JP2011208283A - Aluminum alloy sheet for bottle can - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy sheet for a bottle can which has excellent formability upon production of a bottle can and with which the bottle can produced has sufficient can body strength (buckling strength) without increasing the present sheet thickness/weight.SOLUTION: The aluminum alloy sheet has a composition comprising prescribed amounts of Cu, Mg, Mn, Fe and Si, and the balance Al with inevitable impurities, and in which the contents of Mn, Mg and Fe satisfy 5.450<{5.66×Mn(mass%)+0.667×Mg(mass%)+2.17×Fe(mass%)}<7.550. The elongation of the aluminum alloy sheet is 5.0 to 8.0%, also, the average aspect ratio of the crystal grains is ≥3.0, the 0.2% proof stress after heat treatment of the aluminum alloy sheet is >270 to 290N/mm, and the earing ratio of the aluminum alloy sheet is -2 to +3.5%.

Description

  The present invention relates to an aluminum alloy plate for bottle cans as a material for bottle cans used as various beverage cans.

  Conventionally, as a bottle can, as shown in FIG. 1, there is a two-piece bottle can 1 in which a body portion 2 and a bottom portion 6 are continuously formed. In the two-piece bottle can 1, a neck portion 3 is formed at a predetermined portion of the body portion 2, and a mouth portion 4 is formed at an end portion of the neck portion 3. Further, the two-piece bottle can 1 has a screw portion 5 for attaching a cap on the outer periphery in the vicinity of the mouth portion 4 and a curled portion 7 on the top surface portion 8.

  And in patent document 1, 3004 alloy prescribed | regulated to JISH4000 which adjusted each content of Fe, Si, Mn, and Mg as an aluminum alloy plate used for such a 2 piece bottle can, or 3104 alloy etc. This is used for casting, homogenization heat treatment, hot rolling treatment, cold rolling treatment, annealing as necessary, and then cold rolling to produce a predetermined aluminum alloy sheet It has been proposed to do.

JP 2002-256366 A (paragraph numbers 0013 and 0030, FIG. 1)

  However, depending on the contents of the bottle can, in order to prevent leakage after the cap is tightened, it is required to increase the capping load at the time of capping. When trying to expand the application to such contents, it is necessary to increase the buckling strength against the axial load applied to the neck portion and the body portion from 1500 N or more to 1960 N or more. In order to produce a bottle can that can withstand a high stoppering load, a material with higher strength is required. However, in the conventional aluminum alloy sheet, the higher the strength, the more the wrinkle during neck forming and the curl forming There is a problem that curl cracks occur in the cans, making cans themselves difficult, and they have not been put into practical use. In order to increase the strength, it is conceivable to increase the thickness of the aluminum alloy plate. However, in a bottle can, there is a high demand for reducing the thickness and weight in order to reduce the amount of metal used per can.

  Therefore, the present invention was devised to solve such a problem, and the problem is that the formability when manufacturing a bottle can is excellent and the current thickness / weight is not increased. Another object of the present invention is to provide an aluminum alloy plate for a bottle can having a sufficient can body strength (buckling strength).

In order to solve the above-mentioned problems, the aluminum alloy plate for a bottle can according to the present invention has Cu of 0.10 to 0.40 mass%, Mg of 1.38 to 2.00 mass%, and Mn of 0.50 to 0.50. 1.00% by mass, 0.40 to 0.80% by mass of Fe, 0.10 to 0.40% by mass of Si, and the balance is composed of Al and unavoidable impurities, of Mn, Mg and Fe The aluminum alloy plate whose content satisfies the relationship of 5.450 <{5.66 × Mn (mass%) + 0.667 × Mg (mass%) + 2.17 × Fe (mass%)} <7.550 The elongation of the aluminum alloy plate is 5.0 to 8.0%, the average aspect ratio of the crystal grains is 3.0 or more, and the aluminum alloy plate is heat treated at 210 ° C. for 10 minutes. Later 0.2% proof stress exceeds 270N / mm ² and 290N / Mm ² or less, and a blank having a diameter of 66 mm is punched from the aluminum alloy plate, and cupping is performed on the blank to produce a drawn cup having a cup diameter of 40 mm, which is calculated from the cup height of the drawn cup The ear rate is -2 to + 3.5%.

