JP2009001858A - Aluminum alloy sheet for can body having excellent circulation pinhole resistance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum alloy sheet for a can body having excellent circulation pinhole resistance in which the generation of pinholes can be prevented without increasing production cost. <P>SOLUTION: The aluminum alloy sheet for the can body having excellent circulation pinhole resistance has a composition comprising, by mass, 0.15 to 0.5% Si, 0.3 to 0.6% Fe, 0.15 to 0.5% Cu, 0.7 to 1.2% Mn and 0.8 to 2.0% Mg, and the balance Al with inevitable impurities, the aluminum alloy sheet is characterized in that the thickness is 0.250 to <0.275 mm, the stock proof stress after baking is ≥265 MPa, the number of intermetallic compounds with an equivalent circle diameter is ≥10 μm of ≤3 pieces/mm<SP>2</SP>, the tensile strength of the barrel part in a can body after can making by DI working and coating/baking is >330 to 380 MPa, and the elongation of the barrel part is ≥4%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an aluminum alloy plate for a can body that is excellent in resistance to distribution pinholes.

  In general, the can body includes a can with a can lid wound around its open end and a bottle can with a cap screwed into its open end, filled with beverages and other contents, and distributed in the market. is doing. Such a can body is conventionally formed by DI (Drawing & Ironing) processing performed by drawing and ironing a plate material made of an Al alloy such as JIS3004 (AA3004) or JIS3104 (AA3104). Such a ironing process is usually performed in three times to produce a can body. And the trunk | drum of such a can body is formed with the thickness in the thinnest part being about 0.106 mm.

Conventionally, in the distribution process of the can body as described above, for example, the sharp body contacts or collides with the body portion of the can body, the body portions of adjacent can bodies collide, or between the cans and the cans. Due to rubbing in a state where foreign matter is sandwiched, there is a problem that breakage of a minute hole or the like called a distribution pinhole occurs and the contents leak.
As an effective means for solving the problem of such a distribution pinhole, it is conceivable to increase the thickness of the trunk, but in this case, the amount of can body material increases, so that the manufacturing cost is increased. There was a problem of increasing.

In order to solve such a problem, for example, it is made of an aluminum alloy material containing, by mass%, Mn: 0.8 to 1.5% and Mg: 0.8 to 1.3%, and the elongation at break is 6 to A can body of 10% has been proposed (for example, Patent Document 1).
JP-A-8-199273

According to the can body described in Patent Document 1, the component composition of the can body material is as described above, and the elongation at break after canning is configured as 6 to 10%, thereby reducing the thickness of the material. Even so, it is said that the piercing strength of the trunk portion is improved.
However, in the configuration of the can body material described in Patent Document 1, when the thickness of the material is reduced, the bottom portion of the can body is also thinned, so that the pressure resistance strength of the bottom portion may be reduced. For this reason, it is necessary to increase the strength of the raw material itself. However, if the strength of the raw material is increased, there is a problem in that the body portion is likely to be broken (cut out) during molding by ironing.

  In order to prevent the can body from being cut as described above, it is effective to increase the number of ironing processes in order to reduce the ironing rate in one ironing process. In the conventional DI processing method, ironing is normally performed three times, and there is a problem that conventional process equipment cannot be used when the number of ironing is increased.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an aluminum alloy plate for a can body that can prevent the generation of pinholes without increasing the manufacturing cost and has excellent circulation pinhole resistance. And

  As a result of intensive studies to improve the flow resistance pinhole resistance of the can body, the present inventors first limited the component composition of the material to a predetermined range, and formed a thin plate thickness of the material, and The body of the can body can be made thicker by increasing the thickness of the can body body, increasing the strength of the material, and controlling the size and distribution of intermetallic compounds after canning by DI processing and paint baking. As a result, the present invention was completed.

  That is, the present invention relates to the following.

