JP2002038233A - Material for aluminum alloy foil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a material for an aluminum alloy foil whereby an aluminum alloy foil excellent in a pin hole property and a foil break resistance, high in a softening strength of product and therefore kept in quality, can be obtained even if process annealing is omitted for cost down. SOLUTION: This material for aluminum alloy foil as foil rolling, is composed of aluminum alloy having Fe of 0.70-1.70 mass % and Si of 0.03-0.30 mass %, wherein the occupied ratio of area of sub-grain structure in cell structure is 50-90% without process annealing in the course of process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy foil used as a material for aluminum alloy foil used for packaging medicines, foods and the like.

[0002]

2. Description of the Related Art Aluminum alloy foils are generally used in a thickness of about 5 to 100 μm depending on the application.
These aluminum alloy foils are also used for packaging, and have been conventionally used in JIS 1N30 (JIS H4160).
Have been mainly used. In recent years, JIS 8079, 8021, and the like, which have higher strength and higher rollability than JIS 1N30 and have a high Fe amount, have been used in response to a demand for further reduction in foil thickness.

[0003] Aluminum alloy foils used for packaging foods and chemicals are generally used in a state of being bonded to polyethylene, vinyl, paper or the like. The foil used for such an application has a function of protecting its contents from atmospheric moisture and ultraviolet rays, and is required to be excellent in quality.

[0004] Aluminum alloy foil is generally manufactured by preparing an aluminum alloy slab by a method such as semi-continuous casting, and performing a soaking process, a hot rolling process, a cold rolling process, an intermediate annealing process, and a cold rolling process. The thickness is set to 0.15 mm to 0.3 mm. The aluminum alloy foil is further rolled to a thickness of 5 to 100 μm. This rolling is called foil rolling. After the foil rolling, the foil is annealed at a temperature of 250 ° C. or more, and the rolling oil remaining in the coil during the foil rolling is evaporated to form an aluminum alloy foil. This annealing turns the aluminum alloy foil into a soft material.

[0005] In recent years, cost reduction has been increasingly demanded for aluminum alloy foils. One of the methods is to omit the intermediate annealing step after the cold rolling. By omitting the intermediate annealing step, not only is the energy required for annealing and equipment such as an annealing furnace unnecessary, but also the number of production days can be shortened, and the effect is large. However, simply eliminating the intermediate annealing in the conventional process not only deteriorates the foil quality such as the strength and pinhole characteristics of the aluminum alloy foil, but also causes the foil to break due to work hardening or the like, making production impossible. Therefore, it is necessary that the pinhole characteristics, the foil breaking resistance, and the soft foil strength of the product described below are excellent.

[0006] Pinholes are tiny holes present in a thin foil and are generated by overlap rolling in the final pass. Pinholes tend to increase exponentially with decreasing product foil thickness. Since aluminum foil having a large number of pinholes significantly deteriorates in moisture resistance when it becomes a product, pinholes are strictly regulated. Accordingly, it is necessary that pinholes are not easily generated even when the aluminum alloy foil is rolled, that is, the pinhole characteristics must be excellent.

[0007] Foil breakage (foil breakage) generated during foil rolling not only deteriorates product yield, but also takes time and labor to clean up after foil breakage, which is a cause of deterioration in productivity. Foil rupture occurs when the rolling load or tension is too high, or when excessive work hardening or softening occurs before and after rolling, and the material strength before and after rolling changes. Therefore, in order to improve productivity, it is necessary that the foil break resistance is excellent.

In addition, foil products are sold on a length basis, with thinner foil thicknesses being more cost effective within tolerances for nominal thickness. However, simply reducing the thickness of the current product is insufficient in strength and causes problems such as breakage of the foil and generation of wrinkles. In order to compensate for the insufficient strength due to the reduction in foil thickness, it is necessary to improve the strength of the product soft foil.

There are various types of aluminum foils having different thicknesses and configurations depending on the application, and the following are conventionally known.

First, Japanese Patent Application Laid-Open No. 57-123966 discloses an aluminum alloy containing 0.1 to 0.5% by mass of Fe and having low work hardening (conventional example 1). The technology described in this publication is to produce an ingot by semi-continuous casting, then perform hot rolling, and without intermediate annealing, after cold rolling to a sheet thickness of 0.12 mm, heat treatment annealing. I am giving.

