JPH0651901B2 - Method for producing aluminum alloy for drawing having high strength and low directionality - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention mainly relates to a method for producing an aluminum alloy for drawing suitable for a DRD can.

(Prior art and problems to be solved) Aluminum cans used for beverage cans such as beer and carbonated drinks or food cans are processed by DRD (Drawn and Redrawn) or DI (Drawn and Ironed).・
It is made by one of the ironing processes. The one obtained by the former processing method is called a DRD can, and the one obtained by the latter processing method is called a DI can.

DRD cans are usually cans with a plate thickness of 0.20 to 0.25 mm, and a typical process for manufacturing them is: coated coil → draw press (drawing and drawing) → redraw press → beading press (necessary) Depending on the side bead and neck bead processing). At this time, it is particularly important that the aluminum alloy as a raw material has the following properties (1) to (4).

(1) Material strength to obtain the required can bottom strength, (2) No distortion pattern that impairs the surface appearance (see "Fundamentals and Industrial Technology of Aluminum" published by Japan Light Metal Association (1986) p.139), ( 3) The occurrence of ears after redrawing is small, that is, the directionality is small, and (4) The flange workability of the end tightening part is excellent.

However, conventionally, the aluminum alloy added with a large amount of Mg for the requirement (1) has the drawback of (2), and if the cold rolling rate is increased, it becomes a material with a sharp ear and satisfies the requirement (3). There was a drawback of not doing it. Therefore, there has been a strong demand for a material that simultaneously satisfies the requirements (1) to (4) required for a DRD can.

On the other hand, the present inventors have previously filed Japanese Patent Application No. 63-0223.
In No. 11, we proposed a method that can satisfy these requirements at the same time. This method regulates each condition of homogenizing heat treatment, hot rolling, and intermediate annealing together with adjustment of chemical composition to obtain a structure having an intermetallic compound of a specific size and amount, and an appropriate finish cold rolling (40 to 50). %).

However, there is a demand for a material having a lower earring rate in a DRD can material having a higher drawing degree, and from the viewpoint of manufacturing the material, even if the finishing cold rolling rate is increased, a material having a low earring rate cannot be obtained. It has been desired to be developed, and further development of materials has been demanded.

The present invention has been made in order to meet such a demand, and mainly provides a method for producing an aluminum alloy for drawing, which has the above-mentioned requirements as a DRD can, particularly high strength and lower directionality. It is intended.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present inventor, based on the above proposal, further earnestly researched on the production conditions of the aluminum material, and as a result, reduced the Mn content, etc. If the composition is adjusted and the conditions of homogenizing heat treatment, hot rolling, and intermediate annealing are regulated to form a structure having a specific size and amount of intermetallic compound, this is subjected to finish cold rolling with a large cold rolling rate. However, it has been found that a material having a lower ear rate can be obtained.

That is, according to the present invention, Mg: 0.8 to 1.5%, Mn: 0.
30 to 0.50% and Cu: 0.05 to 0.80% are contained as essential components, and further Fe: 0.7% or less, Si: 0.4
% Or less, Zn: 0.5% or less, Cr: 0.05% or less and T
i: An aluminum alloy ingot containing one or two or more of 0.05% or less and the balance of Al and impurities, and subjected to homogenizing heat treatment at 500 to 600 ° C.
After hot rolling at 600 ° C, intermediate rolling and 350-5
Intermediate annealing at 50 ° C. is applied, and the diameter is 5 × 10 ² to 1 × 1.
A high strength and low directionality characterized by having a structure having an intermetallic compound of 0 ⁴ Å in a volume fraction of 0.5 to 3% and then performing finish cold rolling at a cold rolling rate of 40 to 70%. The gist is the method of manufacturing the aluminum alloy for drawing.

The present invention will be described in more detail below.

(Operation) First, the reasons for limiting the chemical components in the present invention will be described.

Mg: Mg is an element that gives strength, but if it is less than 0.8%, sufficient strength cannot be obtained, and if it exceeds 1.5%, a distorted pattern easily occurs on the can surface during molding, In addition, the work hardening becomes large when the finish cold rolling amount is increased, and the formability of the material is impaired. Therefore, the amount of Mg is set to 0.8 to 1.5%.

Mn: Mn gives strength and intermetallic compound with Al (Mn, Fe) Al
_Although it is an element necessary for forming No. ₆ , if it is less than 0.30%, sufficient strength cannot be imparted, and an intermetallic compound having a volume fraction of 0.5% or more cannot be formed. On the other hand, when Mn exceeds 0.50%, the texture due to cold working tends to develop, and the ear rate increases. In addition, a desired size (5 × 10 ² to 1 × 1)
The proportion of the intermetallic compound of 0 ⁴ Å) increases and the flange formability decreases. Therefore, the Mn amount is 0.30 to 0.5
The range is 0%.

