JP2015203154A - Aluminum alloy soft foil and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy soft foil having unconventionally high elongation by achieving uniformalization and miniaturization of crystal particle sizes while reducing anisotropy of elongation and a manufacturing method thereof.SOLUTION: In manufacturing the aluminum alloy soft foil having a composition consisting of, by mass%, Fe: 1.4% to 2.0% inclusive, the Si content: 0.15% or less and the balance Al with inevitable impurities, intermediate firing is performed by continuous firing in the middle of cold rolling.

Description

  The present invention relates to an aluminum alloy soft foil used as a medicine, food, a battery packaging material, and the like, and a method for producing the same.

The aluminum alloy 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, a material having a large elongation has been demanded in the past, and in recent years, thinning of the foil has been progressing in the battery packaging field.
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.

As described above, conventionally, an aluminum alloy soft foil for a packaging material is required to have a high elongation and a thin wall.
Conventionally, in order to increase the elongation, what has been subjected to intermediate annealing in the middle of cold rolling has been proposed (see Patent Documents 1, 2, and 3), and the intermediate annealing in the middle of cold rolling is omitted from the viewpoint of manufacturing efficiency. Is also known (Patent Document 4).

International Publication No. 2012/036181 JP 2012-52158 A Japanese Patent Laid-Open No. 2003-239052 JP 2002-224710 A

  However, when intermediate annealing is not performed, the foil grain size can be uniformized and refined, but elongation anisotropy appears, only the elongation in a specific direction is improved, and the other direction is rather lowered Occurs. On the other hand, in the case of performing the intermediate annealing, there is a problem that the crystal grain size becomes coarse and non-uniform by heating for a long time, resulting in a decrease in elongation.

  The present invention has been made on the basis of the above circumstances, and by realizing uniform and fine grain size while reducing the anisotropy of elongation, an aluminum alloy soft foil having high elongation and its production It aims to provide a method.

  That is, among the aluminum alloy soft foils of the present invention, the first present invention contains, by mass%, Fe: 1.4% or more and 2.0% or less, Si: 0.15% or less, with the balance being Al. And an inevitable impurity composition, the average crystal grain size is 5 μm or less, and the maximum crystal grain size / average crystal grain size ratio is 3.5 or less.

  The aluminum alloy soft foil of the second invention is characterized in that, in the first invention, the elongation in each direction of 0, 45, 90 ° with respect to the rolling direction is 20% or more at a thickness of 40 μm. .

  The manufacturing method of the aluminum alloy soft foil of the third aspect of the present invention includes, in mass%, Fe: 1.4% or more and 2.0% or less, Si: 0.15% or less, and the balance from Al and inevitable impurities. An aluminum alloy having a composition as described above is cold-rolled, and intermediate annealing is performed by continuous annealing in the middle of cold rolling.

  The method for producing an aluminum alloy soft foil of the fourth invention is the method according to the third invention, wherein the intermediate annealing is performed at a heating rate of 10 to 250 ° C./second, a heating temperature of 400 to 550 ° C., and a holding time. None or holding time: 5 seconds or less, cooling rate: 20 to 200 ° C./second.

  According to a fifth aspect of the present invention, there is provided a method for producing the aluminum alloy soft foil according to the third or fourth aspect of the present invention, wherein the aluminum alloy is melted and then heated at a temperature of 430 to 530 ° C. for 3 to 7 hours. It is characterized by performing the conversion process.

  The composition and production conditions in the present invention will be described below. In addition, all the following component content is shown by the mass%.

Fe: 1.4% or more and 2.0% or less Fe has an effect of crystallizing as an Al—Fe intermetallic compound at the time of casting, and using it as a nucleus to refine crystal grains. If it is less than 1.4%, the effect of miniaturization is low, and when combined with intermediate annealing by a continuous annealing line, coarse crystal grains are generated non-uniformly and elongation is lowered. On the other hand, if it exceeds 2.0%, 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. Therefore, the Fe content is set to 1.4% or more and 2.0% or less. For the same reason, the Fe content is desirably 1.5% or more and desirably 1.8% by mass or less.

