TWI575078B - Aluminum alloy plate for cans - Google Patents

Description

Aluminum alloy plate for can lid

The present invention relates to an aluminum alloy plate for a can lid, and more particularly to an aluminum alloy plate for a can lid which has both high strength and excellent formability and excellent can openability.

A two-piece all-aluminum can, which is currently known as one of the packaging containers for beverages and foods, is a bottomed cylindrical body portion (can body, can body) in which the bottom and the side walls are integrally formed. And a disk-shaped lid portion (can lid, can end portion) which is an upper surface of the opening portion of the can body portion.

The material of such an aluminum can is classified into an aluminum alloy plate of AA grade to Japanese industrial specification JIS 3000 series (Al-Mn system) in the can body portion because of the difference in strength, formability, and the like required. In the can lid, an aluminum alloy sheet of AA grade to Japanese Industrial Standard JIS 5000 (Al-Mg) is used, and it is widely used.

Among these materials, the important characteristics required for the 5000-series aluminum alloy sheet for the can lid are, for example, the moldability which can withstand the processing of the can lid, and the compressive strength capable of withstanding the internal pressure of the can after the beverage is filled. Use The installed pull ring can be normally and simply opened to open the lid and the like.

In recent years, these can lids, which are 5000-type aluminum alloy sheets for can ends, have been required to be thinner to a thickness of about 0.2 mm, from the viewpoint of reducing the cost of the cans. As a technical subject of such a thinning, there is a problem that the pressure resistance is deteriorated, the formability is deteriorated, and the like. Among these technical problems, the deterioration of the compressive strength can be compensated for by increasing the material strength of the aluminum alloy sheet. However, as the strength is increased, the formability is deteriorated. Therefore, in order to make the aluminum alloy plate for a can lid thin, it is necessary to improve the strength together with the formability.

Even if the can lid is made thinner with the 5000-series aluminum alloy plate, the technique of retaining the strength of the material and improving the formability can be maintained, and the conventional method is for the intermetallic compound (opening property, formability), crystal grain size ( Organizations such as moldability, subgrains, or aggregate structures are subjected to various controls.

For example, in the above-described structure control of the 5000 series aluminum alloy plate for a can lid, the area ratio of the subgrains in the internal structure of the aluminum alloy plate is controlled to 3%. 30%, in order to improve the roundness and packageability when the can lid is wound on the can body.

In addition, in order to perform tissue control or to improve characteristics, intermediate annealing is performed on the way after hot rolling or cold rolling. However, in the case of mass-produced sheets, the ratio of manufacturing intermediate annealing to manufacturing costs is also large. . Therefore, there are many technical solutions such as patent documents. The technical solution disclosed in the second aspect of the invention is to perform cold rolling without performing intermediate annealing, and to perform tissue control at low cost to manufacture a 5000 series aluminum alloy plate for a can lid.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Kaiping No. 11-229066

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2003-105475

However, in the conventional 5000 series aluminum alloy sheets for can ends, there is still a technical problem of how to improve the rivet forming property at the time of forming the can lid. In the case where the strength is increased, the rivet formability is deteriorated. Therefore, in order to obtain excellent rivet formability, it is necessary to deteriorate the material strength.

Here, the can lid forming process will be described. First, after the material is punched into a circular plate shape, the casing is formed by a punching process, and then, in the conversion forming process, a rivet forming process is performed by a press machine to form a pull-up in the center of the casing. The convex part of the ring.

The rivet forming process is performed by a foaming forming process for causing the central portion of the can lid to be convex and convex, and the bulging portion (foaming) is used in one to three steps. It is composed of a button forming process in which a diameter is reduced to form a sharp protrusion.

After the rivet is formed, it is pressed by a die having a blade having a V-shaped cross section to form a groove of the water outlet portion, that is, the formation and execution of the score 3 as shown in FIGS. 2 and 3 It can increase the rigidity of the panel or the formation of characters. Then, the step of attaching the tab is performed, and the separately formed tab is caulked and attached to the convex portion formed in the center of the casing to be integrated.

At this time, in order to fix the tab normally, it is necessary to sufficiently ensure the diameter of the rivet after the protrusion. Therefore, the rivet formability required for the material is required to make the protrusion (button) after the button forming process is completed. The height reaches a full height.

On the other hand, even if the material sheet in which the area ratio of the sub-grains is controlled to 3 to 30% as shown in the above-mentioned Patent Document 1, if the strength is increased, the rivet formability will be deteriorated. In order to obtain excellent rivet formability, it is necessary to deteriorate the strength of the material. In other words, there is still a gap in the desire to have both excellent rivet formability and high strength.

Further, if cold rolling which is not subjected to intermediate annealing as shown in the above-mentioned Patent Document 2 or the like is used, it is possible to achieve both of the effects of such rivet formability and high strength by a low-cost manufacturing method. Technical issues yet to be resolved.

In view of such technical problems, an object of the present invention is to provide a technique for producing an aluminum alloy plate for a can lid, according to which aluminum can be produced can be produced even by cold rolling without intermediate annealing. Alloy sheet, the aluminum alloy sheet for the can lid, even with high material strength, can have sufficient rivet formability, and even after thinning, it has sufficient pressure resistance after filling of the beverage, and rivet formability And open canning is excellent.

The gist of the aluminum alloy plate for can lids of the present invention for solving the above problems is as follows.

An aluminum alloy plate containing Mg: 4.0 to 6.0% by mass, Fe: 0.10 to 0.50% by mass, Si: 0.05 to 0.40% by mass, Mn: 0.01 to 0.50% by mass, Cu: 0.01 to 0.30% by mass, and the rest is An aluminum alloy plate composed of Al and unavoidable impurities, which is subjected to cold-rolling without intermediate annealing, and subjected to baking coating, wherein the Mg is determined by the residue extraction method by hot phenol. The solid solution amount is 80% or more of the aforementioned Mg content, and is located in a field of 0.05 mm (that is, a thickness of 0.1 mm) from the center of the plate thickness toward the both sides in the thickness direction on a plane parallel to the rolling surface. The microstructure of the sub-grain area measured by a transmission electron microscope at a magnification of 50,000 times is an average of 10% or more and 90% or less.

In the above-mentioned gist, the aluminum alloy plate for a can lid preferably has a soaking treatment of the ingot to dissolve the Mg.

