JPH06101002A - Production of aluminum alloy sheet reduced in ear rate excellent in formability - Google Patents

Abstract

PURPOSE:To provide an aluminum allay sheet reduced in ear rate, excellent in formability, and most suitable for use in deep drawing, e.g. for can body material for DI can, DR can, DRD can, etc. CONSTITUTION:An ingot of an aluminum alloy having a composition consisting of 0.5-2.0% Mg, 0.5-1.8% Mn, 0.1-0.7% Fe, 0.005-0.20% Ti independently or together with 0.0001-0.05% B, further one or more kinds among 0.05-0.5% Si, 0.05-0.5% Cu, 0.05-0.3% Cr, and 0.1-0.5% Zn, and Al is subjected, by the ordinary method, to igniting at 560-620 deg.C and to hot rolling. Subsequently, the resulting alloy plate is cold-rolled and subjected to annealing at >=0.5 deg.C/s heating and cooling velocity under the condition where the length of time for holding at 290-400 deg.C ultimate temp. is regulated to <=10min. The resulting alloy sheet is further subjected to cold rolling at 5-30%, to recrystallization annealing at >=1 deg.C/s heating and cooling velocity while regulating the length of time where the alloy sheet is exposed to 400-600 deg.C ultimate temp. to <=10min, and then to cold rolling.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an aluminum alloy hard plate having excellent earing rate, strength and moldability, 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 cans have been made thinner and have higher strength. This is because of economical demands such as reduction of material cost by using a thin plate having higher strength. JI
The S3004 alloy hard plate has relatively good formability even when cold rolled at a high rolling rate in order to increase the strength, and thus is often used for a can body material from the past.
This JIS 3004 alloy hard plate is hot-rolled in accordance with a conventional method after homogenization treatment, and then is often subjected to intermediate annealing with or without cold rolling. This intermediate annealing is performed in a box-type annealing furnace. 300 ° C using (batch furnace)
It is carried out at a temperature of ~ 400 ° C for about 30 minutes to 3 hours. In this case, the required cold rolling rate cannot be obtained unless the final cold rolling rate is 70% or more, but this alloy has a relatively high cold rolling rate. However, the ear rate does not increase so much. On the other hand, with the widespread use of continuous annealing furnaces (CAL) in recent years, it is possible to raise the reached temperature and perform rapid cooling when performing intermediate annealing using this CAL, and by utilizing the solution treatment effect by this,
A process has also been proposed in which high strength can be obtained even if the final cold rolling rate is small. However, in the case of this method, the ear rate becomes unacceptably large when a large cold rolling rate is taken.

[0003]

The advantage of the conventional batch annealed material is that the ear ratio is low. But,
In the case of a batch annealed material, the strength decreases greatly during coating baking, so in order to secure the strength after coating baking, it is unavoidable to increase the strength of the can body material before DI molding.
As a result, there arises a problem that the moldability during DI molding deteriorates. On the other hand, the advantage of the CAL annealed material is that the strength reduction during coating baking is small due to the solutionizing effect, so even if the strength of the can body material before DI molding is not very high, the strength after coating baking is sufficient, so DI formability is improved. Is to get better. However, if the cold rolling rate after the intermediate annealing is increased, the ear rate becomes unacceptably high. It is an object of the present invention to solve the above problems and provide a material having a low earring rate and improving the overall formability even if the intermediate annealing by CAL is performed.

[0004]

In order to achieve the above object, the present inventor diligently studied a production method having both the earring rate of batch annealing and the solution treatment effect of CAL annealing.
The present invention has been completed.

