JP4865425B2 - Method for producing aluminum alloy plate with excellent surface treatment - Google Patents

Description

  This invention can be used for interior and exterior panels for building materials, panels for various transportation equipment, electrical equipment panels, electrical components, optical equipment, kitchen equipment, other daily necessities, etc. The present invention relates to a method for producing an aluminum alloy plate for surface treatment that is used after being subjected to chemical or electrochemical surface treatment.

  In the interior / exterior panels for building materials and the panels of various devices, from the viewpoint of commercial value, it is strongly required that the surface quality is excellent and there are few defects in appearance. On the other hand, in this type of application, the surface of the material aluminum plate may be subjected to a surface treatment such as chemical or electrochemical etching, or further anodizing (alumite treatment) after etching. Therefore, it is desired that the material plate has excellent surface treatment properties such as etching properties, and does not cause appearance defects such as unevenness and streaks on the surface after the surface treatment. .

  Among various aluminum alloys, pure aluminum (JIS 1000 series) aluminum alloys are not so high in strength, but have good surface quality and relatively good surface treatment properties. It has been widely used for applications. However, it is usually required to have a certain degree of strength even in applications such as this type of panel. As a method for producing a pure aluminum-based aluminum alloy plate for applications such as panels that require good surface treatment and a certain level of strength, conventionally, an ingot is subjected to intermediate annealing after hot rolling of the ingot. Cold rolling is performed, or intermediate annealing is performed in the middle of cold rolling after hot rolling, and a hard plate having a tempering degree of H18 or H24 is often obtained by final cold rolling. In this way, the structure of the plate finished into a hard plate becomes a fibrous processed structure in which the structure obtained by cold rolling remains.

  On the other hand, recently, in order to save energy and reduce costs by reducing the number of processes, intermediate annealing for recrystallization between hot rolling and cold rolling as described above or in the middle of cold rolling is not performed. In many cases, a hot rolled sheet is self-recrystallized in the process of hot rolling, winding and cooling, and thereafter only cold rolling is performed to finish a hard plate.

  By the way, in general, in the process of manufacturing an aluminum alloy sheet, non-uniformly coarse recrystallized grains are often generated during hot rolling, and after the surface treatment is performed on the base plate due to the coarse recrystallized grains. In some cases, appearance defects such as streaks and unevenness may occur on the surface of the steel plate, and particularly when the hard plate is finished without performing the intermediate annealing as described above, the risk is high.

  Here, as a method of manufacturing an aluminum alloy sheet for surface treatment for applications such as panels that require excellent surface quality, for example, in Patent Document 1, the reduction amount and rolling temperature during hot rolling are optimized. Proposal to prevent the occurrence of streak and unevenness of the surface after surface treatment by preventing the occurrence of coarse recrystallization and regulating the grain size of the product plate and the size of the aggregate having the same crystal plane Has been.

  In Patent Document 2, after the surface treatment, the hot rolling conditions are regulated, and the contrast of light and darkness of the crystal grains on the surface of the material plate is dispersed (averaged) as an index for uniformly dispersing the crystal orientation of the product plate. Further, in Patent Document 3, among various crystal orientations in an aluminum alloy plate, the orientation density of S orientation crystal grains is 12 or more, and the orientation density of Cu orientation crystal grains is 10 or more. It has been proposed to improve surface properties by restricting to the above.

Japanese Patent Laid-Open No. 11-335761 JP 2000-119782 A JP 2000-96172 A

  As described above, in applications such as building interior / exterior panels and electrical equipment panels, surface quality is required to be excellent, and surface treatment such as etching is usually performed, so surface treatment properties It is desirable that appearance defects such as unevenness and streaks do not occur on the surface after the surface treatment, but it has been difficult to meet such requirements reliably and stably with the conventional method. .

  For example, in the proposal of Patent Document 1, it is possible to improve the appearance after the surface treatment to some extent by optimizing the hot rolling conditions. It is not always possible to obtain a good quality plate, especially in the process of finishing to a hard plate with the final cold rolled plate without intermediate annealing after hot rolling (or in the middle of the subsequent intermediate annealing). Has been confirmed by experiments by the present inventors.

  Further, as shown in Patent Document 2 and Patent Document 3, the method for controlling the crystal orientation certainly has an effect of improving the unevenness and streak after the surface treatment to some extent. When applied to the process of finishing to a hard plate by omitting annealing, it was difficult to improve the surface treatment property reliably and stably.

