JP2000219929A - Aluminum alloy sheet excellent in formability and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an aluminum alloy sheet in which crystal grain size can be made into the smaller one and excellent in formability by setting optimum cooling conditions after soaking treatment and to provide a method for producing the alloy sheet. SOLUTION: This aluminum alloy sheet excellent in formability is formed into a sheet body contg., as chemical components, by weight, 0.85 to 1.50% Mn, 0.50 to 1.50% Mg, 0.30 to 0.70% Fe, 0.10 to 0.50% Si, 0.15 to 0.50% Cu, and the balance Al with inevitable impurities. As to the method for producing the aluminum alloy sheet excellent in formability, an aluminum alloy ingot composed of the above chemical components is subjected to homogenizing treatment at 590 to 630 deg.C by an ordinary method, is thereafter cooled to <=550 deg.C at a cooling rate of <=50 deg.C/h, is subjected to hot rolling at 400 to 550 deg.C starting temp. and 300 to 350 deg.C finishing temp. and is subsequently subjected to cold rolling.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy plate excellent in formability (neck / flange forming) and preferably used for a two-piece aluminum can body such as a beverage can.

[0002]

2. Description of the Related Art Aluminum can bodies have Al-M bodies.
An n-Mg-based JIS3004 alloy hard plate is conventionally used. JIS3004 alloy is widely used as a can body material because it has good formability even when cold rolling is performed at a high rolling ratio in order to increase strength. As disclosed in Japanese Patent Application Laid-Open No. 3-90549, which is a typical prior art, this kind of alloy is subjected to a homogenization treatment by heating after casting to reduce segregation and reduce the Al—Fe—Mn—Si phase ( Hereafter, the growth of the precipitated phase (α phase) is promoted.

[0003] Control of the precipitated phase is important because the size and distribution of the precipitated phase affect the recrystallization behavior after hot rolling. In the soaking heat treatment, the higher the soaking temperature and the longer the soaking time, the more the growth of precipitates is observed. Therefore, the soaking condition is determined in consideration of productivity.

[0004]

In the processing of a can body, the processing conditions have recently become stricter due to an increase in molding speed and a reduction in lubrication cost, and there has been a demand for improved workability. In this case, the size of the crystal grains is a factor that affects the drawing workability and the ironing (handle) workability,
If the crystal grain size is large, the workability is reduced.
It is desirable to reduce crystal grains in recrystallization after the completion of hot rolling.

[0005] Crystals, precipitates,
There is a strain (dislocation), and it is possible to control the crystal grain size to be small by optimizing the distribution and promoting recrystallization. In growing the precipitates, conventionally, the soaking temperature and soaking time were controlled.However, as described above, there is a limitation in terms of productivity. It's never easy.

The present invention has been devised in view of such a conventional situation in order to further reduce the crystal grain size. Focusing on the effects of the cooling temperature range and cooling rate on the conditions of recrystallization, we found that the grain size can be reduced by setting the cooling conditions after soaking. It has been reached. Thus, an object of the present invention is to make it possible to further reduce the crystal grain size by setting appropriate cooling conditions on the basis of the above-mentioned technical background, and thus to form an aluminum alloy sheet having excellent formability. And a method of manufacturing the alloy plate.

[0007]

The present invention has the following configuration to achieve the above object. That is, in the invention of claim 1 of the present invention, Mn: 0.85 to 1.50%, Mg: 0.5% by weight as a chemical component.
0 to 1.50%, Fe: 0.30 to 0.70%, Si:
An aluminum alloy containing 0.10 to 0.50% and Cu: 0.15 to 0.50%, with the balance being formed into a plate composed of Al and inevitable impurities. It is a board.

According to a second aspect of the present invention, there is provided an aluminum alloy sheet having excellent formability according to the first aspect, wherein the aluminum alloy sheet is formed into a plate by homogenization, hot rolling and cold rolling. Surface grain size after hot rolling is 17
２０20 μm.

Further, the invention of claim 3 according to the present invention is characterized in that Mn: 0.85 to 1.50% by weight as a chemical component;
Mg: 0.50 to 1.50%, Fe: 0.30 to 0.7
0%, Si: 0.10 to 0.50%, Cu: 0.15
An aluminum alloy ingot containing 0.50%, the balance being Al and unavoidable impurities, is homogenized at 590-630 ° C by a usual method, and then cooled at a cooling rate of 50 ° C / h.
Then, the temperature is lowered to 550 ° C. or less, and hot rolling is started at a temperature of 4 ° C.
This is a method for producing an aluminum alloy sheet excellent in formability, characterized in that cold rolling is performed after performing at a temperature of 00 to 550 ° C and an end temperature of 300 to 350 ° C.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be specifically described below. First, the reasons for limiting each component in the aluminum alloy sheet according to the present invention will be described. In this case, each alloy component is added for the purpose of increasing the strength of the aluminum and at the same time controlling the ear ratio (the degree of directionality of the ear generated by the in-plane anisotropy of the material at the time of axisymmetric drawing) and the formability. Things.