  According to such a configuration, by restricting each content of Cu, Mg, Mn, Fe, and Si to a predetermined range, the 0.2% proof stress after the heat treatment becomes an appropriate range, and the can body strength is improved. At the same time, neck formability and curl formability are improved. Moreover, the ear | edge rate in the case of can shaping | molding becomes an appropriate range, and a can dimension is stabilized. When the contents of Mn, Mg, and Fe satisfy a predetermined relationship, an intermetallic compound having a predetermined size and number density is formed on the aluminum alloy plate, and neck formability and curl formability are improved. Further, by restricting the elongation of the alloy plate to a predetermined range, neck formability and curl formability are improved. Furthermore, by controlling the average aspect ratio of the crystal grains of the alloy plate within a predetermined range, the crystal grains have a structure elongated in the rolling direction, and the ear ratio when the alloy plate is formed by DI is in an appropriate range.

  According to the aluminum alloy plate for a bottle can of the present invention, excellent formability can be achieved without increasing the current plate thickness / weight, and the manufactured bottle can has sufficient can dimensions, can body strength (seat Bend strength).

It is a perspective view which shows a 2 piece bottle can typically. It is explanatory drawing which shows typically the manufacturing method of the 2 piece bottle can of FIG.

  Hereinafter, embodiments of the present invention will be described in detail. The present inventors have advanced the development of a material suitable for manufacturing a bottle can that can withstand a cap-capping load more than the conventional one, even if the bottle can has a current can wall thickness or a thinner can wall thickness. . As a result, the required can can be obtained by combining the alloy components exceeding the component range of JIS stipulated 3104 alloy or 3004 alloy, which has been conventionally adopted, with appropriate homogenization heat treatment conditions, hot rolling conditions, and cold rolling conditions. The present inventors have found an aluminum alloy plate for bottle cans (hereinafter referred to as an aluminum alloy plate) that satisfies the strength, can size, and formability at the same time.

[Aluminum alloy plate]
In the aluminum alloy plate according to the present invention, Cu is 0.10 to 0.40 mass%, Mg is 1.30 to 2.00 mass% (preferably 1.38 to 2.00 mass%), and Mn is 0.00. 50 to 1.00% by mass, Fe is 0.40 to 0.80% by mass, Si is 0.10 to 0.40% by mass, the balance is composed of Al and inevitable impurities, and the Mn, Mg and Aluminum alloy satisfying a relationship of Fe content of 5.450 <{5.66 × Mn (mass%) + 0.667 × Mg (mass%) + 2.17 × Fe (mass%)} <7.550 The aluminum alloy plate has an elongation of 5.0 to 8.0% or less, an average aspect ratio of crystal grains of 3.0 or more, and 0.2% after heat treatment of the aluminum alloy plate strength is there in the more than 290N / mm ² or less 270N / mm ² The ear of an aluminum alloy plate is -2 + 3.5%.

The reason why the respective components contained in the aluminum alloy plate and the material properties (elongation, 0.2% proof stress after heat treatment with an average aspect ratio of crystal grains, and ear ratio) are limited numerically will be described below.
(Cu content: 0.10 to 0.40 mass%)
Cu is an element that contributes to the material strength of the aluminum alloy plate. Further, the buckling strength of the bottle can depends on the material strength of the aluminum alloy plate. And in the manufacturing process of the bottle can described later, 0.2% proof stress after the heat treatment before the neck forming, that is, 210 ° C. for 10 minutes corresponding to the heat treatment when the inner surface printing / baking treatment is performed on the DI can. An important indicator is the 0.2% yield strength of the aluminum alloy sheet after the heat treatment is applied to the aluminum alloy sheet.

