JPH0978168A - Aluminum alloy sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an Al alloy sheet in which crystal grains in the surface are refined, in an Al alloy sheet produced by continuous casting, by incorporating specified amounts of Fe, Ti and Cr, specifying the content of Fe solid solution and making crystallizations into large ones. SOLUTION: This Al alloy sheet is the one having a compsn. contg., by weight, 0.3 to 2.0% Fe, 0.001 to 0.2% Ti and 0.001 to 0.1% Cr, furthermore contg., at need, one or more kinds of <=0.5% Mg and <=0.4% Cu and moreover contg. <=0.5% Mn and <=0.1% B, and the balance Al, in which the content of Fe solid solution is regulated to <=0.3% and crystallizations having >=4μm diameter are present by >=20/mm<2> . By the addition of Fe, its strength increases, and by the addition of Cr, Al-Fe crystallizations are made large, and furthermore, large Al-Cr intermetallic compounds are formed. Thus, at the time of executing heat treatment in the post stage, the effect of pinning dislocations is given to refine the crystal grains. Ti has the effect of refining the crystal grains and making them into equi-axed ones and furthermore has the effect of reducing the content of Fe to enter into solid solution in the matrix.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy sheet used for fins, building materials, foils, etc., and produced by continuous thin sheet casting instead of DC casting.

[0002]

2. Description of the Related Art Conventionally, aluminum or aluminum alloy (hereinafter collectively referred to as aluminum) plates have been mainly used for thin metal plates having a thickness of 0.1 mm or less. This is because aluminum is excellent in workability, so that an aluminum plate can be manufactured at a relatively low cost and also has excellent corrosion resistance, light resistance and moisture resistance.

Usually, an aluminum plate is manufactured as follows. First, aluminum ingot is melted and adjusted to a predetermined composition. Next, casting is performed to a thickness of 250 to 80
A so-called aluminum ingot having a rectangular parallelepiped shape of 0 mm is produced. After that, in order to make the structure of the ingot uniform and remove the casting distortion, the ingot is subjected to soaking treatment and further hot-rolled to obtain an aluminum plate having a thickness of 20 mm or less, for example. Next, this aluminum plate is cold-rolled and optionally heat-treated to obtain a final product thickness of 0.1 mm or the like. Further, if necessary, annealing is performed, and the aluminum plate becomes the final product.

However, with the widespread use of aluminum plates and their applications, the aluminum plates are often subjected to surface treatment in order to improve their appearance and corrosion resistance. Further, further cost reduction is required. In order to improve the surface treatment property, it is essential to secure uniform etching property. This etching property is greatly affected by the intermetallic compound in the aluminum material.
Usually, an aluminum plate has a so-called matrix in which an additive element is solid-dissolved in aluminum and the diameter in the matrix is 1
To a fine intermetallic compound of about 20 μm. Since the intermetallic compound and the matrix have different potentials,
When performing etching, for example, when the intermetallic compound is base, the intermetallic compound is preferentially dissolved over the matrix, and conversely, when the matrix is base, the matrix around the intermetallic compound is Will preferentially dissolve. Therefore, in order to further improve the uniformity of etching, it is necessary to reduce intermetallic compounds caused by segregation of components in the matrix and to make the intermetallic compounds finer and uniformly distributed.

As the above-mentioned intermetallic compound, Al--Fe
System, Al-Fe-Mn system, Al-Mn system, Al-Si system and Mg-Si system. Among these, the so-called pure aluminum-based alloys include Al-Fe-based and Al-Fe-M.
An n-based intermetallic compound is mainly formed. For example, in an Al-1 wt% Fe alloy, about 4% of the total volume thereof is Al.
-It becomes a Fe-based intermetallic compound. In addition, due to the difference in the steps in which these intermetallic compounds are formed,
It can be mainly classified into two types. One is a crystallized product generated during casting, and this crystallized product is mainly generated in a crystal grain boundary during casting. The other is a precipitate generated by the precipitation of a supersaturated component during the heat treatment of the subsequent step. Among these, in order to make the crystallized substances uniform, it is important to make the crystal grains during casting uniform and fine. Further, in order to uniformly distribute the precipitates, it is important to reduce the component segregation and so-called micro segregation formed during casting.