That is, in the present invention, Mg: 0.5% by weight is used.
2.0%, Mn: 0.5 to 1.8%, Fe: 0.1
0.7%, Ti: 0.005 for microstructuring and stabilization
.About.0.20% alone or B: 0.0001 to 0.
0.05%, and further Si: 0.05-0.
5%, Cu: 0.05 to 0.5%, Cr: 0.05 to
An aluminum alloy ingot containing 0.3%, Zn: 0.1 to 0.5% of one kind or two kinds, and the balance of Al and impurities is soaked at 560 to 620 ° C. according to a conventional method, and then heated. Hot rolling, then cold rolling, then heating / cooling rate of 0.5 ° C / s or more, 290-40
The reached temperature of 0 ° C, the time to be kept in this temperature range is 10
Annealing is performed for no more than minutes, then cold rolling is performed at a rolling rate of 5 to 30%, then at a heating / cooling rate of 1 ° C./s or more, at an ultimate temperature of 400 to 600 ° C., and at 400 to 600
An aluminum alloy having a low earring ratio and excellent formability, which is characterized by performing recrystallization annealing for 10 minutes of exposure to a temperature range of ℃, and then performing cold rolling with a rolling rate of 40% or more. It is a method of manufacturing a plate.

[0006]

[Action]

First, the reasons for limiting the components in the rolled aluminum alloy plate of the present invention will be described. The following alloy components are added for the purpose of enhancing the strength of aluminum and controlling the ear ratio and formability. Mg: Mg is expected to age harden by precipitation of Mg ₂ Si or Al-Cu-Mg due to coexistence with Si / Cu, and when performing intermediate annealing that brings about a solution treatment effect as in the present invention,
In particular, it is effective in suppressing the decrease in strength after baking. Furthermore, Mg alone is an element that has the effect of solid solution strengthening. As described above, it is an essential element for improving the strength, but when the Mg content is less than 0.5%, its effect is small, and when it is added in excess of 2%, there is no problem in draw forming, but work hardening is easy. Therefore, redrawability and ironing property are deteriorated. Therefore, the amount of Mg should be in the range of 0.5 to 2%. Mn: Mn is an element that contributes to the improvement of strength and is effective in improving the formability. In particular, Mn is particularly important in the can body material, which is the intended use of the present invention, because ironing is performed. Emulsion type lubricants are usually used in the ironing of aluminum alloy sheets. Mn
When the amount of crystallized substances is small, even if they have the same level of strength, the emulsion type lubricant alone lacks the lubrication ability, resulting in poor appearance such as scratches and seizure called galling. This goring phenomenon is due to the size of the crystallized substance,
It is known to be influenced by the amount and type, and Mn is an essential element for properly forming the crystallized substance. Mn
If the amount is less than 0.5%, the solid lubricating effect of the Mn compound cannot be obtained, and if it exceeds 1.8%, MnAl.
The primary crystal giant intermetallic compound of ₆ crystallizes and the formability is significantly impaired. Therefore, the Mn content is 0.5 to 1.8%. Fe: Fe is an element necessary for promoting crystallization and precipitation of Mn and controlling the amount of Mn solid solution in the aluminum matrix and the dispersed state of the Mn-based insoluble compound. The necessary condition for obtaining the proper state of the compound or the like is the addition of Fe according to the amount of Mn added. When the Fe content is less than 0.1%, it is difficult to obtain a proper compound dispersion state, and when the Fe content exceeds 0.7%, a primary crystal giant compound is likely to be formed together with the added Mn, and the formability is significantly impaired. . Therefore, the Fe content is 0.1
~ 0.7%. Further, if the (Fe + Mn) amount exceeds 2%, a primary crystal giant compound is likely to be formed and formability is significantly impaired. Therefore, the (Fe + Mn) amount is preferably 2% or less. Ti, B: In an ordinary aluminum alloy, a small amount of Ti and B is added for refining and stabilizing the ingot crystal grains. In the present invention, Ti: 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 crystallizes and hinders formability. Therefore Ti
The amount is in the range of 0.005 to 0.2%. 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%, there is no effect, and if it exceeds 0.05%, coarse particles of TiB ₂ are mixed to impair the formability, so the B content added with Ti is 0.0001 to 0. The range is 0.05%. Cu: In the present invention, strength improvement due to the solution treatment effect of Cu can be expected. That is, by adding Cu, the strength can be improved by utilizing the age hardening that occurs in the precipitation process of Al-Cu-Mg-based precipitates during the baking treatment. If the Cu content is less than 0.05%, the effect cannot be obtained, while 0.5%
If it is added in excess of 1, the age-hardening is easily obtained, but it becomes too hard and hinders the moldability. Therefore, Cu
The amount is 0.05 to 0.5%. By adding Si: Si, strength improvement 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, and if it exceeds 0.5%, age hardening can be easily obtained, but the material becomes too hard and hinders the moldability. 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 , and if the Zn content is less than 0.1%, there is no effect, and if it exceeds 0.5%, the corrosion resistance deteriorates. It is necessary to regulate below this value. Therefore,
The Zn amount is 0.1 to 0.5%. Cr: Cr is an element effective in improving strength, but 0.0
If it is less than 5%, the effect is small, and if it exceeds 0.3%, the formation of huge crystallized substances may occur, resulting in deterioration of moldability, which is not preferable. Therefore, the Cr content is 0.05 to 0.3%. The balance of each of the above components is Al and inevitable impurities.

