JP2000129384A - Aluminum alloy sheet for secondary battery case, its manufacture, and secondary battery case - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture an aluminum alloy sheet for secondary battery case, excellent in strength and formability and improved in blister resistance, and to provide a secondary battery case. SOLUTION: This sheet consists of an aluminum alloy sheet having -0.75 to 0.75 directionality Δr computed by the following equation: Δr=(r0+r99)/2-r45 (wherein r0 is r-value (Lankford value, the same applies to the following) measured by performing a tensile test in a direction parallel to the rolling direction; r90 is r-value measured by performing a tensite test in a direction perpendicular to the rolling direction; and r45 is r-value measured by performing a tensile test in a direction forming an angle of 45 deg. with the rolling direction). It is preferable to regulate the average grain size of this aluminum alloy sheet to <=150 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an aluminum alloy plate for a secondary battery case and a secondary battery case formed by molding the aluminum alloy plate.

[0002]

2. Description of the Related Art Rechargeable batteries are used as a power source for portable devices such as notebook computers and mobile phones.
It is increasingly important to be small and lightweight.
The battery case that stores the electrode body is also more often a prismatic case with a higher filling density than a cylindrical one,
Regarding the material of the case, a battery case made of a lightweight aluminum alloy has attracted attention instead of the conventional battery case made of iron or stainless steel.

Conventionally, as an aluminum alloy for a battery case, 3000 series (Al) containing Mn as a main component has been used.
-Mn-based) aluminum alloys are widely used (Japanese Patent Application Laid-Open No. 8-329908), and a plate material of this alloy (for example, a H16 temper having a thickness of about 0.8 to 1.0 mm) is used.
For example, after drawing and ironing into a rectangular cylindrical can shape having dimensions of about 28 mm in length, 6 mm in width, 45 mm in height, and about 0.5 mm in side wall thickness, forming the body of the case, storing the electrode body, A secondary battery is made by attaching a lid made of material by welding or caulking.

However, currently used Al-
Mn-based alloys are excellent in formability, but have relatively low strength. Especially when a rectangular cylindrical battery case is used, blisters are likely to occur, and the battery housing space of equipment is designed to be large enough to account for blisters. This causes inconvenience in downsizing the equipment.

[0005] Swelling is caused by gas generation from the electrolyte due to self-heating during charging when charging takes a long time, or when the device is placed in the sun, for example, in a parked car in summer. Alternatively, this is a phenomenon in which the case expands due to an increase in the internal pressure of the battery due to thermal expansion of gas remaining inside. Although the swelling of the case itself decreases with a decrease in the internal pressure, if the swelling state is left for a long time or if the swelling occurs at a high temperature, the case does not return completely and the case is deformed.

There is a method of increasing the thickness by increasing the thickness of the material constituting the battery case in order to increase the blister resistance, but this is disadvantageous in terms of weight reduction. As an aluminum alloy for a battery case with improved strength, Mn is 0.8 to
1.5%, 0.8 to 1.5% of Mg, 0.1 to 0.1% of Cu
Although an aluminum alloy containing 0.4% and 0.1 to 0.4% of Si has been proposed (Japanese Patent Application Laid-Open No. 9-316580), even when a battery case is formed from this alloy material,
In many cases, sufficient blister resistance is not always obtained.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned conventional problems in the aluminum alloy material for a secondary battery case, the present invention has been made to solve the problem of a battery case formed from an aluminum alloy plate as a material of the battery case. The effects of various properties, internal structure, and alloy components of aluminum alloy sheets on swelling resistance are the result of repeated experiments and studies. The purpose is to have excellent strength, formability, and swelling resistance. It is an object of the present invention to provide an aluminum alloy plate for a secondary battery case, which has an increased resistance, a method of manufacturing the same, and a secondary battery case.

