JPH0341539B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to tab materials for beer cans, carbonated beverage cans, etc., and more specifically, a low-cost end tab material with stay-on tabs that has excellent bendability and repeated bendability, and the production thereof. It is about the method. (Prior Art) Currently, an easy open end method is used to open beverage cans such as beer cans and carbonated beverage cans, which allows the cans to be easily opened by hand without using any equipment such as a can opener. These easy open ends include a partial open end and a full open end in which the tab separates from the can body when opened, and an end with a stay-on tab and a push-on tab end in which the tab does not separate from the can body when opened. Conventionally, the latter type of end with stay-on tabs has been promoted especially in Europe and America, and the tab material for this purpose is
Al alloy with components such as AA5082 and AA5042 is used, and the ingot is homogenized and hot rolled, then high cold rolled, and then final annealed to adjust the strength. has been done. For example, as disclosed in US Pat. No. 3,502,448, there is a method of increasing the finishing cold rolling rate to 85% or more. After this step, the tab material is subjected to final annealing. (Problem to be solved by the invention) As mentioned above, the conventional stay-on tab materials being developed in Europe and the United States have lower strength than the partial open end tab materials mainly manufactured in Japan. Therefore, there is a problem of thick plate thickness and high cost. Furthermore, since this stay-on tab material has a relatively large amount of Mg added and is subjected to high cold rolling, strength adjustment by final annealing is essential. However, finish annealing is performed at a relatively high temperature (approximately 280°C), so degreasing is usually performed to prevent rolling oil from seizing.Furthermore, the range of finish annealing temperatures is narrow, and the accuracy of annealing temperatures is limited. Due to the importance of this material, high-precision annealing equipment is required, leading to higher production costs than domestic partial open-end tab materials. As described above, the material cost of conventional stay-on tab materials is higher than that of domestic partial open-end tab materials. This means that although the stay-on tab end is more advantageous in terms of can pollution,
This is one of the reasons why it is not adopted domestically. On the other hand, in recent years, with the thinning of stay-on tubs,
Relatively high strength has become one of the important properties for stay-on tab materials. However, in the conventional manufacturing method, since high cold rolling is required, the crystal grains become flat and elongated grains, and the angles of the grains are 0°, 45°, and 45° with respect to the rolling direction.
There is a problem in that anisotropy occurs in the bending properties in the 90° direction and the repeated bending properties. In particular, cracks are likely to occur when bent at 0° with respect to the rolling direction and subjected to repeated bending deformation. That is, the stay-on tab is joined to the end by riveting, and by pulling up the tab, the score portion of the end is torn and pushed down into the can, but at this time the tab is subjected to bending deformation. In particular, when pressing down on a torn part, the tab may be repeatedly moved up and down, and at this time the tab is repeatedly bent and deformed, which may cause cracks and the tab to come off. To prevent this, it is necessary to improve the repeatability of bending. In this regard, conventionally, no particular consideration has been given to repeated bendability, and only bending workability (180° close bending) has been evaluated as a housing material, a can end material, and a can tab material. The present invention was made under such circumstances, and it is possible to obtain an Al alloy plate for stay-on tabs that has particularly excellent repeated bending properties, high strength, and excellent bending workability at a relatively low cost. The purpose is to provide technology that can (Means for Solving the Problem) In order to achieve the above object, the present inventors conducted comprehensive research on chemical composition adjustment, structure, manufacturing conditions, etc. in order to improve bending workability and repeated bendability. . As a result, it was found that the desired material properties could be obtained if the composition, structure, and manufacturing conditions including Mg were controlled. In other words, when the amount of Mg is almost the same as that of conventional materials, the smaller the crystal grains, the better the bending workability and repeated bendability, and the lower the cold rolling rate, the more equiaxed the crystal grains become. It was found that the anisotropy with respect to the direction is small. To achieve this, in addition to adjusting other components other than Mg, manufacturing conditions,
In particular, it is necessary to regulate the homogenization treatment temperature and cold rolling rate, which can improve bending workability and repeated bendability.At the same time, the finish annealing temperature can be relatively low, and the temperature tolerance is also lower than that of the conventional one. It was found that the conditions could be expanded, and that normal annealing equipment could be used. That is, the Al alloy plate for stay-on tabs having excellent bending workability and repeated bending workability according to the present invention contains Mg: 3.5 to 5.5%, and optionally further contains Si≦0.30%, Fe≦0.40%, Cu≦0.20%, Mn≦
0.20%, Cr≦0.25%, Zn≦0.15%, Zr≦0.15% and Ti≦0.20%,
The remainder consists of Al and unavoidable impurities, the strength is adjusted by final annealing, and the grain width seen from the rolled plate surface is 20 μm or less. In addition, the manufacturing method includes the above-mentioned chemical components.
After homogenizing the Al alloy ingot at 450-550℃,
It is characterized by hot rolling and cold rolling, further intermediate annealing, cold rolling at a rolling reduction of 20 to 55%, and then intermediate annealing. The present invention will be explained in more detail below. (Function) First, the reason for limiting the chemical components in the present invention will be explained. Mg: Mg is an important element that imparts strength, and it is necessary to add a predetermined amount to ensure the strength that can be used as a stay-on tab material. That is, unless it is added at least 3.5%, the strength of the stay-on tab material will be low and it cannot be used. However, if it is added in an excessive amount exceeding 5.5%, the strength will be too high, leading to a decrease in moldability, which is not preferable. Therefore, the Mg amount is 3.5
The range should be ~5.5%. Fe: The addition of Fe has a great effect on grain refinement,
The larger the amount added, the finer the particles. However, if it is added in an excessive amount, although it is effective for grain refinement, it is not preferable because the number of intermetallic compounds increases, resulting in a decrease in repeated bendability. for that purpose
