JP2956038B2 - Al alloy plate for drawing cups excellent in suppressing distortion pattern and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Al alloy plate for drawing a food can, a beverage can, and other objects, and a method for producing the same.

[0002]

2. Description of the Related Art When drawing is performed using an Al alloy plate, a strain pattern called a stretcher strain mark (SS mark) or a Luders mark may be formed on the side wall of the drawing cup. This distortion pattern is caused by the state of deformation stress at the time of molding, and is caused by uneven deformation in the circumferential direction of the side wall. The strain pattern generated in this way not only impairs the appearance of the cup side wall, but when there is a coating on the plate surface, the coating film is cut off, causing a coating defect such as peeling, and when the degree is large, May lead to cracking of the material.

[0003] Conventionally, in the drawing of food cans, beverage cans, and other objects, alloys such as 5052 are disclosed in
As shown in JP-A-288056 and JP-B-61-7465, a plate manufactured by a manufacturing method including hot rolling, (cold rolling), intermediate annealing, and final cold rolling is used. .

[0004]

However, the conventional 505
The alloy 2 has a problem that a strain pattern is formed on the side wall of the drawing cup. Of course, this problem can be avoided by lowering the strength, but this does not meet the demand for thinning.
Although the use of 3004 alloy used for beverage cans is also conceivable, a strain pattern is generated at the same high strength, and when the strength is reduced, high-temperature treatment is required, and the stability of actual production is lacking. Further, since the 3004 alloy contains Fe and Cu (Fe: 0.4%, Cu: 0.2%), there is a problem in corrosion resistance.

[0005] Therefore, the conventional materials and manufacturing methods are insufficient for suppressing the generation of strain patterns. From this viewpoint, it is necessary to develop a material which is easily deformable at the time of molding, has a strength suitable for moldability, and further considers corrosion resistance and productivity.

An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide an Al alloy plate for a draw cup which is excellent in suppressing a strain pattern by drawing and a method for producing the same.

[0007]

Means for Solving the Problems In order to solve the above problems, the present inventors have focused on the fact that the state of occurrence of a strain pattern when the strength is changed by heat treatment using an existing material is different, and Al for squeeze cup with excellent suppression
We worked to develop an alloy plate.

It is generally considered that the strain pattern is caused by dislocation fixation by Mg atoms dissolved in the material structure.

Therefore, the present inventors first investigated several materials having different Mg contents. As a result, with respect to the material after the cold rolling, it was found that the strain pattern occurred regardless of the Mg amount, and the degree of the strain pattern did not correspond to the Mg amount. In addition, it was found that, for those subjected to finish annealing after cold rolling, a material having a higher annealing temperature and a lower material strength has a relatively reduced strain pattern.
Furthermore, when the crystal grain size was changed for alloys of the same component and the strain pattern was examined, the smaller the crystal grain size was, the smaller the degree of the strain pattern was.
The strain pattern was very slight after annealing the material of μm or less. Attempts were made to adjust the crystal grain size by chemical components. When the grain size was reduced to 25 μm or less, the strain pattern was reduced. In that case, Fe, an element that forms the nucleus of recrystallization,
Is required, resulting in poor corrosion resistance. Also, with respect to corrosion resistance, addition of a large amount of Cu is not preferable. To suppress the decrease in the corrosion resistance and obtain fine crystal grains, the addition of Mn is effective. However, if the addition amount of Mn is excessive, the formability is reduced.

From these results, the following has been found. The strain pattern in the draw forming is not due to dislocation fixation due to Mg atoms, but due to uneven deformation in the circumferential direction of the draw cup during forming. In order to suppress the distortion pattern, it is necessary to refine the crystal grains. However, considering corrosion resistance, the addition of Fe and Cu should be regulated.