(1) Invention of Claim 1 The thickness of a trunk | drum is 0.125 mm or more and 0.125 mm or less, the total drawing ratio at the time of manufacture is 2.0-2.7, and the total ironing rate is 50. % And less than 60% of the can body aluminum alloy plate for mass%, Si: 0.15-0.5%, Fe: 0.3-0.6%, Cu: 0.15-0.5%, Mn: 0.7-1.2%, Mg: 0.8-2.0%, the balance is made of Al containing inevitable impurities, and the plate thickness is 0.250 mm It is less than 0.275 mm, the material yield strength after baking is 265 MPa or more, the number of intermetallic compounds having an equivalent circle diameter of 10 μm or more is 3 / mm ² or less, and is manufactured by DI processing and paint baking. The tensile strength of the body of the can body after the can is more than 330 MPa and 380 MPa or less An aluminum alloy plate for a can body having excellent circulation pinhole resistance, characterized in that the body portion has an elongation of 4% or more.
(2) Invention of Claim 2 Furthermore, it contains 1 type or 2 types in Zn: 0.05-0.30% and Ti: 0.05-0.15% by the mass%, It is characterized by the above-mentioned. The aluminum alloy plate for can bodies having excellent flow-resistant pinhole properties according to claim 1.

According to the aluminum alloy plate for a can body excellent in flow-through pinhole resistance according to the present invention, it has the above-mentioned composition, and the tensile strength of the body portion of the can body after DI processing and paint baking can be 330 MPa. By adopting a configuration in which the elongation of the body portion is set to be over 380 MPa or less and 4% or more, the strength of the can body body portion can be improved uniformly, and pinholes are hardly generated.
Therefore, by using the aluminum alloy plate for a can body of the present invention, a can body excellent in circulation pinhole resistance can be obtained without increasing the production cost.

  Hereinafter, an embodiment of an aluminum alloy plate for a can body (hereinafter, may be abbreviated as an aluminum alloy plate for a can body) having excellent flow-resistant pinhole properties according to the present invention will be described with reference to FIG. 1 as appropriate. .

The aluminum alloy plate for a can body of the present invention is in mass%, Si: 0.15 to 0.5%, Fe: 0.3 to 0.6%, Cu: 0.15 to 0.5%, Mn: 0.7 to 1.2%, Mg: 0.8 to 2.0%, the balance is made of Al containing inevitable impurities, the plate thickness is 0.250 mm or more and less than 0.275 mm, after baking The yield strength of the material is 265 MPa or more, the number of intermetallic compounds with an equivalent circle diameter of 10 μm or more is 3 / mm ² or less, and the tensile strength of the body of the can body after canning by DI processing and paint baking The thickness is more than 330 MPa and not more than 380 MPa, and the elongation of the body portion is 4% or more.

The aluminum alloy plate for a can body of the present embodiment has a body thickness of more than 0.110 mm and not more than 0.125 mm, a total drawing ratio at the time of manufacture of 2.0 to 2.7, and a total ironing rate Is suitable for use in the production of can bodies having a ratio of 50% to less than 60%.
In addition, the aluminum alloy plate for a can body of the present invention is subjected to homogenization treatment in a temperature range of 560 ° C. to less than the melting point for the aluminum ingot, and then hot-rolled, or further cold-rolled, And / or after having formed into predetermined sheet thickness by performing intermediate annealing, the final sheet thickness (0.250 mm or more and 0.2. Less than 275 mm).

The aluminum alloy plate for a can body according to the present invention can be obtained by controlling the number of intermetallic compounds having an equivalent circle diameter of 10 μm or more to 3 pieces / mm ² or less in the can body after canning. Since the strength of the body portion is improved uniformly, pinholes are less likely to occur.

[Ingredient composition]
Hereinafter, the component composition limited in the aluminum alloy plate for can bodies of this invention is demonstrated.
In addition, content of each element described below is mass% unless otherwise specified, and includes an upper limit and a lower limit unless otherwise specified. Therefore, for example, 0.15 to 0.5% means 0.15% or more and 0.5% or less.