In other words, the method for producing an aluminum alloy sheet for a can lid according to the present invention is more preferably contained in the range of 4.0 to 6.0% by mass of Mg, 0.10 to 0.50% by mass of Fe, 0.05 to 0.40% by mass of Si, and Mn: 0.01. ~ 0.50% by mass, Cu: 0.01 to 0.30% by mass, and the rest is an aluminum alloy ingot composed of Al and unavoidable impurities, but is formed by soaking Mg to form a solution, and controlling the Mg after solid solution The hot-rolled sheet is formed by hot rolling, and the hot-rolled sheet is cold-rolled without intermediate annealing to form a cold-rolled sheet, after the cold-rolled sheet is subjected to baking coating treatment. In the state, the solid solution amount of Mg measured by the residue extraction method by hot phenol is set to 80% or more of the Mg content as a thickness from the plate which is parallel to the rolling surface. The tissue in the field of 0.05 mm (that is, the thickness of 0.1 mm) on both sides in the thickness direction is the sub-grain area ratio measured by a transmission electron microscope using a magnification of 50,000 times, on average More than 10% and less than 90% of the organization is preferred.

As described above, the structure and characteristics of the aluminum alloy sheet specified by the present invention are used as an aluminum alloy sheet for a can lid, that is, a pre-coated aluminum alloy sheet after being coated on a cold-rolled sheet and coated and baked. Alternatively, it is defined as the structure and characteristics of the can lid after molding the aluminum alloy sheet. Further, the cold rolled sheet may be subjected to a simulation of the structure and characteristics of the aluminum alloy sheet after the heat treatment is performed according to the specific conditions described later on the coating baking treatment.

The present invention is an aluminum alloy plate for a can lid which is increased in the sub-grain area ratio in a state after the baking and coating treatment after cold rolling, and has a structure in which the amount of Mg solid solution is increased. Formability and high strength Degree. Thereby, the present invention can achieve rivet formability and high strength which are difficult to achieve in the conventional art.

Therefore, the present invention does not require the material strength to be sacrificed in order to obtain the rivet formability as in the conventional art, and it is possible to achieve sufficient rivet formability even with high material strength. Therefore, even when the thickness of the sheet is made thinner by only about 0.2 mm, it is possible to provide aluminum for the can lid which has sufficient pressure resistance after filling of the beverage and excellent in rivet formability and can openability. Alloy plate.

Further, the amount of solid solution of Mg can be ensured (controlled) by the soaking treatment under the conditions described later. In other words, Mg is solid-dissolved only by the soaking treatment on the upstream side in the manufacturing process of the aluminum alloy sheet, and if the amount of Mg solid solution in the ingot is secured in advance, subsequent hot rolling and cold rolling are performed. In the downstream process, by controlling not to allow the already-prepared Mg solid solution amount and reducing it by precipitation, the amount of Mg dissolved in the final cold-rolled sheet can be ensured at a desired value (level) ). In other words, if Mg is solid-solved by the soaking treatment, it is not necessary to solidify Mg by intermediate annealing or the like during cold rolling, or the amount of solid solution of Mg in the final cold-rolled sheet can be ensured at a desired value. (Level), and thus the intermediate annealing can be omitted.

Moreover, even in such cold rolling which is not subjected to intermediate annealing, the sub-grain area ratio of the cold-rolled sheet can be controlled in the same manner as the cold rolling in which the intermediate annealing is performed. Therefore, in the present invention, the metallurgical technique such as the sub-grain area ratio and the solid solution amount of Mg can be selected, but the homogenization is used to make the solution solid-solution Mg, even if the intermediate annealing is not used. Cold rolling, too An aluminum alloy plate for a can lid having high material strength and sufficient rivet formability is produced.

1‧‧‧ can lid

2‧‧‧ Rivets

3‧‧‧ Scotch

4‧‧‧ Pull ring

5‧‧‧can open load measuring machine

6‧‧‧Cards

7‧‧‧Clocks

Fig. 1 is a photograph showing a substitute drawing of the structure of the aluminum alloy sheet of the present invention.

Fig. 2 is a plan view showing the aluminum alloy sheet formed into a can lid.

Figure 3 is a cross-sectional view showing the notch of the can lid used in the evaluation of the can opening property.

Fig. 4A is a perspective view showing the can open load measuring machine used in the evaluation of the can opening property.

Fig. 4B is a schematic cross-sectional view showing the vicinity of the can lid when the measurement is performed by the can end load measuring machine.

Fig. 4C is a front elevational view showing the direction of the can lid when the can lid is set to the can end load measuring machine.

Hereinafter, an embodiment of the aluminum alloy plate for a can lid of the present invention will be described.

(aluminum alloy composition)

The aluminum alloy plate for the can lid is as described above, and the characteristics required for the can lid in the state after the baking and coating treatment must be consistent with: The formability of the lid processing, the pressure resistance of the internal pressure after the filling of the beverage, and the can opening property which can be opened in a normal and simple manner.

Therefore, the alloy composition of the aluminum alloy sheet for a can lid of the present invention contains Mg: 4.0 to 6.0% by mass, Fe: 0.10 to 0.50 in order to conform to such required characteristics from the viewpoint of the alloy composition. %, Si: 0.05 to 0.40% by mass, Mn: 0.01 to 0.50% by mass, Cu: 0.01 to 0.30% by mass, and the balance is composed of Al and unavoidable impurities. The meaning of each element contained in the following will be described in order below.

Mg: 4.0 to 6.0% by mass

Mg is an effect of increasing the strength of the aluminum alloy sheet. When the Mg content is less than 4.0% by mass, the strength of the aluminum alloy sheet is insufficient, and the pressure resistance at the time of forming the can lid is insufficient. On the other hand, when the Mg content exceeds 6.0% by mass, the strength of the aluminum alloy sheet is too high, and the formability, particularly the rivet formability, is deteriorated. Therefore, the Mg content is set to Mg: 4.0 to 6.0% by mass.

Solid solution amount of Mg (solid solution concentration)

In addition, if Mg is dissolved in the matrix phase, a large lattice deformation will occur, so that work hardenability can be improved. On the other hand, if the amount of Mg dissolved is reduced, the undissolved Mg will be present in the form of a compound of Mg ₂ Si or Mg ₂ Al ₃ , and this compound will cause cracks or formation of constrictions when the rivet is formed. This causes the rivet formability to deteriorate.

