JP2006037129A - Aluminum alloy sheet for sealing sheet of secondary battery case - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum alloy sheet having excellent crack propagation properties and suitably used as a sealing sheet of a secondary battery case in which a safety valve is formed by coining. <P>SOLUTION: The aluminum alloy sheet for the sealing sheet of a secondary battery case has a composition containing, as essential components, by mass, 0.8 to 1.3% Mn, 0.2 to 0.5% Si and 0.3 to 1.0% Fe, and the balance Al with inevitable impurities, and in which the number of Al (Fe, Mn, Si) based intermetallic compounds with the maximum length of 0.5 to 3.0 μm is controlled to 5,000 to 20,000 pieces per mm<SP>2</SP>. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an aluminum alloy plate for a sealing plate of a secondary battery case.

  In recent years, secondary batteries such as lithium ion secondary batteries, nickel hydride secondary batteries, and nickel cadmium secondary batteries have excellent advantages such as high current, high voltage, long life, and high-speed charging. Therefore, it is widely used in various electric devices such as mobile phones, notebook personal computers, digital cameras, and portable AV devices.

  However, although these secondary batteries have the above-mentioned advantages, they are not general when stored under high temperature by direct sunlight, repeatedly short-circuited, or charged with a charger other than a dedicated charger. When used under circumstances, a large amount of gas may be generated inside the secondary battery case. If a large amount of gas is generated, the gas pressure in the case increases, and the secondary battery case may explode, which is extremely dangerous. In particular, the rectangular secondary battery case has lower pressure resistance than the round secondary battery case, and has a high risk of bursting.

  For this reason, most secondary battery cases, whether square or round, are equipped with a gas exhaust mechanism called a safety valve on a part of the sealing plate or case. Therefore, when the gas pressure in the case becomes excessively high, the safety valve is opened by the gas pressure, and a large amount of gas is discharged to prevent the secondary battery case from bursting.

  As a sealing plate for a secondary battery case using a safety valve, for example, as shown in FIG. 3, an aluminum foil 12a is pressure-bonded by clad rolling to the lower surface of an aluminum flat plate provided with a hole 14 for a safety valve. A sealing plate 11 in which a safety valve 12 is formed is known (see, for example, Patent Document 1). A metal plate obtained by pressure-bonding two or more metal plates in this way is called a clad plate.

  According to the sealing plate 11, when the internal pressure of the secondary battery case rises excessively, the safety valve 12 breaks and discharges the gas in the secondary battery case, thereby rapidly increasing the temperature of the battery and increasing the internal pressure of the battery. However, in order to obtain such a clad plate, it is necessary to roll the aluminum flat plate provided with the holes 14 and the aluminum foil 12a in a vacuum state. There is a problem that not only the rolling mill becomes large, but also the cost becomes high. Moreover, in the safety valve 12 described in Patent Document 1, the gas pressure (operating pressure) necessary for the safety valve 12 to break may vary depending on the pressure-bonded state of the aluminum foil 12a, and the operating pressure is not stable. It was.

Further, for example, like the sealing plate 21 shown in FIG. 4, by performing coining on an aluminum alloy flat plate or a pure aluminum flat plate, a valve body 22 a thinner than the plate thickness of the flat plate is formed, A safety valve 22 having a score 23 formed on the valve body 22a has been proposed (see, for example, Patent Document 2). Since the safety valve 22 having such a configuration can be easily cleaved along the score 23 when the pressure inside the secondary battery case is excessively increased due to the generation of gas, the gas can be quickly discharged.
Moreover, according to the sealing plate 21 provided with such a safety valve 22, it is not necessary to perform clad rolling under a vacuum state, so that it is possible to reduce the cost. Since it is not affected by the crimping state, it is possible to stabilize the operating pressure.

