JP2005048288A - Aluminum alloy sheet for bottle can excellent in shape stability and strength of bottom part - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a bottle can material excellent in the shape stability and strength of the bottom part. <P>SOLUTION: An aluminum alloy sheet having a composition containing, by mass, 0.2 to 0.4% Si, 0.25 to 0.55% Fe, 0.15 to 0.35% Cu, 0.7 to 1.2% Mn, 0.8 to 1.4% Mg, 0.10 to 0.3% Zn and 0.01 to 0.15% Ti, and the balance Al with inevitable impurities, and in which proof stress after baking is 245 to 270 MPa, also, the ratio of crystallized products with the maximum length of ≥1 μm is 2 to 5% by area ratio based on the surface of the rolled sheet, and the number thereof is 4,000 to 10,000 pieces per mm<SP>2</SP>is used. The bottle can material excellent in the shape stability and strength of the bottom part can be obtained. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an aluminum alloy plate for a bottle-type beverage can in which a body portion, a shoulder portion, and a mouth portion are integrally formed, and in particular, an aluminum alloy plate for a bottle-type beverage can excellent in shape stability and strength of a bottom portion. It is related to.

Conventionally, aluminum cans for beverages are generally produced by drawing and ironing an aluminum alloy plate, and a two-piece can in which the can body and the bottom of the can are integrated, and a simple can lid called an easy open end. The method of opening the opening by tab operation was the mainstream.
On the other hand, recently, with the increase in demand for canned beverages and the like, the demand for bottle-shaped beverage cans made of aluminum alloy that can be resealed by caps has increased rapidly.
As a conventional technique, an aluminum plate for a bottle can is disclosed. (For example, see Patent Document 1.)
JP 2002-256366 A

  In the case of a bottle can, the thickness of the portion formed in the neck portion, screw portion, etc. is thicker than the portion formed in the body portion during DI processing to ensure the strength during necking. Thus, if the plate | board thickness difference with a trunk | drum and a neck part etc. is large, it will become difficult to remove | remove a can body from a punch after DI process. Therefore, more excellent stripping properties are required so that the punch can be easily removed from the can body. If the strip property is poor, the bottom shape becomes unstable. For example, the bottom portion and a part of the vicinity thereof are dented and bulged. When the dents and bulges are generated in this way, an error occurs in the dimensions of the bottle can by the amount of the irregularities, resulting in an abnormal shape. If neck processing, screw processing, or the like is performed with such a dimensional error, an error occurs in the bottle height, neck shape, and screw shape, that is, an abnormal shape is generated. As a result, capping defects such as insufficient capping properties and difficult cap closure occur.

Also, when capping after filling the contents into the bottle can, fix the bottle can with a strong restraining force from above, press the roller with the shape along the bottle screw part against the cap part, rotate the roller to the cap Form a screw and capping. If the bottom is deformed by the strong restraining force from above during capping and the bottle is lowered in height or has a shape abnormality, normal capping cannot be performed, so that a certain degree of strength is required for the bottom portion.
Further, in the molding process such as neck process and screw process, since the bottom part is fixed and the molding process is performed, the stability of the shape of the bottom part is a very important factor for the molding process and capping of the bottle can.
In view of the above problems, an object of the present invention is to provide an aluminum alloy plate that is less likely to be deformed in the bottom part in the bottle can molding process and can have excellent stability of the shape of the bottom part. is there.

  In order to solve the above-mentioned problems, the present inventors controlled the content of Si, Fe, Mn, Mg, etc., the area ratio and the number of crystallized substances within an appropriate range, and good stripping properties during DI processing. As a result, it was found that the stability of the good shape of the bottom portion can be obtained. In addition, the aluminum alloy plate that can secure the strength of the bottom portion by regulating the content of the above elements and the proof stress after baking within an appropriate range, and can also obtain the stability of the good shape of the bottom portion during each forming process. It has been found that can be realized, and the present invention has been achieved.

That is, in order to obtain good stripping properties during DI processing, the alloy composition in terms of mass% is Si: 0.2 to 0.4%, Fe: 0.25 to 0.55%, Cu: 0.15 to Contains 0.35%, Mn: 0.7-1.2%, Mg: 0.8-1.4%, Zn: 0.10-0.3%, Ti: 0.01-0.15% In addition, a crystallized product having a composition composed of Al containing the inevitable impurities in the balance and having a maximum length of 1 μm or more is 2 to 5% in terms of the area ratio as viewed from the surface of the rolled sheet, and 4000 per 1 mm ^2. The aluminum alloy plate which is 10000 pieces was used as the plate material for the bottle can.

  Moreover, in order to ensure the strength of the bottom part so as to ensure the stability of the good shape of the bottom part during each molding process, the alloy composition is the same as above, and the yield strength after baking is 245 to 270 MPa. An aluminum alloy plate was used as a plate material for a bottle can.