Therefore, in the present invention, the amount of solid solution, that is, the solid solution ratio, is used as a reference (indicator) for the Mg contained in the above range, so as to maintain the original rivet formability, and Increase the strength. If the solid solution amount of Mg (solid solution ratio of Mg) is less than 80% of the Mg content of the aluminum alloy sheet, the Mg compound (Mg precipitate) will become too much, and the rivet formability will become difference. Therefore, the solid solution amount (solid solution ratio) of Mg is set to 80% or more of the aforementioned Mg content. In addition, the higher the solid solution amount (solid solution ratio) of Mg, the higher the upper limit is not particularly specified, but in the process of not performing the intermediate annealing, the Mg content is controlled to be as high as 88% or more. This practice itself is extremely difficult in the production of law. Therefore, in terms of the manufacturing limit, the upper limit of the solid solution amount (solid solution ratio) of Mg is preferably less than 88% of the Mg content.

Fe: 0.10 to 0.50% by mass

Fe forms an Al-Fe(-Mn)-based or Al-Fe(-Mn)-Si-based intermetallic compound in an aluminum alloy sheet, which improves the tearability of the scored portion when formed into a can lid. It has the effect of improving the can opening property. When the Fe content is less than 0.1% by mass, the tearing property of the score portion cannot be improved, and the occurrence of the score line breakage is likely to occur at the time of opening the can (the crack propagation reaches the portion other than the score portion when the can is opened) or The required opening capacity is increased, resulting in a broken can opening such as a broken ring. On the other hand, if the Fe content exceeds 0.50% by mass, the number density or volume ratio of the intermetallic compound formed in the aluminum alloy sheet will become large when casting or hot rolling, resulting in rivet forming. Sexual deterioration. Therefore, the Fe content is set to 0.10 to 0.50% by mass.

Si: 0.05 to 0.40% by mass

Si forms an Mg-Si-based or Al-Fe(-Mn)-Si-based intermetallic compound in an aluminum alloy sheet, which improves the tearability of the scored portion when formed into a can lid, and thus has an improved can opening. Sexual effect. When the Si content is less than 0.05% by mass, the can opening property cannot be improved similarly to Fe. Further, the purity required for the aluminum base material of the raw material used for the aluminum alloy sheet must also be increased, so that the cost is increased. On the other hand, when the Si content exceeds 0.40% by mass, when casting or hot rolling is performed, the intermetallic compound formed in the aluminum alloy sheet is increased, and the rivet formability is deteriorated. Therefore, the Si content is set to 0.05 to 0.40% by mass.

Mn: 0.01 to 0.50% by mass

The Mn system has the effect of improving the strength of the aluminum alloy sheet, and forms an Al-Fe-Mn-based or Al-Fe-Mn-Si-based intermetallic compound in the aluminum alloy sheet, thereby improving the nick of the formed can lid. The tearing property of the part has the effect of improving the can opening property. When the Mn content is less than 0.01% by mass, the effect of improving the strength of the aluminum alloy sheet and the effect of improving the can opening property when forming the can lid cannot be obtained. On the other hand, when the Mn content exceeds 0.50% by mass, when casting or hot rolling is performed, the intermetallic compound formed in the aluminum alloy sheet is increased, and the rivet formability is deteriorated. Therefore, the Mn content is set to 0.01 to 0.50% by mass.

Cu: 0.01 to 0.30% by mass

Cu is an effect of increasing the strength of the aluminum alloy sheet. Further, work hardenability can be improved by solid-solving Cu. When the Cu content is less than 0.01% by mass, the amount of solid solution in the matrix phase is small, and the balance between strength and formability is deteriorated, and the rivet formability cannot be improved. On the other hand, when the Cu content exceeds 0.30% by mass, the strength of the aluminum alloy sheet becomes too large, and the rivet formability is deteriorated. Therefore, the Cu content is set to 0.01 to 0.30% by mass.

Unavoidable impurities

The aluminum alloy of the present invention, except for the aforementioned essential components, is composed of Al and unavoidable impurities. The unavoidable impurities are: Cr is 0.3% by mass or less, Zn is 0.3% by mass or less, Ti is 0.1% by mass or less, Zr is 0.1% by mass or less, B is 0.1% by mass or less, and other elements are respectively 0.05. If it is within the range of mass% or less, it may be allowed. If the content of the unavoidable impurities is within this range, the properties of the aluminum alloy sheet of the present invention are not affected.

(Organization of aluminum alloy plate)

In the present invention, in addition to the alloy composition component described above, the structure of the aluminum alloy sheet for the can lid is limited to: a sub-crystal is added in a state after the baking and coating treatment after cold rolling. The grain area ratio maintains the original formability and is increased in strength.

In order to achieve the above, the aluminum alloy plate for the can lid after the above-mentioned baking coating treatment is placed on the plane parallel to the rolling surface, 0.05 mm from the center of the thickness of the plate toward the thickness direction (the thickness is 0.1 mm). The structure in the field of the center portion of the plate thickness (hereinafter, simply referred to as the center portion of the plate thickness) is limited to the sub-grain area ratio measured by a transmission electron microscope using a magnification of 50,000 times, on average More than 10% and less than 90% of organizations.

Thereby, the present invention can simultaneously achieve rivet formability and high strength which are difficult to achieve in the conventional art. In other words, the characteristics of the aluminum alloy plate for the can lid can be: simulate the 0.2% resistance of the aluminum alloy plate for the can lid after the heat treatment of the coating baking treatment, and the rivet formability of the aluminum alloy. Both features are of a high standard.

More specifically, as shown in the later-described embodiment, even if the 0.2% proof stress exceeds 360 MPa, the level of the protruding limit height can be set to 1.45 mm or more, and the high strength and high formability can be achieved. Here, when the protrusion limit height of the aluminum alloy plate is 1.45 mm or more, when the can lid is actually molded, the protrusion (button) having a sufficient height can be formed, and sufficient rivet formability can be obtained.

Further, such data is as shown in the later-described embodiment, that is, 0.2% of the endurance after the heat treatment of 255 ° C × 20 seconds of the baking treatment is simulated; and the micro protrusion test with a diameter of 6 mm is performed. The relationship between the strength and the formability when the rivet formability of the aluminum alloy sheet is evaluated in terms of the height of the protruding limit.

Subgrain

Hereinafter, the specification of the subgrain will be specifically described.

The subgrain is also called a sub-crystal, and is a small particle having no fixed shape. The reason for the formation of such a subgrain is that it is a material (tissue) which is imparted with a processing deformation by cold rolling or the like and is introduced into the index. The temperature, time, and stress factors that are applied are again produced in the process of returning to a lower energy structure.