According to the thin plate continuous casting method using a casting roll, since fine intermetallic compounds are uniformly distributed, it is possible to manufacture a plate material having the above-mentioned properties. That is, in the thin plate continuous casting method, pressure is constantly applied between the molten metal and the mold, and an air gap or the like does not occur, so that the thermal conductivity is extremely high. Therefore, the cooling rate is about 300 ° C./second, and an extremely high cooling rate can be obtained as compared with the normal DC casting method of 1 ° C./second. Therefore, the microstructure tends to be fine and uniform, so that the crystallized substances formed between the crystal grains are fine and uniform. For the same reason, segregation of components in the matrix is unlikely to occur, and etching is likely to be uniform. Furthermore, the addition amounts of Cu, Zn, etc., which do not form an intermetallic compound, can also be increased significantly compared to usual. Usually, when these elements are added in a very large amount, they are crystallized at crystal grain boundaries and adversely affect strength and etching property (a step is formed along the crystal grains). However, in the thin plate continuous casting method, since these elements are forced to form a solid solution in the matrix and do not crystallize at the grain boundaries, there is no possibility of the above-mentioned adverse effects occurring. Therefore, the strength, etching property, etching rate and the like can be greatly improved by greatly increasing the addition amounts of these elements.

Further, in the thin plate continuous casting method, since the plate obtained by casting is thin, there is no need for processing such as hot rolling and equipment for thinning the plate, and the cost can be greatly reduced. In the manufacturing process by the thin plate continuous casting method, first, melting and casting are performed to manufacture an aluminum plate having a thickness of 20 mm or less. Then, if necessary, the aluminum plate is heat-treated. This heat treatment step is called rough annealing and is usually performed at a temperature of 400 to 600 ° C. However, this heat treatment step can be omitted. After this heat treatment, it is necessary to perform hot rolling to reduce the plate thickness in the usual DC casting method, but this can be omitted in the case of the thin plate continuous casting method. Further, this aluminum plate is cold-rolled to a predetermined plate thickness such as 0.1 mm. Note that heat treatment may be performed during the cold rolling. This heat treatment is called intermediate annealing, which improves rolling property by removing rolling strain,
And for the purpose of recrystallization for grain refinement, usually 30
It is carried out at a temperature of 0 ° C or higher. If necessary, final annealing is performed to adjust the heat treatment to obtain a product. The thin plate continuous casting material thus obtained is applied to products such as disks used in computers and the like in which the intermetallic compound needs to be fine, and is highly evaluated.

[0008]

However, the above-mentioned prior art has the following problems. That is, when the thin plate continuous casting method is applied to a JIS 1000 series aluminum alloy or an Al-Fe series alloy, the surface crystal grains become coarse and a pattern is formed along the crystal grains after rolling, impairing the appearance of the obtained aluminum alloy plate. There is a drawback that. Further, the hardness and strength are greatly changed, holes and the like are likely to occur at the time of rolling, and in an extreme case, there is a problem that the coil is broken and the aluminum alloy sheet cannot be rolled.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an aluminum alloy plate having fine surface crystal grains.

[0010]

The aluminum alloy sheet according to the present invention is an aluminum alloy sheet produced by continuous casting, Fe: 0.3 to 2.0% by weight, T
i: 0.001 to 0.2% by weight and Cr: 0.001
To 0.1% by weight, the balance consisting of Al and inevitable impurities, and the solid solution amount of Fe is 0.3% by weight or less,
It is characterized in that the number of crystallized substances having a diameter of 4 μm or more is 20 / mm ² or more.

The aluminum alloy plate further comprises Mg:
It may contain one or more elements selected from the group consisting of 0.5 wt% or less and Cu: 0.4 wt% or less.

The aluminum alloy plate is further M
It may contain n: 0.5% by weight or less.

Further, the aluminum alloy plate may further contain B: 0.1% by weight or less.

It is preferable that the aluminum alloy plate has a plate thickness of 3 to 20 mm immediately after completion of the continuous casting.

Further, the aluminum alloy plate is one obtained by performing one or more annealing treatments after the continuous casting, and the temperature rising rate of the annealing treatment performed first in the annealing treatment is 1000 ° C. / Hour or more is preferable.

In this case, the annealing treatment at a heating rate of 1000 ° C./hour or more may be carried out after the cold rolling after the continuous casting, or the temperature rising of 1000 ° C./hour or more. Cold rolling may be performed after the speed annealing treatment.

