JPS62250144A - Aluminum-alloy foil for package - Google Patents

Abstract

PURPOSE:To obtain an A-alloy foil for package having high bursting strength and reduced in spring back after forming, by specifying a composition consisting of Fe, Mn, Si, and Al. CONSTITUTION:The Al-alloy foil for package has a composition consisting of, by weight, 0.7-1.8% Fe, 0.1-1.5% Mn, 0.2-0.5% Si, and the balance Al with inevitable impurities. This Al-alloy foil has high bursting strength and is reduced in spring back after forming, so that thinning of foil is made possible and cost reduction can be attained. Moreover, it is desirable that average grain size of the above foil after final annealing is limited to range 15-60mum by changing various conditions in the manufacturing process.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to an aluminum alloy foil for packaging used as cap seals for food and beverage containers.

Prior art and problems Aluminum foil for this type of packaging has the following properties:
In particular, it is required to have high bursting strength and not break easily, and to have little elastic deformation (so-called springback) after solidification forming (punching) or drawing forming.

On the other hand, conventionally, such packaging aluminum foil has lN30
A soft foil (so-called 0 material) obtained by annealing a pure aluminum alloy such as an alloy was used. However, since such conventional foils have low springback but low bursting strength, the foil must necessarily be thick, on the order of 30 to 100 μm, leading to increased costs.

However, in recent years, aluminum foil itself has been made thinner to reduce costs, and aluminum laminate materials, which are aluminum foil laminated with synthetic resin films such as polyethylene, have been used as packaging materials to compensate for the decrease in strength due to the thinner aluminum foil. is also used. However, in such aluminum laminate materials, since the elastic modulus of the synthetic resin film is low, the springback after molding is generally large, resulting in a drawback that there is a risk of problems in processing in the next step.

The present invention was made in view of the above circumstances, and it is an object of the present invention to provide an aluminum alloy foil for packaging that has high bursting strength and low springback after forming.

Means for Solving the Problems For this purpose, the inventor conducted various experiments and research, and found that in order to improve bursting strength, it is necessary to increase tensile strength and elongation, and to reduce springback after molding. It was discovered that a lower yield strength (0.2% yield strength) is preferable for this purpose, and from this point of view, this was completed as a result of further research on the alloy composition.

That is, the aluminum alloy foil for packaging according to the present invention is made of Fe.
: 0.7~1.8vt%, Mn: 0°1~1.
5wt%, Si: 0. 2-0. 5 wt%, with the remainder consisting of aluminum and unavoidable impurities.

In the composition of aluminum alloy foil, Fe makes the crystal grains of the foil smaller and improves its strength and elongation. However, when θ is less than 7vt%, the effect is poor, and on the contrary 1.8ν
Even if it contains more than j96, Afi-F e-3i-
A coarse compound of Mn is formed, resulting in a decrease in strength, elongation, and foil rollability.

Preferably, the content of melon is in the range of 1.0 to 1.671%.

Mn reduces the amount of solid solution of Fe and becomes recrystallization nuclei ρ-
This increases the number of Fe-Mn compounds, promotes grain refinement of the foil, and contributes to improvement in strength due to fine precipitates and solid solution Mn. However, if it is less than 0.1 wt%, these effects are poor, and on the other hand, if it is added more than 1.5 wt%, coarse compounds are formed, work hardening increases, foil rollability decreases, and yield strength decreases. If the height is too high, the springback will be large. Preferably 0. The content is preferably in the range of 3 to 1°0vt96.

Si contributes to improving the strength of the foil.

However, if it is less than 0.2vt%, the effect is poor;
．． If the content exceeds 5 wt%, work hardening increases and foil rollability decreases, and yield strength becomes too high, resulting in large springback. Preferably 0. The content is preferably in the range of 2 to 0.35 wt%.

In addition to the above components, Ti: about 0.005 to 0.05 wt%, B
: Content of about 0.005 to 0.05 wt% is allowed.

By the way, in a generally known manufacturing method for aluminum alloy foil, each essential step of hot rolling, cold rolling, foil rolling, and final annealing is sequentially performed on an aluminum alloy ingot, but the aluminum alloy according to the present invention It is desirable that the foil has an average grain size after final annealing within a range of 15 to 60 μm. That is, the average crystal grain size is 15 μm
If it is less than that, the yield strength of the foil will become too high, and there is a risk that the springback after molding will become large. Also, the crystal grain size is 6
When the diameter exceeds 0 μm, not only the tensile strength and elongation decrease and the bursting strength decreases, but also the surface roughness becomes large after molding, which may cause problems in terms of appearance. More preferably, the thickness is 15 to 40 um.

The average grain size after final annealing is determined by various conditions in the known manufacturing process described above, such as hot rolling temperature, rolling ratio of cold rolling or foil rolling, final annealing temperature, time, temperature increase rate, etc. By changing it, you can make various changes,
It can also be changed by whether or not the slab is homogenized or by performing intermediate annealing after hot rolling, during cold rolling, or before foil rolling.

Effects of the Invention As is clear from the examples, the aluminum alloy foil having a specific composition according to the present invention has high bursting strength and less springback after forming.

Therefore, it is possible to make the foil thinner, which reduces costs, and also prevents problems from occurring during processing in the next step after molding, making it suitable as a packaging foil.

Example Next, this invention will be explained in detail.

Various aluminum alloy foils were manufactured by combining the AQ-F e-Mn-3i alloy having the composition shown in Table 1 with the manufacturing methods shown in (1) to (2) below.

■ After homogenizing the aluminum alloy slab at 610°C for 20 hours, it was heated to 530°C to a thickness of 4 mtn.
After hot rolling to 0,6 nun, foil rolling to a thickness of 25 μm, then 37
Final annealing at 0°C for 2 hours.

■ In the process of ■ above, after cold rolling and before foil rolling,
Intermediately annealed at 0°C for 1 hour.

■ In the step (■) above, first intermediate annealing is performed at 400°C for 1 hour after hot rolling, and then at 400°C after cold rolling.
×1 hour secondary intermediate annealing.

■ In the process of "Two feet■", the secondary intermediate annealing is carried out at 20℃/
The test was conducted at 400°C for 20 seconds at a rapid heating rate of sec.

And ・I- of the aluminum alloy foil obtained above
The uniform grain size was measured.

Table 1: Next, the bursting strength of two 6 foils was measured, and the springback after forming was measured by shallow rippling molding with a punch diameter of 33 tnm and a blank diameter of 49 tnta. The amount of springback was evaluated based on the difference between the maximum outer diameter of the molded product and the punch diameter after molding.

The results are shown in Table 2.

As is clear from the results in Table 2, the aluminum alloy foils according to the present invention have a bursting strength of 2.2. It was confirmed that the value exceeds oXy/m and that the springback after molding is small.

Claims (2)

[Claims] (1) Fe: 0.7-1.8wt%, Mn: 0.1-1
．． 5 wt%, Si: 0.2 to 0.5 wt%, and the remainder consists of aluminum and inevitable impurities. (2) The aluminum alloy foil for packaging according to claim 1, wherein the average crystal grain size after final annealing is defined in the range of 15 to 60 μm.