In other words, in the case of the aluminum alloy plate for can lids, the indexing introduced by the cold rolling is caused by the heating of the baking coating or the like to cause the combination to be eliminated and rearranged, thereby making the index lattice The indexing density in the densely-indexed area of the wall or deformation zone is reduced, and a sharp boundary is formed, thereby generating subgrains. Although the above-mentioned intensive field and the newly moved index have a high rate of coincidence, the work hardenability will be poor, but the subgrain boundary will hinder the movement of the index, thus improving the work hardenability. . When the work hardening property is improved, the uniform deformation energy is increased, and the rivet formability of the biaxial projection deformation can be improved. In addition, the sub-grain has an effect of improving the strength in addition to the effect of improving the formability of the rivet.

This sub-grain, as shown in Fig. 1, can be seen to be formed in the crystal grains by a transmission electron microscope with a magnification of 50,000 times, and the outer edge shape of the boundary is sharp ( Clear and clear), and there is no fixed shape or isolated shape in the interior without any indexing. Thus, the ratio of the sum of the measured areas of each sub-grain to the area of the field of view of this transmission electron microscope By rate, the sub-grain area ratio specified by the present invention can be calculated.

On the other hand, it is in contact with the above-mentioned densely-distributed field or interlaced with the densely-distributed area, and the boundary thereof is a width, and it is difficult to see that the crystal grains exhibiting independent small particles are not regarded in the present invention. For subgrains, it is not included in the count. Such a crystal grain, specifically, as shown in Fig. 1, a part or a plurality of parts thereof are in contact with or interlaced with the aforementioned densely-indexed area, and have an index in the inside thereof, and the whole is the boundary (outer edge) The shape is not sharp, but the grain with a width in the realm. Such grains are difficult to see as small grains that appear to be independent or isolated one by one, and therefore are not considered to be sub-grains and are not counted. In the present invention, such a series of calculation methods are referred to as "sub-grain area ratio measured by a transmission electron microscope with a magnification of 50,000 times".

In the present invention, the average value of the sub-grain area ratio of the center portion of the thickness of the aluminum alloy sheet for the can lid is selected to be 10% or more and 90% or less.

If the average value of the sub-grain area ratio is as small as less than 10%, the aluminum alloy sheet itself tends to have high strength, and the more excellent the rivet formability and the high strength. In other words, even if the alloy composition is satisfied and the solid solution amount of the Mg described above is satisfied, it is impossible to maintain the original formability of the aluminum alloy plate for the can lid and to increase the strength.

Although the larger the sub-grain area ratio, the more the rivet formability can be improved, the upper limit of the area ratio is selected to be an average of 90% based on practical manufacturing considerations.

Therefore, in the present invention, the thickness center of the aluminum alloy plate for the can lid is used. The sub-grain area ratio of the portion is selected to be an average of 10% or more and 90% or less.

By the way, the above-mentioned Patent Document 1 and the aluminum alloy plate for can lids of the present invention are repeated in terms of the alloy composition fraction and the area ratio (area occupancy ratio) of the subgrains, but they are manufactured. The conditions are different, so the amount of Mg dissolved is low. In the above-described production conditions of Patent Document 1, when the aluminum alloy sheet is cold-rolled, a tandem rolling mill in which the rolling stands are arranged in series is used instead of a single rolling mill, and if forced cooling is not performed, The temperature is inevitably increased, and the temperature at the time of rolling is relatively high, and the precipitation of Mg is promoted, and the amount of solid solution of Mg is reduced. In other words, it is impossible to maintain the original formability of the aluminum alloy plate for the can lid and to achieve high strength. When the same strength level is compared with the present invention, the rivet formability is deteriorated.

As described above, the structure and characteristics of the aluminum alloy sheet specified by the present invention are as follows: the aluminum alloy sheet for the can lid is applied to the cold-rolled aluminum alloy sheet (the aluminum alloy sheet after cold rolling). The structure and characteristics of the aluminum alloy sheet (pre-coated aluminum alloy sheet) after painting and baking treatment, or the structure and characteristics of forming the aluminum alloy sheet into a can lid. In addition, it is also possible to carry out the heat treatment according to the specific conditions described later for the cold-rolled aluminum alloy sheet by simulating the coating baking treatment without performing such coating or coating baking treatment or without forming the can lid. The structure and characteristics of the rear aluminum alloy sheet. These structures and characteristics are the same or the same structure and characteristics as long as they are only slightly different as long as they are the same as those of the aforementioned baking treatment and the aforementioned heat treatment.

(Production method)

Next, a method of producing the aluminum alloy sheet for a can lid according to the present invention will be described.

The manufacturing process of the aluminum alloy sheet of the present invention is itself a casting process in which an aluminum alloy having the above composition is melted and cast into an ingot, in the same manner as a usual production method; and the ingot is homogenized by heat treatment. The soaking step is performed; the homogenized ingot is hot-rolled to form a hot-rolled sheet, and the hot-rolled sheet is cold-rolled in a cold-rolled step without annealing.

However, in the present invention, the metallurgical technical means of the "sub-grain area ratio" and the "solid solution amount of Mg" are selected, so even if only the soaking treatment is used to make the Mg solid solution, and does not do In the cold rolling of the intermediate annealing, an aluminum alloy plate for a can lid having both high material strength and sufficient rivet formability can be produced.

The amount of solid solution of Mg can be ensured by soaking treatment, but Mg can be solid-solved by the soaking treatment on the upstream side, as long as the amount of Mg solid solution of the ingot is first secured, and the heat on the subsequent downstream side is secured. In the steps of rolling, cold rolling, etc., the Mg solid solution amount of the final cold-rolled sheet can be ensured at a desired value (level) as long as the amount of the Mg solid solution to be secured is not reduced by precipitation. In other words, if the Mg is solid-solved only by the soaking treatment, the Mg solid solution amount of the final cold-rolled sheet can be ensured at a desired value even if it is not necessary to carry out intermediate annealing or the like in the middle of cold rolling to dissolve the Mg. (Level), the intermediate annealing can be omitted. And even if it is cold rolling without intermediate annealing, it is still cold rolling with intermediate annealing. Similarly, the sub-grain area ratio of the cold-rolled sheet can be controlled.

