JP2013014837A - Method for producing aluminum alloy foil and aluminum alloy foil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy foil enabling to enhance strength while keeping conductivity.SOLUTION: This production method of the aluminum alloy foil comprises hot rolling an aluminum alloy ingot and cold rolling to make it into a foil shape. The aluminum alloy ingot comprises chemical components in mass%, of 0.1-0.6% Si, 0.2-1.0% Fe, and the balance Al with inevitable impurities. There are no need for performing soaking treatment before the hot rolling, the temperature at the hot rolling is ≤350°C, also no need for performing annealing on the way in the cold rolling to make the foil thickness to be 20 μm or less.

Description

  The present invention relates to a method for producing an aluminum alloy foil and an aluminum alloy foil.

  Conventionally, aluminum alloy foil has been used in various fields. In recent years, from the viewpoint of being thin and conductive, for example, it is used as a secondary battery such as a lithium ion battery or a current collector of an electric double layer capacitor. Specifically, in the case of a lithium ion battery, as disclosed in Patent Documents 1 and 2, a layer containing a positive electrode active material and a binder is applied to one surface of an aluminum alloy foil as a current collector and dried. Then, the positive electrode is manufactured by rolling in order to improve the density of the positive electrode active material and the adhesion to the foil.

  The aluminum alloy foil is generally produced by subjecting an aluminum alloy ingot having a predetermined composition to a homogenization treatment, hot rolling, and cold rolling in order. Moreover, it is usual that annealing is performed once or twice during the cold rolling.

  For example, Patent Document 3 contains Si 0.01 to 0.60 mass%, Fe 0.2 to 1.0 mass%, Cu 0.05 to 0.50 mass%, Mn 0.5 to 1.5 mass%, with the balance being Al. And a step of homogenizing an aluminum alloy ingot composed of unavoidable impurities at 500 to 620 ° C. for 1 to 20 hours, and a cooling rate of the aluminum alloy ingot cooled from 500 ° C. to 400 ° C. at 35 ° C./hour or more at room temperature A method of manufacturing an aluminum alloy foil for a lithium ion battery, including a step of cooling to a temperature, a hot rolling step with a total rolling time of less than 30 minutes, a cold rolling step, and a foil rolling step, and the manufacturing method The resulting aluminum alloy foil is disclosed.

JP 2007-234277 A Japanese Patent Laid-Open No. 11-67220 JP 2011-26656 A

  However, the conventional aluminum alloy foil has problems in the following points. That is, as described above, the aluminum alloy foil receives a compressive force by rolling or the like when manufacturing a foil-use member such as a battery electrode. Therefore, a strength that does not cause unnecessary deformation or breakage against such a compressive force is required. Furthermore, in recent years, further thinning of the foil has been demanded, and in order to cope with this, it is necessary to further increase the strength of the foil.

  As a typical method for increasing the strength of the foil, there is a method of adjusting an aluminum alloy component. However, by simply adjusting the alloy components, the specific resistance of the foil increases due to the addition of alloy components other than Al, making it difficult to maintain the conductivity of the foil. As described above, the conventional aluminum alloy foil has a trade-off problem that the conductivity is lowered when the strength is increased, and the strength is lowered when the conductivity is improved.

  This invention is made | formed in view of such a background, It aims at providing the aluminum alloy foil which can aim at high intensity | strength, maintaining electroconductivity.

One aspect of the present invention is a method for producing an aluminum alloy foil that is formed into a foil by cold rolling after hot rolling the aluminum alloy ingot,
The aluminum alloy ingot has a chemical composition of mass%, Si: 0.1% to 0.6%, Fe: 0.2% to 1.0%, the balance being Al and inevitable Consisting of impurities,
Without homogenization before the hot rolling,
The temperature during the hot rolling is 350 ° C. or less,
In the method for producing an aluminum alloy foil, the cold rolling is performed without annealing in the middle, and the foil thickness is 20 μm or less.

