JP3234610B2 - Manufacturing method of aluminum alloy hard plate for beverage can lid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an aluminum alloy hard plate excellent in drawability, and more particularly to a shallow draw forming process having a small depth to diameter ratio, such as a lid for a beverage can. The present invention relates to a method for inexpensively manufacturing an aluminum-unim alloy hard plate having excellent shape freezing properties when performed.

[0002]

2. Description of the Related Art A lid of a recent beverage can is required to be easily openable and to have a strength after baking, and a hard plate made of an aluminum alloy is used.

Conventionally, an aluminum alloy plate used for such a can lid is formed by homogenizing an ingot, then hot rolling to a thickness of 3 to 5 mm, and cold rolling → intermediate annealing → final cold rolling. Is a hard plate of 0.4 mm or less. in this case,
In order to obtain sufficient strength, cold rolling of 80% or more is required, and when the cold rolling reduction is increased, there is a phenomenon that the overhang of the ear during drawing is increased.

Accordingly, the present applicant has proposed a method of inexpensively producing a hard plate having a small strength and a small protrusion (ear ratio) at the time of drawing, using Mn, Zr, Al-Mg based materials.
V, Ti adjusted aluminum alloy 300-350
A method has been proposed in which hot rolling or intermediate annealing is performed at 0 ° C., followed by cold rolling (Japanese Patent Publication No. 57-33332).

[0005]

SUMMARY OF THE INVENTION The above mentioned Japanese Patent Publication No. Sho 57-3
The aluminum alloy material produced by the method of No. 3332 without intermediate annealing, when subjected to shallow drawing such as a can lid, warps (Δh) on the bottom surface of the molded product as shown in FIG. Was found to occur. (The one with a small amount of warpage is said to have excellent shape freezing properties.)

When such a warp occurs, when the molded articles are stacked and moved on a belt conveyor or the like, not only lack of stability hinders smooth conveyance, but also disadvantages such as poor dimensional accuracy. Further, there is a disadvantage in that when the flattened can is fitted to the upper edge of the can body, a non-uniform gap is generated, and the hermeticity of the can is deteriorated.

Therefore, an object of the present invention is to produce an aluminum alloy hard plate excellent in shape freezing property by cold rolling without performing intermediate annealing after hot rolling, even when shallow drawing is performed. It provides a method.

[0008]

In order to solve the above-mentioned problems, various investigations have been conducted on the cause of the occurrence of warpage on the bottom surface of the molded product. As a result, the cause of the warpage is that coarse recrystallized grains formed during hot rolling are present. For this reason, they have found that the problem can be solved by making the recrystallized grains finer, and have completed the present invention.

The gist of the present invention is that Mg: 3.0 to 6.0.
%, Mn: 0.2 to 0.8%, Cu: 0.10 to 0.4
0%, Fe: 0.05 to 0.35%, Si: 0.05 to
An aluminum alloy ingot containing 0.25% and Ti: 0.01 to 0.05% is subjected to a homogenizing heat treatment, and thereafter, hot rolling is started at 350 to 450 ° C., and the material temperature at the end of rolling is 2
Alcohol for beverage can lids that performs cold rolling at a working rate of 70% or more without performing intermediate annealing at 50 ° C or more and less than 280 ° C.
This is a method for producing a minium alloy hard plate.

The operation of the above alloy components and processing conditions will be described. Mg:

Mg is a basic additive element in the present invention and contributes to strength. If Mg is less than 3.0%, the required strength cannot be obtained. If it exceeds 6.0%, cracks tend to occur during hot rolling.

Mn: Like Mg, it contributes to strength. Further, there is an effect of making recrystallized grains fine. When the amount of Mn added is 0.
If it is less than 2%, the effect is small, and if it exceeds 0.8%, the hot workability is reduced, and it is easy to form an Al-Fe-Mn-based coarse intermetallic compound at the time of ingot making, and the formability of the hard plate is also improved. Lower.

Cu: Cu forms a fine precipitate of an Al-Mg-Cu compound and contributes to strength. If it is less than 0.10%, this effect is small, and if it exceeds 0.40%, cracks tend to occur during hot rolling.

Fe: Fe is effective in refining recrystallized grains. If the added amount of Fe is less than 0.05%, the effect is small, and if it exceeds 0.35%, Al-Fe-
A Mn-based coarse intermetallic compound is easily formed, and the formability of the hard plate is deteriorated.

Si: Si promotes the precipitation of Mn and forms an Al-Mn-Si-based compound. The precipitate prevents coarsening of recrystallized grains. It is not economical to purify the amount of Si added to less than 0.05%, and the effect of refining recrystallized grains is diminished. If it is added in excess of 0.25%, the formability of the hard plate decreases.

Ti: Ti has an effect of making crystal grains fine. If the added amount is less than 0.01%, the desired effect cannot be obtained in the above-mentioned action. On the other hand, if the added amount is more than 0.05%, the effect is not so large, but a coarse compound is formed, It deteriorates the formability of the plate.

After ingoting the aluminum alloy by a conventional method, it is preferable to perform a homogenization treatment prior to hot rolling to remove segregation of solute atoms. This homogenization treatment is usually performed at 480 to 530 ° C. for 3 to 10 hours.

