JP3218099B2 - Method for producing aluminum alloy sheet with low ear ratio and excellent formability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an aluminum alloy hard plate excellent in ear ratio, strength and formability, and more specifically, cans such as DI cans, DR cans and DRD cans. The present invention relates to a method for manufacturing an Al-Mn-Mg-based aluminum alloy hard plate suitable for a body material.

[0002]

2. Description of the Related Art In recent years, aluminum alloy hard plates used for can materials have been reduced in thickness and strength. This is due to economic demands such as reducing material costs by using thinner plates having higher strength. JI
Since the S3004 alloy hard plate has relatively good formability even when cold-rolled at a high rolling ratio in order to increase the strength, it is often used as a can body material conventionally.
This JIS 3004 alloy hard plate is hot-rolled according to a conventional method after homogenization treatment, and then subjected to intermediate annealing with or without cold rolling in many cases. This intermediate annealing is performed by a box-type annealing furnace. 300 ° C using (batch furnace)
In this case, the required strength cannot be obtained unless the final cold rolling reduction is 70% or more. However, this alloy has a relatively high cold rolling reduction. However, the ear rate is not so large. On the other hand, with the spread of continuous annealing furnaces (CALs) in recent years, it has become possible to increase the ultimate temperature and rapid cooling when performing intermediate annealing using the CALs.
A process has been proposed in which high strength can be obtained even with a small final cold rolling reduction. However, in this method, if the cold rolling reduction is increased, the ear ratio becomes unacceptably large.

[0003]

The advantage of the conventional batch annealing material is that the ear rate is low. But,
In the case of batch annealed materials, the strength decrease during baking is large, so in order to secure the strength after baking, the strength of the can body at the time before DI molding must be high,
As a result, there arises a problem that moldability during DI molding is deteriorated. On the other hand, the advantage of the CAL annealed material is that the strength of the can body before the DI forming is not so high because the strength after the paint baking can be sufficiently obtained even if the strength of the can body before the DI forming is small because the strength of the solution annealing effect is small. Is to be better. However, if the cold rolling reduction after the intermediate annealing is increased, there is a problem that the ear ratio becomes unacceptably large. An object of the present invention is to solve the above problem and to provide a material which has a low ear ratio and improves overall formability even when subjected to intermediate annealing by CAL.

[0004]

In order to achieve the above object, the present inventors have conducted intensive studies on a production method having both the ear ratio of batch annealing and the solution heat effect of CAL annealing.
The present invention has been made.

That is, in the present invention, Mg: 0.5% by weight
2.0%, Mn: 0.5 to 1.8%, Fe: 0.1 to
0.7%, Ti: 0.005 for refining and stabilizing the structure
To 0.20% alone or B: 0.0001 to 0.1%.
0.05% to 0.5%.
5%, Cu: 0.05-0.5%, Cr: 0.05-
An aluminum alloy ingot containing one or more of 0.3% and Zn: 0.1 to 0.5% and the balance of Al and impurities is soaked at 560 to 620 ° C. according to a conventional method, and then heated. Cold rolling, and then a heating / cooling rate of 0.5 ° C./s or more, 290 to 40
A temperature of 0 ° C., and a period of time in this temperature range of 10 ° C.
Minutes, and then cold-rolled at a rolling rate of 5 to 30%, and then at a heating / cooling rate of 1 ° C / s or more, at an ultimate temperature of 400 to 600 ° C, and 400 to 600 ° C.
An aluminum alloy having a low ear rate and excellent formability, which is subjected to recrystallization annealing in which the time of exposure to a temperature range of 10 ° C. is within 10 minutes, and then to cold rolling at a rolling ratio of 40% or more. This is a method for manufacturing a plate.

[0006]

[Action]