Regulated to 0.40% or less. Note that if the content is less than 0.05%, there will be little effect, and furthermore, a high purity Al ingot will be required, so it is desirable that the content be 0.05% or more. Si: Like Fe, the addition of Si is effective in refining grains and improving strength. However, if too much is added, a large amount of intermetallic compounds, especially Mg ₂ Si, will be generated, which will lead to a decrease in repeated bendability, which is not preferable. To this end, it should be regulated at 0.30% or less. Note that if it is less than 0.02%, the effect will be small and furthermore, high purity metal will be required, so 0.02% or more is desirable. Cu: Addition of Cu is effective in improving strength. But 0.20
If it is added in excess of more than %, the strength will be too high, resulting in a decrease in moldability and corrosion resistance. Therefore, the amount of Cu should be 0.20% or less. Mn, Cr: The addition of Mn and Cr has a great effect on improving strength and refining grains. However, if Mn exceeds 0.20%,
If Cr is added in excess of more than 0.25%, the formation of giant crystallized substances and the number of crystallized substances will increase, resulting in a decrease in bendability, which is not preferable. Therefore, the Mn content should be 0.20% or less, and the Cr content should be 0.25% or less. Zn: Addition of Zn has the effect of improving formability such as bending workability and stretchability. This is because it has the effect of reducing the crystallization of the (MnFe)Al ₆ intermetallic compound when viewed from the surface of the rolled sheet. However, it is not preferable to add too much because it causes a decrease in corrosion resistance. Therefore, the amount of Zn should be 0.35% or less. Ti, Zr: Ti and Zr are each effective elements for stabilizing the structure, but if they are added in large amounts, they will form giant compounds and reduce bending workability, so the amount of Ti should be 0.20% or less. The amount of Zr shall be 0.15% or less. In the present invention, the inclusion of Mg is essential, but the other elements mentioned above are optional addition elements, and at least one of them is added as necessary. Next, the manufacturing method of the present invention will be explained. The Al alloy having the above chemical components is melted and cast by a conventional method, and the resulting ingot is homogenized and then hot rolled. These conditions are not particularly limited. However, the homogenization process needs to be performed at a temperature of 450 to 550°C. This is because if the heating temperature is less than 450℃, homogenization will be insufficient and cause edge cracks to occur during hot rolling, and if it exceeds 550℃, burning will occur and the surface condition will deteriorate, which is not desirable. It is. Further, after cold rolling, intermediate annealing is performed. Here, the intermediate annealing conditions are not particularly limited, but complete recrystallization is essential, and from the viewpoint of crystal grains, continuous annealing (CAL) is preferably used. The CAL conditions are a heating and cooling rate of 100°C/min or more, an attained temperature of 380 to 550°C, and a holding time of 10 minutes or less. The cold rolling rate after intermediate annealing affects strength, crystal grains, bending workability, or repeated bendability, so it needs to be controlled. In other words, the strength is adjusted by finish annealing, but if the cold rolling reduction is less than 20%, although bending workability and repeated bendability are excellent, the required strength cannot be obtained, and cold rolling is necessary to improve the strength. Although it is necessary to increase the ratio, if it exceeds 55%, the strength immediately after rolling increases, the subsequent final annealing temperature becomes high, and the crystal grains become flat elongated grains, which improves bending workability and repeated bendability. This is not preferable because the anisotropy becomes large. Therefore, the cold rolling rate is 20
~55% range. After this cold rolling, it is necessary to perform final annealing to adjust the strength. In this case, the final annealing temperature is determined each time to obtain the desired strength, and although it is not particularly limited here, the desired strength can be achieved at a temperature as low as 260° C. or lower.
Therefore, the annealing cost can be reduced, the temperature tolerance can be made wider than before, and the annealing equipment can be handled using ordinary equipment. Through the above manufacturing process, a structure that contributes to improvement in bending workability and furthermore, repeated bendability can be obtained. That is, the smaller the crystal grain size, the better the bending workability and repeated bending workability, so the grain width observed from the plate surface is preferably 20 μm or less. (Example) Next, an example of the present invention will be shown. Example 1 An Al alloy having the chemical composition shown in Table 1 was melted and cast by a conventional method, and the resulting ingot was subjected to homogenization treatment by holding it at a temperature of 500°C for 3 hours, and then hot rolled to a thickness of 5 mm. And so. After that, it is cold rolled to a thickness of 0.83mm and CAL annealed (heating and cooling rate 700℃/min, final temperature 450℃,
(holding time: 2 seconds) and then cold rolling to a product thickness of 0.5 mm. Furthermore, in order to keep the strength constant, invention examples No. 1 to No.
Finish annealing was carried out at 240°C for 2 hours for Comparative Example No. 4, and at 250°C for 2 hours for Comparative Example No. 5. Baking of the obtained material (200℃ x
Table 2 shows the mechanical properties, bending workability, repeated bendability, and grain width after 20 min). Note that the baging treatment was performed under the same conditions as when the tab material was painted, assuming that it would be molded after painting. As shown in Fig. 1, the bending workability is determined by performing 180° close bending in the 0° direction (rolling direction) or in the 90° direction, and determining the degree of cracking at the bent portion. Evaluation was made as follows: excellent) → ○ → ○△ → △ (poor). The repeated bendability is 1 as shown in Figure 2.
Hold the material plate 1 with a holder 2 having an R of mm, and
The evaluation was performed by determining the number of times of breakage, with one cycle consisting of protruding to a height of mm, bending at 90°, and returning. As is clear from Table 2, invention examples No. 1 to No.
All of No. 4 have the strength as stay-on tab materials, and are excellent in bending workability and repeated bendability. On the other hand, although Comparative Example No. 5 has the same strength as the inventive example, it is inferior in bending workability and repeated bendability. In each example, the grain width is 20 μm or less.

