JPH10121176A - Aluminum alloy plate excellent in flange formability for di can drum and manufacture therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide aluminum alloy plate for DI can drum capable of maintaining excellent flange formability even when the contents of Si and Zn in the scrap get higher owing to an increased blending rate. SOLUTION: The alloy contains 0.7-1.3wt.% Mg, 0.8-1.3wt.% Mn, 0.3-0.7wt.% Fe, 0.1-0.5wt.% Si, <=0.5wt.% Zn, 0.005-0.1wt.% Ti alone or in combination of 0.0001-0.1wt.% B, and, as necessary, <=0.3wt.% of each of one or two kinds of Cu or Cr, alkali metals as impurities controlled not to exceed 1ppm and the balance Al with other inevitable impurities.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DI having excellent flange formability and capable of increasing the mixing ratio of scrap.
The present invention relates to an aluminum alloy sheet for a can body and a method for producing the same.

[0002]

2. Description of the Related Art Two-piece aluminum D which is formed by deep drawing and ironing sequentially on an aluminum alloy plate to form a can body
The I can body has been widely used as a container for beer and carbonated drinks. As can body materials for such applications,
JIS-3004 aluminum alloy hard plate is used exclusively because it has good formability and strength. The forming process of the aluminum DI can body is as follows. The JIS-3004 aluminum alloy hard plate having a thickness of about 0.28 to 0.37 mm is formed by DI forming (cupping forming ⇒ redraw forming ⇒ three-step continuous ironing) to form a straight can. (The thickness of the side wall portion of this straight can is about 100 to 110 μm, and the thickness of the side wall tip portion to be subsequently necked and flanged is about 15 μm.
0-180 μm is set slightly thicker), then trimming (edge cutting), degreasing cleaning, chemical conversion treatment, inner and outer surface coating, baking heating are sequentially performed, and necking is performed to reduce the diameter of the opening. Lastly, flange forming (mouth opening forming) for facilitating tightening with the can lid is performed. Then, after filling contents such as beverages, the end (lid) is double-wrapped and sealed. This JIS-3004 aluminum alloy plate is manufactured by a series of steps of casting, facing, homogenization, hot rolling, and cold rolling. Further, if necessary, after the cold rolling, finish annealing, degreasing and washing, and application of a lubricating oil for cupping are performed. In order to adjust the strength, it is customary to carry out intermediate annealing before or during the cold rolling.

[0003] In recent years, in order to further improve the economic efficiency of aluminum cans, the thickness of used materials and the use of scraps (UBC, Used Beverage Ca) have been reduced.
There is an increasing momentum to further thoroughly recycle n) into materials for can bodies. The thickness of the can body material varies depending on the type of can, but taking the most commonly used 350 ml can as an example, the initial 0.4 mm has changed to 0.28 mm, and the development of further thinning Is being actively pursued. Along with such thinning, problems in can molding have been changing. That is, the reduction of the ear ratio and the prevention of the breakage in the DI molding process, which were the conventional problems, have been almost solved by recent advances in molding techniques and improvements in can materials.
However, with the progress of further thinning, necking after DI molding, and microcracking at the can end opening in the subsequent flange forming and can lid winding processes have emerged as new problems. Above all, with respect to the prevention of minute cracks at the opening of the can end, a solution is strongly desired. Also, the recycling rate (recycling rate) of used can scrap (UBC) was at most a few years ago.
However, recently, due to growing social momentum,
It has become 0-40%. In addition, there is an increasing demand to reduce costs by recycling various low-purity scraps used for other purposes than UBC as can materials.

[0004]

However, as the usage rate of the scrap increases, the purity of the can body material decreases, and a problem arises that the moldability decreases. Specifically, there is a problem in that Si and Zn derived from scrap increase, and the rate of occurrence of flange cracks in the can body increases. Conventionally, the content of Si was 0.1-0.2 wt%, but is now 0.1-0.2 wt%.
22 to 0.30 wt%, and Zn, which was about 0.02 wt% in the past, has now increased to 0.05 to 0.1 wt%, and tends to further increase in the future. Along with this, it has been found that cracks occur during flange forming (mouth expansion forming) and subsequent double-tightening with the end (lid), resulting in a problem that the contents leak.

