JP2002322530A - Aluminum foil for container and production method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide aluminum foil for a container which has high strength, elongation and satisfactory drawing formability, and a production method therefor. SOLUTION: The aluminum foil for a container has a composition containing, by weight, 0.10 to 0.8% Fe and 0.001 to 0.02% Ti, and the balance Al with inevitable impurities, and the content of Si in the inevitable impurities is <0.15%. The aluminum foil has a subgrain structure in which recrystallized grains are present in the central part of the foil thickness, and recrystallized grains are not present in the surface layer of the foil thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum foil for a container and a method for producing the same. An object of the present invention is to provide an aluminum foil for a container and a method for producing the same.

[0002]

2. Description of the Related Art Aluminum or aluminum alloys of 1000 series, 3000 series, 5000 series, etc., which are recrystallized structures, subgrain structures or mixed structures in which recrystallized grains are uniformly mixed in a subgrain structure, have low strength. Yes,
Because of its elongation, it is used as aluminum foil for packaging and the like, and because of its good drawability, it is used for various containers. For example, in the case of a wrinkled container for storing food, a foil having a thickness of 50 to 200 μm is drawn by a die and a punch, and the flange portion and the container wall are wrinkled.

The above-mentioned foil having a thickness of 50 to 200 μm is subjected to DC casting to obtain an ingot having a thickness of 400 to 550 mm, and the ingot is subjected to homogenization heat treatment, hot rolling, cold rolling, annealing treatment. Then, a thin plate having a predetermined thickness (1 to 3 mm) is cold-worked, tempered and annealed to a predetermined hardness, and then foil-rolled to produce a foil having a predetermined thickness.

[0004]

SUMMARY OF THE INVENTION
Aluminum alloys of type 0 are easy to process and are often used. However, thinning is required for cost reduction. However, when cured, there is a problem that elongation is reduced and drawability is particularly reduced. In addition, the production of foil by DC casting has the disadvantage that the thickness of the ingot is large and therefore many steps are required for subsequent rolling.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on solving the above-mentioned problems in the prior art, and as a result, have found that a foil having a sub-grain structure in which recrystallized grains are present only in the center of the foil thickness is provided. The present invention has been completed by finding that the strength is high, the elongation is good and the drawability is good, and the present invention has completed the present invention. The present invention has succeeded in providing a method for manufacturing the aluminum foil, which is easy to perform, as follows.

(1) Fe: 0.10 to 0.8 in wt%
%, Ti: 0.001 to 0.02%, and the balance consists of unavoidable impurities and Al.
Less than 0.15%, recrystallized grains are present in the center of the foil thickness,
An aluminum foil for a container, wherein the foil thickness surface layer has a sub-grain structure without recrystallized grains.

(2) The ratio of recrystallized grains existing at the center of the foil thickness is 1 to 30 in terms of area ratio in a cross section along the rolling direction.
%, The aluminum foil for a container according to the above (1).

(3) The aluminum foil for a container according to the above (1) or (2), wherein the size of the recrystallized grains existing at the center of the foil thickness is 5 to 50 μm.

(4) Any one of the above items (1) to (3), wherein the range of the layer thickness at the center of the foil thickness where recrystallized grains are present is 1/4 to 3/4 of the total foil thickness. An aluminum foil for a container according to any one of the above.

(5) A slab obtained by continuously casting a foil is subjected to cold rolling at a rolling reduction of 95% or more without intermediate annealing to obtain a foil having a desired thickness by continuous casting and rolling. The aluminum foil for containers according to any one of claims 1 to 4, which is obtained.

(6) Fe: 0.10 to 0.8 in wt%
%, Ti: 0.001 to 0.02%, and the balance consists of unavoidable impurities and Al.
Aluminum alloy continuous casting in which the slab obtained by continuous casting is less than 0.15% and is subjected to cold rolling at a rolling reduction of 95% or more without intermediate annealing to obtain a foil having a desired thickness. It is obtained by rolling, wherein recrystallized grains are present at the center of the foil thickness, and the layer thickness range of the center of the foil thickness where the recrystallized grains are present is 1/4 to 3/4 of the total foil thickness. An aluminum foil for a container, wherein the other foil-thick surface layer has a sub-grain structure without recrystallized grains.

(7) The aluminum foil for a container according to any one of the above (1) to (6), wherein the foil is a foil for a draw-formed container.