  If the Cu content is less than 0.10% by mass, sufficient material strength (0.2% yield strength after heat treatment) cannot be obtained, and the can strength of the bottle can is insufficient (neck portion against the axial load, can body) The buckling strength of the part is insufficient). If the Cu content exceeds 0.40 mass%, the material strength (0.2% proof stress after heat treatment) becomes too high, and in the bottle can manufacturing process described later, wrinkles are generated during neck molding and curl molding. The occurrence rate of defective cans due to the occurrence of cracks at the time increases, making it unsuitable for practical use.

(Mg content: 1.30 to 2.00% by mass, preferably 1.38 to 2.00% by mass)
Mg is an element that contributes to the material strength of the aluminum alloy plate. If the Mg content is less than 1.30% by mass, sufficient material strength (0.2% yield strength after heat treatment) cannot be obtained, and the can strength of the bottle can is insufficient. If the Mg content exceeds 2.00% by mass, the work hardening increases and the material strength (0.2% proof stress after heat treatment) becomes too high. The occurrence rate of defective cans due to the occurrence of wrinkles and cracks during curl molding increases, making it unsuitable for practical use.

(Mn content: 0.50 to 1.00% by mass)
Mn is an element that contributes to the material strength of the aluminum alloy plate. If the Mn content is less than 0.50% by mass, sufficient material strength (0.2% yield strength after heat treatment) cannot be obtained, and the can strength of the bottle can is insufficient. If the Mn content exceeds 1.00% by mass, the material strength (0.2% proof stress after heat treatment) becomes too high, and in the bottle can manufacturing process described later, the neck portion after printing / baking treatment Due to lack of ductility, the rate of occurrence of defective cans due to the occurrence of wrinkles during neck molding and cracks during curl molding increases, making it unsuitable for practical use.

(Fe content: 0.40 to 0.80 mass%)
When the Fe content is less than 0.40% by mass, in the bottle can manufacturing process described later, the 0-180 ° ear increases during DI molding, making it difficult to obtain a predetermined can size. When the Fe content exceeds 0.80% by mass, the size and number density of the Al—Mn—Fe—Si intermetallic compound increase, and in the bottle can manufacturing process described later, cracks are generated during curl molding. The incidence of defective cans increases, making them unsuitable for practical use.

(Si content: 0.10 to 0.40 mass%)
When the Si content is less than 0.10% by mass, 45 ° ears increase during DI molding in the bottle can manufacturing process described later. If the Si content exceeds 0.40% by mass, the texture of the hot rolled alloy will vary in the manufacturing process of the aluminum alloy sheet described later. When a bottle can is manufactured with such an aluminum alloy plate, the variation in the ear rate increases during DI molding. In either case, it is difficult to obtain a predetermined can size.

(Inevitable impurities)
In the present invention, as unavoidable impurities, Cr is 0.1 mass% or less, Zn is 0.5 mass% or less, Ti is 0.1 mass% or less, Zr is 0.1 mass% or less, B is Even if contained in an amount of 0.1% by mass or less, the effect of the present invention is not hindered, and the inclusion of such inevitable impurities is allowed.

(5.450 <{5.66 × Mn (mass%) + 0.667 × Mg (mass%) + 2.17 × Fe (mass%)} <7.550)
In the bottle can manufacturing process, the occurrence of streak defects at the neck is affected by the size and number density of the Al—Mn—Fe—Si intermetallic compound. The size and number density of the intermetallic compound depend on the contents of Mn, Mg, and Fe, and the degree of influence increases in the order of Mn, Fe, and Mg. When Mn, Mg, and Fe satisfy the above relationship, the size and number density of the intermetallic compound are in a suitable range, generation of streak-like defects in the neck portion is suppressed, and curl cracking is also prevented.

