JP2019104965A - Aluminum alloy foil for electromagnetic cooking vessels, and aluminum foil molded container - Google Patents

Abstract

To provide an aluminum alloy foil for electromagnetic cooking vessels, and achieves both of corrosion resistance and moldability.SOLUTION: An aluminum alloy foil for electromagnetic cooking vessels has a composition containing Si: 0.2 wt.% or less, Fe: 0.1 wt.% or less, Mn: 0.7-1.6 wt.%, Mg: 1.0-2.0 wt.%, Cr: less than 0.05 wt.%, with the balance being Al and unavoidable impurities, and Cu: 0.01 wt.% or less in the unavoidable impurities, and has an average crystal grain size of more than 30 μm-100 μm, so that the aluminum alloy foil has excellent corrosion resistance and moldability.SELECTED DRAWING: None

Description

  The present invention relates to an aluminum alloy foil for use in electromagnetic cooking and an aluminum foil-formed container for use in electromagnetic cooking.

Aluminum alloy foils are widely used as containers for heated foods such as noodles and pans because they are excellent in moldability and thermal conductivity and are lightweight, and may be applied to heating using an electromagnetic cooker It is requested.
However, in general, aluminum foil has low electrical resistance, and heating efficiency is poor in electromagnetic cooking. Therefore, for example, in Patent Document 1 and Patent Documents 2 and 3, the aluminum foil contains a trace element such as Mg in order to increase the electrical resistance of the aluminum foil. The aluminum foil is a container formed to be used as a pan or the like in electromagnetic cooking. At the time of producing the container, the aluminum foil needs to be excellent in formability, and in order to enhance the formability, heat treatment at high temperature is performed after cold rolling in the process of producing the aluminum foil.

JP 2007-270351 A JP, 2009-097077, A Patent No. 5613573 gazette

  By the way, when using aluminum alloy foil as an electromagnetic cooking container, corrosion resistance which corrosion does not produce in contact with cooking fluid at the time of storage of a content or cooking is required. The corrosion resistance of the aluminum alloy foil decreases as the content of impurity elements decreases, so it is conceivable to increase the purity, but the higher the purity of the aluminum alloy foil, the larger the grain size after final annealing, and the formability decreases. There is a problem. In order to balance corrosion resistance and formability, it is necessary to improve formability after appropriately managing the amount of impurity elements, but the prior art is not sufficient in terms of achieving both corrosion resistance and formability. .

  The present invention has been made against the background described above, and an object of the present invention is to provide an aluminum alloy foil for electromagnetic cooking containers and an aluminum foil-formed container which are excellent in corrosion resistance and formability.

  That is, in the aluminum alloy foil for an electromagnetic cooking container according to the present invention, the first form is Si: 0.2 wt% or less, Fe: 0.1 wt% or less, Mn: 0.7 to 1.6 wt%, Mg: It has a composition containing 1.0 to 2.0 wt%, Cr: less than 0.05 wt%, the balance being Al and unavoidable impurities, and Cu: 0.01 wt% or less in the unavoidable impurities, an average crystal It is characterized in that the particle size is more than 30 μm to 100 μm.

  The invention of the aluminum alloy foil for an electromagnetic cooking container according to the other form is characterized in that in the present invention of the above form, Si: 0.01 wt% or more, Fe: 0.01 wt% or more, Cr: 0.01 wt% or more I assume.

  Invention of the aluminum alloy foil for electromagnetic cooking containers of another form is characterized by the foil thickness being 65-100 micrometers in this invention of the said form.

  The aluminum foil molded container of the present invention is characterized by comprising the aluminum alloy foil for an electromagnetic cooking container of the first to third inventions.

Next, the reasons for limitation of the components defined in the present invention and their actions will be described.
Si: 0.2 wt% or less Containing Si has the effect of improving formability by promoting crystal precipitation of Mn and refining crystal grains. However, when the content of Si exceeds 0.2 wt%, the corrosion resistance is lowered, so the upper limit of the Si content is 0.2 wt%. For the same reason, 0.1 wt% or less is desirable.
If the Si content is less than 0.01 wt%, the grain size after final annealing becomes coarse, and the formability is reduced. In addition, the purity is high and the cost is increased. Therefore, the Si content is preferably 0.01 wt% or more. For the same reason, the Si content is more preferably 0.03 wt% or more.

