JPH072248A - Aluminum lid highly resistant to rupture under high internal pressure - Google Patents

Abstract

PURPOSE:To make even a thin material sufficiently resistant to rupture by employing for a coated aluminum lid and aluminum alloy of specific alloy composition as the base material and selected as one having a prescribed post- coating strength to bending-stretching-tensile force or even a higher strength than the prescribed requirement and by molding it into a lid provided with an annular groove which reinforces the pressure resistance. CONSTITUTION:An organic resin-coated aluminum plate 1 is based on an alloy whose composition comprises 2.0-6.0wt.% Mg, 0.05-1.0wt.% Mn, 0.02-0.40wt.% Cr, 0.02-0.20wt.% Cu, 0.5wt.% or less of Su, 0.5wt.% or less of Fe, 0.5wt.% or less of Zn, and aluminum, This base material is processed into a coated aluminum plate which, after the coating, has a strength to bending-stretching- tensile force valued at 5N/mm<2> or more. A reinforcing annular groove 6 is so formed as to have a curved bottom at a depth (H) of 1.5-4.5mm below the middle panel 5 and with a radius of curvature (R) in the range of 0.20-1.00mm. As a result, eve in the case of decrease in thickness of the aluminum material, the product can be rendered resistant to rupture under high internal pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum lid having excellent resistance to breakage under high internal pressure, and more particularly to a can filled with contents having a high internal pressure such as carbonated beverages and beer. Regarding aluminum lids.

[0002]

2. Description of the Related Art In can lids for canned contents such as carbonated drinks, beer, etc. having self-pressure or so-called nitrogen-filled canned products in which liquid nitrogen is dropped at the time of filling the contents, the buckling pressure is generally 7 kgf / cm ² or more. It is required to secure. On the other hand, in order to reduce the material cost and the weight of the empty can, attempts have been made to reduce the plate thickness of the lid as much as possible. Aluminum is excellent in workability and flavor retention as a lid material, but it is inferior in strength compared to steel material, so there is a problem that the pressure resistance performance and buckling resistance performance of the lid decrease when the plate thickness is made thin. .

In order to solve this problem, it has already been done to improve the strength of the aluminum material and to make the lid shape excellent in pressure resistance. As a countermeasure for the former,
As an aluminum material, Mg, which has the effect of increasing strength,
The amount of alloy components such as Cu and Cr is increased, or the rolling ratio of final cold rolling is increased. Further, as a measure against the latter, Japanese Patent Laid-Open No. 3-27544 discloses that a reinforcing annular groove is provided at the peripheral edge of the central panel portion and the radius portion of the annular groove is formed to have a small radius of curvature. Has been done.

[0004]

The above-mentioned means is effective even if the aluminum plate is thin and the buckling resistance of the aluminum lid is 7 kgf / cm ² or more. It was still insufficient to prevent destruction in time. That is, an actual pressure-resistant can is sometimes placed in a considerably high temperature atmosphere such as in a summer automobile, and under such a condition, the internal pressure is further increased even after the lid is buckled, and 8 kgf / The pressure may be higher than cm ² .

In the case of a lid made of thin aluminum, under the internal pressure higher than the internal pressure that causes the buckling of the lid, a part of the lid is cracked and the contents leak out or the reinforced annular groove of the lid. There was a risk that the contents would explode in an explosive manner, with a large crack extending halfway around the radius part of. The occurrence of cracks due to the pressure rise during or after buckling cannot be solved by increasing the strength of the aluminum material or changing the pressure resistant shape. Rather, as the strength of the material increases, the shape of the lid also increases. The more excellent the pressure resistance deformation is, the more remarkable it appears.

Therefore, an object of the present invention is to provide an aluminum lid which is excellent in fracture resistance at high internal pressure even when the plate thickness of the aluminum material is reduced. Another object of the present invention is to provide an aluminum lid which has a predetermined buckling resistance and which effectively prevents breakage due to cracking or the like even when the internal pressure of the can exceeds the buckling resistance.

