JP2016191137A - Aluminum alloy sheet for resin coated can body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy sheet for a resin coated can body, allowing a can body surface after DI processing to exert a glittering metallic feeling particular to metal.SOLUTION: An aluminum alloy sheet for a resin coated can body contains 4.0-6.0 mass% Mg, and the balance Al with inevitable impurities. On a surface of the sheet, an area ratio of coarsened crystals having a crystal grain size of 200 μm or larger as a major axis is 30-60%, and an average crystal grain size is 70 μm or larger.SELECTED DRAWING: None

Description

  The present invention relates to an aluminum alloy plate for a resin-coated can body, and more specifically, an aluminum alloy plate used for a can body of a resin-coated can that is made by squeezing and ironing and encloses beverages, foods, aerosols, etc. It is about.

Aluminum cans such as DI cans and bottle cans are formed by drawing and ironing (DI processing) in order to reduce the weight while securing the strength of the can, and then to the surface of the can Printing, filling the contents, and attaching a lid or cap.
In general, aluminum cans of such JIS 3004 and JIS 3104 are used for such aluminum cans in consideration of mechanical properties required for the cans.

The mechanical properties of aluminum can bodies are extremely important because they affect the quality of can bodies, but it is also important to improve the design of cans in order to respond to the diversification of consumer needs in recent years. It is recognized as an important matter.
Therefore, the following techniques have been proposed for improving the design of aluminum cans.

  For example, in Patent Document 1, a continuous pattern in which a large number of cells are arranged in the circumferential direction and the can axis direction is attached to at least a part of the smooth peripheral wall of the can body by printing, and the cells have continuous gradation. There has been proposed a metal can characterized in that it is displayed with a gradation of changing similar colors, and adjacent cells are separated by a boundary portion of a gradation color different from the display color of these cells.

JP 2014-223935 A

Resin coated cans molded by DI processing after applying resin coating (laminate coating) to the surface of the aluminum alloy plate are different from ordinary DI cans (coating is applied after DI processing). There is no direct contact between the surface of the plate and the tool (punch, die, etc.). Therefore, the can body of the resin-coated can is inferior in the metallic feeling peculiar to metals as compared with the can body of a normal DI can.
Therefore, even if a pattern is attached to the surface of the can body by printing as in the technique according to Patent Document 1, there is a limit in terms of improving the designability because the pattern does not appear. And it is difficult to express a metallic feeling that glitters on the surface of the can body only by printing such as the technique according to Patent Document 1.

  Therefore, an object of the present invention is to provide an aluminum alloy plate for a resin-coated can body in which the surface of the can body after DI processing exhibits a metallic metallic sparkle.

  That is, the resin-coated can body aluminum alloy plate according to the present invention contains Mg: 4.0 to 6.0% by mass, the balance is Al and inevitable impurities, and the major surface has a major axis of 200 μm or more. The area ratio of the coarsened crystal exhibiting the crystal grain size is 30 to 60%, and the average crystal grain size is 70 μm or more.

  According to this aluminum alloy plate for a resin-coated can body, the Mg content is within a predetermined range and the average crystal grain size is not less than a predetermined value. A feeling can be demonstrated. Furthermore, according to the aluminum alloy plate for the resin-coated can body, the area ratio of the coarse crystals is in a predetermined range, so that the crystal is in a mixed grain state on the surface of the aluminum alloy plate, and the light on the surface of the can body after DI processing. By increasing the scattering of the metal, it is possible to more reliably exhibit a metallic feeling peculiar to metals.

  Moreover, the aluminum alloy plate for resin-coated can bodies according to the present invention contains Mg: 4.0 to 6.0% by mass, the balance is Al and inevitable impurities, and the average crystal grain size is on the plate surface. 90-150 micrometers may be sufficient.

  According to this aluminum alloy plate for a resin-coated can body, the content of Mg is in a predetermined range and the average crystal grain size is in a predetermined range, so that the surface of the can body after DI processing has a metallic feel peculiar to metal. Can be demonstrated.