Patent Document 2 describes that the sealing plate 21 is produced using an aluminum alloy or pure aluminum. However, as a secondary battery case, in practice, the formability and corrosion resistance of pure aluminum are not reduced. , 3000 series aluminum alloys specified in JISH4000 with increased strength, such as aluminum alloy with alloy number 3003, and aluminum alloy with alloy number 3003-O softened and tempered by annealing Has been.
JP-A-10-241651 (Claim 1, paragraph 0021, FIG. 1) JP 2003-187774 A (paragraph 0020, paragraph 0029, FIG. 2, FIG. 4 and FIG. 11)

  However, in the case of an aluminum alloy having an alloy number of 3003 or an aluminum alloy having an alloy number of 3003-O, which has been conventionally used, it may not be said that the crack propagation property is sufficiently good for use as a safety valve. For example, even if gas is generated in the secondary battery case, only a small crack is generated and this does not propagate, and gas cannot be discharged quickly. In addition, since the crack propagation property is not sufficient, it is necessary to reduce the remaining thickness of the coining in order to impart sufficient crack propagation property to the safety valve, and there is a disadvantage that the control is difficult.

  The present invention has been made in view of the above problems, and has an object to provide an aluminum alloy plate that is excellent in crack propagation and can be suitably used as a sealing plate for a secondary battery case in which a safety valve is formed by coining. To do.

  As a result of diligent research, the present inventors have found that the above problems can be solved by regulating the composition of the aluminum alloy to an appropriate range and specifying the properties of the aluminum alloy plate, and completed the present invention. It came to do.

That is, in the invention described in claim 1, as essential components, Mn: 0.8% by mass to 1.3% by mass, Si: 0.2% by mass to 0.5% by mass, Fe: 0.3% The number of Al (Fe, Mn, Si) -based intermetallic compounds containing 1% by mass or more and 1.0% by mass or less, the balance being Al and inevitable impurities, and a maximum length of 0.5 μm or more and 3 μm or less is 1 mm ^2. An aluminum alloy plate for a sealing plate of a secondary battery case, wherein the number is 5,000 or more and 20,000 or less.

  In the invention according to claim 2, as an optional component, Cu: 0.5% by mass or less, Ti: 0.1% by mass or less, or Cu: 0.5% by mass or less and Ti: 0.1% by mass 2. The aluminum alloy plate for a sealing plate of a secondary battery case according to claim 1, wherein the aluminum alloy plate is contained.

  Thus, the aluminum alloy plate for the sealing plate of the secondary battery case according to claim 1 or claim 2 has various strengths required for the sealing plate of the secondary battery case since various components are regulated to an appropriate range. While ensuring moldability, among these components, it contains a large amount of Si and Fe, and further, by regulating the number per unit area of intermetallic compounds having the maximum length of a specific range, it is excellent Crack propagation can be imparted. That is, it is possible to provide an aluminum alloy plate for a sealing plate of a secondary battery case having excellent cleavability. Moreover, the aluminum alloy plate for the sealing plate of the secondary battery case which gave the predetermined characteristic further by containing Cu or Ti suitably can be provided.

  According to the present invention, an aluminum alloy plate for a sealing plate of a secondary battery case, which is excellent in formability and corrosion resistance, has excellent crack propagation properties, and is suitable for use as a sealing plate of a secondary battery case that forms a safety valve by coining. Can be provided.

Next, the best mode of the aluminum alloy plate for the sealing plate of the secondary battery case according to the present invention will be described in detail.
[Configuration of aluminum alloy plate for sealing plate of secondary battery case]
The aluminum alloy plate for the sealing plate of the secondary battery case of the present invention has, as essential components, Mn: 0.8% by mass to 1.3% by mass, Si: 0.2% by mass to 0.5% by mass, Fe: 0.3% by mass or more and 1.0% by mass or less between Al (Fe, Mn, Si) -based metals having the balance consisting of Al and inevitable impurities and having a maximum length of 0.5 μm to 3 μm The number of compounds is 5000 or more and 20000 or less per 1 mm ² . Further, in addition to Mn, Si, and Fe, which are essential components of the aluminum alloy plate for the sealing plate of the secondary battery case, Cu: 0.5% by mass or less or Ti: 0.1% by mass or less as an optional component, Alternatively, an aluminum alloy plate for a sealing plate of a secondary battery case containing Cu: 0.5% by mass or less and Ti: 0.1% by mass or less can also be suitably used.

