JP2012197489A - High strength aluminum alloy sheet for secondary battery large-scaled rectangular can excellent in laser weldability and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high strength aluminum alloy sheet for a secondary battery large-scaled rectangular can excellent in laser weldability, which has high tensile strength, is excellent in press formability and laser weldability, and can be easily formed into a relatively large-scaled rectangular can for a battery by using a multistage drawing-ironing process, and a method for producing the same.SOLUTION: The high strength aluminum alloy sheet for a secondary battery large-scaled rectangular can excellent in laser weldability is welded with a member to be joined by a laser welding method; contains 0.01-0.20 mass% of Si, 0.05-0.50 mass% of Fe, 0.30-0.80 mass% of Cu, 0.90-1.30 mass% of Mn, and 0.20-0.80 mass% of Mg and comprises the remainder Al and inevitable impurities; and has tensile strength and elongation specified within a predetermined range. The aluminum alloy sheet is formed into, for example, a rectangular can 2 for a battery, and a battery can 1 is constructed by welding a lid member 3 to the open part of the rectangular can 2 by the laser welding method.

Description

  The present invention relates to a high-strength aluminum alloy plate for a secondary battery large-sized square can excellent in laser weldability used as a material for an outer can for a secondary battery such as a lithium ion secondary battery, and a method for producing the same.

Lithium ion secondary batteries are widely used as power sources for mobile products such as mobile phones and PCs (personal computers).
In lithium ion secondary batteries used in these mobile products, for example, a rectangular battery can in which an open part of a rectangular metal tube whose one side is open is closed with a lid member is used (see, for example, Patent Document 1). .) Even in a relatively large can, the dimensions of the cross section are about a short width W ≦ 10 mm, a long width L ≦ 50 mm, and a height H ≦ 60 mm. The battery can of such a mobile lithium ion secondary battery needs to have high strength in order to protect the internal electrode material from swelling and external impact due to heat generation during the charge / discharge cycle. An aluminum alloy plate having a thickness of about 0.40 to 0.60 mm is used as a tempered material of H16.

  On the other hand, in recent years, lithium ion secondary batteries are increasingly used in places that require a large capacity, such as large transport equipment and electric vehicles. In this case, the lithium ion secondary battery is used in units of a plurality of cells arranged in parallel, and the battery capacity per cell (output density: W / kg, energy density: Wh / kg) in order to minimize the loading load. ) Has been devised to increase as much as possible.

In particular, a hybrid vehicle (HV) or a plug-in hybrid vehicle (PHV) that uses an internal combustion engine as a main power and uses a secondary battery as auxiliary power, or an electric vehicle (EV) that obtains power by rotating a motor only with a secondary battery. ), The load capacity of the secondary battery is preferably small, and the battery capacity per cell is extremely important.
For this reason, the lithium ion secondary battery for in-vehicle use is a large square battery can larger than that used in mobile devices, that is, the cross-sectional dimensions are short width W ≧ 10 mm, long width L ≧ 70 mm or more. The battery capacity per cell is increased by using square battery cans of H ≧ 60 mm, and a plurality of them are mounted per unit.

JP 2000-11964 A

  By the way, a rectangular metal can used in a lithium ion secondary battery is generally manufactured using a multistage drawing-ironing process. Here, when manufacturing a large metal can having a height H of 60 mm or more, it is necessary to use a large transfer press in which the stroke of the press machine is more than three times the height of the metal can. Extremely severe deep drawing is performed as compared to manufacturing cans.

  In addition, in the case of a rectangular metal can for in-vehicle use, not only is it required to have sufficient swell resistance to charge / discharge cycles, but it can also protect the electrode material from external impacts assuming an automobile collision. Is also required. For this reason, as a raw material of a metal can, it is required to have higher strength, and an aluminum alloy material plate having a plate thickness t of 0.6 to 1.6 mm is used. However, such a thick plate-like aluminum alloy material plate is very susceptible to cracking and accompanying breakage during deep drawing, which increases the defective rate of battery cans.

  In such a battery can, for example, a lid member made of an aluminum alloy such as JIS1050 or 3003 and the battery can are joined by a laser welding method. Here, in particular, in-vehicle battery cans are required to protect the electrode material from the strong external impact as described above. Therefore, the bonding strength between the metal can and the lid member is high, that is, deep in laser welding. It is necessary that melting has occurred, and it is preferable that welding defects such as blow holes and melt sputtering are small. In particular, when a part of the melt spatter jumps around and a metal piece is mixed inside the battery can, the positive electrode and the negative electrode are short-circuited, and the internal pressure of the lithium ion secondary battery is also expected to increase abnormally. It is extremely important to suppress this.