The aluminum alloy plate for a resin-coated can body according to the present invention has a Mg content within a predetermined range, an area ratio of coarse crystals within a predetermined range, and an average crystal grain size equal to or greater than a predetermined value. The can body surface after processing can exhibit a metallic feeling peculiar to metal.
In addition, the aluminum alloy plate for a resin-coated can body according to the present invention has a Mg content within a predetermined range and an average crystal grain size within a predetermined range, so that the surface of the can body after DI processing is unique to the metal. A metallic feeling can be exhibited.

3 is a photographic image showing a state of a surface of a specimen 1 before DI processing. 3 is a photograph image showing a state of a surface of a specimen 4 before DI processing. 3 is a photographic image showing the state of the surface of the specimen 5 before DI processing.

  Hereinafter, the form for implementing the aluminum alloy plate for resin-coated can bodies which concerns on this invention is demonstrated in detail.

[Aluminum alloy plate for resin-coated can body]
The resin-coated can body aluminum alloy plate according to the present invention (hereinafter referred to as “aluminum alloy plate” as appropriate) contains Mg in a predetermined range, and the balance is made of Al and inevitable impurities. The area ratio of the coarsened crystal is in a predetermined range, and the average crystal grain size is not less than a predetermined value.
The aluminum alloy plate according to the present invention contains Mg in a predetermined range, the balance is made of Al and inevitable impurities, and the average crystal grain size is in the predetermined range on the plate surface.

  Hereinafter, the reason why the alloy components of the aluminum alloy plate according to the present invention, the area ratio of coarse crystals, and the average crystal grain size are limited numerically will be described.

(Mg: 4.0-6.0% by mass)
Mg has an effect of improving strength by solid solution strengthening in an aluminum alloy. By setting the Mg content to 4.0% by mass or more, a desired strength as a can body can be obtained. On the other hand, if the content of Mg exceeds 6.0% by mass, cracks are likely to occur during hot rolling, making manufacture difficult.
Therefore, the content of Mg is 4.0 to 6.0% by mass.

(Inevitable impurities)
As unavoidable impurities, Fe, Si, Zn, Cu, Mn, Cr, Zr, Ti, V, Ga, Ni, and the like may be contained within a range that does not hinder the effects of the present invention. Specifically, each of Fe and Si is 0.10% by mass or less, and the other is 0.05% by mass or less.
For Fe, Si, Zn, Cu, Mn, Cr, Zr, Ti, V, Ga, Ni, etc., the content is not more than the predetermined value described above, and the total amount is not more than 0.15% by mass. For example, not only when it is contained as an unavoidable impurity, but also when it is actively added, the effect of the present invention is not hindered.

  Next, the properties of the surface of the aluminum alloy plate according to the present invention will be described. A state in which coarse crystals and fine crystals are mixed (first embodiment) and a state in which relatively large crystals occupy the majority. Since there are two types (the second embodiment), the surface properties will be described in two parts.

(First embodiment: average crystal grain size is 70 μm or more)
The aluminum alloy plate (first embodiment) according to the present invention has an average crystal grain size of 70 μm or more in a direction perpendicular to the rolling direction on the plate surface.
When the average crystal grain size is 70 μm or more, the crystal grains appearing on the plate surface are large as a whole, and the surface of the can body after DI processing can exhibit a metallic feeling peculiar to metal. On the other hand, if the average crystal grain size is less than 70 μm, the crystal grains appearing on the plate surface will be too small as a whole, and even if light is applied to the surface of the can body after DI processing, a metallic metal specific to metal There is no feeling.
Therefore, the average crystal grain size is 70 μm or more.
The upper limit of the average crystal grain size is not particularly limited, but those exceeding 300 μm are difficult to manufacture.

