JPS6238422B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an aluminum alloy composite material for food containers with excellent pitting resistance, and more particularly, to an aluminum alloy composite material for food containers with excellent pitting resistance that can be filled with highly chloric acid content. . Traditionally, aluminum alloys for food containers generally include 5052 alloy, 5082 alloy, 5182 alloy, and 3004 alloy.
Al--Mg alloys and Al--Mn--Mg alloy plates are used because they have relatively good corrosion resistance, excellent formability, and medium or higher strength. However, when filling a container made of these alloy plates with highly chloric acid content with a pH of 3 to 5 and a Cl ion concentration of 200 ppm or more, these aluminum alloy plates do not have sufficient corrosion resistance. In particular, if these plates are used as can ends and electrochemically noble metals such as tinplate or stainless steel are used for the can body, the aluminum alloy of the can ends will accelerate corrosion, which may lead to perforation due to pitting. be. For this reason, tinplate is often used as a can end when filling highly chlorine acidic contents, but when used as an easy open end, tinplate has poor opening performance and has not always been a satisfactory can end. The present inventor has conducted extensive research into the problems of conventional aluminum alloy plates and the drawbacks of using burki when filling with the high chlorine acid content described above. Even if it is filled, pitting progresses slowly,
We have developed an aluminum alloy composite material for food containers that is resistant to pitting and has excellent pitting resistance. The aluminum alloy composite material for food containers with excellent pitting resistance according to the present invention contains (1) one or both of Mg2.2 to 2.8wt% and Mn0.50 to 1.5wt%, with the remainder being Al. A food container with excellent pitting resistance, characterized by comprising an aluminum alloy core material consisting of aluminum alloys and unavoidable impurities, and an aluminum skin material with an Al purity of 99.5wt% or more and the remainder consisting of unavoidable impurities. The first invention is an aluminum alloy composite, and furthermore, (2) an aluminum alloy containing one or both of Mg2.2 to 2.8 wt% and Mn 0.50 to 1.5 wt%, with the balance being Al and inevitable impurities. A food container with excellent pitting resistance characterized by comprising a core material of aluminum and a skin material of aluminum with an Al purity of 99.5wt% or more, Cu of 0.05wt% or less, and the remainder consisting of unavoidable impurities. This invention consists of two inventions, with the second invention being an aluminum alloy composite material. Since the aluminum alloy composite material for food containers with excellent pitting resistance according to the present invention has such a structure, the skin material is electrochemically less noble than the core material, so there is no sacrifice of the skin material. The core material is well protected against corrosion due to the positive anode effect, and pitting corrosion does not reach the core material.Therefore, there is no fear of perforation even when filled with highly chloric acid contents, and the crud rate of the skin material is low. If it is less than 5%, the skin material will wear out quickly, and if it exceeds 15%, the strength of the clad material will decrease and it will become unsuitable as a container material, so the cladding percentage of the skin material should be between 5 and 15%. preferable. The components and component ratios of the core material and skin material of the aluminum alloy composite material for food containers with excellent pitting resistance according to the present invention will be explained. (A) Core material Mg is an element that has the effect of improving the strength of the core material. If the content is less than 2.2wt%, the strength cannot be ensured, and if the content exceeds 2.8wt%, The core material is not electrically noble enough with respect to the skin material, and the sacrificial anode effect of the skin material is reduced. Therefore, the Mg content is set to 2.2 to 2.8 wt%. Mn is an element that improves the strength of the core material, makes it electrochemically noble, and increases the sacrificial anode effect of the skin material.If the content is less than 0.50wt%, this effect cannot be obtained. Difficult and also
If the content exceeds 1.5wt%, giant crystallized substances are likely to be formed during casting, resulting in deterioration of properties. Therefore, the Mn content is set to 0.50 to 1.5 wt%. In addition, when the Mn content is 1.5 wt%, the effect of the aluminum alloy composite material for food containers with excellent pitting resistance according to the present invention is fully exhibited even if the Mg content is less than 2.2 wt%. , therefore, the Mn content is
When Mg is contained at 0.50 wt%, Mg can be contained at 2.8 wt%. Furthermore, when the Mg content is 2.8wt%, the aluminum alloy composite material for food containers with excellent pitting resistance according to the present invention has sufficient effects even if the Mn content is less than 0.50wt%. , therefore Mg is 2.2wt%
If Mn is contained, the Mn content can be up to 1.5 wt%. That is, when containing both Mg and Mn, the total content is preferably 0.50 to 3.7 wt%. In addition to these components, Cu and Cr can also be included.By containing Cu and Cr, it is possible to make the core material more electrochemically noble, and the sacrificial anode effect of the skin material can be reduced. It can be made larger to improve pitting resistance. To achieve this effect, the Cu content must be 0.2
~0.8 wt%, and the Cr content can be contained in the range of 0.05 to 0.35 wt%. And Cu content less than 0.2wt%, Cr content
If the Cu content is less than 0.05wt%, the electrochemically noble effect is small, and if the Cu content exceeds 0.8wt%, the susceptibility to intergranular corrosion increases, and the Cr content
If the content exceeds 0.35wt%, coarse intermetallic compounds will be formed, which will cause defects in the rigorous molding process for food containers. (B) Skin material By using aluminum with an Al purity of 99.5wt% or more, this skin material is not only electrochemically less base than the core material, but also contains high chlorine acid content due to the inclusion of impurities. If the Al purity is less than 99.5 wt%, the corrosion resistance of the skin material itself will decrease, and there is a risk that aluminum elution into the highly chloric acid contents will increase. Therefore, the Al purity is set to 99.5wt% or more. Further, the reason why the Cu content is set to 0.05 wt% or less is to make the skin material electrochemically less noble than the core material. Note that the core material and skin material may unavoidably contain Fe as an impurity, but the content is
A content of about 0.40wt% is acceptable because it has little effect. However, it is natural that fewer is preferable. Examples of the aluminum alloy composite material for food containers having excellent pitting resistance according to the present invention will be described. Example An aluminum alloy having the components and proportions shown in Table 1 was prepared, the aluminum alloy for the core material was a hot-rolled plate with a thickness of 24 mm, the aluminum for the skin material was a hot-rolled plate with a thickness of 3 mm, These two hot-rolled plates were superimposed and hot-rolled to a thickness of 3 mm, and then cold-rolled to a thickness of 0.3 mm to obtain a test material. (No. 1 to No. 4 and No. 9 to No. 12) For aluminum alloy plate materials, aluminum alloys with the ingredients and proportions shown in Table 1 were prepared, and hot rolled to a thickness of 3 mm by the usual method. After the plate was produced, it was finished by cold rolling to a thickness of 0.3 mm and used as a test material. (No.5-No.8)