◆ Mn: Mn contributes to improvement in strength and is effective in improving ironing workability by proper distribution of the compound Al—Fe—Mn—Si phase (α phase). M
When n is less than 0.85%, both effects are small, and
If it exceeds 1.50%, a primary crystal giant metal compound of MnAl ₆ is crystallized, leading to a reduction in formability. Therefore, Mn is 0.1.
85% to 1.50%.

(1) Mg: Mg alone is effective for improving strength by solid solution strengthening, and is combined with Cu (when using CAL: annealing for a short time by rapid heating and cooling while unwinding a product coil) to form Al. -Cu-Mg is precipitated, and is effective in preventing softening due to baking (baking printing) during can making. If Mg is less than 0.50%, there is no effect, and if Mg exceeds 1.50%, work hardening is increased, leading to a reduction in moldability. Therefore, Mg is 0.50%
To 1.50%.

◆ Fe: Fe is effective in reducing the crystal grain size and improving the formability by proper distribution of the compound (α phase).
If Fe is less than 0.30%, the effect is not obtained.
If it exceeds 70%, the moldability is reduced due to the coarsening of the compound (α phase). Therefore, Fe is 0.30% or more.
0.70%.

◆ Si: Si is effective in improving the formability by forming a compound (α phase). If the Si content is less than 0.10%, the effect is not obtained, and if the Si content exceeds 0.50%, M
The increase in strength due to g ₂ Si increases, leading to a decrease in formability. Therefore, Si is set to 0.10% to 0.50%.

(4) Cu: Cu has an effect of increasing the strength and preventing softening due to baking at the time of can making when combined with Mg (when CAL is used). If Cu is less than 0.15%, there is no effect, and if Cu exceeds 0.50%, the strength increases greatly, leading to a decrease in formability. Therefore, Cu is 0.15% or more.
0.50%.

As other unavoidable impurities, T
If i is an impurity level such as 0.10% or less and B is 0.05% or less, the effects of the present invention are not hindered.

Next, the manufacturing process in the present invention will be described. ◆ Casting: An aluminum alloy ingot having the above-mentioned alloy composition is manufactured by a DC casting method (semi-continuous casting method) according to a conventional method.

(1) Soaking: First, the ingot is subjected to a homogenizing treatment. The homogenization treatment includes homogenization of micro-segregation, precipitation of a supersaturated element, and Al-Fe-Mn to Al-Fe-Mn.
-It is effective in promoting the phase transformation to the Si phase (α phase) and improving ironing workability. In this case, if the temperature is lower than 590 ° C., the growth of the precipitate is not sufficient, so that it does not easily become a nucleus for recrystallization. If the temperature exceeds 630 ° C., burning may occur in the furnace. Therefore, the homogenization treatment is performed within a temperature range of 590 to 630 ° C. In addition, since a sufficient homogenization cannot be obtained by holding the heat soak for less than 2 hours, the soaking time is desirably 2 hours or more.

(4) Cooling: In the cooling performed after the soaking, the elements dissolved by the soaking are precipitated as the temperature decreases, and the precipitates generated during the soaking further grow. If the cooling rate in this case is higher than 50 ° C./h, the time required for precipitation cannot be obtained, and the growth of precipitates is not sufficient. On the other hand, if the cooling temperature is higher than 550 ° C., the difference from the soaking end temperature is small, and the change in the solid solubility limit is small, so that a driving force for precipitation cannot be obtained and the effect on the growth of precipitates is not obtained. Is small.
Therefore, the cooling rate is 50 ° C./h or less and 550 ° C.
Cool to below. Regarding the temperature at which cooling is achieved, the growth of precipitates is preferably observed by cooling to 480 ° C.

(4) Hot rolling: After the above-mentioned cooling treatment is completed, hot rolling is performed. Reducing the hot rolling start temperature to a low temperature has the effect of positively introducing strain that is a driving force for recrystallization during hot rolling and making crystal grains fine. In addition, seizure on the plate surface can be reduced. If the temperature exceeds 550 ° C., the effect is small. If the temperature is lower than 400 ° C., the effect is increased, but the number of rough rolling passes increases, and the productivity is poor. Therefore, the hot rolling start temperature is set to 400 to 550 ° C.