  Hereinafter, in the aluminum alloy plate for the sealing plate of the secondary battery case according to the present invention, the reason for regulating the contents of various components, and the maximum length of the Al (Fe, Mn, Si) intermetallic compound in the aluminum alloy plate The reason why the number of Al (Fe, Mn, Si) intermetallic compounds is regulated will be described.

(Mn content: 0.8 mass% or more and 1.3 mass% or less)
Mn is dissolved in the matrix and has the effect of increasing the strength of the aluminum alloy sheet. At the same time, Mn is combined with Al, Fe, and Si to produce an Al—Fe—Mn intermetallic compound or Al—Fe—Mn—. Since the Si-based intermetallic compound is formed, it has an effect of improving the cleavability of a safety valve formed by coining because it is a starting point of fracture when stress is applied and has an effect of improving crack propagation. When the Mn content is less than 0.8% by mass, the effect of improving the cleavability of the safety valve is reduced. On the other hand, if the Mn content exceeds 1.3% by mass, a coarse intermetallic compound is generated, which tends to be a starting point of cracking during forming, and thus the formability of the aluminum alloy plate is lowered. Therefore, the Mn content is 0.8 mass% or more and 1.3 mass% or less.

(Si content: 0.2 mass% or more and 0.5 mass% or less)
Si forms an Al—Fe—Mn—Si intermetallic compound with Al, Mn, Fe, or the like. This intermetallic compound has an effect of improving the cleavability of a safety valve formed by coining because it has the effect of becoming a starting point of fracture when stress is applied and improving crack propagation. When the Si content is less than 0.2% by mass, the effect of improving the cleavability of the safety valve is reduced. On the other hand, if the Si content exceeds 0.5% by mass, the Al—Fe—Mn—Si intermetallic compound is coarsened and the number is increased, so that the moldability is lowered. Further, when the Si content exceeds 0.5% by mass, the laser weldability is also lowered. Therefore, Si content shall be 0.2 mass% or more and 0.5 mass% or less.

(Fe content: 0.3 mass% or more and 1.0 mass% or less)
Fe forms an Al—Fe—Mn intermetallic compound and an Al—Fe—Mn—Si intermetallic compound, and therefore has the effect of becoming a starting point of fracture when stress is applied and improving crack propagation. Therefore, it has an effect of improving the cleavability of the safety valve formed by coining. If the Fe content is less than 0.3% by mass, the amount of intermetallic compound produced decreases, and the effect of improving the cleavability of the safety valve is reduced. On the other hand, when the Fe content exceeds 1.0% by mass, the intermetallic compound is coarsened and the number thereof is increased, which tends to be a starting point of cracking during forming, so that the formability of the aluminum alloy plate is lowered. To do. Therefore, the Fe content is set to 0.3% by mass or more and 1.0% by mass or less.

(Cu content: 0.5 mass% or less)
Cu has the effect of increasing the strength of the aluminum alloy plate by solid solution strengthening. If the Cu content exceeds 0.5% by mass, the formability of the aluminum alloy plate is lowered and the laser weldability is lowered. In addition, the effect which raises the intensity | strength of an aluminum alloy plate is small as content of Cu is less than 0.01 mass%. Therefore, the Cu content is preferably 0.5% by mass or less, and more preferably 0.01% by mass or more and 0.5% by mass or less, which is an unavoidable impurity level or more.

