JP2003007260A - Aluminum alloy plate for secondary battery case - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy plate for a secondary battery case that has high strength and is superior in press moldability and weldability. SOLUTION: The aluminum alloy plate for a secondary battery case contains Mn of 0.3 to 1.5 wt.% and Fe of more than 1.0 to 1.8 wt.%, with the rest unavoidable impurities and Al. The aluminum alloy plate for a secondary battery case may further include either or both of 0.1 to 0.8 wt.% of Cu and more than 0.10 to 1.0 wt.% of Mg, include either or both of Cr of 0.05 to 0.2 wt.% and Zr of 0.05 to 0.2 wt.% of Zr, or contains either or both of Cu of 0.1 to 0.8 wt.% and Mn of more than 0.10 to 1.0 wt.% and also either or both of Cr of 0.05 to 0.2 wt.% and Zr of 0.05 to 0.2 wt.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy plate suitable for use as a case of a secondary battery serving as a power source for notebook personal computers, mobile phones and the like, and more particularly to an aluminum alloy plate for a lithium ion secondary battery case. It is about.

[0002]

2. Description of the Related Art A secondary battery is required to be small and lightweight because it is used as a power source for portable devices such as notebook personal computers and mobile phones. As one of the requirements, the thinning of the secondary battery case is being studied.

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

[0004]

By the way, a secondary battery is manufactured by putting an electrode body in a case made of the above-mentioned material and then sealing it with a lid by welding or caulking. When the secondary battery manufactured in this manner is used in a mobile phone or the like, the temperature inside the case may rise and the pressure inside the case may increase during charging. In that case, there is a problem that a large swelling occurs in the case manufactured from the above-mentioned relatively soft case material.

The present invention has been accomplished in view of the above-mentioned problems, and an object thereof is to provide an aluminum alloy sheet having high strength and excellent overall characteristics such as press formability and weldability. .

[0006]

The aluminum alloy plate for a secondary battery case according to claim 1 has an Mn of 0.3-1.
It is characterized by containing 5% by weight of Fe and more than 1.0 to 1.8% by weight of Fe, and the balance consisting of unavoidable impurities and Al. Since this aluminum alloy plate contains Mn and Fe, it has high strength and excellent press formability. From this, the aluminum alloy plate of the present invention has high strength, so that it can suppress the swelling of the secondary battery case, and is also excellent in press formability and weldability,
It can be preferably used as an aluminum alloy plate for a secondary battery case.

The invention according to claim 2 is the aluminum alloy plate for a secondary battery case according to claim 1, further comprising 0.1 to 0.8% by weight of Cu and more than 0.10 to 1.
It is characterized by containing one or both of 0% by weight. In addition to the effect of the above-mentioned claim 1, this aluminum alloy plate is further enhanced in strength by containing Cu and Mg.

According to a third aspect of the present invention, in the aluminum alloy plate for a secondary battery case according to the first aspect, further 0.05 to 0.2% by weight of Cr and 0.05 to 0.
It is characterized by containing one or both of 2% by weight. In addition to the effect of the above-mentioned claim 1, this aluminum alloy plate further improves press formability and strength by containing Cr and Zr.

A fourth aspect of the present invention is the aluminum alloy plate for a secondary battery case according to the third aspect, further comprising 0.1 to 0.8% by weight of Cu and more than 0.10 to 1.
It is characterized by containing one or both of 0% by weight. In addition to the effect of the above-mentioned claim 3, this aluminum alloy plate is further enhanced in strength by containing Cu and Mg.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The aluminum alloy plate for a secondary battery case of the present invention contains Mn in an amount of 0.3 to 1.5% by weight and Fe in excess of 1.0 to 1.8% by weight, and the balance is It has a composition consisting of unavoidable impurities and Al.

In the aluminum alloy plate for a secondary battery case of the present invention, the aluminum alloy plate for a secondary battery case containing Mn and Fe is further added with (a) 0.1 to 0.8 weight% of Cu. %, Mg in one or both of more than 0.10 to 1.0% by weight, and (b) Cr in 0.1.
One or both of 0.05 to 0.2% by weight and Zr to 0.05 to 0.2% by weight, or (c) Cu of 0.1
.About.0.8 wt%, Mg in excess of 0.10 to 1.0 wt%, one or both of them, and Cr in 0.05
.About.0.2 wt%, and Zr may be included in one or both of 0.05 to 0.2 wt%.

First, constituent components of an aluminum alloy plate for a secondary battery case (hereinafter referred to as "aluminum alloy plate") will be described.

