JP2007031825A - Aluminum alloy sheet for battery housing and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum alloy sheet for a battery housing, which can be shaped into a square housing without encountering housing break and worsened appearance by drawing and ironing in multiple stages, does not form cracks or pinholes after being sealed by common laser welding, has good creeping resistance, and not cause swelling during a charge/discharge cycle. <P>SOLUTION: The aluminum alloy sheet comprises 0.8 to 1.5% Mn, 0.2 to 0.8% Mg, above 0.7 to 1.2% Cu, the total amount of Mn, Mg, and Cu (Mn%+Mg%+Cu%) being 2.6% or less, and impurities being controlled so that Si is present in an amount of 0.20% or less, Fe is present in an amount of 0.4% or less, and Zn is present in an amount of 0.1% or less, with the balance comprising Al with inevitable impurities. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an aluminum alloy plate for a battery case, and more particularly to an aluminum alloy plate for a battery case such as a prismatic lithium ion battery used for a mobile phone or a notebook computer, and a method for manufacturing the same.

  It is strongly desired that the parts incorporated into mobile phones and notebook personal computers be lightweight, and as a result, the case materials for prismatic lithium-ion batteries used in these parts can replace the original steel plates and stainless steel plates. A3003 aluminum alloy plate is used. The rectangular battery case is sealed with a pure aluminum plate or an aluminum alloy plate using a laser welding technique.

  In a rectangular battery case formed by combining multiple processes of drawing and ironing, Al-Mn-based A3003 alloy is a material that can be thinned while maintaining a glossy and beautiful surface state. In a repetitive lithium ion battery, the internal pressure rises during the reaction and the temperature may rise, and the battery case material is subjected to a tensile stress due to the internal pressure depending on the use environment. Under such a use environment, the Al—Mn-based aluminum alloy plate undergoes creep deformation, resulting in a problem that the thickness of the battery case increases (swells). When the thickness deformation amount is large, there is a concern about the influence (failure, breakage, etc.) on the equipment.

  In recent years, lithium batteries are required to be lighter and have higher capacities, and there is a demand for further thinning of prismatic battery cases. Thinning is directly related to the increase in internal volume, and is an important factor for increasing the battery capacity. For this reason, with respect to the battery case, increasing the internal volume while maintaining the outer dimensions, or downsizing with the same capacity has been a problem. In addition, thickness tolerances are becoming stricter year by year, and thus high performance of materials is required.

The performance required here is: (1) resistance to creep deformation, (2) drawing-ironing during can molding, and (3) no defects such as cracks caused by laser welding. Is mentioned. So far, several aluminum alloy plates for battery cases in which Mg and Cu are added in addition to Mn have been proposed (see, for example, Patent Document 1), but all of them are for rectangular battery cases such as creep characteristics and laser weldability. The performance required as a material is not always sufficient.
JP 2004-232009 A

  In order to obtain an Al-Mn-based aluminum alloy plate having the above-mentioned performance required for battery cases, the inventors have repeatedly tested and studied the relationship between the component composition, production conditions and performance, It was found that these performances can be achieved when specific amounts of Mn, Mg and Cu are contained and the amount of impurities is regulated.

  The present invention has been made on the basis of the above knowledge, and its purpose is excellent in drawing workability and ironing workability, sealing treatment by laser welding is possible, improved creep characteristics are provided, and a charge / discharge cycle. An object of the present invention is to provide an aluminum alloy plate for a battery case that can suppress an increase in case thickness and a method for manufacturing the same.

  In order to achieve the above object, the aluminum alloy plate for battery case according to claim 1 exceeds Mn: 0.8 to 1.5%, Mg: 0.2 to 0.8%, Cu: 0.7% The total content of Mn, Mg, and Cu (Mn% + Mg% + Cu%) is 2.6% or less, Si as an impurity is 0.20% or less, and Fe is 0.2% or less. 4% or less, Zn is restricted to 0.1% or less, and the balance is Al and inevitable impurities.

  An aluminum alloy plate for a battery case according to claim 2 is the same as in claim 1, further comprising Zr: 0.01 to 0.2%, Cr: 0.01 to 0.3%, V: 0.01 to 0.2%. 1 type or 2 types or more are contained.

