JPH11256294A - Production of aluminum alloy sheet suitable for alkali treatment, aluminum alloy sheet, and formed part of aluminum alloy sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce, with high productivity, an aluminum alloy sheet free from occurrence of striped pattern at the surface to be treated even if alkali treatment is applied. SOLUTION: An aluminum alloy ingot, having a composition consisting of, by weight, >0.40-1.5% Fe, 0.03-0.30% Si, 0.004-0.20% Cu, 0.01-0.05% Ti, 0.0001 0.02% B, and the balance aluminum with inevitable impurities, is subjected to homogenizing treatment at 350 to 430 deg.C, and successively, hot rolling by plural pases is applied to this ingot to form a hot rolled plate. At this time, hot rolling is started at a temperature not exceeding the finishing temperature of homogenizing treatment, and hot rolling is performed without causing recrystallization before the final pass among the plural passes and at least the surface layer of the hot rolled plate is recrystallized by the final pass alone to form a recrystallized structure having <50 μm average recrystallized grain size in a direction perpendciualr to rolling direction. Then, cold rolling is applied to the hot rolled plate.

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 sheet suitable for alkali treatment, which can provide a high-productivity aluminum alloy sheet having a beautiful surface free of streak patterns by alkali treatment. The present invention relates to an aluminum alloy plate produced by the method described above and an aluminum alloy plate molded product obtained by molding the aluminum alloy plate.

[0002]

2. Description of the Related Art Aluminum alloys are used for pottery, pots and other objects, interior and exterior panels, etc. due to their good formability and good surface treatment properties. These objects or panels are generally manufactured as follows. That is, a molten metal is cast into an ingot, the ingot is homogenized at a high temperature, and then subjected to hot rolling and cold rolling to obtain an aluminum alloy sheet having a desired thickness. Usually, it is wound into a coil after cold rolling. The obtained aluminum alloy plate is formed into a predetermined size to obtain a product shape such as a panel or a container. Molded products such as panels and objects obtained are generally
A surface treatment such as an anodic oxidation treatment is performed to impart characteristics such as decorativeness and corrosion resistance.

This surface treatment is performed as follows. First,
As a pretreatment, the alloy plate or the molded product is washed with an acidic aqueous solution such as sulfuric acid or an alkaline aqueous solution such as caustic soda, or an aqueous solution of both. By this treatment, the surface is slightly etched, and stains such as oils and fats or oxides on the surface are removed. Next, an anodizing treatment is performed in an electrolytic bath such as sulfuric acid or oxalic acid to form an oxide film. Further, the above-mentioned plate or molded article having the oxide film formed thereon is electrolytically colored to a desired color by a secondary electrolytic treatment, if necessary.

Conventionally, an aluminum alloy plate used for forming and subsequent surface treatment as described above is obtained by subjecting an ingot to homogenization at a high temperature of 450 to 600 ° C. as described above.
It is manufactured by hot rolling and annealing in the middle of cold rolling (Japanese Patent Laid-Open No. 5-202453).

[0005]

However, the above-mentioned conventional manufacturing method involves subjecting the ingot to homogenization at a high temperature, and thus has a drawback that the heat treatment time is long and the productivity is low. Accordingly, an object of the present invention is to provide a method for producing an aluminum alloy plate having no streak pattern on a surface to be treated even with an alkali treatment with high productivity, and an aluminum alloy plate and an aluminum alloy plate molded product produced thereby. To provide.

[0006]

In order to solve this disadvantage of low productivity, the present inventors produced an aluminum alloy sheet by homogenizing the ingot at a low temperature and hot rolling at a low temperature. However, a molded article molded from the obtained aluminum alloy plate has been completed by obtaining the knowledge that no stripe pattern is generated on the surface to be treated even when the above-described alkali treatment is performed.

