JPH0717991B2 - Al-Mg based alloy that does not generate stretcher strain marks during forming and method for producing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an Al—Mg alloy, and more specifically, an Al—Mg alloy for forming which is mainly intended for deep drawing and a method for producing the same. Regarding

(Prior art and problems to be solved) Aluminum materials are mainly used for drawn cans (DR cans) such as food cans, and they are manufactured by deep drawing after hot rolling, cold rolling, etc. .

Such aluminum materials for food cans are required to have the following material characteristics.

Strength Formability Low directionality Surface quality, especially no SS mark (stretcher / strain mark) Corrosion resistance Adhesion of coating film From the above viewpoint, in Japan, 5052 alloy based on Al-2.5% Mg has been conventionally used. In the United States, the Al-3.5Mg-based 5042 alloy was mainly used.

However, recently, with the adoption of deep-drawing cans with a drawing ratio close to about 2.0 for food cans, B type SS mark (parallel band)
Occurs on the body of the can, and not only the aesthetic appearance but also the damage to the coating film applied to the inner surface of the can to protect the contents.

For this B type SS mark, see, for example, "Basics and Industrial Technology of Aluminum Materials" published by The Light Metals Association of Japan (1985), p.140. Difficult to prevent, increase processing speed,
It is necessary to change the deformation conditions, such as adjusting the strain conditions. ", A preventive measure from the deformation conditions (processing conditions) was mentioned. Certainly, in simple processing such as tensile deformation, speeding up the deformation speed and low temperature deformation are effective, but in the actual forming of can material, it is difficult to increase the press working speed and control the temperature. There has been a long-standing demand for improvement in terms of aspects.

The present invention has been made to meet the above requirements, provides an Al-Mg alloy that does not generate stretcher strain marks during molding, and industrially manufactures such an Al-Mg alloy. The purpose is to provide a possible method.

(Means for Solving the Problem) In order to achieve the above-mentioned object, the inventors of the present invention frequently use aluminum alloys for food cans, and 5052 alloys (2.5% Mg), which are expected to be used in the future, 5042 alloys ( For 3.5% Mg), in order to find a material that does not generate SS mark, we will take measures to prevent SS mark from the material side, consider strength, etc. Overlaid.

As a result, by rolling the Al-Mg-based alloy under specific conditions and subjecting it to heat treatment to control the degree of softening along with the grain size,
We have found that the SS mark can be effectively prevented.

That is, the present invention is an Al-Mg based alloy containing 1.5 to 4 wt% of Mg, having a grain size of 10 to 40 μm, and having a softening degree defined by the following equation, a softening degree = (σy ⁰ − σy) × 100 ÷ σy ⁰ (%) (where σy ⁰ : yield strength of material before stabilization annealing σy: yield strength of material after stabilization annealing is 10% or more The gist is an Al-Mg-based alloy that does not generate letcher strain marks.

Further, the present invention according to the manufacturing method thereof, after hot rolling the ingot of Al-Mg based alloy containing 1.5 to 4 wt% Mg, intermediate rolling with a working rate of 40% or more, the temperature of 300 ~ 500 ℃. Intermediate annealing is performed, and further finish rolling with a working rate of 40% or more is performed.
A gist of the present invention is to provide a method for producing an Al-Mg-based alloy that does not generate stretcher strain marks during forming, which is characterized by performing stabilizing annealing at a temperature of up to 250 ° C.

Hereinafter, the present invention will be described in more detail.

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

The Al alloy targeted by the present invention contains 1.5 to 4 wt% of Mg.
It is an Al-Mg based alloy. Since the strength of this system alloy is determined by the amount of Mg and the translocation introduced by cold working, it is necessary to use a predetermined amount of Mg as an essential component. That is, the amount of Mg is 1.
If it is less than 5 wt%, the proof that the yield strength is 20 kgf / mm ² or more cannot be achieved. Further, when Mg exceeds 4 wt%, sufficient strength is obtained, but press workability is deteriorated. Therefore, the amount of Mg is
The range is 1.5 to 4 wt%.

As for other components, 5052 alloy, 5042 alloy and other Al-
An element contained in the Mg-based alloy can be contained in an appropriate amount as necessary. For example, a transition element such as Cr (5052 alloy) or Mn (5042 alloy) may be contained for controlling the structure.

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

The Al—Mg based alloy adjusted to the desired composition as described above is usually ingot-cast by the DC casting method, subjected to homogenizing heat treatment, and then hot rolled. The homogenization heat treatment is preferably performed at a temperature of 500 to 550 ° C. Further, hot rolling is preferably performed at a temperature of 300 to 550 ° C. After the hot rolling, intermediate annealing may be performed. When the intermediate annealing is performed, the control of the material structure becomes easier.

Then, intermediate rolling (cold rolling) with a working rate of 40% or more is performed. When the rolling rate is less than 40%, the final grain size is 40μ.
m is larger than m, the surface becomes rough during the molding process, and the surface quality is deteriorated, which is not preferable.

