JPS61264150A - Aluminum alloy sheet for can superior in bulge workability - Google Patents

Abstract

PURPOSE:To improve workabilities of ironing and bulging, by specifying the area occupation ratio of intermetallic compds., shape and the number thereof, in Al-Zn-Mn-Mg-Fe alloy sheet having a specified compsn. CONSTITUTION:In Al alloy sheet having compsn. composed of, by weight 0.05-1% Zn, 0.5-0.1% Mn, 0.5-2.0% Mg, 0.2-0.7% Fe and the balance Al with inevitable impurities, area occupation ratio of intermetallic compd. view from sheet surface after rolling is regulated to 1-3%. The size and number of the compd. are regulated to <=25mum and <=900 pieces per 0.25mm<2> respectively. Al alloy sheet for can having the constitution is superior in formabilities such as ironing and bulging workabilities, further superior in mechanical property, and suitable for can material requiring pressure resistant strength.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an aluminum alloy plate for packaging with excellent bulge formability, and more specifically to a can body material for beer and soft drinks. This invention relates to an aluminum alloy plate for packaging that has excellent can wall protrusion properties after ironing process.

[Prior art 1] In general, aluminum beverage can bodies are manufactured by drawing an aluminum plate material and subjecting it to ironing, painting and printing, and 7-lung processing. ) After that, the can wall is subjected to necking and flashing processing, but the can body is not particularly processed, so it has particularly excellent drawing and ironing workability30
04-HI9 material is used.

However, in recent years, there has been a phenomenon of diversification along with energy saving and resource saving, and beverage cans of various capacities and irregular shapes have been developed. Due to this diversification, conventional materials cannot adequately handle the irregularly shaped cans. That is, in the side wall bulging process (bulge process) after ironing process (DI process), conventional materials tend to crack due to their low ductility. As a countermeasure against this problem, heating at a high temperature after ironing is effective in improving the ductility to a certain extent and preventing the occurrence of cracks.

However, the heat treatment temperature in this case is 250″C or higher,
The temperature can reach over 270℃. This temperature is close to the recrystallization temperature of the aluminum material, so recrystallization occurs in some parts of the material, resulting in a large decrease in strength.

However, since aluminum cans are used as containers for beer, soft drinks, etc., a pressure of 5 kg/cm2 or more is generated inside the can, so aluminum cans need to be pressure resistant, and the strength of the can is reduced. There's a problem.

Furthermore, heat treatment at high temperatures shortens the life of the furnace and wastes energy.

Therefore, for forming applications such as irregular shapes, a material is required that has low work hardening during processing and that can obtain high ductility at a relatively low heat treatment temperature.In addition, a material that has few crack initiation points and crack propagation is required. has been done.

[Problem to be Solved by the Invention 1] As explained above, the present invention solves various problems that occur in the conventional manufacturing of cans for beer, drinking water, etc., and in particular,
High ductility cannot be obtained with heat treatment at low temperatures (below 270'C), and even when heat treated at high temperatures (above 270'C), there are problems with bulge processing (that is, fins are generated and cracks are likely to occur). As a result of research on these issues, they found that high ductility cannot be obtained with low-temperature heat treatment because fine precipitates in the material strongly fix dislocations and prevent subgrain formation. Further, at high temperatures, the subgrains immediately turn into recrystallized grains and the strength decreases, and these fine precipitates become AlMn-Fe.
The reason why constrictions occur during valve processing and tends to crack even with high-temperature heat treatment is that the cracks originate from relatively large intermetallic compounds (25 μm) that crystallize during agglomeration.
(above), and if there are many of these (due to propagation of fins and cracks, this is also caused by Al-Fe
-Knowing that it is a Mn-based material and that conventional materials that focused only on ironing workability could not cope with this problem, they developed an aluminum alloy plate for packaging with excellent bulge workability.

[Means for Solving the Problems 1] The aluminum alloy plate for packaging with excellent formability according to the present invention is characterized by: Zn 0.05-1wt%, Mn 0.5-0.8u+
t%, Mg 0.5-Z, 0IIlt%, Fe 0. Z
It is an aluminum alloy containing ~0.7u+t%, the balance consisting of Al and impurities, the area occupation rate of the intermetallic compound as seen from the rolled plate surface is 1 to 3%, the size of this intermetallic compound is 25 μm or less, and , the number of intermetallic compounds per 0.25n+m2 of plate surface is 900 or less.

The aluminum alloy plate for packaging with excellent bulge workability according to the present invention will be described in detail below.

First, the components and component ratios of the packaging aluminum alloy plate having excellent bulge workability according to the present invention will be explained.

Zn suppresses the growth and generation of intermetallic compounds, and in particular, by heat treatment at low temperatures, +λ
This effect is small in the case of 6f00 or more, and if the content exceeds 1 ust%, there is a problem in corrosion resistance. Therefore, the Zn content is 0.05~1w
It is assumed to be t%.

Mnj is an element necessary for suppressing fine precipitates and producing appropriate intermetallic compounds, and it also affects strength, and if the content is less than 0.5 wt%, the amount of fine precipitates and intermetallic compounds formed will decrease. Although this results in high ductility at low temperatures and the absence of necking during bulge forming, this is accompanied by a significant decrease in strength and a significant decrease in intermetallic compounds, resulting in a decrease in ironing workability. This is a problem as a packaging container, and if the content exceeds 1.0 wt%, fine precipitates and intermetallic compounds increase, which adversely affects valve processability. Therefore, the Mn content is 0.5~
1.0...t%.

