JP2000248326A - High formability aluminum alloy sheet excellent in recyclability, and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high formability aluminum alloy sheet excellent in recyclability, having high ironing formability, and particularly suitable for use as a can body material for DI cans. SOLUTION: This aluminum alloy sheet has a composition consisting of, by weight, 0.8-1.2% Mn, 0.15-0.25% Cu, 0.25-0.6% Fe, 0.30-0.50% Si, Mg in an amount within the range satisfying ( 1 3 7. 5 + 8 8. 5 × S i - 53.0×Mn-167.6×Cu-24.6×Fe)/71.9<=Mg<=(167.5+88.5×Si-53.0×Mn-167.6×Cu-24.6×Fe)/71.9, <=0.25% Zn, 0.01-0.10% Ti, and the balance Al with <=0.15%, in total, of impurities.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a highly formable aluminum alloy sheet having excellent recyclability and high ironing formability, and particularly excellent in recyclability suitable for use as a can body for DI cans. It relates to the manufacturing method.

[0002]

2. Description of the Related Art In recent years, recycling of used cans (UBC: Used Beverage Can) such as beverage cans has become an important issue from the viewpoint of environmental protection. The body (can body), end (can end) and tub are not the same aluminum alloy, which is an obstacle to recycling UBC. That is, A3004 alloy (Al-1.2% Mn-1.0% Mg) is generally used for the body material, and A5082 alloy (Al-4.5% M) is used for the end material and the tab material.
g), A5182 alloy (Al-4.5% Mg-0.35)
% Mn) or A5052 alloy (Al-2.5% Mg)
-0.25% Cr).

Therefore, when the regenerated lump component of UBC is arithmetically calculated based on the composition table of the alloy used, the components other than Mg should be lower in the body material.
When an actual regenerated lump component is analyzed, Si or Fe or the like is often mixed in the process of forming the regenerated lump, so that the result does not become the same as the arithmetic calculation. In particular, the increase and variation of Si become remarkable. The body, end, and tub components and weight of a randomly purchased all-aluminum beverage can were measured, and the regenerated lump component of UBC was arithmetically calculated.
i was 0.23% on average, but the UB of this beverage can
C was actually dissolved and its regenerated mass component was measured.
Was 0.29% in average value and 0.04% in standard deviation value, the Si content was higher than the arithmetic calculation value, and the variation was large.

[0004] Under such circumstances, conventionally, in order to produce can materials by recycling UBC such as all-aluminum beverage cans, the amount of UBC regenerated lump used in order to satisfy the component standards required for each of them. At present, it is necessary to adjust the ingredients by adding new bullion. Furthermore, S
i is liable to undergo transformation and precipitation together with Mn (Fe) during heating and hot rolling of the ingot, accompanied by a decrease in the amount of Mn solid solution essential for maintaining the strength of the body material and a decrease in fine precipitation (coarsening),
In particular, since the strength is reduced after the baking treatment of the paint after the can-making, the properties of the can, particularly the strength, cannot be maintained. Therefore,
When the UBC regenerated lump is used as a can material, there is an inconvenience that casting must be performed particularly under sufficient control of the amount of Si, which is a factor of high cost.

[0005]

SUMMARY OF THE INVENTION The present invention is particularly directed to UBC
The purpose of the present invention is to eliminate the above-mentioned conventional disadvantages in the recycling of steel. The purpose is to improve the quality and performance of cans even when the amount of Si in the recycled UBC mass fluctuates when used as can bodies. While maintaining at least the same level as the current level, secure high iron formability, obtain sufficient can body strength, eliminate appearance defects after ironing, and at the same time have sufficient corrosion resistance High moldability with excellent recyclability An object of the present invention is to provide an aluminum alloy plate and a method for manufacturing the same.

[0006]

In order to achieve the above object, the high formability aluminum alloy sheet having excellent recyclability according to the first aspect of the present invention comprises Mn: 0.8 to 1.2% and C
u: 0.15 to 0.25%, Fe: 0.25 to 0.6
%, Si: 0.30 to 0.50%, and Mg in an amount obtained by substituting the content percentages of Mn, Cu, Fe and Si into the following formula, and further Zn: It is characterized by containing 0.25% or less and Ti: 0.01 to 0.10%, with the balance being Al and impurities of 0.15% or less in total. (137.5 + 88.5 × Si% −53.0 × Mn% −
167.6 × Cu% −24.6 × Fe%) / 71.9 ≦
Mg% ≦ (167.5 + 88.5 × Si% −53.0 ×
(Mn% -167.6 × Cu% −24.6 × Fe%) / 7
1.9

