JP2002339049A - Manufacturing method of aluminum alloy plate for secondary battery case - Google Patents

Abstract

(57) [Problem] To provide a method of manufacturing an aluminum alloy plate for a secondary battery case having high strength and excellent press formability. SOLUTION: Mn is 0.6 to 1.5% by weight, Mg is 0.5% by weight or less, Cu is 0.1 to 0.6% by weight, Si
0.2-0.8% by weight, Fe 0.2-1.0% by weight
A method for producing an aluminum alloy sheet which is obtained by melting, casting, homogenizing, hot-rolling, cold-rolling, intermediate annealing, and final cold-rolling an aluminum alloy containing each and the remaining unavoidable impurities and Al. In the homogenization treatment, the first stage is maintained at 170 to 270 ° C. for 1 hour or more, and the second stage is heated to 400 to 560 ° C.
The above problem is solved by a method of manufacturing an aluminum alloy plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an aluminum alloy plate for a secondary battery case, which is used as a power source for a notebook personal computer, a mobile phone, and the like, and more particularly, to an aluminum alloy plate for a lithium ion secondary battery case. About the method.

[0002]

2. Description of the Related Art A secondary battery is used as a power source for portable equipment such as a notebook personal computer and a portable telephone, and is required to be small and lightweight. As one of the demands, thinning of a secondary battery case is being studied.

Since the secondary battery case is usually formed by a multi-stage press, the case material is required to have good press formability. For this reason, conventionally, pure aluminum-based (JIS-1000-based) or Al-Mn-based JI
A relatively soft material such as an S-3003 alloy was often used for a secondary battery case.

[0004]

A secondary battery is manufactured by putting an electrode body in a case made of the above-mentioned material, and then sealing the cover by welding or caulking. The secondary battery thus manufactured is used in a mobile phone or the like. When charging after discharging, the temperature inside the case increases, and the pressure inside the case increases. In this case, there is a problem that a case made of the above-described relatively soft case material is greatly swollen. In order to suppress this swelling, a high-strength secondary battery case material is required.

The present invention has been accomplished in view of the above problems, and an object of the present invention is to provide a method for producing an aluminum alloy sheet having high strength and excellent press formability.

[0006]

According to the first aspect of the present invention, 0.6 to 1.5% by weight of Mn and 0.5% by weight of Mg are used.
Hereinafter, 0.1 to 0.6% by weight of Cu and 0.2 to 0.6% by weight of Si
0.8 wt%, Fe 0.2-1.0 wt%, respectively, dissolves aluminum alloy consisting of unavoidable impurities and Al, casting, homogenizing, hot rolling, cold rolling,
In the method for manufacturing an aluminum alloy sheet obtained by performing intermediate annealing and final cold rolling to obtain a sheet material, the homogenization treatment is performed at 170 to
A method for producing an aluminum alloy plate for a secondary battery case, comprising holding at 270 ° C. for at least one hour and then heating to 400 to 560 ° C.

According to a second aspect of the present invention, in the method for manufacturing an aluminum alloy plate for a secondary battery case according to the first aspect, the aluminum alloy further contains 0.05 to 0.05% of Zr.
It is characterized by containing 0.2% by weight.

According to the method for producing an aluminum alloy plate for a secondary battery case of the present invention, a homogenization treatment in which the first stage is maintained at 170 to 270 ° C. for 1 hour or more and the second stage is heated to 400 to 560 ° C. As a result, the metal compound precipitates in the aluminum alloy plate, and the strength increases. As a result, an aluminum alloy plate having high strength and excellent press formability can be manufactured, and thus the manufactured aluminum alloy plate is suitable for use in a secondary battery case.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing an aluminum alloy plate for a secondary battery case according to the present invention will be described.

In the present invention, Mn is contained in an amount of 0.6 to 1.5% by weight,
0.5% by weight or less of Mg, 0.1-0.6% by weight of Cu, 0.2-0.8% by weight of Si, and 0.2-1.
Aluminum alloy sheet containing 0 wt% each and dissolving, casting, homogenizing, hot rolling, cold rolling, intermediate annealing, and final cold rolling the aluminum alloy consisting of aluminum and inevitable impurities as the rest The production method is characterized in that the homogenization treatment is carried out in the first stage at 170 to 270.
C. for 1 hour or more, and heated to 400-560 ° C. in the second stage.

