JPH07197176A - Al alloy sheet for full open-end having excellent can openability - Google Patents

Abstract

PURPOSE:To produce an Al alloy sheet for food can full open-end having excellent can openability. CONSTITUTION:This Al alloy sheet for food can full open-end has the chemical composition composed of 1.70-2.70%Mg, 0.30-0.60% Mn, 0.10-0.30% Fe as the essential components, and as necessary, further containing one or more kinds of <=0.30% Si, <=0.20% Ti and <=0.20% Cu and the balance Al with inevitable impurities and 0.3-1.0% area possessing ratio with Al-Fe-Mn intermetallic compound of 3-20mum when observing from the surface of the product sheet and has excellent can openability. After executing homogenizing treatment at 470-530 deg.C to an Al alloy cast ingot having this chemical composition, hot-rolling is applied, and further, cold-rolling is applied at >=30%, and after applying intermediate annealing in the temp. range of 360-540 deg.C, the cold-rolling is applied at 30-80% to produce the objective Al alloy sheet adjustable its strength without applying the annealing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an end material for food cans of food packaging excluding beverage cans, and more specifically, it does not require a can opener to open a can and is attached to a can lid. )
The present invention relates to an Al alloy plate for a full open end (hereinafter referred to as FOE) in which a can lid is opened at the entire surface by pulling up a tab, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Food cans are tin plates, aluminum materials, and tin-free steel (T
It is a container made of thin plates such as FS) and filled with food.
The food is hermetically sealed and heat-sterilized, or food that has been heat-sterilized in advance is aseptically filled and sealed to be canned.

Up to now, the lid of a food can has been very troublesome because it requires a can opener to open the can, but in recent years, the can opener is not required to open the can and the RP tab attached to the can lid is pulled up. The FOE in which the can lid is opened over the entire surface is becoming popular.

Aluminum and tin are used for FOE, but aluminum is becoming popular from the viewpoint of can openability. However, since the FOE has a large opening, the open can load is higher than that of the partial open end used for beverage cans and the like, and it is necessary to reduce the open can load.

In the FOE, a wedge-shaped press-fitting process called a score is applied to the opening after painting so that the can can be opened easily, and the open-can load can be reduced by increasing the score processing rate. Although it is possible to achieve this, a coating film defect on the inner surface of the can lid becomes large, and corrosion may occur from the coating film defect portion depending on the content.

[0006] Further, in order to repair a coating film defect, if a heat treatment is performed after score processing due to repair or retort, the can open load tends to increase and the can open property tends to decrease.

Conventionally, AA has been used as the FOE material for food cans.
A material obtained by hot rolling an Al alloy ingot having components such as 5052 and then cold rolling at a relatively high rolling rate is used. However, in the case of using the AA5052 alloy, score tearing at opening can Since the load was high and the progress of tearing was poor, there were cases where cracks occurred in places other than the score, and the entire drinking mouth was not opened. Although the tearing load is reduced by increasing the strength, it is necessary to carry out higher cold rolling in order to improve the strength with the AA5052. However, in the case of high cold rolling, the crystal grains are flat. There is a problem that the grains become elongated and the rivet workability for attaching the RP tab, which is one of the important characteristics of FOE, deteriorates.

On the other hand, the AA5182 alloy, which is often used for the partial end of beer, carbonated drinks, etc., has high strength, and it is possible to obtain sufficient strength for reducing the tearing load when opening the can. However, many 3P (piece) cans made of tin are used as food cans.
Since the shock absorption of the body is inferior, cracks may occur at the score part. Therefore, it is disadvantageous to significantly increase the strength in order to maintain the impact absorbability of the end itself.

The manufacturing method proposed in JP-A-63-286546 is a method for manufacturing a can end material such as a beverage can. In this method, after cold working to a final plate thickness, 100 to Although the strength is adjusted by finish annealing at a temperature of 250 ° C., the material subjected to finish annealing has a large amount of deformation at the time of can opening, which increases the can opening load.

Therefore, the conventional materials and manufacturing methods cannot satisfy the required characteristics as the FOE end material for food cans, and in order to improve the can openability, a material having sufficient tearability is required. Will be needed.

The present invention has been made to solve the above-mentioned problems of the prior art and to meet the above-mentioned needs, and provides an Al alloy plate for food can FOE excellent in can openability and a method for producing the same. That is the purpose.

