JPH07197175A - Aluminum alloy sheet for cap having excellent compressive strength and its production - Google Patents

Abstract

PURPOSE:To produce an Al alloy sheet having excellent compressive strength by executing homogenizing treatment, hot-rolling, cold-rolling containing two times of intermediate annealings and finish annealing to a specific composition of Al alloy cast ingot in a specific temp. condition. CONSTITUTION:The Al alloy cast ingot containing one or more kinds among 0.1-0.3wt.% Cu, 0.6-1.2% Mn, 1.0-2.5% Mg, 0.05-0.30% Zn or further, <0.3% Si and/or <0.25% Fe is heated to the temp. range of 450-550 deg.C to execute the homogenizing treatment and, thereafter, the hot-rolling is executed in the condition of >95% rolling ratio and >280 deg.C rolling finish temp. to form the hot-rolled sheet of e.g. 3mm thickness and, successively, the cold-rolling to about 0.7mm thickness is executed. Immediately after applying the intermediate annealing at >=100 deg.C/min heating and cooling rate, 400-500 deg.C reaching temp. for >=100min holding time to the cold-rolled sheet in a continuous annealing furnace, cold-rolling is executed at >=40% rolling ratio to form into the finish sheet thickness, and finally, the finish annealing is executed at 150-250 deg.C. The Al alloy sheet being dispersed with <=3000 pieces of intermetallic compound having <=3mum average grain diameter per unit area (mm<2>) then observed from the surface of the sheet material and having <=300N/mm<2> tensile strength, is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is of high strength (tensile strength 300).
~ 350 N / mm ² ) aluminum alloy plate, more specifically, press-fitting into a wedge shape (hereinafter referred to as score processing)
TECHNICAL FIELD The present invention relates to an aluminum alloy plate suitable for a ring-pull type cap and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
The cap material is pure Al JIS 1100, Al-M
Aluminum alloys such as n-based JIS3105 and Al-Mg-based 5052 are used, and these alloys are properly used depending on the type of contents and the shape of the cap. In carbonated drinks that are subject to gas pressure, if the material strength is low, the cap will come off the container, so increase the material plate thickness.
This can be dealt with by increasing the material strength, but in general, the material strength is increased to reduce costs.

However, in recent years, a score-pulled ring-pull type cap has been introduced. In this cap, when the internal pressure becomes high, the cap does not come off from the container, but the score part breaks (the internal pressure value at this point is pressure-resistant). Strength)
Therefore, it is not possible to cope with the problem by simply increasing the material strength as in the conventional case, and the plate thickness is increased at a high cost.

The score-processed ring-pull type cap material for carbonated beverages is required to have a high strength (tensile strength of 300 N / mm ² or more) and a property that the score portion is not easily broken.
However, in the 1100 alloy and the 3105 alloy, the tensile strength is about 200 N / mm ² and the strength is insufficient.

The example of Japanese Patent Publication No. 3-41537 discloses a general cap manufacturing method. The content is a homogenizing treatment at 510 ° C., a hot rolling at 500 to 300 ° C., a plate thickness of 3 mm, and a cold rolling at 0.
This is a manufacturing method in which a plate thickness is set to 5 mm, intermediate annealing is performed at a temperature of 480 ° C., and then cold rolling is performed to 0.25 mm.

However, Japanese Patent Publication No.
In the case of manufacturing by applying the conventional manufacturing method as shown in No. 37, there is a problem that the ears in the 0-90 ° direction (-: minus ears) become high in the drawing process and become unstable during transportation.

Here, the term “ear” refers to the difference in height between the peak (height H) and the valley (height h) generated on the side wall of the cap by drawing, and the ear ratio is defined by the following equation. is there. Ear rate = {2Σ (H−h) / Σ (H + h)} × 100 (%)

Under the circumstances, the present invention has an object to provide an aluminum alloy plate for a cap which is excellent in pressure resistance and is less likely to rupture the score portion, and a method for producing the same.