  Moreover, the trimming process after a neck process can be decreased by making an ear rate into 6% or less.

That is, according to the aluminum alloy plate of the present invention, the alloy composition is Si: 0.2 to 0.4%, Fe: 0.25 to 0.55%, Cu: 0.15 to 0.35% in mass%. , Mn: 0.7 to 1.2%, Mg: 0.8 to 1.4%, Zn: 0.10 to 0.3%, Ti: 0.01 to 0.15%, the balance being The crystallized product having a composition composed of Al containing inevitable impurities and having a maximum length of 1 μm or more is 2 to 5% in terms of the area ratio viewed from the surface of the rolled plate, and is 4000 to 10,000 per 1 mm ^2. Therefore, by controlling and combining the alloy composition, yield strength after baking and distribution of crystallized materials within an appropriate range, a bottle can material having excellent bottom shape stability and strength can be obtained while keeping the ear ratio low. be able to.

First, the reason for limiting the composition of the aluminum alloy of the present invention will be described.
Si: 0.2 to 0.4%
Si forms a compound together with Mg contained at the same time and exerts a hardening action, and also forms a crystallized substance with Al, Mn, Fe, etc., and exhibits an effect of preventing seizure to the die during DI processing. If the Si content is less than 0.2%, the desired lubrication performance cannot be exhibited, which is insufficient to prevent seizure on the die. On the other hand, if the Si content exceeds 0.4%, the material becomes brittle and the workability such as neck processing and screw processing deteriorates. Therefore, the appropriate content of Si is set to 0.2 to 0.4%.

Fe: 0.25 to 0.55%
Fe exhibits the effect of miniaturizing crystal grains and preventing seizure on the die during DI processing. If it is less than 0.25%, the area ratio and the number of crystallized substances are lowered and the desired effect cannot be obtained, and if it exceeds 0.55%, the area ratio and the number of crystallized substances increase and become brittle and neck processing, screws Processability such as processing deteriorates. Therefore, the proper content of Fe is 0.25 to 0.55%. For the same reason, it is desirable that the lower limit is 0.35% and the upper limit is 0.50%.

Cu: 0.15-0.35%
Cu easily forms an intermetallic compound with Mg and contributes to the hardening action. If it is less than 0.15%, these effects are poor, and if it exceeds 0.35%, workability such as neck machining and screw machining deteriorates. Therefore, the Cu content is limited to 0.15 to 0.35%. For the same reason, it is desirable to set the lower limit to 0.2% and the upper limit to 0.3%.

Mn: 0.7 to 1.2%
Mn easily forms a crystallized substance together with Fe, Si, Al, etc., and exhibits the effect of preventing seizure on the die during DI processing. If it is less than 0.7%, desired curing characteristics cannot be obtained, and if it exceeds 1.2%, it becomes brittle and the workability such as neck processing and screw processing deteriorates. Therefore, the Mn content is limited to 0.7 to 1.2%. For the same reason, it is desirable to set the lower limit to 0.8% and the upper limit to 1.1%.

Mg: 0.8 to 1.4%
Mg has a solid solution strengthening action, enhances work hardening at the time of rolling, and exhibits a dispersion precipitation hardening action by coexisting with the Si and Cu. If it is less than 0.8%, these functions and effects are not sufficiently exhibited. If it exceeds 1.4%, the yield strength after baking becomes too high, and workability such as necking and screwing deteriorates. Therefore, the Mg content is limited to 0.8 to 1.4%. For the same reason, it is desirable that the lower limit is 0.9% and the upper limit is 1.3%.

Zn: 0.10 to 0.3%
Zn has the effect of refining the precipitated intermetallic compounds of Mg, Si, and Cu.
If it is less than 0.10%, the above action is insufficient, and if it exceeds 0.3%, workability such as neck machining and screw machining and corrosion resistance deteriorate. Therefore, the Zn content is limited to 0.10 to 0.3%. For the same reason, it is desirable to set the lower limit to 0.15% and the upper limit to 0.25%.

Ti: 0.01 to 0.15%
Ti exhibits the effect of refining crystal grains and improving workability. If the content is less than 0.01%, these effects cannot be exhibited. If the content exceeds 0.15%, a coarse compound is formed, and workability such as neck processing and screw processing deteriorates. Therefore, the Ti content is limited to 0.01 to 0.15%. For the same reason, it is desirable to set the lower limit to 0.01% and the upper limit to 0.10%.

  In addition to the essential components described above, impurities may contain Zr: 0.1% or less and Cr: 0.1% or less in terms of mass%.