In another aspect of the present invention, the chemical component contains, by mass, Si: 0.1% or more and 0.6% or less, Fe: 0.2% or more and 1.0% or less, and the balance is Al and inevitable. Consisting of mechanical impurities
The foil thickness is 20 μm or less,
The tensile strength is 200 MPa or more,
A specific resistance measured in liquid nitrogen is 0.45 μΩ · cm or more and 0.7 μΩ · cm or less.

  The said manufacturing method uses the aluminum alloy ingot which consists of the said specific chemical component as foil material. And this aluminum alloy ingot is hot-rolled without homogenizing. At this time, the temperature during the hot rolling is set to 350 ° C. or less. Furthermore, when performing the said cold rolling, foil thickness shall be 20 micrometers or less, without performing annealing in the middle. Therefore, precipitation of an Al—Fe—Si compound is suppressed in each manufacturing process, and Si and Fe can be kept in a solid solution state. Therefore, it is possible to obtain an aluminum alloy foil capable of increasing strength while maintaining conductivity. In addition, since no homogenization or intermediate annealing is performed, the energy saving effect is high, and the manufacturing cost can be reduced.

  The aluminum alloy foil can be obtained for the first time as long as the method for producing the aluminum alloy foil is carried out. According to the aluminum alloy foil, the tensile strength is as high as 200 MPa or more. Furthermore, the specific resistance is relatively low, 0.45 μΩcm or more and 0.7 μΩ · cm or less, and the electrical conductivity can be maintained while being high strength.

  Therefore, for example, even when a compressive force due to rolling or the like is applied during the manufacture of a foil-use member such as a battery electrode, the aluminum alloy foil is less likely to cause unnecessary plastic deformation and can ensure good conductivity. In addition, because of the strength of the foil, it is easy to meet the demand for thin foil. Therefore, if the said aluminum alloy foil is used as an electrical power collector of an electrode in secondary batteries, such as a lithium ion battery, for example, it can contribute to the high density and high energy of a battery.

  As mentioned above, according to this invention, the aluminum alloy foil which can aim at high intensity | strength can be provided, maintaining electroconductivity.

  First, the manufacturing method of the said aluminum alloy foil is demonstrated. The said manufacturing method makes it foil-like by cold-rolling, after hot-rolling an aluminum alloy ingot. Here, the aluminum alloy ingot can be prepared by melting and casting an aluminum alloy in which the chemical component is a specific component. The significance and reason for limitation of the above specific chemical component (unit: mass%, simply abbreviated as “%” in the description of the chemical component below) are as follows.

Si: 0.1% to 0.6% Si is an element necessary for improving the foil strength. When the temperature of the aluminum alloy exceeds 350 ° C. during the production of the foil, the dissolved Si and Fe are precipitated as Al—Fe—Si based compounds, the work hardenability during cold rolling is reduced, and the foil strength is reduced. Invite. Therefore, in the manufacturing method described above, hot rolling is performed under conditions of 350 ° C. or lower. In order to increase the foil strength and reduce the specific resistance of the foil to ensure conductivity, the Si content is reduced. It is necessary to be 0.1% or more and 0.6% or less. When the Si content is less than 0.1%, the specific resistance of the foil is reduced, but the strength of the foil is not improved. When the Si content exceeds 0.6%, it is difficult to further improve the foil strength, and coarse Si single-phase particles are formed. If the foil thickness is 20 μm or less, the problem of pinholes and foil breakage tends to occur. The lower limit of the Si content is preferably 0.12%. The upper limit of the Si content is preferably 0.4%.