Further, Japanese Patent Application Laid-Open No. 62-250143 discloses that an aluminum alloy ingot is subjected to homogenization treatment, hot rolling,
An aluminum foil in which the Fe and Mn contents of the aluminum alloy foil formed by sequentially performing cold rolling, foil rolling and final annealing and the crystal grain size after final annealing are controlled is disclosed. Also, Japanese Patent Application Laid-Open No. 62-250144 discloses Fe, Mn of aluminum alloy foil formed through the same process.
And a foil in which the Si content and the crystal grain size after the final annealing are controlled are disclosed (Conventional Example 2). According to Conventional Example 2,
By controlling the aluminum alloy composition and the crystal grain size, the springback after forming the aluminum alloy foil is reduced.

Further, Japanese Patent Application Laid-Open No. 4-214833 discloses an aluminum foil in which the Fe content, the area ratio of sub-grains in the foil and the particle size are regulated (Conventional Example 3). According to the technique of the conventional example 3, in the foil rolling of an aluminum alloy, the cell walls can be moved under appropriate rolling conditions to form sub-grains relatively stable against rapid heating, thereby causing the generation of gleng loss. Has been prevented.
Further, when the rolling conditions are not appropriate and sub-grains are not formed, heat treatment is performed before baking to adjust the grain size and area ratio of the sub-grains.

Furthermore, Japanese Patent Application Laid-Open No. 11-217656 discloses a foil in which the contents of Fe and Si are regulated, the hot-rolled sheet is reduced to 3 mm or less, and the final temperature of the cold rolling is regulated to 100 to 180 ° C. A ground manufacturing technique is disclosed (conventional example 4). In the technique described in Conventional Example 4, by increasing the final temperature of cold rolling to 100 to 180 ° C., intermediate annealing in the cold rolling step can be omitted.

[0014]

However, the technique of the prior art 1 is mainly intended for ironing of fins and cans, and is not intended for thin foils. In addition, the aluminum alloy foil of the conventional example 2 is intended for a foil used for a cap seal or the like of a beverage can and is intended to reduce springback, and is also intended for a foil material for a thin foil. Absent.

The third conventional example is aimed at preventing gleng loss at the time of baking coating. As described above, it is possible to obtain sufficient pinhole characteristics, foil breakage resistance and product soft strength. Can not.

Further, in the technique of the conventional example 4, it is possible to increase the load of the cold rolling equipment for increasing the final temperature of the cold rolling to 100 to 180 ° C., and to uniformly control the lubrication conditions and the like. It is difficult, and there is a problem that quality variation between products becomes large.

None of the conventional examples described above satisfy the foil strength, pinhole characteristics, and foil breakability. Further, in recent years, the quality requirements for the foil base quality have been increasing, and particularly for thin foils, while the reduction in foil thickness has been strongly demanded, the demand for cost reduction is severe.

The present invention has been made in view of such a problem, and even if the intermediate annealing is omitted for cost reduction, the pinhole characteristics and the foil breaking resistance are excellent, the product soft strength is high and the quality is high. It is an object of the present invention to provide an aluminum alloy foil base from which a maintained aluminum alloy foil can be obtained.

[0019]

The aluminum alloy foil material according to the present invention is an aluminum alloy foil material for foil rolling, and contains 0.70 to 1.70% by mass of Fe and 0. 70% by mass of Si.
It is made of an aluminum alloy containing 0.3 to 0.30% by mass, wherein the intermediate annealing is not performed in the middle step, and the area occupancy of the subgrain structure in the cell structure is 50 to 90%.

In the present invention, the aluminum alloy may further contain 0.005 to 0.03% by mass of Cu.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The inventors of the present application have conducted intensive experiments and researches to solve the above-mentioned problems. As a result, the Fe content of the aluminum alloy was set to 0.07 to 1.70 mass% and the Si content was set to 0.0
At the stage of aluminum alloy foil for foil rolling to make the aluminum alloy foil 3 to 0.30 mass% and 50 to 90% of the entire cell structure of the aluminum alloy foil as a sub-grain structure. Thus, it was found that a sub-grain structure was stably maintained in each step of foil rolling, and an aluminum alloy foil having excellent pinhole characteristics, foil rupture resistance, and product soft foil strength could be obtained.

The reasons for limiting the numerical value of the area occupancy of the subgrain structure specified in the present invention, the reasons for adding the aluminum alloy additive, and the reasons for limiting the numerical value will be described below.