In order to achieve a preferred method for producing an aluminum alloy sheet for this purpose, first, an aluminum alloy ingot having the above composition is subjected to a temperature range of more than 500 ° C and 550 ° C or less in order to solidify Mg. The soaking treatment is maintained for more than 1 hour. Secondly, after this soaking treatment, the set speed of all the plates is set to 25 meters/min or more, and the minimum temperature of the rough rolled plate between the plates is set at 450 ° C or more. Rolling, followed by final refining rolling in a hot zone in which the rolling end temperature is set in the range of 300 to 360 ° C, and a hot rolled sheet is produced. Then, the hot-rolled sheet is not subjected to intermediate annealing, and the coiling temperature of the coiled aluminum alloy sheet after the final cold rolling is set at 60 to 120 ° C, and the total rolling reduction rate is set at 75%. The above cold rolling is used to form a cold rolled sheet.

Hereinafter, preferred conditions and significance of each manufacturing process will be described.

First, the aluminum alloy is melted, and the aluminum alloy of the above composition is cast by a known semi-continuous casting method such as IDC casting.

Homogeneous heat treatment:

Next, the field of the formation in which the surface layer of the ingot is not uniform is removed by surface shaving, and then subjected to soaking treatment (homogenization heat treatment). Only by this soaking treatment, Mg is solid-solved, and the amount of the above-mentioned Mg solid solution prescribed by the invention is set. In addition, the internal stress is removed, and the solute elements segregated during casting are homogenized to crystallize during casting. The intermetallic compound is diffused and solidified to homogenize the tissue. Therefore, the homogenization heat treatment is carried out in a temperature range of more than 500 ° C and 550 ° C or less for 1 hour or more, and is selected in accordance with the amount of Mg solid solution required.

When the homogenization heat treatment temperature is 500 ° C or lower, or the holding time is less than 1 hour, the amount of Mg solid solution is reduced, and the amount of solid solution of Mg described in the present invention cannot be obtained. Further, the aforementioned homogenization effect is deteriorated, and mechanical properties and can openability are also deteriorated. Further, if the homogenization heat treatment temperature exceeds 550 ° C, burning occurs during hot rolling. Further, the upper limit of the holding time is 20 hours, and if it is exceeded, the amount of solid solution of Mg is not much different, and only the productivity is deteriorated.

Hot rolling:

After the homogenization heat treatment, the ingot is not cooled, or cooled to a predetermined starting temperature, followed by hot inter-rough rolling, and then final refining by heat to form a predetermined plate thickness. Aluminum alloy hot rolled sheet. At this time, in order not to reduce the amount of solid solution of Mg secured by the soaking treatment, hot rolling is performed so that precipitation of Mg can be suppressed.

Therefore, the execution time of the hot-rolling is preferably within 10 minutes. Therefore, the set speed of all the passes is set at least 25 meters/min or more, and will be from the initial board. The plate temperature between all the plates of the final plate is set at 450 ° C or higher (that is, the minimum temperature of the coarse roll plate between all the plates is set at 450 ° C or more).

Among these passes, even if the speed of the plate is not up to 25 meters per minute, the rolling time will become longer, and the Mg-Si compound will be easily precipitated, and the amount of solid solution Mg will be easily precipitated. It will be reduced.

Further, among these passes, even if the plate temperature of only one time of the plate is less than 450 ° C, the Mg-Si-based compound is easily precipitated, and the amount of solid solution Mg is reduced.

Further, if the end temperature of the hot inter-high-rolling is less than 450 ° C, the hot rolling is divided into a rough rolling and a final refining rolling, and at the end of the continuous rolling, the end temperature of the hot inter-high rolling is performed. When it is finally refined and rolled in the heat between the next process, the rolling temperature becomes low, and edge cracking easily occurs.

After this hot inter-rough rolling, next, in order to perform the final refining rolling in which the end temperature is preferably maintained at 300 to 360 ° C or more, in order to prevent the precipitation of the Mg-Si-based compound, there is no delay. The hot-finished final rolling is performed either continuously or continuously to form a hot-rolled sheet. If the end temperature of the final refining rolling of the hot room is less than 300 ° C, the rolling load becomes high and the productivity is deteriorated. On the other hand, since a large amount of processed structure does not remain but becomes a recrystallized structure, if the temperature at the end of the final refining rolling is increased, and the temperature exceeds 360 ° C, the Mg-Si-based compound is easily precipitated. The amount of solid solution Mg is reduced.

Cold rolling:

Before the cold rolling of the aforementioned hot rolled sheet, or in each of the past plates On the way between (pass), no intermediate annealing is performed, and only cold rolling is performed. This cold rolling system uses a rolling stand as a single stand (1 stand rolling mill) or a tandem rolling mill in which two or more stands are arranged in series to perform the required number of passes (number of passes) ) cold rolling.

The cold rolling ratio (total rolling reduction ratio) is set to 85% or more. When the cold rolling ratio (total rolling reduction ratio) is set to 85% or more, the index density becomes high, and the sub-grain area ratio after the baking coating treatment increases. By introducing the index, the aforementioned rib-like indexing can easily become entangled (entangled, entangled) and can form a plurality of index-intensive areas such as a forest index, a lattice wall, a shear band, and the like. Further, by the heat treatment such as baking coating which is carried out later, sub-grains can be formed from the densely-indexed region, and the sub-grain area ratio in the range defined by the present invention can be achieved.

On the other hand, if the cold rolling ratio is less than 85%, the cumulative deformation amount imparted by the rolling is insufficient, the density-intensive area is reduced (becomes insufficient), and the sub-grain area ratio after baking coating is also reduced. Even the formability including the rivet formability is deteriorated.

Further, the material temperature after the final cold rolling (after the final plate is passed or at the exit side of the final rolling stand) (the coiling temperature at which the aluminum alloy coil is to be wound) is set in the range of 60 to 120 °C. If the temperature of the material after cold rolling is too high and exceeds 120 ° C, the index density of the cold-rolled sheet is reduced, and the sub-grain area ratio after the baking coating treatment cannot be 10% or more. On the other hand, if the temperature of the material after cold rolling is too low and does not reach 60 ° C, the index density of the cold rolled sheet is too high, and it is easy to promote its recovery to the original state during the baking and coating process, and the strength is increased. Getting worse.