  As described above, in the manufacturing process in which self-recrystallization is performed in the hot rolling process and subsequent intermediate annealing is omitted, the temperature and reduction amount in each pass of hot rolling are compared with the process of recrystallization by intermediate annealing. These conditions greatly affect the recrystallization texture after hot rolling. Even if such a recrystallized texture changes to a rolled texture by subsequent cold rolling, the influence of the initial recrystallized texture remains as a history, which greatly affects the surface processability. On the other hand, the surface treatment itself for the product plate has recently been omitted in order to reduce costs, so the surface performance after the surface treatment is also easily affected by the base plate before the treatment. Even if the surface treatment process and conditions are changed, it is desirable that streaks and unevenness do not occur stably. For example, it is desired that good surface quality can be obtained even when the etching amount is reduced by using a deteriorated liquid for cost reduction in etching.

  However, the conventional method does not give sufficient consideration to these points, and therefore, it is not always possible to obtain an aluminum alloy plate for surface treatment that is reliable and stable and has excellent surface treatment properties (particularly etching properties). There is no actual situation.

  This invention has been made against the background of the above circumstances. By using a JIS 1000 series aluminum alloy as a raw material, self-recrystallization by hot rolling eliminates subsequent intermediate annealing, and finally by cold rolling. In the manufacture of aluminum alloy plates for surface treatment that are finished into hard plates, the surface treatment properties, especially the etching properties by chemical or electrochemical etching, are always reliable and stable, and the appearance after surface treatment is uneven and streaks ( It is an object to be able to stably obtain a surface-treated plate with few defects such as stripes).

  As a result of repeated experiments and studies by the present inventors in order to solve the problems as described above, by appropriately controlling the accumulation of strain in each pass from the final pass in hot rolling to several passes before , It is found that recrystallization after hot rolling can be controlled stably, and in particular, Z that is an index of accumulation of hot strain in each pass from the final pass to 2 passes before the hot pass (finishing 3 passes). Appropriately regulating the value (Zener-Holomon Parameter) based on the relationship with the rolling start temperature of each pass in order to reliably and stably obtain an aluminum alloy sheet excellent in surface treatment It was newly discovered that it was effective, and this invention was made.

Specifically, in the method for producing a surface-treated aluminum alloy sheet according to claim 1, hot rolling is started by heating a JIS 1000 series aluminum alloy ingot to a temperature within a range of 400 to 610 ° C. And, for each of the three passes of the hot rolling, for the up three passes, the rolling start temperature T in each pass is within the range of 280 to 480 ° C., and the Ln (Z) value in each pass (Note: Z is Zener-Holomon Parameter) represents the following formula −0.0645 × T + 55.5 ≦ Ln (Z) ≦ −0.0645 × T + 59.5 depending on the rolling start temperature T (° C.) of each pass.
The rolling is performed so as to satisfy the conditions, the hot rolling is finished at a temperature within the range of 270 to 370 ° C., and the structure of the portion from the surface of the plate to the position of at least 30% of the plate thickness in the thickness direction of the plate is A hot rolled up board having a recrystallized structure with an average crystal grain size of 100 μm or less is obtained, and then cold rolled.

  According to the method of manufacturing an aluminum alloy plate for surface treatment of the present invention, by using JIS 1000 series aluminum alloy as a raw material and recrystallizing by self-annealing in hot rolling, the subsequent intermediate annealing is omitted. In addition, when finishing into a hard plate by cold rolling, accumulation of hot strain in three passes (upward three passes) from the final pass in hot rolling to two passes before it is calculated as the hot rolling start temperature in each pass. By appropriately regulating under the relationship, the crystal size and crystal orientation density distribution after hot rolling can be stably controlled within a narrow range, and as a result, it is finished into a hard plate by final cold rolling. Even when surface treatment such as chemical or electrochemical etching is applied to the product plate, surface treatment such as etching is obtained stably. Can be a good plate appearance defect-free surface quality, such as unevenness or streaks (streaks) as a surface appearance, can reliably and stably. Therefore, for example, even in applications that require a uniform external color tone, such as building material panels, it is possible to provide a panel with no uneven color tone, and to provide excellent products for decoration. In addition, it is possible to provide a product having stable and good surface quality even if the surface treatment process and conditions are changed.