Next, the manufacturing process in the present invention will be described. Casting: An aluminum alloy ingot having the above 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 which also serves as homogenization treatment, or after heating as homogenization treatment and then preheating before hot rolling. This homogenization treatment is an effective treatment for improving the strength, toughness and deep drawing workability of the final plate and reducing the variation in the ear ratio.
Below 560 ° C, sufficient homogenization cannot be obtained, and 620
If the temperature exceeds ℃, swelling may occur on the surface of the ingot, so the soaking temperature is 560 to 620 ℃. Further, since holding for less than 1 hour does not result in sufficient homogenization, it is desirable to set the holding time to 1 hour or more. The upper limit of the holding time may be set appropriately in consideration of productivity. Hot rolling: The conditions for hot rolling are not particularly limited,
In consideration of hot ductility, a rising temperature of 230 ° C or higher is preferable. The thickness of the ascending plate is preferably 10 mm or less in consideration of the winding property. Cold rolling: In the case of a structure recrystallized after hot rolling, it is necessary to perform cold rolling with a rolling rate of 30% or more in order to obtain a uniform recrystallized structure in the subsequent annealing. 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 promotes crystallization of the R direction of the normally high ear component. A like the alloy of the present invention
In the 1-Mn-Mg-based alloy, a large number of crystallized compounds having a size of several μm are usually present, and cold rolling causes strains to accumulate near the crystallized substances, which facilitates recrystallization. Therefore, by performing annealing such that the heating / cooling rate is 0.5 ° C./s or more, the ultimate temperature is 290 to 400 ° C., and the time to be maintained in this temperature range is within 10 minutes, the crystallized substances are preferentially added from the vicinity of the crystallized substances. Recrystallization with R orientation starts. The recrystallization rate is preferably 10 to 80%. Heating / cooling rate is 0.5
If less than ℃ / s, Mg ₂ Si, Al ₂ CuM
Precipitation of g and αAlMnSi or Al ₆ Mn occurs, and the growth of crystals having a Cube orientation is suppressed during the second annealing, which is not preferable. If the annealing temperature is less than 290 ° C, recrystallization does not proceed sufficiently, and if the annealing temperature exceeds 400 ° C, recrystallization hardly occurs, which is not preferable. Therefore, the annealing temperature is 290 to 400 ° C., preferably 3
20-380 degreeC. Cold rolling: After the above partial recrystallization annealing, cold rolling with a rolling ratio of 5 to 30% is performed, and a slight strain is applied to the portion recrystallized by the first annealing. If the rolling ratio is less than 5%, the strain applied is not sufficient, and if it exceeds 30%, the strain of strength is added to the recrystallized portion. Therefore, preferential generation and growth of 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 substances is reduced by the first-stage annealing, the vicinity of the crystallized substances is easily recrystallized in the second-stage annealing. It cannot be a nucleus, and instead, recrystallization preferentially proceeds from the dislocation accumulating 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 Cube orientation and has a low ear component. That is, the second-stage annealing preferentially generates recrystallized grains in the Cube orientation, and even grows to the vicinity of the crystallized substances that cannot be completely recrystallized, resulting in a recrystallized structure with many Cube orientations as a whole. , As a whole, the tissue has a low ear rate. Japanese Examined Japanese Patent Sho 60-3
Japanese Patent No. 7186 describes that this second stage annealing is performed in a batch type, but in the present invention, this annealing is performed at a high heating rate of 1 ° C./s or more like a CAL (continuous annealing furnace). By having a cooling rate and an ultimate temperature of 400 to 600 ° C., it is desired to improve strength by the solution treatment effect by solid solution of metal elements such as Cu, Mg, and Si. That is, although the strength during DI molding is not so strong, it is possible to obtain an aluminum alloy plate which is not significantly reduced in strength due to age hardening even if a coating baking treatment is performed. Therefore, the strength during DI molding is not so high that the moldability is good, and the strength after DI baking is small, so the strength during DI molding is lower than that of the batch type annealed material, but the strength during DI molding is low. In the end, an aluminum alloy plate having sufficient strength is obtained. If the ultimate temperature is less than 400 ° C, a sufficient recrystallized structure cannot be obtained,
Further, although it is expected that the higher the temperature is, the strength improvement due to the solution treatment can be expected, the higher the temperature exceeds 600 ° C, the more inconvenient the production such as the softening due to the eutectic melting, and the partial melting may impair the appearance of the product. . Therefore, the ultimate temperature is set to 400 to 600 ° C. If the cooling rate is slower than 1 ° C./s, the solid-dissolved alloy elements are precipitated during the cooling process, and the degree of strength improvement due to the solution treatment effect is reduced. Therefore, the cooling rate is 1 ° C./s or more. Further, at a temperature higher than 400 ° C., the surface oxidation remarkably progresses, so it is necessary to reduce the holding time at 400 ° C. or higher. When the time is longer than 10 minutes, the oxide film formed on the surface impairs the cold rollability and the product appearance after annealing. Therefore, the total period of heating, holding and cooling is to be exposed to the temperature range of 400 to 600 ° C. for 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 reason as well, it is preferable that the heating rate is fast, 1 ° C / s.
The heating rate is the above. Cold rolling: After the above annealing, cold rolling is performed, but the rolling ratio is 4
If it is 0% or more, the required strength cannot be obtained. It is expected that the deep drawability will be improved by performing final annealing at about 100 to 200 ° C., if necessary.

