JPH0573822B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing aluminum alloy foil with excellent formability, such as aluminum alloy foil used for laminated foil as a material for food packaging containers. (Prior art and problems) Recently, as materials for food packaging containers, paper with no formability and synthetic materials with excellent formability but poor long-term shelf life of food due to moisture and air permeability have been used. Instead of resin materials, so-called Al laminate materials, in which aluminum foil is bonded to synthetic resin materials, are increasingly being used to compensate for their drawbacks. Aluminum foil for such materials is required to be as thin as possible from a cost perspective and to have excellent formability such as deep drawability and stretchability. Conventionally, pure aluminum such as 1N30 alloy, which has good rollability, has been mainly used for aluminum foil for such purposes. However, even in this case, if the foil is manufactured through the normal manufacturing process, that is, hot rolling, cold rolling, and final annealing (O material treatment), the crystal grains will become coarse and insufficient. When strength and elongation cannot be obtained and the angle is 0° with respect to the rolling direction,
It has the disadvantage that the elongation at 90° is smaller than the elongation at 45°, that is, the anisotropy is large, and only products with poor moldability can be obtained. Therefore, in order to improve formability, the present inventors investigated various manufacturing processes and found that at least 2
It has been found that performing intermediate annealing more than once is effective to some extent in increasing 0° and 90° elongation, but on the other hand, the strength decreases.
The effect of improving moldability could not be expected, and only unfavorable results were obtained from the viewpoint of manufacturing costs. Furthermore, these drawbacks of 1N30 alloy become more pronounced as the foil pressure becomes thinner.
There was no hope of thinning the foil either. (Purpose of the Invention) Therefore, the inventors conducted various experiments and research with the intention of improving elongation and strength and improving formability in a specific combination of alloy composition and manufacturing process. This was achieved as a result. (Structure of the Invention) That is, the method for producing an aluminum foil with excellent formability according to the present invention includes Fe: 0.7 to 1.8 wt%,
An aluminum alloy consisting of balance aluminum and unavoidable impurities shall be used, and after hot rolling the ingot of this aluminum alloy, intermediate annealing is performed at a temperature equal to or higher than the recrystallization temperature, and after this intermediate annealing, the rolling ratio is 50% or more. It is characterized in that it is cold-rolled at 5° C. and then subjected to final annealing at a temperature increase rate of 5° C./sec or more. (Specific explanation and effects of the composition) First of all, in the composition of the aluminum alloy used, the amount of Fe is limited to 0.7 to 1.8 wt% because below the lower limit, grain refinement, strength improvement, elongation, and especially
It is not effective in improving elongation at 0° and 90°, and on the other hand, if the upper limit is exceeded, coarse compounds increase, reducing ductility, and the melting point tends to increase in the hypereutectic region, making melting and casting work difficult. Based on becoming. Better results can be obtained if the amount of impurities other than Fe is as small as possible. On the other hand, in the manufacturing process, generally known manufacturing methods sequentially perform the essential steps of hot rolling, cold rolling, and final annealing on an aluminum alloy ingot, but in this invention, the above-mentioned steps are first performed. Performing intermediate annealing at a temperature range equal to or higher than the recrystallization temperature before or during the intermediate rolling step after hot rolling;
The cold rolling process after this intermediate annealing shall be performed at a rolling rate of 50% or more, and the final annealing shall be performed at 5°C/
The condition is that the temperature increase rate is sec or more. The intermediate annealing described above is effective in eliminating anisotropy, but at the same time it is necessary to refine the crystal grains during the intermediate annealing. Therefore, it goes without saying that the treatment should be performed at a temperature higher than the recrystallization temperature in order to achieve the above effect, but if the temperature is too high, the crystal grains tend to become larger and power consumption increases. Preferably, the treatment is carried out at a temperature range of 350°C to 500°C. If this intermediate annealing is not performed, the elongation at 0° and 90° with respect to the rolling direction will be low, and there will be a problem that a strong 45° selvage will appear after deep drawing. The above intermediate annealing is performed during the cold rolling process, that is, at 1
Although it is preferable to perform the cold rolling between the next cold rolling and the second cold rolling, the present invention provides a manufacturing process in which cold rolling is performed at least after 50% or more of rolling after the intermediate annealing. satisfies the limiting conditions.
Therefore, cold rolling after this intermediate annealing refines the crystal grains of the final foil, and if this is performed at a rolling rate lower than 50%, the effect of grain refinement will be small and the strength will not be sufficient. can't get it. Through this rolling process, the aluminum alloy base plate has a thickness of 0.2mm.
The following foils are made. The foil material that has gone through the above steps is subjected to final annealing at a temperature increase rate of 5° C./sec or more to form an O material. The reason why the heating rate is limited to the above range is to promote grain refinement, suppress the precipitation of Fe, and improve the strength of the foil.
This is to improve elongation. This effect becomes more pronounced as the temperature increase rate increases, and therefore it is preferably 20° C./sec. Note that the hot rolling is performed by a conventional conventional method, and a homogenization treatment may be performed according to a conventional method before hot rolling. Although this homogenization treatment does not have a particularly large effect on the final foil, it is effective to perform the treatment at a temperature of 500°C or higher in order to stabilize the quality. In addition, in the above process, large Al-Fe compounds impede formability, so by increasing the cooling rate during casting or adding finer elements, Al-Fe compound particles can be reduced.
It is preferable to miniaturize the cells. (Effects of the Invention) The aluminum alloy foil manufactured by the combination of the aluminum alloy with a limited composition and specific manufacturing conditions according to the present invention has extremely fine crystal grains and has higher strength and elongation than conventional products. It is high and has small variations in elongation at 0°, 90°, and 45° with respect to the rolling direction, and has even better formability such as deep drawability and stretchability. Therefore, it is possible to make the foil even thinner in practical use, contributing to cost reduction, and the improvement in formability increases the range of moldable materials such as laminated foil, making it suitable for use in food packaging containers, etc. can expand the scope of applicability. (Example) Next, an example of the present invention will be shown in comparison with a comparative example. Al-0.4~2.3wt%Fe with various compositions shown in Table 1
The alloy is produced into ingots using conventional methods, and these are heated to 520℃.
After preheating for 5 hours, hot rolling was performed to obtain a 4 mm blank sheet. For samples other than sample No. 9, after first cold rolling, intermediate annealing was performed at 400°C for 1 hour, and then the rolling ratio was varied in the range of 30 to 95%. The foil was then subjected to secondary cold rolling to obtain a foil with a thickness of 0.05 to 0.15 mm, and then final annealing was performed at a heating rate of 1.5 to 20° C./sec. On the other hand, sample No. 9 was cold-rolled at a rolling rate of 90% without the intermediate annealing, and was finished into an aluminum foil with a thickness of 0.1 mm.