First, the reasons for limiting the components in the rolled aluminum alloy sheet of the present invention will be described. The following alloy components are added for the purpose of increasing the strength of aluminum and controlling the ear ratio and formability. Mg: Mg is expected to undergo age hardening due to precipitation of Mg ₂ Si or Al—Cu—Mg due to coexistence with Si · Cu, and is subjected to intermediate annealing that brings a solution effect as in the present invention.
In particular, it is effective in suppressing a decrease in strength after baking. Further, Mg alone is an element having the effect of solid solution strengthening. As described above, it is an indispensable element for improving the strength. However, when the Mg content is less than 0.5%, its effect is small, and when it is added more than 2%, there is no problem in drawing, but work hardening is easy. In order to become, the redrawability and the ironing property are deteriorated. Therefore, the Mg content is in the range of 0.5 to 2%. Mn: Mn is an element that contributes to improving strength and is effective for improving formability. In particular, Mn is particularly important in the can body material, which is an application aimed at by the present invention, because ironing is performed. In the ironing of an aluminum alloy plate, an emulsion type lubricant is usually used. Mn
In the case where the amount of the system crystallization is small, the lubricating ability is insufficient only with the emulsion type lubricant even if the emulsion type lubricant has the same strength, and poor appearance such as abrasion or galling called galling occurs. This galling phenomenon depends on the size of
It is known that the amount and type are affected, and Mn is an element indispensable for properly forming the crystallized product. Mn
If the amount is less than 0.5%, the solid lubrication effect of the Mn compound cannot be obtained, and if it exceeds 1.8%, MnAl
The primary crystal giant intermetallic compound of ₆ is crystallized, and the formability is significantly impaired. Therefore, the amount of Mn is set to 0.5 to 1.8%. Fe: Fe is an element that promotes crystallization and precipitation of Mn, and is necessary for controlling the amount of Mn solid solution in the aluminum matrix and the dispersion state of the Mn-based insoluble compound. A necessary condition for obtaining an appropriate state of a compound or the like is the addition of Fe according to the amount of Mn added. If the Fe content is less than 0.1%, it is difficult to obtain a proper compound dispersion state. If the Fe content exceeds 0.7%, a primary crystal giant compound is easily generated together with the added Mn, and the formability is significantly impaired. . Therefore, the amount of Fe is 0.1
To 0.7%. If the amount of (Fe + Mn) exceeds 2%, a primary crystal giant compound is likely to be generated, and the formability is significantly impaired. Therefore, the amount of (Fe + Mn) is desirably 2% or less. Ti, B: In ordinary aluminum alloys, a small amount of Ti and B is added for refining and stabilizing ingot crystal grains. In the present invention, Ti: 0.0
0.05 to 0.20% alone or B: 0.0001 to
Add with 0.05%. If the Ti content is less than 0.005%, the effect cannot be obtained, and if it exceeds 0.2%, the primary crystal T
iAl ₃ is crystallized to inhibit the formability. Therefore Ti
The amount ranges from 0.005 to 0.2%. Also, when B is added together with Ti, the effect of refining and stabilizing the ingot crystal grains is improved. However, if the B content is less than 0.0001%, the effect is not obtained. If the B content exceeds 0.05%, coarse particles of TiB ₂ are mixed and formability is impaired. Therefore, the B content added with Ti is 0.0001 to 0. 0.05%. Cu: In the present invention, an improvement in strength due to the solution effect of Cu can be expected. That is, the addition of Cu makes it possible to improve the strength by utilizing age hardening that occurs during the precipitation process of the Al-Cu-Mg-based precipitate during the baking treatment. If the Cu content is less than 0.05%, the effect cannot be obtained.
When added in excess of the above, age hardening is easily obtained, but becomes too hard to inhibit moldability. Therefore, Cu
The amount is 0.05-0.5%. Si: By adding Si, an improvement in strength can be expected by age hardening with a Mg ₂ Si-based compound. If the Si content is less than 0.05%, the effect cannot be obtained. If the Si content is more than 0.5%, age hardening can be easily obtained, but the material becomes too hard and the moldability is impaired. Therefore, the amount of Si is 0.0
5% to 0.5%. The addition of Zn: Zn is intended to improve the strength by aging precipitation of Mg ₂ Zn ₃ Al _{2. If} the Zn content is less than 0.1%, there is no effect, and if it exceeds 0.5%, the corrosion resistance is deteriorated. It is necessary to regulate below this value. Therefore,
The amount of Zn is 0.1-0.5%. Cr: Cr is an element effective for improving the strength.
If it is less than 5%, the effect is small, and if it exceeds 0.3%, large crystallized substances are formed, resulting in a decrease in moldability, which is not preferable. Therefore, the amount of Cr is set to 0.05 to 0.3%. The balance of each of the above components is Al and inevitable impurities.