The area occupancy of the subgrain structure is 50 to
In general, when aluminum and aluminum alloys are processed from a soft state, dislocations are introduced into the material and change into a tangle-like dislocation structure, a cell-like dislocation structure, and the like. Strength increases. Further, in a high-purity aluminum or an aluminum alloy containing a specific amount of Fe, Ni, or the like, when the processing rate is increased, so-called polygonalization in which dislocations are rearranged occurs, and the entangled dislocations form walls to form a subgrain structure. Easy to do.

In the foil rolling step of rolling the thin foil, the material state in the final pass is desirably softened to some extent. For example, annealing is performed at 170 ° C. for about 2 hours, and then the final pass is performed. To obtain an aluminum alloy foil having a thickness of 7 μm. That is,
The material structure is a tangle-like or cell-like dislocation structure in the first pass of foil rolling, but a subgrain structure was obtained just before the final pass by the above-described annealing. In recent years, from the viewpoint of cost reduction and the like, in order to perform the final pass rolling without annealing as described above, the final pass is performed by combining the components of the aluminum alloy, the cold working rate during the production of the aluminum alloy foil, and the foil rolling conditions. Earlier, it was aimed to obtain a material state that would result in a subgrain structure.

In contrast to these prior arts, the present inventors completely changed the viewpoint, and made a sub-grain structure already at the stage of the foil base, and strictly controlled the aluminum alloy components and the production conditions, thereby enabling each pass of the foil rolling. In the above, a foil material capable of stably maintaining a subgrain structure was found.

If the area occupation ratio of the sub-grain structure in the aluminum alloy foil is less than 50%, the 1
Alternatively, in the second pass, the hardening rate is remarkable and the absolute value of the strength is high, so that the rolling becomes rather difficult, and the foil is easily broken. On the other hand, if the area occupation ratio of the sub-grain structure in the aluminum alloy foil layer exceeds 90%, remarkable softening occurs during the pass of foil rolling, and the subsequent pass shows a remarkably hardening rate, resulting in excessive foil breakage and pinholes. Would. Therefore, the area occupancy of the subgrain structure in the aluminum foil is set to 50 to 90%.

The area occupancy of the subgrain structure in the present invention can be measured as follows. First, a transmission electron microscope (Transmission electron microscope)
(TEM)) A thin film for observation was prepared, and TEM observation was performed at a magnification of, for example, 10,000 times for a portion having a thickness of 2000 to 2500 °. In the observed cell structure, (1) no dislocation was observed in the grains. In addition, in the case where no interference fringes are observed at the grain boundaries and the arrangement of dislocations at the grain boundaries cannot be said to be complete, the grains in which no dislocations are observed in the grains are subdivided. Grain organization. The area ratio of these sub-grain tissue portions can be measured by an image analyzer. The TEM observation is preferably performed at a magnification of 5000 times or more and 20000 times or less, depending on the particle diameter of the subgrain. When the magnification is lower than 5000 times, observation of dislocations and interference fringes in the sub-grains becomes insufficient, and an accurate area ratio cannot be obtained. The higher the magnification is, the easier it is to obtain the area ratio accurately, but it is useless even if the magnification exceeds 20000 times.

Fe content: 0.7 to 1.7% by mass Fe is added to the aluminum alloy to improve the strength of the aluminum alloy and to cause work hardening.
Further, the aluminum alloy is sub-grain-structured. However, if the Fe content is less than 0.7%, absolute strength cannot be obtained, and a sub-grain structure cannot be obtained during strong working. On the other hand, when Fe exceeds 1.7%, remarkable softening at the time of strong working and a remarkable hardening rate in a subsequent pass lead to foil breakage and the like. Further, Fe binds to Al to form an intermetallic compound, but if added in excess of 1.7%, foil breakage is likely to occur due to the notch effect caused by this compound. Therefore, the Fe content is 0.7 to 1.7.
% By mass.

Si content: 0.03 to 0.3% by mass Si easily forms a compound together with Fe. If the content of Si is less than 0.03% by mass, ingot casting of the aluminum alloy becomes difficult due to molten metal leakage during casting. On the other hand, when the Si content exceeds 0.3% by mass, the solid solution state and the precipitation state of Fe are likely to be unstable, the strength and work hardening behavior of the foil become unstable, and the strength of the product foil is reduced. For this reason, Si
The content is set to 0.03 to 0.3% by mass.