Yield strength after baking: 245 to 270 MPa
By defining the range of the yield strength after baking according to the present invention, the stability of the good shape of the bottom portion can be obtained during neck processing, screw processing, capping and the like.
If the proof stress after baking is less than 245 MPa, the bottom strength is insufficient and stability of the shape of the bottom part cannot be obtained during necking, screwing, capping, etc. If it exceeds 270 MPa, molding such as necking and screwing is performed. Deteriorates. Preferably it is 251-265 MPa. Yield strength after baking is to ensure the strength of the body part by the precipitation hardening of intermetallic compounds by the elements contained in the material if solution treatment (intermediate annealing performed by continuous annealing at 500 ° C. or higher) is performed at the time of manufacturing the material. . In addition, precipitation hardening does not occur unless a solution treatment is performed at the time of manufacturing the raw material, but in the present invention, the yield strength after baking may be 245 to 270 MPa. In the above-mentioned continuous annealing, a heating rate of 10 to 200 ° C./second, a holding temperature of 500 to 560 ° C., a holding time of 1 to 30 seconds, and a cooling rate of 10 to 200 ° C./second can be exemplified.
Thus, by restricting the proof stress after baking to an appropriate range, a necessary strength is obtained for the bottom portion, and the stability of the shape of the bottom in the molding process can be ensured.

Crystallized material on the surface of the plate (maximum length of 1 μm or more): area ratio of 2 to 5%, number of 4000 to 10,000 per 1 mm ² for crystallized substances having a maximum length of 1 μm or more, less than 2% of area ratio, or 1 mm ² If the number is less than 4000, the DI processability is lowered and the stripping property is deteriorated. On the other hand, if the area ratio exceeds 5% or more than 10,000 per 1 mm ² , the formability such as neck processing and screw processing deteriorates.
Thus, by regulating the crystallized material on the surface of the plate to an appropriate range, it is possible to ensure a good strip property during DI processing, and as a result, to obtain a good shape stability of the bottom portion.

Ear ratio: 6% or less When the ear ratio exceeds 6%, the number of trimmings after the neck processing step increases, which is not preferable. A preferable range of the ear ratio is 3% or less. In order to make the ear rate 6% or less, the final cold rolling rate is desirably 88% or less, but the manufacturing method is not limited.

The present invention will be specifically described below with reference to examples.
An aluminum alloy having a composition (residual Al + inevitable impurities) shown in Table 1 was used as a material. The molten metal of each alloy was cast into a slab by semi-continuous casting by a conventional method. Then, after heating to 600 ° C. and homogenizing, it was hot-rolled to a thickness of 6.5 mm and subsequently cold-rolled to a thickness of 0.4 mm. During the cold rolling, intermediate annealing was performed in a continuous annealing furnace at a thickness of 360 mm at a thickness of 1.2 mm and 550 ° C. at a thickness of 1.0 mm. In Comparative Material 1, hot rolling was performed up to 4.0 mm, and the intermediate annealing was not performed. Using the aluminum alloy plate blank thus obtained, it was processed into a bottle-type beverage can.
The ear rate was calculated from the ear height of a squeezed cup formed by squeezing a blank having a diameter of 62 mm with a 33.8 mm punch.
Baking conditions are 210 ° C. and 10 minutes.
Further, the test material after baking, was polished to a mirror with 0.1μmAl ₂ O ₃ abrasive material surface, using EPMA (JEOL JXA-8800 type electron probe microanalyzer), an accelerating voltage 15kV A composition image was taken at an irradiation current of 5 × 10 ⁻⁹ A. Then, the composition image was binarized by contrast, and a crystallized material that appeared brighter than the aluminum matrix was extracted, and its area and maximum length (maximum chord length) were obtained. And about the crystallized substance whose maximum length is 1 micrometer or more, the area ratio seen from the rolled-sheet surface and the number per 1 mm < ² > were measured.
The stability of the bottom shape was 100 cans, and finally, all the capping was performed normally ○, there were 1-4 defective cans, Δ, 5 or more defective products × As evaluated.
The screw workability was evaluated as “◯” when no screw cracking occurred and no cracking, and “X” when cracking occurred.
The trimming property was evaluated as ○ when the difference between the peak and valley of the ear was 0.7 mm or less after neck processing, and x when the difference exceeded 0.7 mm.

Claims (2)

In mass%, Si: 0.2 to 0.4%, Fe: 0.25 to 0.55%, Cu: 0.15 to 0.35%, Mn: 0.7 to 1.2%, Mg: 0 0.8 to 1.4%, Zn: 0.10 to 0.3%, Ti: 0.01 to 0.15%, the balance being made of Al containing inevitable impurities, and baking The crystallization product having a proof stress of 245 to 270 MPa and a maximum length of 1 μm or more is 2 to 5% in terms of the area ratio viewed from the surface of the rolled plate, and 4000 to 10,000 in number per 1 mm ^2. Aluminum alloy plate for bottle cans with excellent bottom shape stability and strength. The aluminum alloy plate for a bottle can excellent in stability and strength of the shape of the bottom portion according to claim 1, wherein the ear rate is 6% or less.