Si: 0.15% or less Si may be added for the purpose of increasing the strength of the foil if it is in a small amount, but in the present invention, if it exceeds 0.15%, Al—Fe— produced during casting. When the size of the Si-based compound is increased, the elongation of the foil is reduced, and the foil thickness is thin, the fracture starts from the compound and the rollability is reduced. For this reason, the Si content is limited to 0.15% or less. For the same reason, the Si content is desirably 0.10% or less.
Note that the content of Si is limited to a predetermined value or less as described above, and Si may or may not be intentionally contained.

As described above, the aluminum alloy that constitutes the aluminum alloy soft foil contains Fe and has a composition in which the content of Si is limited and the balance is composed of Al and inevitable impurities. It may have.
When other components such as Cu and Mg are added, the total content is limited to 0.15% or less. If it exceeds 0.15%, the material is cured, and there is a concern that the elongation is reduced.

The average crystal grain size is 5 μm or less, and the maximum crystal grain size / average crystal grain size ratio is 3.5 or less. By refining the average crystal grain size after final annealing to 5 μm or less, the foil becomes uniform during molding. Deformation and elongation are improved. However, when coarse grains exceeding 3.5 times the average grain size are present in the fine grain structure, deformation around the grains becomes non-uniform and elongation decreases.

Next, the manufacturing method of the aluminum alloy soft foil of this invention is demonstrated.
In the case of the said manufacture, a homogenization process can be performed with respect to the molten aluminum alloy. The conditions for the homogenization treatment are not particularly limited. For example, the temperature can be set to 430 to 550 ° C., and the holding time can be set to 3 to 7 hours. By the homogenization treatment, Al—Fe-based precipitates are finely dispersed in the matrix, and fine recrystallized grains are obtained during intermediate annealing and final annealing, thereby improving elongation. Furthermore, the elongation can be further improved by setting the temperature of the homogenization treatment to 430 to 530 ° C.

Intermediate annealing Intermediate annealing is performed during the cold rolling by continuous annealing.
In general, the intermediate annealing is mainly performed in order to remove the distortion of the material and restore the rollability.
When cold rolling at a high pressure is performed, a rolling texture of the material develops and the elongation anisotropy of the foil becomes remarkable. However, by performing intermediate annealing during cold rolling, a recrystallized structure can be developed and the elongation anisotropy of the foil can be improved. As the method of intermediate annealing, generally, batch annealing (Bach Annealing, BACH) in which a coil is put into a furnace and held for a certain period of time, and annealing in which a material is rapidly heated / cooled rapidly by a continuous annealing line (Continuous Annealing Line, CAL). There are two known methods. Either method has an effect of improving elongation anisotropy. However, batch annealing tends to increase the grain size as compared with annealing by continuous annealing, and in particular, the effect of limiting the content of Fe and Si is significantly reduced. By restricting Fe and Si and performing intermediate annealing by continuous annealing, it is possible to achieve coexistence of crystal grain size uniformity and refinement, and an unprecedented effect is obtained.

The conditions for the intermediate annealing are, for example, a heating rate: 10 to 250 ° C./second, a heating temperature: 400 ° C. to 550 ° C., no holding time or holding time: 5 seconds or less, and a cooling rate: 20 to 200 ° C./second. be able to.
When the heating rate is slower than 10 ° C./second, the accumulated energy introduced during cold rolling is released in the heating process, so the recrystallization nucleation rate decreases and the crystal grain size after annealing increases, The elongation of the foil after final annealing is 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. For this reason, it is desirable that the rate of temperature increase be 10 to 250 ° C./second. For the same reason, it is more desirable that the lower limit is 20 ° C./second and the upper limit is 200 ° C./second.

