JPH06101004A - Manufacture of aluminum foil excellent in strength and foil rollability - Google Patents

Abstract

PURPOSE:To provide a manufacturing method of alminum foil stock which is high in the strength and excellent in providing the aluminum foil with few pin holes. CONSTITUTION:Molten aluminum alloy having a composition consisting of, by weigh, >0.8% and <=2.8% Fe and 0.05-0.3% Si, and the balance A1 with inevitable impurities is continuously cast and rolled directly to make strip-shaped cast plate of <=25mm thickness. After >=30% cold rolling is executed, thereto heat treatment at >=400 deg.C, cold rolling and an intermediate annealing at 250-450 deg.C are executed in order, and again cold rolling is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an aluminum foil, and more particularly to a method for manufacturing an aluminum foil suitable for obtaining an aluminum foil having high strength and few pinholes. .

[0002]

2. Description of the Related Art Aluminum foil has a plate thickness of about 5 to 200 μm and is mainly used for packaging foods, medicines and the like. This aluminum foil is often used by being laminated with polyethylene, vinyl, paper, resin or the like. The aluminum foil used for such an application needs to be shielded from moisture and ultraviolet rays in the atmosphere depending on the packaged contents. Conventionally,
JIS-IN30 is used for aluminum foil for such applications.
(99.3% Al), JIS-1050 (99.5% A)
1), pure aluminum such as JIS-1100 (Al-0.13% Cu) is mainly used. This aluminum foil was cast into an ingot from a molten aluminum by a semi-continuous casting method, and was hot-rolled and cold-rolled to give an ingot.
A plate material (foil material) having a thickness of about 3 to 0.6 mm, and further foil rolling to a thickness of about 5 to 200 μm by foil rolling,
Further, it is general to perform annealing treatment. If necessary, the ingot is usually homogenized before hot rolling or subjected to intermediate annealing during cold rolling.

[0003]

By the way, recently, thinner aluminum foil has been required, and it has an extremely thin thickness of 6 μm or less, which is thinner than 7 μm which has been generally put into practical use. Things are becoming required. Generally, when rolling to a thin foil having a thickness of 10 μm or less, it is usual to carry out polymerization rolling (rolling two foils in layers), but in this polymerization rolling, the thinner the foil thickness, the more exponentially generated in the foil. Since the number of pinholes increases and the strength is insufficient, there is a problem that the foil breaks due to the tension during rolling, and the moisture permeation resistance of the foil remarkably decreases due to the increase in the number of pinholes. Therefore, when an extremely thin aluminum foil with a thickness of 6 μm or less is to be manufactured by a conventional general method, a sharp increase in the number of pinholes and a lack of strength cause frequent breakage accidents during foil rolling, resulting in high productivity. The fact is that only a foil with poor moisture permeability was obtained as the final foil. Therefore, there is a strong demand for the development of an aluminum foil material that has few pinholes even if it is rolled to a thickness of 6 μm or less and is excellent in strength and foil rollability.

[0004]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventors have found that aluminum produced by a continuous continuous casting and rolling method from an aluminum alloy melt whose Fe and Si contents are appropriately adjusted. Completed the present invention by discovering that the foil fabric produced by the steps of cold rolling, intermediate annealing, and cold rolling after the cold rolling of the alloy strip cast plate is further excellent, and the heat treatment is further excellent. It has come to do.

That is, according to the present invention, an aluminum alloy melt containing Fe in excess of 0.8% and 2.8% or less, Si in an amount of 0.05 to 0.3%, and the balance being Al and inevitable impurities is continuously formed. By directly casting and rolling to form a strip-shaped cast plate having a plate thickness of 25 mm or less, which is cold-rolled by 30% or more, and then heat-treated at a temperature of 400 ° C. or more, and then cold-rolled. The method for producing an aluminum foil having excellent strength and foil rollability is characterized by performing intermediate annealing at 250 to 450 ° C. and then performing cold rolling.