Cu: Cu is an element necessary to give strength, but 0.0
If it is less than 5%, a sufficient effect cannot be obtained, and if it exceeds 0.80%, the strength becomes high, it becomes difficult to adjust the strength, and the corrosion resistance deteriorates, which is not preferable. Therefore,
The Cu content is in the range of 0.05 to 0.80%.

Each of the above elements is contained as an essential component, but in the present invention, one or more of the following elements Fe, Si, Zn, Cr, and Ti are contained in appropriate amounts.

Fe: Fe has an effect of imparting strength, and as a crystallized substance of (Fe, Mn) Si ₃ Al ₁₂ , it also has an effect of preventing seizure at the time of molding, and at the same time, Mn and (Mn, Fe) Al ₆ It is an element that forms an intermetallic compound. However, if it exceeds 0.7%, a coarse intermetallic compound (Mn, Fe) Al ₆ is formed, and a desired size (5 × 10 ² ~
A desired volume fraction (1 to 3%) of 1 × 10 ⁴ Å) cannot be obtained. Therefore, the Fe content is 0.7% or less.

Si: Si is an element that brings about the effect of preventing seizure during molding as a crystallized product of (Fe, Mn) Si ₃ Al ₁₂ described above, but if it exceeds 0.4%, a coarse crystallized product will be generated and You will lose your sex. Therefore, the Si content is 0.4% or less.

Zn: Zn is an element that provides strength, but if it exceeds 0.5%, the corrosion resistance deteriorates, so the Zn content is 0.5% or less.

Cr, Ti: Cr and Ti are elements that are added to finely control the structure, but if the content of each exceeds 0.05%, coarse intermetallic compounds are generated and formability is impaired. , Ti content is 0.05% or less.

Next, the manufacturing method of the present invention will be described.

The aluminum alloy having the above-mentioned chemical components is melted and cast by a conventional method to obtain an ingot. The ingot is cast by, for example, a DC casting method.

The obtained ingot needs to be subjected to homogenizing heat treatment at a temperature of 500 to 600 ° C. This homogenization heat treatment aims at homogenization of microsegregation and formation of a desired intermetallic compound. However, if it is less than 500 ° C, sufficient homogenization heat treatment (homogenization of microsegregation) and desired intermetallic compound (Mn, Fe) A
l ₆ (diameter 5 × 10 ² to 1 × 10 ⁴ Å, volume fraction 0.5 to
3%) cannot be formed, and if the temperature exceeds 600 ° C., eutectic melting or the like may occur, which is not preferable. The heating time is not particularly limited, but is preferably in the range of 3 to 24 hours at the above temperature.

Then, after the blast furnace, hot rolling is performed at a temperature of 600 to 270 ° C. to obtain a hot rolled plate of about 2 to 5 mm. At this time, 270
Cold rolling is introduced when rolling is carried out at a temperature below ℃,
A sufficiently uniform hot non-recrystallized structure cannot be obtained. The upper limit temperature of 600 ° C. is a value defined by the upper limit value of 600 ° C. of the homogenizing heat treatment temperature.

After that, intermediate rolling (cold rolling) is performed to 350 to 550.
Intermediate annealing is performed at a temperature of ° C to obtain a soft material. If the intermediate annealing temperature is less than 350 ° C, a sufficient soft material cannot be obtained, and 5
If the temperature exceeds 50 ° C, abnormally large particles will be generated, so 350
It shall be in the range of 550 ° C. The heating time of the intermediate annealing is 2 to 4 hours in the temperature range of 350 to 400 ° C., but in the case of the high temperature treatment using the continuous annealing furnace, it is, for example, 5 hours.
A heating time of 0.5 to 10 seconds at 00 ° C is a good guide.

By the above manufacturing process, a structure having a desired intermetallic compound, which is a feature of the present invention, can be obtained.

The main intermetallic compound is (Mn, Fe) Al ₆ , and metallurgically the ones that mainly belong to precipitates (Dispersoids),
As described above, the average diameter is 5 × 10 ² to 1 × 10 ⁴ Å and the volume fraction is 0.5 due to the optimum combination of the chemical components (particularly Mn and Fe contents), the homogenizing heat treatment, and the hot rolling temperature.
~ 3% is obtained. If the size is less than 5 × 10 ² Å, the strength of the material will be too high and the formability will be deteriorated. If the size is more than 1 × 10 ⁴ Å, cracks may occur during the molding process. It is not preferable. Further, if the volume fraction is less than 0.5%, the structure cannot be made sufficiently fine, and if it exceeds 3%, the moldability is deteriorated, which is not preferable.

