening by heat treatment were also proposed.

[0009] In reality, it is common knowledge that in most expanded lattices, the calcium content is about 0.07%. The lead-acid battery that used the calcium-type expanded lattice that appeared in this way replaced the conventional battery that used an antimony alloy lattice, and was used in many automobiles, and the composition was recognized and developed as a new maintenance-free battery. There were no problems with the construction method at that time.

0010

[Problem to be solved by the invention] However, in recent years,
In addition to the high efficiency of engines, the adoption of turbochargers, and the increased density of engine compartments, there is also an increase in road congestion, creating a battery environment that has never been experienced before.75
The temperature is often so high that it exceeds 90°C, and sometimes exceeds 90°C.

[0011] There is an emerging trend of short battery life of a type that has not occurred heretofore. It has been revealed that the cause of this is mainly corrosion and elongation of the lattice due to use at high temperatures, and separation also occurs between the active material and the lattice.

[0012] Since this problem basically concerns the strength of the alloy, it became necessary to seek a new method for creating a strong lattice. In other words, technology that takes advantage of the expanded lattice made of lead-calcium-tin alloy, which has excellent maintenance-free properties and high productivity, and prevents the lattice from elongating and the resulting peeling in this harsh high-temperature environment will become the future maintenance-free technology. It has become necessary as a response to the times.

[0013]

[Means for Solving the Problems] In order to solve the above problems, the present invention takes on the challenge of developing alloys with a calcium content of more than 0.10% by weight, which has been avoided in the past from the viewpoint of corrosion. It can be rolled without causing
They also discovered that expansion processing is possible without breaking bones, and that the resulting lattice is resistant to elongation and has excellent corrosion resistance.

[0014] That is, the basic structure is that a substrate of a lead-calcium-tin alloy with a calcium content of more than 0.10% by weight is cast and then has a dense, laminated crystal structure obtained by a rolling process. This invention discloses an electrode plate for a lead-acid battery, characterized in that an expanded continuous sheet is used as a grid.

[0015] Also, among the several methods suitable for carrying out the above-mentioned processing without any problems, the most effective manufacturing method is the casting process, rolling process, expanding process, and paste application of lead-calcium-tin alloy. In this rolling process, the cast body is rolled step by step into a continuous sheet shape using multi-stage rolling rollers, and in at least one stage the cast body is rolled and rolled out of the rollers. Progression speed of rolling object/linear speed of rolling roller (
This study clarified a method in which the rolling ratio (referred to as the advanced ratio) is made larger than 1 and rolling is performed while the rollers are delayed. Furthermore, the advanced ratio is in a highly practical range of 1.05 or more and 1.20 or less, and furthermore, a method is proposed in which the advanced ratio is made smaller than 1 at any stage of this multi-stage rolling and rolling is performed while slipping. It will be revealed that combined use is effective. Another way to make good use of alloy sheets that are difficult to stretch is to expand them without heat treatment.
A manufacturing method in which the material is then heat treated and cured is also disclosed.

[0016]

[Function] In the region where calcium is slightly more than 0.10% by weight, where highly corrosive intermetallic compound Pb3Ca is formed, the tensile strength of the alloy is nearly twice that of the region with less calcium, resulting in mechanical strength. It has the basic properties that make it . Calcium content in this range is generally said to be inferior in corrosion resistance, but even in this range, rolling treatment and making the crystal form into a dense layered structure can provide corrosion resistance that can withstand use at high temperatures. I discovered that I could make it last.

[0017] There is little information on the corrosion resistance of this composition range, as it has been difficult to properly roll or expand it in the past, and most of the test results were based on cast specimens with large grain boundaries. It seems to be known whether the corrosion resistance of alloys in this region can be improved, but in reality it has not been fully elucidated.

[0018] Such a corrosion-resistant effect can be seen even in a region with a small amount of tin, but it becomes more noticeable when the tin content is 0.5% or more. The content of tin may be large for corrosion resistance, but it may cause dendrites if left over-discharged at high temperatures for a long period of time, so it is thought that it is best to keep the tin content within 2% when incorporated into the base material.