"Si" 0.15-0.5%
In the aluminum alloy plate for can bodies of the present invention, Si forms a compound together with Mg or the like contained at the same time, and improves the strength by solid solution hardening, precipitation hardening and dispersion hardening, and Al-Mn-Fe based metal An intermetallic compound is formed, and has the effect of preventing seizure on the die during ironing molding.
If the Si content is less than 0.15%, sufficient strength cannot be obtained, and the size of the intermetallic compound increases. Further, the desired lubrication performance cannot be exhibited, which is insufficient to prevent seizure on the die (die).
If the Si content exceeds 0.5%, the strength becomes too high, and when a can body is produced as a can body, it becomes easy to be cut out of the cylinder and the workability deteriorates.
Moreover, the intermetallic compound with Mg, Cu, and Al cannot be solutionized, the toughness is lowered, and pinholes are easily generated.
Therefore, the Si content is preferably in the range of 0.15 to 0.5%.

"Fe" 0.3-0.6%
Fe increases the precipitation amount of Al-Mn-Fe intermetallic compounds in the aluminum alloy sheet for can bodies of the present invention, and prevents the formation of fine crystals and seizure to the die during ironing processing. Has the effect of
If the Fe content is less than 0.3%, the precipitation amount of the Al—Mn—Fe intermetallic compound becomes too small, and seizure to the ironing die tends to occur.
If the Fe content exceeds 0.6%, the amount of Al—Mn—Fe intermetallic compound becomes too large, and the workability deteriorates due to a decrease in toughness, and pinholes are likely to occur.
Therefore, the Fe content is preferably in the range of 0.3 to 0.6%.

"Cu" 0.15-0.5%
Cu forms an intermetallic compound with Mg or the like in the aluminum alloy plate for a can body of the present invention, and has an effect of increasing strength by solid solution hardening, precipitation hardening, and dispersion hardening.
If the Cu content is less than 0.15%, a sufficient strength improvement effect cannot be obtained.
If the Cu content exceeds 0.5%, the strength becomes too high, and when the can body is produced as a can body, it becomes easy for the barrel to be cut. In addition, the intermetallic compound with Mg, Si, and Al cannot be in solution, and the workability deteriorates due to a decrease in toughness, and pinholes are likely to occur.
Therefore, the Cu content is preferably in the range of 0.15 to 0.5%.

"Mn" 0.7-1.2%
In the aluminum alloy plate for can bodies of the present invention, Mn forms an Al-Mn-Fe intermetallic compound, becomes a crystallization phase and a dispersed phase, exhibits a dispersion hardening action, and is used as a die during the ironing process. On the other hand, it has the effect of preventing seizure.
If the Mn content is less than 0.7%, the amount of Al—Mn—Fe intermetallic compound becomes too small to obtain sufficient curing characteristics, and seizure to the ironing mold tends to occur.
When the content of Mn exceeds 1.2%, the amount of Al—Mn—Fe intermetallic compound is excessively increased, workability is deteriorated due to a decrease in toughness, and pinholes are easily generated.
Therefore, the Mn content is preferably in the range of 0.7 to 1.2%, more preferably 1.0% or less.

"Mg" 0.8-2.0% (preferably less than 1.5%)
In the aluminum alloy plate for can bodies of the present invention, Mg has a solid solution strengthening action, enhances work hardening at the time of rolling, and exhibits dispersion hardening and precipitation hardening action by coexisting with Si and Cu. To improve.
If the Mg content is less than 0.8%, the above-described sufficient effect cannot be obtained.
If the Mg content exceeds 2.0%, the strength becomes too high, and the workability, particularly curl workability, is deteriorated, and when the can body is produced as a can body, it becomes easy to cause a barrel break.
Therefore, the Mg content is more preferably in the range of 0.8 to 2.0%, and more preferably less than 1.5%.

“Zn and Ti” Zn: 0.05 to 0.30%, Ti 0.05 to 0.15%
The aluminum alloy plate for a can body according to the present invention may further include one or two of Zn: 0.05 to 0.30% and Ti: 0.05 to 0.15% by mass as necessary. It can be set as the component composition to contain.
Zn has the effect | action which refines | miniaturizes the intermetallic compound of Mg, Si, and Cu to precipitate.
If the Zn content is less than 0.05%, the above-described sufficient effect cannot be obtained.
If the Zn content exceeds 0.30%, workability and corrosion resistance deteriorate.
Therefore, the Zn content is preferably in the range of 0.05 to 0.30%.

