JPH07252611A - Aluminum-manganese-magnesium alloy sheet for forming - Google Patents

Abstract

PURPOSE:To provide superior deep drawability and baking finish hardenability by subjecting an Al alloy of specific composition to continuous casting and direct rolling and then to cold rolling and controlling the maximum length and volume fraction of insoluble compounds in the resulting rolled sheet, respectively. CONSTITUTION:The Al alloy has a composition consisting of, by weight ratio, 0.5-<1.0% Mn, 0.3-<0.6% Mg, and the balance Al with inevitable impurities. After this Al alloy is cast continuously, the resulting cast slab is subjected, without cooling, to holding at a temp. not lower than hot rolling temp., followed by rolling. The resulting plate is cold-rolled to prescribed thickness. At this time, the maximum length and volume fraction of insoluble compound grains existing in the sheet are controlled to <=2mum and <=2.0%, respectively. Moreover, if necessary, one or >=2 kinds selected from 0.3-1.0% Cu, 0.1-1.0% Fe, 0.3-0.5% Si, 0.3% Cr, 0.3% Zr, and 0.5% Zn are further added to the alloy composition.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to Al-Mn for molding.
-Mg-based alloy sheet, and particularly to an Al-Mn-Mg-based alloy sheet for forming, which exhibits excellent deep drawability and is also excellent in bake coating hardenability.
The Al-Mn-Mg alloy plate for forming according to the present invention can be utilized for various forming applications including drinking and eating can materials by taking advantage of its excellent characteristics.

[0002]

2. Description of the Related Art Conventionally, as a method for producing an aluminum alloy plate for forming and used for, for example, food cans and beverage cans, it has been generally practiced to use an ingot produced by a semi-continuous casting method or the like. This is a method of sequentially performing hot rolling, cold rolling, annealing, etc. after subjecting to a faceting treatment or a homogenizing heat treatment, and the conventional Al alloy plate for forming having such a process has a good formability. In addition to being good, it also possessed some strength, and satisfied the demands of consumers for the time being.

However, in recent years, the demands of consumers have become more severe, and in particular, there has been a demand for a thinner product of deep-drawn products. In order to cope with such a tendency toward thinning, it is considered effective to further improve the deep drawability and achieve excellent baking coating curability.

On the other hand, as a relatively new Al alloy plate manufacturing technique, a method of sending to a rolling step immediately after continuous casting to carry out hot rolling and cold rolling (hereinafter sometimes referred to as continuous casting / direct feed rolling method) is adopted. However, a method of omitting the chamfering and homogenizing heat treatment has been studied (for example, JP-A-55-274).
97, Japanese Patent Publication No. 62-54182, etc.). According to this method, cost reduction can be achieved by omitting the chamfering and homogenization heat treatment, and the solid solution elements that are supersaturated in the casting process do not precipitate during homogenization heat treatment. It is possible to obtain the advantage that the high strength due to is also enhanced.

[0005]

SUMMARY OF THE INVENTION The present invention has been made under these circumstances, and an object thereof is to exhibit an excellent deep drawing property and an Al for molding process which is excellent in baking coating curing property. An object is to provide an —Mn—Mg-based alloy plate.

[0006]

The Al alloy plate of the present invention which achieves the above objects, Mn: 0.5 to less than 1.0% by weight, Mg: 0.3 to less than 0.8% by weight, respectively. An Al-Mg-based alloy containing the balance Al and unavoidable impurities is hot-rolled while maintaining the slab temperature at or above the hot-rolling temperature after continuous casting, and then cold-rolled to a predetermined plate thickness. And the maximum length of the insoluble compound particles is 2 μm or less, and the volume fraction thereof is suppressed to 2.0% or less.

[0007]

The present inventors examined the conditions from various angles in order to realize the Al alloy plate as described above. As a result, Al whose contents and ratios are strictly adjusted
-Mn-Mg-based alloy (hereinafter sometimes simply referred to as Al alloy) was manufactured by applying the above continuous casting / direct feed rolling method, and the maximum length and volume of insoluble compound particles If the rate is adjusted appropriately, the desired Al
The present invention has been completed by finding that an alloy plate can be obtained. First, the reasons for limiting the component range of the Al alloy plate used in the present invention are as follows.

Mn: 0.5 to less than 1.0% by weight Mn is an element effective for improving the strength by solid solution strengthening, improving the baking coating curability by precipitation hardening, and the like. According to a study made by the present inventors, since Mn is dissolved in supersaturation by applying the continuous casting / direct feed rolling method, the amount of Mn added in the case of applying the conventional process (JIS standard: 1.0 to It has been found that smaller amounts are better than 1.5% by weight). That is, in the Al alloy of the present invention, when the content of Mn is less than 0.5% by weight, the effect is not exhibited and 1.0
If it is more than weight%, the ironing workability deteriorates. The more preferable content of Mn is 0.6 to 0.9% by weight, and more preferably 0.7 to 0.8% by weight.