Further, according to the present invention, since the amount of Mn is regulated to 0.30 to 0.50%, the amount of (Mn, Fe) Al ₆ produced is smaller than in the past, and the development of the texture during cold working occurs. The size is reduced, and at the same time, even if cold working of 40 to 70% is performed in the next step, a relatively low ear material can be obtained.

Finally, cold working is applied to the above-mentioned soft material having the desired intermetallic compound to make it a hard material, but sufficient strength cannot be obtained at a cold rolling ratio of less than 40%. On the other hand, 70
If the cold rolling rate exceeds%, a texture in which the crystal grains are oriented in the preferential direction develops due to the cold rolling, and the directionality occurs in the material, resulting in a peak height of about 3% or more when forming into a can, Increased trimming after molding is required, which significantly reduces product value. Therefore, the cold rolling rate of finish rolling is set in the range of 40 to 70%.

Through the above steps, a plate material having a thickness of about 0.20 to 0.25 mm can be obtained. This plate material, after painting by a normal method,
A desired can is formed by DRD processing in which drawing is performed twice or three times.

(Example) Next, the Example of this invention is shown.

Example 1 An aluminum alloy ingot having a chemical composition shown in Table 1 and having a thickness of 600 mm was melted by a DC casting method, and after chamfering, 575
C..times.6 hr of homogenizing heat treatment and hot rolling at a temperature of 550 to 300.degree. C. to obtain a hot coil having a thickness of 3.5 mm.

Then, a 0.50 mmt coil was obtained by intermediate rolling, an intermediate annealing was performed at 500 ° C. for 3 seconds in a continuous annealing furnace, and a 0.22 mmt hard plate was obtained by finish cold rolling (cold rolling rate 45%).

For the obtained material, the size and amount of the intermetallic compound were examined, and the as-manufactured and coating heat treatment (200 ° C. × 20 mi
The mechanical properties after n) were investigated, and the ear ratio, surface strain pattern, and flange formability were also evaluated. The results are also shown in Table 1.

In addition, the ear rate was determined by a punch diameter of 40 mmφ and a drawing rate of 40%. Also, the surface distortion pattern and the flange formability are good (good), ● It was evaluated by marking it with (Bad).

From Table 1, all of the aluminum alloy sheets of Inventive Examples No. 1 to No. 5 have an intermetallic compound of a size and amount within the scope of the present invention, have high strength, no surface distortion pattern, and ear ratio. Also, it is understood that it has excellent flange formability. On the other hand, the comparative example shows high strength, but a surface distortion pattern occurs,
Most of them are inferior in ear coverage and flange formability.

Example 2 Regarding the No. 1 aluminum alloy in Table 1, the final plate thickness 0.22 mmt was obtained by various manufacturing processes under the conditions shown in Table 2.
Of aluminum alloy hard plate was manufactured.

The material properties of the obtained material were evaluated in the same manner as in Example 1. The results are also shown in Table 2.

From the table, it can be seen that the aluminum alloy sheets of Inventive Examples No. 11 to No. 17 all have high strength, no surface strain pattern, and low ear ratio and excellent characteristics. On the other hand, Comparative Examples have chemical components within the scope of the present invention and have high strength, but are inferior in any of ear ratio, surface distortion pattern, rough surface, and flanging workability.

(Effects of the Invention) As described in detail above, according to the present invention, each condition of homogenizing heat treatment and hot rolling is regulated and applied to an aluminum alloy having a specific chemical composition, and a metal of a predetermined size and amount is applied. Since the structure having the intercalation compound is obtained, it is possible to manufacture an excellent aluminum alloy hard plate for drawing which has high strength, has no surface strain pattern, and has low directionality even if the finishing cold rolling rate is increased. It is particularly suitable for manufacturing DRD cans.

Claims (1)

[Claims] 1. In weight% (hereinafter the same), Mg: 0.8-
1.5%, Mn: 0.30 to 0.50% and Cu: 0.05
~ 0.80% as an essential component, further Fe: 0.7
% Or less, Si: 0.4% or less, Zn: 0.5% or less, Cr:
An aluminum alloy ingot containing one or two or more of 0.05% or less and Ti: 0.05% or less, and the balance being Al and impurities, is subjected to a homogenizing heat treatment at 500 to 600 ° C., and 270 After hot rolling at ~ 600 ° C, intermediate rolling and intermediate annealing at 350 ~ 550 ° C are performed to obtain a diameter of 5
A structure having an intermetallic compound of × 10 ² to 1 × 10 ⁴ Å in a volume fraction of 0.5 to 3%, and then a cold rolling ratio of 40 to
A method for producing an aluminum alloy for drawing having high strength and low directionality, which comprises performing 70% finish cold rolling.