That is, according to the present invention, there are provided the following components: Fe: 0.40
Over 1.5 wt%, Si: 0.03-0.30 wt%
%, Cu: 0.004 to 0.20 wt%, Ti: 0.01
A 0.05% by weight, B: 0.0001 to 0.02% by weight, and the balance: an aluminum alloy ingot composed of aluminum and unavoidable impurities is prepared, and the ingot is subjected to a temperature of 350 to
When the ingot is subjected to a homogenization treatment at 430 ° C. and subsequently the ingot is subjected to hot rolling in a plurality of passes to form a hot-rolled plate, the hot rolling is started at a temperature not exceeding the end temperature of the homogenization treatment. And
Hot rolling is performed without recrystallization before the final pass of the plurality of passes, and at least the surface layer of the hot rolled plate is recrystallized only by the final pass, and the average recrystallized size in a direction perpendicular to the rolling direction is 50 μm. Less than the recrystallized structure,
A method for producing an aluminum alloy sheet suitable for alkali treatment, wherein the hot-rolled sheet is subjected to cold rolling.

When the ingot is homogenized at a low temperature and at least the surface layer of the hot-rolled sheet is recrystallized only by the final pass, the average recrystallized grain size in a direction perpendicular to the rolling direction is less than 50 μm. Thus, even if the plate or the processed product obtained from the cold-rolled plate-shaped coil is subjected to alkali treatment, the stripe pattern is not visually observed. The rolling rate of the last pass of the hot rolling is 55
% Or more, the average recrystallized grain size in the direction perpendicular to the rolling direction described above is easily reduced to fine recrystallized grains having a size of less than 50 μm, and no streak pattern is formed by the subsequent alkali treatment.

The recrystallized structure preferably has a recrystallized grain size in a direction perpendicular to the rolling direction of 100 μm or less. Similarly, a molded article formed from the plate-shaped coil obtained by the above-described production method does not have a stripe pattern due to alkali treatment.
One of the features of the method according to the present invention is that the ingot is homogenized at 350 to 430 ° C., which is lower than before.
By this homogenization treatment, the alloy element that has become a supersaturated solid solution during casting becomes a fine intermetallic compound and is uniformly precipitated. The uniformly dispersed fine precipitates have a pinning effect of supplementing dislocations introduced by hot rolling, and have an effect of preventing or delaying the progress of a recovery / recrystallization process occurring between passes during hot rolling. The dislocation pinning effect due to the uniform dispersion of fine precipitates also promotes uniform refinement of the recrystallized grain structure in the surface layer after the final pass of hot rolling.

Another feature of the method according to the invention is that it does not substantially undergo recrystallization during hot rolling, but only after the last pass. The recrystallization that occurs in a normal hot rolling process in a general aluminum alloy is substantially a static recrystallization between rolling passes. The uniformly dispersed fine precipitates described above effectively prevent the occurrence of recrystallization between passes. Due to this, the processing strain introduced into the material throughout the hot rolling process is accumulated and held until after the final pass, and in this state, recrystallization appears at once after the final pass, and extremely fine and highly uniform recrystallization. A grain structure is formed.

Conventionally, recrystallization during hot rolling is rather positively developed, and recrystallization is repeated for each pass, thereby finally producing a uniform and fine recrystallized grain structure. However, streaks or streaks could not be eliminated enough to satisfy the recent demand for higher quality. The reason is considered as follows. In other words, causing recrystallization for each pass means that the processing strain introduced in one pass is eliminated each time by recrystallization, and no large strain is formed. Although the strain introduced into the material by the rolling is macroscopically uniform, it is non-uniform microscopically or in terms of individual crystal grains, and the amount of strain differs for each region of the order of crystal grains. Therefore, even if a sufficient amount of strain is imparted to cause recrystallization sufficiently when viewed macroscopically, the strain required for recrystallization does not reach when viewed in each microscopic region on the order of crystal grains. Regions may remain. In addition, due to micro-segregation during casting, regions where the recrystallization temperature is high, that is, regions where large strain is required to develop recrystallization, and regions where the strength is higher than the surroundings and where deformation is difficult, that is, regions where distortion is hardly introduced, are scattered inside the material. doing. Due to the presence of such a region where the microscopic distortion non-uniformity and the material structure non-uniformity overlap, coarse and fine recrystallized grains appear after the final pass of hot rolling. Then, a non-uniform recrystallized structure is formed, and after the cold rolling, it remains as a streak or streak pattern having a non-uniform width in the perpendicular direction extending in the rolling direction and having a long width.