As mentioned above, in the region where the calcium content exceeds 0.1% by weight, cracks are likely to occur during rolling and bones are likely to break during expanding. There are many ways to proceed appropriately in this area. For example, it is possible to proceed with rolling or expanding slowly, or to roll at a high temperature close to 200°C. Choosing the amount of tin added also helps. However, in order to achieve proper rolling with high productivity, instead of rolling to a fine crystalline structure all at once using multi-stage rolling rollers as in the past, rolling should be done sequentially so that the thickness does not exceed 1/2 of the original thickness at most. The first thing to do is to roll it. A more effective measure is to set the mirror finish of the rolling roller and the rotational speed so that the speed at which the rolled object is sent out from the roller/linear speed of the rotating roller (advanced ratio) is greater than 1 and an appropriate value is selected. This can suppress the occurrence of cracks even in alloys that are difficult to stretch. Adjusting this advance ratio to 1.05 or more and 1.20 or less is effective for high-speed rolling as high as 30 m/min. Although the mechanism in this case is not clear in detail, it appears that by slowing down the roller speed so that the inner layer precedes the surface layer, cracks are prevented from occurring during rolling.

[0020] If cracks still occur, this can be improved by simultaneously using a method in which rollers are rotated at high speed and rolled while slipping in a part of the multi-stage rolling process. This crack prevention effect is particularly effective not only in regions with a high calcium content, but also in regions with a conventionally low calcium content, since cracks are more likely to occur when the production speed is increased.

[0021] On the other hand, prevention of bone fracture during expansion processing is basically not a problem as long as no cracks occur during rolling, but when the rolling speed is increased or when the calcium content exceeds 0.2% by weight. is likely to cause trouble. Normally, after rolling, the material is heat treated at 50 to 100°C for several hours or more to age harden it and then expanded, but when it already has a tensile strength of 4 to 5 kg/mm2 that can withstand processing due to the increased calcium content, it becomes more difficult. Heat treatment is not preferred.

However, the final tensile strength may be applied after the expanding process, as this is necessary to prevent the grid from elongating during use. In this case, it may also be used for aging and drying after applying the paste.

[0023]

[Examples] The features of the present invention will be described below with reference to Examples. A matrix of calcium content and tin content in a lead-calcium-tin alloy is assembled, and an alloy substrate is continuously cast using a conventional method. This is rolled with multi-stage rollers and expanded using a conventional method to form a net shape. Make it a grid. An active material paste was applied to this, molded into the shape of an electrode plate, aged and dried to produce an unformed electrode plate.The quality was observed during this process, and a battery with a 5-hour rate capacity of 48AH was constructed using the paste. The charging conditions were 14.0V and a constant voltage charge of 25A at a maximum current of 2 hours in a gas phase atmosphere at 75℃, and the discharge was set at 25A for 1 hour.This was considered as one cycle, and every 39 cycles, the voltage was discharged at 310A at 90℃, and the voltage at the 30th second was set. A test was conducted in which the life span was defined as the time when the voltage became 7.2V or less.

FIG. 1 shows a lattice in the conventional composition range, with a calcium content of 0.07% by weight (hereinafter simply referred to as %).
, the number of lifetimes when the tin content is 0.3% is 100, and the lifetimes under various lattice conditions are expressed as an index. Further, the absolute value of the vertical elongation of the lattice of the electrode plate B at the end of its life is also shown as L in FIG. In these, A,
B and C have a tin content of 0.3%, 0.5%, and 2.0, respectively.
%. Note that the rolling speed was approximately 30 m/min. In addition, in order to form a lattice without cracking over a wide composition range, the advanced ratio had to be approximately 1.1.

[0025] D has the same composition as A, but the rolling speed is 55 m/
8 minutes since cracks occurred.
Among the rollers in the stages, the rotational speed of the roller in the fifth stage,
By adjusting the rolling rate, roller spring pressure, etc., we increased the linear speed on the roller side and rolled it while slipping, eliminating the occurrence of cracks. This is an example in which this sheet was heat treated at 75° C. for 6 hours and then expanded.

[0026] E is a case in which expand processing was performed without heat treatment, and after filling with an active material, aging and drying was added at 60°C or higher.