  In the method of the present invention, a JIS 1000 series aluminum alloy which is a so-called pure aluminum series is used as an aluminum alloy as a material. Since the JIS 1000 series aluminum alloy is excellent in surface treatment property and the surface appearance after the surface treatment such as etching is excellent, in this invention, the JIS 1000 series alloy was used. Here, the Ln (Z) value defined as the hot rolling condition in the method of the present invention depends on the deformation stress, but Mg, Mn, Si, which are positively added in alloys other than JIS 1000 series, If an alloying element such as Cu is added alone even at about 1%, a crystallized product or a precipitate is generated, affecting the deformation stress, and thus affecting the Ln (Z) value. Although it is difficult, if the content is as specified in the JIS 1000 series, there is little formation of crystallized products and products, so the Ln (Z) value can be controlled easily and appropriately. Therefore, it is appropriate to use a JIS 1000 series alloy in this respect as well.

  Next, the manufacturing method of this invention is demonstrated.

  First, as described above, a JIS 1000 series alloy is cast according to a conventional method such as a DC casting method to obtain an ingot (slab). The ingot is subjected to a homogenization treatment as necessary and then hot-rolled. The homogenization treatment conditions for performing the homogenization treatment are not particularly limited, but are usually 500 to 600 ° C. for about 1 to 10 hours. In addition, when performing homogenization treatment, it may be cooled to room temperature after homogenization treatment and then re-heated to hot rolling start temperature to perform hot rolling, or after homogenization treatment, it may be cooled to hot rolling temperature. Hot rolling may be performed immediately.

  The hot rolling conditions are extremely important in the method of the present invention, and by appropriately and strictly controlling this, it becomes possible to stably obtain a product plate having excellent surface treatment properties such as etching properties. .

  In this hot rolling, as will be described later, it is necessary to recrystallize at least once and control so that at least the surface layer portion has a fine recrystallized structure after the hot rolling is completed. From these viewpoints, the hot rolling start temperature is set within a range of 400 to 610 ° C., and the hot rolling end temperature is set within a range of 270 to 370 ° C.

  That is, when the hot rolling start temperature is less than 400 ° C., recrystallization hardly occurs during hot rolling, streaks are likely to occur on the surface after the surface treatment of the product plate, and hot rolling is performed at 270. It becomes difficult to complete the process at a high temperature range of ℃ or higher. On the other hand, if the hot rolling start temperature exceeds 610 ° C., the rolling of the recrystallized grains becomes coarse (in the thickness direction) in the case where the rolling is interrupted by cutting the crocodile mouth at the front and rear ends of the ingot during the hot rolling. There is a strong risk of causing a coarsening exceeding the particle size of 100 μm. Here, the recrystallized grains generated in the relatively early rough rolling in the hot rolling are the basis of the structure generated in the subsequent hot rolling process as the mother crystal grains, and the size of such mother crystal grains is also Since it affects the grain size of the recrystallized structure at the end of hot rolling, it is necessary to suppress the coarsening of recrystallized grains in the relatively early rough rolling of hot rolling. Therefore, in the present invention, the hot rolling start temperature is in the range of 400 to 610 ° C.

On the other hand, in the method of the present invention, at the end of hot rolling (when hot rolling is finished, coiled and cooled to room temperature), at least 30% in the thickness direction from the surface of the plate. It is necessary that the structure of this part is a recrystallized structure composed of recrystallized grains having an average particle size of 100 μm or less. When the hot rolling finish temperature (final pass rising temperature) is less than 270 ° C., the accumulation of strain is insufficient under the condition of Ln (Z) defined in the present invention, and the thickness of the plate extends from the surface of the plate to the thickness direction of the plate. It becomes difficult to stably recrystallize up to a portion of at least 30% . If the hot rolling end temperature is regulated to 270 ° C. or higher, it is possible to stably recrystallize from the surface of the plate to the position of at least 30% of the plate thickness in the thickness direction of the plate. If the rolling end temperature exceeds 370 ° C., the recrystallized grains may grow after winding on the coil, and the recrystallized grains may exceed 100 μm. Therefore, the hot rolling end temperature is set in the range of 270 to 370 ° C.

Here, as the structure of the hot rolled sheet after completion of hot rolling (after coil winding and cooling), the recrystallized grains in the portion from the surface of the sheet to the position of at least 30% of the sheet thickness in the thickness direction of the sheet If the diameter exceeds 100 μm, it may cause rough skin of the product plate, and good surface quality cannot be obtained. Further, when the portion from the surface of the hot rolled plate to the position of at least 30% of the plate thickness in the thickness direction of the plate is not a complete recrystallized structure (at least part of the portion within the 30% range is In the case of an unrecrystallized structure), the surface treatment property, which is the final object of the present invention, cannot be improved reliably and stably.