The aluminum alloy sheet for a can lid produced by the above-described steps is subjected to surface treatment such as chromate or zircon, and is coated with, for example, an epoxy resin, a polyvinyl chloride sol, or a poly An organic coating such as an ester is subjected to a coating baking treatment at a temperature of about 230 to 270 ° C at a maximum metal temperature (PMT; Peak Metal Temperature), and is formed into a precoated plate, and then formed into a can lid. In the present invention, the above-described heat treatment for the coating baking treatment is simulated for the evaluation of the strength and the rivet formability, and in order to make it reproducible (reproducible), the coating treatment conditions are The range is selected: a single point of 255 ° C × 20 seconds.

(How to make the can lid)

Hereinafter, an example of a conventional method of producing a can lid from an aluminum alloy sheet (cold rolled sheet) of a material will be described.

As described above, the pre-coated and baked-coated aluminum alloy sheet (pre-coated sheet) is punched into a circular plate shape (punched blank), and then punched by a press machine. After the processing, and the round-side winding process of the outer peripheral portion is performed, a compound for sealing is applied to the rounded portion to form a casing.

Then, in the conversion molding step, the following molding processing is performed. That is, a rivet forming process for forming a convex portion for attaching a tab in the center of the casing is performed by a press machine. The rivet forming process is a foam forming process in which the center portion of the can lid is swollen, and a button forming process in which the bulging portion (foaming) is reduced in diameter by one to three steps to form a sharp protrusion. Constructed.

Then, the groove of the water outlet portion is formed by pressing with a die having a V-shaped blade edge, that is, the formation of the score 3 as shown in Figs. 2 and 3 and the improvement of the panel are performed. The formation of rigid bumps or characters.

Further, in the step of attaching the tab, the separately formed tab is caulked and attached to the convex portion formed in the center of the casing to be integrated. A plan view of this integrated can lid is shown in Fig. 2.

Then, this can lid is wound up in an opening portion of an aluminum alloy can body portion which is molded by DI and can be filled with contents (beverage, food) from the opening, and then sealed.

[Examples]

Although the embodiments of the present invention have been described above, the embodiments for confirming the effects of the present invention will be specifically described below, and comparative examples which are not in accordance with the requirements of the present invention will be described. Furthermore, the invention is not limited to only such an embodiment.

(Aluminum alloy plate for test materials)

Each of the aluminum alloys having the composition components shown in No. 1 to No. 26 in Table 1 was cast by a semi-continuous casting method (DC), and each of the examples was similarly fabricated into an ingot after the surface layer was removed (aluminum). Alloy blank plate). Then, as shown in Table 1, the various conditions of the ingot during hot rolling and cold rolling were changed and produced. Formation: It is possible to distinguish between the amount of Mg solid solution and the area of sub-grain in the state after the above-described cold rolling and after baking and coating treatment.

The manufacturing conditions common to the examples are as follows. That is, each example was similarly subjected to a homogenization heat treatment at 520 ° C for 4 hours, and then hot inter-rough rolling was started at a temperature of 520 ° C, and the end temperature of the hot inter-high-roll rolling was set at 450 ° C. As described above, immediately after the hot-rolling rough rolling, the hot-finished final rolling is started, and a hot-rolled sheet having a thickness of 1.2 to 4.3 mm is produced. Then, the hot-rolled sheet is not subjected to intermediate annealing between hot rolling or each of the cold-rolled plates, and the number of rolls is two-row series cold rolling to form a plate thickness of 0.215 mm. The can lid is covered with cold rolled sheets.

At this time, in the manner shown in Table 1, by controlling the amount of the lubricating oil and the coolant, for example, the constant speed at the time of the hot inter-hot rolling, and the rough rolling between the plates. The minimum temperature, the total rolling reduction of cold rolling, the material temperature after the final cold rolling (the exit side of the final rolling mill) (winding temperature when coiled into a coil), etc., are variously changed to control Mg. Solid solution amount and sub-grain area ratio.

Then, the aluminum alloy sheets shown in No. 1 to No. 26 of Table 1 which were manufactured in this manner were subjected to the simulation coating and baking process, and similarly, the hot oil bath was used to carry out 255 ° C × The 20-second heat-treated aluminum alloy sheet was used as a test material for the measurement and evaluation of the following structures and characteristics.

(Mg solid solution amount)

The amount of Mg solid solution (solid solution ratio) of the aforementioned test material was measured in accordance with the following procedure.

In other words, the phenol is placed in a beaker for decomposition and heated, and the sample taken from each of the test plates (the center portion of the thickness of the plate) to be measured is transferred into the decomposition beaker, and the heat is used. Phenol is thermally decomposed. Next, filtration was carried out using a filter membrane having a mesh size (capture particle diameter) of 0.1 μm, and the filtrate was introduced into an inductively coupled plasma (ICP) luminescence spectroscopic analyzer, and it was turned into a mist by an atomizer. The small solid droplets were sprayed into the plasma to determine the amount of solid solution of Mg. Further, even if the filtrate contains precipitates of less than 0.1 μm, when the filtrate is atomized into the mist, it cannot be analyzed as a large droplet, but is discharged, so that it is not in the analysis value. Contains precipitates of less than 0.1 μm. Then, the ratio (%) of this Mg solid solution amount to the Mg content in this aluminum alloy sheet was calculated. The results are shown in Table 1.

(sub-grain area ratio)

The sub-grain area ratio is measured by a transmission electron microscope at a magnification of 50,000 times for the structure of the center portion of each of the plate thicknesses on the plane parallel to the rolling surface of the test material. The average value corresponding to the number of measured fields of view is calculated.

Specifically, the test material is mechanically ground, and 0.05 mm (thickness: 0.1 mm) is taken from both sides of the thickness center toward the thickness direction, and then ground to a thickness by a double jet electrolytic polishing method. A film having a thickness of 100 nm was used in the center, and this film was photographed with a transmission electron microscope (TEM) at a magnification of 50,000 times to take four observation fields. From the captured images, only the subgrains were transferred onto the transparent film, and the image analysis software (trade name: Image-Pro Plus) was used to measure the total area of the subgrains in the imaging range, according to the foregoing. The average of the four observed fields of view was used to calculate the area ratio of the sub-grains relative to the area of the field of view (the area of the shot).

As mentioned above, the subgrain here refers to a particle surrounded by a sharp boundary without a width. If it looks like a whole, its boundary (outer edge shape) is not sharp but has a width, which is difficult. It can be seen that it is a small particle that appears to be independent or isolated, and it is not considered as: subgrain, not included in the count.