Therefore, the purpose of the present invention is to reduce the non-uniform deformation in the circumferential direction at the time of drawing by reducing the size of the crystal grains based on such knowledge, and to improve the corrosion resistance for application to food cans, beverage cans and the like. Required strength (200 to 2 in proof stress)
It has been found that the initial purpose can be achieved by adjusting the chemical composition so as to sufficiently obtain 60 N / mm ² ) and regulating the intermediate annealing conditions, the cold rolling conditions, and the finish annealing conditions.

That is, the present invention relates to Mg: 1.0-2.
0%, Mn: more than 0.80 to 1.50%, Fe: 0.10
０．２0.25% as an essential component, and if necessary, Cu ≦ 0.07%, Si ≦ 0.20%, Ti ≦ 0.20
% Of one or more kinds, the balance being Al and unavoidable impurities, and a proof stress of 200 to 260 N / mm.
² , the average crystal grain size observed from the surface is 25 to 40 μm
The gist of the present invention is an Al alloy plate for a draw cup, which is excellent in suppressing a strain pattern due to draw forming, wherein the m is m.

[0013] Further, the production method is such that an Al alloy ingot having the above-mentioned chemical components is subjected to a homogenizing heat treatment, then hot-rolled, cold-rolled at a rolling reduction of 60% or more, and then subjected to an intermediate annealing at a sheet temperature. At 400 to 500 ° C. for 10 minutes or less, and thereafter, a rolling reduction of 30 to 70 ° C.
% After cold rolling, it is subjected to finish annealing at a temperature of 200 to 260 ° C., in proof stress 200~260N / mm ^2, Table
Al with an average crystal grain size of 25 to 40 μm observed from the surface
It is characterized by obtaining an alloy plate .

Hereinafter, the present invention will be described in more detail.

[0015]

[Action]

First, the reasons for limiting the chemical components of the Al alloy in the present invention will be described.

Mg: Mg is an important element for imparting strength, and is an essential component in the present invention. At least 1.0% for use in food cans, beverage cans, etc.
If not added, sufficient strength cannot be obtained. However, if added in excess, the strength increases and non-uniform deformation due to an increase in the deformation force is caused.
It is. Therefore, the amount of Mg added is set in the range of 1.0 to 2.0%.

Mn: Mn is an important element that contributes to the strength and contributes to the refinement of crystal grains, which is most effective in suppressing the strain pattern, and also has the same effect as the refinement of the crystal grains in suppressing the strain pattern. Contributes to the increase of certain fine precipitates. Therefore, Mn is also an essential component in the present invention. An amount exceeding at least 0.80% for the effect of strength and grain refinement to be recognized
Must be added . However, excessive addition exceeding 1.50% causes a reduction in moldability. Therefore, the amount of added Mn is set to be in a range of more than 0.80 to 1.50%.

Fe: Fe is an element forming a nucleus of recrystallization, and the addition of Fe has a great effect of making crystal grains fine. At least 0.10% must be added in order for the effect of grain refinement to be recognized. Further, as the amount of addition increases, the crystal grains become finer,
Addition of more than 5% causes a decrease in corrosion resistance. Therefore, the amount of Fe added is in the range of 0.10 to 0.25%.

In the present invention, Mg, Mn, and Fe are essential components, but one or more of the following elements can be contained in an appropriate amount as needed.

Cu: The addition of Cu has a great effect on increasing the strength, but the excessive addition causes a decrease in corrosion resistance. Therefore, the added amount of Cu is set to 0.07% or less.

Si: The addition of Si has an effect on the formation of precipitates. However, if it is added excessively, the number of giant crystallized substances and the number of crystallized substances increases, leading to a reduction in formability. Therefore, the addition amount of Si is set to 0.20% or less.

Ti: Ti is an element effective for stabilizing the structure, but when added in a large amount, giant crystals are formed to lower the formability. Therefore, the addition amount of Ti is set to 0.20% or less.

Further, in the present invention, the average crystal grain size observed from the surface of the obtained Al alloy plate is regulated to 25 to 40 μm. This is because if the crystal grain size is larger than 40 μm during drawing, uneven deformation in the circumferential direction is liable to occur. To obtain a crystal grain size smaller than 25 μm, the amount of Fe added must be 0.25% or more. And the cold rolling reduction before the intermediate annealing must be greatly increased, which is a factor of cost increase.