[0012]

Means for Solving the Problems As a means for solving the above problems, the present invention provides Mg: 1.70 to 2.70%,
Mn: 0.30 to 0.60%, Fe: 0.10 to 0.30% are contained as essential components, and if necessary, Si ≦ 0.30.
%, Ti ≤ 0.20%, Cu ≤ 0.20%, and the balance has a chemical component of Al and unavoidable impurities. 20 μm Al
-Fe-Mn intermetallic compound has an area occupancy ratio of 0.3 to 1.0.
The main feature is an Al alloy plate for a food can full open end having excellent openability.

According to another aspect of the present invention, an Al alloy ingot having the above chemical composition is subjected to a soaking treatment at 470 to 530 ° C., followed by hot rolling and further 30% or more cold rolling. , An intermediate anneal in the range of 360 to 540 ° C., and then cold rolling at a rolling rate of 30 to 80% to adjust the strength without finish annealing, which is excellent in can openability. The gist is the manufacturing method of the Al alloy plate for can full open end.

[0014]

The present invention will be described in more detail below. First, the results of the study leading to the knowledge of the present invention will be described.

In order to achieve the above object, the present inventors have
Focusing on the improvement of can openability when increasing the amount of intermetallic compounds using existing materials, Al for food can FOE with excellent can openability
For the purpose of developing alloy materials, earnest research was repeated.

First, the inventors of the present invention investigated the relationship between the intermetallic compound and the can openability.
It was found that the tearing load when opening the can was reduced. The fact that the increase in intermetallic compounds contributes to the improvement in tearability is
"Proceedings of the 74th Spring Meeting of the Japan Institute of Light Metals" p.91-
As disclosed in 92, in this technology, 300
It is shown that when a score is given to the No. 4 alloy plate, a large increase in the Fe addition amount is necessary to reduce the tearing load.

However, considering the corrosion resistance and the formability of the food can FOE targeted by the present invention, the upper limit of the Fe addition amount is 0.3%, and it is expected that the can openability will be greatly improved only by the Fe addition amount. It was determined that it could not be done.

Therefore, when the Fe and Mn amounts and the manufacturing conditions were adjusted and the intermetallic compound diameter was changed, it was found that the tearability could be improved with a relatively small amount of Fe added.

The effect is remarkably observed in the Al-Fe-Mn type intermetallic compound at 3 µm or more, and it has been proved that the larger the intermetallic compound diameter is, the better if the area ratio is the same. did. However, it has been found that it is necessary to control the grain size to 20 μm or less because coarsening of the intermetallic compound leads to deterioration of rivet formability, which is an important characteristic of FOE.

In addition, the strength range of FOE (proof strength 215-2
At 75 N / mm ² ), it was found that the one with relatively high strength has better can openability, and the one without stability annealing after finish cold rolling has better tearability and improves can openability. .

Therefore, it has been found that by appropriately controlling the rolling ratio after the intermediate annealing, a material for food can FOE having relatively high strength and excellent can openability can be obtained without stabilizing annealing. .

The present invention makes it possible to achieve the initial objectives by adjusting the chemical composition based on such knowledge and controlling the conditions of soaking conditions and cold rolling steps (including intermediate annealing). It was done.

Next, the reasons for limiting the chemical composition of the Al alloy in the present invention will be explained.

Mg: Mg is an important element for imparting strength, and is an essential component in the present invention. Sufficient strength cannot be obtained unless at least 1.70% is added as a food can FOE material. However, if added too much, the strength may be too high and the score may crack due to the impact at the time of dropping, and the moldability may be deteriorated. Therefore, the upper limit of the addition amount is 2.70%. Therefore, the addition amount of Mg is set to the range of 1.70 to 2.70%.

The addition of Mn: Mn has a great effect on the formation and strength improvement of the Al-Fe-Mn intermetallic compound which improves the tearability contributing to the improvement of the can openability, and Mn is also an essential component in the present invention. It is a thing. At least 0.30% or more must be added for the effect of improving tearability to appear. However, if it is added in excess, the number of fine intermetallic compounds produced becomes too large, resulting in a decrease in moldability and a failure to improve the can openability. Therefore,
The amount of Mn added is 0.30 to 0.60%.