  The present invention has been made to solve these problems, has high tensile strength, is excellent in press formability and laser weldability, and uses a multistage drawing-ironing process to form a relatively large corner for a battery. It is an object of the present invention to provide a high-strength aluminum alloy sheet for a secondary battery large-sized square can that can be easily formed into a mold can and excellent in laser weldability, and a method for producing the same.

  As a result of repeated investigations by the present inventors to obtain an aluminum alloy plate having high tensile strength and excellent press formability and laser weldability, the composition and mechanical properties of the aluminum alloy plate (tensile strength, elongation) ) Has led to the knowledge that an aluminum alloy sheet satisfying these requirements can be obtained. The present invention has been made based on such findings and has the following configuration.

A high-strength aluminum alloy plate for a secondary battery large square can excellent in laser weldability of the present invention is a high-strength aluminum alloy plate for laser welding welded to a member to be joined by a laser welding method, and includes Mn, Cu, Mg, Si, Fe is contained in the following content, the balance consists of Al and inevitable impurities,
Mn: 0.90 to 1.30% by mass, Cu: 0.30 to 0.80% by mass, Mg: 0.20 to 0.80% by mass, Si: 0.01 to 0.20% by mass, Fe: 0.05 to 0.50 mass%, tensile strength is 150 to 230 MPa, and elongation is 20% or more.

Further, in the present invention, the battery can be formed into a square can for a battery having a short width W of 10 mm or more, a long width L of 70 mm or more, and a height H of 60 mm or more by multistage drawing-ironing. To do.
Further, the present invention is characterized in that excellent laser weldability can be obtained by laser welding with a member to be joined.

  The method for producing a high-strength aluminum alloy plate for a secondary battery large square can excellent in laser weldability of the present invention is a method for producing a high-strength aluminum alloy plate for laser welding that is welded to a member to be joined by a laser welding method. In the aluminum alloy ingot containing Mn, Cu, Mg, Si, Fe in the following content, the balance being Al and inevitable impurities, homogenization treatment, hot rolling, cold rolling, final When manufacturing a high-strength aluminum alloy sheet for a secondary battery large square can excellent in laser weldability by performing annealing sequentially, Mn: 0.90 to 1.30% by mass, Cu: 0.30 to 0.80 % By mass, Mg: 0.20 to 0.80% by mass, Si: 0.01 to 0.20% by mass, Fe: 0.05 to 0.50% by mass, winding temperature of rolled sheet in hot rolling At 360 ° C or lower, and the final annealing is performed under cold pressure. After the temperature of the rolled sheet obtained in step 1 is increased to 400 to 550 ° C. at a temperature increase rate of 10 to 250 ° C./second, the temperature is maintained at this temperature for 5 to 60 seconds, and then cooled at a cooling rate of 20 to 200 ° C./second. It is characterized by that.

According to the present invention, a high-strength aluminum alloy plate for a secondary battery large-sized square can excellent in laser weldability contains Mn, Cu, Mg, Si, Fe at a predetermined content, and has a tensile strength and elongation. By being defined within the predetermined range, the tensile strength is high, and good press formability and laser weldability can be obtained.
For this reason, the high-strength aluminum alloy plate for a secondary battery large square can excellent in laser weldability can be easily formed into a relatively large battery square can by using multistage drawing and ironing. . The molded rectangular can is excellent in mechanical strength and can be welded to the battery lid member with a high welding strength by a laser welding method. For this reason, it can use suitably as a square can of the large sized lithium ion secondary battery for vehicle mounting.

  In addition, according to the present invention, the aluminum alloy ingot containing Mn, Cu, Mg, Si, and Fe in a predetermined amount is sequentially subjected to homogenization treatment, hot rolling, cold rolling, and final annealing. When manufacturing a high-strength aluminum alloy sheet for laser welding, in order to set the coiling temperature of the rolled sheet in hot rolling and the conditions for final annealing within a predetermined range, the tensile strength as described above is high, Moreover, the high intensity | strength aluminum alloy plate for secondary battery large square cans which is excellent in laser weldability excellent in press moldability and laser weldability can be obtained easily.

It is a schematic exploded perspective view which shows an example of the battery can shape | molded from the high intensity | strength aluminum alloy plate which concerns on this invention. It is a cross-sectional view of the rectangular can for batteries shown in FIG. In evaluation of the laser weldability of an Example, it is a schematic perspective view which shows the cutting state of a battery can.