[0017]

[Function] As a result of earnest research by the inventors of the present application, Al-Fe
It has been found that when the thin plate continuous casting method is applied to the base alloy, the surface crystal grains of the aluminum alloy plate become extremely coarse, about 0.3 to 2 mm, during heat treatments such as rough annealing, intermediate annealing and final annealing. As a result of further investigation on the cause of coarsening of the crystal grains during these heat treatments, it was found that there are two causes.

One is that the size of the crystallized intermetallic compound is too fine. When an aluminum alloy plate is produced by a normal DC casting method, large intermetallic compounds are arranged along the crystal grains. Therefore, when recrystallization occurs due to the heat treatment in the subsequent step, the growth of crystal grains is suppressed by this large intermetallic compound. This phenomenon is commonly known as the dislocation pinning effect of intermetallic compounds. However, as described above, the intermetallic compound of the aluminum alloy plate produced by the thin plate continuous casting method has an extremely fine size and does not cause the pinning effect, so dislocations pass through the intermetallic compound during heat treatment. Therefore, the crystal grains become coarse.

The other is due to the solid solution of Fe. In the thin plate continuous casting method, since the cooling rate is extremely fast, Fe, which is hardly dissolved in the ordinary DC casting method, forms a solid solution. The solid solution Fe is precipitated by the heat treatment, but this Fe preferentially precipitates in the shear zone which becomes the recrystallization nucleus. This shear band is an aggregate of strains (dislocations) that are introduced when the material is processed by rolling or the like, and these dislocations are extremely present in the ingot and are usually called casting strains. And
Since Fe precipitates in the shear zone, the shear zone does not act as a recrystallization nucleus and the starting point of recrystallization decreases, so that the recrystallized grains become coarse.

As described above, increasing the size of the Al--Fe system crystallized product and preventing the precipitation of Fe are essential for refining the crystal grains of the Al--Fe system plate material. Therefore, as a result of earnest studies by the inventors of the present application, when Cr is added, the Al—Fe-based crystallized product is increased in size and a large Al—Cr-based intermetallic compound is generated, so that heat treatment is performed in a subsequent step. It was clarified that the pinning effect of dislocations was generated and the crystal grains became fine.

The heat treatment conditions are also very important in order to suppress precipitation of solid solution Fe during heat treatment and to control the size of recrystallized grains to be fine. In this case, since the precipitation of Fe is due to a diffusion phenomenon, its rate is extremely slow, and if it is heated to a temperature equal to or higher than the recrystallization temperature before sufficient precipitation occurs, fine crystal grains can be obtained. For this purpose, it is important to increase the temperature rising rate in the rough annealing, the intermediate annealing and the final annealing as much as possible, and at least the temperature rising rate of the first annealing is 1000 ° C./hour or more. preferable.

Next, the reason for limiting the numerical values in the present invention will be described. First, the reason for limiting the numerical value of the chemical composition of the aluminum alloy will be described.

Fe (iron): 0.3 to 2.0 wt% Fe is added to increase the strength of the aluminum alloy plate. Fe usually does not form a solid solution in Al and forms an intermetallic compound having a size of about 1 to 20 μm. Since these intermetallic compounds pin dislocations during rolling and heat treatment, the strength of the obtained aluminum alloy plate increases. However, when the cooling rate is fast as in the thin plate continuous casting method, the crystallized substances such as the Al—Fe intermetallic compound are too fine only by adding Fe alone, and the effect of pinning dislocations is small. Therefore, in order to increase the size of the Al-Fe based intermetallic compound, it is necessary to add Cr together with Fe, as described later.

When the cooling rate is extremely high as in the thin plate continuous casting method, a part of Fe is solid-dissolved, so that this solid-solved Fe precipitates in the subsequent step. The amount of solid solution during casting is Fe
Is determined by the balance between the diffusion rate and the solidification rate in the molten metal. When the Fe content exceeds 2% by weight, the solid solution amount of Fe becomes too large. For this reason, during heat treatment performed in a later step, Fe preferentially precipitates in the shear band that serves as a recrystallization nucleus and reduces the nucleation point of recrystallization, resulting in coarse crystal grains. Further, when the Fe content is less than 0.3% by weight, the amount of crystallized substances such as Al-Fe-based intermetallic compounds formed during casting decreases, so that the crystal grains become coarse when recrystallized in a later step. The pinning effect that suppresses is reduced. Therefore, the Fe content is 0.3 to 2.0% by weight.
And

