JP2016156059A - Aluminum alloy foil excellent in elongation property and method for producing aluminum foil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy foil reduced in anisotropy, having excellent elongation properties and having excellent moldability.SOLUTION: Provided is an aluminum alloy foil having a composition containing, by mass, 0.8 to 1.8% Fe, and the balance Al with inevitable impurities, and in which the content of Si is regulated to 0.01% or lower in the inevitable impurities, in which the average crystal grain size is 5 μ or lower, also the ratio of the maximum crystal grain size/the average crystal grain size is 2.5 or lower and the elongation in the respective directions of 0°, 45° and 90° to the rolling direction is 25% or higher. In its production, upon cold rolling, process annealing in which temperature rising rate is 10 to 250°C/s, heating temperature is 450 to 550°C, holding time is 5 s or lower and cooling velocity is 20 to 200°C/s is performed, and thereafter, final cold rolling is performed at the final cold rolling ratio of 90% or higher.SELECTED DRAWING: None

Description

  The present invention relates to an aluminum alloy foil having excellent elongation characteristics and a method for producing the aluminum foil.

Aluminum foil used for packaging materials for batteries such as food and lithium ion secondary batteries is greatly deformed by press molding or the like. For this reason, materials having a large elongation have been demanded, and soft foils of JIS 1000 series alloys such as 1N30 and 8000 series alloys such as 8079 and 8021 are used. Patent Document 1 discloses an aluminum alloy foil that contains Fe and Mg, and whose Si content is regulated to 0.10% or less.
Patent Document 2 discloses an aluminum alloy foil containing Fe and Si, Cu and Mn being restricted to 0.2% as upper limits, and the size of crystal grains being restricted.

Japanese Patent Laid-Open No. 3-191042 JP 2014-65956 A

For elongation, the aluminum alloy foil is not deformed in one direction, and so-called stretch forming is often performed, so that not only the direction parallel to the rolling direction generally used as the elongation value of the material is used. The elongation in each direction such as 45 ° and 90 ° is also required to be high. Recently, the thickness of the packaging material has been reduced, especially in the field of battery packaging materials.
However, the aluminum alloy foil shown in Patent Document 1 does not have sufficient uniformity of elongation in each direction, and uniform deformation becomes difficult by overhanging or the like.
In addition, Patent Document 2 shows a sufficient elongation, but an example in which Cu and Mn are added with an upper limit of 0.2% for refining crystal grains is shown. Even if it is a very small amount, the rollability is lowered, and there is a concern that the productivity is lowered because the risk of breakage during rolling due to the occurrence of edge cracks increases. In addition, even with a small amount of high Fe material close to 1.5%, the addition of Mn causes coarsening of the Al-Fe-Mn-based crystallized material. The risk that becomes the starting point of the occurrence of holes is increased.

  The present invention has been made against the background of the above circumstances, and is an aluminum alloy foil excellent in elongation characteristics that has high elongation in each direction, is uniform, and can be uniformly deformed during molding, and the aluminum foil It aims at providing the manufacturing method of.

  That is, among the aluminum alloy foils excellent in elongation characteristics of the present invention, the first present invention contains Fe: 0.8 mass% or more and 1.8 mass% or less, and the balance consists of Al and inevitable impurities, In the inevitable impurities, Si has a composition regulated to 0.03% by mass or less, the average crystal grain size is 6 μm or less, the maximum crystal grain size / average crystal grain size ratio is 2.5 or less, and the rolling direction The elongation in each direction of 0 °, 45 °, and 90 ° is 25% or more.

  The aluminum alloy foil having excellent elongation characteristics according to the second aspect of the present invention is the unavoidable impurity in the composition according to the first aspect of the present invention, Cu: 0.01 mass% or less, Mn: 0.01 mass% or less. It is characterized by being.

  According to a third aspect of the present invention, there is provided a method for producing an aluminum alloy foil having excellent elongation characteristics. An aluminum alloy having the composition described in the first aspect of the present invention or the second aspect of the present invention is prepared, and cold rolling using the alloy is performed. In this case, the intermediate annealing is performed, and then the final cold rolling is performed at a final cold rolling rate of 93% or more.

  According to a fourth aspect of the present invention, there is provided a method for producing an aluminum alloy foil having excellent elongation characteristics. In the third aspect of the present invention, the aluminum alloy is homogenized at a temperature of 500 to 560 ° C. for 6 to 12 hours. Features.

  Next, the contents defined in the present invention will be described. In addition, all component content demonstrated below is shown by mass ratio.

