JP2001049377A - Aluminum alloy plate for wide-mouthed tab excellent in repeated bending property and method for producing the same - Google Patents

Abstract

[PROBLEMS] To provide an aluminum alloy plate for a wide-mouthed stay tab having sufficient toughness to be repeatedly bent, having toughness that is not easily torn even when subjected to bending deformation, and also having excellent strength, and a method of manufacturing the same. provide. SOLUTION: Mg: contains more than 3.5% and not more than 5.0%,
It consists of a rolled aluminum alloy plate containing Mn: less than 0.40%, Fe: 0.35% or less, Si: 0.20% or less, the balance being Al and unavoidable impurities, and having a proof strength of 280-335M.
In Pa, when the length in the rolling direction of the crystal grains viewed from the surface of the rolled plate is L, and the length in the direction perpendicular to the rolling direction is W, L
Five or more crystal grains satisfying / W ≧ 8 and L ≧ 150 μm exist in 1 mm ² .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy sheet for a tab of a wide mouth lid having excellent repetitive bending property and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, 5042 aluminum alloy or 5
082 aluminum alloy has been used, but recently, in order to improve the tab strength, in most cases, 5182 aluminum alloy has been used. In Europe and the United States, recently, 5182 aluminum alloy has a yield strength exceeding 340 MPa. A high-strength material having the following characteristics is used as a tab material, and the cost is reduced by reducing the plate thickness. On the contrary,
In Japan, the quality requirements for tabs are strict.For example, in the case of an end with a stay-on tab, the tab may repeatedly move up and down when opening the can. Because of this, the behavior is different from that in Europe and the United States, such as the need to repeatedly improve bendability.

[0003] Recently, attempts have been made to increase the area of the drinking opening at the lid opening of a beverage can to make it easier to drink (Japanese Patent Application Laid-Open No. 10-296362, US Patent No. 5,711).
1,448). Specifically, in the case of a 350 ml can,
Conventionally, it is formed in a wide-mouthed lid which increases the area of an opening of about 300 mm ^{2 by} 20 to 30%. With such a wide opening of the beverage can, the opening score is longer than before, so the number of times the tab is bent back at the time of opening the lid is more likely to be increased than before, and when raising the tab, the tab is raised to a higher angle. In order to keep the force applied to the tabs, the tabs are easier to tear off and take off than before. This degree of property change is not regarded as a problem in the United States and Europe, but as mentioned above, the quality requirements for tabs are high in Japan, so with the improvement of the lid shape,
There is also a need to improve the material of the tab material used.

[0004] In order to meet the above requirements, the aluminum alloy plate for the tab of the wide-mouthed lid is required to have a good bending property of a test piece (0 ° direction test piece) whose longitudinal direction is the rolling direction. High toughness to prevent tearing,
Further, when formed into a tab, the tab has a predetermined strength so that the tab is not easily broken. These required characteristics are difficult to cope with with an aluminum alloy plate conventionally used as a tab.

Conventionally, many proposals have been made for aluminum alloy plates for tabs, but none of them have sufficient properties as aluminum alloy plates for tabs of wide mouth lids. For example, in Japanese Patent Publication No. 3-41539, intermediate annealing is performed in the middle of cold rolling to reduce the crystal grain width to 20 μm or less, and to improve the repetitive bending property. However, since the cold rolling reduction after the intermediate annealing is low, the repetitive bending property of the test piece in the 0 ° direction is not improved, and the proof stress is 24.4 kgf / cm ² (239MPa) at the maximum.
a), and the strength is too low for the tab material.

In Japanese Patent Publication No. 5-47617, intermediate annealing is performed during cold rolling to reduce the anisotropy of repeated bending characteristics. Insufficient repeat bending property. JP-A-5-263
Japanese Patent Publication No. 175 proposes a material having less Mg (Mg: 1 to 3%) than a conventional aluminum alloy as an aluminum material for a stay-ion tub having little softening over time. It is difficult to obtain sufficient strength as a tab material by baking treatment at 230 to 280 ° C. which is common in painting. Further, in the aluminum alloy plate described in JP-A-7-316711, since the amount of Mn added is large, it is difficult to obtain a repetitive bending property suitable for a wide palate, and the stainless steel plate proposed in JP-A-7-197217 is proposed. Since the aluminum alloy sheet for tabs also undergoes intermediate annealing during rolling, the repetitive bendability of the 0 ° direction test specimen is unlikely to reach a predetermined value.