[0006]

Next, the present invention will be described in detail. In order to reduce the occurrence of pinholes in an ultrathin aluminum alloy foil, it is important to suppress roll hardening during foil rolling. When rolling hardening occurs, the crystal lattice deformation becomes nonuniform, and especially during polymerization rolling, a coarse banding occurs, so that the deformation of the polymerization surface becomes uneven and the roughness becomes large, and pinholes easily occur. Become. In the aluminum alloy foil according to the present invention, Fe added as an essential alloying component is finely crystallized as an Al—Fe-based intermetallic compound during continuous casting and rolling, and is crushed by the subsequent hot rolling and cold rolling. It is uniformly dispersed as fine particles having a diameter of 2 to 5 μm. Dislocations locally accumulate around the Al-Fe-based intermetallic compound dispersed in this way during foil rolling, and dynamic recovery occurs using this as a driving force, so that the effect of suppressing the progress of rolling hardening is exerted. is there. In order to obtain this effect, the amount of addition of Fe exceeds 0.8%, preferably 1.0%
It is necessary to be above. On the other hand, if the amount of addition of Fe exceeds 2.8%, the crystallized substances become coarse during solidification by casting, which rather easily causes pinholes and lowers the corrosion resistance. Therefore, the added amount of Fe exceeds 0.8% and 2.
The range is 8% or less.

Si has the effect of improving strength by coexisting with Fe. To obtain this effect, the amount of Si added is 0.
It must be at least 05%. On the other hand, the amount of Si added is 0.3
%, The amount of solid solution Si increases, causing hardening in the foil rolling step and increasing pinholes. Therefore, Si is added in the range of 0.05 to 0.3%.

[0008] Other impurities include Cu, Mn, Mg, Zn, etc. contained in ordinary aluminum ingots, but if these are about 0.05% or less, there is no particular problem. In addition, as an optional additional element, each containing 0.1% or less of Ti and B is effective for refining the solidification structure during continuous casting and rolling.

In the method of the present invention, the aluminum alloy melt having the above composition range is continuously cast and rolled to directly obtain a plate thickness of 25 mm.
The following band-shaped cast plate is used. The plate thickness of 25 mm or less of the strip-shaped cast plate obtained by the above continuous casting and rolling means that the intermetallic compounds formed during solidification of alloying component elements such as Fe and Si are sufficiently dispersed, and the effect of the continuous casting and rolling is achieved. It is a plate thickness that is sufficiently utilized, that is, a plate thickness that is obtained in a cast state in which the molten metal is cooled uniformly and rapidly. If the thickness of the strip-shaped cast plate exceeds 25 mm, the rapid solidification cannot be completed, and the intermetallic compound becomes coarse. Therefore, the thinner the plate thickness, the better.
If the thickness is less than mm, casting becomes difficult and the fine dispersion effect of the intermetallic compound is saturated, so it is not preferable to set the thickness to less than 3 mm, preferably continuous casting having a thickness of 5 to 10 mm. It is preferable to form a rolled plate. In order to continuously cast and roll the molten aluminum alloy, the molten metal in the above-mentioned mold is passed through a nozzle which is arranged between two casting rolls which face each other and a casting belt which runs. And then cooled in a mold to solidify. This method is known as a direct continuous casting and rolling method, and 3C method, Hunter method, Hazel method and the like are industrially used, but the present invention is not limited to these methods.

Next, in the method of the present invention, the strip-shaped cast plate obtained by continuous casting and rolling is cold-rolled by 30% or more and then heat-treated at a temperature of 400 ° C. or more. The cold rolling before the heat treatment has the effect of promoting the destructive action of the solidified structure during the heat treatment performed thereafter. When the cold rolling ratio is less than 30%, the cast structure is not sufficiently destroyed, so that a streak pattern is likely to occur on the mating surface (mat surface) of the polymer-rolled foil, which causes a problem in appearance. . Therefore, the cold rolling rate before heat treatment needs to be 30% or more. The heat treatment subsequent to the cold rolling has an effect of dividing the crystallized substance and finely dispersing it and an effect of breaking the solidified structure to form a homogeneous structure.
Further, this heat treatment is carried out by supersaturating solid solution of F during casting and rolling.
It has the effects of reducing the amount of impurity elements such as e and Si to improve the foil rollability, and lowering the recrystallization temperature during the intermediate annealing performed in a later step, thereby making the recrystallized grain size fine and uniform.
If this heat treatment is less than 400 ° C., the effect is not sufficient, the recrystallized grain size during intermediate annealing becomes coarse, and the foil rollability decreases. Therefore, it is preferable to perform heat treatment at a temperature of 400 ° C. or higher, more preferably 450 or higher for 0.5 hours or longer.

