JP3153541B2 - Manufacturing method of aluminum alloy cold rolled sheet for packaging container without surface pattern - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing an aluminum alloy sheet for forming and processing used for packaging containers such as caps and cans.

(Prior art) Aluminum alloy plates used for packaging containers such as can bodies, can lids or caps include (1) high strength, (2) good drawability, and (3) ears. Quality characteristics such as low occurrence, (4) no rough skin, and (5) good corrosion resistance are required.

For this type of application, A1100, A3003, A310
5, Aluminum alloy plates such as A5052 are mainly used. Among these, A3105 is used particularly for packaging containers that require moderate strength (for example, PP caps, screw caps, etc.), and the general production method is agglomeration → This is a method comprising the steps of homogenization treatment → hot rolling → annealing → cold rolling → intermediate annealing → final cooling rolling.

(Problems to be Solved by the Invention) However, A3105 (Al-M
An n-Mg-based aluminum alloy sheet has a drawback in that a striped surface pattern is generated on the surface of the as-rolled sheet after the final cold rolling. For this reason, when this is subjected to the packaging container manufacturing process, the surface pattern is further emphasized in the coating printing process,
There is a problem that the beauty of the container product is significantly impaired.

An object of the present invention is to provide a method for producing an aluminum alloy sheet for a packaging container, which solves the above-mentioned disadvantages of the prior art and does not cause a surface pattern which significantly impairs the beauty of the container product on the surface of the rolled plate. It is intended for.

(Means for Solving the Problems) In order to achieve the above object, the present inventor has found that a striped pattern is generated on a finished plate surface after cold rolling because a coarse macrostructure is generated. In view of this, as a result of intensive research on measures to control the recrystallized grain size, the production process and conditions (homogenization treatment, hot-rolled sheet thickness, intermediate annealing during cold rolling) were adjusted along with adjustment of the aluminum alloy composition. ) Was found to be possible by regulating

That is, the method for producing an aluminum alloy cold-rolled sheet for packaging containers without a surface pattern according to the present invention is as follows: Si: 0.1 to 0.4%, F:
e: 0.2 to 0.8%, Mn: 0.2 to 1.0% and Mg: 0.3 to 1.0%, with the balance being 2 to 24 hours at 480 ° C to 600 ° C in an Al alloy ingot consisting of Al and inevitable impurities. After homogenizing,
Hot rolling to 2.0-5.0mm thickness, after hot rolling,
Perform cold rolling without annealing, and perform heat treatment by rapid heating at a heating temperature of 400 to 550 ° C, a heating rate of 150 ° C / min or more, and a holding time of 10 minutes or less during this cold rolling process. It is characterized by.

 Hereinafter, the present invention will be described in more detail.

First, the reasons for limiting the chemical components in the present invention will be described.

Among the alloy components, Si has the effect of suppressing ears generated in the rolling direction of 45 °, but this effect is small at less than 0.1%, and when it exceeds 0.4%, recrystallized grains are coarsened. Danger of rough skin. Therefore, the Si content is in the range of 0.1 to 0.4%.

Fe has the effect of refining the recrystallized grains and preventing the occurrence of roughening during drawing. However, if it is less than 0.2%, this effect is small. Not suitable for use. Therefore, the amount of Fe is 0.2,
The range is 0.8%.

Mn is an element necessary for improving strength and drawability, but if it is less than 0.2%, the strength is insufficient, and 1.0%
If it exceeds 300, a huge Al-Mn-based intermetallic compound is generated during casting, which impairs the drawability. Therefore, the amount of Mn is 0.2 to 1.0
% Range.

Mg is effective in maintaining the strength, but if it is less than 0.3%, its effect is small, and if it exceeds 1.0%, the strength is increased, and the drawability is reduced. Therefore, Mg content is 0.3 ~
The range is 1.0%.

The aluminum alloy having the above composition may contain impurities inevitably mixed in the production, but the amount of impurities may be allowed as long as the effects of the present invention are not impaired.

 Next, the manufacturing process and conditions will be described.

The aluminum alloy having the above-described components is melted and cast by a conventional method, but the obtained ingot needs to be subjected to one-stage or two-stage homogenization treatment at 480 to 600 ° C. for 2 to 24 hours.

Such a homogenization treatment is necessary to reduce the occurrence of ears in the rolling direction of 45 ° in the drawing step of the final rolled sheet, and furthermore, the recrystallization of the rolled sheet by forming precipitates of MnAl ₆ The object is to suppress grain coarsening. However, if the heating temperature is less than 480 ° C. and the heating time is less than 2 hours, this effect is not sufficient, and if it exceeds 600 ° C., the effect is not increased, and there is a risk of burning (local melting). . Further, even if the heating time exceeds 24 hours, no adverse effect is recognized, but there is no difference in effect with the case of the heating time within that, and the cost is increased economically.

In the subsequent hot rolling, the hot-rolled finished plate thickness was 2.0 m
It is preferably not less than m and not more than 5.0 mm. If the sheet thickness is smaller than this range, it becomes difficult to obtain a predetermined sheet thickness by cold rolling, and if the sheet thickness is larger, the number of cold rolling steps increases, which leads to an increase in cost.