Next, specific embodiments of the present invention will be described with reference to the drawings.
<High-strength aluminum alloy plate for laser welding>
First, an embodiment of the high-strength aluminum alloy plate for laser welding of the present invention will be described.
FIG. 1 is a schematic exploded perspective view showing an example of a battery can to which a battery square can formed from a high-strength aluminum alloy plate for laser welding according to the present invention is applied. FIG. 2 is a battery square shown in FIG. It is a cross-sectional view of a can.
In the following description, in the battery square can 2, a cross section along a plane orthogonal to the height direction is referred to as a “cross section”, the short width of the outer shape in this cross section is “W”, and the long width is The length in the direction orthogonal to the cross section is “height H”.

The high-strength aluminum alloy plate (hereinafter simply referred to as “aluminum alloy plate”) for a secondary battery large square can excellent in laser weldability of the present invention is welded to a member to be joined by a laser welding method. , Mn, Cu, Mg, Si, and Fe are contained in the following contents, and the balance is made of Al and inevitable impurities.
Mn: 0.90 to 1.30% by mass, Cu: 0.30 to 0.80% by mass, Mg: 0.20 to 0.80% by mass, Si: 0.01 to 0.20% by mass, Fe: 0.05-0.50 mass%. Moreover, the aluminum alloy plate of this embodiment has a tensile strength of 150 to 230 MPa and an elongation of 20% or more.
Thereby, the aluminum alloy plate of this embodiment can obtain high tensile strength, and can obtain excellent press formability and laser weldability.

The aluminum alloy plate of this embodiment is formed into a desired shape as necessary, and is welded to the member to be joined by a laser welding method.
When the aluminum alloy plate is formed, the shape is not particularly limited, but it is preferable to form the aluminum alloy plate into a battery square can 2 such as a lithium ion secondary battery having the structure shown in FIG.
1 and 2 is formed into a bottomed cylindrical shape having a rectangular cross section, and the battery can 1 is constituted by a lid member 3 that closes one end that is opened. The square can 2 of this embodiment is formed by multistage drawing-ironing, and has a large size with a short width W of 10 mm or more, a long width L of 70 mm or more, and a height H of 60 mm or more in the cross section. Has been. The lid member 3 is welded to the square can 2 by a laser welding method.

  Here, since the aluminum alloy plate of the present invention has good press formability, it can be easily formed into a large square can 2 as in the present embodiment using multistage drawing-ironing. Further, the molded square can 2 has high mechanical strength due to the excellent tensile strength and laser weldability of the aluminum alloy plate as the material, and the lid member 3 is made high by the laser welding method. It can be welded with welding strength. For this reason, it can use suitably as a square can of the large sized lithium ion secondary battery for vehicle mounting.

The above effects can be obtained when the content of each component contained in the aluminum alloy plate and its mechanical properties (tensile strength, elongation) are defined within a predetermined range.
Hereinafter, each component of the aluminum alloy plate, its content, and mechanical properties will be described.
“Mn: 0.90 to 1.30% by mass”
The addition of Mn has the effect of increasing the tensile strength of the aluminum alloy plate, miniaturizing the crystal grains, and improving the press formability of the aluminum alloy plate.
When the Mn content is less than 0.90% by mass, these effects are insufficient. On the other hand, if the Mn content exceeds 1.40% by mass, a coarse Al-Fe-Mn-based crystallized product is easily generated during casting of a slab for rolling, and these are mixed, thereby press forming an aluminum alloy plate. Remarkably deteriorates. For this reason, in this invention, Mn content is prescribed | regulated to 0.90-1.40 mass%. In addition, from the point which improves tensile strength and press moldability more, the range of 0.95-1.30 mass% is preferable for Mn content.

“Cu: 0.30 to 0.80 mass%”
The addition of Cu has the effect of increasing the tensile strength of the aluminum alloy plate and deepening the penetration of the molten metal during laser welding. Thereby, for example, when a battery square can is constituted by the aluminum alloy plate, the mechanical strength of the square can and the welding strength between the square can and the lid member are improved, and a battery can excellent in pressure strength is obtained. be able to.
When the Cu content is less than 0.30% by mass, these effects are insufficient. On the other hand, if the Cu content exceeds 0.80% by mass, the press formability and laser weldability of the aluminum alloy plate are significantly reduced. For this reason, in this invention, Cu content is prescribed | regulated to 0.30-0.80 mass%. In addition, it is preferable that Cu content is 0.35-0.70 mass% from the point which improves tensile strength, laser weldability, and press moldability more.