[0009]

In order to solve the above problems, the inventors of the present invention have noticed that when the existing material is used and the distribution state of the intermetallic compound is changed, it affects the pressure resistance strength. The chemical composition was examined in consideration of strength, corrosion resistance, moldability, and ear ratio suitable for the score-processed material for the ring-pull type cap.

That is, it is generally known that the finer the intermetallic compound of the material and the smaller the number per unit area, the greater the resistance to crack propagation due to stress concentration. Therefore, the present inventors have found that the intermetallic compound becomes fine by adjusting the amount of Zn, and further high strength is obtained by increasing the strength by adding an appropriate amount of Cu, Mn, and Mg.

That is, Cu: 0.1 to 0.3%, Mn:
0.6-1.2%, Mg: 1.0-2.5%, Zn: 0.05
~ 0.30%, if necessary Si: 0.3%
Hereinafter, Fe: an aluminum alloy containing 1 or 2 of 0.25% or less, the balance being Al and inevitable impurities, and the intermetallic compound seen from the surface of the material is 3000 / mm per unit area. ^The gist is an aluminum alloy plate for a cap, which has an average diameter of ² or less, a mean diameter of 3 μm or less, and a tensile strength of 300 N / mm ² or more and is excellent in pressure resistance.

Further, in the manufacturing method, the Al alloy ingot having the above chemical composition is homogenized at 450 to 550 ° C., and then the hot rolling finish temperature is set to 2 at a working rate of 95% or more.
Hot rolling is performed at 80 ° C. or higher, further cold rolling, and then continuous annealing is performed as intermediate annealing under the conditions of heating and cooling rate of 100 ° C./min or more and plate temperature of 400 to 500 ° C. for 10 minutes or less. Further, after that, cold rolling is performed at a rolling rate of 40% or more, and then finish annealing is performed in the range of 150 to 250 ° C.

[0013]

The present invention will be described in more detail below.

When the score portion is broken, the intermetallic compound peels off at the interface with the mother phase and becomes a crack propagation route. The smaller the intermetallic compound and the smaller the number per unit area, the higher the pressure resistance. Therefore, as described below, Z
By adjusting the amount of n, the intermetallic compound is made finer, and Cu,
High compressive strength can be obtained by increasing the strength by adding an appropriate amount of Mn and Mg. First, the reasons for limiting the chemical components in the present invention will be described.

Cu: Cu has the effect of increasing the tensile strength. However, if it is less than 0.1%, the effect is not sufficiently exhibited, and if it exceeds 0.3%, the corrosion resistance decreases, so the Cu content is made 0.1 to 0.3%.

Mn: Mn has an effect of enhancing mechanical properties. However, if it is less than 0.6%, the effect as a cap material that requires strength is not sufficiently exhibited, and if it exceeds 1.2%, an intermetallic compound such as (Fe · Mn) Al ₆ is produced and the pressure resistance strength is increased. Therefore, the amount of Mn is set to 0.6 to 1.2%.

Mg: Mg also has the effect of enhancing mechanical properties like Mn. However, if it is less than 1.0%, the effect is not sufficiently exhibited, and if it exceeds 2.5%, an intermetallic compound is formed and the pressure resistance is lowered, so that the Mg amount is 1.0 to 2.5.
%.

Zn: Zn has the effect of reducing the size of the intermetallic compound. However, if it is less than 0.05%, this effect is not sufficiently exhibited, and if it exceeds 0.30%, on the contrary, it promotes the formation of intermetallic compounds and lowers the pressure resistance.
The amount of n is 0.05 to 0.30%.

Further, in the present invention, Cu, Mn,
In addition to Zn as an essential component, one or two of the following elements can be added as required.