The aluminum alloy plate of the present invention contains Mn and Fe as essential components. Mn and Fe enhance the strength of the aluminum alloy plate and also refine the crystal grains to contribute to the improvement of press formability. The content of Mn and Fe capable of exerting these effects is M
n is 0.3 to 1.5% by weight, preferably 0.6 to 1.3
% By weight, and Fe is more than 1.0 to 1.8% by weight.
When the contents of Mn and Fe are out of the above ranges, the effect of increasing the strength of the aluminum alloy plate is insufficient, and the effect of refining the crystal grains is insufficient, which contributes to the improvement of press formability. There are things you can't do. Therefore, the aluminum alloy sheet of the present invention has high strength, excellent press formability and weldability, and is suitable for use in a secondary battery case.

The content of Mn and Fe is set in the above range so that the composition ratio of Al, Mn and Fe is near the ternary eutectic point in the ternary phase diagram of Al-Mn-Fe. In the manufacturing process of an aluminum alloy plate, when the composition ratio of Al, Mn and Fe is near the ternary eutectic point during casting, the α phase mainly composed of Al and Al, Mn and F
The intermetallic compound consisting of e forms a fine two-phase mixture called a eutectic. The intermetallic compound in the formed two-phase mixture is spheroidized by the homogenization treatment after casting and further divided by cold rolling to be very fine dispersed particles. Since the fine dispersed particles are distributed in the aluminum alloy plate at a high density, the fine dispersed particles serve as nuclei of recrystallized grains (work as nucleation sites) during annealing. Due to the action of the dispersed particles, the crystal grains of the aluminum alloy plate are refined and the press formability is improved. At the same time, this aluminum alloy plate has Mn and F
High strength is obtained by containing e. If the Mn content is less than 0.3% by weight or more than 1.5% by weight, the amount of the two-phase mixture produced during casting may decrease, and the above-mentioned effect may not be sufficiently obtained. Further, even when the Fe content is 1.0% by weight or less or exceeds 1.8% by weight, the amount of the two-phase mixture generated during casting is reduced, and the above-mentioned effects may not be sufficiently obtained.

The aluminum alloy plate of the present invention described above includes
Further, Cu, Mg, Cr, and Zr components can be added. Specifically, as described above, (a) Cu, M
An embodiment containing one or both of g and (b) Cr, Zr
There is a mode of containing one or both of (1) and a mode of containing (c) one or both of Cu and Mg and further containing one or both of Cr and Zr.

In the above embodiment (a) containing one or both of Cu and Mg, the strength of the aluminum alloy plate is increased by containing at least one of Cu and Mg.

Cu has the effect of increasing the strength of the aluminum alloy plate. If the Cu content is less than 0.1% by weight, the effect is insufficient, and if it exceeds 0.8% by weight, the press formability may deteriorate. In addition, the preferable range of Cu content is more than 0.30 to 0.7% by weight, and the strength can be further increased.

Mg also has the effect of increasing the strength of the aluminum alloy plate. If the Mg content is 0.10 wt% or less, the effect becomes insufficient, and if it exceeds 1.0 wt%, a secondary battery case lid is welded to the body of the secondary battery case after molding. In that case, the weldability may be impaired. In addition, the preferable range of the Mg content is 0.15 to 0.6% by weight, and the strength can be further increased.

In either case where only Cu or Mg is contained in the aluminum alloy plate, or when both Cu and Mg are contained in the aluminum alloy plate, the above-mentioned content is used to obtain aluminum. The strength of the alloy plate can be increased.

In the above embodiment (b) containing one or both of Cr and Zr, at least one of Cr and Zr is contained to make the crystal grains in the aluminum alloy plate finer and press-molded. The strength is also improved while improving the property.

[0021] Cr has the effect of refining the crystal grains in the aluminum alloy plate to improve the press formability and also the strength. If the Cr content is less than 0.05% by weight, the effect becomes insufficient, and if it exceeds 0.2% by weight, coarse crystallized substances are likely to be formed during casting, and thus press formability may be deteriorated. . In addition, the preferable range of Cr content is 0.08 to 0.15% by weight, and press formability can be further improved.

Zr also has the effect of refining the crystal grains in the aluminum alloy plate to improve the press formability and the strength. If the Zr content is less than 0.05% by weight, the effect becomes insufficient, and if it exceeds 0.2% by weight, coarse crystallized substances are likely to be formed during casting, and thus press formability may be deteriorated. . In addition, the preferable range of the Zr content is 0.08 to 0.15% by weight, and the press formability can be further improved.