(Ti content: 0.1% by mass or less)
Ti has the effect of refining the solidification structure at the time of ingot production, and contributes to productivity improvement by preventing casting cracks and hot rolling cracks. When the Ti content exceeds 0.1% by mass, a huge Al—Ti intermetallic compound is generated, and the formability of the aluminum alloy sheet is lowered. If the Ti content is less than 0.01% by mass, the effect of refining the solidified structure during ingot production is small. Accordingly, the Ti content is preferably 0.1% by mass or less, and more preferably 0.01% by mass or more and 0.1% by mass or less, which is an inevitable impurity level or more.

(Inevitable impurities)
The inevitable impurities contained in the aluminum alloy of the aluminum alloy plate for the sealing plate of the secondary battery case of the present invention may contain elements such as Cr, Zn, Zr, B, etc., but these inevitable impurities are Even if it is contained at a content of less than 0.05% by mass, it does not affect the properties of the aluminum alloy sheet in the present invention. Therefore, it is allowed to contain these inevitable impurities as long as the effects of the present invention are not hindered.

(The number of Al (Fe, Mn, Si) -based intermetallic compounds having a maximum length of 0.5 μm to 3 μm is 5000 to 20000 per mm ² )
The Al (Fe, Mn, Si) intermetallic compound in the present invention includes an Al—Fe—Mn intermetallic compound, an Al—Fe—Mn—Si intermetallic compound, an Al—Fe—Si intermetallic compound, And Al—Mn—Si intermetallic compounds are included, but it is not necessary to strictly distinguish them.
When the maximum length of the Al (Fe, Mn, Si) intermetallic compound is less than 0.5 μm, the effect of improving the cleavability of the safety valve formed by coining is reduced, and Al (Fe, Mn, Si) When the maximum length of the intermetallic compound exceeds 3 μm, it tends to be a starting point of cracking when being molded as a sealing plate. Therefore, the maximum length of the Al (Fe, Mn, Si) -based intermetallic compound is 0.5 μm or more and 3 μm or less.

If the Al (Fe, Mn, Si) -based intermetallic compound having the maximum length is less than 5000 per mm ^2, the effect of improving the cleavability of the safety valve formed by coining is reduced. On the other hand, when the Al (Fe, Mn, Si) -based intermetallic compound having such a maximum length exceeds 20000 per 1 mm ² , it tends to be a crack propagation path when being molded as a sealing plate. Therefore, the number per 1 mm ² of Al (Fe, Mn, Si) -based intermetallic compounds having a maximum length of 0.5 μm or more and 3 μm or less is 5000 or more and 20000 or less.

[Method for producing aluminum alloy sheet]
Next, the manufacturing method of the aluminum alloy plate of this invention is demonstrated.
As a typical method for producing the aluminum alloy sheet of the present invention, an ingot of aluminum alloy having the composition component defined in claim 1 or 2 of the present invention is subjected to homogenization heat treatment, followed by hot rolling and cold There is a method in which rolling is performed to a predetermined plate thickness, and the obtained rolled plate is annealed.

In this case, the homogenization heat treatment is preferably performed at 550 ° C. or more and the hot rolling finish temperature is preferably 300 ° C. or more. The annealing is performed at 400 ° C. or more if continuous annealing, and 300 to 400 ° C. if batch annealing is performed. It is preferable to carry out with. Moreover, as a manufacturing method, it is not limited to the said method, For example, you may perform intermediate annealing with the plate | board thickness in the middle of cold rolling.
Thus, by producing the aluminum alloy having the above composition by the production method described above, the maximum length of the Al (Fe, Mn, Si) -based intermetallic compound and a predetermined number per unit area (pieces / piece mm ² ) and the aluminum alloy plate for the sealing plate of the secondary battery case of the present invention.