“Mg: 0.20 to 0.80 mass%”
The addition of Mg has the effect of increasing the pressure resistance of the aluminum alloy plate and deepening the penetration of the molten metal during laser welding. Thereby, for example, when a square can of a battery is constituted by the aluminum alloy plate, the mechanical strength of the square can and the welding strength between the square can and the lid member are improved, and a battery having excellent pressure strength is obtained. Can do.
When the Mg content is less than 0.20% by mass, these effects are insufficient. On the other hand, if the Mg content exceeds 0.80% by mass, the tensile strength of the aluminum alloy plate and the pressure resistance of the battery are improved, but the press formability of the aluminum alloy plate is lowered. Furthermore, when laser welding the aluminum alloy plate and the member to be joined, both blow holes and melt spatter are generated. For this reason, in this invention, Mg content is prescribed | regulated to 0.20-0.80 mass%. In addition, it is preferable that Mg content is 0.25-0.65 mass% from the point which improves tensile strength, laser weldability, and press moldability more.

“Si: 0.01 to 0.20 mass%”
Si exists as an unavoidable impurity and has the effect of slightly increasing the strength of the aluminum alloy plate, but adversely affects welding stability, such as the penetration depth becoming non-uniform in laser welding. For this reason, Si content needs to be 0.20 mass% or less, it is preferable that it is 0.15 mass% or less, and it is more preferable that it is less than 0.10 mass%. However, in order to make the Si content less than 0.01% by mass, it is necessary to use a high-purity metal that is difficult to obtain, and the aluminum alloy plate becomes expensive. For this reason, the minimum of Si content is prescribed | regulated to 0.01 mass%.

“Fe: 0.05 to 0.50 mass%”
Fe is present as an inevitable impurity like Si, and has the effect of slightly increasing the strength of the aluminum alloy plate. However, when the Fe content increases, Al—Fe—Mn-based crystallized particles are coarse on the aluminum alloy plate. To become distributed. When the Al—Fe—Mn crystallized particles are particularly coarse particles, they do not directly cause breakage during press forming of an aluminum alloy plate, but they tend to be a crack propagation path. For this reason, in order to obtain good press formability, it is necessary to appropriately manage the size and distribution state of Al—Fe—Mn crystallized particles distributed on the aluminum alloy plate.

  For this reason, in this invention, Fe content is controlled to less than 0.50 mass%. Thereby, crystallization of the Al—Fe—Mn coarse particles can be suppressed, and good press formability can be obtained. Note that. A more preferable range of the Fe content is 0.30% by mass or less. However, in order to make the Fe content less than 0.05% by mass, it is necessary to use a highly pure metal that is difficult to obtain, and the aluminum alloy plate becomes expensive. Furthermore, if the Fe content is extremely low, the castability of the aluminum alloy deteriorates, and problems such as cracking of the ingot occur. For this reason, the minimum of Fe content is prescribed | regulated to 0.05 mass%.

Next, the tensile strength and elongation of the aluminum alloy plate will be described.
Here, in this specification, “tensile strength” and “elongation” are “tensile strength” and “elongation” measured according to the tensile test method defined in JIS Z2201, respectively.
“Tensile strength: 150 to 230 MPa”
The tensile strength of the aluminum alloy plate affects the press formability of the aluminum alloy plate and the mechanical strength of the resulting molded body (such as a square can). In this embodiment, the tensile strength of the aluminum alloy plate is preferably 150 MPa or more and 230 MPa or less.
When the tensile strength of the aluminum alloy plate is less than 150 MPa, for example, when a square can of the battery is constituted by the aluminum alloy plate, the function of protecting the electrode material inside the battery from external impact cannot be obtained sufficiently. On the other hand, when the tensile strength exceeds 230 MPa, for example, when a rectangular can is formed by multi-stage drawing using a transfer press, cracks are likely to occur during the forming process, and the defect rate is significantly increased. When the tensile strength of the aluminum alloy plate is within the above range, sufficient swelling resistance to the charge / discharge cycle of the battery can be obtained, and a rectangular can for the battery that can sufficiently withstand external impact is produced with high productivity. Obtainable.

“Elongation: 20% or more”
The elongation of the aluminum alloy plate of the present embodiment affects the press formability when the aluminum alloy plate is formed by multistage drawing-ironing or the like.
Since the aluminum alloy sheet has an elongation of 20% or more, even when the wall thickness t is relatively thick, 0.6 to 1.6 mm, good formability can be obtained by multistage drawing-ironing, and the height H It can be reliably formed into a large square can of ≧ 60 mm or more.
Here, even a general-purpose aluminum alloy plate such as JIS3003 alloy can be sufficiently formed into a square can having a height H ≧ 60 mm. However, in the case of a high-strength aluminum alloy plate having a tensile strength of 150 to 230 MPa, the multistage drawing-ironing process is very difficult, and the elongation needs to be 20% or more to enable this process. That is, since the aluminum alloy plate has an elongation of 20% or more, it can be formed into a large square can 2 by multistage drawing-ironing processing while having high strength.