  If {5.66 × Mn + 0.667 × Mg + 2.17 × Fe} is 5.450 or less, the formation of intermetallic compounds is not sufficient, and in the bottle can manufacturing process described later, seizure during DI molding occurs. As a result, not only the trunk part but also the neck part has noticeable streak-like defects. When {5.66 × Mn + 0.667 × Mg + 2.17 × Fe} is 7.550 or more, the intermetallic compound is coarsened, and this coarse intermetallic compound is dropped at the time of DI molding. This causes streak-like defects. This streak-like defect causes a crack during curl molding.

(Elongation: 5.0-8.0%)
If the elongation is less than 5.0%, wrinkles at the time of cup molding remain as wrinkles after neck molding in the bottle can manufacturing process described later, and the incidence of defective cans due to increased cracking at the time of curl molding increases. Not suitable for practical use. If the elongation exceeds 8.0%, in the bottle can manufacturing process described later, the work hardening at the time of neck molding is large, the neck portion strength becomes excessive, and the rate of occurrence of defective cans due to increased cracking at the time of curl molding Becomes higher and is not suitable for practical use. In addition, in the manufacturing process of the aluminum alloy plate described later, it is possible to obtain the elongation in the above range by controlling the coiling temperature in the cold rolling to a predetermined range.

(Average aspect ratio of crystal grains: 3.0 or more)
The aspect ratio of the crystal grains is defined by the ratio (L / ST) of the crystal grain size (L) in the rolling direction and the crystal grain size (ST) in the plate width direction of the aluminum alloy plate, and the average aspect ratio is the average value. When the ratio is less than 3.0, in the bottle can manufacturing process described later, 0-180 ° ears increase during DI molding, making it difficult to obtain a predetermined can size. In addition, in the manufacturing process of the aluminum alloy plate described later, the average aspect ratio in the above range can be obtained by controlling the cold working rate within a predetermined range.

(0.2% proof stress after the heat treatment: exceed 270N / mm ² 290N / mm ² or less)
The 0.2% yield strength of the aluminum alloy plate after heat treatment at 210 ° C. for 10 minutes affects the can strength (buckling strength) of the bottle can. If the 0.2% yield strength after heat treatment is 270 N / mm ² or less, the can strength (buckling strength) is insufficient. If the 0.2% proof stress after heat treatment exceeds 290 N / mm ² , the rate of occurrence of defective cans increases due to the occurrence of wrinkles during neck molding and cracks during curl molding, making it unsuitable for practical use. Therefore, in the present invention, the 0.2% proof stress of the aluminum alloy sheet after heat treatment at 210 ° C. for 10 minutes is required to be more than 270 N / mm ² and 290 N / mm ² or less. In addition, by controlling the contents of Cu, Mn, and Mg contained in the aluminum alloy within a predetermined range, it is possible to obtain 0.2% proof stress (after heat treatment) in the above range.

(Ear rate: -2 to + 3.5%)
The size of the ear rate corresponds well with the can size accuracy (mouth size accuracy) of the bottle can, and in order to obtain a predetermined can size, the ear rate is required to be in the range of -2 to + 3.5%. . When the ear rate is within the above range, the can dimension accuracy is good, and when the ear rate is outside the range, the can size accuracy is poor. In addition, the content of Fe and Si contained in the aluminum alloy, the homogenization heat treatment temperature in the production of the aluminum alloy sheet described later, the winding temperature during hot rolling, and the cold working rate during cold rolling are controlled. Thus, it is possible to obtain an ear rate in the above range.