In the method of the present invention, recrystallization during hot rolling is not substantially caused, and the processing strain introduced in each pass is not eliminated to accumulate and maintain until after the final pass. Even if there is a non-uniformity of microscopic distortion and a non-uniformity of the material structure as described above, a uniform fine re- A sufficient amount of strain can be imparted to develop crystals, a uniform and fine recrystallized grain structure can be obtained, and streaks or streaks can be significantly reduced.

According to the present invention, the occurrence of recrystallization between hot rolling passes can be prevented by the uniform dispersion of fine precipitates, as described above, so that the hot rolling process itself is not changed in particular. The conventional hot rolling process may be used. Although it is necessary to manage so that the time between passes does not become too long, the management that has been performed conventionally to secure the material temperature is sufficient, and it is unlikely that the management items will increase substantially. Absent.

As described above, according to the present invention, the intermetallic compound is uniformly and finely dispersed by performing a homogenization treatment at a lower temperature than in the prior art, and the ingot in this state is hot-rolled, so that the conventional ingot is used actively. The development of recrystallization during the hot rolling, which had been performed, was prevented contrary to the conventional method, and recrystallization was caused at a stretch after the final pass. Thereby, particularly in the hot-rolled sheet surface layer, it is possible to easily obtain a very fine and uniform recrystallized grain structure having an average grain size of less than 50 μm in a direction perpendicular to the rolling direction, By performing the rolling, it is possible to manufacture an aluminum alloy strip coil in which no stripe pattern occurs on the surface to be processed even when the alkali treatment is performed. In addition, since the homogenization treatment is performed at a low temperature, the above-described strip coil can be manufactured with high productivity.

[0015]

First, the reasons for limiting the components of the aluminum alloy in the present invention will be described. Fe: more than 0.40 and 1.5 wt% or less Fe forms Al-Fe-based and Al-Fe-Si-based intermetallic compounds, imparts strength, and refines the crystal grains of the cast structure. Element required for If the Fe content exceeds 1.5 wt%, the Al-Fe system and Al
-A coarse compound of the Fe-Si system is formed, and the local unevenness of the alkali treatment becomes remarkable, and the formability of the plate is reduced. When the Fe content is 0.40 wt% or less,
For processed products such as panels and articles, the effects of reducing the crystallinity of strength and cast structure cannot be obtained, and the uniformity of the alkali treatment is impaired due to the presence of coarse crystal grains.

Si: 0.03 to 0.30 wt% Si is an element necessary for forming an Al-Fe-Si based intermetallic compound and imparting strength. If the Si content is less than 0.03% by weight, this effect is insufficient. on the other hand,
If the Si content exceeds 0.30 wt%, Al-Fe-S
A coarse i-type intermetallic compound is formed, and the local non-uniformity of the alkali treatment becomes significant. Si is an element usually contained as an impurity in an aluminum alloy.
If the i content is less than 0.03 wt%, the cost increases.

Cu: 0.004 to 0.20 wt% Cu is an element that greatly affects corrosion resistance. If the Cu content is less than 0.04 wt%, thread-like corrosion is likely to occur. On the other hand, if the Cu content exceeds 0.20 wt%, pitting corrosion and the like occur, and the corrosion resistance is reduced. Ti: 0.010 to 0.050 wt% Ti is effective for refining the crystal grains of the cast structure. Therefore, it is useful for preventing the occurrence of cracks during casting, and is also effective for uniformity of alkali treatment caused by coarsening of the crystal structure of the casting structure. If the Ti content is less than 0.010% by weight, the effect of refining the crystal grains of the cast structure is small. On the other hand, Ti
If the content exceeds 0.050 wt%, not only the effect of refining the crystal grains of the cast structure is saturated, but also the content of Al-
A coarse Ti-based compound is formed, and the crystal grains of the cast structure become non-uniform.