Ti (titanium): 0.001 to 0.2
%, B (boron): 0.1% by weight or less Ti, like B, has the effect of making crystal grains fine and equiaxed during casting. Further, when the crystal grains are miniaturized, the crystal grain boundaries naturally increase, so that a large amount of intermetallic compounds such as Al—Fe crystallize out at the crystal grain boundaries. Therefore, addition of Ti also has the effect of reducing the solid solution amount of Fe in the matrix.
As described above, Ti is added in order to make the crystal grains finer and to distribute the crystallized substances uniformly and densely. Ti content is
If it is less than 0.001% by weight, the crystal grains of the cast plate become extremely coarse. For this reason, the distribution of intermetallic compounds formed between crystal grains becomes extremely sparse, which causes coarsening of crystal grains in the final product. On the other hand, when the amount of addition of Ti exceeds 0.2% by weight, Ti-B lumps are generated and surface defects are generated. Therefore, the Ti addition amount is set to 0.001 to 0.2% by weight.

Although Ti may be added as a simple substance of Ti, it is usually added in the form of a Ti-B alloy. It is extremely effective to add Ti and B at the same time for refining the crystal grains. This effect is due to the Ti-B based intermetallic compound T
It occurs when iB ₂ acts as a crystal nucleus during solidification. This intermetallic compound has a weight ratio of about Ti: B = 3: 1. However, when the content of B is too large, Ti-
The B intermetallic compound becomes coarse and surface defects occur in the final product, which is not preferable. Therefore, the B content is preferably 0.1% by weight or less.

Cr (chrome): 0.001 to 0.1
Cr is added in order to increase the amount of the crystallized material in the amount of% . When Cr forms a solid solution in the Al-Fe-based intermetallic compound, it has an effect of increasing the size of the intermetallic compound. In addition, large A
In some cases, an l-Cr intermetallic compound is formed. These large crystallized substances have a sufficient dislocation pinning effect,
Prevents coarsening of crystal grains during heat treatment. Furthermore,
The addition of Cr makes the Al-Fe intermetallic compound slightly crystallize, and has the effect of reducing the amount of Fe solid solution in the aluminum matrix. If the amount of Cr added is less than 0.001% by weight, these effects are not sufficient, and
If added in excess of wt%, Al-Cr-based crystallized substances,
It becomes extremely coarse, for example, its diameter becomes several mm,
Rollability and workability are significantly impaired. Therefore, the Cr addition amount is 0.001 to 0.1% by weight.

Cu (copper): 0.4 wt% or less Cu is added when the strength is insufficient only by adding Fe. If Cu is added in a very small amount, it will be solid-dissolved uniformly in the aluminum matrix. Therefore, the strength and hardness of the matrix are increased. However, if too much is added, a solid solution containing a large amount of Cu is crystallized at the grain boundaries, which exerts a very bad influence on the strength and etching properties of the aluminum alloy plate. In the thin plate continuous casting method, since precipitation to the crystal grain boundaries is small, it is possible to add a large amount as compared with the DC casting method. However, even in the thin plate continuous casting method, when Cu is added, the addition amount is 0.4
It should be less than or equal to weight%.

Mg (magnesium): 0.5 wt% or less Mg is uniformly dissolved in the aluminum matrix,
Like Cu, it increases the strength of the aluminum alloy plate.
Unlike Cu, Mg has a very high solid solubility in the matrix, and therefore precipitation at the crystal grain boundaries is unlikely to occur. However, if added in an excessively large amount, the matrix becomes difficult to be crushed, so that the workability and rollability are impaired and the effect of increasing the strength is saturated. Therefore, when adding Mg, the addition amount is 0.5% by weight or less.

Mn (manganese): 0.5 wt% or less Mn replaces a part of the Al—Fe-based intermetallic compound,
An Al-Fe-Mn-based intermetallic compound is formed. This Al
Since the size of the —Fe—Mn-based intermetallic compound is larger than that of the Al—Fe-based intermetallic compound, Mn is an element effective for increasing the size of the crystallized product. The large crystallized product has a dislocation pinning effect and prevents the crystal grains from becoming coarse during heat treatment. In addition, since the Al-Fe-Mn-based intermetallic compound has a small potential difference from the aluminum matrix, the corrosion resistance of the aluminum alloy plate is improved. Where M
Since n has a very small diffusion coefficient in molten aluminum, it is forcibly dissolved in the matrix during casting. Therefore, Mn tends to precipitate during heat treatment, the crystal grains in the final product are likely to become coarse, and the crystal grain sizes are different, which causes so-called mixed grains. Therefore, when Mn is added, the addition amount is 0.5% by weight.
The following is assumed.