Cu content: 0.005 to 0.03 mass
Depending on the % foil rolling conditions, solid-solution Si and solid-solution Fe alone cause excessive subgraining, and the above-described remarkable softening and remarkable hardening are likely to occur. To prevent this, 0.
It is preferable to add 005% by mass or more of Cu. However, if added in excess of 0.03% by mass, the formation of subgrains does not proceed and the desired effect cannot be obtained, leading to foil breakage and the like. Therefore, the Cu content is preferably set to 0.005 to 0.03% by mass.

Although Ti is not directly related to the effect of controlling the work hardening behavior of the present invention, it is effective for refining the ingot structure, and for this purpose, 0.005% to 0%. It is preferable to add 0.03% by mass.

In addition, unavoidable impurities such as Mn, Mg, Zn, and Cr are allowable if they are less than 0.05% by mass, because they do not affect the effects of the present invention.

Next, the method for producing the aluminum alloy foil of the present invention will be described. As described above, the aluminum alloy foil fabric produces a slab of an aluminum alloy having a specified Fe and Si content by semi-continuous casting, soaking treatment,
It can be manufactured by hot rolling and cold rolling. At this time, the intermediate annealing usually performed after the cold rolling is not performed. Further, the soaking conditions are, for example, 480 to 540.
C. for 3 to 6 hours, and the cold rolling rate is, for example, 90 to 96.
%. As described above, when the soaking treatment and the cold rolling are performed under appropriate conditions, the area occupancy of the subgrain structure in the cell structure of the obtained aluminum alloy foil material is reduced to 50 to 90.
%.

The intermediate annealing step can be omitted by appropriately regulating the aluminum alloy composition and performing soaking, hot rolling and cold rolling under appropriate conditions. As a result, the obtained aluminum foil material has an area occupation ratio of the subgrain structure of 50 to 90%. Therefore, even if foil rolling is performed thereafter, the aluminum foil material has excellent pinhole characteristics and foil rupture resistance. In addition, a foil-rolled aluminum foil has sufficient product soft strength. Therefore, in the manufacturing process of the aluminum foil material, the intermediate annealing can be omitted to obtain an aluminum foil material having extremely low cost and high productivity.

[0035]

EXAMPLES The aluminum alloy foil of the present invention is actually manufactured and compared with a comparative example which is out of the scope of the present invention, and its effect will be described.

First, a test foil was produced by semi-continuous casting of a 500 mm thick slab made of an aluminum alloy having the composition shown in Table 1 below. Cold rolling was performed. In all the examples and comparative examples, no intermediate annealing was performed. The thickness of all the obtained aluminum alloy foils was unified to 0.2 mm, which was used as a test foil.

The area occupancy of the subgrain structure of the test foil ground in the cell structure is determined by the aluminum alloy component, the soaking condition,
And the cold rolling reduction.

Next, the area occupancy of the subgrain structure in the obtained test foil was measured. As described above, a thin film for TEM observation was prepared, and TEM observation was performed at a magnification of 10,000 times for a portion having a thickness of 2000 to 2500 ° to observe a sub-grain structure in the cell structure. FIG. 1 and FIG. 2 are TEM photographs showing sub-grain structures in some test foil bases. As shown in FIG. 1, (1) grains in which no dislocations are observed in grains and interference fringes are observed in grain boundaries, (2) cases in which no interference fringes are observed in grain boundaries, and rearrangement of grain boundaries. In the case of not being perfect, a grain in which no dislocation was observed in the grain was determined as a sub-grain structure.

FIGS. 3 and 4 are trace diagrams in which the portions determined to be the subgrain tissues 1 in the examples shown in FIGS. 1 and 2, respectively, are blacked out. Thus, the area occupancy of the sub-grain tissue (sub-grain ratio) was measured by the image analyzer from the trace diagram of the sub-grain tissue determined from the TEM photograph. The area occupancy rate is obtained by measuring a plurality of arbitrarily selected locations and averaging them.

Table 1 below shows the area occupancy of the subgrain structure of each test foil ground measured as described above. In addition, the cold rolling rate was calculated by (sheet thickness before cold rolling-sheet thickness after cold rolling) / sheet thickness before cold rolling. The cold rolling reduction was adjusted by changing the sheet thickness after hot rolling.

The obtained test foil ground was subjected to a 4-pass foil rolling test using an actual foil rolling machine. In the final pass, a foil having a thickness of 15 μm was used, and doubling rolling was performed to produce an aluminum alloy foil having a glossy surface and a glossy surface on one side and a foil thickness of 6.5 μm.