Ti has the effect of refining crystal grains and improving workability in the aluminum alloy plate for can bodies of the present invention.
When the Ti content is less than 0.05%, the above-described sufficient effect cannot be obtained.
If the Ti content exceeds 0.15%, a coarse compound is produced and the workability is deteriorated.
Therefore, the Ti content is preferably in the range of 0.05 to 0.15%.

[Thickness of aluminum alloy sheet for can body]
It is preferable that the plate | board thickness of the aluminum alloy plate for can bodies of this invention is the range of 0.250 mm or more and less than 0.275 mm.
When the plate thickness is less than 0.250 mm, sufficient pressure resistance strength cannot be obtained when the can is made into a can body.
On the other hand, if the plate thickness is 0.275 mm or more, the weight of the bottom of the can body becomes heavy, and the manufacturing cost increases, which is not economical.

[Material strength after baking (265 MPa or more)]
The can body after DI processing is heated to a temperature of 180 to 230 ° C. by drying after cleaning and chemical conversion treatment, or by baking treatment after external printing or internal coating. This heating generally changes the strength of the can bottom and the trunk. The strength after heating differs depending on the amount of strain during DI molding. Since the distortion at the bottom is small during DI molding, the strength after heating is almost equal to the strength after heating the aluminum alloy plate, which is a material before DI processing. For this reason, the intensity | strength after baking (heating) the aluminum alloy plate which is a raw material can be used as a standard of the intensity | strength of a bottom part. In the present invention, the heating condition for this is 210 ° C. × 10 minutes.
The material yield strength after baking of the aluminum alloy plate for can bodies of the present invention is preferably 265 MPa or more as the yield strength after baking under the above conditions.
If the material yield strength after baking under the above-mentioned conditions is less than 265 MPa, sufficient pressure strength of the can body after canning by DI processing and paint baking cannot be obtained.

[About the total ironing ratio and the total drawing ratio]
The aluminum alloy plate for a can body according to the present invention is used for manufacturing a can body having a body thickness (thickest thickness) of more than 0.110 mm and not more than 0.125 mm. Moreover, the aluminum alloy plate for can bodies of the present invention is used for producing a can body having a total ironing rate during DI processing of 50% or more and less than 60%. Here, the total ironing rate is expressed by the following equation (4).
Total ironing rate (%) = (original plate thickness T1—final can body body thinnest portion thickness T2) / original plate thickness T1 × 100 (4)
In the above formula (4), the final can body trunk thinnest part thickness T2 is a thickness without a coating film.
The aluminum alloy plate for a can body of the present invention has a material plate thickness of 0.250 mm or more and less than 0.275 mm, and the minimum ironing rate is 0.250 mm for the original plate thickness and 0.125 mm for the body thickness. 50% of the case.

Here, when the total ironing ratio is set to 60% or more, the aluminum alloy plate for can bodies of the present invention has high material strength, so that a cylinder breakage is likely to occur during ironing forming, and productivity is lowered. On the other hand, the case where the total ironing rate is lower than 50% is the case where the material plate thickness is smaller than 0.250 mm, or the case where the body portion plate thickness is larger than 0.125 mm.
When the material plate thickness is smaller than 0.250 mm, sufficient pressure resistance cannot be obtained. Further, when the body plate thickness is larger than 0.125 mm, the pinhole resistance is improved, but from the practical viewpoint, it becomes excessive strength and the amount of necessary material increases, which is not economical. Therefore, the total ironing rate needs to be 50% or more.

Moreover, the aluminum alloy plate for can bodies of the present invention is used for manufacturing a can body having a total drawing ratio of 2.0 to 2.7 during DI processing.
If the total drawing ratio is greater than 2.7, the material is likely to break during drawing when drawn in two drawing steps. On the other hand, in order to obtain a can body having a practical capacity under the constraints of the material plate thickness T1, the final can body body thinnest part thickness T2, and the total ironing rate, the total drawing ratio is set to 2.0 or more. There is a need to. For example, when a can body having a can body diameter of 66 mm and a capacity of 350 cc, which is generally used, is formed, the total drawing ratio is preferably set to 2.2 to 2.4. Further, when a can body having a can body diameter of about 66 mm and a capacity of about 500 cc is molded, the total drawing ratio is preferably set to 2.45 to 2.65.