[0007]

According to the present invention, an organic resin-coated aluminum plate is produced in the production of aluminum formed by molding an organic resin-coated aluminum plate into a lid shape consisting of a central panel and a reinforced annular groove at the periphery thereof. , Mg 2.
0-6.0% by weight, Mn 0.05-1.0% by weight, C
r 0.02 to 0.40% by weight, Cu 0.02 to 0.
20% by weight, 0.5% by weight or less of Si, 0.5% by weight or less of Fe, 0.5% by weight or less of Zn, and the balance being an aluminum alloy composed of Al and inevitable impurities, and bending and tensile strength after coating. Is 5 N / mm ² or more, and the depth (H) from the center panel of the radius portion of the reinforced annular groove is 1.5 to 4.5 mm.
And the radius of curvature (R) of the radius portion is 0.20 to 1.0
Provided is a lid made of aluminum which is characterized by being in a range of 0 mm and which is excellent in fracture resistance at high internal pressure.

[0008]

According to the present invention, as the organic resin-coated aluminum plate to be molded into the lid, Mg 2.0 to 6.0% by weight, Mn
0.05-1.0 wt%, Cr 0.02-0.40 wt%, Cu 0.02-0.20 wt%, Si 0.5 wt%
Hereinafter, 0.5% by weight or less of Fe, 0.5% by weight or less of Zn, and the balance being an aluminum alloy composed of Al and unavoidable impurities as a base, and the bending and stretching tensile strength after coating is 5N.
Select and use a coated aluminum plate having a thickness of / mm ² or more.

Bending and stretching tensile strength in the present invention means
It means the strength required by the following measuring method. A rectangular test piece having a length of 15 mm in the rolling direction and a length of 40 mm in the direction perpendicular to the rolling is cut out from the aluminum plate coated with the organic coating. Using the jig for prebending shown in FIG. 1, the test piece (1) is bent 180 degrees in parallel with rolling. Two aluminum plates of the same thickness as the test piece are sandwiched between the pre-bend test pieces and placed on the base (2) of the processing device shown in FIG. 2, and a 3 kg weight (3) is dropped from a height of 450 mm to give an impact. Bending process. The bent test piece is opened so that the opening angle is about 90 degrees, the two aluminum plates used previously are removed, and then the processing device shown in FIG. It is placed on the base plate of 3 kg, and a 3 kg weight is dropped from a height of 450 mm to make the test piece flat. Using a tensile tester, the tensile strength of the bent and stretched part is measured.

In the past, it was completely unknown what kind of physical property of the aluminum material the crack generation due to the pressure rise at the time of buckling of the aluminum lid or after buckling, but in the present invention, the crack generation is caused. Has a close relationship with the bending and stretching tensile strength measured by the above method, and when the bending and stretching tensile strength is 5 N / mm ² or more, the occurrence of cracks during or after buckling is effectively prevented. I knew it would be done.

Reference was made to Examples and Comparative Examples described later.
Yes. In these examples, different tensile strengths, proof stresses and bending
For lids made from painted aluminum plate with stretched and tensile strength
Then, wrap it in a can filled with carbonated drink,
The results when stored for 24 hours are described in (Table
2). These results show that the painted aluminum sheet
There is no noticeable tendency between tensile strength and crack initiation,
With respect to the proof stress and the occurrence of cracks, cracks are
Is observed, but bending and stretching
Looking at the relationship between tensile strength and crack initiation, bending elongation
Strength is 5 N / mm ² Less than one cracks without exception
However, this bending and stretching tensile strength
5 N / mm² Above all, crack initiation is completely prevented.
You can see that it is.

Thus, it is important to select, as the organic coated aluminum plate to be molded into the lid, one having a bending and stretching tensile strength of 5 N / mm ² or more in order to prevent the lid from breaking at a high internal pressure. Understood. In the present invention, the flexural elongation tensile strength is defined as a value after coating with an organic resin, because of the influence of heating at the time of coating the organic resin, the flexural elongation tensile strength also changes (this will be described later). explain).