(8) Fe: 0.10 to 0.8 in wt%
%, Ti: 0.001 to 0.02%, and the balance consists of unavoidable impurities and Al.
Continuously casting an aluminum alloy melt of less than 0.15%, then performing cold rolling at a reduction of 95% or more, and then 2
A method for producing aluminum foil for a container, comprising performing temper annealing for 4 hours to 10 hours at a temperature of 50 to 300 ° C.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION An aluminum foil having a subgrain structure in which recrystallized grains are present only in the center portion of the foil thickness is a so-called composite structure foil, and the whole foil has a uniform subgrain structure or recrystallized structure. The strength and the elongation are balanced as compared with those of the above, and the drawability is excellent. In other words, regarding the drawability, if the entire plate has a uniform subgrain structure as in the prior art at the time of draw forming, the subgrain structure has good elongation, so that deformation is concentrated on the shoulder portion of the punch and cracks. A metal structure in which defects are liable to be present and recrystallized grains are also present on the foil surface is easier to work harden than a sub-grain structure. The surface of the crystal structure is likely to be rough, and is likely to exhibit cracking defects as a starting point of cracking.

On the other hand, with the composite structure as described above according to the present invention, concentration of deformation strain at the shoulder of the punch can be prevented, and good drawing can be performed. However, the foil of the composite structure of the present invention has a recrystallization ratio existing in the center of the foil thickness,
The cross-sectional area ratio is preferably from 1 to 30%, whereby the progress of the concentration of deformation on the foil surface at the shoulder of the punch at the time of drawing is accurately prevented. That is, 1
%, It is difficult to prevent cracks at the shoulder of the punch.
%, The work hardening increases during drawing,
There is a possibility that it may be a starting point of cracking during deformation.

In the composite structure foil of the present invention as described above, the size of the recrystallized grains at the center of the foil is set to 5 to 50 μm, whereby the concentration of deformation strain at the punch shoulder during drawing is appropriately prevented. That is, when the size of the recrystallized grains is less than 5 μm or the proportion of the recrystallized grains at the center of the foil thickness is less than 1%, it may not be possible to completely prevent the occurrence of cracks at the punch shoulder, Further, when the recrystallized grain ratio exceeding 50 μm exceeds 30%, there is a possibility that it becomes a starting point of a crack at the time of drawing.

In the composite texture foil according to the present invention, as shown in FIG.
Similarly, as shown in FIG. 1, the thickness of the foil is set to １ ／ to ／,
The foil thickness surface layer has a subgrain structure 1 without recrystallized grains.
In this way, the concentration of deformation strain at the punch shoulder during drawing can be effectively prevented. That is,
When the ratio of the recrystallized grains existing in the thin layer such as less than 1/4 or the center of the foil thickness is less than 1% in cross-sectional area ratio, there is a possibility that the progress of the surface deformation cannot be completely prevented. Yes,
In the case of a thick layer exceeding 3/4, if the proportion of recrystallized grains exceeds 30% in cross-sectional area ratio, there is a possibility that cracks may occur at the punch shoulder due to hardening due to composition processing.

The aluminum foil of the composite structure according to the present invention has a composition of wt%, Fe: 0.10-0.8%, T
i: 0.001% or more and less than 0.02%, with the balance being impurities, and by making Si as an unavoidable impurity less than 0.15%, strength can be improved, and not only a foil sheet but also a preferred draw-formed container Get the foil. If the Fe content is less than 0.10%, for example, the strength after molding as a container is low, making it difficult to apply as a foil.
If it exceeds, there is a possibility that the ductility becomes insufficient and cracks occur during drawing. If the Ti content is less than 0.001 wt%, the crystal cracking during casting may be insufficient to cause casting cracks. If the Ti content exceeds 0.02 wt%, the effect of preventing casting cracks is saturated.

Note that, as a typical impurity, Si is made less than 0.15 wt% so as not to deteriorate the formability and corrosion resistance. Cu is also 0.15 for impurities other than Si.
wt%, Mn less than 0.03 wt%, Cr, V and Z
It is preferable that each of r is less than 0.015 wt%.

The composite structure foil of the present invention is preferably a slab rolled plate by a continuous casting technique, since the solid solution amount of the alloy element increases and strength can be effectively imparted.

The production of the composite texture foil according to the present invention is not limited to the method described below, but preferable requirements for the production method include a component composition, continuous casting and rolling conditions, and temper annealing. The composition is as follows.

