JP2994140B2 - Aluminum alloy plate for DI forming - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy sheet for forming, and more particularly to an aluminum alloy sheet for forming DI which is used for forming by ironing such as a DI can.

[0002]

2. Description of the Related Art AA3004 alloy (Al-1.25 wt% Mn-1.05 wt% Mg alloy) has been used as a body material of aluminum beer cans or general beverage cans. This alloy is originally used because it has excellent formability to some extent by cold rolling with a high degree of workability and has the necessary strength as a body material. However, in recent years, the thickness of the material has been required to be further reduced for the purpose of further cost reduction, and in response to this, the strength required for the body of the food can has become higher than before. Japanese Patent Application Laid-Open No.
A method for producing an aluminum alloy sheet utilizing precipitation of Mg ₂ Si as disclosed in Japanese Patent No. 105509, or a method utilizing precipitation hardening due to an Al—Cu—Mg based precipitate as disclosed in Japanese Patent Application Laid-Open No. 57-120648. Are known. On the other hand, improvement of productivity by reducing defects in the molding process as a cost reduction method has also been a major issue. In particular, with the progress of thinning and high strength, cracking during ironing becomes a problem. Therefore, the interaction between the precipitate and the cold roll was examined.
No. 5 is known. In previous studies, an improvement in strength and an improvement in moldability have resulted in contradictory results, and materials having high strength generally have inferior moldability. By the way, hydrogen atoms in a metal material have conventionally been regulated because they swell during heat treatment and become surface defects.
As a method of reducing the hydrogen content, a degassing process is performed by blowing an inert gas into the molten metal before casting, and the above problem is avoided at a hydrogen content of usually about 0.3 ml / 100 g or less.

[0003]

SUMMARY OF THE INVENTION The present invention has been made by searching for factors that affect the DI formability other than the factors that affect both the strength and formability as described above. An object of the present invention is to provide an aluminum alloy sheet for DI forming which has improved DI formability, especially ironing workability.

[0004]

That is, the present invention provides a method for producing Mn0.
8 to 1.5 wt%, Mg 0.7 to 1.3 wt%, Cu 0.05 to 0.3 wt%, Si 0.1 to 0.3 wt%
%, Fe 0.1 ~ 0.7wt%, Zn 0.1 ~ 0.25wt
% Or more, the balance consisting of Al and unavoidable impurities, and a hydrogen content of 0.12 ml.
/ 100 g, which is an aluminum alloy plate for DI molding.

[0005]

In the present invention, Mn forms an intermetallic compound together with Fe and Si, and is an indispensable element in the material for DI molding in order to prevent seizure on a die during ironing. If it is less than 0.8 wt% (hereinafter simply abbreviated as%), this effect is small, and it is not suitable for long-time molding.
On the other hand, when the content exceeds 1.5%, a huge compound is easily formed under ordinary casting conditions, and there is a high possibility that a large second phase becomes a starting point of crack generation during molding. Like Cu, Mg is an important element that mainly improves the strength of the alloy of the present invention by forming a solid solution. In addition, by forming a supersaturated solid solution state by solution treatment and quenching, Mg ₂ Si or Al-Mg-Cu-based precipitates are formed at the time of heat treatment at about 200 ° C. in paint baking after can molding, further improving strength. Can be planned. If the added amount of Mg is less than 0.7%, the required strength cannot be maintained, and if it exceeds 1.3%, seizure is likely to occur. By using a special casting method with a high solidification rate, it is possible to further increase the amount of Mg added to 2.5% by increasing the density of Mn-based precipitates having high seizure resistance. Fe also has the effect of improving the strength similarly to Mg, but less than 0.1% has little effect.
Addition of more than 7% results in the formation of a giant compound like the Mn element. Here, in the case of performing a continuous casting method or the like in which the cooling rate during casting is extremely high, the size of the compound can be suppressed to be small, so that the addition amounts of Mn and Fe can be further increased to twice. Cu can be expected to have the same effect as Mg. Therefore, if it is less than 0.05%, the effect of improving the strength cannot be expected, and if it exceeds 0.3%, the moldability is impaired and a problem arises in the corrosion resistance. S
Although i has low solid solution hardening property by itself, the fine compound formed in the initial stage of the heat treatment serves as a nucleation site for precipitates of other elements, thereby promoting the precipitation of other elements. Therefore, the addition of Si lowers the solid solution amount of Fe and Mn and promotes the precipitation of an Al-Mg-Cu-based compound that causes precipitation hardening. Further, by adding more Si, finer Al—Cu—Mg—Si based compound (Al ₅ Cu
₂ Mg ₈ Si ₆ metastable phase). To improve the strength, 0.1% or more is actually required. However, these precipitates are effective for improving the strength, but the latter compound is finer than the former, and significantly reduces the formability. Therefore, the amount of Si added needs to be 0.30% or less. Zn increases its strength mainly in a solid solution state. Therefore, if the amount is less than 0.1%, the effect is not expected, and if it exceeds 0.25%, the corrosion resistance is impaired.