[0008]

According to a first aspect of the present invention, there is provided an aluminum alloy plate for a secondary battery case, wherein the directionality Δr calculated by the following equation is -0.75. As mentioned above, it is characterized by being made of an aluminum alloy plate of +0.75 or less. Δr = (r ₀ + r ₉₀ )
/ 2-r ₄₅ , where r ₀ is an r value measured by performing a tensile test in a direction parallel to the rolling direction, r ₉₀ is an r value measured by performing a tensile test in a direction perpendicular to the rolling direction,
r ₄₅ is an r value measured by performing a tensile test in a direction at 45 ° to the rolling direction.

The aluminum alloy plate for a secondary battery case according to claim 2 is characterized in that, in addition to the structure of claim 1, the average crystal grain size of the aluminum alloy plate is 150 μm or less.

The aluminum alloy plate for a secondary battery case according to claim 3 is the same as the structure of claim 1 or 2, wherein the aluminum alloy plate has Cu: 0.20 to 1.0%, Mn:
It is characterized by containing 0.5 to 2.0% and having a composition consisting of the balance of Al and impurities.

According to a fourth aspect of the present invention, the aluminum alloy plate for a secondary battery case is the same as the first or second aspect, except that the aluminum alloy contains 0.20 to 1.0% of Cu and 0.1 to 0.1% of Mn.
5 to 2.0%, Mg: 0.20% or less, the balance A
1 and impurities.

The aluminum alloy plate for a secondary battery case according to claim 5 is characterized in that, in addition to the constitution of claim 1 or 2, the aluminum alloy further contains 0.4 to 1.0% of Si. I do.

The aluminum alloy plate for a secondary battery case according to claim 6 is the aluminum alloy according to any one of claims 3 to 5, wherein Fe as an impurity is 0.7% or less, and
r is 0.05% or less, Ti is 0.05% or less, and B is 10% or less.
It is characterized by being limited to 0 ppm or less and Zn to 0.5% or less.

Further, a method of manufacturing an aluminum alloy sheet for a secondary battery case according to the present invention is characterized in that the ingot of the aluminum alloy according to any one of claims 3 to 6 is hot-rolled and cold-rolled to obtain a sheet material. In doing so, the homogenization treatment is performed at 550 ° C. or higher, and intermediate annealing is performed before the final cold rolling to be recrystallized.
It is characterized by final cold rolling.

Further, the secondary battery case according to the present invention is
The aluminum alloy plate according to any one of claims 1 to 6 is formed into a can shape.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The aluminum alloy plate for a secondary battery case of the present invention comprises an aluminum alloy plate having a directionality Δr calculated by the following equation of not less than -0.75 and not more than +0.75. This is very important. Δr = (r ₀ +
r ₉₀ ) / 2−r ₄₅ , where r ₀ is an r value measured by performing a tensile test in a direction parallel to the rolling direction, and r ₉₀ is measured by performing a tensile test in a direction perpendicular to the rolling direction. The r value and r ₄₅ are r values measured by conducting a tensile test in a direction at 45 ° to the rolling direction.

When the directionality (Δr) is out of this range,
The blister resistance tends to decrease, and it becomes difficult to obtain a desired shape after molding. In addition, the ears generated by the molding process increase, and the margin for trimming increases, resulting in a decrease in product yield and an increase in cost. In particular, when Δr exceeds +0.75, workability is significantly reduced.

The average grain size of the aluminum alloy sheet of the present invention is preferably 150 μm or less, more preferably 100 μm or less. When the average grain size exceeds 150 μm,
Not only the swelling resistance is reduced, but also the moldability is reduced, the surface is roughened at the time of molding, and defects such as flow marks are easily caused.

In the present invention, as long as the directionality (Δr) or the directionality (Δr) and the average crystal grain size are within a predetermined range, any aluminum alloy can be used regardless of the composition of the aluminum alloy. However, in the present invention, particularly, in the aluminum alloy, the following composition (1)
It is preferable to use an aluminum alloy having the following (3).