Fe: 0.10 to 0.8 wt%. Fe is sufficiently solid-dissolved by continuous casting and rolling to impart strength and draw formability, and is precipitated by subsequent tempering annealing to cause recrystallized grains to be present in the center of the foil thickness, and to form recrystallized grains on the foil surface layer. If the Fe content is less than 0.10 wt%, the desired strength cannot be imparted, and if the Fe content exceeds 0.8 wt%, a coarse intermetallic compound is formed to form In addition to lowering the properties, a sub-grain structure in which recrystallized grains exist in the center of the foil thickness in the subsequent tempering annealing and no recrystallized grains exist in the sheet surface layer cannot be obtained. A more preferable range of such Fe content is 0.7 w.
t% or less.

Ti: 0.001 wt% to 0.02 wt%. Ti is contained in order to refine the crystal grains during continuous casting and prevent casting cracks. The content of this Ti
If the content is less than 0.001 wt%, the above-described effect is reduced, and
If the content exceeds 2 wt%, the effect of preventing casting cracks is saturated, and the entire foil has a fine sub-grain structure. In the subsequent tempering annealing, recrystallized grains are present only in the central portion of the sheet thickness, and the sheet surface layer A sub-grain structure without recrystallized grains cannot be obtained. The preferred upper limit of the Ti content is 0.1.
It is less than 015 wt%. The addition of Ti is preferably performed using an Al-Ti master alloy or an Al-Ti-B master alloy. When an Al-Ti mother alloy is used, B is contained, but if the amount is 0.002 wt% or less, the effect of the aluminum foil of the present invention is not impaired.

As unavoidable impurities, Si is typically less than 0.15 wt% so as not to lower the formability and corrosion resistance, but Cu is also less than 0.15 wt% as other impurities. It is preferable that Mn is less than 0.03 wt%, and Cr, V and Zr are each less than 0.015 wt%.

Continuous casting and rolling conditions. The continuous cast rolled foil is a foil having a desired thickness obtained by subjecting a slab obtained by continuous casting to cold rolling at a reduction ratio of 95% or more without intermediate annealing. The continuous casting and rolling is not limited to any method as long as it is a method capable of casting a slab by rapid solidification and rolling continuously.
For example, there is a water-cooled roll method in which molten aluminum is poured between a pair of opposed internal cooling rotating rolls and the cast slab is rolled without annealing, and as another method, a pair of cooled other sides is cooled. There is a method of injecting molten aluminum between rotating plates and rolling the cast slab without annealing. The casting conditions are, for example,
The temperature of the molten metal is 680-730 ° C, and the thickness of the slab is 70
mm or less, preferably 50 mm or less, more preferably 30 mm or less. When the thickness is 6 mm or less, it is difficult to realize a composite structure which is the gist of the present invention. The slab withdrawal speed is 50-150 cm / min.

Temper annealing. After performing cold rolling with a draft of 95% or more as described above,
A temper annealing treatment is performed at a temperature of 250 to 300 ° C. for 4 to 10 hours. This treatment is a temper annealing treatment for imparting high strength to the aluminum foil, in which Fe and Ti are appropriately deposited, and a quarter to three-thirds of the foil thickness at the center of the foil thickness.
In / 4, recrystallized grains are present at a ratio of 1 to 30% in cross-sectional area ratio, and other foil surface layers have a sub-grain structure, which is a composite structure of these re-crystallized grains and sub-grain structure. Things. If the rolling reduction is less than 95% and the tempering annealing temperature is less than 250 ° C and less than 4 hours, recrystallized grains as described above cannot be obtained. On the other hand, if the tempering annealing temperature exceeds 300 ° C., the area ratio of the recrystallized grains becomes too large, and if the recrystallized grains become too large, it becomes difficult to obtain the desirable composite metal structure aimed at by the present invention. It is not economical that the tempering annealing is performed for 10 hours or more.

[0027]

EXAMPLE An aluminum alloy melt having the composition (wt%) of the alloy of the present invention, the comparative alloy and the conventional alloy as shown in the following Table 1 was cast into a 7 mm-thick slab by a water-cooled roll method, and then cold-rolled. Then, a thin plate having a thickness of 0.100 mm was obtained.

[0028]

[Table 1]

Each of the foils obtained as described above was subjected to temper annealing under the annealing conditions shown in Table 2 below, and the aluminum foil thus obtained was then subjected to drawing. The results of forming and evaluating the moldability are also shown in the latter part of Table 2. Other characteristic values include the amount of Fe solid solution, the plate thickness in the range where recrystallized grains exist, the ratio of recrystallized grains, and the mechanical property limit drawing ratio (L
DR) was measured, and the results are also shown in Table 2.