[Secondary battery case]
Next, a secondary battery case provided with a sealing plate made of an aluminum alloy plate for a secondary battery case sealing plate according to claim 1 or claim 2 of the present invention will be described.
As shown in FIG. 1, the secondary battery case 4 is configured as a sealed container by laser welding the main body 5 of the secondary battery case 4 and the sealing plate 1.
The sealing plate 1 is formed by cutting the aluminum alloy plate for the secondary battery case sealing plate of the present invention into a predetermined size and coining, thereby engraving a score 3 on a predetermined portion of the sealing plate 1. The safety valve 2 is provided. The shape of the sealing plate 1 may be an ellipse, a circle or a rectangle, and the score 3 may be formed inside the secondary battery case.

  It should be noted that the present invention is not limited to the contents of the best embodiment described above and the examples described below, and can be appropriately changed as long as it is based on the technical idea of the present invention. It goes without saying that it is possible.

[Example A]
Next, referring to [Example A], the aluminum alloy plate for secondary battery case sealing plate of the present invention satisfies the requirements of claim 1 of the present invention and the requirements of claim 1 of the present invention. This will be specifically described in comparison with a comparative example.
That is, in [Example A], the size and number of Mn, Si, Fe and Al (Fe, Mn, Si) -based intermetallic compounds, which are essential components of the aluminum alloy plate for a secondary battery case sealing plate of the present invention. The density was examined.
Table 1 shows Invention Example No. 1-4 and Comparative Example No. The compositional component content of 1 to 6 aluminum alloy plates and the number of intermetallic compounds per unit area (1 mm ² ) are shown. Invention Example No. having such properties. 1-4 and Comparative Example No. The 1-6 aluminum alloy plates were produced as follows.

First, Invention Example No. 1 in Table 1 was used. 1-4 and Comparative Example No. Ingots of respective aluminum alloys having the compositions shown in 1 to 6 and the balance being Al and inevitable impurities were produced. These ingots were subjected to a homogenization heat treatment at 600 ° C. and subjected to hot rolling and cold rolling to produce rolled plates having a plate thickness of 1.0 mm. The temperature at the end of hot rolling was 350 ° C. Thereafter, as the annealing, each rolled plate was subjected to batch annealing at 350 ° C. for 3 hours. 1-4 and Comparative Example No. Aluminum alloy plates shown in 1 to 6 were produced.
The maximum length and number of Al (Fe, Mn, Si) -based intermetallic compounds per 1 mm ² are the same as those in Invention Example No. 1-4 and Comparative Example No. After the surface of the aluminum alloy plates 1 to 6 is buffed by 5 μm, an Al (Fe, Mn, Si) -based metal is obtained by SEM (magnification = 1000 times) equipped with an EDS (Energy Dispersive Spectrometer). The relationship between the maximum length and number of intermetallic compounds was investigated. This was performed for each aluminum alloy plate for 50 views, and the number per 1 mm ² was determined for Al (Fe, Mn, Si) intermetallic compounds having a maximum length of 0.5 μm or more and 3 μm or less (in Table 1). “Described as the number of intermetallic compounds having a maximum length of 0.5 μm to 3 μm”).
In addition, the underline in Table 1 shows that it is outside the range regulated by the present invention.

  Next, Invention Example No. 1 produced as described above was used. 1-4 and Comparative Example No. The strength, formability, laser weldability, and tearability were evaluated using 1 to 6 aluminum alloy plates.

〔Strength〕
Invention Example No. 1-4 and Comparative Example No. About the aluminum alloy plates of 1-6, the JIS5 tension test piece was produced so that a tension direction might become parallel to a rolling direction. Then, the tensile test by JISZ2241 was implemented and the tensile strength, yield strength, and elongation were calculated | required. As the proof stress, 42 N / mm ² or more was considered good.