The composition (1) is Cu: 0.20 to 1.0
%, Mn: 0.5 to 2.0%, with the balance being Al and impurities. Cu functions to increase the strength and the blister resistance, but if the Cu content is less than 0.20%, the blister resistance is not sufficient, and the grain refinement and directionality (Δr)
Function cannot be sufficiently obtained for the homogenization. If the Cu content exceeds 1.0%, the strength is improved, but the moldability and the weldability are undesirably reduced. In particular, when the moldability is reduced, it is difficult to form the battery case by impact molding or press molding. A more preferred content of Cu is in the range of 0.4 to 0.7%.

Mn also functions to increase the strength and the blister resistance, but if the Mn content is less than 0.5%, the strength is low and the blister resistance becomes insufficient, and the Mn content exceeds 2.0%. , The strength is high, but the moldability is undesirably reduced. In addition, a huge crystallized substance is generated and dispersed in the matrix, which hinders the thinning of the case and the rollability of the sheet material. M
The more preferable content range of n is 0.7-1.7%.

The composition (2) contains Cu: 0.20 to 1.0.
%, Mn: 0.5 to 2.0%, Mg: 0.20% or less, with the balance being Al and impurities. Cu and M
The meaning of n-containing and the reasons for limitation are as described above. M
g functions to increase strength and blister resistance, but M
If the g content exceeds 0.20%, the formability and weldability are reduced. When the lid is joined to the body of the battery case by welding, a decrease in weldability impairs the joinability, so it is necessary to suppress the Mg content to 0.20% or less. When mounting by means such as caulking, workability is not significantly reduced.
Up to 5% Mg may be included.

The composition (3) comprises 0.4 to 1.0% of Si in addition to the compositions (1) and (2). Si is
Works to increase strength and blister resistance, but 0.4%
If it is less than the above, the strength is low and it is difficult to obtain sufficient blister resistance. Si
When the content exceeds 0.6%, the strength is increased, but a huge compound is easily generated in the matrix, and the moldability is deteriorated. This is not preferable for reducing the thickness of the case.

In an aluminum alloy having the compositions (1) to (3), Fe as an impurity is 0.7% or less, Cr is 0.05% or less, Ti is 0.05% or less, and B
Is preferably limited to 100 ppm or less, and Zn is limited to 0.5% or less. By this impurity limitation, the directionality (Δr) of the aluminum alloy plate becomes more uniform.

The aluminum alloy plate for a secondary battery case according to the present invention is formed by ingot-forming the aluminum alloy according to any one of claims 3 to 6 by, for example, continuous casting, and the obtained ingot is subjected to face milling. After removing the non-uniform layer on the lump surface, it is subjected to a homogenization treatment, and then manufactured by hot rolling and cold rolling. After the ingot has been homogenized, the surface may be cut and re-heated to perform hot rolling.

The feature of the present invention is -0.75 or more, +
In order to obtain a directionality Δr of 0.75 or less, in the above-described manufacturing process, homogenization treatment is performed at 550 ° C. or more, and then hot rolling, cold rolling, intermediate annealing, and final cold rolling are performed. Is preferred. Also, after the ingot is homogenized, the surface may be cut, re-heated and hot-rolled,
In this case, the reheating temperature and the holding time are not so important, but they do not impair the effect of the homogenization treatment.
It is desirable not to hold for a long time (for example, 5 hours or more) at a temperature of 550 ° C. or less. Furthermore, in order not to impair the effect of the homogenization treatment, cooling is performed during hot rolling.
It is even better to reduce the time during which the material is exposed to a temperature range between 50 ° C. and less than 550 ° C.

In order to obtain an average crystal grain size of 150 μm or less, it is necessary to carry out intermediate annealing before the final cold rolling to recrystallize, to reduce the average crystal grain size to 150 μm or less, and to perform final cold rolling. Is preferred. In order to obtain a fine grain size within the scope of the present invention, it is preferable to interpose a cold rolling step after hot rolling and before intermediate annealing.
L) is preferably applied. In addition, the effect of crystal grain refinement can be achieved by performing the hot rolling while cooling.