Next, the effects of the present invention will be explained with reference to this figure. The results of A to C show that, compared to the conventional range of 0.1% or less calcium, in the range of the present invention where calcium is more than 0.1%, conventional cast alloys have been abandoned as being unusable due to corrosion. However, the results show that the durability against harsh high-temperature environments is significantly improved. This shows that even in this high calcium content region, if the layered crystal structure is properly created, durability superior to that of conventional materials can be achieved. It has also been shown that the tin content helps improve its durability. Also L
In relation to this, the durability against this high temperature environment has a deep relationship with the elongation of the lattice, indicating that the present invention has improved the strength of the lattice itself.

On the other hand, in D, if a sheet whose hardness has been increased by heat treatment is forcibly expanded, cracks will occur in the bones rather than the elongation itself, which will shorten the life of the sheet. On the other hand, E indicates that it can be improved by not heat-treating before expanding, but by heat-treating after processing.

[0029] Regarding the advanced ratio, which is one of the important elemental technologies of the present invention, the advanced ratio is 1.05 to 1.2 for a calcium content of 0.14% where cracks are likely to occur.
FIG. 2 shows the crack occurrence rate per 1000 plates for X in the range of 0 and Y in the case of less than 1.05. Although it is not uniform due to the relationship with production speed, if the production rolling speed is around 30 to 60 m/min, the advanced ratio is 1.05 to 1.20.
would be appropriate. This setting also changes the rolling rate of each roller,
It can be easily adjusted by adjusting the feed speed and thickness of the material, the rotation speed of the roller, and the roll spring.

[0030] This effect is related to the basics of the skeleton and cannot be changed by the combination of existing additives, impurities, surface treatments, and other auxiliary techniques, and whether the electrode plate is applied to the positive or negative electrode. The battery type is also limited to a range in which it can be applied to either a liquid-filled battery or a gas absorption type sealed battery.

[0031]

As described above, the present invention suppresses the elongation of the lattice at high temperatures in a lead-acid battery using a calcium-type lead alloy lattice, and significantly improves the durability at high temperatures. This makes it possible to provide a maintenance-free lead-acid battery that can withstand an environment that will become increasingly hotter in the near future.

[Brief explanation of the drawing]

[Figure 1] Diagram showing the results of high-temperature durability tests of batteries using grids with various compositions.

[Figure 2] Diagram showing the relationship between rolling speed and crack occurrence rate

[Explanation of symbols]

A shows the characteristics of the example of the present invention, and the amount of tin added is 0.
3% B Indicates the characteristics of the example of the present invention, and the amount of tin added is 0.
5% C Indicates the characteristics of the example of the present invention, and the amount of tin added is 2.
0% D Heat-treated before expanding E Heat-treated by expanding (processing machine) L Example of elongation of lattice after durability test

Claims (6)

[Claims] 1. A lead-calcium-tin alloy slab casting process, a rolling process, an expanding process, and a paste coating process, and in the rolling process, the slab casting is gradually formed into a continuous sheet using multi-stage rolling rollers. A method for producing an electrode plate for a lead-acid battery, characterized in that the linear speed of the rolling roller is reduced in relation to the advancing speed of the rolled object leaving the roller in at least one stage. . [Claim 2] The ratio of the advancing speed of the rolled object leaving the roller/the linear speed of the rolling roller (referred to as the advancing ratio) is 1.05.
2. The method for manufacturing a lead-acid battery electrode plate according to claim 1, wherein the value is 1.20 or less. 3. The method of manufacturing a lead-acid battery plate according to claim 1, further comprising a step of rolling the plate while slipping at least one roller with an advance ratio of less than 1. 4. A continuous sheet with a dense, laminated crystal structure obtained by rolling a lead-calcium-tin alloy substrate with a calcium content of more than 0.10% by weight. An electrode plate for a lead-acid battery produced by the manufacturing method according to claim 1, using the expanded body as a lattice. 5. The electrode plate for a lead-acid battery according to claim 4, wherein the content of tin is 0.5% or more by weight. 6. The method for producing an electrode plate for a lead-acid battery according to claim 4 or 5, wherein heat treatment is not performed before the expanding process, but heat treatment is performed at a temperature of 60 to 100° C. for at least 6 hours or more in the step after the expanding process. .