Si: Si has the effects of improving the drawability and preventing the roughening of the flow marks during deep drawing.
However, if it exceeds 0.3%, the deep drawability deteriorates, and Al
Since the withstand pressure strength decreases due to the formation of the —Fe—Si-based compound, the Si content is set to 0.3% or less.

Fe: Fe is a very important element for the size of the intermetallic compound and its abundance, and when it exceeds 0.25%, it promotes the formation of intermetallic compounds such as (Fe.Mn) Al ₆ together with Mn. However, although the compressive strength is lowered, Fe has the function of preventing flow marks and rough skin during drawing. Therefore,
The Fe content is 0.25% or less.

The elements other than the above are impurities, and it is preferable that the elements are as small as possible. For example, when Cr and Ti are contained, if the content of each of them is 0.05% or less, the pressure resistance obtained by the present invention is excellent. Since it does not change the characteristics of the aluminum alloy plate, it is allowed up to 0.05% in each case.

Further, in the present invention, the intermetallic compound observed from the surface of the obtained aluminum alloy plate is 3000 pieces / mm ² or less per unit area, and its average diameter is 3 μm or less. This is because when the intermetallic compound is more than 3000 pieces / mm ² per unit area or its average diameter is more than 3 μm, the pressure resistance is significantly lowered.

The aluminum alloy having the above chemical composition is melted and cast by a conventional method, and then homogenized and hot-rolled. In the present invention, the intermetallic compound is adjusted by adjusting the homogenizing conditions. One of the features is to regulate the size and distribution and improve the pressure resistance.

That is, if the soaking temperature is lower than 450 ° C., the intermetallic compound becomes too fine and hinders the formation of cubic texture, which is not preferable because the earing rate becomes too high. Since it is not preferable because it causes the formation of various intermetallic compounds, the temperature is set to 450 to 550 ° C.

After the homogenizing treatment, hot rolling is carried out. If the working ratio is lower than 95% and the hot rolling end temperature is lower than 280 ° C., a cubic orientation (100) (001) after intermediate annealing can be sufficiently obtained. Therefore, it is not preferable because the produced aluminum alloy plate has a high ear rate. Therefore, in hot rolling, the processing rate is 95% or more and the hot rolling end temperature is 280 ° C.
Perform under the above conditions.

Next, after performing an appropriate cold rolling, an intermediate annealing is performed. This annealing is performed in a continuous annealing furnace called CAL, and the conditions have a great influence on the intermetallic compound, strength and formability. Since it affects, it is regulated as follows.

That is, the substantial temperature of the plate during annealing affects recrystallization, and if the temperature is less than 400 ° C., the recrystallization is not completed, and if it exceeds 500 ° C., the crystal grains become coarse and the formability deteriorates. , 400 to 500 ° C. Also,
The heating / cooling rate at this time must be regulated to 100 ° C./minute or more. This is because Mg, which contributes to the strength, is necessary to maintain the solid solution state, and sufficient strength cannot be obtained at less than 100 ° C./min. Furthermore, if the holding time exceeds 10 minutes, the crystal grain size becomes too large, resulting in deterioration of moldability and roughening of the surface plate during cap processing,
The holding time is set to 10 minutes or less to increase the coating film damage.

After the intermediate annealing, the product sheet thickness is obtained by cold rolling. This cold rolling is a process that greatly affects the strength.
If the rolling rate is less than 40%, sufficient strength cannot be obtained, and the 0-90 ° ear becomes high in the drawing process. Therefore, the rolling rate needs to be 40% or more.

Further, after cold rolling, stabilization annealing (finish annealing) is performed. Stabilization annealing adjusts the strength, and by disposing dislocations entangled in the grain boundaries by cold rolling to reduce the dislocation density and suppress non-uniform deformation during drawing after coating. , Is an important step for preventing coating film defects. If the annealing temperature is less than 150 ° C, dislocations are not sorted out, and if it exceeds 250 ° C, the strength is rapidly reduced, and the stability in actual production is lacking. Therefore, the finish annealing temperature is in the range of 150 to 250 ° C.