  The method for manufacturing the aluminum alloy plate includes the following first to fourth steps. In the first step, Cu is 0.10 to 0.40 mass%, Mg is 1.30 to 2.00 mass% (preferably 1.38 to 2.00 mass%), and Mn is 0.50 to 1. 00 mass%, Fe 0.40 to 0.80 mass%, Si 0.10 to 0.40 mass%, the balance is composed of Al and unavoidable impurities, the content of Mn, Mg and Fe Of aluminum alloy satisfying the relationship of 5.450 <{5.66 × Mn (mass%) + 0.667 × Mg (mass%) + 2.17 × Fe (mass%)} <7.550 To produce an ingot. In the second step, the ingot is subjected to homogenization heat treatment. And the said homogenization heat processing is performed on the temperature conditions of 570-620 degreeC. In the third step, the ingot homogenized by the second step is hot-rolled to produce a rolled plate. And the said hot rolling is performed by coiling temperature 300 degreeC or more. In the fourth step, the rolled plate is cold-rolled to produce an aluminum alloy plate. The cold rolling is performed at a cold working rate of 82 to 90% and a winding temperature of 130 to 180 ° C.

  Below, each condition prescribed | regulated in the said manufacturing method is demonstrated. In addition, about the numerical limitation reason of the component of an aluminum alloy, since it is the same as the above-mentioned aluminum alloy plate for bottle cans, it abbreviate | omits.

(Temperature conditions for homogenization heat treatment: 570-620 ° C.)
If the homogenization heat treatment temperature is less than 570 ° C., it causes variations in texture during hot rolling in the next step, and in the bottle can manufacturing process described later, variations in the ear rate during DI molding increase, and the predetermined can It becomes difficult to obtain the dimensions. In addition, the remaining of the non-recrystallized structure causes wrinkles at the time of neck forming, and further curl cracks. When the homogenization heat treatment temperature exceeds 620 ° C., the ingot surface is burned, and the alloy plate itself cannot be manufactured.

(Hot rolling coiling temperature: 300 ° C or higher)
If the coiling temperature for hot rolling is less than 300 ° C., it causes variation in texture during hot rolling in the next step, and in the manufacturing process of a bottle can described later, variation in ear ratio during DI molding increases. It becomes difficult to obtain a predetermined can size. In addition, the remaining of the non-recrystallized structure causes wrinkles at the time of neck forming, and further curl cracks.

(Cold rolling cold working rate: 82-90%)
If the cold working rate is less than 82%, in the bottle can manufacturing process described later, 0-180 ° ears increase and it becomes difficult to obtain a predetermined can size. When the cold working rate exceeds 90%, the 45 ° ear increases, and it becomes difficult to obtain a predetermined can size. By controlling the cold working rate within the above range, the average aspect ratio of the crystal grains of the aluminum alloy plate can be set within a predetermined range.

(Cold rolling coiling temperature: 130-180 ° C.)
When the coiling temperature for cold rolling is less than 130 ° C., sufficient ductility cannot be obtained in the aluminum alloy sheet, and in the bottle can manufacturing process described later, wrinkles at the time of cup molding remain as wrinkles after neck molding, The incidence of defective cans due to increased cracking during molding increases, making it unsuitable for practical use. When the winding temperature exceeds 180 ° C., in the bottle can manufacturing process described later, work hardening at the time of neck molding is large, the strength of the neck is excessive, and defective cans are generated due to increased cracking at the time of curl molding. The rate will be high and not suitable for practical use. In addition, it becomes possible to make elongation of an aluminum alloy plate into a predetermined range by controlling winding temperature in the said range.

  Here, the casting in the first step is preferably a DC casting process (Direct-chill Casting), and is necessary between the hot rolling in the third step and the cold rolling in the fourth step. Depending on, a rough annealing step of annealing may be added. Further, the cold rolling of the fourth step may be performed by performing an intermediate annealing step of performing cold rolling a plurality of times and performing annealing as necessary during the cold rolling. Therefore, the cold work rate means the total cold work rate.

  The aluminum alloy plate according to the present invention described above has a two-piece bottle can 1 in which a body portion 2 and a bottom portion 6 are integrally formed as shown in FIG. 1 and a body portion and a bottom portion which are not shown, but are different from each other. It is a material suitably used for a three-piece bottle can formed of a member.