The end temperature of the hot rolling needs to be 300 to 350 ° C. If the temperature is lower than 300 ° C., the entire hot rolled sheet cannot be recrystallized. If the temperature exceeds 350 ° C., recrystallization occurs, but the crystal grains become coarse.

(5) Cold rolling: After the completion of hot rolling, cold rolling is performed by a usual method to obtain an aluminum alloy plate having a required thickness.

[0023]

Examples of the present invention will be described below with reference to Tables 1 and 2 below.

An aluminum alloy having a chemical composition as shown in Table 1 was cast and homogenized, cooled and hot rolled by the production method under each production condition shown in Table 2. A and B in Table 1 are alloys according to the present invention, and C is an alloy in which Mg is lower than the range of the present invention. Table 2 shows the precipitate size of the aluminum plate subjected to the homogenization treatment, cooling, and hot rolling and the surface crystal grain size after the completion of the hot rolling by each manufacturing method.

[0025]

[Table 1]

[0026]

[Table 2]

No. Examples 1, 2, and 3 are examples of the present invention, in which fine recrystallized grains having a surface crystal grain size of the hot coil of 20 μm or less were obtained, and showed good formability as a body material. No. 4 is a comparative example using alloy C, and M
Since g is small, the introduction of distortion during hot rolling is small. For this reason, the occurrence of recrystallization is reduced, and the crystal grains are coarsened. No. Sample No. 5 has a soaking temperature of 520 ° C., which is lower than the range of the present invention, and the growth of precipitates during soaking is not sufficient, and the amount of solid solution is small, so that the precipitates hardly grow during cooling.

No. In No. 6, the soaking temperature was 640 [deg.] C., which was higher than the range of the present invention, and burning occurred during the soaking, making it unusable. No. In No. 7, the cooling rate after the end of the soaking was 100 ° C./h, which was outside the range of the present invention, and the time and temperature range necessary for growing the precipitate were insufficient, and the crystal grains did not become fine.

No. In No. 8, the ultimate temperature during cooling is higher than the range of the present invention, the difference from the soaking temperature is small, and the driving force for precipitation is not sufficient. As a result, the precipitate became fine, and the crystal grains could not be refined. No. In No. 9, since the hot rolling start temperature is high, the introduction of distortion during hot rolling is insufficient,
Recrystallization was not sufficiently generated.

No. In No. 10, since the hot rolling start temperature was low, the hot rolling end temperature was also lower than the range of the present invention, did not reach the recrystallization temperature, and the rolling texture remained. No. 11
In this case, since the hot rolling end temperature was high, recrystallization was coarsened, and fine crystal grains could not be obtained.

[0031]

As described above, according to the present invention, the occurrence of recrystallization can be promoted by optimizing the soaking conditions and hot rolling conditions and controlling the precipitates and strains. In addition, it is possible to provide an aluminum alloy plate having small crystal grains, high strength and good formability, and greatly contributes to improvement of productivity in a manufacturing process.

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Claims (3)

[Claims] 1. Mn: 0.8% by weight as a chemical component
5 to 1.50%, Mg: 0.50 to 1.50%, Fe:
0.30 to 0.70%, Si: 0.10 to 0.50%,
Cu: An aluminum alloy plate excellent in formability, containing 0.15 to 0.50%, with the balance being formed into a plate composed of Al and unavoidable impurities. 2. The aluminum having excellent formability according to claim 1, wherein the aluminum is formed into a plate by homogenization treatment, hot rolling and cold rolling, and has a surface crystal grain size of 17 to 20 μm after completion of hot rolling. Alloy plate. 3. Mn: 0.8% by weight as a chemical component.
5 to 1.50%, Mg: 0.50 to 1.50%, Fe:
0.30 to 0.70%, Si: 0.10 to 0.50%,
Cu: An aluminum alloy ingot containing 0.15 to 0.50%, with the balance being Al and unavoidable impurities,
After homogenizing at 90 to 630 ° C. by a usual method, it is cooled to 550 ° C. or less at a cooling rate of 50 ° C./h or less, and hot rolling is started at a temperature of 400 to 550 ° C. and finished at a temperature of 300 to 3 °.
A method for producing an aluminum alloy sheet having excellent formability, comprising performing cold rolling at 50 ° C.