Further, if the heating temperature is less than 400 ° C., it takes a long time until the recrystallization is completed, so that there is a concern about the coarsening of crystal grains and the production efficiency of the aluminum alloy plate is lowered. On the other hand, when the heating temperature exceeds 550 ° C., local melting occurs in the material during annealing, and there is a possibility that rollability and material characteristics may be deteriorated. For this reason, it is desirable that the heating temperature be 400 ° C to 550 ° C. For the same reason, it is more desirable to set the lower limit to 420 ° C. and the upper limit to 520 ° C.
Further, it is not necessary to provide a holding time, but if the holding time exceeds 5 seconds, there is a concern about the coarsening of recrystallized grains. For this reason, it is desirable that no holding time or holding time: 5 seconds or less. For the same reason, it is more desirable to set the upper limit to 3 seconds or less. The continuous annealing line rapidly heats the material charged from the inlet side and starts cooling immediately after reaching the target temperature, so there may be nothing that can be called holding time (holding time 0 second).

  As described above, according to the present invention, an aluminum alloy soft foil that achieves uniform and fine crystal grain size while reducing the anisotropy of elongation can be obtained, and high elongation characteristics can be obtained.

Hereinafter, an embodiment of the present invention will be described.
The aluminum alloy used as the material for the aluminum alloy soft foil contains Fe: 1.4% or more and 2.0% or less, Si content: 0.15% or less, and the balance is Al. In order to obtain a composition composed of inevitable impurities, it can be cast and melted by a conventional method such as a semi-continuous casting method.

  For an aluminum alloy ingot, for example, a homogenization treatment is performed under conditions of a temperature of 430 to 550 ° C. and a holding time of 3 to 7 hours.

The aluminum alloy ingot after the homogenization treatment is hot-rolled to obtain an aluminum alloy hot rolled material.
In hot rolling, it is desirable that the finishing temperature is 280 ° C. or lower which is lower than the recrystallization temperature of the aluminum alloy. By finishing below the recrystallization temperature, the grain structure after hot rolling becomes a uniform and fine fiber structure, the stability of final cold rolling is improved, and variation in the elongation of the final product foil is suppressed. .
However, in the present invention, each condition in the hot rolling is not particularly limited.

Cold rolling is performed on the hot rolled material. In cold rolling, rolling is performed until the finished sheet thickness is, for example, 0.4 to 1.0 mm.
In the finish rolling in the cold rolling, the aluminum alloy plate having a finished thickness is rolled and rolled, and the final thickness is set to 15 to 100 μm, for example.
In the final cold rolling (including finish rolling?) Performed after the intermediate annealing described later, the rolling rate is desirably 80% or more in order to refine the grain structure after the final annealing described later.

  In the middle of the cold rolling (usually in the middle of cold rolling before finish rolling), intermediate annealing by continuous annealing is performed on the aluminum alloy sheet. The conditions for the intermediate annealing are, for example, a heating rate: 10 to 250 ° C./second, a heating temperature: 400 ° C. to 550 ° C., no holding time or holding time: 5 seconds or less, and a cooling rate: 20 to 200 ° C./second. . The intermediate annealing can be performed twice or more.

After performing the said intermediate annealing, final cold rolling is implemented. The final cold rolling is performed at a temperature at which the material is completely recrystallized, for example, at 270 to 400 ° C. for 4 hours or more. When removing rolling oil completely, 10 hours or more are preferable.
The final annealing can be performed by batch annealing.

  In the aluminum alloy soft foil of the present invention, the crystal grain size is made uniform and refined, the anisotropy of elongation is reduced, and preferably at 0 °, 45 ° with respect to the rolling direction at a thickness of 40 μm. The elongation in each direction of ° and 90 ° is 20% or more.

