JPS60221546A - Aluminum alloy for food container - Google Patents

Abstract

PURPOSE:To obtain an Al alloy with superior corrosion resistance and strength as the material of a can for canning a drink, food or the like by adding specified amounts of Zn, Mg and Mn to Al or further adding Cr. CONSTITUTION:An Al alloy contg. 0.1-0.8wt% Zn and 2.2-3.5wt% Mg and/or 0.5-1.5wt% Mn or further contg. 0.05-0.35wt% Cr is used as the material of a food container for a cooling drink such as beer, a carbonated drink or fruit juice or canned provisions. The Al alloy has superior corrosion resistance and high strength and can be used as the material of a can for canning a drink or food in the form of a thin plate.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an aluminum alloy for food containers, and more particularly, to an aluminum alloy for containers for beverages and foods that has excellent corrosion resistance against highly corrosive contents.

In general, aluminum or aluminum alloys form a highly protective oxide film on their surfaces and exhibit excellent corrosion resistance in practical use, so they are widely used in fields such as daily necessities and building materials.

In addition, aluminum and aluminum alloys have the characteristics of not only excellent corrosion resistance, but also light weight, toughness, and excellent formability, and furthermore, their corrosion products are harmless, and have recently become popular. It is also recognized as a material for soft drinks such as beer, carbonated drinks, fruit juices, and food containers such as canned goods, and its usage tends to increase year by year.

As a material for this type of beverage and food, JIS505
At-Mg alloys typified by No.2, AI-MB-Mn alloys such as J153004, or pure aluminum alloys are generally used for cap materials that require particularly deep drawability, and are usually unpainted. It is then put into practical use.

This type of aluminum alloy for beverages and foods has excellent formability and relatively good corrosion resistance, but when the content contains as much as several hundred ppHl of CI ions, it becomes corrosive.
In the case of low content, the protective oxide film of the aluminum alloy is easily destroyed and localized 71! This can lead to pitting and corrosion1), which can lead to fatal accidents as a container, so its use is naturally limited.

In addition, if aluminum or aluminum alloy is used as the lid material and the body is made of a material that is more electrically sensitive than aluminum or aluminum alloy, such as tin, 1" 〃Due to the addition of lupanic action, the speed of pitting that occurs in aluminum or aluminum alloy materials is increased 1), and the restrictions on the use of aluminum or aluminum-cum alloy materials due to the contents are even more severe. Become.

As explained above, aluminum or aluminum alloy has excellent properties, but in view of the fact that its use as a material for beverage and food containers is limited, as a result of extensive research, the present inventor has developed a material with excellent hole resistance. We have developed an aluminum alloy for food containers that has corrosion resistance.

The aluminum alloy for food containers according to the present invention includes (1)'
Content of Zn O, 1-0,8u+t%, and Mg
2.2-3.5wt%, Mn 0.5-1.5u+L%
The first invention is an aluminum alloy for food containers, which is characterized in that it contains one or two of the following, and the remainder consists of A1 and unavoidable impurities: (2) Zn001-0.8wt%, CrO,05
-0.35u+t%, and further contains Mg2.2~3.5u+t%, Mn0.5~1.5+u
This invention consists of two inventions, the second invention being an aluminum alloy characterized in that it contains one or two of t% and the remainder consists of A1 and unavoidable impurities.

The aluminum alloy for food containers according to the present invention will be explained in detail.

First, the components and component ratios of the atsubenium alloy for food containers according to the present invention will be explained.

Zn is an essential component, and by including an appropriate amount of Zn in A1, the form of corrosion that occurs in aluminum alloys becomes full-scale corrosion, and it prevents pitting, which is a fatal defect as a container material, and aluminum alloys are normally protected. Since there is a protective oxide film, the corrosion takes the form of pitting, but by adding Zn, the protective properties of the oxide film are weakened, and A7
- The number of points increases and the corrosion type changes from a pitting type to a general corrosion type, and this effect is small when the Zn content is 0.8 u+t%, and the corrosion rate itself increases when the Zn content exceeds 0.8 u+t%. increases. Therefore, the Zn content is 0.1
~0, i'ouL%.

MB and Mll are elements that improve strength without reducing corrosion resistance, and for contents subject to internal pressure such as carbonated drinks, AI-M g alloy, No\1-Here-M
n-alloy is used as a container material, and when canned fish etc. are sterilized at a high temperature of 00'C or higher, the pressure inside the container increases, so the container material has a certain degree of resistance. Strength is required. Mg 2.2+uL
If the content is less than 3.51%, the desired strength cannot be obtained, and if the content exceeds 3.51%, stress corrosion sensitivity increases, which is undesirable and disadvantageous in terms of rolling processing. Therefore, Mg
The content is 2.2 to 3.5 u+t%. Mn is an element that has an effect on drawability in addition to improving strength, and if the content is less than 0.5+++t%, the desired effect cannot be obtained, and if the content is too high, such as exceeding 1.5+ut%, it will become coarse. Intermetallic compounds are formed, which can actually cause defects in severe molding. Therefore, the Mn content is 0.5 to 1.
It is set as 5wL%.