-Fe: 0.1 wt% or less Containing Fe has an effect of improving formability by promoting precipitation of Mn and refining crystal grains. However, if the Fe content exceeds 0.1 wt%, the corrosion resistance is lowered, so the upper limit of the Fe content is set to 0.1 wt%. 0.05 wt% or less is desirable for the same reason.
If the Fe content is less than 0.01 wt%, the crystal grain size after final annealing becomes coarse, and the formability is reduced. In addition, the purity is high and the cost is increased. For this reason, it is desirable that the Fe content be 0.01 wt% or more. For the same reason, the Fe content is more preferably 0.03 wt% or more.

-Cu: 0.01 wt% or less Cu has a corrosion resistance lower than 0.01 wt%, so the upper limit is made 0.01 wt%. For the same reason, 0.005 wt% or less is desirable.

-Mn: 0.7 wt% to 1.6 wt%
The inclusion of Mn has the effect of enhancing the electrical resistivity. If the Mn content is less than 0.7 wt%, sufficient electrical resistivity can not be obtained, and also. The strength is reduced. Therefore, the lower limit of the Mn content is 0.7 wt%. 0.9 wt% or more is desirable for the same reason.
On the other hand, when the Mn content exceeds 1.6 wt%, coarse intermetallic compounds are crystallized, and the formability is deteriorated. In addition, when the content is more than 1.6 wt%, it is necessary to increase the final annealing temperature to sufficiently recrystallize, and discoloration of the foil surface occurs. For these reasons, the upper limit of the Mn content is 1.6 wt%. For the same reason, 1.3 wt% or less is desirable.

-Mg: 1.0 wt% to 2.0 wt%
The inclusion of Mg has the effect of enhancing the electrical resistivity. If the Mg content is less than 1.0 wt%, sufficient electrical resistivity can not be obtained, and the strength is reduced. Therefore, the lower limit of the Mg content is 1.0 wt%. It is desirable to make it 1.5 wt% or more for the same reason.
On the other hand, when the Mg content exceeds 2.0 wt%, the strength becomes too high, and the formability deteriorates. Therefore, the upper limit of the Mg content is 2.0 wt%.

Cr: less than 0.05 wt% Cr has the effect of enhancing the electrical resistivity. However, if the Cr content is 0.05 wt% or more, it is necessary to increase the final annealing temperature to sufficiently recrystallize, and discoloration of the foil surface occurs. For this reason, the Cr content is less than 0.05 wt%.
Further, if the Cr content is less than 0.01 wt%, a sufficient electric specific resistance can not be obtained, so the content is desirably 0.01 wt% or more.

Average grain size: more than 30 μm to 100 μm
When the average grain size exceeds 100 μm, the formability is reduced. On the other hand, when the average crystal grain size is 30 μm or less, the crystal grains are too fine, the 0.2% proof stress becomes too high, and the formability is lowered.
The average grain size can be determined by arithmetically averaging the major axis and the minor axis of a certain number of crystal grains from the crystal grain structure observed by an optical microscope.

・ Foil thickness: 65 to 100 μm
The electrical resistivity can be increased by reducing the thickness of the aluminum alloy foil. Since a sufficient electric specific resistance can not be obtained at a foil thickness exceeding 100 μm, it is desirable to set the upper limit of the foil thickness to 100 μm. However, if the foil thickness is less than 65 μm, sufficient strength can not be obtained, so the lower limit of the foil thickness is preferably 65 μm.

  According to the present invention, it is possible to obtain an aluminum alloy foil container for an electromagnetic cooking container having excellent corrosion resistance and moldability.