  The aluminum alloy sheet for battery cases according to claim 3 is characterized in that, in claim 1 or 2, it further contains Ti: 0.01 to 0.2% and B: 5 to 100 ppm.

  The method for producing an aluminum alloy plate for a battery case according to claim 4 is the production of an aluminum alloy plate having the composition according to any one of claims 1 to 3, wherein the final cold work degree is 10 to 60%, Heat treatment is performed at a temperature of 100 to 300 ° C.

  According to the present invention, a multi-stage drawing-ironing process can be formed into a rectangular case without causing fracture or appearance stains, and cracks and pinholes are generated after sealing treatment by normal laser welding. In addition, an aluminum alloy plate for a battery case that has good creep characteristics and can suppress an increase in case thickness during a charge / discharge cycle, and a method for manufacturing the same are provided.

The significance and reasons for limitation of the alloy components in the aluminum alloy plate for battery cases of the present invention will be described.
Mn: Mn is an element effective for improving creep characteristics. Moreover, it functions to make the plate surface properties during the ironing process good. The preferable content of Mn is in the range of 0.7 to 1.5%. If the Mn content is less than 0.7%, sufficient creep characteristics cannot be obtained, and the swelling of the rectangular battery case during charging and discharging is prevented. Not enough to If it exceeds 1.5%, a coarse intermetallic compound is likely to be formed during casting, and cracks are likely to occur during molding.

  Mg: Mg is an effective element for improving strength and improving moldability. The preferred Mg content is in the range of 0.2 to 8%. If the Mg content is less than 0.2%, the effect of improving strength and formability is not sufficient, and if too much Mg is present, laser weldability is obtained. Since it deteriorates, it is preferable to keep it at 0.8% or less.

  Cu: Cu is an element effective for improving creep characteristics. The preferable content of Cu is in the range of more than 0.7% and 1.2% or less. When the Cu content is 0.7% or less, the effect of improving the creep characteristics is small, and when Cu is increased, the laser weldability is lowered. Therefore, it is desirable to limit it to 1.2% or less. A more preferable content range of Cu is more than 0.8% and 1.2% or less.

  Mn% + Mg% + Cu%: In the above-mentioned range of Mn, Mg and Cu, the total content of Mn, Mg and Cu is preferably suppressed to 2.6% or less. The properties are significantly hindered, causing a decrease in productivity and casting cracks.

  Zr, Cr, V: Zr, Cr, and V are effective elements for improving the creep characteristics and miniaturizing the structure to improve the formability. Preferable contents are in the ranges of Zr: 0.01 to 0.2%, Cr: 0.01 to 0.3% and V: 0.01 to 0.2, respectively. When the content is small and each content exceeds the upper limit value, a coarse compound is produced at the time of casting, which deteriorates the moldability.

  Ti, B: Ti and B refine crystal grains to prevent cracking and rough skin during molding. Preferable contents are in the ranges of Ti: 0.01 to 0.2% and B: 5 to 100 ppm, respectively, and the effect is small if the content is less than the lower limit, and if the content exceeds the upper limit, it is coarse during casting. A compound is formed to reduce the moldability.

  Si: Si is contained as an impurity. If the Si content exceeds 0.2%, the moldability tends to be lowered, so it is preferable to regulate it to 0.2% or less. Further, reducing the amount of Si requires the use of high-purity Al ingot, leading to an increase in manufacturing cost. Therefore, it is desirably contained in the range of 0.05 to 0.2%.

  Fe: Fe is contained as an impurity. If the amount of Fe exceeds 0.4%, the formability tends to decrease, so it is preferable to regulate it to 0.4% or less. Moreover, reducing the amount of Fe requires using high-purity Al ingots, leading to an increase in manufacturing cost. Therefore, it is desirably contained in the range of 0.1 to 0.4%.

  Zn: Zn is contained as an impurity. When the amount of Zn exceeds 0.1%, creep properties deteriorate, so it is preferable to regulate it in a range of 0.1% or less.

  The aluminum alloy plate for battery case of the present invention is a step of homogenizing and hot rolling the ingot ingot according to a conventional method, then performing intermediate annealing as necessary, cold rolling, or hot rolling Then, it is manufactured through a step of cold rolling through an intermediate heat treatment for the purpose of performing an intermediate annealing and recrystallization as required. In this case, it is preferable that the final cold rolling work degree is 10% to 60%.