Cr is an effective element for preventing stress corrosion without reducing corrosion resistance, and this effect is not observed when the content is less than 0.051%, and when the content exceeds 0.35+ut% The effect is saturated and it is wasteful, and like the above-mentioned Mn, if it is contained in a large amount, intermetallic compounds will be formed, which is undesirable. Therefore, the Cr content is 0.05-0.35u
+L% tossle.

In addition to these contained elements, it is also possible to contain, for example, an element that refines the casting structure of the Ti shade. Further, Fe may be unavoidably contained as an impurity, and a content of up to about 0.3+uL% is permissible because it does not impair the effects of the aluminum alloy for food containers according to the present invention.

Next, examples of the aluminum alloy for food containers according to the present invention will be described.

EXAMPLE The test materials used in Example 1 and Example 2 will be explained.

An aluminum alloy having the ingredients and proportions shown in Table 1 was melted, cast and rolled according to a conventional method.
A hot fill with a thickness of mn+ is produced and then cold rolled to
．． 3 was taken as the surface thickness.

No. 1 to No. 6 are aluminum alloys for food containers according to the present invention, and No. 1 to No. 1 (l is a comparative material).

Example 1 Sample materials N001 to N006 of aluminum alloys for food containers according to the present invention (sometimes referred to simply as the present invention material).
Comparative materials No. 7 to No. 40 were evaluated for hole resistance. That is, to evaluate the hole 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 where the tin plate and the test material (aluminum alloy) are used in combination, the two are connected by a conductive wire 4, and as the corrosive medium 5, as a model for a high chlorine-containing beverage, 800% of C1 ions are added using table salt. ppm and the pH was adjusted to 3 with citric acid and sodium citrate. Assessed the situation.

The results are shown in Table 2. As is clear from Table 2, it can be seen that the material of the present invention has an excellent effect of improving hole resistance. Furthermore, the microscope shown in FIG. 2 can be produced. That is, Fig. 2 (a) shows the occurrence of hole axes in the present invention 4t No. 4, in which almost no hole axes are observed, but in Fig. 2 (b) comparative material No. 7, hole axes or through-holes are observed. In comparison material No. 8 in Fig. 2(e), the hole axis reaches approximately 1/2 of the plate thickness, indicating that the inventive system has better hole axis resistance than the comparative material. That is clear.

Table 2 Example 2 Test materials were divided into No. 1-No. 3 and No. 8, and the corrosion weight loss in the same corrosive medium as described in Example 1 was investigated for comparison. In this case, N2 gas was blown into the corrosive medium for 30 minutes to reduce the dissolved oxygen as much as possible, and then the test shrine was sealed and kept at a temperature of 38°C for one month, and the corrosion loss was measured. The results are shown in Table 3.

Table 3: Corrosion loss of inventive materials No. 1 to No. 3 is comparative material No.
8, and the self-corrosion rate is low.

As explained above, since the aluminum alloy for food containers according to the present invention has the structure as explained above, it has excellent hole resistance, and is a material that is particularly electrically more stable than aluminum alloy. It is extremely effective when used in combination with, for example, tinplate, etc., and has great strength.
It has excellent industrial effects such as being able to reduce the thickness when used as a food container material, ie, a lid material or a body material.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing the corrosion test method, and FIG. 2 is a microscopic cross-sectional photograph showing the occurrence of hole axes. 1. Test material, 2. Electrically sensitive material, 3. PVC pipe, 4. Conductive wire, 5. Corrosive medium. Patent Applicant: Kobe Steel, Ltd. Image Spear 1 Figure 5 Sai2ni1 - , ω)' 2, Par-゛--- -□□伽← Procedural amendment (method) % formula % 1. Labeled food in the case Aluminum Alloy for Containers 3, Relationship with the Amendment Case Patent Applicant Address 1-3-18 Wakihama-cho, Chuo-ku, Kobe Name (1)
19) Kobe Steel Co., Ltd. Representative: Fuyuhiko Maki 4, Agent address: No. 5, Hoop 901, Fujiwazukayo-cho, 2-2-15 Minamisuna, Koto-ku, Tokyo, Date of amended order: June 26, 1980 (shipped) 6. Subject of amendment (1) Detailed explanation of the invention in the specification (2) Brief explanation of the drawings in the specification (3) Figure 2 (a) (1) (c) 8 , Contents of the amendment (1) "Also," from page 9, line 19 of the specification tube to page 10, line 7
Figure 2...It is clear. ” to be deleted. (2) Page 13 of the specification, lines 1 to 3 [Figure 1...
It's a photo. [FIG. 1 is a schematic cross-sectional view showing the corrosion test method. ” he corrected. (3) Delete Figure 2 (a), (b), and (c).

Claims (2)

[Claims] (1) Contains Zn0.1-0.8u+L%, and further contains MB 2.2-3.5u+t%, MnO, 5-1,
Contains 5u+t% of 1lffl or 2 species, the remainder A1
and unavoidable impurities. (2) ZnO,1-0,8u+t%, CrO,0
5-0,35u+1%, and further contains Mg 2.2-3.5urL%, λ'In O,5-1
, 5u+L%, and the remainder consists of AI and unavoidable impurities.