In the present invention, even when the aluminum plate is thinned, it is necessary that the resistance strength and the buckling withstand voltage are equal to or higher than the reference value. Therefore, the aluminum base material having the above-mentioned alloy composition is used.

The reason why the alloy composition is limited as described above is as follows. Mg is added to improve the strength, and the content thereof is limited to 2.0 to 6.0 wt% because the desired strength cannot be obtained if the content is less than 2.0 wt%.
This is because if it exceeds 0 wt%, ear cracks become large during rolling. Mn and Cr improve the strength and heat resistance, further improve the limiting drawing ratio, and make the crystal grains finer.
The reason for limiting the content to 0.02 to 0.40 wt% is that if the content is less than the lower limit, the above effect is small, and if it exceeds the upper limit, the limiting drawing ratio decreases, and cracks occur in the lid making process. Cu improves the strength and its content is 0.02-
The reason why the content is limited to 0.20 wt% is that if the amount is less than the lower limit, the effect is small, and if the amount exceeds the upper limit, cracking occurs during casting. Si and Fe are for improving formability, and the content of Si and Fe is 0.5 wt% or less, and Fe is 0.5 w.
The reason why the content is limited to t% or less is that if it exceeds 0.5% by weight, large crystallized substances are likely to be formed and the formability is deteriorated. Zn is effective in improving strength, preventing softening, and improving heat resistance, but if its content exceeds the upper limit, it tends to form a huge crystallized substance and deteriorates formability.

In the present invention, an aluminum plate having a thickness of 0.15 to 0.40 mm, particularly 0.20 to 0.30 mm can be used, and a thickness of 7.0 kgf /
The depth (H) from the center panel of the radius part of the reinforced annular groove so that a buckling withstand voltage of cm ² or more can be obtained.
Is 1.5 to 4.5 mm, especially 1.8 to 4.0 m
m, most preferably 2.0 to 3.5 mm,
The radius of curvature (R) of the radius part is also 0.20 to 1.00 m
m, especially 0.20 to 0.90 mm, most preferably 0.
It is 20 to 0.70 mm.

According to the present invention, as described above, a predetermined buckling withstand voltage is obtained while using a thin aluminum plate, and even if buckling occurs due to an abnormal increase in internal pressure in a high temperature atmosphere, cracks due to the buckling occur. Occurrence was prevented and the fracture resistance was remarkably improved.

[0017]

Preferred Embodiment of the Invention

Structure of Lid In FIGS. 3 (top view) and 4 (enlarged cross-sectional view) showing an example of a lid (easy open can lid) of the present invention, the lid 4 includes a central panel portion 5, a reinforced annular groove 6 and It consists of the outermost winding part. The central panel portion 5 has an expected opening portion 8 surrounded by a score 7, and an opening tab 9 is fixed via a rivet 10. The opening tab 9 includes a grip ring 11, a pushing tip 9, and a rivet fixing tongue piece 1.
3, and the push-in tip 12 is attached so as to overlap the planned opening portion 8. The reinforced annular groove 6 has the inner wall portion 1
4, radius portion 15 and outer wall portion (chuck wall) 1
The outer wall portion 16 is connected to the seaming panel portion 17 and the curl portion 18. A groove 19 is formed on the back side of the seaming panel portion 17 and the curl portion 18, and a sealing rubber composition (not shown) is lined in the groove 19 so that the groove 19 and a can body flange (not shown) are provided. Double sealing will be performed.