[0009]

EXAMPLE An aluminum alloy having the chemical composition shown in Table 1 was rolled and heat-treated by the manufacturing method shown in Table 2 to prepare a sample. In Table 2, the column of soaking shows temperature × holding time, the columns of hot rolling and cold rolling show sheet thickness (mm), and the column of intermediate annealing shows temperature × holding time. However, the holding time of 0 indicates that the 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. Each will be described below. 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 second step is batch annealing and the second step is batch annealing. No. 4 is a comparative example in which the first step was batch annealing and the second step was CAL annealing. No. 5 is a comparative example in which the first step was performed by CAL annealing at a temperature lower than the range of the present invention and the second step was also performed by 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 has a higher temperature than the range of the present invention.
This is a comparative example in which L annealing is performed and the second step is also CAL annealing. No. 8 is a comparative example in which the rolling ratio of the cold rolling between the first and second CAL annealing is higher than the range of the present invention. N
o9 is a comparative example in which the second step annealing is performed by high temperature batch annealing, but the time of exposure to the temperature range of 400 to 600 ° C. is set to exceed 10 minutes, although the same step as in the present invention.

[0010]

[Table 1]

[0011]

[Table 2]

With respect to the obtained sample, the tensile strength (TS: N / mm ² ) and proof stress (YS: N / mm ² ) of the base plate and the plate after heat treatment at 200 ° C. for 20 minutes corresponding to coating baking,
The elongation (EL:%) was examined, and a 66 mmφ circle was deep-drawn with a clearance of 30% using a punch having a diameter of 38 mmφ and a shoulder R of 2.5 mm to measure the ear rate. Further, actual DI molding was performed to observe the continuous moldability and the appearance of the DI can. The appearance was judged by the presence or absence of flow line-like appearance defects along the rolling direction of the can side wall. The results are shown in Table 3.
Shown in.