The average crystal grain size can be measured by the following method.
The surface of the aluminum alloy plate after the second cold rolling in the manufacturing method described later is electrolytically etched, washed with water, dried, photographed with an optical microscope, and then cut in a direction perpendicular to the rolling direction. To calculate the average crystal grain size. In the measurement using the intercept method, for example, one measurement line length is set to 40.5 mm, and a total of five measurement fields are observed with three lines per one field, so that the total measurement line length is 40.5 × 15 mm. And it is sufficient.
The average crystal grain size of the aluminum alloy plate (first embodiment) according to the present invention is controlled by the content of each of the alloy components described above, and among the steps of the manufacturing method described later, in particular, annealing in the intermediate annealing step. It can be controlled by temperature.

(First embodiment: The area ratio of coarse crystals is 30 to 60%)
In the aluminum alloy plate according to the present invention (first embodiment), the area ratio of coarse crystals having a crystal grain size of 200 μm or more is 30 to 60% on the plate surface. This crystal grain size is specifically the major axis (largest diameter) of the crystal grain, and a crystal exhibiting a crystal grain size having a major axis of 200 μm or more was defined as a coarse crystal.
If the area ratio of the coarse crystals is less than 30%, the number of fine crystals increases. If the area ratio exceeds 60%, the coarse crystals increase, so that in any case, The desired state in which coarsened crystals are mixed is not achieved. On the other hand, by setting the area ratio of coarse crystals to 30 to 60%, the crystal becomes a desired mixed grain state on the surface of the aluminum alloy plate, the direction of each crystal grain surface is randomized, and the surface of the can body after DI processing The scattering of light becomes stronger. As a result, the surface of the can body after DI processing can exhibit an excellent metallic feel unique to metal.
Accordingly, the area ratio of coarse crystals having a crystal grain size of 200 μm or more is 30 to 60%.

The area ratio of the coarsened crystal can be measured by the following method.
The surface of the aluminum alloy plate after the second cold rolling in the manufacturing method described later is subjected to electrolytic etching, washed with water and dried, then photographed with an optical microscope, and subjected to image processing to obtain a major axis (in the most preferred direction in an observation field). A coarse crystal having a large diameter) of 200 μm or more is used as a coarse crystal, and an equivalent area of the coarse crystal is calculated, and an area ratio (= a proportion of the area of the coarse crystal in a predetermined area) may be measured.
About the area ratio of the coarsening crystal | crystallization of the aluminum alloy board (1st Embodiment) which concerns on this invention, while controlling by content of each above-mentioned alloy component, also in the process of the manufacturing method mentioned later, especially an intermediate annealing process It can be controlled by the annealing temperature.

(Second Embodiment: Average crystal grain size is 90 to 150 μm)
The aluminum according to the present invention (second embodiment) has an average crystal grain size of 90 to 150 μm.
When the average crystal grain size is 90 to 150 μm, the crystal grains appearing on the plate surface are considerably large as a whole, and the surface of the can body after DI processing can exhibit a metallic feeling peculiar to metal.
Therefore, the average crystal grain size is 90 to 150 μm.

  The average crystal grain size of the aluminum alloy plate (second embodiment) according to the present invention is controlled by the content of each of the alloy components described above, and among the processes of the manufacturing method described later, in particular, annealing in the intermediate annealing process. It can be controlled by temperature.

(Second embodiment: other)
The surface properties of the aluminum alloy plate (second embodiment) according to the present invention are preferably in a state in which relatively large crystals occupy the majority (that is, in a non-mixed state). Therefore, on the surface of the plate, the area ratio of relatively large crystals having a crystal grain size of 90 to 150 μm as the major axis is preferably 90% or more, and more preferably 100%.

(State of aluminum alloy plate)
The aluminum alloy plate according to the present invention basically refers to an alloy plate coated with a resin after the resin coating step in the production method described later. An alloy plate in a state where the resin before the coating step is not coated and an alloy plate in a state where the base treatment before the resin coating is not performed are also included.
Here, the “resin” may be any resin for covering the aluminum alloy plate before DI processing, and for example, a PET film or a PBT film may be used. The thickness of the resin layer (film) formed on the surface of the aluminum alloy plate may be 10 to 200 μm. In addition, favorable DI workability can be obtained by coating the aluminum alloy plate with a resin before DI processing.