Here, the total drawing ratio A is obtained by multiplying the cup drawing ratio B (steps of FIGS. 1A to 1B) and the redrawing ratio C (steps of FIGS. 1B to 1C). It is a value and is represented by the following formulas (1) to (3).
Cup drawing ratio B = Blank diameter D1 / Cup diameter D2 (1)
Redrawing ratio C = Cup diameter D2 / body diameter D3 (2)
Total drawing ratio A = Cup drawing ratio B × Redrawing ratio C = blank diameter D1 / body part diameter D3 (3)

[Tensile strength of can body body after canning by DI processing and paint baking]
It is preferable that the tensile strength of the body part of the can body obtained by DI processing and paint baking of the aluminum alloy plate for can bodies of the present invention is more than 330 MPa and not more than 380 MPa.
If the tensile strength of the body of the can body after making cans by DI processing and paint baking is 330 MPa or less, sufficient distribution-resistant pinhole properties cannot be obtained, and if it exceeds 380 MPa, it becomes easy to cause a cylinder breakage. Productivity decreases.
Further, the tensile strength of the can body trunk after canning by DI processing and paint baking is more preferably over 340 MPa.

[Elongation of can body after can making by DI processing and paint baking]
The elongation of the body portion of the can body obtained by DI processing and paint baking of the aluminum alloy plate for can bodies of the present invention is preferably 4% or more, and most preferably 5% or more.
The body portion immediately after DI molding has low elongation and is fragile, so pinholes are likely to occur. The molded can body is dried by washing and chemical conversion treatment, and is heated by baking after the outer surface coating printing and inner surface coating, whereby the ductility is restored although the strength is lowered.
By controlling the heating conditions as described above, it is necessary to make the elongation of the body portion equal to or more than the lower limit. However, for example, when heating at a constant temperature for 10 minutes, a temperature of 180 ° C. is not sufficient. It is necessary to heat at a temperature of 190 ° C. or higher.

[Number of intermetallic compounds]
In the aluminum alloy plate for can bodies of the present invention, the number of intermetallic compounds having an equivalent circle diameter of 10 μm or more is preferably 3 / mm ² or less.
There are various methods for reducing the number of intermetallic compounds having an equivalent circle diameter of 10 μm or more to 3 pieces / mm ² or less. However, the component composition is defined within the above range, and solidification cooling is performed during the production of an aluminum ingot. A method in which the speed is set to 0.05 ° C./second or more is a method that can be most easily performed in terms of equipment and the like. More preferably, if the solidification cooling rate is 0.5 ° C./second or more, the number of intermetallic compounds having an equivalent circle diameter of 10 μm or more can be reduced to 0 / mm ^2, and flow resistance pinhole resistance can be improved. Can be increased.

Here, the solidification cooling rate at the time of producing the aluminum ingot was measured by dendrite arm spacing (DAS), which is the interval between the branches of the primary dendrite structure of the aluminum ingot, by the secondary branch method. ).
ds = 44.7 × C _α ^−0.32 (5)
In the above relational expression (5), ds is a dendrite arm spacing (μm) measured by the secondary branch method, and C _α is a solidification cooling rate (° C./second).

In addition, among the methods of setting the number of intermetallic compounds having an equivalent circle diameter of 10 μm or more to 3 / mm ² or less, there is a method of reducing the content of Fe and Mn as a method other than the above. However, when such a method is used, the number of intermetallic compounds having an equivalent circle diameter of less than 10 μm also decreases. An intermetallic compound having an equivalent circle diameter of 5 μm or more and less than 10 μm is useful for preventing seizure from occurring on the die during ironing, but when the Fe and Mn contents are low, Since the number of intermetallic compounds in the range decreases, seizure to the ironing mold is likely to occur. The present inventors have intensively studied, prescribed the component composition as described above, and seized the die during the ironing process by the method of setting the solidification cooling rate during the production of the aluminum ingot to the above range. The number of intermetallic compounds having an equivalent circle diameter of 10 μm or more is set to 3 pieces / mm ² or less without excessively reducing the number of intermetallic compounds having an equivalent circle diameter of 5 μm or more and less than 10 μm, which is useful for preventing I found that I can do it.