As described above, in the conventionally proposed aluminum alloy material for a stainless steel tub, since the intermediate annealing is performed in the middle of the cold rolling, the anisotropy is reduced, and the bending property of the 0 ° direction test specimen is reduced. Does not reach the specified value. Therefore, it is not preferable especially for a wide-mouthed lid in which the repeated bending property in this direction is important, and the production cost is increased due to the additional intermediate annealing step. Further, an alloy with a reduced amount of Mg has a problem that the yield strength after painting is low and the tensile strength cannot be increased, so that the work hardening is small and a predetermined tab strength cannot be obtained, so that practical use is difficult.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems in the aluminum alloy material for a stainless steel tab and to obtain an aluminum alloy material suitable for a tab of a wide palate. The composition of the aluminum alloy for tabs was reviewed, and the relationship between the structural properties, strength properties, and the repetitive bending properties, important as tab materials, cracking properties when subjected to bending deformation, and tearing properties were examined from multiple perspectives. Its purpose is to have sufficient repetitive bending properties suitable for use as a stay-on tab of a wide-mouthed can lid with a wide open mouth area, and with toughness that is difficult to tear even when subjected to bending deformation. Another object of the present invention is to provide an aluminum alloy plate for a wide-mouthed tab having excellent strength and a method for producing the same.

[0009]

In order to achieve the above object, the aluminum alloy sheet for a tab of a wide mouth palate excellent in the repetitive bending property of the present invention contains Mg: more than 3.5% and 5.0% or less. Mn: less than 0.40%, Fe: 0.35% or less, Si:
It consists of a rolled plate of an aluminum alloy containing 0.20% or less, with the balance being Al and unavoidable impurities, and having a proof strength of 28%.
At 0 to 335 MPa, assuming that the length in the rolling direction of the crystal grains as viewed from the surface of the rolled sheet is L and the length in the direction perpendicular to the rolling direction is W, a crystal having L / W ≧ 8 and L ≧ 150 μm It is characterized in that five or more grains are present in 1 mm ² .

Further, the method for producing an aluminum alloy plate for a tab of a wide mouth lid excellent in repeated bending properties according to the present invention is described in US Pat.
g: more than 3.5% and not more than 5.0%, and Mn: 0.40%
%, Fe: 0.35% or less, Si: 0.20% or less,
After the ingot of the aluminum alloy consisting of Al and inevitable impurities is homogenized and hot-rolled, cold-rolling is performed at a working ratio of 80 to 92% without annealing during the cold rolling. It is characterized by.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The significance of the components in the aluminum alloy plate for a tab of a wide mouth (hereinafter, simply referred to as an aluminum alloy plate) of the present invention and the reasons for limiting the components will be described below.
Functions to increase the strength of the aluminum alloy plate. The preferred content range of Mg is more than 3.5% and 5.0% or less,
If the content is less than 3.5%, the strength is not sufficient, and if the content exceeds 5.0%, the hot rolling property and the cold rolling property are reduced, which is not suitable for industrial production. A more preferred content of Mg is in the range of 3.7-4.8%.

Mn, like Mg, functions to increase the strength of the aluminum alloy. The preferable content range of Mn is 0.40%
If it is less than 0.40%, the moldability is reduced. It is more preferably at most 0.35%, further preferably at most 0.20%. As the Mn content is smaller, the tabs are less likely to be torn, but it is difficult to recycle the lid material of A5182 aluminum alloy, and the strength is so low that the tabs are easily broken. It is preferable to contain it to some extent.

[0013] Fe in the aluminum alloy is contained as an impurity. The preferred content range of Fe is 0.35% or less,
If it exceeds 0.35%, the moldability will decrease. More preferably 0.
It is at most 25%, more preferably at most 0.15%. As the Fe content is smaller, the tabs are less likely to be torn. However, in order to reduce the Fe content, the purity of the metal must be increased, which increases the cost. It is necessary to keep the purity and the purity of the bullion not to be excessively increased.