(Use)
The use of the aluminum alloy plate according to the present invention is a can body of a resin-coated can formed by DI processing after a resin coating (laminate coating) is applied to the surface. In addition, according to the aluminum alloy plate which concerns on this invention, since the can body surface after DI process exhibits the metallic feeling peculiar to a metal, it can be used suitably for the can body of the resin coating can which requires designability.

  The aluminum alloy plate according to the present invention is as described above, but the other characteristics that are not clearly specified are not particularly limited as long as they are conventionally known and exhibit the effects obtained by the characteristics. Needless to say.

[Method for producing aluminum alloy sheet for resin-coated can body]
Next, the manufacturing method of the aluminum alloy plate concerning this invention is demonstrated.
The aluminum alloy sheet according to the present invention includes a casting process, a homogenization heat treatment process, a hot rolling process, a first cold rolling process, an intermediate annealing process, and a second cold rolling process. Manufactured. Moreover, the aluminum alloy plate which concerns on this invention is manufactured by performing a resin coating process after a 2nd cold rolling process.
Hereinafter, the respective steps will be mainly described.

(Casting process)
In the casting process, the aluminum alloy having the above-described composition is melted, cast by a known casting method such as a DC casting method, cooled to below the solidus temperature of the aluminum alloy, and a predetermined thickness (for example, 400 (About 600 mm).

(Homogenization heat treatment process)
In the homogenization heat treatment step, the homogenization heat treatment is performed at a predetermined temperature before rolling the ingot cast in the casting step. By subjecting the ingot to homogenization heat treatment, internal stress is removed, solute elements segregated at the time of casting are homogenized, and intermetallic compounds precipitated at the time of casting cooling and thereafter grow.
The heat treatment temperature in this homogenization heat treatment step is preferably 500 to 550 ° C. By setting the temperature to 500 ° C. or higher, the above-described homogenization effect can be obtained. On the other hand, when the processing temperature exceeds 550 ° C., the ingot is melted and it becomes difficult to manufacture the alloy plate.
The heat treatment time is not particularly limited, and may be 1 to 24 hours.

In the homogenization heat treatment step, even after “homogeneous heat treatment” after the homogenization heat treatment, the hot rolling is performed without cooling. ) Even after “2 times soaking” in which hot rolling is carried out after reheating after chamfering and chamfering, after the homogenization heat treatment, it is cooled to the hot rolling start temperature and hot rolling “Two-stage soaking” may be performed.
Here, when performing “one-time soaking” and “two-stage soaking”, it is only necessary to chamfer before the homogenization heat treatment step.

(Hot rolling process)
In the hot rolling step, the homogenized ingot is hot rolled.
The rolling start temperature and the rolling end temperature in this hot rolling step are not particularly limited. For example, the rolling start temperature is 400 to 550 ° C., and the rolling end temperature is 250 to 380 ° C., preferably 300 ° C. or higher. .
And it can be set as the hot rolled sheet (hot coil) of desired plate | board thickness by performing the hot rolling which consists of a several path | pass.

(First cold rolling process)
In the first cold rolling step, the hot rolled plate is cold rolled.
The rolling reduction in the first cold rolling step is preferably 80% or less. If the rolling reduction exceeds 80%, the processing strain increases, so that the crystal grains become coarser than necessary after the intermediate annealing.

(Intermediate annealing process)
In the intermediate annealing step, the rolled sheet after the first cold rolling step is annealed.
The annealing temperature in this intermediate annealing step is preferably 400 to 550 ° C. When the annealing temperature is less than 400 ° C., the crystal grains of the produced aluminum alloy plate become fine, and the average crystal grain size on the plate surface becomes a desired value or less. On the other hand, when the annealing temperature exceeds 550 ° C., melting occurs on a part of the surface during annealing, making it difficult to produce an aluminum alloy plate.