After that, intermediate annealing is performed, but recrystallization does not occur below 300 ° C, and there is a risk of coarsening of the crystal grains and burning above 550 ° C. Therefore, the temperature is in the range of 300 to 550 ° C. In addition, this heat treatment is 300 to 3 in a batch type furnace.
50 ℃ x 2hr is enough, and in continuous heating furnace (CAL)
500 to 550 ° C x 1 to 10 seconds is sufficient.

Subsequent final finish rolling (cold rolling) is performed at a working rate of 40% or more. If the processing rate is less than 40%, sufficient strength cannot be obtained.

Finally, stabilization annealing is performed at a temperature of 150 to 250 ° C. In this case, if the temperature is lower than 150 ° C, the internal structure is insufficiently changed, and if the temperature exceeds 250 ° C, softening proceeds and sufficient strength cannot be obtained.

In the Al-Mg based alloy obtained by the above method, when the grain size exceeds 40 μm, roughening occurs during drawing,
If it is less than m, the movement of dislocations during processing becomes slow, and SS marks are likely to occur. Therefore, the grain size is 10-40μ
It is preferable to adjust to the range of m.

Further, in the present invention, the softening degree defined by the following formula is regulated.

Softening degree = (σy ⁰ −σy) × 100 ÷ σy ⁰ (%) (where, σy ⁰ : yield strength of material before stabilizing annealing σy: yield strength of material after stabilizing annealing, that is, the softening degree is 10% The above is to be considered as a guideline for industrial stabilization annealing.
There are many dislocations that cause marks and SS marks are easily generated, which is not preferable. In addition, the amount of solid solution Mg is also changed by performing the stabilizing annealing, and it seems that it is in a stable existence state, and it has the effect of making it difficult to cause a dynamic reaction with dislocations. Is preferably applied.

The Al-Mg-based alloy thus obtained is subjected to forming processing by a conventional method, but even if it is subjected to deep drawing with a drawing ratio close to about 2.0, SS marks can be prevented.

Next, examples of the present invention will be described.

(Example) An ingot of an Al alloy having a chemical composition shown in Table 1 (thickness: 50 m
m) is faced and subjected to homogenizing heat treatment at 500 ℃ x 8hr, then 3
Hot rolling was performed at 00 to 500 ° C to obtain a hot rolled sheet having a thickness of 2 to 4 mm.

After that, processing and heat treatment under the conditions shown in Table 2
A test material of 0.25 mm was obtained.

With respect to the obtained test materials, the grain size and the softening degree were examined, and the tensile properties, SS marks (parallel band) and rough skin were examined. The results are also shown in Table 2.

The SS mark was evaluated by conducting a 40 mmφ, 50% squeeze cup test, and when there was no occurrence, it was marked with O, and when it occurred, was marked with X.

It can be seen from Table 2 that Examples No. 1 to No. 5 of the present invention have the required strength (> 20 kgf / mm ² ) without any SS mark.

On the other hand, Comparative Examples No. 6 to No. 9 are examples in which the degree of softening is zero because the stabilizing annealing is not performed, and SS marks are generated. Mg
Comparative example No. 10 for Al alloys whose content is outside the scope of the present invention
No. 11 has a small softening degree and SS marks are generated.
Comparative Example No. 12, which has a low intermediate rolling working ratio, has a large crystal grain size, which causes SS marks and rough skin. Comparative Example No. 13 in which both the workability of intermediate rolling and the intermediate annealing temperature are low, the recrystallization is insufficient, the softening degree is small, and S
S mark is generated. Comparative Example No. 14, which has a low intermediate annealing temperature and a low finish rolling rate, did not have the required strength and
The mark is generated. Comparative example N with low stabilization annealing temperature
Comparative Example No. 16 of which the softening degree is small, SS mark is generated, and the stabilization annealing temperature is high cannot be obtained in o.15.

(Effect of the Invention) As described in detail above, according to the present invention, Al-containing a specific composition
By subjecting Mg-based alloy to rolling and heat treatment under specific conditions, the grain size and softening degree are regulated, so stretcher strain marks (parallel band) are used during forming.
It is possible to obtain an aluminum material that does not generate In particular, it is possible to manufacture deep-drawn cans such as food cans without generating stretcher strain marks even in deep-drawing where the drawing ratio is close to 2.0. Further, according to the method of the present invention, industrial production is easy.

Claims (2)

[Claims] 1. An ingot of an Al-Mg based alloy containing 1.5 to 4 wt% of Mg is hot-rolled and then subjected to an intermediate rolling with a working rate of 40% or more.
Stretcher / strain mark during forming, characterized by performing intermediate annealing at a temperature of 0 to 500 ° C, finish rolling at a working rate of 40% or more, and then stabilizing annealing at a temperature of 150 to 250 ° C. A method for producing an Al-Mg-based alloy that does not generate heat. 2. An Al-Mg based alloy containing 1.5 to 4 wt% of Mg, having a grain size of 10 to 40 μm, and having a softening degree defined by the following formula, softening degree = (σy ⁰ −σy ) × 100 ÷ σy ⁰ (%) (where σy ⁰ : yield strength of material before stabilization annealing σy: yield strength of material after stabilization annealing is 10% or more, stretcher during forming process -Al-Mg alloy that does not generate strain marks.