Mg is an effective element for improving strength, and if the content is less than 0.5wL%, the strength improvement effect is small and there is a problem as a packaging container, and if the content exceeds 2.0wL%, The strength becomes too high and an oxide film MgO is formed on the surface that adversely affects formability, making it impossible to process. Therefore, the Mg content is set to 0.5 to 2.0 wt%.

Fe affects fine precipitates and intermetallic compounds, and if the content is less than 0.2 wt%, the intermetallic compounds will be significantly reduced, promoting a decrease in ironing workability.
If the content exceeds 711 t%, fine precipitates and intermetallic compounds will increase, leading to a decrease in valve workability. Therefore, the Fe content is set to 0.2-0.7 ut%.

In addition to these components, the Si and Cu contents are 0. ht% or less, the Cr content is 0.3u+t% or less, and other components are acceptable as long as they are at the level of impurities.

Next, to explain about intermetallic compounds, these intermetallic compounds are generated during agglomeration, and their distribution is
It is influenced by agglomeration conditions such as Fe, Mn) and solidification rate. In addition, intermetallic compounds are the starting point of cracking during bulge processing, but on the other hand, they are necessary as a feedstock to improve the light workability of ladders, and therefore the optimal range for the distribution of intermetallic compounds is required. There is.

First, if the area ratio of intermetallic compounds is less than 1%, ironing workability will be reduced and cause cracking of the can body.
If it exceeds this value, the crack propagation speed during bulge processing will increase and breakage will occur easily.

In addition, if there are too many intermetallic compounds, crack propagation will increase, so the size of the intermetallic compounds should be 25 μm or less,
Furthermore, the number of intermetallic compounds per 0.25 mm2 is 90
Must be 0 or less. Note that the intermetallic compound distribution was measured by image processing using a scanning electron microscope (SEM).

Furthermore, the crystal grains on the plate surface affect the bulge workability in the can wall, and the finer the grains, the better. It is desirable that the subsequent average crystal grains be 45 μm or less. Note that the product is cold-rolled and the grains are elongated, so the average width of the grains in the product sheet is 4.
It is desirable that the thickness is 5 μm or less.

There are no particular restrictions on the method for manufacturing the aluminum alloy sheet for packaging with excellent formability according to the present invention, but in order to suppress fine precipitates, the homogenization heat treatment is preferably performed at a temperature of 500°C or higher for 2 hours or more. In addition, the hot rolling conditions are the final plate thickness (Hot
Co11) It is preferable to set the temperature to 1.8 degrees or more and about 300°C, and furthermore, the intermediate annealing is performed under the conditions of hot rolling and, if necessary, recrystallization after cold rolling, for example, 350°C x 2
In the case of CAL, it is preferable to carry out the rolling process under conditions such that the final temperature is about s o o 'c. Furthermore, the product needs to be finished cold rolled by at least 30% or more in terms of compressive strength.

[Example 1] An example of an aluminum alloy plate for packaging with excellent bulge workability according to the present invention will be described.

Example: A small ingot with a thickness of 50m+e was made of an aluminum alloy having the ingredients and proportions shown in Table 1, and was heated at 570°C x 6
After soaking for hours, hot rolling and cold rolling are carried out.
Intermediate annealing was performed at 360° C. for 3 hours at 1 and 2 non thickness to give a product plate thickness of 0.4 mmN.

Table 2 shows the crystallized material distribution, drawing and ironing properties of these test materials, as well as their side wall extrusion properties (Er value) and pressure resistance.

As is clear from Table 2, packaging aluminum alloy plates No. 5 and No. 6, which have excellent balloon processability according to the present invention, have excellent can side wall protrusion properties under relatively low baking conditions. This is due to a decrease in fine precipitates due to the specified Mn%Fe content and a decrease in intermetallic compounds due to Zn content. In contrast, comparative material No.

Comparative materials No. 1, No. 2, and No. 2 have poor can side wall extension properties after baking, and comparative materials No. 3 have excellent can side wall extension properties (valving properties), but have problems with pressure resistance. However, during the ironing process, seizure (flaws on the can surface) occurs, which poses a problem for mass production.

[Effect of the invention 1 As explained above, the aluminum alloy plate for packaging with excellent formability according to the present invention has the above-mentioned structure.
It has excellent ironing workability and bulge workability, excellent mechanical properties, and is extremely suitable as a can material that requires high pressure resistance. Furthermore, it is effective in extending the life of the furnace and saving energy. It has this effect.

Claims (1)

[Claims] Zn0.05-1wt%, Mn0.5-1.0wt%,
Mg0.5-2.0wt%, Fe0.2-0.7wt%
It is an aluminum alloy containing aluminum with the remainder being Al and impurities, and the area occupation rate of the intermetallic compound as seen from the surface of the rolled plate is 1 to 3%, and the size of this intermetallic compound is 25 μm.
An aluminum alloy plate for packaging with excellent bulge workability, characterized in that the number of intermetallic compounds per 0.25 mm^2 of the plate surface is 900 or less.