  An aluminum alloy having the composition shown in Table 1 (the balance being Al and inevitable impurities) was melted by a semi-continuous casting method by a conventional method, and the resulting aluminum alloy ingot was subjected to a temperature of 490 ° C. and a holding time of 4 A time homogenization process was performed. Thereafter, a 4.0 mm aluminum alloy hot-rolled sheet was produced by hot rolling, and intermediate annealing was performed under the conditions described below in a state where the aluminum alloy hot-rolled sheet had a sheet thickness of 0.7 mm by cold rolling. Further, after thinning to a certain extent by cold rolling, two materials were stacked, and finish rolling, which is a partial process of cold rolling, was performed to obtain a foil having a thickness of 40 μm. Then, the final annealing was performed on the conditions mentioned later, and the soft foil was produced.

For intermediate annealing, except for Comparative Example 8, in the continuous annealing line (CAL), the heating rate was 40 ° C./second, the heating temperature was 520 ° C., the holding time was 1 second, and the cooling rate was 40 ° C./second. In Comparative Example 8, batch annealing (BACH) was performed at 360 ° C. for 3 hours. Further, in Comparative Example 9, intermediate annealing was not performed (“NON” in Table 1). In the case where the intermediate annealing is performed by batch annealing, the crystal grains become extremely coarse when the high-temperature final annealing is performed, so that the conditions are relatively low.
In the final annealing, except for Comparative Example 8, batch annealing was performed at 350 ° C. for 5 hours, and in Comparative Example 8, batch annealing was performed at 300 ° C. for 5 hours to obtain a test material.

  Tensile tests were performed on the specimens to evaluate the elongation. The tensile test is based on JIS Z2241, and the rolling direction of the foil is set to 0 °, and JIS No. 5 test pieces in three directions of 0 °, 45 °, and 90 ° are sampled from the sample, and a universal tensile tester (manufactured by Shimadzu Corporation) is used. The test was conducted at a pulling speed of 2 mm / s.

  The average crystal grain size and the maximum crystal grain size were measured as follows. The aluminum alloy foil of the sample was electropolished with a 20% perchloric acid + 80% ethanol mixed solution, and then the observation magnification was set to × 500 with SEM (scanning electron microscope), and by EBSD (Effect Back Scatter Diffraction) analysis. An orientation mapping image was obtained, and the grain size distribution of the crystal grains was analyzed therefrom. The average grain size is calculated by dividing the measurement area by the number of grains within the measurement range, obtaining the area per grain, and assuming that the shape of the grain is a circle. The radius was calculated, and the average crystal grain size was determined from the value. In addition, three visual fields were observed for one sample, and the average crystal grain size was the average of three visual fields, and the maximum crystal grain size was the largest of the three visual fields.

As is clear from Table 1, Example No. 1-4 are comparative example No.1. Compared with 5-10, the anisotropy of elongation is reduced and it has high elongation in each direction.

Claims (5)

  In mass%, Fe: 1.4% or more and 2.0% or less, Si: 0.15% or less, the balance is composed of Al and inevitable impurities, and the average crystal grain size is 5 μm or less An aluminum alloy soft foil, wherein the maximum crystal grain size / average crystal grain size ratio is 3.5 or less.   2. The aluminum alloy soft foil according to claim 1, wherein an elongation in each direction of 0, 45, 90 ° with respect to the rolling direction at a thickness of 40 μm is 20% or more.   Cold rolling an aluminum alloy having a composition of Fe: 1.4% or more and 2.0% or less, Si: 0.15% or less, with the balance consisting of Al and inevitable impurities, and cold The manufacturing method of the aluminum alloy soft foil characterized by performing intermediate annealing by continuous annealing in the middle of rolling.   The intermediate annealing is performed at a temperature rising rate: 10 to 250 ° C./second, a heating temperature: 400 ° C. to 550 ° C., no holding time or holding time: 5 seconds or less, and a cooling rate: 20 to 200 ° C./second. The method for producing an aluminum alloy soft foil according to claim 3. The method for producing an aluminum alloy soft foil according to claim 3 or 4, wherein after the aluminum alloy is melted, a homogenization treatment is performed by heating at a temperature of 430 to 530 ° C for 3 to 7 hours.