JP2525017B2 - Aluminum alloy material for can ends - Google Patents

Description

The present invention relates to an aluminum alloy material for can ends,
More specifically, it relates to an aluminum alloy material for can ends which has excellent rivet formability and is suitable for thinning.

(Prior Art) Easy-open cans widely used as beverage cans consist of a can body (can body) and a can end (can lid), and the can body is processed into a cup shape by DI molding.
The can end is scored and rivet-molded (multi-stage overhang molding), and after the tab is attached, the can end is wound and joined to the gan body. JIS 3004 alloy material or tin-free steel with excellent deep drawability and ironing workability (DI formability) is used as the can body material, and coffee and rivet formability is excellent as the can end material for the can end material. JIS 5052 alloy material, JIS 5082 alloy material with higher strength for carbonated drinks and beer that generate internal pressure, JIS 5182
An alloy material with a plate thickness of about 0.3 mm is used.

By the way, in recent years, the demand for aluminum cans has been rapidly increasing, and it has been strongly desired to reduce the thickness and weight of cans in order to reduce the manufacturing cost.

(Problems to be Solved by the Invention) However, when the conventional alloy material is thinned,
There was a drawback that the rivet moldability became insufficient and rivet mold cracks tended to occur. That is, the rivet forming is usually carried out by forming the rivet with a diameter of about 3 mm by three-step bulging, and then attaching the tab (rivet setting), but this bulging becomes more difficult as the plate thickness becomes thinner. Therefore, in the above-mentioned conventional material, the limit was thinning to about 0.25 mm.

Therefore, the present invention has excellent rivet formability and a thickness of 0.
It is an object of the present invention to provide an aluminum alloy material for can ends which can be thinned to about 20 mm.

(Means for Solving the Problems) As a result of intensive studies conducted by the present inventor to solve the above problems, the above object can be achieved by an aluminum alloy containing a predetermined amount of Mg and a rare earth element. It has also been found that a more preferable alloy material can be obtained by further adding a metal element that improves mechanical strength to this aluminum alloy. The present invention has been accomplished based on this finding.

That is, according to the present invention, (1) Mg2 to 6% (hereinafter, weight% is simply referred to as%) (however, 2% is excluded), rare earth element 0.1.
An aluminum alloy material for can ends, characterized by containing 005 to 1% and the balance being Al and unavoidable impurities,
(2) Mg2-6% (excluding 2%), rare earth element 0.0
Aluminum alloy material for can ends, characterized by containing 05 to 1%, further containing 0.05 to 1% Cu, and the balance being Al and inevitable impurities, (3) Mg2 to 6% (however,
Aluminum alloy material for can ends, characterized in that it contains 0.005 to 1% of rare earth elements, further contains 0.05 to 1.5% of Zn, and the balance is Al and inevitable impurities (4). For can ends characterized by containing Mg2 to 6% (excluding 2%), rare earth element 0.005 to 1%, Mn 0.05 to 0.5%, and the balance Al and unavoidable impurities. Aluminum alloy material, and (5) Mg2〜
6% (excluding 2%), 0.005 to 1% rare earth element, and further contains one or more of Cr0.05 to 0.3% or Zr0.05 to 0.3%, the balance Al and unavoidable impurities An aluminum alloy material for can ends, comprising:

The reasons for limiting the components contained in the can end aluminum alloy material and the component contents in the present invention are as follows.

The content of Mg is 2 to 6%. Mg is an important element that gives strength to an aluminum alloy material. 2% Mg content
If the content is less than the above range, the strength is not sufficiently improved, and if the content of Mg exceeds 6%, the rolling property is deteriorated and the formability is deteriorated.