Further, after the foil rolling, the obtained aluminum alloy foil was subjected to softening annealing at 300 ° C. for 20 hours.
A soft foil was used. Thereafter, for each test foil base, the pinhole characteristics during foil rolling, the productivity of the foil (breakage rate during foil rolling), and the strength of the obtained soft foil were evaluated.

The pinhole characteristics were evaluated by counting the number of pinholes in the manufactured foil using a light irradiation type pinhole detector. When the number of pinholes was less than 100 / m ^{2, it was} evaluated as ○, and when it was 100 or more / m ² , it was evaluated as ×.

The productivity was evaluated by dividing the number of foil breaks that occurred during foil rolling by the product tonnage. If the number of foil breaks is less than 1.0 times / ton, ○;
And

The evaluation of the foil strength was performed by using a tensile tester.
The evaluation was based on the tensile strength of the soft foil. Tensile strength 70N /
mm ² or more was evaluated as ○, and tensile strength as less than 70 N / mm ² was evaluated as ×. Table 2 shows the evaluation results of the pinhole characteristics, productivity, and foil strength.

[0046]

[Table 1]

[0047]

[Table 2]

In Examples 1 to 8, since the composition of the aluminum alloy and the area occupancy of the subgrain structure were within the range of the present invention, the pinhole characteristics after foil rolling, the foil breaking, and the soft strength were good.

In Comparative Example 1, the area occupancy of the subgrain in the aluminum foil was less than the lower limit of the range of the present invention.
Many pinholes were generated, and the pinhole characteristics deteriorated.
In Comparative Example 2, since the Si content exceeded the upper limit of the range of the present invention, the work hardening behavior became unstable, and the foil strength decreased.
In Comparative Example 3, since the Fe content exceeded the upper limit of the range of the present invention, the heat generation during the foil rolling significantly promoted the subgrain organization and caused excessive work softening. did. In Comparative Example 4, since the Fe content was less than the lower limit of the range of the present invention, the soft foil strength was low. In Comparative Example 5, since the Cu content exceeded the upper limit of the preferred range of the present invention, and the area occupancy of the subgrain structure was less than the lower limit of the present invention range, excessive work hardening occurred and foil breakage frequently occurred. In Comparative Example 6, since the area occupation ratio of the sub-grain structure exceeded the upper limit of the range of the present invention, remarkable work softening occurred in an intermediate pass during foil rolling, and foil fracture frequently occurred.

[0050]

As described in detail above, according to the present invention,
A foil with productivity and quality equal to or higher than the current one can be produced using an inexpensive foil material.

[Brief description of the drawings]

1 (a) to 1 (c) are photographs substituted for drawings showing the surfaces of aluminum alloy foil substrates of Example 1, Example 3 and Example 6 respectively (TEM photograph: magnification 10000 times).

FIGS. 2A and 2B are Comparative Examples 1 and 2, respectively.
1 is a drawing-substituting photograph showing the surface of an aluminum alloy foil substrate of Example 1 (TEM photograph: 10000 times magnification).

FIGS. 3A to 3C are Embodiments 1 and 3, respectively.
FIG. 11 is a diagram in which a subgrain structure is traced in a TEM observation photograph of the aluminum alloy foil ground surface of Example 6 and FIG.

FIG. 4 is a TEM of the ground surface of the aluminum alloy foil of Comparative Example 1.
It is the figure which traced the subgrain organization in an observation photograph.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Nobuyuki Tanami 15 Kinuigaoka, Moka-shi, Tochigi Pref. Inside Kobe Steel Moka Works (72) Inventor Katsura Kajiwara 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo No. 5 Kobe Steel, Ltd.Kobe Research Institute (72) Inventor Yasuaki Sugisaki 1-5-5 Takatsukadai, Nishi-ku, Kobe City, Hyogo Prefecture Kobe Steel, Ltd.Kobe Research Institute

Claims (2)

[Claims] 1. An aluminum alloy foil for foil rolling, comprising 0.70 to 1.70% by mass of Fe and 0. 70% by mass of Si.
An aluminum alloy foil comprising an aluminum alloy containing 0.3 to 0.30 mass%, wherein intermediate annealing is not performed in an intermediate step, and an area occupancy of a subgrain structure in a cell structure is 50 to 90%. . 2. The aluminum alloy according to claim 1, wherein Cu: 0.0
The aluminum alloy foil material according to claim 1, wherein the aluminum alloy foil content is from 0.05 to 0.03% by mass.