<Manufacturing Method of High Strength Aluminum Alloy Plate for Secondary Battery Large Square Can with Excellent Laser Weldability>
Next, the manufacturing method of this aluminum alloy plate (the manufacturing method of the aluminum alloy plate of this invention) is demonstrated.
This method for producing an aluminum alloy sheet includes an aluminum alloy ingot homogenization treatment step [1], a hot rolling step [2], a cold rolling step [3], and a final annealing step [4]. is doing. Hereinafter, each process will be described sequentially.

[1] Homogenization treatment step First, the aluminum alloy ingot corresponding to the composition of the target aluminum alloy plate is heated to the treatment temperature and held at this temperature for a certain period of time. Thereby, non-uniform structures such as segregation of the aluminum alloy ingot are removed, and the characteristics and quality of the obtained aluminum alloy plate are stabilized.
The treatment time and treatment temperature are not particularly limited, but are usually 480 ° C to 590 ° C and 60 minutes to 12 hours.

[2] Hot rolling step Next, the aluminum alloy ingot subjected to the homogenization treatment is rolled by passing between a pair of rolling rolls while being heated to a recrystallization temperature or higher, and the obtained rolled plate Is wound on a winding coil.
Moreover, in this invention, the temperature of the rolled sheet at the time of winding up a rolled sheet is prescribed | regulated to 360 degrees C or less. Thereby, the fibrous structure is strongly developed on the rolled sheet, and a uniform and fine crystal grain structure can be easily obtained by the final annealing performed in the post-process [4].
In addition, when performing this rolling process repeatedly, it is preferable to wind up a rolled sheet at the temperature of 360 degrees C or less in all times. Thereby, the fibrous structure of a rolled sheet can be developed more strongly.

[3] Cold rolling step Next, the rolled plate obtained in the hot rolling step is cold-rolled, and the obtained rolled plate is wound on a winding coil. Thereby, the flatness and hardness of the rolled sheet are adjusted to desired values.
Here, the degree of processing in this cold rolling step is preferably 20 to 85%. When the degree of work in the cold rolling process is less than 20%, the tensile strength of the obtained aluminum alloy plate is insufficient, and when the rectangular can of the battery is constituted by the aluminum alloy plate, sufficient pressure strength is obtained. There is no possibility. On the other hand, when the workability exceeds 90%, the tensile strength of the aluminum alloy plate becomes too high, and the press formability is lowered. Thereby, when this aluminum alloy plate is formed into a square can by multistage drawing and ironing, the obtained square can may be easily broken.

[4] Final annealing step Next, the rolled sheet obtained by the cold rolling step is heated to a temperature higher than the recrystallization temperature (annealing temperature), held at this temperature for a certain period of time, and then cooled, thereby cooling the aluminum alloy plate. Get.
This final annealing is a process in which the aluminum alloy sheet is heated to a temperature higher than the recrystallization temperature and then cooled to recrystallize, whereby the processing strain of the rolled sheet is alleviated, and the tensile strength and press formability are compatible.

Here, in order to obtain an aluminum alloy sheet excellent in tensile strength and press formability, it is preferable that the recrystallized crystal grains are fine and uniform. The process conditions are defined as follows.
Temperature rising rate: 10 to 250 ° C./second, heating temperature: 400 to 550 ° C., holding time: 5 to 60 seconds, cooling rate: 20 to 200 ° C./second.

  When the rate of temperature increase is slower than 10 ° C./second, accumulated energy introduced during cold rolling is released during this temperature increase process, so the recrystallization nucleation rate decreases and the crystal grain size after annealing increases. . As a result, the tensile strength and press formability of the resulting aluminum alloy plate are reduced. On the other hand, even if the rate of temperature rise is higher than 250 ° C./second, no further effect is obtained, and expensive heating equipment is required instead, and the production cost of the aluminum alloy plate increases.

  When the heating temperature at the time of annealing is lower than 400 ° C., the time until the recrystallization is completed becomes long, so that the production efficiency of the aluminum alloy plate is lowered. In addition, elongated and coarse crystal grains are generated in the obtained aluminum alloy plate. On the other hand, when the annealing temperature is higher than 550 ° C., local melting occurs and elongation becomes low, and the press formability of the obtained aluminum alloy plate is lowered.

When the holding time is shorter than 5 seconds, recrystallization is not completely completed, and fine crystal grains cannot be obtained. On the contrary, if the holding time is longer than 60 seconds, crystal grains grow. Thereby, in any case, the tensile strength of the obtained aluminum alloy sheet becomes low.
On the other hand, when the cooling rate is lower than 20 ° C./second, Cu and Mg form an intermetallic compound with Al during cooling, resulting in a decrease in strength of the resulting aluminum alloy plate. Further, even if the cooling rate is faster than 200 ° C./second, no further effect can be obtained. On the contrary, expensive cooling equipment is required, and the production cost increases.
Thus, the aluminum alloy plate which is high in strength and excellent in press formability can be manufactured by setting the temperature rising rate, annealing temperature, holding time and cooling rate in the final annealing step after cold rolling within the above ranges.