The highly formable aluminum alloy sheet having excellent recyclability according to claim 2 of the present invention has a Mn of 0.8 to 0.8.
1.2%, Cu: 0.15 to 0.25%, Fe: 0.2
5 to 0.6%, Si: 0.30 to 0.50%,
And the content of Mn, Cu, Fe and Si in the following equation:
And the amount of Mg obtained by substituting
% Or less, including Ti: 0.01 to 0.10%, with the balance being A
1 and 0.15% or less in total. Mg% = (ABYS-102.5 + 88.5 × Si% −
53.0 × Mn% −167.6 × Cu% −24.6 × F
e%) / 71.9 (ABYS: desired strength (MPa) after heat-treating the aluminum alloy plate at 205 ° C. for 10 minutes and a numerical value between 240 and 270)

According to the method for producing a highly formable aluminum alloy sheet having excellent recyclability according to the present invention, an aluminum alloy having the component composition described in claim 1 or 2 is subjected to DC ingot casting, homogenization treatment, hot working, and the like. In the step of manufacturing an aluminum alloy sheet through rolling and cold rolling, the electrical conductivity (IACS%) after hot rolling is 41.0% or more, and among the compounds present on the sheet surface after cold rolling. , No compound exceeding 15 μm was present, and the area ratio of the compound of 1 to 15 μm was 5.0% or more, and the α-phase compound (Al-M
The area ratio of the (n-Fe-Si-based compound) is 50% or more, and the area ratio of the Mg ₂ Si phase is 1.0% or less.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The significance of the alloy components in the highly formable aluminum alloy sheet of the present invention and the reasons for limiting the same will be explained. Mn is a main component for imparting strength, and an α-phase compound (Al-Mn) —Fe—Si system) functions to prevent seizure during ironing (DI processing) and increase can body strength. The preferable content range of Mn is 0.8 to 1.2%, and 0.8%
If less than 1.2%, the effect is not sufficient.
The crystallized Al ₆ (Mn, Fe) produced at the time of casting together with e becomes coarse, which causes deterioration in DI formability, neck / flange formability, and the like.

[0010] Cu is formed together with Mg by low-temperature heat treatment or the like.
It functions to form an Al-Mg-Cu-based compound to increase the strength and to suppress softening due to heating such as baking.
A preferable content range of Cu is 0.15 to 0.25%. If the content is less than 0.15%, the effect is not sufficient.
If it exceeds 5%, the work hardenability at the time of molding becomes too large, and conversely, the moldability decreases, and adverse effects such as a decrease in corrosion resistance occur.

Fe and Al ₆ (Mn,
Fe) phase, α-phase compound (Al-Fe-Mn-Si system),
It forms an Al-Fe-Si compound and functions to prevent seizure between the material and the tool during DI processing. The preferable content range of Fe is 0.25 to 0.6%, and 0.25 to 0.6%.
%, The seizure resistance is degraded, and the UBC usage rate is further reduced to lower the recyclability. If it exceeds 0.6%, a coarse compound is liable to be formed, which may be a starting point of breakage during molding, which is not preferable.

Si is a necessary component for improving the recyclability of the can material, and together with Mn and Fe, an α-phase compound (Al-Mn-Fe-Si) which is effective in preventing seizure during ironing.
System). The preferable content range of Si is 0.30 to 0.5%, and if less than 0.30%, U
Lowering the BC usage rate and reducing recyclability, 0.5%
Percent more than the Al-Mn-Si phase and Mg ₂ Si AiAkira distillate is heavily formed, impairing the corrosion resistance and a coarse.

[0013] Mg is a main component that brings strength to the aluminum alloy sheet of the present invention together with Mn. The strengthening factor is largely due to solid solution hardening, and the addition of Mg increases the amount of Mn solid solution with the increase in Si content. The decrease in strength of the can resulting from the decrease is compensated for. The preferable Mg content range is defined by the formula (1) with respect to the variation of each component. (137.5 + 88.5 * Si% -53.0 * Mn% -167.6 * Cu% -2 4.6 * Fe%) / 71.9≤Mg% ≤ (167.5 + 88.5 * Si%- 53.0 x Mn%-167.6 x Cu%-24.6 x Fe%) / 71.9-(1)

Further, the strength after baking is slightly different depending on the intended use of the can body.
Considering BYS (desired proof stress after heating treatment equivalent to paint baking at 205 ° C. for 10 minutes in the range of 240 to 270 MPa), it is defined by equation (2), and the target value of ABYS is substituted for M
Determine the amount of g. Mg% = (ABYS−102.5 + 88.5 × Si% −53.0 × Mn% −16 7.6 × Cu% −24.6 × Fe%) / 71.9 −− (2)

Mg is preferably small from the viewpoint of corrosion resistance. However, if the content of Mg is less than the content% determined by the above formula (1) or (2), the required strength of the can cannot be obtained. %, The corrosion resistance decreases.