Si: 0.03% or less In an aluminum alloy foil characterized by high formability, Si is not an element that is actively added because it increases the risk of generating coarse intermetallic compounds during casting. If only the coarse intermetallic compound is prevented, the upper limit may be about 0.1%. However, in the present invention, by adding Fe to the upper limit of 0.03% or less, Both grain and elongation anisotropy can be achieved. In addition, the regulation of Si has also been confirmed to have an effect of uniforming the size of crystal grains. When the amount of Si is large, even if the average crystal grain size can be reduced, the maximum crystal grain size / average crystal grain size ratio is increased. , Uniform deformation is not possible. For the same reason, it is desirable to further limit the Si content to 0.02% or less.

・ Fe: 0.8-1.8%
Fe crystallizes as an Al—Fe intermetallic compound at the time of casting and has the effect of making crystal grains fine by using it as a nucleus. If it is less than 0.8% by mass, the effect of miniaturization is low, and when intermediate annealing is performed in a continuous annealing line, there is a concern that the crystal grain size becomes uneven and the elongation decreases. If it exceeds 1.8% by mass, the effect of crystal grain refinement is saturated or reduced, and the size of the Al—Fe-based compound produced during casting becomes large, and the elongation and rollability of the foil are reduced. In particular, the lower limit is preferably 1.0% by mass, and the upper limit is preferably 1.6% by mass.

The average crystal grain size is 6 μm or less, and the maximum crystal grain size / average crystal grain size ratio is 2.5 or less. The crystal grain size and anisotropy have an important relationship with the elongation of the foil. By making the crystal grain size finer, the material is easily deformed uniformly. Particularly, since the foil product is thin, the contribution of this crystal grain refinement is large. However, when coarse crystal grains are mixed in fine crystal grains, stress concentration occurs during forming, constriction occurs early, and breakage occurs. When the average crystal grain size is 6 μm or less and the maximum crystal grain size / average crystal grain size ratio is 2.5 or less, stable high formability can be ensured.

Elongation in each direction of 0 °, 45 °, and 90 ° is 25% or more with respect to the rolling direction. For high formability, the elongation of the foil is important. Especially, the direction parallel to the rolling direction is 0 °, 45 °, and It is important that the elongation is high in each direction of 90 ° which is the normal direction of the rolling direction.
For example, when an Al—Fe alloy foil is produced without restricting Si to 0.01% or less, elongation anisotropy of 0 ° and 90 ° elongation is low and 45 ° elongation is high. Such a foil having elongation anisotropy is low in molding.

Cu: 0.01% or less Although Cu contributes to refinement of crystal grains if it is in a very small amount, this alloy has a high density of Al-Fe-based intermetallic compounds that are the core of recrystallization, Crystal grains can be sufficiently refined without relying on Cu. Even if Cu is contained in excess of 0.01%, it hardly contributes to the strength of the final soft foil, but the rollability is lowered due to work hardening during cold rolling, and the risk of breakage due to edge crack growth is increased. . Therefore, when Cu is contained, the upper limit is desirably 0.01%.

・ Mn: 0.01% or less Mn contributes to refinement of crystal grains as well as Cu, but in the alloy like this application in which Fe is added by 0.8% or more, Al—Fe—Mn based metal is added by adding Mn. The intermetallic compound becomes coarse, causing breakage and pinholes during rolling, and if the foil is thin, it may lead to cracking during molding. If it is 0.01% or less, the above risk is almost avoided. Therefore, when Mn is contained, the upper limit is desirably 0.01%.

・ Intermediate annealing Intermediate annealing must be performed from the viewpoint of anisotropy. Intermediate annealing methods include batch and CAL (continuous annealing), and the intermediate annealing method is preferably a batch method from the viewpoint of elongation anisotropy.
If the Si content is extremely low at less than 0.001%, the solid solution amount of the solute element is low in the batch type, and dynamic recovery is also promoted. However, the crystal grain structure is not refined, and after the final annealing, an extremely coarse recrystallized grain structure (average crystal grain size of several tens of μm) is obtained, and the elongation is extremely lowered. Therefore, when the Si content is less than 0.001%, CAL annealing must be selected.
In the present application, both batch and CAL can be used in the range of Si content of 0.001% to 0.03%. However, when intermediate annealing of an Al—Fe alloy that does not regulate Si as much as the present invention is performed by CAL. Although the crystal grains become finer, the anisotropy of elongation becomes significant and the maximum crystal grain size / average crystal grain size ratio becomes large.

  As described above, according to the present invention, the aluminum alloy foil has a small elongation anisotropy and has excellent elongation characteristics, and can be molded well.

Hereinafter, an embodiment of the present invention will be described.
First, an aluminum alloy is melted with the composition specified in the present invention. Si can be regulated by careful selection of materials, but the method is not particularly limited.
An appropriate method such as a semi-continuous casting method can be adopted as a method for melting the aluminum alloy, and the present invention is not particularly limited. For an aluminum alloy ingot, for example, a homogenization treatment can be performed under conditions of a temperature of 500 to 560 ° C. and a holding time of 6 to 12 hours.