[Formability]
Invention Example No. 1-4 and Comparative Example No. For the aluminum alloy plates 1 to 6, the Erichsen test specified in JISB7729 and JISZ2247 was conducted with a 20 mmφ ball-head punch by the JISA method, and the Erichsen value was measured. An Erichsen value of 10.8 mm or more was accepted. The Erichsen value refers to the amount of drawing until cracking occurs in the Eriksen test.
In addition, a molding test was performed with a 40 mmφ flat-head punch, and the occurrence of cracks was visually observed to determine the limit drawing ratio of crack generation, that is, the ratio of the blank diameter to the punch diameter of 40 mm. A limit drawing ratio of 2.10.
Those in which either of these Erichsen values or the limit drawing ratio does not satisfy the above-mentioned criteria were evaluated as being inferior in formability and rejected (inferior formability).

[Laser weldability]
Invention Example No. 1-4 and Comparative Example No. About the 1-6 aluminum alloy plates, pulse laser welding was performed by end part butt | matching. Sound welds with no defects such as cracks and good bead shape with a constant bead for each pulse (“◯”), good weld bead shape disordered (“△”), crack The thing which generate | occur | produced was evaluated as a defect ("*").

[Cleavage]
Invention Example No. 1-4 and Comparative Example No. About the aluminum alloy plates of 1-6, as shown in FIG. 2, using a plate of 40 mm × 40 mm, a coining process was performed to form a C-shaped score. Note that the remaining thickness of the score was 80 μm. The aluminum alloy plate was fixed and pulled upward, the maximum load at the time of score tear was measured, and the tearability was judged. Those having a tear load of 11.0 N or less were regarded as acceptable and judged as acceptable.
The results of these evaluations are shown in Table 2. In addition, the underline in Table 2 shows that it is outside the range regulated by the present invention.

As shown in Table 2, Comparative Example No. 1 to 6 is the composition of the aluminum alloy plate or the number per 1 mm ² of Al (Fe, Mn, Si) intermetallic compound having a maximum length of 0.5 μm or more and 3 μm or less is regulated by the present invention. Since it was out of the range, an undesirable result was obtained in any of strength, formability, laser weldability, and cleavability.

That is, Comparative Example No. 1 is the number per 1 mm ² of Al (Fe, Mn, Si) -based intermetallic compounds whose Mn content is less than the lower limit of the range regulated by the present invention and whose maximum length is 0.5 μm or more and 3 μm or less. However, since it is less than the lower limit value of the range regulated by the present invention, the strength of the aluminum alloy plate was insufficient and the tearability was poor.
Comparative Example No. 2, since the content of Mn exceeds the upper limit of the range regulated in the present invention, the maximum length exceeds 3 μm between Al—Fe—Mn intermetallic compound and Al—Fe—Mn—Si based metal A compound was generated, resulting in poor moldability.

Comparative Example No. 3 is less than the lower limit of the range regulated by the present invention, and the lower limit of the range in which the number per 1 mm ² of intermetallic compounds having a maximum length of 0.5 μm to 3 μm is regulated by the present invention. Since it was less than a value, the result was inferior in cleavability.
Comparative Example No. 4, the Si content exceeds the upper limit of the range regulated in the present invention, and the maximum length is 0.5 μm or more and 3 μm or less of Al (Fe, Mn, Si) intermetallic compound per 1 mm ² . Since the number exceeded the upper limit of the range regulated by the invention, the formability and laser weldability were inferior.

Comparative Example No. 5 is the number per 1 mm ² of Al (Fe, Mn, Si) based intermetallic compounds whose Fe content is less than the lower limit of the range regulated by the present invention and whose maximum length is 0.5 μm or more and 3 μm or less. Is less than the lower limit of the range regulated by the present invention, resulting in poor cleavage.
Comparative Example No. 6, the Fe content exceeds the upper limit of the range regulated by the present invention, and the maximum length is 0.5 μm or more and 3 μm or less of Al (Fe, Mn, Si) intermetallic compound per 1 mm ² . Since the number exceeded the upper limit of the range regulated by the present invention, the yield strength and the formability were inferior.

In contrast, Invention Example No. 1-4 is the composition of the aluminum alloy plate and the number per 1 mm ² of Al (Fe, Mn, Si) intermetallic compound having a maximum length of 0.5 μm or more and 3 μm or less. Since it was within the regulated range, it exhibited good strength, formability, laser weldability, and tearability.