The high-strength aluminum alloy plate for secondary battery large square cans manufactured as described above and having excellent laser weldability has high tensile strength and is excellent in press formability and laser weldability.
For this reason, it can be easily formed into a large battery square can using, for example, multistage drawing-ironing. In addition, the square can formed from the above-described aluminum alloy plate has high mechanical strength due to the excellent tensile strength and laser weldability of the aluminum alloy plate, and the lid member can be formed by laser welding. Can be welded with high welding strength. For this reason, it can use suitably as a square can of the large sized lithium ion secondary battery for vehicle mounting.

  As mentioned above, although each embodiment of the aluminum alloy plate and its manufacturing method of this invention was described, this invention is not limited to these, In the range which does not deviate from the scope of the present invention, it can change suitably.

Specific examples of the present invention will be described below, but the present invention is not limited to these examples.
"Example 1 to Example 5"
An aluminum alloy ingot containing Mn, Cu, Mg, Si, and Fe as shown in Table 1 was prepared. And this aluminum alloy ingot was homogenized by holding at 580 ° C. for 6 hours, and then subjected to hot rolling. Table 1 shows the measurement temperature of the winding coil in this hot rolling process.
Subsequently, the rolled plate obtained in the hot rolling step was cold-rolled to obtain a rolled plate having a thickness of 1.6 mm.
Next, final rolling was performed on the rolled plate. The conditions for final annealing are as follows.
Temperature rising rate: 120 ° C./second, annealing temperature: 450 ° C., holding time at annealing temperature: 30 seconds, cooling rate: 150 ° C./second. The aluminum alloy plate was obtained by the above process.

“Example 6 and Example 7”
An aluminum alloy plate was obtained in the same manner as in Example 1 except that the final annealing conditions were changed as shown in Table 2.

“Comparative Examples 1 to 6”
As shown in Table 1, an aluminum alloy plate was obtained in the same manner as in Example 1 except that the content of at least one of the components contained in the aluminum alloy was outside the predetermined range.
“Comparative Example 7”
As shown in Table 1, during hot rolling, an aluminum alloy plate was obtained in the same manner as in Example 1 except that the rolling temperature of the rolled plate was outside the predetermined range.
“Comparative Example 8 to Comparative Example 11”
As shown in Table 2, an aluminum alloy plate was obtained in the same manner as in Example 1 except that the final annealing condition was outside the predetermined range.

<Evaluation>
About the aluminum alloy plate produced by each Example and each comparative example, press-formability and laser weldability were evaluated. The evaluation conditions are as shown below.
(1) Press formability Each aluminum alloy plate having a plate thickness of 1.6 mm is subjected to multi-stage drawing-ironing processing to can thickness t: 1.3 mm, short width W in cross section: 37.5 mm, long width L: It was molded into a rectangular can of 150 mm and height H: 120 mm. And the press formability in the case of the shaping | molding was evaluated according to the following references | standards. The press used for processing is a transfer press having a 10-stage mold.
○: When the multistage drawing-ironing process can be formed without any problem. △: The square can was formed, but rough skin and microcracks are generated. X1 to x10: Cracks are generated during the multistage drawing process. This is a case where molding was not possible, and the number on the right indicates the number of stages of the transfer press when cracking occurred.
Moreover, the aluminum alloy plate produced in Example 1 was formed into a square can with the dimensions shown in Table 3 by multistage drawing-ironing, and the press formability during the forming was similarly evaluated.
In addition, although it is evaluation of the volume V and L / W ratio which are shown in Table 3, it would like to produce as large a battery can as the volume V as a battery can, but when L / W ratio becomes large, it will become a tendency for shaping | molding to become difficult.

(2) Laser weldability Laser weldability was evaluated using each square can formed from an aluminum alloy sheet in the above-described evaluation of press formability.
An aluminum lid member (plate thickness: 1.0 mm) made of JIS standard A3003-O material is welded to the open side of each square can using a Yb-fiber laser welding machine with a maximum output of 2 kw to obtain a battery can. It was. The welding conditions are as follows.
Oscillation method: CW oscillation, fiber diameter: φ0.1, Ar gas flow rate: 20 (l / min), output: 850 W, welding speed: 166 (mm / sec).
About the weld part of the obtained battery can, the fusion | melting sputter | spatter, the penetration depth, and the number of blow holes were investigated as follows.