A rolled aluminum alloy material is obtained by performing hot rolling on an ingot of the aluminum alloy that has been subjected to the homogenization treatment or has not been subjected to the homogenization treatment. In addition, what was made into the hot-rolled material by continuous casting may be used.
For example, cold rolling is performed on the hot-rolled aluminum alloy material to obtain an aluminum alloy foil having a final thickness of 10 to 40 μm.
In the middle of the cold rolling, it is necessary to perform an intermediate annealing on the aluminum alloy material. There are two types of intermediate annealing methods: batch annealing (Batch Annealing, BATCH) in which coils are placed in a furnace and held for a certain period of time, and annealing in which materials are rapidly heated and rapidly cooled by a continuous annealing line (Continuous Annealing Line, CAL). Although a system is known, a batch system is preferable from the viewpoint of elongation anisotropy. (However, in the case of an alloy having a Si content of less than 0.001%, CAL annealing must be selected.)
In the case of the batch type in this embodiment, the temperature is 350 to 450 ° C. for 3 to 6 hours, and for CAL annealing, the heating rate is 100 to 250 ° C./second, the heating temperature is 450 to 550 ° C., the holding time is none or 5 2 seconds or less, cooling rate: 20 to 200 ° C./second. Further, the intermediate annealing can be performed twice or more.

  By setting the cold rolling rate from the intermediate annealing to the final thickness to 93% or more as the final cold rolling rate, the crystal grains after the final annealing are refined and the elongation is improved. Moreover, about 40% or more is ensured about the cold rolling rate from hot rolling to intermediate annealing, and the crystal grain size at the time of intermediate annealing can be made uniform.

  The obtained aluminum alloy foil has an average crystal grain size of 5 μm or less, a maximum crystal grain size / average crystal grain size ratio of 2.5 or less, a tensile strength of 90 MPa or more, 0 ° with respect to the rolling direction, 45 It has the characteristic that the elongation in each direction of ° and 90 ° is 25% or more.

Aluminum alloys shown in Table 1 (the balance being Al and inevitable impurities) were melted by a semi-continuous casting method, and homogenized at a temperature of 560 ° C. and a holding time of 6 hours. Thereafter, a 7 mm aluminum alloy hot-rolled sheet was produced by hot rolling, and the aluminum alloy hot-rolled sheet was subjected to intermediate annealing under the conditions described later in the middle of cold rolling.
As for the intermediate annealing, the batch-type condition is 360 ° C. × 4 hours, and in the continuous annealing line (CAL), the heating rate is 70 ° C./second, the heating temperature is 500 ° C., the holding time is 0 second, and the cooling rate. : 50 ° C./second.

After the intermediate annealing, cold rolling was performed at a final cold rolling rate shown in Table 2, and an aluminum alloy foil having a width of 1200 mm and a final thickness of 40 μm was produced. The aluminum alloy foil was subjected to batch annealing at 350 ° C. for 10 hours to obtain a test material.
Example No. 1-9, Comparative Example No. Tensile test was performed on 10 to 14 specimens to evaluate elongation. The tensile test is based on JIS Z2241, taking a JIS No. 5 test piece from the sample so that the elongation in each direction of 0 °, 45 ° and 90 ° with respect to the rolling direction can be measured. The test was conducted at a tensile speed of 2 mm / min. The calculation of the elongation rate is as follows. First, before the test, two lines are marked at the center of the test piece in the vertical direction of the test piece at intervals of 50 mm, which is the distance between the gauge points. After the test, measure the distance between the marks by bringing the fracture surface of the aluminum alloy foil together, and then divide the original distance between the gauge points (50 mm) by the distance between the gauge points (50 mm). The elongation (%) was obtained. The measurement results are shown in Table 2.

Claims (4)

  Fe: 0.8 mass% or more and 1.8 mass% or less, with the balance being Al and inevitable impurities, having a composition regulated to Si: 0.03 mass% or less in the inevitable impurities, and an average crystal The grain size is 6 μm or less, the maximum crystal grain size / average crystal grain size ratio is 2.5 or less, and the elongation in each direction of 0 °, 45 °, and 90 ° with respect to the rolling direction is 25% or more. An aluminum alloy foil with excellent elongation characteristics.   2. The aluminum alloy foil according to claim 1, wherein, in the inevitable impurities in the composition, Cu: 0.01% by mass or less and Mn: 0.01% by mass or less.   An aluminum alloy having the composition according to claim 1 or 2 is prepared, intermediate annealing is performed during cold rolling using the alloy, and then final cold rolling is performed at a final cold rolling rate of 93% or more. The manufacturing method of the aluminum alloy foil excellent in the elongation characteristic characterized by the above-mentioned.   The method for producing an aluminum alloy foil excellent in elongation characteristics according to claim 3, wherein the aluminum alloy is homogenized at a temperature of 500 to 560 ° C for 6 to 12 hours.