JPS63317458A - Can end material - Google Patents

Abstract

PURPOSE:To obtain a can end material generating no deep pitting, by using a composite material wherein a core material composed of an aluminum alloy containing Si, Cu, Mn and Mg is cladded with pure aluminum. CONSTITUTION:A can end composite material 7 is formed by cladding a core material 7a, which is composed of an aluminum alloy wherein 0.15-0.4% Si, 0.2-0.7% Cu, 0.5-1.4% Mn and 0.3-0.6% Mg are contained and the remainder is Al and inevitable impurities, with aluminum 7b wherein the purity of Al is 99.0% or more and the remainder is composed of inevitable impurities. This composite material 7 is extremely useful as the can end material of a can container containing content relatively high in salt concn.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an aluminum material for food containers, and more particularly to a material for containers for beverages and foods that has excellent pitting corrosion resistance against highly corrosive contents. In particular, the present invention relates to an aluminum material suitable as a can end material.

(Prior Art) Aluminum or aluminum alloys generally form a highly protective oxide film on their surfaces and exhibit corrosion resistance that is useful in practice, so they are widely used in fields such as daily necessities and building materials.

Additionally, aluminum or aluminum alloys have excellent corrosion resistance, are lightweight, and have excellent formability.
Furthermore, its corrosion products have the characteristic of being harmless, and in recent years.

It is also recognized as being useful as a material for soft drinks such as beer, carbonated drinks, and fruit juices, as well as food containers such as canned goods, and its usage tends to increase year by year.

Conventionally, all-steel so-called three-piece cans have been widely used as containers for the above-mentioned contents. This is a steel end (1) as shown in Figure 2.
), body (2), bottom (3), etc.

However, when it comes to lids (can ends), the ease with which various processes must be performed on the surface of the lid (riveting for attaching easy-open tabs, scoring, etc.), opening performance, and the cut of the opening are important. For reasons such as safety, it is desirable to use aluminum plates instead of steel plates.

For carbonated drinks such as beer, less corrosive juices, coffee, etc., A-Mg alloys such as JIS 5052 or Al-Mg alloys such as JIS 3004 are used as can end materials for steel can bodies. -Mn alloy is used, and pure aluminum alloy is generally used for the cap material which particularly requires deep drawability, and is usually put into practical use after being painted.

(Problems to be Solved by the Invention) However, although this type of aluminum alloy for beverages and food products has excellent formability and relatively good corrosion resistance, the content contains as much as several hundred ppm of Cl ions, causing corrosion. In the case of aggressive contents (e.g., tomato juice, sports drinks, soups, etc.), the protective oxide film on aluminum alloys is easily destroyed, resulting in localized dissolution and pitting corrosion, which can be fatal to containers. Its use was self-restricted because it could lead to accidents.

In addition, if aluminum or aluminum alloy is used for the can end and the body is made of a material that is more electrochemically sensitive than aluminum or aluminum alloy, such as tinplate, TFS, or steel, galvanic action may occur in addition to the corrosive action of the contents themselves. As a result, the rate of pitting corrosion that occurs in aluminum or aluminum alloy materials is increased, and restrictions on the use of aluminum or aluminum alloy materials due to the contents have become even more severe.

The objects of the present invention are to provide strength and formability required for a can end material, and to provide 1. To obtain a can end material which prevents the expansion of a corroded area and prevents deep pitting from occurring.

(Means for Solving the Problems) That is, the present invention provides: (1) S i 0.15 to 0.4% by weight (hereinafter referred to as % by weight)
is simply written as %), CuO, 2-0.7%, Mn
Contains 0.5 to 1.4%, Mg 0.3 to 0.6%,
A can end material (hereinafter referred to as the first invention) characterized in that the remainder is made of an aluminum alloy containing Al and inevitable impurities; and (2) Si 0.15 to 0.4, Cu
O, 2~0.7%, Mn0.5~1.4%, Mg
O,: 1 to 0.6% is added to the aluminum alloy core material with the remainder being An and unavoidable impurities, A! ;L purity 9
The object of the present invention is to provide a can end material (hereinafter referred to as the second invention) characterized in that it is clad with aluminum of 9.0% or more and the remainder being unavoidable impurities.

The reasons for limiting the aluminum alloy contents of the can end material of the first invention and the core material of the second invention are as follows.

The Cu content in the can end material of the first invention and the core material of the second invention is 0.2 to 0.7%. Cu has the effect of making the aluminum alloy electrochemical, and the content is 0.2
If the content is less than 0.7%, this effect will be small, and if the content exceeds 0.7%, susceptibility to intergranular corrosion will increase, which is not preferable.

The Mn content in the can end material of the first invention and the core material of the second invention is 0.5 to 1.4%. Mn is an element that electrochemically affects aluminum alloys and further improves corrosion resistance and strength.For contents subject to internal pressure such as carbonated drinks, AM-Mg alloy, AM-Mg
-Mn alloy is used as a container material, and when canned fish etc. are sterilized at high temperatures of 100℃ or higher after filling, the pressure inside the container increases, so the container material has a certain degree of strength. is required, and the Mn content is 0.5%.
If the content is less than 1.4%, the desired effect cannot be obtained, and if the content exceeds 1.4%, coarse intermetallic compounds are formed, which may cause defects in severe molding.

The Mg content in the can end material of the first invention and the core material of the second invention is 0.3 to 0.6%. Mg is also an element that increases material strength, but if the Mg content is less than 0.3%, a sufficient effect will not be obtained, and if the content exceeds 0.6%, corrosion resistance will deteriorate.