Further, in the method for manufacturing an aluminum alloy plate for a secondary battery case of the present invention, the above-mentioned aluminum alloy may further contain 0.05 to 0.2% by weight of Zr.

The homogenization treatment is performed for the purpose of eliminating segregation or preserving an equilibrium composition at the treatment temperature to precipitate excess elements and stabilize the ingot structure.
In the present invention, first, as the first stage processing, 170
Hold at 270 ° C. for 1 hour or more. By such a treatment, Mg ₂ Si as a metal compound is precipitated in the cast aluminum alloy. When Mg is not contained in the aluminum alloy, Si precipitates. Next, as a second stage treatment, heating is performed in the range of 400 to 560 ° C. By such processing, Mg ₂ Si or Si precipitated in the first processing is used as a nucleus (nucleation site),
Al-Mn-Fe-Si-based metal compounds are finely dispersed and precipitated. By precipitating these metal compounds in the aluminum alloy, the strength of the manufactured aluminum alloy plate can be improved.

If the temperature of the first-stage homogenization treatment is lower than 170 ° C., the size of the precipitated Mg ₂ Si or Si becomes small, and the Mg ₂ Si or Si is made of Al—Mn—F.
It may not be a site for nucleation of the e-Si-based metal compound. In addition, the temperature of the first-stage homogenization treatment is 270 ° C.
By weight, precipitated or become Mg ₂ Si or distribution density of Si is low and, Mg ₂ Si or Si may not precipitated. In these cases, the Al-Mn-Fe-Si-based metal compound cannot be deposited at a high density even when subsequently heated at 400 to 560 ° C. It is more preferable that the temperature of the first-stage homogenization treatment is in the range of 190 to 260 ° C.

If the holding time of the first-stage homogenization treatment is less than 1 hour, Mg ₂ Si or Si may not be sufficiently precipitated. Here, the upper limit value of the holding time is not particularly defined, but it is appropriate to set the upper limit value to 20 hours in consideration of the effect of precipitation of Mg ₂ Si or Si and the cost required for manufacturing an aluminum alloy plate. .

When the temperature of the second-stage homogenization treatment is lower than 400 ° C., an Al—Mn—Fe—Si-based metal compound having Mg ₂ Si or Si precipitated in the first stage as nucleation sites is deposited. And the temperature of the second stage homogenization treatment is 5
When the temperature exceeds 60 ° C., the Al—Mn—Fe—Si-based metal compound grows greatly, and Al—Mn—Fe—Si
The distribution density of the base metal compound is significantly reduced. It is more preferable that the temperature of the second-stage homogenization treatment is in the range of 440 to 550 ° C.

The holding time of the second-stage homogenization treatment is not particularly limited, but is preferably 2 hours or more. A for more than 2 hours
The l-Mn-Fe-Si-based metal compound can be sufficiently precipitated. More preferably, it is 5 hours or more.
Further, as to the upper limit value, it is appropriate to set the upper limit value to 20 hours, when the effect of depositing the metal compound and the cost are weighed in the same manner as the holding time in the first-stage homogenization treatment.

When only the first-stage homogenization treatment is performed, only Mg ₂ Si or Si is deposited.

When only the second-stage homogenization treatment is performed, the Al—Mn—Fe—Si-based metal compound precipitates, but the distribution density of the metal compound is higher than when the first-stage homogenization treatment is performed. Becomes lower.

In the method of manufacturing an aluminum alloy plate for a secondary battery case according to the present invention, a higher strength aluminum alloy plate can be manufactured by performing such a homogenization treatment at the time of manufacturing the aluminum alloy plate. .

Next, the component composition of the aluminum alloy applied to the method for manufacturing an aluminum alloy plate for a secondary battery case of the present invention will be described. In order to obtain the effect of the homogenization treatment described above, the following component compositions are required.

The composition of the aluminum alloy applied to the present invention is as follows: Mn is 0.6 to 1.5% by weight, Mg is 0.5% by weight or less, Cu is 0.1 to 0.6% by weight, Si is 0.2 ~
It contains 0.8% by weight and 0.2 to 1.0% by weight of Fe, and the balance consists of unavoidable impurities and Al. In the method for producing an aluminum alloy plate for a secondary battery case of the present invention, the intended object can be achieved by applying an aluminum alloy having such a composition.