Fe: The addition of Fe improves the can openability.
It has an effect on the formation of -Fe-Mn-based intermetallic compounds. Also,
It has a great effect on the refinement of crystal grains which improves the moldability, which is a characteristic required for the end material, and the higher the addition amount, the finer the grain. However, if less than 0.10%, the effect is not recognized, and if more than 0.30% is added, the food can F
Corrosion resistance, which is an important characteristic of OE, is deteriorated, and the number of large intermetallic compounds and crystallized substances is increased, resulting in deterioration of formability. Therefore, the addition amount of Fe is set to 0.10 to 0.30%.

Intermetallic compound: By adding Fe and Mn (F
Although an intermetallic compound such as e, Mn) Al ₆ is produced, it is the intermetallic compound of 3 μm or more that contributes to the improvement of the can openability, and it is necessary to adjust it depending on the production conditions. However, the formation of the giant intermetallic compound causes a decrease in formability.
It is necessary to control to less than μm. Also, when viewed from the surface of the product plate, the area occupancy of these intermetallic compounds is 0.3 to
It is preferably 1.0%. This is because if it is less than 0.3%, the effect of tearing property is not recognized, and if it exceeds 1.0%, the moldability is significantly lowered.

In the present invention, the above Mg, Mn and Fe are used.
Is an essential component, but it is possible to include one or more of the following elements in appropriate amounts as needed.

Si: The addition of Si has an effect on the formation of the Mg-Si based intermetallic compound which improves the tearability. But,
If it is added in excess, the number of intermetallic compounds produced will become too large and the formability will be markedly reduced.
30% or less.

Ti: Ti is an element effective for stabilizing the structure, but if it is added in a large amount, it forms a giant intermetallic compound and reduces the formability. Therefore, Ti
The amount added is 0.20% or less.

Cu: Addition of Cu is effective in improving strength.
However, if added excessively, corrosion resistance, which is an important property as an end, is deteriorated, and work hardening becomes large, resulting in too high strength and deterioration of moldability. Therefore,
The added amount of Cu is 0.20% or less.

Next, the manufacturing process of the present invention will be described.

The Al alloy having the above chemical composition is melted and cast by a conventional method. The obtained ingot is subjected to a homogenizing heat treatment in which the Al-Fe-Mn intermetallic compound found on the surface of the product sheet is used. It is carried out under the conditions of 3 to 20 μm, that is, 470 to 530 ° C. If the homogenizing heat treatment temperature is lower than 470 ° C, the intermetallic compound cannot grow sufficiently, so that the can openability is deteriorated. On the other hand, if it exceeds 530 ° C, burning occurs, or even if it does not occur, a fine intermetallic compound is generated. It is not preferable because it becomes too much and the moldability is remarkably lowered.

After the homogenizing heat treatment, hot rolling and cold rolling are carried out. In the present invention, as shown below, a cold rolling process including intermediate annealing under predetermined conditions is carried out to improve the openability. It is characterized by setting a strength level effective for improvement.

First, the cold rolling rate before intermediate annealing is 30%.
If it is less than 30%, the crystal grains after the intermediate annealing become large and the formability, which is a required characteristic of the end, is adversely affected. Therefore, 30% or more is required. Considering the formability at the product thickness, it is preferably 60% or more.

Next, the intermediate annealing is performed, and the temperature of the intermediate annealing is set in the range of 360 to 540 ° C. The reason is 360
This is because if the temperature is lower than ℃, unrecrystallization is caused and the moldability is lowered, and if the temperature exceeds 540 ° C, the crystal grains are coarsened and the moldability is also lowered.

Cold rolling after the intermediate annealing is a condition that greatly affects the strength, and if the rolling ratio is less than 30%, the required strength cannot be obtained. Although increasing the rolling rate is effective for improving strength, the anisotropy of the material increases when the rolling rate exceeds 80%, and the anisotropy of the open can load depends on the processing direction of the opening relative to the rolling direction of the material. Occurs. Further, since the formability is significantly reduced, the cold rolling rate after the intermediate annealing is 30 to 80.
The range is%.

The strength is adjusted by the above manufacturing steps and conditions. If the finish annealing is not applied, the formability is improved when the strength is adjusted to the same strength by the finish annealing.
This is because the amount of deformation at the time of can opening becomes large and the can opening load increases.

Next, examples of the present invention will be shown.