In the lid of the present invention, the depth H from the central panel portion 2 to the radius portion 15 of the reinforcing annular groove 6 is set to a relatively large range of 1.5 to 4.5 mm, while the curvature of the radius portion 12 is increased. By setting the radius (R) to a relatively small range of 0.20 to 1.00 mm, the buckling withstand voltage is increased. Also, the outer wall (chuck wall) 1
Although 6 is a taper shape that is opened upwards as a whole, the inner wall portion 14 and the outer wall portion 16 in the reinforced annular groove 6 are substantially vertical or nearly vertical surfaces in terms of buckling pressure resistance. Is preferred.

Lid Material The lid material used in the present invention is Mg 2.0 to 6.0% by weight,
Mn 0.05-1.0 wt%, Cr 0.02-0.40
Wt%, Cu 0.02 to 0.20 wt%, Si 0.5 wt
% Or less, Fe 0.5% by weight or less, Zn 0.5% by weight or less
Aluminum with bottom and balance consisting of Al and unavoidable impurities
Alloy, casting, homogenization, hot rolling, final cold rolling
To produce a thin plate and coat the thin plate with an organic resin.
Manufactured by. Between hot rolling and final cold rolling
In addition, cold rolling and annealing processes can be added in combination.
Wear. These steps are used for bending the final organic resin coated aluminum plate.
Stretching tensile strength is 5 N / mm ² Above, especially 15N / mm
² It should be controlled so that it is above.

As a general tendency, if the rolling ratio of the final cold rolling increases, the bending and tensile strength tends to decrease, so that the final cold rolling ratio is preferably 80% or less, particularly 70% or less. . Further, for the purpose of reducing the final cold rolling rate to produce a thin plate, it is also effective to carry out the primary cold rolling and the annealing followed by the final cold rolling after the hot rolling.

Further, it is possible to obtain an aluminum material having a high bending strength and a high tensile strength while increasing the final cold rolling rate to 80 to 90%. In this case, annealing is performed at a temperature of 150 to 600 ° C. You can go in.

The formation of the organic resin coating on the aluminum substrate can be carried out by coating an organic resin paint or heat laminating the organic resin film. These coatings are accompanied by heating of the aluminum substrate, but generally, the higher this temperature, the higher the bending / stretching tensile strength of the coated metal sheet.

As described above, the flexural elongation tensile strength of the coated aluminum plate is determined by the final cold rolling rate of the aluminum plate and
Since it depends on two factors, that is, the temperature and time at the time of coating with the organic resin, it is preferable to combine the final cold rolling rate and the temperature and time at the time of coating so as to obtain the above-mentioned bending and stretching tensile strength. Good. Generally, the heating conditions for the organic resin coating are
It is advisable to perform the heating so that the peak temperature of the aluminum substrate is 200 to 350 ° C. and the total heating time is 10 seconds to 30 minutes. When the final cold rolling rate is low, low temperature and short time are allowed. .

The thickness of the aluminum substrate in the lid material is 0.
15 to 0.40 mm, especially 0.20 to 0.30 mm
If it is thicker than the above range, the material cost is disadvantageous, while if it is thinner than the above range, pressure resistance and deformation of the lid are unsatisfactory. Further, the tensile strength of 330N / mm ² or more, proof stress (strength at elongation of 0.2%) is 260 N / mm ² or more, while reducing the thickness is preferable in terms of increasing the pressure resistance.

As the organic resin applied to the aluminum substrate, in the case of paint, a thermosetting resin paint such as phenol-formaldehyde resin, furan-formaldehyde resin, xylene-formaldehyde resin, ketone-formaldehyde resin, urea-formaldehyde resin, melamine- Formaldehyde resin, alkyd resin, unsaturated polyester resin, epoxy resin, bismaleimide resin, triallyl cyanurate resin, thermosetting acrylic resin, silicone resin, oil resin, or thermoplastic resin paint, such as vinyl chloride-vinyl acetate copolymer Examples thereof include a polymer, a partially saponified vinyl chloride-vinyl acetate copolymer, a vinyl chloride-maleic acid copolymer, a vinyl chloride-maleic acid-vinyl acetate copolymer, an acrylic polymer, and a saturated polyester resin. These resin paints may be used alone or in combination of two or more. Among these, epoxy-
Phenol-based paints, epoxy-amino-based paints, vinyl paints, vinyl-epoxy-phenol-based paints and the like are preferable.