Examples of the present invention will be shown below.

[0032]

Example 1 An aluminum alloy having the chemical composition shown in Table 1 was melted and cast, the ingot was faced, homogenized at 520 ° C. for 6 hours, and then hot rolled to a thickness of 3.0 mm. Then, it was cold-rolled to a thickness of 0.7 mm, and this was heat-treated in a continuous annealing furnace at a heating / cooling rate of 340 ° C./min at an ultimate temperature of 480 ° C. and a holding time of 10 seconds, and further cold-rolled to a plate thickness of 0.21 mm. Then, it was annealed at 190 ° C. for 2 hours, and finally heated at a temperature of 180 ° C. for 10 minutes (corresponding to the normal baking condition for coating a cap). The mechanical properties, ear ratio, and pressure resistance of the obtained plate material were investigated. The results are shown in Table 2.

For mechanical properties, tensile strength, physical strength and elongation were measured by a tensile test. The compressive strength was evaluated by the breaking stress in a tensile test using a notched test piece.

As is clear from Table 2, in the examples of the present invention, the mechanical properties and the ear ratios are equal to or higher than those of the conventional Al alloy or the Al alloys outside the scope of the present invention, and the notch breaking stress is extremely high. High pressure resistance.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

Example 2 A plate was manufactured from an Al alloy ingot having the same chemical composition as No. 1 in Table 1 (within the scope of the present invention) under various manufacturing conditions shown in Table 3 to obtain mechanical properties, ear ratio, and pressure resistance. The strength was investigated. The test method and evaluation method are the same as in Example 1. The survey results are shown in Table 3.

As is clear from Table 3, the Al alloy sheets No. 16 to No. 24 produced under the production conditions of the present invention are:
It shows proper strength, ear rate, and notch breaking stress. On the other hand, in Comparative Examples No. 25 to No. 36, if the homogenization treatment condition or the hot rolling condition is outside the scope of the present invention, the ear rate or the notch breaking stress is not sufficient, and the intermediate annealing condition or the intermediate If the post-annealing cold rolling conditions are outside the scope of the present invention, one of the strength, ear rate, and notch breaking stress is insufficient, and if the finish annealing conditions are outside the scope of the present invention, strength or notch breaking stress is not appropriate. .

[0039]

[Table 3]

[0040]

As described in detail above, according to the present invention,
It is suitable for ring-pull type caps because it can provide an aluminum alloy plate with high strength, excellent pressure resistance, and less rupture of the score part and good moldability.

Claims (3)

[Claims] 1. In weight% (hereinafter, the same), Cu: 0.1-
0.3%, Mn: 0.6 to 1.2%, Mg: 1.0 to 2.5
%, Zn: 0.05 to 0.30%, the balance being an aluminum alloy consisting of Al and unavoidable impurities, and the intermetallic compound viewed from the surface of the material is 3000 per unit area.
An aluminum alloy plate for a cap excellent in pressure resistance, characterized in that the number of particles / mm ² or less is 3 μm or less, and the tensile strength is 300 N / mm ² or more. 2. Further, Si: 0.3% or less, Fe: 0.25%
The aluminum alloy plate according to claim 1, containing one or two of the following. 3. An Al alloy ingot having the chemical composition according to claim 1 or 2 is homogenized at 450 to 550 ° C., and then the hot rolling finish temperature is 280 ° C. at a working rate of 95% or more.
The above hot rolling is performed, further cold rolling is performed, and then
As the intermediate annealing, continuous annealing is performed under the condition that the heating and cooling rate is 100 ° C./min or more, and the plate temperature is kept at 400 to 500 ° C. for 10 minutes or less, and then cold rolling is performed at a rolling rate of 40% or more, and then 150 to A method for producing an aluminum alloy plate for a cap, which is excellent in pressure resistance, characterized by performing finish annealing in a range of 250 ° C.