[0014] Si in the aluminum alloy is contained as an impurity like Fe. The preferred content range of Si is 0.20
% Or less, and if it exceeds 0.20%, the moldability decreases. It is more preferably at most 0.15%, further preferably at most 0.10%. The lower the Si content, the more difficult it is to tear the tabs. However, the lower the Si content, the higher the purity of the base metal and the higher the cost. It is necessary to prevent the purity of the bullion from being excessively increased.

In the present invention, in addition to the above-mentioned components, it is preferable that the following considerations be made for Cu, Cr and Ti. Cu contributes to an increase in the strength of the aluminum alloy. However, if the Cu content exceeds 0.15%, it tends to crack during casting or hot rolling, and is not suitable for industrial production. Cr also contributes to increasing the strength of aluminum alloys,
If the content range of Cr exceeds 0.10%, crystallized substances are formed and the toughness is lowered, which is not preferable. Ti is effective in refining the cast structure. If the content of Ti is less than 0.01%, the effect is small, and if it exceeds 0.10%, no further effect can be expected. Rather, it becomes easy to form a coarse intermetallic compound, which is not suitable for industrial production.

The preferred proof stress of the aluminum alloy of the present invention is 2
When the pressure is less than 280 MPa, the tab strength after tab formation is low and not practical.
If the pressure exceeds MPa, the bendability is poor, and when a force is applied to the tab, the tab is torn off and easily detached from the lid, making it difficult to be suitable for a tab for a wide-mouthed can lid.

The preferred form of the crystal grains in the aluminum alloy of the present invention is L / L when the length of the crystal grains in the rolling direction as viewed from the surface of the rolled sheet is L and the length in the direction perpendicular to the rolling direction is W / L / 1 m of crystal grains with W ≧ 8 and L ≧ 150 μm
It is preferable that 5 or more are present in m ² . The form of the crystal grains is obtained by electropolishing the surface of the test material plate in a mixed solution of boric acid and chromic sulfate, electrolytic etching in an aqueous solution of boric acid and hydrogen fluoride, observing the crystal structure with a polarizing microscope, and rolling. The crystal grain length (L) in the direction and the crystal grain length (W) in the direction perpendicular to the rolling direction are measured to determine the L / W ratio. L /
When W ≧ 8 and L ≧ 150 μm crystal grains are present in 5 mm or more in 1 mm ² , the anisotropy of the repetitive bending characteristics is strong, and the repetitive bendability in the 0 ° direction test piece is good. .

A more preferred embodiment of the present invention is as follows. (1) Mg: contains more than 3.5% and not more than 5.0%.
n: 0.35% or less, Fe: 0.25% or less, Si: 0.15% or less, made of a rolled plate of an aluminum alloy containing the balance of Al and unavoidable impurities, with a yield strength of 280 to 335 MPa.
When the length in the rolling direction of the crystal grains viewed from the surface of the rolled sheet is L and the length in the direction perpendicular to the rolling direction is W, L /
An aluminum alloy sheet for tabs of a wide mouth lid excellent in repetitive bending properties, characterized in that five or more crystal grains of W ≧ 8 and L ≧ 150 μm exist in 1 mm ² .

(2) Mg: more than 3.5% and 5.0% or less, Mn: 0.35% or less, Fe: 0.15% or less, Si:
It consists of a rolled plate of an aluminum alloy containing 0.10% or less, with the balance being Al and unavoidable impurities.
At 335 MPa, when the length in the rolling direction of the crystal grains viewed from the surface of the rolled sheet is L, and the length in the direction perpendicular to the rolling direction is W, the crystal grains having L / W ≧ 8 and L ≧ 150 μm 1
An aluminum alloy plate for a tab of a wide mouth lid excellent in repetitive bending property, characterized in that five or more pieces are present in mm ² .