[0005] From the above, the present inventors have conducted intensive studies and found that the alkali metal element as an impurity in the aluminum alloy plate has a very bad effect on flange formability. It has been found that by restricting the content to, good flange formability can be maintained even when the contents of Si and Zn are increased. Conventionally, an alkali metal element such as Na has been used as a main component of a material for cans.
It is known that it is easy to mix from the ingot, and if these elements are contained even in trace amounts, cracks are likely to occur in hot working such as casting or hot rolling, and the content is usually several tens ppm, and furthermore, 10 ppm. It is regulated as follows. However, no clear knowledge has yet been obtained on the effect of the alkali metal element on severe cold / warm formability. For example, JP-A-6-271968 and JP-A-6-2719
No. 69 discloses that if Na or K is 10 ppm or less,
It is suggested that there is no problem with DI moldability, but no specific example is given. No mention is made of the effect on flange formability. The present inventors,
The present inventor has obtained new findings while studying the effects of alkali metal elements on the formability, particularly the flange formability, when the contained elements are slightly changed by recycling of the material, and has completed the present invention. An object of the present invention is to provide an aluminum alloy sheet for a DI can body capable of maintaining good flange formability even when the content of Si and Zn is increased by increasing the mixing ratio of scrap, and a method for producing the same.

[0006]

According to the first aspect of the present invention,
0.7-1.3 wt% of Mg, 0.8-1.3 wt% of Mn
%, Fe 0.3 to 0.7 wt%, Si 0.1 to 0.5 w
t%, Zn 0.5 wt% or less, Ti 0.005 to 0.1
wt% alone or B 0.0001-0.1wt
%, And if necessary, one or two of Cu and Cr are contained in an amount of 0.3 wt% or less, and an alkali metal element as an impurity is regulated to 1 ppm or less, and the balance is Al and other unavoidable impurities. An aluminum alloy plate for a DI can body having excellent flange formability, comprising:

According to a second aspect of the present invention, there is provided a method for controlling the concentration of Mg in the range of 0.7 to 1.0.
3 wt%, Mn 0.8-1.3 wt%, Fe 0.3-
0.7 wt%, Si 0.1-0.5 wt%, Zn0.5
wt% or less, 0.005 to 0.1 wt% of Ti alone,
Alternatively, B is contained in combination with 0.0001 to 0.1 wt%, and if necessary, one or two of Cu and Cr are contained at 0.3 wt% or less, and an alkali metal element as an impurity is regulated to 1 ppm or less, The remaining part of the aluminum alloy ingot consisting of Al and other unavoidable impurities is subjected to homogenization treatment and hot rolling, and is recrystallized as necessary after hot rolling or during cold rolling after hot rolling. This is a method for producing an aluminum alloy for a DI can body having excellent flange formability, which comprises annealing, performing final cold rolling of 60 to 90%, and performing finish annealing as necessary.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The alloy elements of the present invention will be described below in detail. Mg gives the aluminum alloy plate the necessary pressure resistance as a can body. If the addition amount is less than 0.7 wt%, the strength is insufficient, and the pressure resistance required for the can body is insufficient. On the other hand, if the addition amount exceeds 1.3% by weight, the strength of the aluminum alloy sheet is too high, and the work hardens easily during DI molding, so that the frequency of occurrence of fractured bodies (iron cracks) increases. The optimum addition amount of Mg slightly varies depending on the addition amount of other elements and the manufacturing conditions, but a good range of the balance between the pressure resistance and the iron formability is 0.8 to 1.2 wt%, more preferably 0.85 to 1.2 wt%. The range is 1.15 wt%.