[Table] No.1, No.2, No.3, No.9, No.10, No.11, No.12
Aluminum alloy composite material for food containers with excellent pitting resistance according to the present invention and No. 4, No. 5, No. 6, No.
The pitting resistance was evaluated against comparison material No. 7 and No. 8. That is, to evaluate the pitting resistance, as shown in FIG. 1, an electrochemically noble tin plate 2 was fixed to one end of a vinyl chloride pipe 3, a test material 1 was fixed to the other end, and, Considering the case of using a combination of tinplate and aluminum alloy as a test material, the two were connected with a conductor 4, and as a corrosive medium 5, the Cl ions were adjusted to 800 ppm with table salt as a model for a high chlorine content beverage. Then, use citric acid and sodium citric acid to adjust the pH to 3, and keep it at a temperature of 38℃ for 24 hours.
Evaluate the occurrence of pitting in each sample material after the passage of time,
The results are shown in Table 2. From this Table 2, it is clear that the pitting resistance improvement effect of the aluminum alloy composite material for food containers with excellent pitting resistance according to the present invention is extremely superior to the comparative materials. It is clear that there are.

【table】

[Table] As explained above, since the aluminum alloy composite material for food containers with excellent pitting resistance according to the present invention has the structure explained above, it has excellent pitting corrosion resistance. It has the effect of being suitable as a composite material for containers filled with highly chloric acid content.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing the corrosion test method. 1... Test material, 2... Electrochemically noble material,
3... Vinyl chloride pipe, 4... Conductive wire, 5... Corrosive medium.

Claims (1)

[Scope of Claims] 1. An aluminum alloy core material containing one or both of Mg2.2 to 2.8wt% and Mn0.50 to 1.5wt%, with the remainder being Al and inevitable impurities, and an Al purity of 99.5wt. An aluminum alloy composite material for food containers having excellent pitting resistance, characterized in that the aluminum alloy composite material is composed of an aluminum skin material with an aluminum skin material of at least 1% of the total amount and the remainder consisting of unavoidable impurities. 2 An aluminum alloy core material containing one or both of Mg2.2 to 2.8wt% and Mn0.50 to 1.5wt%, with the remainder being Al and unavoidable impurities, with an Al purity of 99.5wt% or more, Cu0. An aluminum alloy composite material for food containers having excellent pitting resistance, characterized in that it is made of an aluminum skin material with a content of 0.05 wt% or less and the remainder consisting of unavoidable impurities.