[0006] Hydrogen atoms in an aluminum alloy segregate in a portion where the atomic arrangement of the parent phase is disordered. As a place where the atomic arrangement of the parent phase is disordered, there are a grain boundary, an interface between a crystallized substance and a precipitate, a shear band, and the like. Segregated hydrogen atoms reduce the strength of the interface. Therefore, it has been found that when the state is close to the forming limit, cracks are generated starting from these weakened interfaces. Conversely, by maintaining the strength of these interfaces, it is possible to avoid a decrease in formability when the strength of the alloy of the present invention is positively improved by a precipitation treatment or the like. In order to maintain the strength of the crack initiation point, the hydrogen content is less than 0.12 ml in 100 g of aluminum alloy,
More preferably, the amount of hydrogen is required to be less than 0.1 ml. In particular, the effect becomes apparent in the final ironing of DI molded cans subjected to multi-stage molding. In order to obtain such a low concentration of hydrogen content, it is necessary to blow an inert gas sequentially immediately before casting to sufficiently reduce the hydrogen content and then to immediately solidify.

[0007]

The present invention will be described in more detail with reference to the following examples. The molten Al alloy of each composition shown in Table 1 was passed through a two-stage filter to produce a 500 mm thick water-cooled cast ingot. Here, argon gas was blown into each filter to remove inclusions and perform degassing. 60 in these ingots
After a homogenization treatment at 0 ° C. for 5 hours, a normal hot rolling to a thickness of 3 mm, annealing at a temperature of 400 ° C. for 2 hours, followed by cold rolling to a final sheet thickness of 0.3 mm And For these test materials, the hydrogen content was measured, the tensile test, and the crack generation rate in DI processing were measured.
In the case of a normal molded body, the proof stress of the material after the paint baking treatment is particularly problematic. Thus, as the mechanical performance of the sample, a proof stress value after a heat treatment at 200 ° C. for 15 minutes corresponding to the baking treatment was used. As a formability evaluation method, in the DI processing, 1,000 standard cans having an internal capacity of 350 ml were continuously formed under the condition that the reduction rate of the plate thickness was fixed at 64%, and the number of cracking cans at this time was evaluated. . The evaluation criteria were as follows: no cracks: excellent, cracks in 1 to 4 cans: average level, cracks in 5 or more cans: inferior. Table 2 shows the hydrogen content, tensile performance and molding test results of these samples.

[0008]

[Table 1]

[0009]

[Table 2]

As is clear from Table 2, the present invention example No. 1 to
No. 3 is excellent in moldability, especially ironing workability, and shows that strength is maintained. On the other hand, in Comparative Example No. having a hydrogen content larger than the range of the present invention. 4 and 5 indicate that the ironing workability is equal to or less than the current level.

[0011]

As described above, the aluminum alloy sheet for forming a DI according to the present invention has very good ironing workability while maintaining the mechanical strength. Therefore, by using the aluminum alloy plate of the present invention, the productivity of the DI can is improved, and it is possible to respond to recent severe molding conditions and demands for cost reduction.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C22C 21/06

Claims (1)

(57) [Claims] 1. Mn 0.8-1.5 wt%, Mg 0.7-
1.3 wt%, and further 0.05-0.3 wt% Cu,
Si 0.1-0.3 wt%, Fe 0.1-0.7 wt%, Z
n containing at least one of 0.1 to 0.25 wt%, the balance being Al and unavoidable impurities, and having a hydrogen content of less than 0.12 ml / 100 g. Aluminum alloy plate for forming.