Fe: 0.2% or more and 1.0% or less Fe is an element necessary for improving the foil strength after Si. When the temperature of the aluminum alloy exceeds 350 ° C. during the production of the foil, the dissolved Si and Fe are precipitated as Al—Fe—Si based compounds, the work hardenability during cold rolling is reduced, and the foil strength is reduced. Invite. Therefore, in the manufacturing method described above, hot rolling is performed under conditions of 350 ° C. or lower. In order to increase the foil strength and reduce the specific resistance of the foil to ensure conductivity, the Fe content should be It is necessary to be 0.2% or more and 1.0% or less. When the Fe content is less than 0.2%, the specific resistance of the foil is reduced, but the strength of the foil is not improved. When the Fe content exceeds 1.0%, it is difficult to further improve the foil strength, and a coarse Al—Fe crystallized product is formed during casting. In the above manufacturing method, as will be described later, the aluminum alloy ingot is not subjected to a homogenization treatment at a high temperature exceeding 350 ° C., so the Al—Fe-based crystallized material formed at the time of casting remains in a coarse state. It will remain up to the final foil thickness. Therefore, the problem of pinholes and foil breakage tends to occur at a foil thickness of 20 μm or less. Moreover, addition of Fe more than necessary also causes an increase in manufacturing cost. The lower limit of the Fe content is preferably 0.30%. The upper limit of the Fe content is preferably 0.80%.

  In the manufacturing method, the aluminum alloy ingot may further contain Cu: 0.01% or more and 0.25% or less in the chemical component (claim 2). The significance and reasons for limitation in this case are as follows.

Cu: 0.01% or more and 0.25% or less Cu is an element that contributes to improving the strength of the foil. In order to obtain the effect, the Cu content is preferably 0.01% or more. Note that Cu of less than 0.01% may be included as an inevitable impurity. On the other hand, when the Cu content is excessive, the specific resistance increases. Therefore, the Cu content is set to 0.25% or less. The lower limit of the Cu content is preferably 0.02%. The upper limit of the Cu content is preferably 0.18%.

  The chemical component can contain elements such as Mn, Mg, Cr, Zn, Ni, Ga, V, and Ti as inevitable impurities. However, if Mn and Mg are excessively contained, the specific resistance of the foil is increased and the electrical conductivity may be deteriorated. Therefore, it is preferable that the Mn content is 0.01% or less and the Mg content is 0.01% or less. Other elements such as Cr, Zn, Ni, Ga, V, and Ti are elements that do not contribute to an increase in specific resistance, and the content of each element is preferably 0.05% or less. In addition, if the total content of inevitable impurities as a whole is 0.15% or less, the foil strength and specific resistance are not substantially affected, and therefore it is acceptable.

  In the manufacturing method, the aluminum alloy ingot made of the chemical component is hot-rolled without being homogenized. Here, “no homogenization treatment” means that the heat treatment for homogenization as conventionally performed at a high temperature exceeding 350 ° C. is not actively performed before hot rolling. When the aluminum alloy ingot is heated to 350 ° C. or lower for hot rolling, the phenomenon that homogenization occurs not a little is allowed because it hardly affects the foil strength and specific resistance.

  In the said manufacturing method, the temperature at the time of the said hot rolling shall be 350 degrees C or less. That is, the temperature at the time of the hot rolling is set to 350 ° C. or less at the start and end of the hot rolling, which allows easy temperature measurement. The upper limit value of the temperature during the hot rolling is preferably 330 ° C., more preferably 310 ° C., from the viewpoint of improving the foil strength and reducing the specific resistance. On the other hand, the lower limit of the temperature during the hot rolling is not particularly limited, but can be set to 150 ° C. from the viewpoint of suppressing an increase in load on the rolling mill due to an increase in deformation resistance.

  Further, the holding time after reaching the start temperature of the hot rolling is not particularly limited, but from the viewpoint of easily suppressing the precipitation of the Al-Fe-Si-based compound and within 12 hours. can do. In addition, the said hot rolling may be performed once, and may be performed in multiple times, such as finishing rolling after rough rolling.

  In the said manufacturing method, an aluminum alloy foil is obtained by cold rolling after hot rolling. At this time, annealing is not performed during the cold rolling. When annealing is performed in the middle, precipitation of the Al—Fe—Si-based compound is promoted, and work hardening at the time of cold rolling is lowered, resulting in a decrease in foil strength. In addition, it is preferable not to perform the final annealing after completion | finish of cold rolling for the same reason as the said intermediate annealing.