(0.2% endurance)

The above-mentioned test material was prepared into a tensile test piece of Japanese Industrial Standard JIS-5, and the tensile direction of this test piece was parallel to the rolling direction of the aluminum alloy plate. Using this test piece, a tensile test was carried out in accordance with Japanese Industrial Standard JIS-Z2241 to obtain 0.2% proof stress. The proper range of 0.2% proof stress is 300 MPa or more, and even if it is this range, even a thin can lid can satisfy a sufficient pressure resistance.

(rivet forming property)

The rivet formability is a test which simulates the above-described foaming step, and the rivet formability is evaluated. That is, for the aforementioned test materials, the diameter is A 6 mm micro protrusion test was performed to find the height of the protrusion limit where no constriction and crack occurred. 0.2% of the endurance is higher, usually, the height of the protruding limit will be worse, so if the 0.2% endurance is in the range of 310-330 MPa, the protruding limit height exceeds 1.60 mm as the proper range; 0.2% endurance exceeds 330 MPa and 360 MPa. In the following range, the protruding limit height is 1.50 mm or more, which is a proper range; if 0.2% of the endurance exceeds 360 MPa, the protruding limit height is 1.45 mm or more as a proper range. As long as the protruding height of the aluminum alloy plate exceeds 1.45 mm, a button having a sufficient height can be formed at the time of actual forming.

(opening load)

The test piece was subjected to a can opening test by a full-length end mold of 204 caliber: a process of forming, converting, and installing a pull ring.

Figure 2 is a plan view of the can lid used in the can open test.

Figure 3 is a cross-sectional view of the score 3 of the can lid used in the can open test.

Fig. 4A is a schematic view showing an open-can load measuring machine for measuring the load at the time of opening the can, and is a perspective view thereof.

Fig. 4B is a schematic cross-sectional view showing the vicinity of the can lid 1 when the can end load measuring device 5 performs measurement.

Fig. 4C is a front elevational view showing the direction of the can lid 1 when the can lid 1 is set to the can end load measuring machine 5.

The can lid 1 is set to the can open load measuring machine 5, and The tab 4 is located above the score 3 (as shown in Figure 4C). The tab 4 is hooked on the tab 4 of the can lid 1 as a locking portion 7 (as shown in Fig. 4B). The card holder 6 is pulled in the horizontal direction, and a tensile load of 3 N is applied. After the card holder 6 is allowed to stand still in this state, the can lid 1 is rotated in the X direction. The load is measured using a load cell and the highest measured load is taken as the can open load. Set the proper range of the can opening load to 25N or less.

As shown in Table 1, in the invention examples of Nos. 1 to 10 which fall within the scope of the present invention, the composition of the composition falls within the scope of the present invention, and the hot-rolling coarse-rolling is carried out at a preferred constant speed, at 10 It is completed within minutes, and the lowest temperature of the rough rolled sheet between the respective plates, the end temperature of the final refining rolling, the total rolling reduction of the cold rolling, the coiling temperature, and the like are all preferably manufactured. Conditions to manufacture.

Therefore, the solid solution ratio of Mg is 80% or more, and the central portion of the thickness of the plate exhibits a sub-grain area ratio measured by a transmission electron microscope of 50,000 times magnification as shown in Fig. 1 . The average is 10% or more and 90% or less. That is, in these invention examples, the structure of the aluminum alloy plate for the can lid is a structure in which the sub-grain area ratio is increased. In addition, this first figure is an example of the invention example 1.

From the results, it can be seen that the invention examples of Nos. 1 to 10 are as shown in Table 1, and the 0.2% proof stress and the can opening load are both positive values, and the rivet formability is also excellent. In other words, both the formability and the high strength can be achieved, and both the rivet formability and the high strength can be achieved.

Specifically, it can be achieved that when the 0.2% proof force falls within the range of 310-330 MPa, the protruding limit height is more than 1.60 mm; When the 0.2% proof force falls within the range of more than 330 MPa and 360 MPa or less, the protruding limit height is 1.50 mm or more; when the 0.2% proof stress exceeds 360 MPa, the protruding limit height is a level of high strength and high formability of 1.45 mm or more.

Therefore, the aluminum alloy sheets of No. 1 to 10 have a very thin thickness, and although they are only 0.215 mm, they are very suitable as an aluminum alloy sheet for cans which are easy to open.

On the other hand, in the comparative examples of Nos. 11 to 26 in Table 1, one of the alloy composition, the solid solution ratio of Mg, and the sub-grain area ratio in the structure of the center portion of the plate thickness is not in this case. Within the range defined by the invention, therefore, as described below, a certain value among 0.2% of the endurance, the can opening load, and the rivet formability cannot be obtained.

No.11 is because the Mg content is not as low as the lower limit, and although it is produced under the preferable production conditions, the solid solution ratio of Mg is also satisfied, and the sub-grain area ratio in the structure of the center portion of the thickness is also satisfied, but 0.2. % endurance is too low.

No. 12 is because the Mg content exceeds the upper limit and is excessive. Although it is manufactured under favorable manufacturing conditions, the solid solution ratio of Mg and the sub-grain area ratio in the structure of the center portion of the sheet thickness are also met, but 0.2% of the endurance is When it exceeds the range of 360 MPa, the level of the protruding limit of the same level as the above-described invention example is not more than 1.45 mm, the formability of the rivet is inferior, and the opening load is relatively large.

No. 13, because the Fe content is not as low as the lower limit, and although it is produced under favorable manufacturing conditions, the solid solution ratio of Mg and the center portion of the sheet thickness are The sub-grain area ratio in the structure is also consistent, but the can opening load is too large and the can opening property is poor.

No. 14 is because the Fe content exceeds the upper limit and is excessively produced. Although it is produced under favorable manufacturing conditions, the solid solution ratio of Mg and the sub-grain area ratio in the structure of the center portion of the sheet thickness are also met, but 0.2% of the endurance is In the range of 310 to 330 MPa, the level of the protrusion limit which is equivalent to the above-described invention example is not more than 1.60 mm, and the rivet formability is inferior.

No. 15 is insufficient because the Si content is not at the lower limit, and although it is manufactured under a preferable manufacturing condition, the solid solution ratio of Mg and the sub-grain area ratio in the structure of the center portion of the sheet thickness are also matched, but the can-loading load is satisfied. Too big, poor openness.

No.16 is because the Si content exceeds the upper limit and is excessively produced. Although it is manufactured under favorable manufacturing conditions, the sub-grain area ratio in the structure of the center portion of the thickness is in compliance with the specification, but the solid solution ratio of Mg is too low, 0.2%. When the endurance is in the range of 310 to 330 MPa, the level of the protrusion limit which is equivalent to the above-described invention example cannot be achieved at a level exceeding 1.60 mm, and the rivet formability is inferior.