In the present invention, by controlling the number of intermetallic compounds having an equivalent circle diameter of 10 μm or more to be 3 pieces / mm ² or less, the strength of the can body body portion is improved uniformly, so that pinholes are hardly generated. Become.
When the number of intermetallic compounds with an equivalent circle diameter of 10 μm or more exceeds 3 pieces / mm ² , the effect is small when the plate thickness is thick, but when the body is molded into a can body with a thin barrel by DI processing The strength of the body portion of the can after the can is made by paint baking is lowered, and pinholes are easily generated.

The present inventors conducted diligent research to improve the piercing strength of the can body body after canning by DI processing and paint baking, and found that the number of intermetallic compounds having an equivalent circle diameter of 10 μm or more and the flow-resistant pin It has been found that there is a correlation with the Hall property. That is, when the number of intermetallic compounds having an equivalent circle diameter of 10 μm or more increases, the flow resistant pinhole performance decreases. In a process where a sharp body comes into contact with or collides with the body of the can body, which is a typical form of distribution pinholes, and breaks such as minute holes occur, the can body body and the sharp body contact or collide with each other. Stress concentration occurs at the site. At that time, if an intermetallic compound exists on the contact surface between the can body body and the sharpened body, the intermetallic compound does not plastically deform at the stress at which the aluminum matrix phase starts plastic deformation, so that discontinuity of deformation occurs, and the metal High stress concentration occurs around the intermetallic compound. As a result of experiments conducted by the present inventors, when the equivalent circle diameter of the intermetallic compound existing on the contact surface is 10 μm or more, the stress concentration becomes extremely high because the influence of the discontinuity of deformation becomes large, and the part concerned From this, it became clear that cracks were easily generated. In addition, even an intermetallic compound having an equivalent circle diameter of 10 μm or more may not have a significant effect on stress concentration depending on the shape and direction of the generated stress, and this fracture phenomenon is a very stochastic phenomenon. It became clear. As a result of statistically investigating the relationship between the number of intermetallic compounds having an equivalent circle diameter of 10 μm or more and anti-circulation pinhole performance, the present inventors have found that the number of intermetallic compounds having an equivalent circle diameter of 10 μm or more is three. / Mm ² or less, it has been found that the distribution pinhole resistance can be improved extremely effectively.
The aluminum alloy plate for a can body according to the present invention has an excellent effect that pinholes hardly occur because the strength of the can body body portion is uniformly improved by the above-described configuration.

[Can manufacturing process by DI processing]
Hereinafter, an example of a process for obtaining a can body 10 by performing DI processing on an aluminum alloy plate for a can body to produce a can body 10 will be described with reference to FIG.

First, as shown in FIG. 1 (a), a can body aluminum alloy plate is punched to obtain a disk-shaped plate member having a diameter of 149 mm.
Next, the disk-shaped plate member is drawn to form a cup-shaped can body having a height in the axial direction of 42 mm and an outer diameter of 88.2 mm as shown in FIG. Here, the disc-shaped plate material has a thickness of 0.250 mm or more and less than 0.275 mm.

Next, the cup-shaped can body shown in FIG. 1B is redrawn to obtain a cup-shaped can body having an outer diameter of 66 mm as shown in FIG. Here, the ratio between D1 and D3 is set to 2.0 to 2.7, and in the illustrated example, 149/66 = 2.26.
Next, ironing is performed so that the total ironing rate is 50% or more and less than 60%, thereby forming a bottomed cylindrical can body as shown in FIG. The opening end portion of the bottomed cylindrical body has an uneven shape that undulates in the direction of the can axis.