Mn increases the strength and refines the crystal grains, thereby contributing to the improvement of press formability. If the Mn content is less than 0.6% by weight, the effect becomes insufficient, and
If the content is more than 1.5% by weight, coarse crystals are likely to be formed at the time of casting, and are dispersed in a matrix to deteriorate press formability. The preferred range of the Mn content is 0.1.
8 to 1.3% by weight.

Mg increases the strength. Mg content is 0.
Exceeding 5% by weight is not preferable because the weldability at the time of joining the lid to the body after molding the case is impaired. The Mg content may be 0% by weight, and the lower limit is not particularly defined. However, the strength is higher in those that do, than in those that do not. A preferred range of the Mg content is 0.1 to 0.4% by weight.

Cu increases the strength. Cu content is 0.
When the content is less than 1% by weight, the effect is insufficient, and when the Cu content exceeds 0.6% by weight, the strength is further improved,
Press formability is significantly reduced. A preferable range of the Cu content is 0.2 to 0.5% by weight.

Si enhances the strength. Si content is 0.
If the content is less than 2% by weight, the effect becomes insufficient, and if the Si content exceeds 0.8% by weight, coarse crystals are easily formed at the time of casting, and press formability is reduced. The preferable range of the Si content is 0.2 to 0.7% by weight.

Fe increases the strength. Fe content is 0.
If the content is less than 2% by weight, the effect is insufficient, and if the Fe content exceeds 1.0% by weight, coarse crystals are easily formed at the time of casting, and press formability is reduced. The preferable range of the Fe content is 0.3 to 0.9% by weight.

When the aluminum alloy having the above composition is applied to the method for manufacturing an aluminum alloy sheet for a secondary battery case of the present invention, the manufactured aluminum alloy sheet for a secondary battery case has excellent strength and press formability. It will be.

Further, Zr is added to the above component composition in an amount of 0.
In the range of 0.5 to 0.2% by weight. Zr is
Strength is enhanced and the crystal grains are refined to contribute to the improvement of press formability. When the Zr content is less than 0.05% by weight, the effect is insufficient, and when the Zr content exceeds 0.2% by weight, coarse crystals are easily formed at the time of casting, and press formability is deteriorated. I do. A preferable range of the Zr content is 0.08 to 0.15% by weight.

The component composition of the aluminum alloy sheet manufactured by the method for manufacturing an aluminum alloy sheet for a secondary battery case of the present invention is also included in the above-mentioned composition.

The method for producing an aluminum alloy sheet of the present invention comprises the steps of melting, casting, homogenizing, hot rolling, cold rolling, intermediate annealing, and final cold rolling of an aluminum alloy having the above-mentioned composition. Have The present invention is characterized by a homogenization treatment, and the other methods are conventionally applied to melting, casting, hot rolling, cold rolling, intermediate annealing, and final cold rolling.

The heating rate in the intermediate annealing step is 10 to 2
Preferably, the temperature is 50 ° C./sec, the annealing temperature is 450 to 580 ° C., the holding time is 5 to 60 seconds, and the cooling rate is 20 to 200 ° C./sec.

If the heating rate is lower than 10 ° C./sec, the stored energy introduced during the cold rolling is released.
The recrystallization nucleation rate decreases, and the average crystal grain size after annealing increases, and as described later, the average crystal grain size does not become 25 μm or less. If the heating rate exceeds 250 ° C./sec, expensive equipment needs to be introduced, and the production cost increases.

If the annealing temperature is lower than 450 ° C., the time required for the recrystallization to be completed becomes longer, which increases the production cost and produces elongated and coarse crystal grains. When the annealing temperature is higher than 580 ° C., recrystallization is completed in a short time and grain growth occurs, so that crystal grains become large.

If the holding time is shorter than 5 seconds, recrystallization is not completely completed, and fine crystal grains cannot be obtained. If the holding time is longer than 60 seconds, crystal grains grow, and a fine grain structure having an average crystal grain size of 25 μm or less, which will be described later, cannot be obtained.

If the cooling rate is lower than 20 ° C./sec, Cu and Mg are precipitated during cooling, which is not preferable because the strength is lowered. When the cooling rate exceeds 200 ° C./sec, capital investment for cooling increases and production cost increases.

As described above, the heating rate in the intermediate annealing step
By setting the annealing temperature, the holding time, and the cooling rate within the above ranges, the average crystal grain size does not become larger than 25 μm, and an aluminum alloy sheet for a secondary battery case having excellent press moldability and strength is manufactured. be able to.