No. 17, because the Mn content is not as low as the lower limit, and although it is produced under favorable manufacturing conditions, the solid solution ratio of Mg and the sub-grain area ratio in the center portion of the plate thickness are also in agreement, but 0.2% of the endurance Too low, the canning load is too large, and the can opening is poor.

No. 18 is because the Mn content exceeds the upper limit and is excessively produced. Although it is manufactured under favorable manufacturing conditions, the solid solution ratio of Mg and the sub-grain area ratio in the structure of the center portion of the sheet thickness are also met, but 0.2% of the endurance is When the range exceeds 360 MPa, the same level as the above-described invention example cannot be achieved. The height of the exit limit is more than 1.45 mm, and the rivet formability is poor.

No. 19, because Cu is not contained, although it is manufactured under favorable manufacturing conditions, the sub-grain area ratio in the structure of the center portion of the thickness is in compliance with the regulations, but when the 0.2% proof is in the range of 310 to 330 MPa, The height of the protruding limit which is equivalent to the above-described invention example is more than 1.60 mm, and the rivet formability is inferior.

No. 20 is because the Cu content exceeds the upper limit and is excessive. Although it is manufactured under favorable manufacturing conditions, the sub-grain area ratio in the structure of the center portion of the thickness is in compliance with the regulations, but when the 0.2% proof is in the range of more than 360 MPa It is impossible to achieve the level of the protruding limit of the same level as the above-described invention example, which is more than 1.45 mm, and the rivet formability is inferior.

No. 21, although the alloy composition is within the scope of the present invention, the steady rate of the hot inter-high-roll rolling is too slow to suppress the precipitation of Mg, and the ratio of the solid solution of Mg is too small. As a result, when the 0.2% proof stress exceeds the range of 330 MPa and 360 MPa or less, the level of the protruding limit height equivalent to the above-described invention example is 1.50 mm or more, and the rivet formability is inferior.

No. 22, although the alloy composition is within the scope of the present invention, the minimum temperature of the rough rolled sheet between the respective sheets is less than 450 ° C, and the Mg-Si-based compound is easily precipitated, and it is impossible to precipitate. The precipitation of Mg is suppressed, and the ratio of the solid solution amount of Mg is too small. As a result, when the 0.2% proof stress exceeds the range of 330 MPa and 360 MPa or less, the level of the protruding limit height equivalent to the above-described invention example is 1.50 mm or more, and the rivet formability is inferior.

No. 23, although the alloy composition is within the scope of the present invention, the final temperature of the final refining rolling is too high, and the Mg-Si-based compound is easily precipitated, and it is impossible to suppress the precipitation of Mg, and the solid solution amount of Mg. The ratio is too small. As a result, when the 0.2% proof stress is in the range of 310 to 330 MPa, the level of the protrusion limit of the same level as the above-described invention example is not more than 1.60 mm, and the rivet formability is inferior.

No. 24, although the alloy composition is within the scope of the present invention, the total reduction ratio of cold rolling is too low, and the sub-grain area ratio is too small. As a result, when the 0.2% proof strength is in the range of more than 330 MPa and 360 MPa or less, the level of the protrusion limit level of the same level as the above-described invention example is 1.50 mm or more, and the rivet formability is inferior, and high rivet formability and high cannot be achieved. strength.

No. 25, although the alloy composition is within the scope of the present invention, the final coiling temperature during cold rolling is too low, and the index density of the cold-rolled sheet is too high, which is promoted in the baking coating process. Recovery results in a 0.2% strain that is too low to combine high rivet formability and high strength.

No. 26, although the alloy composition is within the scope of the present invention, the final coiling temperature at the time of cold rolling is too high, and the solid solution ratio and the sub-grain area ratio of Mg are too small to be far from the lower limit. As a result, when the 0.2% proof stress is in the range of more than 330 MPa and 360 MPa or less, the protruding height of the same degree as the above-described invention example is 1.50 mm or more, the rivet formability is not good, and high rivet formability and the rivet resistance cannot be achieved. high strength.

From the above results, it can be proved that in order to have both high The rivet formability and high strength of the various elements of the invention and the significance of the preferred manufacturing conditions.

The present invention has been described in detail with reference to the preferred embodiments thereof, and various modifications and changes can be made without departing from the spirit of the invention.

This application is based on the Japanese invention patent application filed on October 20, 2014 (Japanese Patent Application No. 2014-213737), and the Japanese invention patent application filed on August 20, 2015 (Japanese Patent Application No. 2015-162561). Priority, therefore the contents of the two applications are cited in this application.

[Industrial availability]

As described above, the present invention does not require the material strength to be sacrificed in order to obtain the rivet formability as in the conventional art, and it is possible to achieve sufficient rivet formability even with high material strength. Therefore, even when the thickness of the sheet is made thinner by only about 0.2 mm, it is possible to provide aluminum for the can lid which has sufficient pressure resistance after filling of the beverage and excellent in rivet formability and can openability. Alloy plate.

Therefore, it is most suitable as an aluminum alloy plate for a can lid, in particular, the can lid is thinned in thickness and the can lid is made high-strength, and is required to have high rivet formability under more severe use conditions. The case of a high-strength can lid.

Claims (2)

An aluminum alloy plate for a can lid, comprising: Mg: 4.0 to 6.0% by mass, Fe: 0.10 to 0.50% by mass, Si: 0.05 to 0.40% by mass, Mn: 0.01 to 0.50% by mass, Cu: 0.01 to 0.30% by mass The remaining part is composed of Al and unavoidable impurities, and is an aluminum alloy plate which has been subjected to baking treatment after cold rolling without intermediate annealing, and is characterized by: residue extraction method by using hot phenol The measured solid solution amount of Mg is 80% or more and 88% or less of the Mg content, and is located on the plane parallel to the rolling surface, 0.05 mm from the center of the thickness direction to both sides in the thickness direction (that is, In the field in the field of 0.1 mm in thickness, the sub-grain area ratio measured by a transmission electron microscope at a magnification of 50,000 times is an average of 10% or more and 90% or less. The aluminum alloy plate for a can lid according to claim 1, wherein the aluminum alloy plate for the can lid is obtained by solid-heating only the ingot to form a solid solution of Mg.