(3) Mg: more than 3.5% and 5.0% or less, Mn: 0.20% or less, Fe: 0.15% or less, Si:
It consists of a rolled plate of an aluminum alloy containing 0.10% or less, with the balance being Al and unavoidable impurities.
At 335 MPa, when the length in the rolling direction of the crystal grains viewed from the surface of the rolled sheet is L, and the length in the direction perpendicular to the rolling direction is W, the crystal grains having L / W ≧ 8 and L ≧ 150 μm 1
An aluminum alloy plate for a tab of a wide mouth lid excellent in repetitive bendability, characterized in that five or more are present in mm ² .

In order to manufacture the aluminum alloy sheet of the present invention, Mg is contained in an amount of more than 3.5% and not more than 5.0%.
An ingot of an aluminum alloy containing less than 0.40%, Fe: 0.35% or less, Si: 0.20% or less, and having a balance of Al and unavoidable impurities, is homogenized according to a conventional method,
After hot rolling, without annealing during cold rolling,
Cold rolling is performed to a predetermined thickness within a range of a working degree of 80 to 92%.

In the production process of this aluminum alloy, if intermediate annealing is performed during the cold rolling, the anisotropy of the repeated bending characteristics is reduced, and particularly the repeated bending property of the 0 ° direction test specimen is reduced. It is not suitable as a tab material for wide palate. Further, the preferable working range of the cold rolling in the manufacturing process of the aluminum alloy is 80 to 92%. Cold rolling degree of 8
If it is less than 0%, the cyclic bendability in the rolling direction is reduced, and if the cold rolling degree exceeds 92%, the strength tends to be high and the bendability is not only lowered, but also the number of cold rolling passes increases, and Not desirable for production.

Example 1 An aluminum alloy having a composition shown in Table 1 (compositions shown in Alloy Nos. 1 to 10) was melted, and ingots were formed by continuous casting. After cutting, 50
The mixture was homogenized at 0 ° C. for 8 hours. The ingot after the homogenization treatment was hot-rolled, and the hot rolling was completed at 340 ° C. Then, without intermediary annealing, the total cold work degree is 88%
Was cold rolled to a thickness of 0.33 mm. After the obtained alloy plate (cold rolled plate) is subjected to surface treatment, a water-based paint is applied and baked at the temperature shown in Table 2 to obtain a coated plate for tab forming (test materials No. 1 to 10). did.

With respect to the obtained coated sheet for tab forming (test material), according to the following method, (1) crystal structure, (2) area ratio of intermetallic compound, (3) mechanical properties, (4) number of times of repeated bending , And (5) tab strength. Table 2 shows the results.
It is shown in Table 3.

Mechanical properties: A JIS No. 5 test piece having a longitudinal direction in the rolling direction was sampled from the obtained coated sheet for forming a tab, and the tensile strength (TS) (MPa) and the proof stress (Y) were obtained from the test piece.
S) (MPa) and elongation (E) (%) are measured. Crystal structure: the above-mentioned electrolytic polishing of the plate surface of the coated plate for tab forming,
After the electrolytic etching, the crystal structure is observed with a polarizing microscope, and the crystal grain length (L) in the rolling direction and the crystal grain length (W) in the direction perpendicular to the rolling direction are measured, and the ratio (L / W) is measured. L / W ≧ 8 and L ≧ 150 in 1 mm ²
Count the number of μm crystal grains. Area ratio of intermetallic compound: 1m in area using an image analyzer
The intermetallic compound at m ² is measured and its area ratio is determined.

Number of times of repeated bending: Evaluation of a repeated bending test for bending and returning, which is a behavior when a lid is opened with a tab. The number of repetitive bendings is about 15% of the proof stress so that a load having a length of 200 mm and a width of 12.5 mm with the rolling direction as a longitudinal direction is applied without bending.
The bending test is repeated under the condition that a certain level of stress is applied.
As shown in FIG. 1, the number of times of bending is counted as one for each bending of 90 degrees.

Tab strength: The coated plate for forming the tab is made of standard St.
Press molding into olle type tabs. In this case, the thickness of the tab curl portion is set to 1.5 mm, which is common in recent commercial cans, the obtained tab is attached to a jig, and a force is applied to a portion where the finger of the tab is put by rotating the jig. The change in load is measured by an Instron tester, and the value at which the strength is reduced due to breakage or tearing of the tab is defined as the tab strength.