  If the cold rolling work degree is less than 10%, the strength of the can as a battery case may be insufficient. If the cold rolling work degree exceeds 60%, the material strength increases and the deformability also decreases. It cannot withstand the multi-step ironing process in case molding, and it is easy to cause broken bodies. A more preferable cold rolling degree is in the range of 20 to 50%. By performing a heat treatment at a temperature of 100 to 300 ° C. after the final cold rolling, the processing strain is alleviated and the moldability and creep characteristics can be improved.

  Examples of the present invention will be described below in comparison with comparative examples to demonstrate the effects. These examples show one embodiment of the present invention, and the present invention is not limited to these examples.

  An aluminum alloy having the composition shown in Table 1 is ingot-formed by semi-continuous casting, and the resulting ingot is homogenized and hot-rolled, and then cold-rolled, intermediate-annealed, and cold-rolled to a thickness of 0. A 6 mm plate was produced. The final cold rolling degree was 35%, and then heat treatment was performed at 270 ° C. In Table 1, those outside the conditions of the present invention are underlined.

Using the obtained plate material as a test material, a tensile test, a forming test, a laser welding test, and a creep test were performed by the following methods. The results are shown in Table 2.
Tensile test: A JIS No. 5 test piece was prepared and a tensile test was performed at room temperature. Those having a tensile strength of less than 200 MPa are insufficient in strength, and those having an elongation of 3% or less and those having a proof stress exceeding 250 MPa have poor moldability.
Molding test: A square case with a thickness of 6 mm, a width of 35 mm, and a height of 50 mm was molded with a wall ironing rate of 55%, and no cracks or rough skin passed (○). It was evaluated as a pass (x).

Laser welding test: A1100-O material having the same thickness as that of the test material is butt welded, and no microcrack is generated in the bead part is accepted (O), and the generated one is rejected (X). evaluated.
Creep test: Using a plate cold-rolled to the same wall thickness as that of the square case obtained by the forming test, a stress of 100 MPa was applied for 200 hours at a temperature of 90 ° C., and the amount of deformation was measured. Those with a strain of 0.3% or less after the creep test were accepted (◯), and those with a strain exceeding 0.3% were rejected (x).

  As can be seen in Table 2, each of the test materials 1 to 6 according to the present invention has a high strength exceeding a tensile strength of 200 MPa, a proof stress of 250 MPa or less, an elongation exceeding 3%, and a good moldability. It was excellent in laser weldability and creep characteristics.

  On the other hand, since the test material 7 has a small amount of added Mn, the tensile strength is low and the creep characteristics are inferior. Since the total amount of Mn, Mg, and Cu was too large, the test material 8 was cracked during casting, so that the test material could not be obtained and each test could not be performed. Since the test material 9 has too much Zn content, the creep property is inferior. The test materials 10 and 11 are inferior in moldability because the amounts of Zr and Ti added are too large. The test material 12 is inferior in laser weldability because the amount of Cu added is too large.

Claims (4)

Mn: 0.8 to 1.5%, Mg: 0.2 to 0.8%, Cu: Over 0.7% and 1.2% or less, and the total content of Mn, Mg and Cu (Mn % + Mg% + Cu%) is 2.6% or less, Si as an impurity is controlled to 0.20% or less, Fe is 0.4% or less, Zn is 0.1% or less, the balance Al and inevitable An aluminum alloy plate for a battery case, characterized by comprising impurities. Furthermore, it contains 1 type (s) or 2 or more types of Zr: 0.01-0.2%, Cr: 0.01-0.3%, V: 0.01-0.2%, It is characterized by the above-mentioned. The aluminum alloy plate for battery cases according to 1. Furthermore, Ti: 0.01-0.2% and B: 5-100ppm are contained, The aluminum alloy plate for battery cases of Claim 1 or 2 characterized by the above-mentioned. A battery characterized in that in the production of an aluminum alloy sheet having the composition according to any one of claims 1 to 3, the final cold work degree is 10 to 60%, and thereafter heat treatment is performed at a temperature of 100 to 300 ° C. A method for producing an aluminum alloy plate for a case.