When the annealing temperature in the intermediate annealing step is a low temperature region (400 to 460 ° C.) among the above temperature range, the crystal grains of the manufactured aluminum alloy plate are likely to be in a mixed grain state, in other words, the first embodiment described above. It tends to be the surface property of the form. On the other hand, in the high temperature range (above 460 ° C. and below 550 ° C.) of the above temperature range, the crystal grains of the manufactured aluminum alloy plate are unlikely to be mixed, in other words, the surface of the second embodiment described above. It is easy to become.
Therefore, the annealing temperature in the intermediate annealing step is more preferably 400 to 460 ° C. in order to bring the area ratio of the coarse crystal on the plate surface into a desired range by making the crystal grains of the aluminum alloy plate into a mixed grain state. .
In addition, it is preferable that the annealing time in an intermediate annealing process shall be 2 to 11 hours.

(Second cold rolling process)
In the second cold rolling step, the rolled plate after the intermediate annealing is cold rolled.
The rolling reduction in this second cold rolling step is preferably 30% or more. After performing the intermediate annealing as described above, by performing cold rolling at a reduction rate of 30% or more, the surface of the can body after DI processing has an excellent metal-specific metallic feeling (the difference between SCI and SCE described later) To make it smaller).

(Resin coating process)
In the resin coating step, the surface of the rolled plate after the second cold rolling step is coated with a resin (resin lamination).
The thickness of the resin or resin layer (film) used in this resin coating step is as described above. The method for coating the resin is not particularly limited, and may be performed by a conventionally known method such as heat fusion.
In the resin coating step, the surface treatment of the rolled plate may be appropriately performed before the resin coating process. This base treatment is a conventionally known treatment such as a phosphoric acid chromate treatment, a chemical conversion treatment using Ti-Zr or the like, a primer treatment or the like.

  The method for producing an aluminum alloy plate according to the present invention is as described above. However, in carrying out the present invention, other processes are performed between or before and after each process within a range that does not adversely affect each process. May be included. For example, a processing step of cutting and punching the aluminum alloy plate into a predetermined size may be included after the second cold rolling step or the resin coating step.

  In addition, as for conditions that are not clearly shown in the respective steps, it is sufficient to use conventionally known conditions, and it is needless to say that the conditions can be appropriately changed as long as the effects obtained by the processing in the respective steps are exhibited.

  Next, the aluminum alloy plate according to the present invention will be specifically described by comparing an example satisfying the requirements of the present invention with a comparative example not satisfying the requirements of the present invention.

[Production of test materials]
Aluminum alloys having the compositions shown in Table 1 were melted and ingots were produced by DC casting (Direct Chill casting). And after performing the homogenization heat processing for 4 hours at 540 degreeC with respect to the produced ingot, hot rolling (starting temperature: 500 degreeC, winding temperature: 320 degreeC) was performed. Subsequently, first cold rolling and intermediate annealing were performed under the conditions shown in Table 1. Then, it rolled until the board thickness became 0.32 mm by 2nd cold rolling, and produced the test material (Aluminum alloy board for resin-coated can bodies).

[Measuring method]
(Average crystal grain size)
The surface of the test material after smut removal was electrolytically etched, washed with water and dried, then photographed with an optical microscope (× 25 times), and averaged using a section method in a direction perpendicular to the rolling direction. The value of the crystal grain size was calculated. In the measurement using the intercept method, the length of one measurement line was 40.5 mm, and the total measurement line length was 40.5 × 15 mm by observing a total of five fields with three lines per field of view. .

(Area ratio of coarse crystals)
The surface of the test material after removal of the smut is electrolytically etched, washed with water and dried, then photographed with an optical microscope (× 25 times), and the major axis is 200 μm or more in an arbitrary direction in the observation field by image processing. As a coarse crystal, the equivalent area of the coarse crystal in an area of 3.5 mm × 2.7 mm was calculated, and the area ratio was measured.