  An aluminum alloy having the composition of the present invention is produced. In the present invention, the method of producing an aluminum alloy is not limited to a specific one. For example, a slab obtained by semi-continuous casting may be hot-rolled, or alternatively, an aluminum material obtained by continuous casting may be used. In addition, it is preferable to perform a homogenization process with respect to the obtained material. The conditions for the homogenization treatment are not particularly limited, but it is preferable to carry out the homogenization treatment at a high temperature for a long time, and for example, the homogenization treatment can be carried out at 500 ° C. to 600 ° C. for 3 hours to 30 hours . The precipitation of Mn can be promoted by homogenization treatment under appropriate conditions, but if Mn is precipitated too much, the effect of increasing the electrical specific resistance by Mn can not be obtained sufficiently, so depending on the alloy components and other manufacturing processes. Adjustment is necessary.

  The material after the homogenization treatment may be hot-rolled to a desired thickness and then cold-rolled to obtain an aluminum alloy foil of a desired thickness. The thickness of the foil is not particularly limited, but is preferably 65 to 100 μm from the viewpoint of strength and electrical resistance. In the middle of cold rolling, intermediate annealing at 300 to 400 ° C. for 2 to 10 hours may be appropriately performed once or more. Intermediate precipitation under appropriate conditions can promote precipitation of Mn, but if Mn precipitates too much, the effect of increasing the electrical specific resistance by Mn can not be obtained sufficiently, depending on the alloy components and other manufacturing processes. Adjustment is necessary.

Final annealing can be performed on the aluminum foil after cold rolling to obtain the aluminum alloy foil of the present invention. The final annealing conditions are desirably a temperature of 250 ° C. to 330 ° C., preferably 3 hours to 30 hours. If the final annealing temperature is less than 250 ° C., the foil is not sufficiently recrystallized and the formability is reduced. On the other hand, if the final annealing temperature exceeds 330 ° C., discoloration of the foil surface may occur.
Although Mn is added to increase the electrical specific resistance, the solution Mn causes recrystallization to be delayed, so the final annealing temperature is raised and the recrystallized grain size is coarsened. Therefore, it is necessary to crystallize Mn appropriately. By adding an appropriate amount of Si and Fe, crystallization of Mn can be promoted, the final annealing temperature can be increased, coarsening of recrystallized grains can be prevented, and the formability can be improved. As a result, the average grain size of the obtained aluminum foil is more than 30 μm to 100 μm.

  The resulting aluminum alloy foil does not need to be specially annealed such as raising the temperature, use a vacuum furnace, coat the coil end, etc., and has excellent surface quality with suppressed discoloration of the surface. ing.

Moreover, the aluminum alloy foil molded container of this invention can be obtained by shape | molding this aluminum alloy foil. The forming can be performed by press forming etc. The shape of the forming container is not particularly limited. For example, it has a bottom, a peripheral wall rising from the periphery of the bottom, and a flange extending outward from the opening of the peripheral wall It can be set as an aluminum alloy foil forming container for cooking.
The resulting aluminum alloy foil-formed container has high electrical resistance and high IH (induction heating) suitability, and is suitable for heating in an electromagnetic cooker. Moreover, this shaping | molding container is not restricted to electromagnetic cooking, It is also possible to use for heating cooking by direct fires, such as a gas stove.

Hereinafter, examples of the present invention will be described. An aluminum alloy ingot having a composition of Table 1 (the balance is Al and other unavoidable impurities) and a thickness of 600 mm was produced by a semi-continuous casting method.
The obtained ingot was homogenized at 520 ° C. for 20 hours, and then chamfered to remove a nonuniform layer on the surface, and hot rolled into a plate having a thickness of 4 mm.
Subsequently, cold rolling was performed to a thickness of 1.5 mm, and intermediate annealing was performed at 360 ° C. for 3 hours. Then, after setting it as the thickness of Table 1 by cold rolling, final annealing for 20 hours was performed at a temperature (described in Table 1) at which each foil is completely recrystallized, to obtain an aluminum alloy soft foil. With respect to the obtained aluminum alloy soft foil, evaluation of average crystal grain size, discoloration, moldability, IH suitability, and corrosion resistance was performed by the following method, and the evaluation results are shown in Table 1.