B: 0.0001 to 0.020 wt% B is added together with Ti and is effective for refining the crystal grains of the cast structure. The result is higher than when only Ti is added. When the B content is less than 0.0010 wt%, this effect is small. On the other hand, when the B content exceeds 0.020 wt%, not only the effect of refining the crystal grains of the cast structure is saturated, but also a coarse Ti-B-based compound is formed, and the crystal grains of the cast structure are reduced. Becomes uneven.

As impurities or significant elements, Mg, M
Elements such as n, Cr, Zr, V, Zn, Ni, Ga, Li, and Be may be contained. May be contained,
Preferably, the content is as small as about 0.1 wt% or less, so that the effects of the present invention are not significantly affected.
In the present invention, the recrystallized grain structure of the surface layer of the hot rolled sheet is controlled as follows.

An aluminum alloy having the above composition, which has been subjected to slag removal treatment and the like, is cast by a conventional method to form an ingot. The casting method is not particularly limited, but a semi-continuous casting method is desirable. The thickness of the ingot is not particularly limited, but is usually 500 to 600 mm.
It is about. After chamfering the surface of the ingot, 350-43
The homogenization treatment is performed by heating and maintaining the temperature at 0 ° C. The holding time of the homogenization treatment is suitably about 30 minutes to 12 hours. As described above, one of the features of the present invention is that the homogenization treatment is performed at a lower temperature than before. During this low-temperature homogenization treatment, the alloy element that was supersaturated in solid solution during casting was uniformly and finely precipitated as an intermetallic compound, and the pinning effect that supplemented the dislocations introduced by processing in the subsequent hot rolling step resulted in a thermal effect. Prevents the development of recrystallization during hot rolling.
The temperature of 350 to 430 ° C. is the most preferable temperature for uniformly and finely precipitating the alloy element in the supersaturated solid solution as an intermetallic compound during casting. On the other hand, the number of fine intermetallic compounds that are effective for capturing dislocations decreases, and it is not possible to reliably prevent the onset of recrystallization during hot rolling. A recrystallized grain structure cannot be generated. The holding time of the homogenization treatment is 30
If the retention time is less than 1 minute, the precipitation is not sufficient.
If the time exceeds 2 hours, there is a risk that the precipitated particles may re-dissolve at a high temperature, even within the temperature range of the present invention, and the cost increases. Since the present invention performs the homogenization treatment at a lower temperature than in the prior art, it is advantageous in energy saving.

After the homogenization treatment, hot rolling is generally performed by several or more rolling passes. In the present invention, it is essential that recrystallization does not occur during hot rolling. Therefore, the presence of fine precipitates generated by the homogenization treatment is important. These fine precipitates delay the onset of recrystallization.
This is because the fine precipitates supplement or pin the dislocations introduced as the processing strain of hot rolling, and prevent the recovery and recrystallization processes from starting and progressing. In this way, the occurrence of recrystallization during hot rolling is prevented, and the processing strain is accumulated and stored until after the final pass, and after the final pass, recrystallization is developed at once, so that uniform fine refining is achieved on the hot-rolled sheet surface layer. Generate a grain structure.

The hot rolling may be started immediately after the homogenization treatment, or may be started after the surface of the ingot is chamfered and reheated to a predetermined temperature after the homogenization treatment. In the present invention, in order to control the structure between the hot rolling passes and the structure after the completion of the hot rolling, it is essential to control the homogenization treatment conditions. In addition, when the starting temperature and the ending temperature of the hot rolling are controlled, the raw sheet of the present invention can be easily manufactured.

The hot rolling start temperature is set at a temperature not exceeding the homogenizing treatment end temperature. That is, 300 to 430 ° C. is desirable. If the temperature is lower than 300 ° C., stable hot rolling is difficult due to high rolling resistance. On the other hand, when the hot rolling start temperature increases, recrystallization easily occurs between passes at a normal hot rolling speed, and recrystallized grains are also easily grown, processing strain is easily released, and as a result, until after the final pass. It becomes difficult to accumulate and hold processing strain and express recrystallization at a stretch,
In particular, it is difficult to generate a uniform and fine recrystallized grain structure in the surface layer of the hot-rolled sheet, and coarse recrystallized grains are easily generated.