The Si content in the can end material of the first invention and the core material of the second invention is 0.15 to 0.4%. Si has the effect of increasing material strength and at the same time making the aluminum alloy electrochemical by coexisting with Mg, but if the Si content is less than 0.15%, the desired effect of improving material strength cannot be obtained. On the other hand, if the content exceeds 0.4%, the aluminum alloy becomes electrochemically base.

In addition to these components, it is possible to include elements such as Ti that refine the cast structure.

Note that Fe may be contained as an unavoidable impurity, and a content of up to about 0.3% is permissible as it does not impede the intended purpose of the can end material of the present invention. In other words, the less the element, the more desirable it is.

Next, in the second invention, Af is applied to the cladding layer □ of the can end material.
L Aluminum with a purity of 99.0% or more is used. Purity 9
The reason for cladding with 9.0% or more aluminum as a skin material is that the occurrence of pitting corrosion in can end materials that occurs from paint pinholes, scratches during can manufacturing, and paint film defects, as well as the growth rate of pitting corrosion, can be measured electrically. This is to chemically prevent and reduce it. In other words, since 99.0% or more of aluminum acts as a sacrificial anode compared to the core material, it makes it difficult for the aluminum material in the defective part of the paint film to suffer pitting corrosion that occurs when it comes into contact with the contents of the can containing chlorine ions, and at the same time prevents pitting corrosion. Even if pitting corrosion occurs, it has the effect of slowing down the growth rate of pitting corrosion.

The can end material of the present invention can be produced by conventional methods. Generally, can ends are formed by laminating the surface of the can end material obtained in this way and the surface of the cladding layer of the laminated material by thermocompression bonding with a resin, or by applying a paint such as epoxy resin or vinyl resin. is preferable, but it may be used as it is without applying a resin film. When coating with a resin film, it is preferable to apply a chemical conversion film such as chromium in advance.

In the second aspect of the present invention, the cladding ratio of the skin material to the core material is not particularly limited, but is usually in the range of 2 to 20%, preferably 5 to 15%. Further, the thickness of the resin film is preferably in the range of 4 to 2071 m, but is not limited thereto.

Further, in the second aspect of the present invention, the cladding layer is provided on one or both sides of the core material.

The aluminum can end material of the present invention can be used as a can end.
Although it can be used with any type of can body material, it is particularly suitable for use when the can body material is a steel plate. In this way, the case where a can container is made using the can end material of the second invention is shown in the enlarged view of the main part of FIG. 1, in which (7) is the can end material of the present invention, and (7a) is A core material, (7b) a cladding layer, and (7c) a resin film. Also, in (8), the opening formed on the can end is the mouth score (scorched line), and (
9) is resin (9c) on tin-free steel plate (9a)
The can body is coated with

(Example) Next, the present invention will be explained in more detail based on examples.

As an example core material, an alloy having the composition shown in Table 1 was cast, and then soaked and surfaced in a conventional manner to produce a core material. On the other hand, the skin material was manufactured by casting aluminum having a composition corresponding to JIS 1070 as shown in Table 1, soaking and face cutting using the usual method, and then heating and rolling it. The skin material was placed on one side of the core material obtained in this way, heated in a conventional manner, hot-strength rolled, followed by cold rolling, intermediate annealing, and cold rolling to 0.3 m1.
Can end material samples Nos. 1 to 3 having a thickness of 1 plate (cladding thickness of skin material 0.03×1) were prepared. In addition, can end material samples Nos. 4 to 6 were rolled in the same manner without cladding the skin material.
was created.

This aluminum can end material is annealed at low temperature and refined to H38.
It was made into a board. This board was treated with a chemical conversion coating using a phosphoric acid/chromic acid mixture, and then an epoxy resin coating was applied for approximately 50 minutes.
It was coated to a thickness of 1.0 m.

(Test method) Each sample of the can end material obtained as described above and the steel plate are bent together at their edges, and then caulked and fixed, and the can end material and the steel plate are electrically connected. Connected.

The samples thus prepared were immersed in 3% saline at 40° C. for 3 months, and the pitting depth was measured.

The results are shown in Table 1. In addition, comparative materials (No. 7 to N
Tests were also conducted on materials that were not clad as the conventional materials (No. 1, 9) and conventional materials (No. 10 to No. 12), and the results are also shown in Table 1.

(Effects of the Invention) As described above, the aluminum can end material of the present invention does not cause deep pitting against salt-containing contents when in contact with a steel plate. Furthermore, the core material of the can end material of the second invention of the present invention is close to the composition of aluminum alloy can end materials commonly used at present, and has no problem in strength and formability. When Mn is included, the potential difference between the core material and the cladding layer increases, and the depth of pitting corrosion caused by scratches and defects in the resin film can be suppressed to less than the thickness of the cladding layer.

As described above, the can end material of the present invention is extremely useful as a can end material for can containers having contents with a relatively high salt concentration.

[Brief explanation of drawings]

FIG. 1 is an enlarged vertical cross-sectional view of the main parts of a three-piece can using the can end material of the present invention, and FIG. 2 is a vertical cross-sectional view of a typical three-piece can. Maku I Scroll 2

Claims (2)

[Claims] (1) Si0.15-0.4%, Cu0.2-0.7%
, 0.5 to 1.4% of Mn, and 0.3 to 0.6% of Mg, with the remainder being Al and unavoidable impurities (the above weight %). (2) S0.15-0.4%, Cu0.2-0.7%,
The core material of an aluminum alloy containing 0.5 to 1.4% Mn, 0.3 to 0.6% Mg, and the remainder being Al and unavoidable impurities, has an Al purity of 99.0% or more and the remainder being unavoidable impurities (or more). A can end material characterized by being made by cladding aluminum with a weight of %).