Mn improves the pressure resistance and the iron formability. In DI molding, emulsion-type or solve-type lubricants are usually used, but when the amount of Mn is small, lubricating properties alone are insufficient, and build-up by adhesion between an aluminum alloy plate and a mold is performed. And scuffs or burn-in called galling or scoring occur. Mn is α-Al
Form intermetallic compounds (crystallized compounds) such as ₁₂ (Fe, Mn) ₄ Si, Al ₆ Mn, and Al ₆ (FeMn), and the crystallized compounds have a solid lubricating action and suppress build-up. Therefore, there is an effect of preventing the occurrence of the galling or the like. Mn is α-Al
_It forms ₁₂ (Fe, Mn) ₄ Si and has the effect of suppressing the fracture in high-speed ironing. If the amount of Mn is less than 0.8 wt%, the ironing formability is insufficient and the pressure resistance is also insufficient. When the amount of Mn added exceeds 1.3 wt%, the iron moldability and the effect of improving pressure resistance are saturated, and a giant primary crystal compound of the Al-Mn-Fe system is likely to be generated at the time of melting and casting in combination with Fe described later. Since this remains even after rolling, the risk of cracks and pinholes occurring during molding increases.
The range of the optimum addition amount of Mn is in the range of 0.9 to 1.1 wt%.

[0010] Fe promotes the generation of the crystallized compound of Mn and makes its distribution uniform, thereby preventing the occurrence of galling or the like during DI molding. Fe added amount is 0.3wt
%, The effect is insufficient. If it exceeds 0.7% by weight, the Al-Mn-Fe-based giant primary crystal compound is liable to be generated, which causes pinholes, flanges, cracks in tightening, etc. Increase. The range of the optimum amount of Fe to be added is 0.35 to 0.45 wt%.

Si combines with Mn to form an α-Al ₁₂ (Fe, Mn) ₄ Si intermetallic compound having a solid lubricating effect, thereby suppressing build-up during DI molding and preventing galling and the like. It has the effect of preventing and preventing the occurrence of a broken body in high-speed ironing. 0.1w Si content
If the content is less than t%, the effect of preventing galling is insufficient, but if the content is large, the number of brittle Mg-Si based intermetallic compounds and simple Si increases, and the frequency of occurrence of cracks during flange forming increases.
Even if the alkali metal element is regulated to 1 ppm or less according to the present invention in order to increase the mixing ratio of scrap, Si
Has an upper limit of 0.5 wt%, more preferably 0.1 wt%.
4 wt%.

If Zn is contained up to about 0.1% by weight, no harm is caused.
And a brittle Mg-Zn intermetallic compound is formed, and the frequency of occurrence of cracks during flange forming increases. Even if the alkali metal element is regulated to 1 ppm or less according to the present invention, the allowable range is 0.5 wt% or less, more preferably 0.4 wt% or less.

[0013] Ti, or Ti and B, are added for uniform refinement of the ingot structure. If the content of Ti is less than 0.005 wt%, the effect of uniformly reducing the ingot structure cannot be obtained.
When the content exceeds 1 wt%, a giant primary crystal compound of Al-Ti system is liable to be generated at the time of melting and casting, and remains after rolling, so that the risk of generating cracks and pinholes at the time of molding increases. When B coexists with Ti, it has the effect of promoting the effect of making the ingot crystal grains of Ti uniform and fine. B is 0.0001wt
%, The effect cannot be sufficiently obtained, and if it exceeds 0.1% by weight, a Ti-B-based giant primary crystal compound is liable to be generated at the time of melting and casting. The risk of occurrence increases. Ti is 0.
01-0.03wt%, B is 0.0002-0.001
It is desirable that they be contained simultaneously in the range of wt%.

Since Cu or Cr improves the pressure resistance, it may be added up to 0.3 wt% as necessary (for example, for a high-pressure carbonated beverage can such as cider). When the addition amount exceeds 0.3 wt%, the strength of the aluminum alloy plate becomes too high, and the fracture rate increases.

Alkali metal elements have a very bad effect on flange formability. Here, the alkali metal element is N
a, Li, K, Rb, Cs, and Fr. Although the details of the mechanism by which the alkali metal element has an adverse effect on the flange formability are not well understood, the alkali metal element is Mg-
It is present as a monoatomic layer at the interface between the Si-based or Mg-Zn-based intermetallic compound and the Al matrix, facilitating the propagation of cracks due to cracking or peeling of these intermetallic compounds and deteriorating flange formability. It is estimated that there is not. The conventional aluminum alloy sheet for a can body has an alkali metal element content in the range of 3 to 10 ppm.
When the amount of i and Zn was small, the problem did not appear, but the amount of Si was 0.3 wt% or more, and the amount of Zn was 0.1 wt%.
In this case, the flange formability cannot be ensured unless the amount of the alkali metal element is restricted to 1 ppm or less. As a means for reducing the amount of the alkali metal element, it is sufficient to take a means such as blowing an argon gas containing chlorine at a stage of the molten metal treatment before casting for a sufficient time to float it on the surface of the aluminum molten metal as chloride and remove it as slag. .