Zn functions to improve drawability, DI workability, and neck / flange formability. However, if the Zn content exceeds 1.0%, the corrosion resistance is impaired and the cost is disadvantageous. Therefore, the Zn content is 0.25, which is the same range as the current A3004 (A3104) alloy.
% Is preferable.

Ti functions to refine the cast structure, improve rolling workability and recrystallization characteristics, and make the structure uniform, reduce the anisotropy of the finally obtained alloy plate, and formability. Improve. The preferable content range of Ti is 0.01
If it is less than 0.01%, the above effect is small, and if it exceeds 0.1%, a coarse Al-Ti compound or Ti-B compound is formed, and serious damage such as cracks and pinholes is caused. It is not preferable because it causes serious defects.

In the present invention, by limiting the alloy components as described above, a highly formable aluminum alloy sheet having excellent recyclability can be obtained. In other words, on the quality of the can, the appearance and corrosion resistance after ironing are the most important, and the poor appearance after ironing is mainly caused by seizure, but in the present invention, the Si mixed in the recycling process is effectively used. Thus, the α phase compound (Al—Mn—Fe—Si system) in which the Al ₆ (Mn, Fe) compound generated at the time of casting is phase-transformed is increased, and burn-in is effectively prevented. Regarding the corrosion resistance, the type and amount of the intermetallic compound are problematic, but by specifying the composition as described above, the type and amount of the intermetallic compound are regulated, and excellent corrosion resistance can be obtained.

Further, the strength of the can body, especially the can bottom pressure for preventing the can bottom from being deformed when an internal pressure is applied, is determined by baking the material before baking (heating at a temperature of about 200 ° C. for several minutes). In the present invention, as described above, the required proof stress after the baking treatment and the S
If the amount of i is known, even if the amount of Si in the UBC fluctuates, by adjusting the amount of Mg, it is possible to obtain the necessary proof stress after the baking treatment, and to secure a sufficient pressure resistance for the can body. Can be.

The method for producing a highly formable aluminum alloy sheet having excellent recyclability according to the present invention will be described. First, an aluminum alloy having the above-mentioned component composition is melted and, for example, formed into an ingot by continuous casting. The ingot is homogenized. The homogenization treatment is performed at 600 to 640 ° C for 1 hour.
It is preferable to carry out the heating under the condition of heating for more than an hour. Mn, Mg, Si, F
e and other additional elements are dissolved. The solid solubility increases as the temperature increases and the time increases.

Α-phase compound (Al—Mn—Fe—Si system) that gives an anti-seizure effect during ironing (DI)
Transformation (Al ₆ (Mn, transformation from Fe)) to be in order to perform adequately and is preferably carried out by high-temperature and long-time homogenization treatment can, when heated above 640 ° C., the ingot Since the eutectic melting occurs partially and the quality of the plate surface is likely to deteriorate, the above homogenization treatment conditions are preferable. If the homogenization temperature is in the range of 600 to 640 ° C., the homogenization time of 1 hour or more is sufficient. Even if it is kept for more than 10 hours, the effect is saturated and it is not economical.

The hot rolling of the homogenized ingot is performed at 450
It is preferable to start in the temperature range of ５550 ° C. (material temperature). If it is lower than 450 ° C., recrystallization during hot rolling becomes insufficient, and the ear ratio (anisotropic) tends to deteriorate. The ear ratio of the final sheet depends on the recrystallization texture at the end of hot rolling and the rolling texture at the time of subsequent cold rolling. When the hot rolling start temperature exceeds 550 ° C., the sheet surface is oxidized and the recrystallized grains are coarsened, so that the formability is easily reduced.

The end temperature (material temperature) of hot rolling is 280.
~ 350 ° C is preferred. If it is lower than 280 ° C., recrystallization is insufficient, and if it is higher than 350 ° C., recrystallized grains tend to be coarse, and in any case, the ear ratio tends to deteriorate. In consideration of the use of the material of the present invention, the thickness of the final plate is 0.25 to 0.35.
Since the thickness is about mm, the end thickness of the hot rolling is preferably set to 3 mm or less in consideration of reducing the total thickness reduction rate of the subsequent cold rolling to 90% or less.