The thickness of the paint is 2 to 2 when dried.
It is preferably in the range of 0 μm, particularly 3 to 15 μm. The coating is performed by means known per se such as roller coating, blade coating, spray coating, etc., and the baking of the coating film is performed in a hot air oven, an infrared heating oven or the like so as to satisfy the above conditions.

On the other hand, when the organic resin coating is a film, a polyester film mainly containing ethylene terephthalate units, various nylon films, olefin resin films, etc. are used, and these are biaxially stretched films. However, unstretched or uniaxially stretched ones are also used. Film thickness is 10 to 50
It is preferably in the range of 10 μm to 40 μm.

The film is laminated so that the film is made of Al.
In the case of having a heat-adhesive property, it is performed by stacking an aluminum plate and a film and directly heat-bonding them, but it is necessary to interpose an adhesive primer, an adhesive layer or an anchoring agent between them. You can Examples of the adhesive primer and the adhesive include an epoxy-phenolic primer, a urethane adhesive, an epoxy adhesive, an acid-modified olefin adhesive, and an anchor agent such as an organic titanate or isocyanate anchor agent. To be Lamination is easily carried out by laminating a film on an aluminum plate, temporarily adhering the film if necessary, and then heating the aluminum plate by high-frequency induction heating or electric heating and passing them through a pressure contact roller or the like. To satisfy the above conditions.

Molding of Lid The molding of the lid of the present invention can be carried out by a molding method known per se except that the above-mentioned lid material is used and the size of the reinforced annular groove is within the above range. . First, the coated aluminum plate or coil is stamped into a predetermined shape and size, and then or simultaneously, it is formed into a lid by a press die. As the press die, the one described in JP-A-3-275443 cited above can be used, but it is not limited to this.

[0030]

The present invention will be further described in the following examples. The evaluation of Examples and Comparative Examples was performed as follows.

Molding of Lid (1) Molding of 200-diameter lid in Examples 1 to 5 and Comparative Examples 1 to 3 An epoxy-phenolic coating material was applied to an aluminum substrate having a plate thickness of 0.22 mm so that the thickness when dried was 10 μm. The depth (H) from the center panel of the radius portion of the reinforced annular groove is 2.5 by the method described in Japanese Patent Laid-Open No. 3-275443 using an organic resin-coated aluminum plate coated on.
mm and radius of curvature (R) of the radius part is 0.50 mm
A lid with a diameter of 200 was molded. (2) Molding of 206-diameter lid in Examples 6 to 13 and Comparative Examples 4 to 8 Organic resin coating in which an epoxy-phenolic coating material was applied to an aluminum substrate having a plate thickness of 0.25 mm so that the thickness when dried was 10 μm. The depth (H) from the center panel of the radius portion of the reinforced annular groove is 2.5 using an aluminum plate and the method described in JP-A-3-275443.
mm and radius of curvature (R) of the radius part is 0.50 mm
A lid with a diameter of 206 was molded.

Pressure resistance measurement Steel DI cans having an internal capacity of 250 g and 350 g were filled with about 90% of the internal capacity of water, and the lid was wound. A hole was opened in a part of the can body, a plastic tube was joined with an adhesive, and the other end of the tube was connected to a pressure device in which a pressure gauge was installed. The pressure was increased, and the pressure when part of the lid buckled was read and used as the pressure resistance.