The end temperature of the hot rolling is 200 to 380 ° C.
Is desirable. At the end of hot rolling, the thickness is 2 to 10 mm.
Is desirable. By setting the end temperature and end plate thickness in this range, it is possible to easily recrystallize by the residual heat of the material itself by simply allowing it to cool without the need for special heating or heat insulation after the final pass of hot rolling. And a sheet thickness convenient for cold rolling in a subsequent step can be obtained. More preferably, the thickness at the end of hot rolling is 3.5 to 7 mm.

It is desirable that the rolling reduction (= rolling reduction, reduction) in the final pass of hot rolling is 55% or more. In the present invention, since the recrystallization is developed after the final pass, the processing strain due to the final pass has the greatest effect on the recrystallization. Therefore, if a larger working strain is imparted to the rolling ratio in the final pass, it is very advantageous to finally generate a uniform and fine recrystallized grain structure in the surface layer of the hot-rolled sheet. That is, by performing the final pass at a rolling rate of 55% or more, the average recrystallized grain size in a direction perpendicular to the rolling direction in at least the surface layer of the hot-rolled sheet is 50 μm.
, And similarly, a maximum grain size of less than 100 μm is readily obtained.

In the present invention, the surface layer of the hot-rolled sheet is a region from the sheet surface to a depth of about 1 mm in the case of a hot-rolled sheet having a thickness of 10 mm or less. Ultimate thickness 1-2mm
About 0.1 mm of the surface of the alloy plate is removed by etching by alkali treatment. As a typical example, when the hot-rolled plate has a thickness of 3.5 to 7 mm, the surface layer refers to an area between 350 μm and 700 μm in depth.

When the thickness of the hot-rolled sheet is 10 mm or less, the size of the recrystallized grains in the surface layer does not substantially change in the sheet thickness direction. The evaluation of the recrystallized grain size of the sheet surface layer can be obtained by measuring the recrystallized grain size of the hot rolled sheet surface. In the present invention, it is sufficient that at least the surface layer of the hot-rolled sheet has a uniform and fine recrystallized grain structure. That is, the core of the hot-rolled sheet may be of any type, regardless of whether it has a uniform and fine recrystallized structure. This is because the streaks or the streak pattern of the panel or the object become obvious by the alkali treatment, and the core of the plate does not directly participate in the generation of the streak or the streak pattern.

Determination of whether or not recrystallization has occurred during hot rolling can be easily performed by observing the structure of the material immediately before the final pass of hot rolling. When recrystallization is not performed during hot rolling, a crystal structure of the cast structure becomes a fibrous processed structure elongated in the rolling direction. On the other hand, when recrystallization is performed during hot rolling, the fibrous structure formed before the recrystallization disappears. Elongation rate of the structure is small or the processed structure has disappeared.

According to the present invention, as described above, an aluminum alloy base plate for a lithographic printing plate is manufactured through casting, facing, homogenizing treatment, hot rolling, and cold rolling. Intermediate annealing and / or final annealing after the end of cold rolling may be performed. Further, after the end of cold rolling, leveler correction for improving flatness can be performed.

Intermediate annealing or final annealing during cold rolling may be performed as necessary. The annealing method in that case may be either batch annealing or continuous annealing. The batch annealing is typically performed at a temperature of 200 to 600C and a holding time of 1 to 24 hours. If the temperature is lower than 200 ° C., annealing hardening for removing work hardening due to cold rolling is insufficient.
If the temperature exceeds 600 ° C., recrystallized grains become coarse, and a roughened surface having high uniformity in appearance cannot be obtained by an electrochemical method, and mechanical properties are also deteriorated, so that good printing durability cannot be obtained.
If the holding time is less than 1 hour, the annealing effect for removing the processing effect is insufficient. If the holding time exceeds 24 hours, the annealing effect will be saturated, which is simply uneconomical.