  Furthermore, in the method of the present invention, not only the hot rolling start temperature and end temperature are regulated as described above, but also the relationship between the strain rate and temperature in each of the three passes of hot rolling is appropriately regulated. This is very important. This will be described below.

  In general, hot rolling is generally performed by rough rolling by plate rolling (plate rolling) as the former stage and finish rolling by coil rolling as the latter stage. On the other hand, the finished thickness of hot rolling varies depending on the required performance and application of the product, but is usually usually finished to a thickness of about 2 to 10 mm. Here, the maximum rolling reduction that can be rolled in one pass varies depending on the plate thickness, but is limited to about 85% due to problems such as coating. Therefore, the hot rolling finish rolling is usually performed in a plurality of passes of 3 passes or more. In addition, suppose here that the pass of 1 step | paragraph also refers to the pass | pass of each stage | paragraph in the case of carrying out finish rolling by a multistage | paragraph pass with a multistage continuous rolling mill.

As a result of repeated detailed experiments and examinations by the present inventors paying attention to the relationship between the strain rate and temperature in rolling of each pass in finish rolling as described above, at least three passes of rolling including the final pass, It is possible to control the relationship between the Zener-Holomon Parameter (Z value), which is an index of hot strain accumulation, and the rolling start temperature in each pass to be within a specific range. They found it important to control. That is, in the method of the present invention, in order to appropriately control strain accumulation and recovery / recrystallization in each of the three passes in the hot rolling process, the rolling start temperature T in each of the three passes in the hot rolling process is 280 to 480 ° C. Within the range, between the natural logarithm value Ln (Z) of the Zn value and the rolling start temperature T (° C.), the following equation (1) −0.0645 × T + 55.5 ≦ Ln (Z) ≦ −0. 0645 × T + 59.5
... (1)
It was decided to perform rolling so that The relationship between such Ln (Z) value and hot rolling start temperature T (° C.) is shown in FIG. In FIG. 1, the shaded area is a range that satisfies the condition of the expression (1).

  Here, in order to finally terminate the hot rolling at 270 ° C. or higher, it is necessary to set the rolling start temperature T in each of the three passes to be 280 ° C. or higher. On the other hand, when the rolling start temperature T in each pass of three passes exceeds 480 ° C., it becomes difficult to satisfy the above formula (1) and to set the hot rolling end temperature to 370 ° C. or less. Therefore, the rolling start temperature in each pass in three passes is set in the range of 280 to 480 ° C.

  On the other hand, when the left side of the above equation (1) is not satisfied in any one or more of the three rising paths, that is, when the Ln (Z) value is less than −0.0645 × T + 55.5, each path Recovery occurs, and once recrystallized grains grow as they are, not only coarse recrystallized grains exceeding 100 μm are generated, but also the degree of recovery for each pass becomes unstable. As a result, the distribution and density of crystal orientation are not stable, and as a result, etching unevenness occurs when the product plate is etched.

  On the other hand, when the right side of the above equation (1) is not satisfied in any one or more of the three rising paths, that is, when the value of Ln (Z) exceeds −0.0645 × T + 59.5, every one path Is sufficient, but a path one pass before the final pass (if the number of passes is N, the Nth pass; hereinafter simply referred to as “N pass”) (hereinafter “N−1 pass”). ) And two passes before the final pass (hereinafter referred to as “N-2 pass”), non-uniform recrystallization occurs on the surface. At this time, when the recrystallized portion and the non-recrystallized portion are recrystallized again at the Nth pass, the size of the crystal grains is different, so when the product plate is finally etched. Depending on the etching conditions, stripe-like patterns are generated depending on the etching conditions, and the appearance quality is deteriorated. Therefore, in each of the three passes after the hot rolling, it is necessary that the relationship between the Ln (Z) value and the rolling start temperature T (° C.) satisfy the above formula (1).

Here, the Z value is, for example, as shown in pages 88 to 89 of the literature (aluminum material basics and industrial technology (issued by the Japan Light Metals Association, May 1, 1985). This means Zener-Holomon Parameter (unit: / second) that is an index of strain accumulation. If strain rate is E, activation energy is Q, gas constant is R, and temperature is T, the following equation (2) Z = E · exp (Q / RT) (2)
This is the value obtained by.