[0040]

Example 1 An ingot of an Al alloy having the chemical composition shown in Table 1 was held as a homogenizing heat treatment at a temperature of 510 ° C. for 4 hours, and then hot-rolled to a plate thickness of 2.0 mm. Then, after cold rolling to a plate thickness of 0.75 mm for each test material, the plate thickness is subjected to heat treatment in a continuous heating annealing furnace at an ultimate temperature of 420 ° C. and a holding time of 0 seconds, and further cold rolled. The thickness is 0.25 mm. For this cold rolled sheet,
Since the end material is molded after painting, 200 ° C x 20
A baking process was performed for a minute, and the same conditions as those for coating were applied. Table 2 shows the material properties (mechanical properties, tear load, rivet overhanging property) of the test material having a product plate thickness of 0.25 mm after the baking treatment.

The tear test method is as shown in FIG. First, a square-shaped score is processed on a 40 × 40 mm plate. The remaining thickness after score processing is the general FOE (140
.About.150 .mu.m). Then fix the plate,
It was pulled up in the same direction as the score processed surface, and the maximum load at the time of tearing was measured.

As shown in FIG. 2, the rivet overhanging test was performed with a ball head punch having a punch diameter of 6 mmφ and a tip 3R of 25 mm.
A 25 mm plate was subjected to overhanging with a constant wrinkle pressing force, and the overhanging height was changed to determine the limit height.

The following is considered from Table 2. All of No. 1 to No. 3 of the present invention have a low can-opening load and are excellent in can-opening property. It also has sufficient rivet overhang formability, which is a necessary characteristic of FOE materials.

On the other hand, Comparative Examples No. 4, No. 6, No. 8 and
Since No. 10, No. 12, and No. 13 do not have an intermetallic compound area occupancy rate or sufficient strength for improving the can openability, a reduction in tear load is observed. Also,
Comparative Examples No. 5, No. 7, No. 9, No. 10 and No. 1
In No. 1 and No. 12, the intermetallic compound increased excessively and the strength was too high, so that deterioration of moldability was observed.

[0045]

[Table 1]

[0046]

[Table 2]

[0047]

Example 2 A plate was manufactured from an Al alloy ingot having the same chemical composition as No. 2 in Table 1 under the manufacturing conditions shown in Table 3, and the yield strength, tear load, and rivet overhang limit height were examined.
The results are also shown in Table 3.

As is clear from Table 3, No. 14 to No. 18 of the Al alloy plate obtained by the production method of the present invention are
It can be seen that all show good tearability and moldability.

On the other hand, Comparative Examples No. 19 to No. 2
6 is out of the manufacturing conditions, so lack of strength,
Tear load increases due to excessive strength, and moldability decreases. In Comparative Example No. 26, finish annealing was performed after cold rolling to adjust the yield strength to that of Inventive Example No. 16, but the formability was improved, but the open can load increased. You can see that This is because the increase in elongation due to finish annealing promotes the deformation in the vicinity of the fracture portion at the time of score fracture during opening of the can, and the load required for the deformation increases.

[0050]

[Table 3]

[0051]

As described in detail above, according to the present invention,
In the material for food can FOE, the load at the time of opening the can after the retort and repair is relatively low, and it is possible to obtain a material that sufficiently satisfies the end characteristics, and it is possible to sufficiently cope with thin wall and high strength. It is also excellent in terms of manufacturing (stability, cost).

[Brief description of drawings]

FIG. 1 is a diagram illustrating a can opening test method.

FIG. 2 is a diagram illustrating a rivet overhanging test method.

Claims (3)

[Claims] 1. In weight% (hereinafter the same), Mg: 1.70-
2.70%, Mn: 0.30 to 0.60%, Fe: 0.10
It contains 0.30% as an essential component, and the balance has a chemical component consisting of Al and unavoidable impurities, and when viewed from the surface of the product plate, an Al-Fe-Mn-based intermetallic compound of 3 to 20 μm has an area occupation rate An Al alloy plate for a food can full open end having excellent openability, which is characterized by being 0.3 to 1.0%. 2. Further, if necessary, Si ≦ 0.30%, Ti
The Al alloy plate according to claim 1, containing one or more of ≤0.20% and Cu ≤0.20%. 3. An Al alloy ingot having the chemical composition according to claim 1 or 2 is subjected to soaking treatment at 470 to 530 ° C., hot rolled, and further cold rolled to 30% or more. , An intermediate anneal in the range of 360 to 540 ° C., and then cold rolling at a rolling rate of 30 to 80% to adjust the strength without finish annealing, which is excellent in can openability. Manufacturing method of Al alloy plate for can full open end.