The continuous annealing is typically performed using a continuous annealing apparatus at a heating rate of 1 ° C./sec or more and a heating temperature of 350 to 60 ° C.
After heating to 0 ° C and reaching a predetermined temperature, the temperature was raised at a rate of 1 ° C /
It is carried out by cooling to 100 ° C. or less by water cooling at a rate of 500 ° C./sec or more, desirably for at least sec. The continuous annealing apparatus is not particularly limited, but the heating method is magnetic induction heating (Tran) using the heat generated by the aluminum alloy itself.
The sverse flux induction heating method is preferable because the amount of oxide film formed on the surface of the aluminum alloy plate is small and the adverse effect on the plate surface is small.

[0032]

EXAMPLES A melt of an aluminum alloy having the composition of the present invention shown in Table 1 was prepared. Each aluminum alloy melt was semi-continuously cast into a 560 mm thick ingot, and the surface of the ingot was chamfered by 15 mm on both sides to 530 mm. Next, after performing the homogenization treatment, hot rolling was performed using a reversible rolling mill to obtain a hot-rolled plate having a thickness of 6 mm. The hot rolling is performed with 17 passes, and the time between passes is 10 sec to 1.
It was within the range of 5 min.

Table 2 shows the homogenizing treatment temperature and time, the hot rolling start temperature, the end temperature, and the final rolling pass reduction.
Sample No. Samples Nos. 1, 2, and 3 were at least one of the conditions outside the scope of the present invention. Conditions 4 and 5 are within the scope of the present invention. Then, the sample No. 1,3,4 are
After performing cold rolling to a thickness of 2.5 mm in cold rolling, a batch type intermediate annealing is performed at a temperature rise of 100 ° C./sec for 1 hour, and a final cold rolling is performed to obtain a thickness of 1 mm.
Cold-rolled plate.

On the other hand, no. Samples 2 and 5 were subjected to cold rolling to form cold-rolled plates having a thickness of 2 mm. For the alloy plate obtained by the plate making process in Table 2, the width of crystal grains in the direction perpendicular to the rolling direction of the surface layer portion of the hot-rolled finished plate was measured according to the following evaluation and measurement methods, and the surface of the surface after alkali treatment was measured. Muscle evaluation was performed. Table 3 shows the results. (1) Measurement of recrystallized grain size of surface layer of hot finished plate After anodic oxidation treatment with Barker's solution (11 ml / l borofluoric acid solution), crystal grains were observed by a polarizing microscope.
The grain size was measured using the linear method. Thereby, the average recrystallized grain size and the maximum grain size were obtained. (2) Evaluation of surface streak after alkali treatment The obtained alloy plate was cut, and 10% NaOH, 50 ° C., 2
After the min etching, a desmut treatment was performed with HNO3.

The surface streak pattern was evaluated by visual observation of the surface. The evaluation was “very good (◎)” for a very uniform appearance, “good (○)” for a uniform appearance and no streak pattern, and a streak pattern was observed without uniform appearance. The result was evaluated as "poor (x)". In addition, in order to determine the presence or absence of recrystallization during hot rolling, the structure of the hot rolled sheet immediately before the final hot rolling pass was observed for each sample in Table 2. As a result, the present invention example use No. In Nos. 4 and 5, a fibrous work structure in which crystal grains were elongated in the rolling direction was observed, and it was confirmed that recrystallization did not occur during hot rolling. Sample No. Samples Nos. 1, 2, and 3 had a low elongation rate of crystal grains, and it was confirmed that recrystallization occurred during hot rolling.

As is clear from Table 3, the sample No. of the present invention was used. In No. 4, the average recrystallized grain size of the surface layer portion of the hot-finished rolled sheet was 25 μm and the maximum recrystallized grain size was 70 μm because recrystallization was not performed during hot rolling as described above.
A fine and uniform recrystallized grain structure of μm was obtained. For this reason, no stripe pattern was observed on the surface after the alkali treatment, and a very uniform and good appearance was exhibited. It can be seen that since the homogenization temperature is low, the time required for the homogenization processing is short, and the productivity is good.

Further, in the sample No. In No. 5, the average recrystallized grain size of the surface layer of the hot-finished rolled sheet was 15 μm and the maximum recrystallized grain size was 40 μm, because the recrystallization was not performed during the hot rolling as described above. A grain structure was obtained. As a result, no streaks were observed on the surface after the alkali treatment, and the surface had a uniform appearance. Since the homogenization treatment temperature is low, the time required for the homogenization treatment is short, and the intermediate annealing can be omitted, indicating that the productivity is very good.