  In the present invention, in calculating the Z value, a value of 37,300 cal / mol was used as the value of the activation energy Q, and a value of 1.987 cal / mol · K was used as the gas constant R.

  As described above, not only the start temperature and end temperature of hot rolling are regulated, but also the structure of the final product plate is controlled by controlling the conditions of the three passes especially after hot rolling, In order to maintain the effect by such control of hot rolling, in the method of the present invention, after hot rolling, a product plate is formed only by cold rolling. That is, intermediate annealing for recrystallization is not performed again after hot rolling or during cold rolling. In addition, although the conditions of cold rolling are not specifically limited, in order to make it finally a hard plate of about H18 to H24, the final cold rolling may be performed at a rolling rate of about 20 to 97%.

  Alloys A and B shown in Table 1 were melted in accordance with a conventional method, and cast into a slab having a thickness of 550 mm by a DC casting method.

  The obtained slab was homogenized by holding at 560 ° C. for 2 hours, and then allowed to cool to room temperature. Thereafter, the rolled surface was chamfered by 10 mm per side, heated to 460 ° C. and heated for 2 hours, and then hot rolling was started. The hot rolling was performed up to an end plate thickness of 2 to 5 mm under conditions such that the rolling speed was 10 to 900 m / min per pass. After hot rolling, it was cold-rolled to a sheet thickness of 0.4 mm without intermediate annealing, finished as a hard product plate, and evaluated for appearance. The reason why the hot-rolling finished sheet thickness is different is that the adjustment is made by the cold rolling rate because the required mechanical properties are different even if the product sheet thickness is the same.

  In the method of the present invention, the appearance quality after the surface treatment of the product plate is determined by the conditions under which three passes of rising before the end of hot rolling are performed. In this embodiment, therefore, the material temperature at the start of each of the three passes, the material temperature at the end of hot rolling (rise temperature), and the strain rate E and Ln (Z) value at each pass starting plate thickness. I investigated. The results are shown in Tables 2 and 3.

  Moreover, about the case of manufacturing numbers 1-5, the Ln (Z) value and rolling start temperature T (degreeC) in each pass of 3 going up are shown in FIG. 2 according to FIG. 1, and the case of manufacturing numbers 6-10 The same is shown in FIG.

  In the above process, the average crystal grain size was measured for the surface of the hot rolled plate. Here, it is the very surface of the plate that affects the appearance when it is actually surface-treated. Therefore, in order to reduce polishing as much as possible, it is polished to about 5 μm with buff (to the extent that the rolling marks disappear), then finished by electrolytic polishing, and after polishing, anodized with Barker's solution, and then the surface is observed with a polarizing microscope. The crystal grains were measured. The measurement was performed by counting the number of grain boundaries crossing a line drawn in the direction perpendicular to the rolling direction by a cutting method on the photograph, and the average grain size was determined and shown in Table 4.

  Moreover, about the hot rolled up board, the crystal orientation distribution density of Cu orientation and S orientation was measured on the surface of the board. The distribution of orientation density is measured by using an X-ray diffractometer manufactured by Rigaku Corporation to create incomplete pole figures of {200}, {220}, {111}, and ODF (three-dimensional crystal orientation) based on them. Analysis). In these analyses, data obtained by measuring a sample having a random orientation made from aluminum powder is normalized for use in incomplete pole figure analysis of {200}, {220}, and {111}. As a file, the Cu and S azimuth densities, ie, {112} <111> and {123} <634> azimuth densities, were obtained as multiples of the samples having random orientations, and the results are shown in Table 4.

  Moreover, the surface treatment property was investigated about the finally obtained cold rolled sheet. Here, the surface treatment property is obtained by macro-etching the surface of the cold rolled plate using a mixed solution of pure water (500 ml) + hydrochloric acid (500 ml) + nitric acid (500 ml) + hydrofluoric acid (5 ml) as an etching solution. The presence or absence of unevenness was visually evaluated. As an evaluation method, a case where neither unevenness nor streaks are visually observed is acceptable (◯ mark), a case where unevenness is present is rejected (△ mark), and a case where a streak occurs is also rejected (× mark). The results are shown in Table 3.