There is no particular problem for impurities other than the alkali metal element as long as they are within the range of JIS-3004.

Next, the manufacturing conditions in the present invention will be described. The aluminum alloy ingot of the above composition is subjected to homogenization treatment as necessary after face milling to diffuse and eliminate micro segregation of added elements such as Mn, uniformize the distribution of solid solution atoms, and reduce the ear ratio and the fracture ratio. Lower. This homogenization process is 560-6.
It is desirable to apply at 30 ° C. for 3 hours or more. Further, after the homogenization treatment, it is more preferable to perform a second-stage homogenization treatment at 400 to 530 ° C. for 1 hour or more, since the ear ratio decreases.

Next, hot rolling is performed by a conventional method, and if necessary, annealing for recrystallization is performed after hot rolling or during cold rolling after hot rolling. This annealing may be performed at 300 to 400 ° C. for 1 hour or more in a stationary batch furnace, or at 350 to 600 ° C. for 10 minutes or more in a continuous annealing furnace.

Next, final cold rolling is performed, and the rolling reduction is in the range of 60 to 90%. Final cold rolling rate is 60%
If it is less than 3, the recovery by baking heating during can-making is not sufficient, and the flange formability decreases. On the other hand, if the final cold rolling ratio exceeds 90%, the strength is too high, and cupping cracks and ironing cracks (fractures) easily occur during DI molding.

Further, after the final cold rolling, finish annealing is performed if necessary. The purpose of the finish annealing is to impart appropriate ductility to the final cold-rolled base plate when the elongation of the base plate is small, and to prevent the occurrence of wrinkles and cup cracks at the bottom of the can. Desirable conditions for finish annealing are 100 to 1
1 hour to 5 hours at 50 ° C.

Further, if necessary, the final cold-rolled alloy sheet or the alloy sheet subjected to finish annealing after the final cold rolling is subjected to washing, straightening, and applying a lubricating oil for cupping by a conventional method. This is a finishing process commonly performed by those skilled in the art.

The aluminum alloy sheet produced by the above-described production method is excellent in high-speed ironing formability, and is thus very suitable as a material for DI can bodies for high-speed can-making.

[0023]

Embodiment 1 Hereinafter, the present invention will be described in more detail with reference to embodiments. (Example 1) Various aluminum alloys having compositions of Nos. A to S shown in Table 1 were melt-cast by a conventional method, and after face milling, 610 ° C.
, At 490 ° C for 2 hours.
The second stage of time homogenization was performed. Then, using a reverse hot rough rolling mill, the starting temperature is 440 ° C. and the thickness is 490 mm.
To 25 mm. Subsequently, hot finish rolling was performed at a starting temperature of 350 ° C., an end plate thickness of 2.2 mm, and a coil winding temperature of 315 ° C. using a 4-tandem hot finishing rolling mill. Next, using a continuous annealing furnace, annealing was performed at 380 ° C. for 0 minutes, and immediately cooled. After that, the final cold rolling was performed to 0.30 mm (final cold rolling rate: 86%, the number of cold rolling passes was three), and finally, lubricating oil for cleaning, straightening, and cupping was applied by a conventional method, and the aluminum for DI can body was formed. An alloy plate was used. The aluminum alloy plate thus obtained was subjected to a bake equivalent treatment (205 ° C. × 20) by a tensile test.
Min) The strength before and after was measured. 350 at the canning line
Each 10,000 cans were formed (made into cans) on a DI can body (side wall thickness: 105 μm, final third ironing rate: 40%) having a capacity of ml. The number of cracking cans at this time was examined. Next, after successively performing trimming (edge cutting), degreasing and cleaning, chemical conversion treatment, inner and outer surface coating, baking heating (at 200 ° C. for 20 minutes), necking is performed to reduce the diameter of the opening, and flange forming (mouth opening). Molding)
Then, after filling the carbonated beverage, an end and a winding process were performed. Further, the can body after baking was subjected to mouth expansion molding by a conical (90-degree open angle) jig, and the expansion rate of the diameter until cracks were generated was measured to evaluate the expansion rate. In addition, baking heating of cans (20
After 20 minutes at 0 ° C.), the pressure resistance was measured by a hydraulic load method. In addition, the number of cracking cans at the time of forming the DI can body, at the time of forming the flange, and at the time of crimping were examined. Table 2 shows the results.