a. Melt Sputter On the outer peripheral surface of each battery can, the range of ± 1.0 mm from the weld bead was observed with a CCD camera, and all the occurrences of melt sputter of 50 μm or more were measured. On the basis of a unit length of 100 mm, the case where the number of sputters generated was 0-10, the case where it was 10-50, was evaluated as Δ, and the case where it was 50 or more was evaluated as x.
b. 3. Evaluation of penetration depth As shown in FIG. 3, each battery can 1 was cut vertically along the cutting line b (divided into four equal parts), and the maximum penetration depth of the weld 4 observed in the cross section was measured. . Here, the battery cans 1 were observed at six cross-sectional positions (three on one side edge of the lid member in the width direction, a total of six positions), and the maximum penetration depth was evaluated by the average value of the six observation positions. did.
The penetration depth becomes an index of the joint strength of the welded portion 4, and the larger the value, the higher the joint strength of the welded portion 4 and the better the pressure resistance performance.
On the other hand, when the penetration depth is shallow with respect to the wall thickness, the required compressive strength cannot be obtained. However, if the penetration depth becomes larger than necessary, the molten metal may penetrate the thickness of the square can 2 and damage the internal electrode member. Further, in order to obtain deep penetration, a high output and a large amount of heat input are required.
Specifically, a penetration depth of about 40 to 80% is preferable with respect to the thickness t of the can. Therefore, it is desirable to control the battery can with a thickness of 1.3 mm to 520 μm (40%) to 1040 μm (80%). In addition, the welding machine nozzle front-end | tip position is shown by the code | symbol S in FIG.

c. The number of blowholes with a width of 100 μm or more The lid member and the battery can were bent on the opposite side to the weld bead, and the entire welded portion was observed using a CCD camera. Then, the number of blowholes having a width of 100 μm or more existing in the welded portion was measured.
A blowhole is a kind of welding defect, and the lid hole and the battery can are not joined at the place where the blowhole is generated. In particular, large blow holes with a width of 100 μm or more reduce the bonding strength, and the number of occurrences is an indicator of the bonding strength of the weld. That is, the smaller the number of blow holes with a width of 100 μm or more, the higher the joint strength of the welded portion. On the basis of a unit length of 100 mm, 0 to 10 blowholes having a width of 100 mm or more were evaluated as ◯, and 10 or more blowholes were evaluated as ×.
The above evaluation results are shown in Tables 1 to 3.

As shown in Tables 1 to 3, the content of each element is within a predetermined range (Si: 0.01 to 0.20 mass%, Fe: 0.05 to 0.50 mass%, Cu: 0.30 0.80 mass%, Mn: 0.90 to 1.30 mass%, Mg: 0.20 to 0.80 mass%) has a high tensile strength of 150 to 230 MPa and an elongation of 20% or more. It was found to be an excellent high-strength aluminum alloy plate for laser welding. Moreover, as conditions for producing a high-strength aluminum alloy plate for laser welding having such characteristics, a hot rolling coiling temperature of 360 ° C. or lower, a temperature increase rate in final annealing of 10 to 250 ° C./second, 400 to 500 The aluminum alloy plates (Examples 1 to 7) produced with heating at 0 ° C., holding time of 5 to 60 seconds, and cooling rate of 20 to 200 ° C. have appropriate tensile strength and sufficient elongation.
For this reason, good press formability could be obtained regardless of the dimensions of the square can to be molded (see Table 3). Specifically, in a size with a thickness of 1.3 mm, a long width of 150 mm, and a width of 180 mm, a rectangular can having a height in the range of 60 to 160 mm and a short width of 26.5 to 50 mm can be formed without any problem by press molding and ironing. I was able to manufacture it.

In addition, the number of melt spatters was reduced in laser welding with the lid member, the occurrence of blow holes could be suppressed, and a sufficient penetration depth could be obtained.
In the obtained results, the penetration depth is preferably about 40 to 80% of the wall thickness of the can. It can be said that the greater the penetration depth, the higher the joint strength and the better. However, if the penetration depth is more than necessary, there is a risk that the welding speed must be reduced or the plate may be penetrated.
The number of fusion sputters is preferably 50 or less, and the possibility of internal mixing of metal powder by sputtering is reduced.
The number of blowholes generated is preferably 10 or less, and a high joint strength can be obtained because there are few unwelded portions.