In either case where only Cr or Zr is contained in the aluminum alloy plate, or when both Cr and Zr are contained in the aluminum alloy plate, the above content is used to obtain aluminum. The press formability of the alloy plate can be improved and the strength can be increased.

In the embodiment of (c) containing one or both of Cu and Mg, and further containing one or both of Cr and Zr, the strength of the aluminum alloy sheet is improved by containing at least one of Cu and Mg. Higher, and Cr and Z
By including at least one of r, the crystal grains in the aluminum alloy plate are refined to improve press formability and strength. Cu, Mg and Cr,
The Zr content and its effect are the same as above.

The content of Si present as an unavoidable impurity in the aluminum alloy plate is not particularly specified in the present invention, but Si may be contained up to 0.8% by weight. The aluminum alloy sheet of the present invention containing 0.8% by weight or less of Si does not deteriorate the above-mentioned properties of strength, press formability and weldability.

Here, the strength is evaluated by the tensile strength obtained by a tensile test. If the strength of the aluminum alloy plate becomes sufficiently high, the internal temperature of the secondary battery case rises when the secondary battery is charged. Based on the above, it is possible to suppress the swelling of the secondary battery case due to the increase of the internal pressure. Therefore, by using the aluminum alloy plate of the present invention as a secondary battery case, the problem of swelling of the conventional secondary battery case can be solved.

As the strength of the aluminum alloy plate having the composition of the present invention, the tensile strength is preferably 200 MPa or more, and more preferably 210 MPa or more. By setting the tensile strength within this range, it is possible to suppress swelling of the secondary battery case manufactured from the aluminum alloy plate of the present invention. The upper limit of the tensile strength is not particularly specified, but the value depends on the characteristics of the aluminum alloy plate and the manufacturing method. Therefore, here, the upper limit of the tensile strength is about 400 MPa, preferably 380, although it can be stably manufactured at low cost with the current aluminum plate manufacturing technology.
It is set to about MPa.

The aluminum alloy sheet of the present invention has improved press formability due to the refinement of crystal grains, and the size of the crystal grains was determined by the following method in the cross section in the rolling direction. The average crystal grain size is preferably 25 μm or less. A more preferable range is less than 20 μm. The average crystal grain size here is SEM (ScanningEl
Crystal orientation observation device (commonly called EBSP (Electron Back-Scatter) attached to an ectron Microscope, scanning electron microscope)
diffraction pattern, reflection electron Kikuchi ray diffraction pattern)), the grain boundaries of the rolling direction of the aluminum alloy sheet are observed, and the cross-sectional area of the crystal grains is measured by analysis software. If the average crystal grain size exceeds 25 μm, the press formability and weldability may deteriorate. Although the lower limit of the average crystal grain size is not specified, the lower limit of the average crystal grain size is determined by the current aluminum plate manufacturing technology because the minimum average crystal grain size is about 3 μm although it can be manufactured stably at low cost. The value is 3 μm.

The aluminum alloy plate of the present invention is manufactured by the following method.

The aluminum alloy having the composition of the present invention is melted, cast, homogenized, hot-rolled, cold-rolled,
A plate material is obtained through the steps of intermediate annealing and final cold rolling.

In this manufacturing process, the temperature rising rate in the intermediate annealing process is 10 to 250 ° C./sec, and the annealing temperature is 450 to.
580 ° C, holding time 5 to 60 seconds, cooling rate 20 to 2
It is preferable to manufacture it at 00 ° C./sec.

If the heating rate is slower than 10 ° C./sec, the average crystal grain size may not be 25 μm or less. This is because the accumulated energy introduced during cold rolling is released and the recrystallization nucleation rate decreases, and the average crystal grain size after annealing increases. If the rate of temperature increase exceeds 250 ° C./sec, expensive equipment needs to be charged, which increases the production cost. If the annealing temperature is lower than 450 ° C., it takes a long time to complete the recrystallization, which increases the production cost and may cause elongated and coarse crystal grains. If the annealing temperature is higher than 580 ° C., recrystallization ends in a short time and grain growth occurs, so that the crystal grains may become large. If the holding time is shorter than 5 seconds, recrystallization may not be completed completely and fine crystal grains may not be obtained. When 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 may not be obtained.

When the component composition contains Cu or Mg, the cooling rate is preferably higher than 20 ° C./sec. If the cooling rate is lower than that, Cu or Mg is generated during cooling.
May precipitate and the strength may decrease. If the cooling rate exceeds 200 ° C / sec, capital investment for cooling will increase,
Production cost increases.

As described above, the temperature rising 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 can be set to a predetermined size, for example, 25 μm or less, and an aluminum alloy plate excellent in press formability can be manufactured. .