【table】

[Table] The various aluminum alloy foils obtained above were subjected to tensile tests and deep drawing tests, and their mechanical properties (average tensile strength and average elongation), bulge height, selvage ratio, and average grain size were determined. The results of the investigation were as shown in Table 2 below.

[Table] Note: The tensile test was conducted using a test piece with a width of 10 mm, a gauge distance of 100 mm, and a tensile speed of 100 mm/min. The average tensile strength σ _B was calculated from σ _B =σ _B (0°)+σ _B (90°)+2σ _B (45°)/4. However, σ _B (0°), σ _B (90°), σ _B
(45°) are respectively 0°, 90°, and
Indicates the tensile strength in the 45° direction. The average elongation δ was also calculated in the same manner. The bulge height was measured by the hydraulic bulge test method using a die with a diameter of 50 mm. For the deep drawing test, punch 33mmφ (corner R1
mm), and calculated as follows: Ear rate = average height of peaks - average height of valleys / (average height of peaks + average height of valleys) 1/2 x 100 (%). As is clear from the results in Table 2 above, the aluminum alloy foil produced by the combination of the alloy composition and manufacturing process of the present invention has higher strength and elongation, and has a lower selvage rate than that of the comparative example that deviates from the above conditions. It can be seen that the grain size is suppressed to within 5%, and the crystal grains are fine and the moldability is excellent.

Claims (1)

[Claims] 1. An aluminum alloy containing 0.7 to 1.8 wt% Fe with the balance being aluminum and unavoidable impurities is used, and after hot rolling an ingot of this aluminum alloy, it is heated at a temperature higher than the recrystallization temperature. While performing intermediate annealing, and after this intermediate annealing, the rolling rate is 50.
% or more, and then final annealing at a temperature increase rate of 5°C/sec or more. 2. The method for producing an aluminum alloy foil with excellent formability according to claim 1, wherein intermediate annealing is performed between the first cold rolling and the second cold rolling.