[0028]

Hereinafter, examples of the present invention will be described in comparison with comparative examples. Example 1 An ingot of an aluminum alloy having a composition shown in Table 1 was formed by semi-continuous casting, and the obtained ingot (thickness: 500 mm) was chamfered to remove an uneven layer on the surface. 1 for the temperature
Perform a homogenization treatment by heating and holding for 0 hours, cool to a temperature of 550 ° C., immediately perform hot rolling, and obtain a thickness of 6.4 m.
m plate material.

Subsequently, a thickness of 2.5 m was obtained by cold rolling.
m, a part of which was rolled to a thickness of 2.3 mm, subjected to intermediate annealing by applying continuous annealing, and then finally cold-rolled to a thickness of 1.0 mm.

The obtained plate material was subjected to a tensile test to measure the directionality Δr, and the surface was observed with a microscope to determine the average crystal grain size (average crystal grain size observed from the plate material surface, the same applies hereinafter). In addition, moldability, bonding properties, and blister resistance were evaluated by the following methods. Formability: Outer dimensions, length 28mm, width 6mm, height 45
mm, side wall thickness 0.5 mm, bottom wall thickness 1 mm, DI processing (drawing and ironing) to form a fuselage for a secondary battery case, and observe for cracks, rough skin, etc. Then, the moldability is evaluated.

Bondability: A3
A lid formed from a 003 alloy plate (thickness: 1 mm) is joined by laser welding, the presence or absence of a defect in the joint is observed, and the joinability is evaluated from the soundness of the joint.

Swelling resistance: The case where the lid is joined in accordance with the above-mentioned method is heated at a temperature of 80.degree.
After pressurizing to 5 kgf / cm ² and holding for 24 hours, naturally cool to room temperature, measure the difference in outer dimensions of the case before and after the test (after the test-before the test), and evaluate the blister resistance based on the difference. did.

Table 2 shows the directionality Δr, average crystal grain size, moldability, bonding property, blister resistance, and average recrystallized grain size after intermediate annealing of each test material. As can be seen from Table 2, all of the test materials according to the present invention exhibited good moldability without cracking or roughening in the moldability test, the joint was sound, and the blister was small (difference less than 1 mm). As a material for a secondary battery case.

[0034]

[Table 1]

[0035]

[Table 2] << Table Note >> Test materials No.5 and No.6 were rolled to 2.3mm thickness by intermediate cold rolling. Moldability ○: No problem Joinability ○: No problem

Comparative Example 1 An ingot of an aluminum alloy having the composition shown in Table 1 and alloys A and C of Example 1 were formed by semi-continuous casting, and the obtained ingot (thickness: 500 mm) was chamfered. After removing the non-uniform layer on the surface, the sheet was heated to a temperature of 500 ° C. without being subjected to the homogenization treatment, and immediately hot-rolled to obtain a plate material having a thickness of 6.4 mm or 2.5 mm. For some, see Example 1.
Up to hot rolling was performed under the same conditions as described above.

Subsequently, the hot-rolled material having a thickness of 6.4 mm was rolled to a thickness of 2.5 mm by cold rolling. Then, after performing intermediate annealing by applying continuous annealing together with a hot-rolled material having a thickness of 2.5 mm, a thickness of 1.0 mm
Until the final cold rolling. In addition, the test piece was sampled from the sheet material after the intermediate annealing, the surface thereof was observed with a microscope, and the average recrystallized grain size was measured.

With respect to the obtained plate material, as in Example 1,
A tensile test was performed to measure the directionality Δr, the surface was observed with a microscope, and the average recrystallized grain size was measured. Example 1
The moldability, bondability, and blister resistance were evaluated in the same manner as described above. Table 4 shows the results.

[0039]

[Table 3]

[0040]

[Table 4] << Table Note >> Formability ○: No problem △: Micro crack (skin roughening) Joining property ○: No problem ×: Cracking occurred at welded part Swelling resistance Difference in case thickness before and after test (smaller the better the performance)

Test material No. No. 7 is an unsuitable production condition (intermediate annealing immediately after hot rolling without performing homogenization treatment) and the directionality Δr and the average crystal grain size are out of the range of the present invention. And the moldability is inferior. Test material No. In No. 8, the production conditions were unsuitable (no homogenization treatment), and as a result, the directionality Δr was out of the range of the present invention, so that the blister resistance was poor. Test material N
o. No. 9 has a low Mn content, so that the material strength is low and the blister resistance is slightly low. Test material No. 10 is Cu
Due to the small amount, the material strength is low, and the blister resistance is slightly low.