Next, the manufacturing process of the present invention will be described.

After the Al alloy having the above chemical components is melted, cast and subjected to a homogenizing heat treatment, hot rolling is performed.

After hot rolling, cold rolling is performed. In the present invention, the control of the crystal grain size which contributes to the suppression of the strain pattern is performed by performing the cold rolling step including the following intermediate annealing. It is characterized by performing.

First, the cold rolling reduction before the intermediate annealing is 60%.
If it is less than 1, the crystal grains after the intermediate annealing become large, and it is likely to cause non-uniform deformation in draw forming. Further, since the formability which is a necessary property is affected, the cold rolling reduction before the intermediate annealing is 6%.
0% or more.

Next, intermediate annealing is performed.
It is performed in a continuous annealing furnace called L, and the conditions have a great influence on strength and formability. That is, the actual temperature of the sheet during annealing affects the recrystallization and the solid solution amount of Mg and Cu. If the temperature is less than 400 ° C., the recrystallization is not completed.
If Mg exceeds Cu, Mg and Cu form a solid solution to increase the strength, so that the deformation force increases, which is disadvantageous for the strain pattern. Further, the recrystallized grain size becomes large, and the effect of suppressing the strain pattern cannot be obtained. Therefore, the range of the plate temperature is 400 to 500 ° C. The retention time affects the amount of solid solution of recrystallization and Mg and Cu, and varies depending on the plate temperature.
Within minutes. The heating / cooling rate may be 100 ° C./min or more.

[0030] Cold rolling after intermediate annealing is a condition that greatly affects the strength. If the rolling reduction is less than 30%, sufficient strength cannot be obtained. Although an increase in the rolling ratio is effective for improving the strength, when the rolling ratio exceeds 70%, the formability is reduced and ears are remarkably generated, and the yield after drawing is deteriorated. Therefore, the cold rolling reduction after the intermediate annealing is 30 to 7
The range is 0%.

After the cold rolling, finish annealing is performed. Finish annealing is a heat treatment that plays an important role in suppressing strain patterns. When the annealing temperature is 200 ° C. or higher, sub-grains are generated, and the dislocations entangled in the crystal grain boundaries are arranged by cold rolling, and the dislocation density is reduced. However, 2
If the temperature is higher than 60 ° C., a rapid decrease in strength is caused, and the stability in actual production is lacking. Therefore, the finish annealing temperature is 200
~ 260 ° C.

The proof stress of the product plate obtained through these steps is regulated to ²⁰⁰ to 260 N / mm ² . This is because the internal pressure varies depending on the type of the contents, the retort treatment, and the like, and deformation occurs at 200 N / mm ² or less. Further, when it is 260 N / mm ² or more, generation of a distorted pattern becomes remarkable.

Next, examples of the present invention will be described.

[0034]

Embodiment 1

Table 1

[Table 1] The aluminum alloy ingot having the chemical components shown in Table 1 was kept at a temperature of 590 ° C. for 8 hours as a homogenizing heat treatment, and thereafter, was hot-rolled to a thickness of 2.0 mm.

Next, each specimen was cold-rolled to a sheet thickness of 0.55 mm, and the sheet thickness was increased to 430 ° C./min in a continuous heating annealing furnace at a heating / cooling rate of 270 ° C./min.
A heat treatment at 0 ° C. and a holding time of 0 seconds was performed, and the sheet thickness was reduced to 0.22 mm by cold rolling. After further cold rolling, 230 ℃ × 2h
The finish annealing of r was performed. In addition, assuming that these materials are applied to a food can, baking treatment was performed at 200 ° C. for 20 minutes.

Table 2 shows the results of an examination of the material properties of the test material having a product plate thickness of 0.22 mm after the baking treatment and the characteristics of the product.