[0024]

[Table 1]

[0025]

[Table 2]

As is evident from Table 2, the composition of the present invention
o. A to F have an alkali metal element (mainly Na) of 1 ppm or less, so that even if the amount of Si and Zn is increased, the pipe expansion ratio is as good as 14% or more, and the rate of occurrence of cracks in flange forming and crimping is zero. It shows good flange formability and no other problems on the can-making. On the other hand, No. G containing less Mg and Mn has low strength after baking-equivalent treatment, that is, low pressure resistance as a can body. No. I, in which the amounts of Fe and Si were small, caused galling. No. J, to which Ti and B were not added, had a rough ingot structure, and when it was made into a can, a rough appearance-like poor appearance occurred.
No.J having a large amount of Mg and Mn had cupping cracks. No. K, which has a large amount of Fe and Si, had a flange / rolling crack. In No. L, which has a large amount of Ti and B, pinholes and fractures occurred, and flange cracks and crimping cracks also occurred.
Nos. M and N, which are rich in Cu and Cr, were broken. Si,
No. O, P, and Q, which contain a large amount of Na even when Zn is within the range of the present invention, had flange cracks and crimping cracks. Even in the case of Na in the present invention, too much Si and Zn resulted in No. R and S, which also had flange cracks and crimp cracks.

(Example 2) The No. F aluminum alloy ingot of Example 1 was subjected to the first-stage homogenization treatment at 615 ° C for 7 hours.
A second-stage homogenization treatment was performed at 00 ° C. for 3 hours and hot-rolled. Subsequently, cold rolling, annealing, final cold rolling, and finish annealing were performed. Table 3 shows the detailed conditions. The aluminum alloy plate thus obtained was evaluated in the same manner as in Example 1. Table 4 shows the results.

[0028]

[Table 3]

[0029]

[Table 4]

As is clear from Table 4, Nos. 1 to 4 according to the process of the present invention have good flange formability and have no problem in can making. On the other hand, No. 5 having a low final cold rolling reduction had poor flange formability, and Nos. 6 and 7 having too high a final cold rolling reduction caused cupping cracks and fractures.

[0031]

As described above, according to the present invention,
An aluminum alloy plate for a DI can body that is excellent in flange formability and can increase the compounding ratio of scrap is obtained,
It contributes to resource recycling and has a remarkable industrial effect.

Claims (2)

[Claims] 1. Mg 0.7-1.3 wt%, Mn 0.8
To 1.3 wt%, Fe 0.3 to 0.7 wt%, Si0.
1 to 0.5 wt%, Zn 0.5 wt% or less, Ti0.0
0.05 to 0.1 wt% alone or B0.0001
-0.1 wt% in combination with C
one or two of each of u and Cr are contained in an amount of 0.3 wt% or less, and an alkali metal element as an impurity is 1 ppm.
An aluminum alloy plate for a DI can body having excellent flange formability, characterized by the following restrictions, with the balance being Al and other unavoidable impurities. 2. Mg 0.7 to 1.3 wt%, Mn 0.8
To 1.3 wt%, Fe 0.3 to 0.7 wt%, Si0.
1 to 0.5 wt%, Zn 0.5 wt% or less, Ti0.0
0.05 to 0.1 wt% alone or B0.0001
-0.1 wt% in combination with C
one or two of each of u and Cr are contained in an amount of 0.3 wt% or less, and an alkali metal element as an impurity is 1 ppm.
Regulated below, the balance is aluminum alloy ingot consisting of Al and other unavoidable impurities, homogenization treatment, subjected to hot rolling, cold rolling after hot rolling or hot rolling as necessary Recrystallization annealing is performed on the way, and the rolling rate is 60 to 9
A method for producing an aluminum alloy for a DI can body having excellent flange formability, wherein a final cold rolling of 0% is performed and finish annealing is performed as necessary.