  Further, the upper limit value of the foil thickness after the cold rolling is preferably 18 μm, more preferably 15 μm, from the viewpoint of securing electric capacity and the like. The cold rolling can be performed once or a plurality of times. The final rolling rate in the cold rolling is preferably 90% or more, and more preferably 95% or more, from the viewpoint of improving the foil strength. The final rolling rate is 100 × (the thickness of the hot rolled sheet before cold rolling−the thickness of the aluminum alloy foil after the final cold rolling) / (of the hot rolled sheet before the cold rolling). It is a value calculated from (plate thickness).

  In the manufacturing method, the aluminum alloy foil can be used for a current collector of a battery electrode. In this case, an electrode active material is attached to the surface of the aluminum alloy foil as a current collector. Specifically, a layer containing an electrode active material is applied to the surface of the aluminum alloy foil, and a compressive force by rolling or the like is applied after drying. Even in such a case, according to the manufacturing method, unnecessary plastic deformation hardly occurs due to the compressive force, so that the electrode active material is hardly peeled off. In addition, good conductivity can be secured. In addition, because of the strength of the foil, it is easy to meet the demand for thin foil. Therefore, it can contribute to high density and high energy of secondary batteries such as lithium ion batteries.

  Next, the aluminum alloy foil will be described. The said aluminum alloy foil can be suitably obtained with the manufacturing method mentioned above. In the aluminum alloy foil, the chemical component may further contain Cu: 0.01% or more and 0.25% or less (Claim 5). In addition, about the meaning of the chemical component of aluminum alloy foil, and the reason for limitation apply to the content demonstrated by the said manufacturing method, description is abbreviate | omitted.

  The upper limit value of the foil thickness is preferably 18 μm, more preferably 15 μm, from the viewpoint of reducing the thickness and contributing to downsizing of the battery and the like. On the other hand, the lower limit of the foil thickness is preferably 10 μm, and more preferably 12 μm, from the viewpoint of ease of handling at the time of manufacturing a foil-use member such as during battery manufacture. Moreover, the said tensile strength shall be 200 Mpa or more. Preferably, it is 210 MPa or more. When the tensile strength is less than 200 MPa, for example, when the foil is thinned, unnecessary plastic deformation is likely to occur when a compressive force is applied to the foil by rolling or the like. The upper limit value of the tensile strength is not limited, but can be determined in consideration of the balance with the specific strength. The upper limit of tensile strength can be 270 MPa. The tensile strength is a value measured according to JIS Z2241.

  The specific resistance has a correlation with the solid solution amount of Si and Fe as alloy components. When the specific resistance is less than 0.45 μΩ · cm, it is difficult to improve the strength by work hardening at the time of manufacturing the foil, and it is difficult to set the tensile strength to 200 MPa or more. On the other hand, when the specific resistance is increased, the strength is improved by work hardening at the time of manufacturing the foil and high strength is obtained. However, the specific resistance increases and the conductivity tends to decrease. Therefore, the upper limit is set to 0.7 μΩ · cm, which is about 60% of the specific resistance of the 3003 series aluminum alloy foil, which is a relatively high strength aluminum alloy foil. The upper limit value of the specific resistance is preferably 0.69 μΩ · cm, and more preferably 0.68 μΩ · cm. The specific resistance is a value measured by the double bridge method in accordance with JIS H0505.

  The manufacturing method of the aluminum alloy foil and the aluminum alloy foil according to the examples will be described below.

Example 1
The manufacturing method of the aluminum alloy foil of this example is a manufacturing method of the aluminum alloy foil made into a foil shape by hot rolling an aluminum alloy ingot and then cold rolling. The aluminum alloy ingot is composed of alloys A to K having chemical components shown in Table 1. There is no homogenization treatment before the hot rolling, the temperature during the hot rolling is 350 ° C. or less, the cold rolling is performed without annealing in the middle, and the foil thickness is 20 μm or less. And

  Moreover, the aluminum alloy foil of this example was obtained by the manufacturing method of this example, and consists of alloys A to K having chemical components shown in Table 1. The foil thickness is 20 μm or less, the tensile strength is 200 MPa or more, and the specific resistance measured in liquid nitrogen is 0.45 μΩ · cm to 0.7 μΩ · cm. This will be specifically described below.