【table】

[Table] Example 2 A hot-rolled plate (thickness: 5 mm) was produced in the same manner as in Example 1 for an Al alloy having the No. 1 chemical composition shown in Table 1, and this was cold-rolled. 0.59mm (Comparative Example A) and 1.25mm (Comparative Example B) by rolling, respectively.
The thickness of the product was reduced to
It was set to 0.5mm. It also has the No. 1 chemical composition shown in Table 1.
The Al alloy was subjected to the same homogenization treatment as in Example 1, hot rolled to a thickness of 3 mm, and then directly cold rolled to a product thickness of 0.5 mm (Comparative Example C). Furthermore, in order to keep the strength constant for Comparative Examples B to C, Comparative Example B was subjected to finish annealing at 250°C for 2 hours, and Comparative Example C was annealed at 260°C for 2 hours. Note that final annealing was not performed on Comparative Example A. Baking of the obtained material (200℃ x
The mechanical properties, bending workability, repeated bending properties and grain width after 20 min) are compared with Invention Example No. 1 in Example 1 and are shown in Table 3. Note that the evaluation method and criteria for each characteristic are the same as in Example 1. As is clear from Table 3, although Comparative Example A has excellent bending workability and repeated bendability, it does not have the strength as a stay-on tab material because final annealing is not performed, and problems such as tab pull-out occur. This is a practical problem. Although Comparative Examples B and C have the strength as stay-on tab materials, they are inferior in both bendability and repeated bendability. In particular, Comparative Example C under conventional production conditions with a high cold rolling rate of 83% has a large grain width and is the worst in bending workability and repeated bendability. On the other hand, as discussed in Example 1, inventive example No. 1 has a predetermined strength and is excellent in both bending workability and repeated bendability.

[Table] No. 1 (Note) No. 1 is the invention example No. in Example 1.
It is 1.
(Effects of the Invention) As detailed above, according to the present invention, it is possible to improve bending workability and repeated bendability in stay-on tab materials such as beer cans and carbonated beverage cans. It minimizes the occurrence of cracking during bending and repeated bending, which is a problem with existing materials, and can also cope with high strength and thinning, and is excellent in terms of stability and manufacturing cost.

[Brief explanation of the drawing]

Figures 1a and b are diagrams explaining the determination of bending workability by 180° close bending, and a is for 0° direction bending;
b shows the case of 90° bending, and FIG. 2 is a diagram illustrating the procedure for repeated 90° bending.

Claims (1)

[Claims] 1% by weight (the same applies hereinafter), containing 3.5 to 5.5% Mg, the remainder consisting of Al and inevitable impurities,
An Al alloy plate for stay-on tabs that has been strength-adjusted by final annealing and has excellent bending workability and repeated bendability, and is characterized by a crystal grain width of 20 μm or less when viewed from the rolled plate surface. 2 The Al alloy further contains Si≦0.30%, Fe≦0.40%,
Cu≦0.20%, Mn≦0.20%, Cr≦0.25%, Zn≦
The Al alloy plate according to claim 1, which contains one or more of the following: 0.35%, Zr≦0.15%, and Ti≦0.20%. 3. Having the chemical component according to claim 1 or 2.
After homogenizing the Al alloy ingot at 450-550℃,
Al for stay-on tabs with excellent bending workability and repeated bendability, characterized by hot rolling and cold rolling, further intermediate annealing, cold rolling at a rolling reduction of 20 to 55%, and then final annealing. Method for manufacturing alloy plates.