The content of rare earth elements is 0.005 to 1%. Although the kind of the rare earth element is not particularly limited, specifically, for example, Y, La, Ce, Pr, Nd, Sm and a mixture thereof can be preferably used. The rare earth element has the function of improving the rivet formability. That is, even if only a very small amount of rare earth element is added, the amount of work hardening in the rivet portion during overhang forming is reduced and the plate thickness distribution is made uniform, so work mounting and tab attachment due to local plate thickness reduction (necking) Prevents the occurrence of cracks. If the total content of rare earth elements is less than 0.005%, its effect is small, and if it exceeds 1%, a coarse intermetallic compound is formed and rivet formability is deteriorated. The preferable content range of the rare earth element is 0.05 when considering the cost.
It is about 0.5%.

Although the rivet formability is greatly improved by containing the above Mg and rare earth elements, it is effective to add the following elements further in order to further improve the mechanical strength and the like.

The Cu content is 0.05 to 1%. Cu is an element that imparts strength. If the Cu content is less than 0.05%, its effect is small, and if it exceeds 1%, the formability and corrosion resistance deteriorate. The Zn content is 0.05 to 1.5%. Zn is one of the elements added to impart strength, and is also an element that improves the rivet formability. If the Zn content is less than 0.05%, the effect is insufficient, and if it exceeds 1.5%, the rivet formability deteriorates.

The Mn content is 0.05 to 0.5%. Mn imparts strength and contributes to stabilizing the texture (ear). Mn content is 0.
If it is less than 05%, the effect is insufficient, and if it exceeds 0.5%, the formability deteriorates.

The contents of Cr and Zr are both 0.05 to 0.3%. Cr and Zr make the crystal grains finer and improve the formability. Cr and
If the content of Zr is less than 0.05%, the effect is insufficient, and if it exceeds 0.3%, the formability deteriorates.

In the aluminum alloy material of the present invention, Fe and Si as impurities contained in addition to the above composition are each 0.5
If it is less than 0.1%, there is no particular problem, but it is preferably less than 0.2% in order to improve the rivet moldability. Further, Ti and B, which are usually added as a refiner of the ingot structure, are each 0.
It is preferably added within the range of less than 05% and less than 0.01%.

Next, a method for manufacturing the aluminum alloy material for can ends of the present invention will be described.

First, a molten aluminum alloy containing the components described above is cast by a conventional method. As this casting method, a semi-continuous casting method is generally used, but thin plate continuous casting may be performed in order to save energy and improve mechanical properties. The obtained ingot is subjected to soaking (homogenization treatment). It is preferable that the soaking conditions are such that the soaking temperature is 450 to 600 ° C. and the soaking holding time is within 48 hours in order to make the crystal grains fine during the intermediate annealing. If the soaking temperature is lower than 450 ° C., it is difficult to refine the crystal grains in the intermediate annealing, and it becomes difficult to perform electrochemical graining uniformly and finely. The soaking temperature is 600 ℃
In the condition that the temperature exceeds 50 hours or the soaking time exceeds 48 hours,
These effects are saturated. It only increases energy costs.

Although hot rolling is performed after soaking, it is not necessary to strictly control this hot rolling.
Hot rolling may be performed by heating at ~ 550 ° C.

After the hot rolling is completed, it is usual to perform the primary cold rolling, then the intermediate annealing, and then the final cold rolling. However, in some cases, the intermediate annealing is sandwiched twice or more to perform the cold rolling. You may go.

The annealing temperature in this intermediate annealing is suitably 300 to 600 ° C. If the temperature is lower than 300 ° C, recrystallization does not occur completely, and if the temperature exceeds 600 ° C, the surface is heavily oxidized and the surface is discolored, which is not preferable. In addition, this intermediate annealing may be either normal batch annealing (average heating rate 20 to 50 ° C / hr) or continuous annealing (average heating rate several ° C to several tens ° C / sec), but further improves the strength after baking, Moreover, in order to make the average recrystallized grain size before the final cold rolling fine and uniform, it is preferable to apply continuous annealing rather than batch annealing. In the case of continuous annealing, it is more desirable to set the intermediate annealing temperature to 480 ° C or higher in order to promote solid solution of Cu and the like.