[Manufacturing method of bottle can (manufacturing process)]
When the aluminum alloy plate according to the present invention is applied to a two-piece bottle can 1 as shown in FIG. 1, as shown in FIG. 2, the aluminum alloy plate A made of the aluminum alloy plate according to the present invention is used. Cupping and DI molding are performed to manufacture a DI can having a body portion 2 and a bottom portion 6. Next, the body part end 2a of the DI can (body part 2) is trimmed, cleaned (not shown), printed and baked (heat treatment at 210 ° C. for 10 minutes), and then applied to the DI can (body part 2). Necking is performed by die neck processing or the like to form the neck portion 3, and the opening portion is used as the mouth portion 4. Thereafter, the outer periphery in the vicinity of the mouth portion 4 is formed with a screw to form a screw portion 5 for attaching a screw cap, and the top surface portion 8 is subjected to curl forming to form a curled portion 7, whereby a two-piece bottle can 1 can be manufactured.

  In addition, the aluminum alloy plate A has a resin film such as PET on the surface of the aluminum alloy plate for bottle can according to the present invention in order to prevent elution of aluminum and the like from the inner surface of the two-piece bottle can 1 to be manufactured. A laminate may be used.

Examples according to the present invention will be specifically described below.
In addition, what satisfy | filled the required condition of this invention was set as Examples 1-6, and the thing which does not satisfy the required condition of this invention was set as Comparative Examples 1-18.

  First, an aluminum alloy having chemical components as shown in Table 1 was melted and cast, and this ingot was subjected to a homogenization heat treatment at a homogenization heat treatment temperature shown in Table 1 for 4 hours. Subsequently, hot rough rolling and hot finish rolling were sequentially performed to produce a hot rolled sheet, and then wound at a winding temperature as shown in Table 1 to obtain a hot coil. The hot coil was cold-rolled at the cold working rate shown in Table 1 and wound up at the winding temperature shown in Table 1, and an aluminum alloy plate having a plate thickness of 0.360 mm (Examples 1 to 6, Comparative Example) 1-18) were produced. Note that the plate thickness of 0.360 mm is a thin plate thickness because the conventional plate thickness is 0.400 mm.

  And about the aluminum alloy plate of said Examples 1-6 and Comparative Examples 1-18, the average aspect-ratio of crystal grain, elongation, and 0.2% yield strength after heat processing were calculated | required with the following measuring methods. The results are shown in Table 1. The underline in Table 1 indicates that the necessary conditions of the present invention are not satisfied.

(Average aspect ratio)
On the surface of the aluminum alloy plate, the crystal grain size (L) in the rolling direction and the crystal grain size (ST) in the plate width direction were determined, and the aspect ratio = (L / ST) was calculated. The same measurement was repeated by changing the measurement location (5 locations), and the average value was defined as the average aspect ratio.

(Elongation, 0.2% proof stress after heat treatment)
A JIS No. 5 test piece was collected from the aluminum alloy plate in the rolling direction, and a tensile test was performed using this test piece in accordance with JIS Z2241, and the elongation was measured. In addition, a JIS No. 5 test piece was collected from an aluminum alloy plate subjected to heat treatment (baking treatment) at 210 ° C. for 10 minutes, and a tensile test was similarly performed using this test piece, and 0.2% yield strength after heat treatment was obtained. Was measured.

Next, the ear rate was adopted as an index of the can size accuracy of the bottle can manufactured from the aluminum alloy plate, and the ear rate was calculated by the following method.
(Ear rate, can dimension accuracy)
A blank having an outer diameter of 66 mm was punched from the aluminum alloy plate, and cupping was performed on the blank to produce a drawn cup having a cup diameter of 40 mm. The cup height of this squeezed cup was measured, and the ear rate was measured based on the following formula (1). In the following formula (1), hX represents the height of the squeezing cup. The suffix “X” of h indicates the measurement position of the cup height, and means the position that forms an angle of X ° with the rolling direction of the aluminum alloy sheet. The size of the ear rate corresponds well with the can size accuracy (mouth size accuracy) of the bottle can, and in order to obtain a predetermined can size, the ear rate may be in the range of -2 to + 3.5%. Desired. When the ear rate was within the above range, the can dimension accuracy was good “◯”, and when the ear rate was outside the range, the can size accuracy was poor “×”. The results are shown in Table 2.