On the other hand, the sample No. In No. 1, recrystallization occurred during hot rolling, and the average recrystallized size of the surface layer of the hot-rolled sheet was 120 µm, and the maximum recrystallized size was 150 µm. However, by performing the intermediate annealing treatment, no stripe pattern was observed on the surface after the alkali treatment, and the surface had a uniform appearance. However, since the homogenization treatment temperature is high and the hot rolling start temperature is low, the time for the homogenization treatment and the cooling to the hot rolling start temperature is very long, and furthermore, since intermediate annealing is also performed, It turns out that productivity is not good.

Further, the sample No. In No. 2, recrystallization occurred during hot rolling, and the average recrystallized size of the surface layer of the hot-rolled sheet was larger than 250 μm, and the maximum recrystallized size was 350 μm. The pattern was remarkable. Furthermore, it turns out that the homogenization processing temperature is high, it takes time to raise the temperature, and the productivity is not good.

In addition, the sample No. of the comparative example. In No. 3, recrystallization occurred during hot rolling, and the average recrystallized size of the surface layer of the hot rolled sheet was 180 µm, and the maximum recrystallized size was 250 µm. Therefore, even when the intermediate annealing treatment is performed, the streak pattern of the surface appearance after the alkali treatment is remarkable.
Furthermore, the fact that the homogenization treatment temperature is low, but the hot rolling start temperature is high means that further heat treatment is required, and that intermediate annealing is also performed, so that productivity is not good.

[0041]

[Table 1]

[0042]

[Table 2]

[0043]

[Table 3]

[0044]

As described above, according to the present invention,
By homogenizing the ingot at a low temperature and hot rolling at a low temperature, it is possible to produce an aluminum alloy plate having no streak pattern on the surface to be processed even with an alkali treatment with high productivity.

──────────────────────────────────────────────────の Continuation of front page (51) Int.Cl. ⁶ Identification code FI C22F 1/00 613 C22F 1/00 613 682 682 683 683 683 685 685Z 691 691B 694 694A 694B (72) Inventor Tomohide Yamagishi Inazawa, Aichi Prefecture 1-11-1 Koike Nippon Light Metal Co., Ltd. Nagoya Plant (72) Inventor Kazumitsu Mizushima 1-11-1 Koike Inazawa City, Aichi Prefecture Nippon Light Metal Co., Ltd. Nagoya Plant

Claims (5)

[Claims] 1. The following components: Fe: more than 0.40 and 1.5% by weight or less, Si: 0.03 to 0.30% by weight, Cu: 0.004 to 0.20% by weight, Ti: 0.01 to 0% An aluminum alloy ingot consisting of .05 wt%, B: 0.0001 to 0.02 wt%, and the balance: aluminum and unavoidable impurities was prepared, and the ingot was subjected to a homogenization treatment at a temperature of 350 to 430 ° C. When the ingot is subjected to a plurality of passes of hot rolling to form a hot rolled plate, the hot rolling is started at a temperature not exceeding the end temperature of the homogenization treatment, and before the final pass of the plurality of passes. Hot rolling without recrystallization, recrystallizing at least the surface layer of the hot rolled sheet only by the final pass,
A method for producing an aluminum alloy sheet suitable for alkali treatment, characterized by having a recrystallized structure having an average recrystallized size in a direction perpendicular to the rolling direction of less than 50 µm, and subjecting the hot-rolled sheet to cold rolling. 2. The method according to claim 1, wherein a rolling reduction in a final pass in the hot rolling is 55% or more. 3. The method according to claim 1, wherein the recrystallized structure has a maximum recrystallized grain size in a direction perpendicular to the rolling direction of less than 100 μm. 4. An aluminum alloy sheet suitable for alkali treatment, which is manufactured by the method according to claim 1, 2, or 3. 5. An aluminum alloy sheet molded article suitable for alkali treatment, obtained by molding the aluminum alloy sheet obtained by the production method according to claim 1, 2, or 3.