Further, the rolling reduction in the final cold rolling is 15 to 8
It is preferable to control to 5%. If the rolling reduction is less than 15%, sufficient work hardening cannot be obtained, and the strength decreases. When the rolling reduction exceeds 85%, further work hardening cannot be obtained so much, and press formability deteriorates.

Here, the strength means a tensile strength obtained by a tensile test. When the strength is sufficiently high, the temperature inside the secondary battery case rises when charging the secondary battery,
The case can be prevented from bulging when the pressure increases. The aluminum alloy plate of the present invention solves the problem of swelling of a conventional case.

The aluminum alloy sheet produced by the production method of the present invention preferably has an average crystal grain size of 25 μm or less in a cross section in the rolling direction, determined by the following method. A more preferred range is 20 μm or less.

The average crystal grain size of the present invention is determined by SEM (Scanni
ng Electron Microscope (scanning electron microscope) attached to a crystal orientation observation device (commonly called EBSP (Electron Back-S
The grain boundary of the cross section in the rolling direction of the aluminum alloy sheet is observed by a cater diffraction pattern (reflection electron Kikuchi line diffraction pattern)), and the cross-sectional area of the crystal grains is measured and determined by analysis software. The measurement of the crystal orientation is performed by dividing the entire observation region into tens of thousands to hundreds of thousands of points vertically and horizontally, one point at a time. In general, a crystal grain is defined as a crystal grain having a certain number or more (for example, 10 or more) points in a region surrounded by a grain boundary having a misorientation of 15 ° or more. The crystal grain size is calculated by obtaining the area of the crystal grain from the number of points in the crystal grain and the area per point, and considering the area as the area of a circle. As described above, the grain size of each crystal grain is obtained, and the average value is calculated to be the average crystal grain size.

When the average crystal grain size exceeds 25 μm, press formability and laser weldability are reduced. Although the lower limit of the average crystal grain size is not particularly defined, the current average aluminum plate manufacturing technology assumes that the minimum average crystal grain size that can be manufactured stably at low cost is about 3 μm. Therefore, if an aluminum alloy plate having an average crystal grain size of 3 μm or less is to be manufactured, enormous capital investment and complicated manufacturing steps are required, and the manufacturing cost is greatly increased. Therefore, in the present invention, from the viewpoint of production, the lower limit of the average crystal grain size is set to 3
μm.

The aluminum alloy sheet produced by the production method of the present invention preferably has a tensile strength of 200 MPa or more, as determined by a tensile test,
It is more preferably at least a. When the tensile strength is within this range, sufficient swelling resistance can be imparted to the secondary battery case formed with the aluminum alloy plate of the present invention.
Although the upper limit of the tensile strength is not particularly defined, it depends on the properties of the aluminum alloy sheet and the manufacturing method. Therefore, the current aluminum sheet manufacturing technology can be manufactured stably at low cost, but the upper limit of the tensile strength is about 400 MPa. ,Preferably,
It is 300 MPa.

[0043]

EXAMPLES (Examples 1 to 9) Table 1 shows the component compositions of the aluminum alloy sheets of Examples 1 to 9 manufactured by the method for manufacturing an aluminum alloy sheet of the present invention. The unit in Table 1 is% by weight. An aluminum alloy blended so that the manufactured aluminum alloy plate had the component composition shown in Table 1 was melted, cast by semi-continuous casting, and the obtained ingot was face-faced. Thereafter, a first-stage homogenization treatment was performed at 190 ° C. for 2 hours, and then a second-stage homogenization treatment was performed at 540 ° C. for 5 hours. Then, cool down to 400 ° C,
Hot rolling was immediately performed to obtain a plate having a thickness of 7 mm. Subsequently, the steel sheet was rolled to a thickness of 0.6 mm by cold rolling, and subjected to intermediate annealing under the conditions shown in Table 2. After that, thickness 0.4
mm. The rolling reduction in the final cold rolling was 33%. Thus, the aluminum alloy plates of Examples 1 to 9 were manufactured.

Comparative Examples 1 to 5 Comparative Examples 1 to 9 were performed in the same manner as in Examples 1 to 9 except that the manufactured aluminum alloy sheets had the component compositions shown in Table 1.
5 was produced. As a feature of each comparative example, comparative example 1 has a high aluminum purity, comparative example 2 has a high Si content, comparative example 3 has a high Mg content, comparative example 4 has a high Cu content, and comparative example 5 has a high Cu content. High Zr content.