In the present invention, unavoidable impurities include B, Zn, Zr, etc., each of which is 0.1
If it is at most% by weight, the effect of the present invention is not adversely affected. If the total amount of unavoidable impurities is 0.3% by weight or less, the effect of the present invention is not adversely affected. Further, among the above-mentioned unavoidable impurities, Si inevitably increases as the Fe content increases, but if the content is 0.5 wt% or less, the effect of the present invention is not adversely affected.

Next, the reason for limiting the numerical values for the solid solution amount of Fe and the crystallized substance will be described.

Solid solution amount of Fe: 0.3% by weight or less As described above, Fe is a component necessary for increasing the strength of the aluminum alloy plate. However, when the solid solution amount of Fe is too large, the size of the crystal grains in the final product becomes coarse. Fe that is solid-solved during casting preferentially precipitates in the shear zone during the heat treatment performed in the subsequent step. Since the shear band is a dislocation, that is, an aggregate of lattice defects, Fe is likely to precipitate on the lattice defects. Such precipitation of Fe reduces dislocations and relieves stress, so that the driving force required for recrystallization decreases. In addition, when the precipitation of Fe is large, the shear band disappears, and the starting point of recrystallization is reduced, so that the crystal grains become coarse. When the solid solution amount of Fe is 0.3% by weight or less, the amount of precipitation at the time of recrystallization is small, so that coarsening of crystal grains can be suppressed. Therefore, F
The solid solution amount of e is 0.3% by weight or less.

In order to reduce the solid solution amount of Fe, in addition to the reduction of the Fe amount itself, the cooling rate is lowered, the solid solution element such as Mg is added, and the apparent cooling rate of Ti and Cr is reduced. It is effective to add an element that causes it.

20 crystallized substances with a diameter of 4 μm or more / mm
² or more Like the solid solution amount of Fe, it is necessary to regulate the number of crystallized substances having a certain size (diameter) or more in order to reduce the crystal grain size. The crystallized substance having a diameter of 4 μm or more has an effect of suppressing the movement of dislocations during the heat treatment performed after casting and having the effect of making the size of the crystal grain fine by the pinning effect. On the other hand, when the diameter of the crystallized substance is 4 μm or less, the dislocations slip through the intermetallic compound and the pinning effect is insufficient. Therefore, in order to refine the crystal grains in the final product, the diameter of the crystallized substance needs to be 4 μm or more, and in order to sufficiently exert the pinning effect, the crystallized substance having a diameter of 4 μm or more is required. 20 pieces / mm ²
It must be above.

In order to increase the size of the crystallized substance, as described above, the addition of the element that forms the crystallized substance such as Fe and Mg, or the absorption by the Al--Fe intermetallic compound such as Mn is likely to occur. There are means for adding elements, adding elements such as Ti and Cr to reduce the apparent cooling rate, and lowering the cooling rate.

In the present invention, 20 or more crystallized substances with a diameter of 4 μm or more means ² crystallized substances with a diameter of 4 μm or more in 70% or more of the measured visual field.
If the number is 0 / mm ² or more, this requirement is satisfied. It is not always necessary that the number of crystallized substances of 4 μm or more is 20 or more / mm ² or more in all measurement visual fields.

Next, the continuous casting method in the present invention will be described. First, melt the aluminum ingot, then F
e, Cr and Ti are added, and if necessary, Cu,
Mg and Mn are added to obtain predetermined components. Then, casting is carried out by a thin plate continuous casting device using a casting roll. If necessary, rough annealing is performed on the obtained cast plate. The purpose of this rough annealing is to remove the casting distortion and to make the cast sheet ready for rolling. However,
When Cu, Mg and Mn are added as alloying elements within the range specified in the present invention, the cast plate is sufficiently soft and can be rolled and can be omitted.