Next, in the method of the present invention, after cold working, intermediate annealing is performed at 250 to 450 ° C. The intermediate annealing is
It is performed in order to soften the plate material and obtain better rollability. If the cold working ratio before intermediate annealing is low, the driving force for recrystallization is insufficient, the recrystallized grain size during intermediate annealing becomes coarse, foil rollability decreases, and pinholes increase. The cold working rate is preferably 30% or more. If the intermediate annealing temperature is less than 250 ° C, the softening of the plate material is not sufficient and the rolling property is deteriorated. Since the amount of elements increases, foil rollability decreases and pinholes increase. Therefore, the intermediate annealing is performed in the range of 250 to 450 ° C, more preferably 280 to
It is better to carry out at a temperature of 420 ° C. for 0.5 to 8 hours. Further, in order to adjust the tempered state of the final foil, cold rolling and intermediate annealing may be repeated twice or more under the above intermediate annealing conditions.

Further, in continuous casting and rolling, surface defects such as oxides are easily generated on the surface of the strip-shaped cast plate, which may cause pinholes. It is effective to remove these surface defects by subjecting the surface cleaning treatment to the alkaline solution having a pH of 10 or more for 1 to 300 seconds at least once during the foil manufacturing process.

[0013]

The present invention will be described in more detail based on the following examples. The molten aluminum alloys A to F having the alloy compositions shown in Table 1 were continuously cast and rolled into a strip-shaped cast plate having a thickness of 7 mm. Further, as a conventional example, a semi-continuous cast ingot having a thickness of 500 mm was chamfered and homogenized by a usual method and then hot-rolled to a thickness of 7 mm. These are cold-rolled under the conditions shown in Table 2, heat-treated, further cold-rolled, annealed to an intermediate thickness of 0.7 mm, and further cold-rolled to 0.35 mm thick. It was made of foil. 12 of these foils
The foil was rolled in four passes to a thickness of μm, and finally polymerized to obtain a foil having a thickness of 5 μm. With respect to this foil, the number of pinholes was measured, the stripe pattern on the foil-polymerized surface was observed, and the tensile strength after 4 passes was measured. These results are also shown in Table 2.

[0014]

[Table 1]

[0015]

[Table 2]

As is apparent from Table 2, the foil according to the present invention
No. In Nos. 1 to 4, the number of pinholes was as small as 50 / m ² or less and the strength was excellent. Comparative example No. whose alloy composition is different from that of the present invention. No. 5 has low strength, and No. 5 is the same. No. 6 has many pinholes. Comparative example No. with low cold workability before heat treatment
7, No. No. 9 has a streak pattern on the foil superposed surface,
Comparative example with low heat treatment temperature or no heat treatment
No. 8, No. No. 10 also has a streak pattern. Comparative example No. in which heat treatment conditions or intermediate annealing conditions differ from those of the present invention.
In Nos. 7 to 11, although the foil strength was high, many pinholes were generated. Conventional example No. manufactured from a semi-continuous casting ingot without using the continuous casting and rolling method. No. 12 has no streak pattern and few pinholes, but the strength is low.

[0017]

As described in detail above, according to the present invention,
It is possible to provide an aluminum foil material which is excellent in foil strength and foil rollability and has few pinholes, and which has a remarkable industrial effect.

Claims (1)

[Claims] 1. Fe content exceeding 0.8% by weight and 2.8% by weight
Hereinafter (hereinafter, weight% is abbreviated as%), Si is 0.05 to
The aluminum alloy melt containing 0.3% and the balance Al and unavoidable impurities is continuously cast and rolled to directly form a strip-shaped cast plate having a thickness of 25 mm or less, and cold-rolled by 30% or more. After performing heat treatment at a temperature of 400 ° C. or higher after performing the above, cold rolling is performed, intermediate annealing is performed at 250 to 450 ° C., and then cold rolling is performed, which is excellent in strength and foil rollability. Method for manufacturing aluminum foil.