Further, the rolling reduction during 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 the press formability deteriorates.

[0036]

EXAMPLES The present invention will be described below with reference to Examples and Comparative Examples.

(Examples) Table 1 shows the manufactured Examples 1 to 1.
11 is a component composition of the aluminum alloy plate of 11 of the present invention.

First, an ingot of an aluminum alloy compounded so that the manufactured aluminum alloy plate has the composition shown in Table 1 was melted and cast by semi-continuous casting, and the obtained cast product was chamfered. To remove the non-uniform surface layer. After that, homogenization treatment is carried out by holding at a temperature of 595 ° C. for 6 hours, cooled to 400 ° C., and rapidly hot rolled,
A plate material having a thickness of 7 mm was used. Then, cold rolling is performed to a thickness of 0.6 mm, and the temperature increase rate in the intermediate annealing step is set to 1
00 ° C / sec, annealing temperature 500 ° C, holding time 25 sec,
Intermediate annealing was performed at a cooling rate of 150 ° C / sec. Then, final cold rolling was performed to a thickness of 0.4 mm. The rolling reduction in the final cold rolling was 33%. Thus, the aluminum alloy plates of Examples 1 to 11 according to the present invention were manufactured.

(Comparative Example) The aluminum alloy sheets of Comparative Examples 1 to 6 were produced by the same method as that of the above example except that the produced aluminum alloy sheet had the composition shown in Table 1.

[0040]

[Table 1]

(Evaluation of Tensile Strength and Press Formability) A JIS Z 2201 No. 5 test piece was cut out from the obtained aluminum alloy plate, and a tensile test was carried out by the method defined in JIS Z 2241 to obtain the tensile strength. , Yield strength and elongation were examined.

The average crystal grain size is SEM (XL30Fe,
EBSP system (TSL) attached to PHILIPS
OIM2.8 analysis software (TSL) from the crystal orientation data measured at 0.2 μm point intervals.
Sought by. A crystal grain was one having 10 or more points in a region surrounded by grain boundaries with a misorientation of 15 ° or more.

Regarding 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
The deep drawing test was performed using the plank of No. 2 and evaluated by the limiting drawing ratio. ○ with a limit aperture ratio of 1.95 or more
Those less than 1.95 were marked with x.

Regarding the weldability, a YAG, pulse laser welder (KYL-500A / BSP, Kataoka Manufacturing Co., Ltd.) was used to weld the aluminum alloy sheet of the present invention by the butt method, and cracking, porosity, and poor penetration were observed. There were no welding defects such as ◯, and those with welding defects were x.

(Evaluation Results) Examples 1 to 11 and Comparative Example 1
Table 2 shows the evaluation results of tensile strength, yield strength, elongation, average crystal grain size, press formability, and weldability of ~ 6.

The aluminum alloy plates of Examples 1 to 11 were
Tensile strength is as high as 210 MPa or more, and average crystal grain size is 9
It was as small as less than μm. And, it showed good press formability and weldability. On the other hand, the aluminum alloy sheets of Comparative Examples 1 to 6 had a tensile strength lower than 200 MPa or poor press formability or weldability.

[0047]

[Table 2]

[0048]

As described above, according to the aluminum alloy sheet of the present invention, since it has a high strength, it is possible to suppress the swelling of the secondary battery case, and it is also excellent in press formability and weldability. It can be preferably used as an aluminum alloy plate for a secondary battery case, particularly for a lithium ion secondary battery case. Moreover, since the aluminum alloy plate of the present invention has excellent press formability and weldability, a secondary battery case can be manufactured at low cost.

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Claims (4)

[Claims] 1. A secondary battery containing 0.3 to 1.5% by weight of Mn and more than 1.0 to 1.8% by weight of Fe, and the balance being inevitable impurities and Al. Aluminum alloy plate for cases. 2. The aluminum alloy plate for a secondary battery case further comprises 0.1 to 0.8% by weight of Cu and 0.1% by weight of Mg.
The aluminum alloy plate for a secondary battery case according to claim 1, containing one or both of more than 0 and 1.0% by weight. 3. The aluminum alloy plate for a secondary battery case further contains Cr in an amount of 0.05 to 0.2% by weight and Zr of 0.
The aluminum alloy plate for a secondary battery case according to claim 1, which contains one or both of 05 to 0.2% by weight. 4. The aluminum alloy plate for a secondary battery case further contains 0.1 to 0.8% by weight of Cu and 0.1% of Mg.
The aluminum alloy plate for a secondary battery case according to claim 3, containing one or both of more than 0 and 1.0% by weight.