With respect to the coated plate for forming a tab, the above-mentioned test was evaluated as having passed a proof stress of 280 to 335 MPa, a repeated bending number of 6 times or more, and a tab strength of 30 N or more.

Comparative Example 1 An aluminum alloy plate having the composition shown in Table 1 (compositions shown in Alloy Nos. 11 to 17) was prepared by using the alloy No. 1 in Example 1. 1
After preparing the alloy plate (cold rolled plate) according to the same process as in Steps 10 to 10 and surface-treating it, applying a water-based paint and baking at a temperature shown in Table 2 to obtain a coating for tab forming. Plates (test materials Nos. 11 to 17) were used. About this coated plate for tab forming, as in Example 1, (1) crystal structure, (2) intermetallic compound area ratio, (3) mechanical properties,
(4) The number of repeated bending and (5) Tab strength were measured. The results are shown in Tables 2 and 3. In Tables 1 to 3, those which are out of the conditions of the present invention are underlined.

[0030]

[Table 1]

[0031]

[Table 2] << Table Note >> Crystal structure ：: L / W ≧ 8 and L ≧ 150μ
5 or more crystal grains exist in 1 mm ² . (See Fig. 2)

[0032]

[Table 3]

As shown in Tables 2 and 3, the test material No. 1 according to the present invention obtained in Example 1 was used. 1 to 10 are all about strength characteristics, number of repeated bending, and tab strength,
It showed good performance and passed the above criteria.

On the other hand, the test material N according to Comparative Example 1
o. 11 is because the amount of Si exceeds the range of the present invention,
As a result of an increase in the amount of the intermetallic compound of Mg ₂ Si, the toughness was reduced and the number of repeated bending was reduced. Test material No. In No. 12, since the amount of Fe exceeded the range of the present invention, the amount of the Al-Fe-Mn-based intermetallic compound increased, resulting in a decrease in toughness and a decrease in the number of repeated bending.
Test material No. In No. 13, since the amount of Mn was beyond the range of the present invention, the amount of the Al-Mn-Fe-based intermetallic compound increased, resulting in a decrease in toughness and a decrease in the number of repeated bending.

Test material No. In No. 14, since the Mg amount is less than the range of the present invention, the yield strength of the coated plate for tab forming is low, and the tab strength is also inferior. Test material No. In No. 15, since the amount of Mg exceeded the range of the present invention, ear cracks occurred during hot rolling, and a good coated plate for tab forming could not be obtained. Test material No. In No. 16, since the amount of Cu was large and the yield strength of the coated plate for tab forming exceeded the range of the present invention, the number of repeated bending was reduced. Test material No. In No. 17, since the baking temperature was higher than the normal temperature, the yield strength of the coated tab forming plate was less than the range of the present invention, and a predetermined tab strength could not be obtained.

Example 2 Alloy No. 1 in Table 1 After cutting the ingot of the aluminum alloy having the composition shown in FIG.
The mixture was homogenized at 500 ° C. for 6 hours. The ingot after the homogenization treatment is hot-rolled, and the end temperature of the hot rolling is set to 340 ° C.
Then, it cold-rolled to the thickness of 0.33 mm with the cold work degree shown in Table 4. After surface treatment of the obtained cold-rolled material,
A water-based paint was applied and baked at the temperature shown in Table 4 to obtain a tab-forming coated plate (test materials Nos. 18 to 19). 1) crystal structure, (2) intermetallic compound area ratio,
(3) Mechanical properties, (4) number of repeated bending, and (5) tab strength were measured. The results are shown in Tables 6 and 7.

Comparative Example 2 Alloy No. 1 in Table 1 The ingot of the aluminum alloy having the composition shown in FIG. 4 was subjected to hot rolling in the same manner as in Example 2,
Then, it cold-rolled to the thickness of 0.33 mm with the cold work degree shown in Table 4. After surface treatment of the obtained cold-rolled material,
A water-based paint was applied and baked at the temperatures shown in Table 4 to obtain the same items as in Example 2 for these tab-formed coated plates (tab-formed coated plates (test material No. 20)). . The results are shown in Tables 6 and 7. Tables 4-7
In the above, those deviating from the conditions of the present invention are underlined.