Mg: 0.3 to Less than 0.8% by Weight Like Mn, Mg is an element effective for improving strength by solid solution strengthening, and improving hardenability of baking coating by precipitation hardening. According to a study conducted by the present inventors, since Mg is dissolved in supersaturation by applying the continuous casting / direct rolling method, the amount of Mg added (J
It has been found that a smaller amount is better than the IS standard of 0.8 to 1.3% by weight. That is, in the Al alloy of the present invention,
If the content of Mg is less than 0.3% by weight, the effect is not exhibited, and if it is 0.8% by weight or more, the ironing workability deteriorates. The more preferable content of Mg is 0.4 to 0.7% by weight, and more preferably 0.5 to 0.6% by weight.

The Al alloys used in the present invention are Mn and M.
g as a basic component and the balance Al and unavoidable impurities, but if necessary Cu, Fe, Si, C
A predetermined amount of elements such as r, Zr and Zn may be contained. The reasons for limiting the component ranges when these elements are contained are as follows.

Cu: 0.3-1.0 wt% Cu interacts with Mg to form Al-Cu during baking coating.
— An element effective in promoting the formation of Mg-based fine precipitates and promoting hardening. According to the continuous casting and direct rolling method, C
Since u can be supersaturated to form a solid solution, the amount of Cu added in the conventional process (0.25 wt% according to JIS standard)
It can be added in a larger amount than that of (degree) and can greatly improve the baking coating curability. In order to exert such an effect, it is necessary to contain 0.3% by weight or more, but if the content exceeds 1.0% by weight, the ear rate becomes poor and the corrosion resistance also deteriorates. The preferable Cu content is about 0.5 to 0.8% by weight.

Fe: 0.1-0.8 wt% Fe is an element effective in preventing rough skin and improving ironing workability by reacting with Mn to form Al-Mn-Fe system precipitates. . In order to exert such an effect, it is necessary to contain 0.1% by weight, but if it is added in excess of 0.8% by weight, the insoluble compound becomes enormous during casting and workability is greatly deteriorated. The more preferable content of Fe is about 0.3 to 0.6% by weight.

Si: 0.3 to 0.6 wt% Si is an element effective for promoting hardening by interacting with Mg to form Mg ₂ Si-based fine precipitates. The Al alloy of the present invention is manufactured by a continuous casting / direct feed rolling method, and Si can be supersaturated to form a solid solution. Therefore, the addition amount in the conventional process (JIS standard: 0.
(About 3% by weight), and the curability of baking coating can be greatly improved. In order to exert such an effect, it is necessary to contain 0.3% by weight or more. However, even if it is excessively contained in excess of 0.6% by weight, it precipitates as Si simple substance and the formability rather deteriorates. The more preferable content of Si is about 0.4 to 0.5% by weight.

One or more elements selected from the group consisting of Cr: 0.3% by weight or less, Zr: 0.3% by weight or less and Zn: 0.3% by weight or less (all do not contain 0% by weight). These elements are effective for preventing rough skin, but if added in excess, the insoluble compound becomes enormous and the workability deteriorates. Therefore, 0.3% by weight or less of Cr and Zr, Zn needs to be 0.5% by weight or less.

The elements contained as necessary must be added at least at the above lower limit values or more in order to exert their effects. However, in the Al alloy plate of the present invention, the above elements are It is not excluded that the Al alloy plate is contained below the lower limit, and such an Al alloy plate is also included in the technical scope of the present invention.

The Al alloy sheet of the present invention is basically assumed to be produced by the continuous casting / direct feed rolling method. By performing continuous casting in this manner, crystals of an insoluble compound are obtained. The effect of making the product finer and improving the press moldability is exhibited. Further, the continuous casting also exerts an effect that Mn, Mg, and Cu and Si that are added if necessary are solid-soluted in a supersaturated state, and the curing property of the baking coating is greatly improved. However, the effect as described above is not limited to the case of applying the continuous casting / direct feed rolling method such that hot rolling is performed immediately as a moving strip by continuous casting, and a continuously cast slab is finally obtained. To be higher than the hot rolling temperature (including the case of once lower than the hot rolling temperature)
It is exhibited even when adjusted and hot-rolled. In short, hot-rolling may be performed "holding the slab temperature after continuous casting at or above hot-rolling".

The continuous casting method applied when producing the Al alloy sheet of the present invention is not particularly limited, and any one of the following methods (1) to (4) can be used. Can be adopted. (1) A water-cooled continuous casting method in which a continuous cast piece that is molded into a plate shape from a fixed water-cooled continuous casting mold is directly water-cooled and solidified with cooling water and continuously cast. (2) A twin roll casting method in which a molten metal is supplied between a pair of rotating water-cooled rolls, the rolls are cooled and solidified, and continuously cast into a plate. (3) A belt-type continuous casting method in which a molten metal is supplied between two movable belt-shaped cooling members to cool and solidify between the belts and continuously cast into a plate. (4) A block-type continuous casting method in which a molten metal is supplied between two movable block-shaped cooling members to be cooled and solidified between the blocks and continuously cast into a plate.