Further, it is important that the electrical conductivity (IACS%) of the hot-rolled sheet obtained in the above step is 41.0% or more. This index indicates the magnitude of the Mn solid solution amount, and a larger value means that the solid solution amount is smaller. That is, Mn
Is precipitated as a compound of Al-Mn-Si,
, The precipitation of Mg ₂ Si, which is disadvantageous to corrosion resistance, is prevented. On the other hand, a decrease in the strength of the can caused by a decrease in the amount of solid solution of Mn is compensated for by adding Mg, and the strength of the can after the paint baking treatment is maintained by solid solution hardening of Mg.

[0025] Cold rolling is performed to improve the material strength. The total reduction is 80 to 80% depending on the relationship between strength and ear rate.
A range of 88% is particularly preferred. If the total rolling reduction is less than 60%, sufficient strength cannot be obtained, and if it exceeds 90%, the rolling texture develops too much, the 45 degree ear ratio becomes too high, and the material yield deteriorates.

With respect to the sheet after cold rolling, no compound exceeding 15 μm was present on the surface,
m is at least 5.0%, and α
The area ratio of the phase compound is 50% or more, and Mg ₂ S
It is preferable that the area ratio of the i-phase is 1.0% or less. The distribution of the compound is measured by an image analyzer (for example, Luzex III (U), manufactured by Nireco) used for measuring the distribution of precipitates and the like in the metal field.

When a compound exceeding 15 μm is present, it becomes a starting point of cracking during flange forming after ironing and neck forming, and the compound of 1 to 15 μm is mainly composed of an Al ₆ (Mn, Fe) phase crystallized product formed during casting. And the crystallized substance is converted into an α phase by a homogenization treatment. These compounds function to prevent seizure during ironing. If the absolute amount is less than 5.0%, the effect is small. Further, of these, the area ratio of the α-phased compound is 50%.
Even if less than%, the effect is small. Since the Mg ₂ Si phase is disadvantageous to the decrease in the amount of Mg solid solution required for maintaining the strength after the paint baking treatment and the corrosion resistance, the area ratio on the plate surface is preferably 1.0% or less.

[0028]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples, and the effects thereof will be demonstrated based on them. It should be noted that these examples are for describing a preferred embodiment of the present invention, and the present invention is not limited thereto.

Example Each aluminum alloy having the component composition shown in Table 1 (compositions shown in Nos. 1 to 12) was melted by a conventional method, and each ingot was formed by semi-continuous casting. 610 ° C
, And then hot-rolled to a thickness of 2.1 mm. The hot rolling starts in a temperature range of 450 to 550 ° C., and the material temperature at the end of the hot rolling is 300.
The temperature was adjusted to be in the range of ３３０330 ° C.

The conductivity of the hot-rolled sheet was measured by a sigma tester, and then each hot-rolled sheet was cold-rolled to a sheet thickness of 0.3 mm to obtain test materials. The yield strength after heating (at 205 ° C. for 10 minutes) was measured, and the compound distribution, moldability (ironing moldability-DI moldability) can strength and corrosion resistance were measured and evaluated based on the following methods.

(1) Compound distribution: The surface of the plate is subjected to electrolytic polishing and etching treatment, and the surface is measured by an image analyzer (Luzex III (U), manufactured by Nireco). (2) Formability: 100 cans were made from the test material, and the success rate at that time and the appearance were evaluated by visual observation. In addition,
In Table 1, ◎ indicates that all the cans (100 cans) were successful and there was no appearance defect, ○ indicates that all the cans (100 cans) were successful but had poor appearance, and Δ indicates that 1 to 5 cans were broken. Showing things,
X shows that it broke beyond 5 cans.

(4) Can body strength: The can bottom pressure of the cans made was measured, and those that were equal to or higher than the withstand pressure of commercially available cans were evaluated as ○, and those reduced by 20 KPa were evaluated as Δ, A sample having a further decrease was designated as x. (5) Corrosion resistance: NaCl (1000 pp)
m) + citric acid (0.3%) solution, keeping this solution at a temperature of 90 ° C. for 5 minutes, pour into bottle with test material,
After sealing and leaving at a temperature of 40 ° C. for 720 hours, the corrosion weight loss is measured.
, And those exceeding 3% were evaluated as x. Table 2 shows the measurement and evaluation results.

As can be seen from Table 2, the test materials (Nos. 1 to 12) satisfying the conditions of the present invention are all excellent in the quality and strength of the can body, and are subject to the fluctuation of Si which is likely to be a problem when recycling UBC. It is possible to cope with it.