Evaluation of breakage resistance of the lid at high pressure: A steel DI can having a capacity of 250 g and 350 g was filled with a carbonated beverage having a gas volume of 4.0, and after the lid was wound up, it was placed in a thermostatic chamber at 80 ° C. for 24 hours. Saved for hours. Number of tests is 1 each
00 cans. After 24 hours, the state of the lid was visually inspected, and the number of cans in which the contents leaked due to microcracks in the lid, large cracks with a length of half the circumference around the chuck wall of the lid, and the contents burst out explosively. The number of cans was evaluated. Also,
With respect to the lid in which the above-mentioned small cracks and large cracks did not occur, the cross-section of the bent portion caused by buckling was observed and evaluated by the number of canned holes in the plate thickness, which is a precursory phenomenon of cracking.

Examples and comparative examples are shown below. Examples 1 to 13 and Comparative Examples 1 to 8 Table 1 shows the component composition of the aluminum substrate in the organic resin-coated aluminum plates of Examples 1 to 13 and Comparative Examples 1 to 8, the final cold rolling rate, and the organic resin. The coating conditions of are shown below.
In Table 2, bending and stretching tensile strength of the organic resin-coated aluminum plates of Examples 1 to 13 and Comparative Examples 1 to 8, tensile strength, proof stress, and pressure resistance of a lid molded using the organic resin-coated aluminum plate, The results of evaluation of fracture resistance at high pressure are shown. As in Examples 1 to 13, the lid using the organic resin-coated aluminum plate having a bending / stretching tensile strength of 5 N / mm ² or more has a micro crack in the lid under an internal pressure higher than the internal pressure at which the lid causes buckling. As a result, the contents are not leaked or a large crack having a length of half the circumference is not formed around the chuck wall of the lid, and the contents are not explosively ejected.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

According to the present invention, as the coated aluminum lid material, one having a base made of an aluminum alloy having a specific alloy composition and having a bending and stretching tensile strength after coating of 5 N / mm ² or more, By molding this into a lid with a pressure-resistant annular groove, sufficient buckling withstand pressure is maintained even when the thickness is thin, and when the internal pressure rises abnormally due to high temperature atmosphere, etc., buckling occurs. In addition, it is possible to effectively prevent the occurrence of cracks and to impart fracture resistance at high internal pressure.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a bending process of a sample used for measuring bending and stretching tensile strength.

FIG. 2 is an explanatory diagram showing a stretching process of a sample used for measuring bending and stretching tensile strength.

FIG. 3 is a top view of an example of the lid of the present invention.

4 is an enlarged cross-sectional view of the lid of FIG. 3 taken along the line AA.

[Explanation of symbols]

 1 Organic Resin-Coated Aluminum Plate 2 Base 3 Weight 4 Easy Open Can Lid 5 Center Panel 6 Strengthening Annular Groove 7 Score 8 Planned Opening Area 9 Opening Tab 10 Rivet 11 Grip Ring 12 Pushing Tip 13 Rivet Fixing Tongue Piece 14 Inner wall 15 Radius 16 Outer wall

Claims (2)

[Claims] 1. An aluminum lid formed by molding an organic resin-coated aluminum plate into a lid shape consisting of a central panel and a reinforced annular groove on the periphery thereof, wherein the organic resin-coated aluminum plate is Mg 2.0 to 6.0.
% By weight, Mn 0.05-1.0% by weight, Cr 0.0
2 to 0.40 wt%, Cu 0.02 to 0.20 wt%, Si 0.5 wt% or less, Fe 0.5 wt% or less, Zn 0.5 wt% or less, and the balance Al and unavoidable impurities. Is a coated aluminum plate which is made of an aluminum alloy consisting of and has a bending and stretching tensile strength of 5 N / mm ² or more after coating, and the depth (H) of the radius portion of the reinforced annular groove from the central panel is 1.5 to 4.5 mm and radius of curvature (R) of radius part is 0.20 to 1.00 mm
The aluminum lid is excellent in fracture resistance at high internal pressure and is in the range of. 2. The organic resin-coated aluminum plate has a proof stress of 260 to 330 N / mm ² and the substrate has a thickness of 0.
The range of 15 to 0.40 mm.
The aluminum lid described.