Test material No. Sample No. 11 has a low material strength due to a small amount of Cu and Mn, and has a slightly low blister resistance. Test material No. In No. 12, the Cu content was low and the production conditions were unsuitable (intermediate annealing immediately after hot rolling without performing homogenization treatment). As a result, the average crystal grain size exceeded 150 μm. Gender is slightly lower. Test material No. No. 13 is inferior in blister resistance because Δr is out of the range of the present invention because the amounts of Cu and Mn are small and the production conditions are unfriendly. Test material N
o. In No. 14, since the amount of Mg was large, cracks were generated in laser welding, and a case could not be manufactured. Therefore, the blister test could not be performed. The test material No.
Nos. 9 to 11; Nos. 13 and 14 were performed under the same conditions as in Example 1 up to the hot rolling.

[0043]

According to the present invention, strength and moldability are excellent.
In addition, an aluminum alloy plate for a secondary battery case having enhanced blister resistance, a method for manufacturing the same, and a secondary battery case are provided. By forming the aluminum alloy plate into a case, the thickness can be further reduced. Therefore, when secondary battery cases having the same outer dimensions are manufactured, the inner volume can be increased, the capacity of the battery can be increased, and the usable time of an electric appliance using the battery can be extended. In the case where secondary batteries having the same capacity are manufactured, further reduction in size and weight can be achieved.

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Claims (8)

[Claims] 1. An aluminum alloy plate for a secondary battery case, comprising an aluminum alloy plate having a directionality Δr calculated by the following equation of −0.75 or more and +0.75 or less. Δr = (r ₀ + r ₉₀ ) / 2−r ₄₅ , where r ₀ is an r value (Langford value, hereinafter the same) measured by conducting a tensile test in a direction parallel to the rolling direction;
r ₉₀ is an r value measured by performing a tensile test in a direction perpendicular to the rolling direction, and r ₄₅ is an r value measured by performing a tensile test in a direction at 45 ° to the rolling direction. 2. An Alminium alloy plate having an average crystal grain size of 15
The aluminum alloy plate for a secondary battery case according to claim 1, wherein the thickness is 0 µm or less. 3. An aluminum alloy plate having a Cu content of 0.20
To 1.0% (% by weight, the same applies hereinafter), Mn: 0.5 to 2.
3. The aluminum alloy sheet for a secondary battery case according to claim 1, wherein the aluminum alloy sheet contains 0% and has a composition consisting of a balance of Al and impurities. 4. An aluminum alloy plate having a Cu: 0.20
-1.0%, Mn: 0.5-2.0%, Mg: 0.20
The aluminum alloy plate for a secondary battery case according to claim 1, wherein the aluminum alloy plate contains a composition containing not more than 0% (excluding 0%, the same applies hereinafter) and the balance being Al and impurities. 5. The composition of the aluminum alloy sheet further includes S
5. The aluminum alloy plate for a secondary battery case according to claim 3, wherein i: 0.4 to 1.0% is contained. 6. 6. An alloy containing 0.7% or less of Fe as an impurity,
r is 0.05% or less, Ti is 0.05% or less, and B is 10% or less.
The aluminum alloy plate for a secondary battery case according to any one of claims 3 to 5, wherein 0 ppm or less and Zn are limited to 0.5% or less. 7. When the ingot of the aluminum alloy according to any one of claims 3 to 6 is hot-rolled and cold-rolled into a sheet, homogenization treatment is performed at 550 ° C. or more, A method for producing an aluminum alloy plate for a secondary battery case, comprising performing intermediate annealing before rolling, recrystallizing the material, and performing final cold rolling. 8. A secondary battery case obtained by forming the aluminum alloy plate according to claim 1 into a can shape.