[0034]

[Table 1]

[0035]

[Table 2]

Comparative Example Each of the aluminum alloys having the component compositions shown in Table 3 (compositions shown in Nos. 13 to 22) was processed in the same steps as in Example 1 to produce test materials. For the test material, the compound distribution, moldability (ironing formability-DI moldability), can body strength and corrosion resistance were measured in the same manner as in Example 1.
evaluated. Further, as in Example 1, the electrical conductivity of the hot-rolled sheet was measured. Table 4 shows the measurement and evaluation results. In Tables 3 and 4, those outside the conditions of the present invention are underlined.

[0037]

[Table 3]

[0038]

[Table 4]

As shown in Table 4, none of the test materials (Nos. 13 to 22) which do not satisfy the conditions of the present invention can clear all of the conditions of can body quality and strength, and UBC is recycled. Doing so will cause problems. That is, the test material No. In Test Nos. 13 and 14, the required strength of the can was not obtained because the amount of Mg was insufficient. No. 14 is inferior in ironing formability.

Test material No. No. 15 has too much Mg content, so ironing formability and corrosion resistance are inferior. Test material No. 16
The required strength of the can was not obtained due to the small amount of Mn, and the ironing formability was also inferior because the compound of 1 to 15 μm was small. Test material No. Since Nos. 17 and 18 have a large Mn content, a compound exceeding 15 μm is present and ironing formability is poor.

Test piece No. 19 has few compounds of 1 to 15 μm. In No. 20, ironing formability is inferior because the area ratio of the α phase is low. Further, the test material No. 19,
No. 20 has a small amount of Si and is inferior in recyclability. Test piece N
o. Test pieces Nos. 21 and 22 were inferior in corrosion resistance due to a large amount of Si. In No. 22, the required can body strength cannot be obtained because the Mg content is further small.

[0042]

According to the present invention, when used as a can body, even if the amount of Si in the UBC regenerated lump fluctuates, the Si mixed in the recycling process can be effectively used.
While increasing the α-phase compound to prevent seizure, while maintaining the quality and performance of the can at least at the current level,
A highly formable aluminum alloy plate having high iron formability, sufficient strength of a can body, no appearance defect after iron forming, sufficient corrosion resistance, and excellent recyclability is provided.

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Claims (3)

[Claims] 1. Mn: 0.8 to 1.2% (mass%, the same applies hereinafter), Cu: 0.15 to 0.25%, Fe: 0.25
-0.6%, Si: 0.30-0.50%, and Mg in an amount obtained by substituting the content percentages of the above Mn, Cu, Fe and Si into the following formula. , And Zn: 0.
A highly recyclable high formability aluminum alloy sheet comprising 25% or less and Ti: 0.01 to 0.10%, with the balance being Al and impurities of 0.15% or less in total. (137.5 + 88.5 × Si% −53.0 × Mn% −
167.6 × Cu% −24.6 × Fe%) / 71.9 ≦
Mg% ≦ (167.5 + 88.5 × Si% −53.0 ×
(Mn% -167.6 × Cu% −24.6 × Fe%) / 7
1.9 2. Mn: 0.8-1.2%, Cu: 0.1
5 to 0.25%, Fe: 0.25 to 0.6%, Si:
0.30 to 0.50%, and the following formula
The amount of M obtained by substituting the contents% of n, Cu, Fe and Si
g: Zn: 0.25% or less, Ti: 0.0
1 to 0.10%, the balance being Al and 0.15 in total
% Of a highly formable aluminum alloy sheet having excellent recyclability, characterized by being composed of impurities of not more than%. Mg% = (ABYS-102.5 + 88.5 × Si% −
53.0 × Mn% −167.6 × Cu% −24.6 × F
e%) / 71.9 (ABYS: desired strength (MPa) after heat-treating the aluminum alloy plate at 205 ° C. for 10 minutes and a numerical value between 240 and 270) 3. A process for producing an aluminum alloy plate by subjecting an aluminum alloy having the component composition according to claim 1 or 2 to ingot by DC casting, through homogenization treatment, hot rolling, and cold rolling. Conductivity after hot rolling (IACS
%) Is 41.0% or more, among the compounds present on the sheet surface after cold rolling, no compound exceeding 15 μm is present, and the area ratio of the compound of 1 to 15 μm is 5.0% or more. The area ratio of the α-phase compound (Al—Mn—Fe—Si-based compound) is 50% or more, and Mg ₂ Si
A method for producing a highly formable aluminum alloy sheet having excellent recyclability, wherein the area ratio of a phase is 1.0% or less.