[0030]

[Table 2]

The evaluation and measurement conditions in Table 2 described above are as follows. * Measurement of drawability (LDR) punch diameter 33Φ, shoulder R
Use 3 things. Using a fixed punch, changing the blank diameter and squeezing the cup, D. It was evaluated as R. There was no wrinkle holder and wax was used for lubrication.

In the comparative alloy foils of Tables 1 and 2 and the conventional alloy foil, an ingot having a slab thickness of 580 mm obtained by DC casting an alloy having the composition shown in Table 1 was used.
The foil was homogenized at 30 ° C. for 1 hour, hot-rolled to a thickness of 7 mm, and cold-rolled to a 0.100 mm foil. The foil was subsequently subjected to temper annealing. The temper annealing conditions were as shown in Table 2. The aluminum foil thus obtained was drawn and formed, and the formability was evaluated. This is the same as the case of the above-described embodiment, and the evaluation results are as shown in Table 2.

However, according to the results shown in Table 3 above, it is clear that the strength and elongation are both balanced and high, and the limit drawing ratio is high in any case of the present invention. On the other hand, it is clear that the conventional alloy foil obtained by the DC casting method has the same strength and the low elongation, and the strength is low at the same limit drawing ratio.

[0034]

According to the present invention as described above, since both strength and elongation are balanced and high, and the limit drawing ratio is high, a relatively thin foil can be used as a foil sheet for various kinds of packaging. The present invention has an effect that a container or the like can be easily and accurately drawn by the foil sheet to provide a preferable container at a low cost, and the effect is industrially large.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing a cross-sectional configuration of an aluminum foil according to the present invention.

[Explanation of symbols]

 1 Sub-grains 2 Recrystallized grains

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22F 1/00 685 C22F 1/00 685 686 686A 691 691B 691C 694 694A

Claims (8)

[Claims] 1. Fe: 0.1 to 0.8% by weight, T:
i: 0.001 to 0.02%, the balance being unavoidable impurities and Al, wherein Si in the unavoidable impurities is 0.15
%, Wherein the recrystallized grains are present in the center of the foil thickness, and the foil thickness surface layer has a sub-grain structure free of recrystallized grains. 2. The aluminum foil for a container according to claim 1, wherein the proportion of recrystallized grains existing at the center of the foil thickness is 1 to 30% in terms of area ratio in a cross section along the rolling direction. 3. The aluminum foil for a container according to claim 1, wherein the size of the recrystallized grains existing at the center of the foil thickness is 5 to 50 μm. 4. The method according to claim 1, wherein the thickness range of the central portion of the foil thickness where the recrystallized grains are present is ４ to ／ of the total foil thickness. Aluminum foil for containers. 5. A slab obtained by continuously casting a foil is subjected to cold rolling at a rolling reduction of 95% or more without intermediate annealing to obtain a foil having a desired thickness by continuous casting and rolling. The aluminum foil for a container according to any one of claims 1 to 4, wherein the aluminum foil is used. 6. In wt%, Fe: 0.10 to 0.8%, T
i: 0.001 to 0.02%, the balance being unavoidable impurities and Al, wherein Si in the unavoidable impurities is 0.15
%, And the slab obtained by continuous casting is subjected to cold rolling at a rolling reduction of 95% or more without intermediate annealing to obtain a foil having a desired thickness by continuous casting and rolling of an aluminum alloy. Wherein the recrystallized grains are present at the center of the foil thickness, and the layer thickness range of the center of the foil thickness where the recrystallized grains are present is １ ／ to ／ of the total foil thickness. An aluminum foil for a container, wherein the foil thickness surface layer has a sub-grain structure without recrystallized grains. 7. The aluminum foil for a container according to claim 1, wherein the foil is a foil for a draw-formed container. 8. In wt%, Fe: 0.10-0.8%, T
i: 0.001 to 0.02%, the balance being unavoidable impurities and Al, wherein Si in the unavoidable impurities is 0.15
% Of a slab obtained by continuously casting an aluminum alloy melt having a rolling reduction of less than 95% without intermediate annealing.
A method for producing an aluminum foil for a container, comprising performing the above-described cold rolling, and then performing temper annealing at a temperature of 250 to 300 ° C. for 4 hours to 10 hours.