Next, after cold rolling the cast plate, if necessary, an intermediate annealing is performed at a temperature of 300 ° C. or higher to improve the rolling property of the plate material, and then cold rolling is performed to a predetermined value. An aluminum alloy plate having a plate thickness of Further, in order to adjust the temper as necessary, the aluminum alloy plate is finally annealed to obtain a product. If the annealing rate is set to 1000 ° C./hour during the annealing, the precipitation of Fe can be prevented and the crystal grains can be further refined.

Cast plate thickness: 3 to 20 mm When the cast plate thickness is less than 3 mm, the rolling rate in the final product becomes small, and problems such as strength and formability occur. Further, the casting speed of the thin plate continuous casting machine is about 1 m / min, which is lower than the rolling speed of the rolling mill of about 1000 m / min.
Extremely slow. Therefore, when the cast plate is thin, the productivity is reduced. On the other hand, if the plate thickness exceeds 20 mm, center segregation is likely to occur during casting, resulting in uneven hardness of the plate, which makes rolling difficult. Further, in order to reduce the plate thickness, it is necessary to perform hot rolling, which increases the cost. Therefore, in order to omit the hot rolling step and improve the productivity, it is preferable to set the cast plate thickness in continuous casting to 3 to 20 mm.

Further, it is preferable to use a casting roll for casting. As a result, a uniform high cooling rate can be obtained on the surface, the microstructure and the grain structure can be made fine and uniform, and the crystallized substances can be finely and uniformly distributed to further reduce segregation. . That is, the cooling rate on the plate surface is determined by the contact state between the mold and the molten metal. In a normal DC casting method, this contact state is almost uncontrollable and is determined by the balance between the surface tension of the molten metal, the weight of the molten metal and the surface tension of the lubricating oil. For this reason, the contact pressure between the casting mold and the molten metal is usually very weak, and a large difference occurs between parts. Therefore, the thermal conductivity between the mold and the molten metal is extremely low and non-uniform,
The microstructure and the grain structure become coarse and non-uniform. On the other hand, when a casting roll is used, the contact pressure between the molten metal and the mold is determined by the pressure of the roll and can be made extremely high and uniform, so that a high heat transfer coefficient is obtained. To be For this reason, the cooling rate becomes higher and uniform, and as a result, the crystallized substances can be finely and uniformly distributed.

Temperature rising rate for the first annealing: 1000
When the rough annealing, the intermediate annealing and / or the final annealing is performed after the continuous casting at ℃ / hour , at least the temperature rising rate of the first annealing is preferably 1000 ℃ / hour or more. By setting the heating rate in this way, it is possible to prevent Fe from precipitating during heating. Fe is precipitated by diffusion in the aluminum matrix, but this precipitation is usually apt to occur in places where there are lattice defects such as on shear bands and crystallized substances. When precipitation occurs on such defects,
As a result, the strain becomes smaller and it becomes difficult to form recrystallization nuclei. However, since this diffusion phenomenon is extremely slow, if the temperature rising rate in the rough annealing, the intermediate annealing and the final annealing is increased and the recrystallization temperature is set before Fe diffusion occurs,
The recrystallized grains can be made finer. However, if most of Fe is precipitated in the first heat treatment, it is not always necessary to increase the temperature rising rate in the subsequent heat treatment process. Therefore, when performing the rough annealing, the intermediate annealing and / or the final annealing, it is preferable that the temperature rising rate of at least the first annealing is 1000 ° C./hour or more.

[0043]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples. In Table 1 below, Example No. 1-9
And Comparative Example No. The chemical composition of aluminum alloys 10 to 17 is shown. Each alloy shown in Table 1 was used as a cast plate having a thickness of 4 mm by using a casting roll, and the amount of Fe solid solution of this plate and the number of crystallized substances having a diameter of 4 μm or more were examined by SEM. Then, this cast plate was subjected to rough annealing at a temperature of 480 ° C. for 15 minutes. The temperature rising rate in this rough annealing is 4
It was set to 800 ° C./hour. Next, after cold rolling to 0.1 mm, the temperature is raised at a temperature rising rate of 40 ° C./hour, and further 35
Final annealing was performed at a temperature of 0 ° C. for 2 hours, and the grain size of each obtained aluminum alloy plate was investigated. The results are shown in Table 2 below.
Shown in

[0044]

[Table 1]

[0045]

[Table 2]

As shown in Table 2 above, Example No. 1 to
In No. 9, since its chemical composition is within the range specified in the present invention, excellent characteristics are obtained, and since the Fe content is 2% by weight or less, the solid solution amount of Fe is 0.3. Less than 1% by weight, and the content of Cr is 0.001% by weight
Therefore, the number of crystallized substances with a diameter of 4 μm or more is 2
The number is 0 / mm ² or more, and the crystal grains are miniaturized.