The subsequent final cold rolling is performed after the intermediate annealing in order to obtain the strength required for the thin can end material, and the rolling rate may be in the range of 30 to 90%. Further, after the final cold rolling is finished, temper annealing (200 to 300 ° C., 1 to 10 hours, H2n treatment) for obtaining desired strength and ductility, and stabilizing annealing (in order to prevent changes in strength over time ( 100 ℃ ~ 200 ℃, 1 ~ 10
Time, H3n) may be given.

The aluminum alloy material of the present invention thus obtained is subjected to a treatment such as degreasing, and then coated and baked (baked) at a temperature of about 200 ° C. for several minutes, and then molded and processed as a can end.

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

Examples Aluminum alloys having the compositions shown in Table 1 (No. 1 to
No. 15) was melted and made into a 500 mm thick ingot by a semi-continuous casting method. This was face-shaved, soaked at 500 ° C. for 5 hours, and then hot-rolled to a thickness of 3 mm. Then, after cold rolling, 520 ℃ in a continuous annealing furnace, subjected to intermediate annealing for 10 seconds, then by final cold rolling, 0.30, 0.28, 0.2 respectively.
Plates with 6 kinds of thickness of 6, 0.24, 0.22 and 0.20 mm were finished.
At this time, the position where the intermediate annealing was performed under the above-mentioned conditions was set so that the final cold rolling rate would be 60% in all cases. After degreasing each of the obtained final cold-rolled sheets, baking was performed at 200 ° C. for 20 minutes, and then the can ends having an outer diameter of 60 mm were formed, and the rivet formability was evaluated. In the rivet forming, a rivet having an outer diameter of 3 mm was formed by a three-step overhanging process, tabs were joined, and the presence or absence of rivet cracking was observed. The evaluation of the rivet crack occurrence status in this test is
Out of 1,000 cans molded, no cracks were found at all (good rivet formability), 1-5 cans were cracked at △ (somewhat good), and 6 or more cans were cracked. Is indicated by x (bad). The results are shown in Table 2.

As is clear from the results of Table 2, the aluminum alloy materials for can ends (No. 1 to No. 7) of the present invention are all
Even if the wall thickness is reduced to 0.20 mm, rivet cracking does not occur and rivet formability is extremely good. On the other hand, in the comparative example, the rivet formability is poor, and it is difficult to reduce the thickness to 0.24 to 0.26 mm or less.

(Effect of the Invention) As described above, according to the present invention, an aluminum alloy material for can ends having excellent rivet formability is provided. Therefore, according to the present invention, the thickness of the can end material can be further reduced (the plate thickness is 0.20 mm), and the weight reduction of the aluminum can and the cost reduction can be achieved remarkably.

Claims (5)

(57) [Claims] 1. Aluminum for can ends, characterized in that it contains Mg 2 to 6% (excluding 2%), rare earth elements 0.005 to 1%, and the balance is Al and inevitable impurities (above weight%). Alloy material. 2. Mg 2 to 6% (excluding 2%), rare earth element 0.005 to 1%, Cu 0.05 to 1%, balance Al and unavoidable impurities (above weight%) An aluminum alloy material for can ends, which is made of 3. Mg2 to 6% (excluding 2%), rare earth element 0.005 to 1%, Zn0.05 to 1.5%, balance Al and unavoidable impurities (above weight%) An aluminum alloy material for can ends, which is made of 4. Mg 2 to 6% (excluding 2%), rare earth element 0.005 to 1%, Mn 0.05 to 0.5%, and balance Al and unavoidable impurities (above wt%). An aluminum alloy material for can ends, which is made of 5. Mg2-6% (excluding 2%), rare earth element 0.005-1%, Cr0.05-0.3% or Zr
An aluminum alloy material for can ends, characterized by containing at least one of 0.05 to 0.3%, and the balance being Al and unavoidable impurities (above weight%).