[Evaluation]
(Evaluation of metallic feeling peculiar to metal)
A PET film having a thickness of 20 μm (manufactured by Teijin DuPont, TEFLEX (registered trademark) FTC) was attached to both surfaces of the prepared test material by heat sealing. Thereafter, drawing and ironing were performed to prepare a DI can (outer diameter 66 mm, 350 ml capacity can).
The DI can was heat-treated (200 ° C., 20 minutes), and then a flat plate (207 mm × 100 mm) was cut out from the can body, and the surface of the outer wall of the can was measured with a color difference meter (Konica Minolta, CM- 600d). Note that the measurement with a color difference meter is performed with two measurement methods of a measurement wavelength of 500 nm, an SCI (Special Component Include: including specular reflection light) method, and an SCE (Special Component Exclude: excluding specular reflection light) method. It was to do. Then, the difference between the measurement result by the SCI method and the measurement result by the SCE method was calculated.
It was found that the smaller the difference in the measurement results between the SCI method and the SCE method, the better the metallic feel that is unique to metals. Therefore, it is judged that the difference in the measurement result between the SCI method and the SCE method is more than 20.0 and less than or equal to 30.0, and a metallic feeling peculiar to metal can be exhibited. It was judged that the metallic feeling peculiar to the metal which was excellent in can be exhibited.
In addition, for the test materials 1, 4, and 5, in order to confirm the state of crystal grains on the surface before DI processing, photographs of the aluminum alloy plate after the second cold rolling were taken, respectively, and FIG. Shown in ~ 3.

  Detailed aluminum alloy components and production conditions are shown in Table 1. In addition, Table 2 shows each measurement result and evaluation result. In Tables 1 and 2, numerical values that do not satisfy the configuration of the present invention are underlined.

[Examination of results]
Regarding the test materials 1 to 4, since the requirements stipulated by the present invention were satisfied, the difference between SCI and SCE was 30.0 or less, and the surface of the can body after DI processing had a metallic feeling (glitter) peculiar to metal. Appearance).
In particular, for the test materials 1 to 3, the crystal grains of the aluminum alloy plate were in a mixed grain state, and the area ratio of the coarsened crystals on the plate surface was in the desired range, so the difference between SCI and SCE was It became 20.0 or less, and the metallic feeling peculiar to the metal on the surface of the can body after DI processing became very excellent.

On the other hand, for the test material 5, the average crystal grain size was small because the temperature of the intermediate annealing was low. As a result, the difference between SCI and SCE exceeded 30.0, and the surface of the can body after DI processing did not exhibit a metallic feeling peculiar to metal.
Moreover, about the test material 6, since content of Mg exceeded the upper limit of the numerical range prescribed | regulated by this invention, the crack generate | occur | produced at the time of hot rolling.

In addition, about the surface before DI processing, as shown in FIG. 1, it can confirm that the test material 1 is in the state where the coarse crystal and the fine crystal are mixed, and the test material 4 is shown in FIG. It has been confirmed that only relatively large crystals exist as shown in FIG.
On the other hand, as shown in FIG. 3, it was confirmed that the specimen 5 was in a state where only fine crystals were present.

  From the above results, it was found that the aluminum alloy plate according to the present invention has a metallic feel peculiar to the surface of the can body after DI processing.

Claims (2)

Mg: 4.0 to 6.0% by mass, the balance being Al and inevitable impurities,
An aluminum alloy plate for a resin-coated can body, characterized in that the area ratio of coarse crystals having a crystal grain size of 200 μm or more as the major axis is 30 to 60% and the average crystal grain size is 70 μm or more. . Mg: 4.0 to 6.0% by mass, the balance being Al and inevitable impurities,
An aluminum alloy plate for resin-coated can bodies, wherein the average crystal grain size is 90 to 150 μm on the plate surface.