Next, the manufacturing process according to the present invention will be described. Casting: An aluminum alloy ingot having the above-described alloy composition is produced by a DC casting method (semi-continuous casting method) according to a conventional method. Soaking: Next, the ingot is subjected to preheating before hot rolling also serving as a homogenizing treatment, or is subjected to heating as a homogenizing treatment and then to preheating before hot rolling. This homogenization treatment is an effective treatment for improving the strength, toughness, deep drawing workability of the final plate, reducing the variation in ear ratio, etc.
If the temperature is lower than 560 ° C., sufficient homogenization cannot be obtained.
If the temperature exceeds ℃, swelling may occur on the surface of the ingot, so the soaking temperature is 560 to 620 ° C. Also, if the holding time is less than 1 hour, sufficient homogenization cannot be obtained, so that the holding time is desirably 1 hour or more. The upper limit of the holding time may be appropriately set in consideration of productivity. Hot rolling: The conditions for hot rolling are not particularly limited.
Considering the hot ductility, a rise temperature of 230 ° C. or more is preferable. Further, the thickness of the upward plate is preferably 10 mm or less in consideration of the winding property. Cold rolling: In the case of a structure that has been recrystallized after hot rolling, it is necessary to perform cold rolling at a rolling ratio of 30% or more in order to obtain a uniform recrystallized structure by annealing in the next step. is there. First-stage annealing: (partial recrystallization annealing) In the present invention,
This first-stage annealing is characterized in that it is not completely recrystallized, but is only partially recrystallized and usually promotes the crystallization of the R direction of the high ear component. A such as the alloy of the present invention
In an l-Mn-Mg-based alloy, a large number of crystallized compounds usually having a size of about several μm are present, and strain is accumulated in the vicinity of the crystallized material by cold rolling, which tends to recrystallize. Therefore, by performing annealing in which the heating / cooling rate is 0.5 ° C./s or more, the ultimate temperature is 290 to 400 ° C., and the time maintained in the temperature range is within 10 minutes, preferentially from the vicinity of the crystallized material. Recrystallization with the R orientation starts. The recrystallization rate is preferably from 10 to 80%. Heating / cooling rate is 0.5
When the temperature is lower than ° C / s, Mg ₂ Si, Al ₂ CuM
g and αAlMnSi or Al ₆ Mn are precipitated, which is not preferable because the growth of a crystal having a Cube orientation is suppressed during the second annealing. If the annealing temperature is lower than 290 ° C., recrystallization does not proceed sufficiently, and if the temperature exceeds 400 ° C., recrystallization hardly occurs, which is not preferable. Therefore, the annealing temperature is 290-400 ° C., preferably 3
20 to 380 ° C. Cold rolling: After the partial recrystallization annealing, cold rolling is performed at a rolling rate of 5 to 30%, and a slight strain is applied to a portion recrystallized by the first-stage annealing. If the rolling reduction is less than 5%, the strain to be imparted is not sufficient, and if it exceeds 30%, a strong strain is applied to the recrystallized portion. And preferential generation and growth of the Cube orientation cannot be obtained. Therefore, the rolling rate is 5-30%
And Second-stage annealing: (Complete recrystallization annealing) Since the strain in the vicinity of the crystallized material has been reduced by the first-stage annealing, the vicinity of the crystallized material is easily recrystallized in the second-stage annealing. It cannot be a nucleus, and instead, recrystallization proceeds preferentially from the dislocation accumulation portion in the matrix introduced by the cold rolling in the previous step. The orientation of the crystal grains generated from this portion is called the Cube orientation and has a low ear component. In other words, the recrystallization grains having Cube orientation are preferentially generated by the second annealing, and grow to include the vicinity of the crystallized substance which cannot be recrystallized, resulting in a recrystallized structure having many Cube orientations as a whole. As a whole, the tissue has a low ear rate. Tokiko Sho 60-3
No. 7186 describes that this second-stage annealing is performed in a batch type. However, in the present invention, this annealing is performed at a high heating rate of 1 ° C./s or more as in a CAL (continuous annealing furnace). It is desired to improve the strength by a solution effect by a solid solution of a metal element such as Cu, Mg, and Si by having a cooling rate and a reaching temperature of 400 to 600 ° C. That is, although the strength at the time of DI molding is not so strong, an aluminum alloy sheet with a small decrease in strength due to age hardening can be obtained even when paint baking is performed. Therefore, since the strength during DI molding is not so high, the moldability is good, and the strength during DI molding is lower than that of batch-type annealed material, so the strength during DI molding is lower than the batch type annealed material because the strength decrease after baking is small. Finally, an aluminum alloy plate having a sufficient strength can be obtained. If the ultimate temperature is less than 400 ° C., a sufficient recrystallized structure cannot be obtained,
In addition, although a higher temperature can be expected to improve the strength by the solution effect, if the temperature is higher than 600 ° C., there are disadvantages in production such as softening due to eutectic melting, and the appearance of the product may be impaired by partial melting. . Therefore, the ultimate temperature is set to 400 to 600 ° C. If the cooling rate is slower than 1 ° C./s, the solid solution alloy element will precipitate during the cooling process, and the degree of strength improvement due to the solution effect will be reduced. Therefore, the cooling rate is set to 1 ° C./s or more. If the temperature is higher than 400 ° C., the surface oxidation proceeds remarkably, and it is necessary to shorten the holding time at 400 ° C. or higher. If the time is longer than 10 minutes, the oxide film formed on the surface impairs the cold rolling property after the end of the annealing and the appearance of the product. Therefore, the time of exposure to the temperature range of 400 to 600 ° C. including the heating, holding, and cooling periods is set to 10 minutes or less. After reaching the above temperature, it may be cooled immediately without holding. In order to shorten the above-mentioned time and for that purpose, it is better that the heating rate is high, and 1 ° C./s
The above heating rate is set. Cold rolling: After the above-mentioned annealing, cold rolling is performed.
If not more than 0%, the required strength cannot be obtained. In addition, improvement of deep drawability can be expected by performing final annealing at about 100 to 200 ° C. as necessary.