  An aluminum alloy ingot was prepared by ingot forming and chamfering an aluminum alloy having chemical components shown in Table 1 by a semi-continuous casting method. Of the aluminum alloys having chemical components shown in Table 1, alloys A to K are aluminum alloys having chemical components suitable for the examples, and alloys L to Q are aluminum alloys having chemical components as comparative examples.

  The prepared aluminum alloy ingot was hot-rolled without subjecting it to a homogenization treatment to obtain a hot-rolled plate having a thickness of 2 mm. At this time, in hot rolling, rough rolling and finish rolling were continuously performed. In the hot rolling, the aluminum alloy ingot before being subjected to the rough rolling is heated to 350 ° C. and held for 6 hours to set the rough rolling start temperature (hot rolling start temperature) to 350 ° C. . The end temperature of rough rolling (temperature during hot rolling) was 320 ° C., and the end temperature of finish rolling (end temperature of hot rolling) was 278 ° C. In this way, in this example, not only the hot rolling start temperature and end temperature, but also the rough rolling end temperature, which is the intermediate temperature of hot rolling, that is, the finish rolling start temperature, is set to 350 ° C. or less.

  Subsequently, cold rolling was repeatedly performed without annealing in the middle to obtain an aluminum alloy foil having a foil thickness of 12 μm. The final rolling rate in the cold rolling is 100 × (the thickness of the hot rolled sheet before cold rolling is 2000 μm−the thickness of the aluminum alloy foil after the final cold rolling is 12 μm) / (before the cold rolling) The thickness of the hot-rolled sheet is 2000 μm) = 99.4%.

  Next, the obtained aluminum alloy foil was used as a test material, and tensile strength, proof stress and elongation, and specific resistance (electric resistivity) were measured. Specifically, the tensile strength, proof stress and elongation were measured in accordance with JIS Z2241, by collecting a JIS No. 5 test piece from the test material. The specific resistance was measured by a double bridge method according to JIS H0505. In order to remove the influence of the ambient temperature, the specific resistance was measured in liquid nitrogen. In addition, in order to investigate the foil rolling situation, lighting was applied from the back of the test material, and the occurrence of pinholes was also investigated according to the presence or absence of light leakage. The results are shown in Table 2. Note that the test materials E1 to E11 are examples, and the test materials C1 to C4 are comparative examples.

  As shown in Table 2, since the test material C1 used an alloy L having an Si content of less than 0.1% and an Fe content of less than 0.2%, the strength improvement effect was not obtained, and the tensile strength was low. It was as low as less than 200 MPa.

  Since the test material C2 used the alloy M having a Si content exceeding 0.6%, coarse Si single-phase particles were formed, and pinholes were generated thereby.

  Since the test material C3 used the alloy N having an Fe content of less than 0.2%, the strength improvement effect was not obtained, and the tensile strength was as low as less than 200 MPa.

  Since the test material C4 used the alloy O in which the Fe content exceeds 1.0%, coarse Al—Fe-based particles were formed, and pinholes were thereby generated.

  On the other hand, the test materials E1 to E11 using the alloys A to K having the specific chemical components described above and manufactured based on the specific conditions are all 12 μm in thickness and have a tensile strength of 200 MPa or more. The specific resistance measured in liquid nitrogen was 0.45 μΩ · cm or more and 0.7 μΩ · cm or less.

  Therefore, according to this example, it is possible to provide an aluminum alloy foil capable of increasing strength while maintaining conductivity. Moreover, even if the thickness is reduced, the strength is high, and problems such as pinholes and foil breakage can be avoided.

(Example 2)
This example mainly investigates the temperature conditions at the time of hot rolling, the presence or absence of a homogenization treatment, the influence of intermediate annealing at the time of cold rolling, and the like.

  An aluminum alloy ingot was prepared by ingot forming and chamfering aluminum alloy B having chemical components shown in Table 1 by a semi-continuous casting method. In addition, a comparative aluminum alloy ingot was also prepared by ingoting and chamfering 1050 alloy (alloy P) and 3003 alloy (alloy Q) of conventional alloys shown in Table 1 by a semi-continuous casting method. .