Average grain size The average grain size is an average of the minor axis and the major axis of each crystal grain of any 100 crystal grains from the surface structure photograph taken with an optical microscope (magnification: 100 times). The average value was determined as the average particle size.

-Color change The color tone difference of aluminum alloy foil before and behind final annealing was judged visually. If no difference in color tone was observed before and after final annealing, it was judged as "○", "Δ" if part or whole surface was slightly discolored, "x" if part or whole surface was clearly yellowed . There is no problem in practice if it is not less than the judgment Δ, but it is desirable that it is ○.

-Formability 1000 pieces of aluminum alloy foil were press-formed to prepare 1000 aluminum alloy foil formed containers (bottom diameter: 11.6 cm, peripheral wall height: 5.6 cm, flange width part: 1.4 cm). About the produced shaping | molding container, when the ratio of the container which the perforation generate | occur | produced in the container bottom part or the wall surface part is 1% or less, it was determined as moldability "(circle)", and 1%, it was determined as "x".

-IH (Induction Heating) aptitude IH aptitude was evaluated as an indicator of having sufficient electrical specific resistance as an aluminum alloy foil for an electromagnetic cooker. IH suitability evaluation is performed by putting 300 cc of water in an aluminum alloy foil forming container after press forming, and measuring the time required for the water temperature to rise from 20 ° C. to 90 ° C. by heating using an electromagnetic cooker. The If the required time is 120 seconds or less, it is judged as IH aptitude “○”, if it exceeds 120 seconds and “130” or less, “Δ”, and if it exceeds 130 seconds, it is “x”. In addition, the test was implemented at 520 m above sea level, and the electromagnetic cooker used HT-B6S (200 V, 3.0 kW) manufactured by Hitachi, Ltd.

Corrosion resistance A commercially available soy sauce (salt equivalent concentration: 160 g / L) was put in a glass container, and the aluminum alloy foil was immersed and kept at room temperature for 7 days and 14 days. Those with no through holes not generated until 14 days are "○", those without through holes did not occur until 7 days, but those with through holes after 14 days "C", those with through holes after 7 days It was judged as "x".
In the long-term corrosion resistance, the container and the cooking liquid do not come in direct contact with each other in the conventional chilled food cooker, but in the case of a frozen food cooker etc., the state where the frozen cooking liquid and the container are in contact High corrosion resistance is required.

According to the evaluation results, in Examples 1 to 9 satisfying the definition of the present invention, good results were obtained in all the characteristics of color change, pressability, IH suitability and corrosion resistance, while the definition of the present invention In Comparative Examples 1 to 8 in which the above was not satisfied, good results were not obtained in any of these characteristics.
In Example 8 in which the foil thickness was as thin as 60 μm, the corrosion resistance slightly decreased to Δ, and in Example 9 in which the foil thickness was as thick as 110 μm, IH suitability slightly decreased.

  As mentioned above, although this invention was demonstrated based on the said embodiment and Example, this invention is not limited to the content of the said description, The said embodiment and implementation unless it deviates from the range of this invention Appropriate modifications to the example are possible.

Claims (4)

  Si: 0.2 wt% or less, Fe: 0.1 wt% or less, Mn: 0.7 to 1.6 wt%, Mg: 1.0 to 2.0 wt%, Cr: less than 0.05 wt%, balance Is composed of Al and unavoidable impurities, and has a composition of 0.01 wt% or less of Cu in the above-mentioned unavoidable impurities, and has an average crystal grain size of more than 30 μm to 100 μm. .   The aluminum alloy foil for an electromagnetic cooking container according to claim 1, wherein Si: 0.01 wt% or more, Fe: 0.01 wt% or more, Cr: 0.01 wt% or more.   The foil thickness is 65-100 micrometers, The aluminum alloy foil for electromagnetic cooking containers of Claim 1 or 2 characterized by the above-mentioned.   It consists of aluminum alloy foil for electromagnetic cooking containers of any one of Claims 1-3, The aluminum foil molded container characterized by the above-mentioned.