  Production numbers 1 to 5 were all rolled under the conditions specified in the present invention, and in these cases, it was found that there were no streaks or unevenness on the surface after etching. Of these, in the case of production number 1, the average crystal grain size was slightly large at 80 μm, but the S orientation and the Cu orientation were sufficiently grown, so that the etching was performed with a good balance. In the case of production numbers 2 to 4, the S orientation was developed and showed good etching characteristics. Further, in the case of production number 5, although the development of the S orientation and the Cu orientation was somewhat low, the crystal grain size could be made finer, thereby showing stable etching characteristics.

  On the other hand, in the examples of production numbers 6 to 10, one of the conditions was outside the range defined in the present invention, and in these cases, unevenness or streaks occurred on the surface after etching. That is, first, in the comparative example of production number 6, the S orientation and the Cu orientation were developed as such, but the N-2 pass rolling was started from the region where the Z value was high, and the temperature at that time was Due to the high temperature of 422 ° C. or higher, streak-like unevenness that seems to be the effect was observed in the pattern that was partially recrystallized once at the start of the N-1th pass.

  Moreover, although the example of the production number 7 aimed at rolling in the area | region with a low Z value and became as fine a crystal grain as possible, since the Z value was too low, even if hot rolling was complete | finished at 368 degreeC and high temperature, Regardless, a strong streak appeared after etching. As for the example of production number 7, the microstructure of the cross section of the hot-rolled sheet was observed. As shown in FIG. 4, only a very small surface was recrystallized, and the majority was unrecrystallized. It turned out to be an organization. Further, in the example of production number 8, rolling was performed under the condition that the Z value was as high as possible based on the failure of the example of production number 7. In this example, the crystal orientation density was considerably developed with the S orientation of 18 and the Cu orientation of 12, which seemed to be etched relatively uniformly. However, since the average grain size was 105 μm, the final plate However, the crystal grains became coarse, and a slight difference in the etching rate for each crystal grain appeared as irregularities, resulting in severe unevenness of the surface after etching. And the example of production number 9 was also rolled in the region of the Z value as low as possible aiming for fine grains, the cross-sectional microstructure of the hot-rolled sheet became full thickness unrecrystallized as shown in FIG. Streaks occurred on the surface after etching. Furthermore, although the example of production number 10 was able to be rolled with good balance, the hot rolling finish temperature (rising temperature) was as low as 265 ° C. Therefore, as shown in FIG. 6, it was partially in the microstructure of the cross section of the hot rolled plate. This resulted in a structure that recrystallized only on the surface, and streaks were formed on the surface after etching.

It is a graph which shows the relationship between the Ln (Z) value and rolling start temperature T (degreeC) in each path | pass of up 3 pass prescribed | regulated by the method of this invention. It is a graph which shows the relationship between the Ln (Z) value and rolling start temperature T ((degreeC)) in each pass of 3 going up in the manufacture numbers 1-5 (all are examples of this invention) of an Example. It is a graph which shows the relationship between the Ln (Z) value and rolling start temperature T (degreeC) in each pass of the up 3 passes in the manufacture numbers 6-10 (all are comparative examples) of an Example. It is a cross-sectional structure | tissue photograph (50-times multiplication factor) of the hot rolled up board in the manufacture number 7 (comparative example) of an Example. It is a cross-sectional structure | tissue photograph (50-times multiplication factor) of the hot rolled up board in the manufacture number 9 (comparative example) of an Example. It is a cross-sectional structure | tissue photograph (50-times multiplication factor) of the hot rolled up board in the manufacture number 10 (comparative example) of an Example.

Claims (1)

About JIS 1000 series aluminum alloy ingot, it heats to the temperature within the range of 400-610 degreeC, and starts hot rolling, and, for each pass of uphill 3 passes among each pass of the hot rolling, each pass The rolling start temperature T in the range of 280 to 480 ° C., and the Ln (Z) value in each pass (Note: Z indicates Zener-Holomon Parameter) is the rolling start temperature T (° C.) of each pass. In accordance with the following formula: −0.0645 × T + 55.5 ≦ Ln (Z) ≦ −0.0645 × T + 59.5
The rolling is performed so as to satisfy the conditions, the hot rolling is finished at a temperature within the range of 270 to 370 ° C., and the structure of the portion from the surface of the plate to the position of at least 30% of the plate thickness in the thickness direction of the plate is A method for producing an aluminum alloy sheet excellent in surface treatability, characterized in that a hot rolled up board having a recrystallized structure with an average crystal grain size of 100 µm or less is obtained and then cold rolled.