[Table 2] Shown in

The test method for the cup characteristics is as follows. In the drawing cup test, a drawing hat with a height of 26 mm was created with a blank diameter of 127 mmφ and a punch diameter of 78 mmφ,
The evaluation was made based on the roughness of the flange portion (Rt value: the more remarkable the strain pattern, the larger the Rt value). Further, a deep drawing cup was prepared, and the occurrence of the strain pattern was visually evaluated. The limit drawing ratio (LDR: blank diameter / punch diameter) was determined by using an Erichsen tester and changing the blank diameter with a 33 mmφ cylindrical punch.

From Table 2, the following is considered. No. 1, which is an example of the present invention, has a suitable crystal grain size, shows almost no distortion pattern, is good, and has appropriate strength and moldability. On the other hand, No. 2, No. 3, and No. of the comparative examples.
In No. 7, although the strength and the formability are appropriate, the strain pattern is remarkably recognized because the crystal grain size is large. Comparative Example N
Nos. 4 to 5 cause excessive decrease in formability due to increase of precipitates due to excessive addition of Fe and Mn. Further, No. 4 has a remarkable decrease in corrosion resistance, and No. 6 has good crystal grain size and strain pattern, but does not have sufficient strength.

[0040]

Example 2 An Al alloy ingot having the same composition as that of No. 1 in Table 1 was subjected to homogenization treatment and hot rolling in the same manner as in Example 1;

[Table 3] A plate was manufactured under the following manufacturing conditions, and the mechanical properties, moldability, crystal grain size, Rt value, and occurrence of strain patterns were determined. Table 4 shows the results.

[Table 4] Shown in

As is evident from Table 4, the Al alloy sheet A produced by the production method of the present invention shows proper yield strength, crystal grains, and a good strain pattern. On the other hand, although C, F, and I of the comparative examples have good strain patterns and good moldability, the strength is too low. Further, B, D, and E of the comparative examples satisfy the strength and the moldability, but cause deterioration of the strain pattern due to the coarsening of the crystal grain size. In Comparative Examples G and H, the strength was too high and the strain pattern was deteriorated.

[0042]

As described in detail above, according to the present invention,
In food cans, beverage cans, and other objects, it is possible to suppress the occurrence of distortion patterns on the side walls due to drawing, and it has sufficient moldability and strength required for the properties after the product. In addition, manufacturing aspects (stability, cost) are also excellent.

Continuation of the front page (56) References JP-A-2-290953 (JP, A) JP-A-51-116105 (JP, A)

Claims (5)

(57) [Claims] (1) Mg: 1.0% by weight (hereinafter the same).
~ 2.0%, Mn: more than 0.80 ~ 1.50%, Fe:
0.10 to 0.25% as an essential component, the balance being A
1 and unavoidable impurities, and has a proof stress of 200 to 2
An Al alloy plate for a draw cup excellent in suppression of a strain pattern by draw forming, wherein the average crystal grain size observed from the surface is 60 N / mm ² and 25 to 40 μm. 2. The Al alloy plate for a drawing cup according to claim 1, further comprising Cu ≦ 0.07%. 3. The Al alloy plate for a draw cup according to claim 1, further comprising Si ≦ 0.20%. 4. The Al alloy plate for a drawing cup according to claim 1, further comprising Ti ≦ 0.20%. 5. An Al alloy ingot having a chemical component according to any one of claims 1 to 4, which is subjected to a homogenizing heat treatment, hot-rolled, and cold-rolled at a rolling reduction of 60% or more. As the intermediate annealing, continuous annealing is performed under the condition that the sheet temperature is maintained at 400 to 500 ° C. within 10 minutes, and then the rolling reduction is 30
After cold rolling at ~ 70%, finish annealing is performed at a temperature of 200 ~ 260 ° C, and the proof stress is 200 ~ 260N / mm ^2.
And the average crystal grain size observed from the surface is 25 to 40 μm
A method for producing an Al alloy plate for a draw cup, which is excellent in suppressing a strain pattern by drawing and forming, wherein the Al alloy plate is obtained.