  Ear rate (%) = [{(h45 + h135 + h225 + h315) − (h0 + h90 + h180 + h270)} / {1/2 (h45 + h135 + h225 + h315 + h0 + h90 + h180 + h270)}] × 100 (1)

  Moreover, as shown in FIG. 2, the 2 piece bottle can 1 was manufactured in the following procedures using the said aluminum alloy plate. First, a blank having an outer diameter of 160 mm was punched from the aluminum alloy plate A, and cupping was performed on the blank to obtain a drawn cup having a cup diameter of 94 mm. DI molding was performed on the drawn cup to obtain a DI can having an inner diameter of the body portion 2 of 66 mm. After trimming the body end 2a of this DI can and baking treatment (heat treatment) at 210 ° C. for 10 minutes, the neck 4 is further necked by the die neck method until the inner diameter of the mouth 4 becomes 40 mm. Got. A screw part 5 and a curl part 7 are formed on the neck part 3 of this necking product by screw / curl molding to obtain a two-piece bottle can 1.

The neck moldability, curl moldability, and buckling strength were evaluated by the following methods using the necking product and the two-piece bottle can. The results are shown in Table 2.
(Neck formability)
In the necking product (number of samples = 20), the neck formability was evaluated by confirming the occurrence of wrinkle or streak defects. A case where no wrinkle or streak-like defects were found was rated as “good”, and a case where wrinkle-like or streak-like defects were found was rated as “poor”.

(Curl formability)
In the two-piece bottle can (number of samples = 20), the curl formability was evaluated by checking the presence or absence of cracks in the curled part. Those where no cracks were observed were evaluated as “good”, and those where cracks were observed even in one can were evaluated as “bad”.

(Buckling strength)
A compressive load in the axial direction was applied to the two-piece bottle can (number of samples = 10), the load when the neck portion or the body portion buckled was measured, and the average value was defined as the buckling strength. As for this buckling strength, those with 1960 N or more were judged as “good”, and those with less than 1960 N were judged as “poor”.

  As shown in Tables 1 and 2, in Examples 1 to 6 that satisfy the requirements of the present invention, even if the plate thickness is reduced, the can size accuracy, neck formability, curl formability and buckling of the bottle can All evaluation items of strength were good.

  However, in Comparative Examples 1 to 18 that do not satisfy the requirements of the present invention, when the plate thickness is reduced, at least one item among the can dimensional accuracy, neck formability, curl formability, and buckling strength is performed. The results were inferior to the examples.

That is, in Comparative Example 1, since Cu is less than the lower limit of the present invention, the 0.2% yield strength after heat treatment is less than 270 N / mm ² , and the buckling strength is inferior. In Comparative Example 2, since Cu exceeds the upper limit of the present invention, the 0.2% proof stress after heat treatment exceeds 290 N / mm ² , and the neck formability and curl formability are inferior.

In Comparative Example 3, since Mg was less than the lower limit of the present invention, the 0.2% yield strength after heat treatment was less than 270 N / mm ² and the buckling strength was poor. In Comparative Example 4, since Mg exceeds the upper limit of the present invention, the 0.2% proof stress after heat treatment exceeds 290 N / mm ² and {5.66 × Mn (mass%) + 0.667 × Mg ( (Mass%) + 2.17 × Fe (mass%)} also exceeds the upper limit of the present invention, so the neck moldability and curl moldability were poor.