[Example B]
Next, in order to give predetermined characteristics to the aluminum alloy plate for a secondary battery case sealing plate of the present invention, the Cu content and the Ti content were examined.

Table 3 shows Invention Example No. 5-14 and Comparative Example No. The compositional component content of 7 to 10 aluminum alloy plates and the number of intermetallic compounds per unit area (1 mm ² ) are shown.
As shown in Table 3, Invention Example No. 5 to 14 contain Mn, Si, and Fe, which are essential components shown in [Example A], within the range regulated by the present invention, and further contain at least one of Cu and Ti as an optional component. It has been made. Comparative Example No. 7 to 10 contain Cu and Ti in amounts exceeding the range regulated by the present invention.

And invention example No. shown in Table 3 is shown. 5-14 and Comparative Example No. 7-10 aluminum alloy plates were produced under the same production conditions as in [Example A]. The maximum length and number of Al (Fe, Mn, Si) -based intermetallic compounds per 1 mm ² were measured by the same method as in [Example A].
In addition, "-" in Table 3 shows that content is less than 0.01 mass%, and the underline in Table 3 shows having remove | deviated from the range regulated by this invention.

  And invention example No. produced as mentioned above. 5-14 and Comparative Example No. About 7-10 aluminum alloy plates, evaluation about intensity | strength, a moldability, laser weldability, and cleavability was performed according to [Example A]. The results are shown in Table 4. In addition, the underline part in Table 4 shows that it has remove | deviated from the range regulated by this invention.

As shown in Table 4, Comparative Example No. Nos. 7 and 9 resulted in inferior formability and laser weldability because the Cu content exceeded the upper limit of the preferred range regulated by the present invention.
Comparative Example No. In Nos. 8 and 10, since the Ti content exceeded the upper limit of the preferable range regulated by the present invention, a large Al—Ti intermetallic compound was generated, resulting in poor formability.

In contrast, Invention Example No. 5 to 14 are the contents of the essential components of the aluminum alloy plate and the number per 1 mm ² of Al (Fe, Mn, Si) intermetallic compound having a maximum length of 0.5 μm or more and 3 μm or less. Since it was within the regulated range and Cu and Ti were contained within the preferred range regulated by the present invention, they exhibited good strength, formability, laser weldability, and cleavability. In particular, Invention Example No. Since 6, 12, and 13 contained a relatively large amount of Cu, the yield strength was increased. Although not shown in Table 4, Invention Example No. Since No. 13 contains a relatively large amount of Ti, casting cracks, hot rolling cracks, and the like were not observed in the manufacturing process, and thus productivity such as yield can be improved.

It is principal part sectional drawing which shows an example of the safety valve provided in the sealing board of the secondary battery case. It is a figure which shows a mode that the test of cleavability is performed. It is principal part sectional drawing which shows an example of the safety valve provided in the sealing plate of the conventional secondary battery case. It is principal part sectional drawing which shows another example of the safety valve provided in the sealing board of the conventional secondary battery case.

Explanation of symbols

1 Sealing plate 2 Safety valve 3 Score

Claims (2)

As essential components, Mn: 0.8 to 1.3% by mass, Si: 0.2 to 0.5% by mass, Fe: 0.3 to 1.0% by mass The balance consists of Al and inevitable impurities,
For a sealing plate of a secondary battery case, wherein the number of Al (Fe, Mn, Si) intermetallic compounds having a maximum length of 0.5 μm or more and 3 μm or less is 5000 or more and 20000 or less per 1 mm ² . Aluminum alloy plate.   As an optional component, Cu: 0.5% by mass or less, Ti: 0.1% by mass or less, or Cu: 0.5% by mass or less and Ti: 0.1% by mass or less The aluminum alloy plate for a sealing plate of the secondary battery case according to claim 1.

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