On the other hand, in Comparative Example No. 10, 12, 14, 1
In Comparative Examples Nos. 6 and 17, the crystal grains became coarse, and Comparative Example Nos. In Nos. 11, 13, and 15, rolling failure occurred, and none of them was satisfactory. In addition, Comparative Example No. No. 16 has a chemical composition within the range specified in the present invention, but has a relatively large Fe content, and T
Since the contents of i and Cr are the lower limits specified in the present invention, the solid solution amount of Fe becomes larger than the range specified by the present invention, which causes coarsening of crystal grains.

Next, the relationship between the temperature rising rate and the grain size in the rough annealing, the intermediate annealing and the final annealing was investigated. An aluminum alloy having the chemical composition shown in Table 3 below was cast into a plate having a thickness of 7 mm using a casting roll. The obtained cast plate was divided, and a part thereof was subjected to rough annealing treatment at a temperature of 500 ° C. for 20 minutes under the temperature rising conditions shown in Table 4 below, followed by cold cooling to a thickness of 1 mm. Rolling, then
Under the temperature raising conditions shown in Table 4, after performing intermediate annealing at a temperature of 380 ° C. for 10 minutes, cold rolling was performed so that the thickness was 0.1 mm, and further the temperature raising conditions shown in Table 4 were applied. 400 ℃
The final annealing was performed at the temperature of 2 hours. The results of investigating the grain size of the obtained aluminum alloy plate are shown in Table 5 below.

[0049]

[Table 3]

[0050]

[Table 4]

[0051]

[Table 5]

The invention A in the remarks column of Tables 4 and 5
In the rough annealing, the intermediate annealing or the final annealing, when the temperature rising rate of at least the first annealing is 1000 ° C./hour or more, the present invention B has a temperature rising rate of the second annealing of 1000. ℃ / hour or more, and heating rate is 100
The case of less than 0 ° C./hour is shown.

As shown in Table 5 above, by selecting the temperature rising rate of at least the first annealing of the rough annealing, the intermediate annealing or the final annealing to be 1000 ° C./hour or more, the crystal grains become finer. A converted aluminum alloy plate can be obtained.

[0054]

As described above, the aluminum alloy sheet according to the present invention contains the alloying additive element defined in the present invention, and the crystallized product is enlarged, so that the crystal grains are refined. Therefore, there is an effect that the appearance and rolling property are excellent.

Claims (8)

[Claims] 1. An aluminum alloy plate produced by continuous casting, wherein Fe: 0.3 to 2.0 wt%, T
i: 0.001 to 0.2% by weight and Cr: 0.001
To 0.1% by weight, the balance consisting of Al and inevitable impurities, and the solid solution amount of Fe is 0.3% by weight or less,
An aluminum alloy plate characterized in that the number of crystallized substances having a diameter of 4 μm or more is 20 / mm ² or more. 2. Further, Mg: 0.5% by weight or less and Cu:
The aluminum alloy plate according to claim 1, which contains one or more elements selected from the group consisting of 0.4% by weight or less. 3. The aluminum alloy plate according to claim 1 or 2, further comprising Mn: 0.5% by weight or less. 4. The method according to claim 1, further comprising B: 0.1% by weight or less.
The aluminum alloy plate according to the item. 5. The aluminum alloy plate according to claim 1, wherein the aluminum alloy plate has a plate thickness of 3 to 20 mm immediately after completion of the continuous casting. 6. The continuous casting is performed one or more annealing treatments, and the annealing treatment performed first in the annealing treatments has a temperature rising rate of 1000 ° C./hour or more. The aluminum alloy plate according to any one of claims 1 to 5, wherein: 7. The aluminum alloy sheet according to claim 6, wherein the annealing treatment at a heating rate of 1000 ° C./hour or more is performed after cold rolling after the continuous casting. 8. The aluminum alloy sheet according to claim 7, wherein cold rolling is performed after the annealing treatment at a temperature rising rate of 1000 ° C./hour or more.