[0013]

[Table 3]

Each of these will be described below. In the conventional example in which the No. 1 annealing was performed only once by CAL, the original plate and the strength after baking were sufficient, but the ear rate was as high as 5%. In the conventional example in which batch rolling annealing was performed after hot rolling without performing cold rolling of No2, the ear ratio was as low as 3%,
The original plate has high strength and 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 base plate during DI molding is 300 N / mm ² in tensile strength and ² in proof stress.
It is 82 N / mm ^2, which is about the same as the conventional material No. 1 and easy to mold. Moreover, the tensile strength is improved by 5 N / mm ² after baking, which shows 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 DI property, and no defect is observed in the appearance of the DI molded can. As described above, the invention examples have soft base plate strength and therefore good moldability, sufficiently satisfy the required strength after baking, have extremely low ear rates, and are excellent in DI property and poor appearance. 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 base plate was too high and the formability was poor, and the tensile strength was significantly reduced by the baking treatment. 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 original plate and the strength after baking, DI property, and the appearance of the DI can were almost the same as those of the invention example, but the ear ratio was slightly larger. Indicates the value. N
In the comparative example in which the first step of o5 was performed at a temperature lower than the range of the present invention by CAL annealing and the second step was also performed by CAL annealing, the ear ratio was inferior to that of the inventive example similarly to No4. The first step of No. 7 was CAL annealed at a temperature higher than the range of the present invention, and the second step was 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 rate is inferior to that of the invention example. In Comparative Example in which the rolling ratio of the cold rolling between the first and second CAL annealings of No. 8 is higher than the range of the present invention, the ear ratio is inferior to that of the inventive example as in No. 5 and No. 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 so that the time of exposure to the temperature range of 400 to 600 ° C. exceeds 10 minutes, the ear rate is the same as that of the conventional example. Equivalent, but the base plate strength is too high,
On the contrary, there is a problem in strength due to a large decrease in strength after baking, and a flow line-like appearance defect occurs in DI molding.

[0015]

[Effect] The aluminum hard plate for forming processing produced by the present invention is particularly suitable for applications such as can materials that are subjected to paint baking treatment, and has low deep-drawing ears, high strength, and formability. Is also excellent. That is, as described in detail, according to the present invention, the strength at the time of DI molding is not so high, the moldability is good, and the strength is improved by the paint baking treatment. It is possible to provide an aluminum alloy plate that exhibits characteristics and has an extremely low ear rate. Therefore, according to the manufacturing method of the present invention, it is possible to obtain an aluminum alloy plate suitable for can bodies such as DI cans, DR cans, and DRD cans.

Claims (1)

[Claims] 1. In weight% (hereinafter the same), Mg: 0.5
~ 2.0%, Mn: 0.5 to 1.8%, Fe: 0.1
0.7%, Ti: 0.005 for microstructuring and stabilization
.About.0.20% alone or B: 0.0001 to 0.
0.05%, and further Si: 0.05-0.
5%, Cu: 0.05 to 0.5%, Cr: 0.05 to
An aluminum alloy ingot containing 0.3%, Zn: 0.1 to 0.5% of one kind or two kinds, and the balance of Al and impurities is soaked at 560 to 620 ° C. according to a conventional method, and then heated. Hot rolling, then cold rolling, then heating / cooling rate of 0.5 ° C / s or more, 290-40
The reached temperature of 0 ° C, the time to be kept in this temperature range is 10
Annealing is performed for no more than minutes, then cold rolling is performed at a rolling rate of 5 to 30%, then at a heating / cooling rate of 1 ° C./s or more, at an ultimate temperature of 400 to 600 ° C., and at 400 to 600
An aluminum alloy having a low earring ratio and excellent formability, which is characterized by performing recrystallization annealing for 10 minutes of exposure to a temperature range of ℃, and then performing cold rolling with a rolling rate of 40% or more. Method of manufacturing a plate.