By the way, the insoluble compound in the present invention is a compound which crystallizes when Fe, Si, Cr or the like is excessively contained, and it does not form a solid solution in the alloy even if the treatment temperature is raised, and it is in the form of particles. In the present invention, the maximum length of the insoluble compound particles is 2 μm or less, and it is necessary to suppress the volume fraction thereof to 2.0% or less. That is, in the Al alloy plate of the present invention,
When the maximum length of the insoluble compound particles exceeds 2 μm or the volume fraction thereof exceeds 2.0%, the moldability is greatly deteriorated,
The object of the present invention is not achieved. The maximum length of the insoluble compound particles is preferably 1.5 μm or less, more preferably 1.0 μm or less, from the viewpoint of moldability. The volume fraction of the insoluble compound is preferably 1.2% or less,
1.0% or less is more preferable.

The maximum length of the insoluble compound particles is, for example, a maximum diameter when a cut surface is formed so as to give a maximum diameter in the case of spherical or disc-shaped crystals, and is a substantially cubic or substantially rectangular parallelepiped crystal. If there is a crystal with an unspecified shape, it means the length of the longest diagonal, if any, and the length between two points on the most distant surface. When measuring the maximum length of the insoluble compound particles, it may be calculated from the microscope field using an electron microscope.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples, and any modification of the design can be made according to the gist of the preceding and the following. It is included in the target range.

[0021]

Examples Al-Mn-Mg having the chemical composition shown in Table 1
A series alloy was produced by a thin plate continuous casting method to obtain a 20 mm moving strip. However, No. 1 in Table 1 20 things are
It is a JIS alloy manufactured by a usual method. Immediately after casting, these moving strips were hot-rolled into a plate material having a thickness of 2 mm. At this time, the starting temperature of the hot rolling was 450 ° C and the ending temperature was 350 ° C. Then, cold rolling was performed to a thickness of 0.8 mm, heat treatment was performed at 530 ° C. for 30 seconds using a salt bath furnace, and further cold rolling was performed to a thickness of 0.3 mm.

[0022]

[Table 1]

With respect to the finished sheet material, the ironing workability was investigated, and the baking coating hardenability was examined by the yield strength after heat treatment at 200 ° C. for 30 minutes. The insoluble compound particles were observed with a scanning electron microscope, and the maximum length and volume fraction thereof were evaluated by image processing. The results are shown in Table 2. The ironing workability indicates a success rate (%) at an ironing rate of 70%, and a value of more than 60% means that the ironing workability is good.

[0024]

[Table 2]

As is clear from Table 2, the material of the present invention satisfying the requirements specified in the present invention has higher ironing workability and baking coating hardening property than the conventional material (JIS alloy), and deep drawing. It can sufficiently cope with thinning of processed products. On the other hand, comparative examples manufactured by continuous casting but not satisfying other requirements specified in the present invention (Nos. 7 to 19) have at least ironing workability or baking coating curability. It can be seen that either of them is bad and it cannot be applied to the thinning of deep drawn products.

[0026]

The present invention is constituted as described above, and an Al-Mn-Mg alloy plate for forming which is excellent in both deep drawing workability and baking coating hardenability was obtained.

Claims (5)

[Claims] 1. Mn: 0.5 to less than 1.0% by weight, M
g: 0.3-0.8% by weight, respectively, balance Al
And an Al-Mn-Mg-based alloy consisting of inevitable impurities are hot-rolled by maintaining the slab temperature after hot casting at a hot rolling temperature or higher, and then cold rolling to a predetermined plate thickness, In addition, the maximum length of the insoluble compound particles is 2 μm or less, and the volume fraction thereof is suppressed to 2.0% or less.
Mg-based alloy plate. 2. The Al—Mn—Mg based alloy plate according to claim 1, which further contains Cu: 0.3 to 1.0 wt%. 3. The Al-Mn according to claim 1 or 2, further comprising Fe: 0.1 to 0.8% by weight.
-Mg-based alloy plate. 4. The Al according to claim 1, further comprising Si: 0.3 to 0.6% by weight.
-Mn-Mg based alloy plate. 5. Further, Cr: 0.3% by weight or less (not including 0% by weight), Zr: 0.3% by weight or less (not including 0% by weight) and Zn: 0.5% by weight or less ( Al-Mn according to any one of claims 1 to 4, which contains one or more kinds selected from the group consisting of (excluding 0% by weight).
-Mg-based alloy plate.