  Using the prepared aluminum alloy ingot, an aluminum alloy foil having a foil thickness of 12 μm was produced under the production conditions shown in Table 3. About the obtained aluminum alloy foil, it carried out similarly to Example 1, and measured tensile strength, yield strength, elongation, and specific resistance, and investigated foil rolling condition (presence of pin pole generation | occurrence | production). The results are shown in Table 4. Note that the test materials E12 and E13 are examples, and the test materials C5 to C11 are comparative examples.

  As shown in Table 4, since the test materials C5 to C7 had a hot rolling start temperature of over 350 ° C. during the hot rolling, the tensile strength was low at less than 200 MPa.

  The test material C8 was produced by performing a homogenization treatment at a high temperature of 500 ° C. exceeding 350 ° C. before the start of hot rolling. Therefore, an Al—Fe—Si-based compound was formed, the amount of Si and Fe dissolved, and the tensile strength was lowered to less than 200 MPa.

  The test material C9 was manufactured by performing annealing at a high temperature of 380 ° C. exceeding 350 ° C. in the course of cold rolling during the cold rolling, although the temperature during hot rolling was 350 ° C. or less. It is. Therefore, precipitation of the Al—Fe—Si compound was promoted, and the tensile strength was lowered to less than 200 MPa.

  As test materials C10 and C11, 1050 alloy (alloy P) and 3003 alloy (alloy Q), which are conventional alloys, are used, and further homogenized at a high temperature of 500 ° C. exceeding 350 ° C. before the start of hot rolling. It was produced. Therefore, the test material C10 did not reach a tensile strength of 200 MPa. Moreover, the test material C11 had a very high specific resistance of 1.2 μΩ · cm or more, and was inferior in conductivity.

  In contrast, the test materials E12 and E13 produced using the above-described specific chemical component alloy B and based on the specific conditions have a thickness of 12 μm, a tensile strength of 200 MPa or more, and a liquid. The specific resistance measured in nitrogen was 0.45 μΩ · cm or more and 0.7 μΩ · cm or less.

  Therefore, according to this example, it is possible to provide an aluminum alloy foil capable of increasing strength while maintaining conductivity. Moreover, even if the thickness is reduced, the strength is high, and problems such as pinholes and foil breakage can be avoided.

  As mentioned above, although the Example was described, this invention is not limited by the said Example, A various deformation | transformation can be performed within the range which does not impair the meaning of this invention.

Claims (5)

A method for producing an aluminum alloy foil in which a foil shape is obtained by hot rolling an aluminum alloy ingot and then cold rolling,
The aluminum alloy ingot has a chemical composition of mass%, Si: 0.1% to 0.6%, Fe: 0.2% to 1.0%, the balance being Al and inevitable Consisting of impurities,
Without homogenization before the hot rolling,
The temperature during the hot rolling is 350 ° C. or less,
The manufacturing method of the aluminum alloy foil characterized by performing the said cold rolling without annealing in the middle and making foil thickness into 20 micrometers or less. In the manufacturing method of the aluminum alloy foil of Claim 1,
The said aluminum alloy ingot is a manufacturing method of the aluminum alloy foil characterized by the said chemical component further containing Cu: 0.01% or more and 0.25% or less by the mass%. In the manufacturing method of the aluminum alloy foil of Claim 1 or 2,
The said aluminum alloy foil is for the collectors of a battery electrode, The manufacturing method of the aluminum alloy foil characterized by the above-mentioned. The chemical component is, by mass%, Si: 0.1% or more and 0.6% or less, Fe: 0.2% or more and 1.0% or less, and the balance consists of Al and inevitable impurities,
The foil thickness is 20 μm or less,
The tensile strength is 200 MPa or more,
An aluminum alloy foil characterized by having a specific resistance measured in liquid nitrogen of 0.45 μΩ · cm to 0.7 μΩ · cm. In the aluminum alloy foil according to claim 4,
The aluminum alloy foil, wherein the chemical component further contains Cu: 0.01% or more and 0.25% or less by mass%.