Comparative Example 3 Alloy No. 1 in Table 1 The ingot of the aluminum alloy having the composition shown in FIG. 4 was subjected to hot rolling in the same manner as in Example 2,
Thereafter, cold rolling including intermediate annealing was performed at a cold working degree of a condition shown in Table 5 to a thickness of 0.33 mm. After surface treatment of the obtained cold-rolled material, a water-based paint was applied and baked at the temperature shown in Table 5 to obtain a tab-formed coated plate (test materials No. 21 to 22). The same items as in Example 2 were measured for the coated plate for use. The results are shown in Tables 6 and 7. In Tables 5 to 7, the values out of the conditions of the present invention are underlined.

[0039]

[Table 4]

[0040]

[Table 5]

[0041]

[Table 6] << Table Note >> Crystal structure ×: L / W ≧ 8 and L ≧ 150μ
The number of crystal grains of m is less than 5 in 1 mm ² . (See Fig. 3)

[0042]

[Table 7]

As shown in Tables 6 and 7, the test material No. satisfying the conditions of the present invention. Nos. 18 and 19 showed good performance in all of the strength characteristics, the number of repeated bendings, and the tab strength, and passed the above evaluation criteria.

On the other hand, the test material No. In No. 20, since the degree of cold working exceeds the range of the present invention, the proof stress is increased and the number of times of repeated bending is reduced. In addition, the test material No. Compared with Nos. 18 and 19, two passes of cold rolling increase the cost. Test material No. In Nos. 21 and 22, the predetermined strength was obtained, but the intermediate annealing was performed during the cold rolling, and the degree of cold working after the intermediate annealing was less than the range of the present invention. The ratio was small, the anisotropy of the repeated bending characteristics was reduced, and the number of repeated bendings in the 0 ° direction test specimen was reduced.

[0045]

According to the present invention, there is provided an aluminum alloy plate for a wide-opening stay tab having a sufficient toughness, a toughness which is not easily torn even when subjected to bending deformation, and an excellent strength. A method is provided. The invention is also applicable for tabs on existing can lids that are not wide mouth.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a method of counting the number of times of repeated bending in the evaluation of an aluminum alloy material according to an embodiment of the present invention.

FIG. 2 shows a test material No. of Example 1 of the present invention. 4 is a polarizing microscope structure photograph showing the crystal structure as viewed from the plate surface of No. 4.

FIG. 3 shows the test material No. of Comparative Example 3. 21 is a polarizing microscope structure photograph showing a crystal grain structure as viewed from the plate surface of No. 21.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C22F 1/00 673 C22F 1/00 673 682 682 683 683 685 685Z 694 694A

Claims (2)

[Claims] 1. Mg: more than 3.5% (% by weight, hereinafter the same)
5.0% or less, Mn: less than 0.40%, Fe: 0.3%
5% or less, Si: 0.20% or less, the balance consists of a rolled plate of aluminum alloy consisting of Al and unavoidable impurities, the proof stress is 280-335MPa, and the length of the crystal grains as viewed from the surface of the rolled plate in the rolling direction Is L, and the length perpendicular to the rolling direction is W, L / W ≧ 8 and L ≧ 15
An aluminum alloy plate for a tab of a wide mouth lid excellent in repetitive bending properties, characterized in that five or more crystal grains of 0 μm exist in 1 mm ² . 2. The alloy contains Mg: more than 3.5% and 5.0% or less, further contains Mn: less than 0.40%, Fe: 0.35% or less, Si:
An ingot of an aluminum alloy containing 0.20% or less, with the balance being Al and unavoidable impurities, is homogenized, hot-rolled, and then annealed during cold rolling without reducing the workability to 80 to 92%. A method for producing an aluminum alloy plate for a tab of a wide mouth lid excellent in repetitive bending properties, characterized by cold rolling at a temperature.