Hot rolling is usually started after heating to about 500 ° C., but the higher the temperature, the more unfavorably the recrystallized grains during rolling tend to become coarse. If the starting temperature is too low, the efficiency becomes industrially poor, and the end temperature is too low. The optimum rolling start temperature is 350 ° C. or more and 450 ° C. or less. This temperature is the material temperature at the start of hot rolling, and the heating temperature of the ingot may be higher than this. However, in consideration of productivity, it is desirable to set the preheating to 500 ° C. or less.

The hot rolling end temperature is the condition to be most strictly controlled. At 280 ° C. or higher , the recrystallized grains become coarse and the shape freezing property deteriorates. It does not recrystallize below 250 ° C,
The ear ratio of the final plate is too high or the formability is deteriorated.
The desired end temperature is between 250 and 280C.

If the hot rolling conditions are controlled as described above, it is not necessary to perform intermediate annealing. Thereafter, by adding final cold rolling of a rolling amount of 70% or more, strength, formability, ear ratio, shape freezing property are obtained. To obtain a hard plate with excellent properties.

If the rolling amount is less than 70%, the desired material strength as a can lid material cannot be obtained. Also, if the rolling amount is too large, the ear ratio and the formability deteriorate, so the rolling amount is desirably within 90%.

[0022]

[Table 1]

After dissolving an aluminum alloy having the composition shown in Table 1 above, agglomerating and homogenizing at 500 ° C. for 4 hours,
Under the conditions shown in Table 2, hot rolling and cold rolling are performed.
After 2 hours of stabilization at 175 ° C., mechanical properties, Erichsen test, shallow draw test and deep draw test (ear rate) were performed.

As shown in FIG. 4, the shallow drawing test was conducted with a blank diameter of 60 mm, a flat bottom punch diameter of 50 mm, and a drawing ratio of 1.2.

The amount of warpage of the bottom surface is determined from the top surface of the drawn cup by using a contracer (CB-41 contour measuring device manufactured by Mitoyo) as shown in FIG. 1 with a cross section parallel to the rolling direction of the test material. Δh was measured. The cross section of the sample was observed with a microscope, and the size of the crystal grain was measured. Tables 2 and 3 show these results.

[0026]

[Table 2]

[0027]

[Table 3]

The Nos. 1 to 5 of the invention examples have a proof stress of 333 Mpa.
As described above, a tensile strength of 382 MPa or more, an elongation of 7% or more, an Erichsen value of 4.5 mm or more, a bottom surface warpage of 0.93 mm or less, an ear ratio of 4.5% or less, and a crystal grain size of 10 to 15 μm are obtained. Obtained. FIG. 2 shows a polarizing microscope structure of No. 1 material after hot rolling.

On the other hand, No. 6 of the comparative example had a hot rolling start temperature of 500 ° C. and an end temperature of 320 ° C., all of which were high, and the grain size after hot rolling was 26 μm, as shown in FIG. And the amount of bottom warpage increased to 1.12 mm.

In No. 7, the hot rolling end temperature was as low as 230 ° C. and the recrystallized structure was not obtained, so that the ear ratio was as large as 6.9%.

No. 8 has a hot rolling start temperature as high as 500 ° C., crystal grains of 20 μm, and a bottom warpage of 1.05.
mm.

In No. 9, the cold rolling reduction ratio was as low as 60%, and the proof stress was as low as 289 Mpa.

In No. 10, Mg in the aluminum alloy was as low as 2.5%, and the proof stress was as low as 278 Mpa.

In No. 11, the Fe of the aluminum alloy was as high as 0.55%, and the Erichsen value was as low as 3.8 mm.

In No. 12, since the Cu in the aluminum alloy was as high as 0.65%, cracks occurred during hot rolling, and the test was interrupted.

In the case of No. 13, the intermediate annealing was performed, but the ear ratio was undesirably high at 5.9%.

[0037]

As described above, according to the present invention, even if cold rolling is performed immediately after hot rolling, the mechanical properties are comparable to those of conventional materials, the amount of bottom warpage is small, and the shape freezing property is low. An aluminum alloy hard plate for a good beverage can lid can be manufactured at low cost, which is an industrially useful invention.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of the amount of warpage of a bottom surface.

FIG. 2 is a polarizing microscope photograph showing the alloy structure of No. 1 material after hot rolling.

FIG. 3 is a polarizing microscope photograph showing an alloy structure of hot rolled No. 6 material as a comparative example after completion of hot rolling.

FIG. 4 is a diagram for explaining a test method.

────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI C22F 1/00 683 C22F 1/00 683 694 694A 694B 63-293144 (JP, A) JP-A-2-185955 (JP, A) JP-A-3-6356 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22F 1/04 -1/057 C22C 21/00-21/18

Claims (1)

(57) [Claims] 1. Mg: 3.0 to 6.0% (mass%, the same applies hereinafter), Mn: 0.2 to 0.8%, Cu: 0.10 to 0.10
0.40%, Fe: 0.05-0.35%, Si: 0.
After performing an homogenizing heat treatment on an aluminum alloy ingot containing 0.05 to 0.25% and Ti: 0.01 to 0.05% and the balance being Al and unavoidable impurities, hot rolling was performed at 350 to 4%.
Starting at 50 ° C., the material temperature at the end of rolling is set to 250 ° C. or more and less than 280 ° C., and the working rate is 7 without intermediate annealing.
A method for producing an aluminum alloy hard plate for a beverage can lid , wherein cold rolling of 0% or more is performed.