[0045]

[Table 1]

[0046]

[Table 2]

(Evaluation of Tensile Strength and Press Formability, etc.) The tensile strength was determined according to JIS Z 2201-5 based on the obtained plate material.
No. test specimens were collected and subjected to a tensile test according to the method specified in JIS Z 2241, and examined.

The average crystal grain size was obtained from PHILIPS SE
The crystal orientation data measured at point intervals of 0.2 μm using a TSL EBSP system attached to M (XL30Fe) was obtained by TSL OIM2.8 analysis software. A crystal grain having 10 or more points in a region surrounded by a grain boundary having a misorientation of 15 ° or more was defined as a crystal grain.

Regarding the press formability, a punch having a diameter of 33 mm and a shoulder R of 4.5 mm, and a diameter of 57.75 to 69.3 mm were used.
A deep drawing test was performed using a plank of No. 1 and evaluated by a limit drawing ratio. If the limit aperture ratio is 1.9 or more,
Those having a value of less than 1.9 were evaluated as x.

(Evaluation Results) Table 3 shows the evaluation results of the tensile strength, average crystal grain size and press formability of Examples 1 to 9 and Comparative Examples 1 to 5.

As shown in Table 3, all of the sheets of Examples 1 to 9 produced according to the present invention had a high tensile strength and a small average crystal grain size of about 10 μm. And good press moldability was shown. Thus, in Examples 1 to 9, an aluminum alloy plate excellent in press formability and strength can be manufactured, and is suitable as an aluminum alloy plate for a secondary battery case.

On the other hand, in the sheet materials of Comparative Examples 1 to 5 deviating from the alloy composition range of the present invention, the strength was considerably lower than 200 MPa or the average crystal grain size was large. And the press formability was poor. From this, Comparative Examples 1 to 5
The aluminum alloy plate was inferior to the present invention as an aluminum alloy plate for a secondary battery case.

[0053]

[Table 3]

(Examples 10 to 12) In the method of Examples 1 to 9, the temperature was raised in the intermediate annealing step, using an aluminum alloy mixed so that the manufactured aluminum alloy sheet had the composition of Example 2. Speed of 100 ° C / sec, annealing temperature of 50
The aluminum alloy plates of Examples 10 to 12 were manufactured at 0 ° C., a holding time of 25 seconds, a cooling rate of 150 ° C./second, and the conditions of the homogenization treatment as shown in Examples 10 to 12 of Table 4.

(Comparative Examples 6 to 8) The aluminum alloys of Comparative Examples 6 to 8 were produced in the same manner as in Examples 10 to 12 except that the homogenizing treatment was performed under the conditions shown in Table 4. Boards were manufactured.

[0056]

[Table 4]

(Evaluation Results) Examples 1 to 9 and Comparative Examples 1 to
As in the case of No. 5, evaluation of tensile strength, press formability, and the like was performed. Table 5 shows the evaluation results of the tensile strength, average crystal grain size, and press formability of Examples 10 to 12 and Comparative Examples 6 to 8. In Examples 10 to 12, an aluminum alloy plate excellent in press formability and strength could be manufactured.

[0058]

[Table 5]

[0059]

As described above, according to the method for manufacturing an aluminum alloy sheet of the present invention, an aluminum alloy sheet having excellent press formability and strength can be manufactured. Suitable for use in battery cases.

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Claims (2)

[Claims] 1. Mn 0.6-1.5% by weight, Mg 0.5% or less, Cu 0.1-0.6% by weight, Si
0.2-0.8% by weight, Fe 0.2-1.0% by weight
Dissolve, cast, homogenize, hot-roll, dissolve aluminum alloy consisting of unavoidable impurities and Al
In the method for producing an aluminum alloy sheet to be a sheet material by cold rolling, intermediate annealing, and final cold rolling, the homogenization treatment is performed by maintaining the temperature at 170 to 270 ° C. for 1 hour or more and then heating to 400 to 560 ° C. A method for producing an aluminum alloy plate for a secondary battery case. 2. The aluminum alloy further contains Zr in an amount of 0.
The method for producing an aluminum alloy plate for a secondary battery case according to claim 1, wherein the aluminum alloy plate is contained in an amount of 0.5 to 0.2% by weight.