On the other hand, the samples of Comparative Examples 1 to 6 which are aluminum alloy plate samples whose content of each element is out of the predetermined range described above, and the samples of Comparative Examples 7 to 10 whose manufacturing conditions are out of the predetermined range are as follows: The tensile strength and elongation were not within the predetermined range, or the laser weldability was poor. And among these, the samples of Comparative Examples 2, 6, 9, and 10 where the tensile strength is too high, the samples of Comparative Examples 7 and 10 where the elongation is insufficient, and the sample of Comparative Example 4 that has too much Mn content are Cracks occurred during press molding and could not be molded into a square can.
In addition, the sample of Comparative Example 8 in which the holding time at the annealing temperature was lengthened in the annealing process and the cooling rate was slowed, and the sample of Comparative Example 11 in which the heating rate was slowed were difficult to control temperature and lacked practicality. there were.

"Examples 8-12, Comparative Examples 12-18"
Tests similar to the tests performed in Examples 1 to 5 above (measurement of tensile strength, measurement of elongation, laser weldability test, press formability test) were also performed on a rolled plate having a thickness of 0.8 mm. The results are shown in Table 4. A sample having a plate thickness of 0.8 mm was formed into a square can having a thickness t of 0.6 mm, a short width W of 14 mm, a long width L of 90 mm, and a height H of 70 mm. The output of the laser welder was set to 550W.
The samples of Examples 8 to 12 shown in Table 4 are samples having the same composition ratio as that of the samples of Examples 1 to 5 shown in Table 1 in the order of the table, but only the plate thickness is different, and Comparative Examples 12 to The sample shown in FIG. 18 is a sample having the same composition ratio as that of the samples of Comparative Examples 1 to 7 shown in Table 1 but only the plate thickness. These samples were processed at the hot rolling coiling temperature shown in Table 4, and then subjected to a test equivalent to the sample shown in Table 1.
Furthermore, the aluminum alloy plate having a thickness of 0.8 mm produced in Example 8 was formed into a square can with the dimensions shown in Table 5 by multi-stage drawing and ironing, and the press formability during the forming was similarly set. And evaluated. Except for the number of mold stages being 8, the calculation method for the number of spatters and the number of blow holes is the same as that for the 1.6 mm thick sample described above.

  As in the results shown in Table 4 and Table 5, even in the test using a rolled plate having a thickness of 0.8 mm, the test results shown in Table 1 showing the test results using the rolled plate having a thickness of 1.6 mm are obtained. As a result, it was found that the same results were obtained when used as a secondary battery large square can on a rolled plate having a thickness of 0.8 mm to 1.6 mm.

  DESCRIPTION OF SYMBOLS 1 ... Battery can, 2 ... Square can for batteries, 3 ... Lid member, 4 ... Welded part, W ... Short width, L ... Long width, H ... Height, a ... Bead width, b ... Cutting position, t ... The thickness of the can.

Claims (4)

A high-strength aluminum alloy plate for laser welding that is welded to the member to be joined by the laser welding method, containing Mn, Cu, Mg, Si, Fe in the following contents, and the balance consisting of Al and inevitable impurities ,
Mn: 0.90 to 1.30% by mass
Cu: 0.30 to 0.80 mass%
Mg: 0.20 to 0.80 mass%
Si: 0.01-0.20 mass%
Fe: 0.05 to 0.50 mass%
A high-strength aluminum alloy plate for a secondary battery large square can excellent in laser weldability, characterized by a tensile strength of 150 to 230 MPa and an elongation of 20% or more   2. The rectangular can for a battery having a short width W of 10 mm or more, a long width L of 70 mm or more, and a height H of 60 mm or more can be formed by multistage drawing-ironing. High-strength aluminum alloy plate for secondary battery large square cans with excellent laser weldability.   The high-strength aluminum alloy plate for a secondary battery large square can excellent in laser weldability according to claim 1 or 2, wherein excellent laser weldability is obtained by laser welding with a member to be joined. A method of manufacturing a high-strength aluminum alloy plate for laser welding that is welded to a member to be joined by a laser welding method, containing Mn, Cu, Mg, Si, Fe in the following contents, and the balance being inevitable with Al When manufacturing high-strength aluminum alloy plates for secondary battery large square cans with excellent laser weldability by sequentially performing homogenization, hot rolling, cold rolling, and final annealing on aluminum alloy ingots made of impurities. ,
Mn: 0.90 to 1.30% by mass
Cu: 0.30 to 0.80 mass%
Mg: 0.20 to 0.80 mass%
Si: 0.01-0.20 mass%
Fe: 0.05 to 0.50 mass%
The coiling temperature of the rolled plate in hot rolling is 360 ° C. or less,
The final annealing is performed by heating the rolled sheet obtained by cold rolling to 400 to 550 ° C. at a temperature rising rate of 10 to 250 ° C./second, and holding at this temperature for 5 to 60 seconds, and then a cooling rate of 20 to A method for producing a high-strength aluminum alloy plate for a secondary battery large-sized square can excellent in laser weldability, which is performed by cooling at 200 ° C./second.

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