[0009]

EXAMPLES Aluminum alloys having the chemical components shown in Table 1 were rolled and heat-treated by the production methods shown in Table 2 to prepare samples. In Table 2, the column of soaking shows temperature × retention time, the column of hot rolling and cold rolling shows sheet thickness (mm), and the column of intermediate annealing shows temperature × retention time. However, a holding time of 0 indicates that cooling was started immediately (without holding) after the temperature reached. The heating / cooling rate of CAL was about 20 ° C./s, and the heating / cooling rate of the batch was about 35 ° C./h. Hereinafter, each will be described. No. 1 is a conventional example in which annealing was performed only once by CAL. No. 2 is a conventional example in which batch annealing was performed after hot rolling without performing cold rolling. No3 is 1
This is a comparative example in which the stage was batch annealing and the second stage was batch annealing. No. 4 is a comparative example in which the first step was performed by batch annealing and the second step was performed by CAL annealing. No. 5 is a comparative example in which the first stage was subjected to CAL annealing at a temperature lower than the range of the present invention and the second stage was also subjected to CAL annealing. No. 6 is an example of the invention in which the first step was CAL annealing and the second step was CAL annealing. In No. 7, the first stage was a CA having a higher temperature than the range of the present invention.
This is a comparative example in which L annealing was performed and the second step was also performed by CAL annealing. No. 8 is a comparative example in which the reduction ratio of the cold rolling during the first and second stages of CAL annealing is higher than the range of the present invention. N
o9 is a comparative example in which the same step as in the present invention was performed, but the second-stage annealing was performed by high-temperature batch annealing, and the time of exposure to a temperature range of 400 to 600 ° C. exceeded 10 minutes.

[0010]

[Table 1]

[0011]

[Table 2]

The tensile strength (TS: N / mm ² ), proof stress (YS: N / mm ² ) of the base plate and the plate after heat treatment at 200 ° C. for 20 minutes equivalent to coating baking,
The elongation (EL:%) was examined, and the ear ratio was measured by deep-drawing a 66 mmφ circle with a clearance of 30% using a punch of 38 mmφ and a shoulder R2.5 mm for the original plate. In addition, actual DI molding was performed to observe continuous formability and appearance of the DI can. The appearance was determined by the presence or absence of a flow line-like appearance defect along the rolling direction of the can side wall. Table 3 shows the results.
Shown in

[0013]

[Table 3]