After hot rolling, cold rolling is performed without performing intermediate annealing. However, intermediate annealing by rapid heating must be performed during cold rolling. The purpose of this rapid heating treatment is to prevent the generation of a coarse macrostructure.

This rapid heating treatment is performed under conditions that make recrystallized grains fine and uniform by high-temperature rapid heating and can prevent the occurrence of a coarse macrostructure. Specifically, the heating temperature is
Preferably, the heating rate is 400 to 550 ° C., the heating rate is 150 ° C./min or more, and the holding time is 10 minutes or less.
The shorter the holding time, the better.

If the heating temperature is lower than 400 ° C., a sufficient intermediate annealing effect cannot be obtained and recrystallized grains will not be obtained, and therefore, the strength and the ear ratio in the 45 ° rolling direction will increase. When the temperature exceeds 550 ° C., the effect is small without much difference from the case of the heating temperature lower than that.

On the other hand, if the heating rate is less than 150 ° C./min or if the holding time exceeds 10 minutes, the recrystallized grains become coarse and coarse recrystallized grains, which is not preferable.

The cooling rate is 150 ° C / m up to 150 ° C.
Preferably, the cooling rate is at least in.

By such a rapid acceleration process, the macro grain size is 200 μm or less and the micro grain size is 30 μm.
m or less can be obtained.

 Of course, the cold rolling conditions are not particularly limited.

 Next, examples of the present invention will be described.

(Example) An Al alloy containing 0.21% of Si, 0.47% of Fe, 0.53% of Mn, and 0.61% of Mg, and the balance consisting of Al and inevitable impurities is melted and cast by a conventional method, and has a thickness of 500 mm. A 970 mm wide ingot was obtained.
After subjecting this ingot to homogenization treatment at 590 ° C for 4 hours, the thickness is 2.
The sheet was hot-rolled to 2 mm, and the hot-rolled sheet was cold-rolled to a final sheet thickness of 0.24 mm by the steps and conditions shown in Table 1. In addition, in the present invention example and the comparative example, the intermediate annealing was performed during the cold rolling. In the comparative example, the rough annealing (heating rate of 40 ° C./hr) was performed after the hot rolling and before the cold rolling.

The mechanical properties of the obtained rolled sheet were examined, the directionality was evaluated by measuring the ear ratio, and the surface pattern was evaluated by microscopic observation. The results are shown in Table 1.

The ear rate (%) is measured by an Erichsen tester (33φ punch,
The measurement was performed using a blank diameter of 55φ).

As is clear from Table 1, all of the examples of the present invention have no striped surface pattern, have a small ear ratio, and have sufficient strength. On the other hand, in the comparative example in which rough annealing is performed after hot rolling and intermediate annealing at a low heating rate is performed even during cold rolling, a striped surface pattern appears, and the ear ratio is high.

To confirm this, the inventive example No. 1 and the comparative example No. 1
As a result of measuring the maximum width of macro grains and the average particle size of micro grains, as shown in Table 2, the macro grain size in Example No. 1 of the present invention was 200 μm or less, while that of Comparative Example No. In the case of No. 1, it is as coarse as 1500 μm.
As shown in the figure, the inventive example No. 1 had no surface pattern (a), but the comparative example No. 1 had a striped pattern (b). The micrograins were almost the same size as shown in Table 2 and FIG. 1 (c) (Example No. 1 of the present invention) and (d) (Comparative Example No. 1).

(Effects of the Invention) As described in detail above, according to the present invention, the production process and conditions of the aluminum alloy for packaging containers are regulated together with the adjustment of the component composition, so that the generation of a coarse macrostructure can be prevented. Thus, it is possible to prevent the occurrence of a striped surface pattern in the largest product.

[Brief description of the drawings]

1 (a) to 1 (d) are diagrams showing a metal structure on the surface of a cold rolled sheet, wherein (a) and (b) are macro photographs (× 1) showing macro grains, (c) and (d) are macro photographs. It is a micrograph (x400) which shows a micro grain, (a) and (c) are the case of this invention example, (b) and (d) are the case of a comparative example.

Claims (1)

(57) [Claims] (1) Si: 0.1 to 0.4% by weight (hereinafter the same)
%, Fe: 0.2-0.8%, Mn: 0.2-1.0% and Mg: 0.3-1.0%
After the ingot of Al alloy consisting of Al and unavoidable impurities is subjected to homogenization treatment at 480 ° C. to 600 ° C. for 2 to 24 hours, it is hot-rolled to a thickness of 2.0 to 5.0 mm, After the end of cold rolling, cold rolling is performed without annealing, and during this cold rolling process, a heating temperature of 400 to 550 ° C and a heating rate of 150 ° C / mi
A method for producing an aluminum alloy cold-rolled sheet for packaging containers having no surface pattern, wherein a heat treatment by rapid heating is performed under conditions of n or more and a holding time of 10 minutes or less.