  Next, the open end of the bottomed cylindrical body shown in FIG. 1 (d) is cut so that the size in the can axis direction, that is, the height is equal to about 123.5 mm over the entire circumference. A can body 10 having a circular cross section having a body 11 and a bottom 12 having a diameter of 65 mm or more and 67 mm or less is formed. In this example, the bottom portion 12 includes a dome portion (not shown) that is recessed toward the inside of the trunk portion 11 in the can axis direction, and the outer peripheral edge portion of the dome portion faces the outside of the trunk portion 11 in the can axis direction. It is an annular projection (not shown) that protrudes. The top portion of the annular convex portion in the can axis direction serves as a grounding portion in contact with the grounding surface when the can body 10 is disposed on the grounding surface so that the can body 10 is in an upright posture.

As described above, according to the aluminum alloy sheet for can bodies having excellent flow-resistant pinhole properties according to the present invention, the number of intermetallic compounds having the above component composition and having an equivalent circle diameter of 10 μm or more is 3 / and mm ^{2 or} less, also, by the tensile strength of the barrel portion of the can body after forming a can by DI processing and baking is less 330MPa ultra 380 MPa, a structure in which elongation of the body portion is 4% or more The strength of the can body body can be improved uniformly, and pinholes are less likely to occur.

Moreover, by increasing the material strength, the strength of the can body barrel after canning by DI processing and paint baking can be increased to a tensile strength of more than 330 MPa and less than 380 MPa (preferably more than 340 MPa). This improves the piercing strength and prevents the pinhole from occurring in the body portion.
Further, by reducing the thickness of the material plate, the weight of the can body can be suppressed to the same level as in the past.
Therefore, by using the aluminum alloy plate for a can body of the present invention, a can body excellent in circulation pinhole resistance can be obtained without increasing the production cost.

Hereinafter, although an Example is shown and the aluminum alloy plate for can bodies excellent in the distribution | circulation resistance pinhole property of this invention is demonstrated in more detail, this invention is not limited to this Example.
In the present Example, the aluminum alloy plate for can bodies of each test example was produced in the following steps under the component composition and production conditions shown in Table 1 below, and each item described below was evaluated.

[Production process of aluminum alloy plate for can body]
An aluminum alloy containing the components shown in Table 1 below was melted, this molten metal was degassed and inclusions removed by conventional methods, and cast into a slab by semi-continuous casting. At this time, the casting speed and the amount of cooling water were appropriately adjusted, and the solidification cooling rate in the obtained slab was cut out to be a substantially constant value, whereby the solidification cooling rate was set to a numerical value as shown in Table 1 below. A sample was obtained.
Next, the slab was subjected to a soaking treatment at a temperature shown in Table 1 below, and then subjected to hot rolling. And after performing cold rolling and intermediate annealing as needed under the conditions shown in Table 1 below, the final cold rolling was performed to obtain a plate thickness of 0.270 mm. Got.

[Evaluation items of aluminum alloy plate for can body (before can making)]
For each sample of the aluminum alloy plate for can body obtained in the above production process, by analyzing the SEM image and composition image using EPMA (Electron Probe MicroAnalyzer), and measuring the intermetallic compound containing Mn, The number of intermetallic compounds having an equivalent circle diameter of 10 μm or more was examined. At that time, the cross section parallel to the rolling direction of the alloy plate was observed and analyzed for a region within ± 100 μm from the plate thickness center after mirror polishing.
Moreover, about each sample of the aluminum alloy plate for can bodies, 0.2% yield strength YS after heating at 210 degreeC for 10 minutes (after baking) was measured.

[Can body manufacturing]
Each sample of the aluminum alloy plate for can bodies obtained in the above process was punched out to obtain a disk-shaped plate material (see FIG. 1A) having a diameter of 141 mm or 149 mm. Then, under the manufacturing conditions shown in Table 2 below, DI processing is performed on the disk-shaped plate material, and drawing and ironing are performed until the thinnest part thickness T2 of the body part becomes the thickness shown in Table 2 below. The can body (350 cc can) of each test example was obtained. In addition, the total drawing ratio and the total ironing ratio at this time were determined by the previous formulas (1) to (4) and are shown in Table 2 below. At this time, the plate material was punched out at a total of six locations in the width direction at the operator side position OPS and the opposite side position DRS of the aluminum alloy plate for the can body, and a can body was obtained by DI processing.