In Comparative Example 5, since Mn is less than the lower limit of the present invention, the 0.2% proof stress after heat treatment is less than 270 N / mm ² and {5.66 × Mn (mass%) + 0.667 × Mg Since (mass%) + 2.17 × Fe (mass%)} is also less than the lower limit of the present invention, the neck moldability, curl moldability, and buckling strength were poor. In Comparative Example 6, Mn, {5.66 × Mn (mass%) + 0.667 × Mg (mass%) + 2.17 × Fe (mass%)} exceeds the upper limit of the present invention. The curl formability was poor.

  In Comparative Example 7, since Fe was less than the lower limit of the present invention, the ear rate was out of the range, and the can dimensional accuracy was inferior. In Comparative Example 8, since Fe, {5.66 × Mn (mass%) + 0.667 × Mg (mass%) + 2.17 × Fe (mass%)} exceeds the upper limit of the present invention, neck moldability, The curl formability was poor.

  In Comparative Example 9, since Si was less than the lower limit of the present invention, the ear rate was out of range, and the can dimension accuracy was inferior. In Comparative Example 10, since Si exceeded the upper limit of the present invention, the ear rate was out of the range, and the can dimensional accuracy was inferior.

  In Comparative Example 11, {5.66 × Mn (mass%) + 0.667 × Mg (mass%) + 2.17 × Fe (mass%)} is less than the lower limit of the present invention. The moldability was inferior. In Comparative Example 12, {5.66 × Mn (mass%) + 0.667 × Mg (mass%) + 2.17 × Fe (mass%)} exceeds the upper limit of the present invention. The property was inferior.

In Comparative Examples 13 to 18, the chemical components satisfy the range regulated in the present invention.
However, since the winding temperature at the time of cold rolling was less than the lower limit value of the present invention in Comparative Example 13, the elongation was less than the lower limit value of the present invention, and the neck formability and curl formability were inferior. In Comparative Example 14, the coiling temperature during cold rolling exceeded the upper limit of the present invention, so the elongation exceeded the upper limit of the present invention and the curl formability was poor.

  In Comparative Example 15, since the cold working rate during cold rolling is less than the lower limit of the present invention, the average aspect ratio of the crystal grains is less than the lower limit of the present invention, the ear ratio is out of the range, and the can dimension accuracy Was inferior. In Comparative Example 16, since the cold working rate during cold rolling exceeded the upper limit of the present invention, the ear rate was out of the range, and the can dimension accuracy was inferior.

  In Comparative Example 17, since the homogenization heat treatment temperature was less than the lower limit of the present invention, the ear rate was out of the range, and the can dimensional accuracy, neck formability and curl formability were inferior. In Comparative Example 18, the coiling temperature at the time of hot rolling was less than the lower limit of the present invention, so the ear ratio was out of range, and the can dimension accuracy, neck formability and curl formability were inferior.

1 2 piece bottle can 2 body part 3 neck part 4 mouth part 5 screw part 6 bottom part 7 curl part 8 top surface part

Claims (1)

Cu is 0.10 to 0.40 mass%, Mg is 1.38 to 2.00 mass%, Mn is 0.50 to 1.00 mass%, Fe is 0.40 to 0.80 mass%, Si is 0.10 to 0.40% by mass, the balance is composed of Al and inevitable impurities, and the content of Mn, Mg and Fe is 5.450 <{5.66 × Mn (% by mass) +0. 667 × Mg (mass%) + 2.17 × Fe (mass%)} <7.550 satisfying the relationship:
The elongation of the aluminum alloy plate is 5.0 to 8.0%, and the average aspect ratio of the crystal grains is 3.0 or more,
The 0.2% proof stress after the heat treatment of 10 minutes at 210 ° C. of the aluminum alloy plate is at a greater than 290 N / mm ² or less 270N / mm ^2,
When a blank having a diameter of 66 mm was punched from the aluminum alloy plate and cupping was performed on the blank to produce a drawn cup having a cup diameter of 40 mm, the ear ratio calculated from the cup height of the drawn cup was -2 to + 3.5% aluminum alloy plate for bottle cans.

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