Hereinafter, each of them will be described. In the conventional example in which the annealing of No. 1 was performed only once by CAL, the strength of the base plate and the strength after baking were sufficient, but the ear ratio was as high as 5%. In the conventional example in which batch annealing was performed after hot rolling without performing cold rolling of No. 2, although the ear ratio was as low as 3%,
The strength of the base plate is high and it is difficult to form, and the change in strength due to baking is large in tensile strength, and the strength is reduced by 13 N / mm ² . On the other hand, in the invention example of No. 6, the strength of the original plate at the time of DI molding was 300 N / mm ² in tensile strength and ² in proof stress.
It is 82 N / mm ^2, which is about the same as that of the conventional material No. 1 and easy to mold. In addition, after baking, the tensile strength is improved by 5 N / mm ² , indicating good characteristics that the strength after baking, which originally requires strength, is sufficiently high. The ear ratio is 3 to 5% in the conventional example, while the invention example shows an extremely low value of 1.5%. Further, there is no problem in the DI property, and no defect is observed in the appearance of the DI molded can. As described above, in the invention examples, the original plate strength is soft, so that the moldability is good, the required strength is sufficiently satisfied after baking, the ear ratio is extremely low, and the DI property and the appearance are poor. ing. In the comparative example in which the first step of No. 3 was batch-annealed and the second step was also batch-annealed, the tensile strength of the original plate was too high and the formability was poor, and the tensile strength was significantly reduced by baking. And there is a problem in strength. In the comparative example in which the first step of No. 4 was batch-annealed and the second step was CAL-annealed, the strength and DI properties after the base plate and baking, and the DI properties and DI can appearance were almost the same as those of the invention example, or the ear ratio was slightly large. Indicates the value. N
The comparative example in which the first step of o5 was CAL annealing at a lower temperature than the range of the present invention and the second step was also CAL annealing was inferior in ear ratio to No. 4 like No. 4. The first stage of No. 7 was subjected to CAL annealing at a higher temperature than the range of the present invention, and the second stage was also CA.
In the comparative example performed by L annealing, the strength improvement by baking is larger than that of the invention example, but the ear ratio is inferior to that of the invention example. In Comparative Examples in which the cold rolling reduction ratio between the first and second CAL annealings of No. 8 was higher than the range of the present invention, the ear ratios were inferior to those of the invention examples, like Nos. 5 and 7. In the comparative example in which the process of No. 9 is the same as that of the present invention, but the second-stage annealing is performed by high-temperature batch annealing, and the time of exposure to the temperature range of 400 to 600 ° C. exceeds 10 minutes, the ear ratio is different from that of the conventional example. Same, but the original plate strength is too high,
Conversely, the strength after baking is greatly reduced, and there is a problem in strength, and a flow line appearance defect occurs in DI molding.

[0015]

[Effect] The aluminum hard plate for forming manufactured by the present invention is particularly suitable for use in which a baking treatment is applied to a can material or the like, a low deep drawing ear, high strength is obtained, and formability is obtained. Is also excellent. That is, as described in detail, according to the present invention, the strength at the time of DI forming is not so high, so that the formability is good, and the strength is improved by paint baking treatment, which is an ideal strength as a forming aluminum alloy. It is possible to provide an aluminum alloy plate having characteristics and an extremely low ear ratio. Therefore, according to the production method of the present invention, an aluminum alloy plate suitable for a can body such as a DI can, a DR can and a DRD can can be obtained.

────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI C22F 1/00 686 C22F 1/00 686Z 691 691A 691B 693 693A 693B

Claims (1)

(57) [Claims] 1. Mg: 0.5% by weight (hereinafter the same).
2.0%, Mn: 0.5-1.8%, Fe: 0.1-
0.7%, Ti: 0.005 for refining and stabilizing the structure
To 0.20% alone or B: 0.0001 to 0.1%.
0.05% to 0.5%.
5%, Cu: 0.05-0.5%, Cr: 0.05-
An aluminum alloy ingot containing one or more of 0.3% and Zn: 0.1 to 0.5% and the balance of Al and impurities is soaked at 560 to 620 ° C. according to a conventional method, and then heated. Cold rolling, and then a heating / cooling rate of 0.5 ° C./s or more, 290 to 40
A temperature of 0 ° C., and a period of time in this temperature range of 10 ° C.
Minutes, and then cold-rolled at a rolling rate of 5 to 30%, and then at a heating / cooling rate of 1 ° C / s or more, at an ultimate temperature of 400 to 600 ° C, and 400 to 600 ° C.
An aluminum alloy having a low ear rate and excellent formability, which is subjected to recrystallization annealing in which the time of exposure to a temperature range of 10 ° C. is within 10 minutes, and then to cold rolling at a rolling ratio of 40% or more. Plate manufacturing method.