The outer surface coating, outer surface printing, and inner surface coating were performed on the can body of each test example DI processed as described above by the method described below.
First, an epoxy paint and an acrylic paint were used as paints, and applied to the outer surface of the can body at a film thickness of 50 mg / dm ² including printed portions such as character information. And this can body was put into oven and heat-dried at the temperature of 180 degreeC for 30 second.
Moreover, the epoxy paint was apply | coated by the film thickness of 40 mg / dm < ² > using the spray to the inner surface of the can body which gave the outer surface coating as mentioned above. And this can body was put into oven and heat-dried at the temperature of 200 degreeC for 60 second.

[Evaluation items for can body (after can making)]
About the can body formed by processing each sample of the aluminum alloy plate for can body obtained in the above process, the tensile strength TS, the elongation rate, and the piercing strength in the body portion of the can body were measured.
Tensile strength TS and elongation rate were obtained by taking a tensile test piece from the above can body and processing it into a dimensional shape having a total length of 75 mm, a parallel part length of 36 mm, a parallel part width of 10 mm, a grip part width of 15 mm, and a shoulder radius of 15 mm. And evaluated. At this time, the portion 60 mm away from the can's ground contact portion in the upper direction of the can axis was the center of the tensile test piece, and the tensile direction was the can axis direction. Then, after the coating of the outer surface and the inner surface was removed using nitric acid, a tensile test was performed to measure the tensile strength TS and the elongation.
Further, the piercing strength is a state in which an internal pressure of 0.196 MPa is applied to the can body in a room temperature (20 ° C.) atmosphere, and a portion of the can body trunk that is 60 mm away from the grounding portion upward in the can axis direction, The pressure was applied inward in the radial direction with a pressing element having a curvature radius of 2.25 mm, and the evaluation was performed by the pressing force when a hole was formed. At this time, the moving speed of the body of the presser toward the inside in the radial direction was set to 25 mm / min.

  Table 1 shows a list of composition components and manufacturing conditions for each sample of the aluminum alloy plate for can bodies, and Table 2 shows a list of manufacturing conditions for each sample of the can body and evaluation test results after canning.

  In addition, IA-CAL shown in the column of intermediate annealing in Table 1 indicates that continuous intermediate annealing was performed between cold rolling and cold rolling in the alloy plate manufacturing process, and HOT-CAL Shows that continuous annealing was performed between hot rolling and cold rolling in the alloy plate manufacturing process.

  From the above results, it became clear that the aluminum alloy sheet for can bodies having various characteristics defined in the present invention has high mechanical characteristics and excellent circulation pinhole resistance.

It is a schematic diagram for demonstrating the aluminum alloy plate for can bodies which is excellent in the distribution | circulation resistance pinhole property which concerns on this invention, and is the schematic explaining the process at the time of DI processing and can-making.

Explanation of symbols

10 ... can body, 11 ... body, 12 ... bottom

Claims (2)

Manufacture of a can body having a body thickness of more than 0.110 mm and not more than 0.125 mm, a total drawing ratio of 2.0 to 2.7, and a total ironing ratio of 50% or more and less than 60% An aluminum alloy plate for a can body used for,
In mass%, Si: 0.15-0.5%, Fe: 0.3-0.6%, Cu: 0.15-0.5%, Mn: 0.7-1.2%, Mg: Containing 0.8 to 2.0%, the balance is made of Al containing inevitable impurities,
The plate thickness is 0.250 mm or more and less than 0.275 mm, the material yield strength after baking is 265 MPa or more, and the number of intermetallic compounds having an equivalent circle diameter of 10 μm or more is 3 / mm ² or less. Excellent tensile pinhole resistance, characterized in that the tensile strength of the body part of the can body after can making by processing and paint baking is more than 330 MPa and 380 MPa or less, and the elongation of the body part is 4% or more. Aluminum alloy plate for can body.   Furthermore, 1% or 2 types in Zn: 0.05-0.30% and Ti: 0.05-0.15% are contained in the mass%, The flow resistance of Claim 1 characterized by the above-mentioned. Aluminum alloy plate for can bodies with excellent pinhole properties.

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