JP2002249841A - Aluminum alloy plate for spinning process, and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy plate having excellent spinning workability and smooth surface after working and suitable for products, e.g. of a cylindrical, cup-like or bowl-like shape such as wheel rim of automobile, parabolic antenna, panelboard, pots and kettles, and also to provide a desirable method for manufacturing the alloy plate. SOLUTION: In the aluminum-alloy plate for spinning, the thickness of the aluminum-alloy plate is 5-10 mm and the size of recrystallized grains in the position at a depth of 0.5 mm from the surface of the alloy plate is made to <=50 μm by circle-equivalent average value and also the size of recrystallized grains in the central part is made to >=70 μm by circle-equivalent average value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is excellent in spinning processability for obtaining cylindrical, cup-shaped or bowl-shaped products such as wheel rims, parabolic antennas, head plates, pot pots and the like for automobiles and the like, and the surface after processing. The present invention relates to a smooth aluminum alloy plate and a preferable method for producing the alloy plate.

[0002]

2. Description of the Related Art As shown in FIG. 1, a spinning process such as a cylindrical shape, a cup shape or a bowl shape is performed by pressing a rolled plate 3 as a material to be processed into a forming die 1 having a predetermined shape which rotates around an axis. The roll 2 is pressed down and moved along the axial direction of the forming die 1 to form the rolled plate 3 as a workpiece into a desired shape. The molding die 1 in this case
An example of a typical rim shape is as shown in the sectional view of FIG.

[0003] Incidentally, the above-mentioned spinning process is established mainly on the forming die 1 as shown in FIG. 1, and can be processed without preparing any extra large equipment. Most of the above-mentioned products are manufactured by spinning an aluminum alloy rolled plate because the plastically processed product has high toughness and can reduce the thickness of the molded product to reduce the weight. The thick plate for spinning is manufactured by cold rolling and then recrystallized in order to make the entire thick plate into a uniform fine structure from the viewpoint of a work material.

[0004]

If the recrystallized grains of the thick plate are made finer to smooth the skin of the spinned product, the yield strength of the thick plate is increased and the spinning workability is reduced. Further, if the recrystallized grains are coarsened to improve the spinning workability and the proof stress of the plate is reduced, the skin of the spinned product becomes rough. That is, the present invention solves the above-mentioned drawbacks of the conventional materials, and proposes a spinning-processable thick plate having a smooth surface of a spinned product and having characteristics of low proof stress and a method of manufacturing the same. It is.

[0005]

Means for Solving the Problems The inventors have found that if the surface layer of a spinning thick plate is made of fine recrystallized grains and the inside is made of coarse recrystallized grains, the surface of the spinned product will be smooth and spinning-free. The present invention has been completed on the assumption that a thick plate having good workability can be obtained.

That is, in the first invention of the present invention, the aluminum alloy plate has a thickness of 5 to 10 mm, and the recrystallized grain size at a depth of 0.5 mm from the surface of the aluminum alloy plate has an average circle equivalent diameter. An aluminum alloy thick plate for spinning, characterized in that the thickness is not more than 50 μm, and the recrystallized grain size at the center is not less than 70 μm in terms of the average equivalent circle diameter. By using a thick plate having such a structure, the surface of the spinned product has a smooth surface and a property of low proof stress coexists, and has an effect of good spinning processability. More preferably, the composition of the aluminum alloy plate is 2.0 to 3.4% by weight of Mg, 0.05 to 0.10% by weight of Cu, and the total amount of Si and Fe as in the second invention. 0.05 to 0.09% by weight, the cast structure refining agent is 0.005 to 0.2% by weight, and the balance is Al and inevitable impurities.
By setting each of n, Cr and Zr to 0.01% by weight or less, in addition to the above effects, a thick plate conforming to an actual product can be obtained.

In a third aspect of the present invention, an aluminum alloy ingot having the above composition is homogenized, and then the ingot is hot-rolled in a plurality of passes. And a work roll exit side plate thickness of 5 to 10 mm, and re-crystallizing the hot-rolled plate by the self-heating of the plate. Since there are few elements that form recrystallization nuclei such as Si and Fe, by adopting such a manufacturing method, the above-described recrystallized grain size can be performed by the self-heating of the sheet after hot rolling, and the thickness can be increased. A thick plate having a recrystallized grain size of 50 μm or less on average in the surface layer portion of the plate and an average recrystallized grain size of 70 μm or more on the center can be easily obtained. Here, the upper limit of the rolling reduction in the final pass of hot rolling is 55%.
It is about. Above this, the recrystallized grain size at the center of the plate becomes smaller. Further, when the hot-rolled alloy thick plate recrystallized by self-heating as in the fourth invention is heated again to the recrystallization temperature, an incomplete recrystallization portion such as the beginning of winding of a coil of the plate can be recrystallized. The entire mechanical properties can be made uniform.

The spinning process described above is a processing method in which the thick plate is shaped into a mold surface using a roll jig in a state where the thick plate and the mold are rotating together, as described above. On the other hand, the crystal grains in the surface layer of the thick plate have the appearance of a processed product in a stretched state. If the grain size of the surface layer portion of the thick plate is small, it is small even if it is elongated, and the smoothness is not impaired. The crystal grain size of the surface layer portion of the thick plate before processing that does not impair the smoothness is about 50 μm or less in terms of the equivalent circle diameter. Further, if the size is small, it is good. However, when the entire thick plate has a small crystal grain size, the yield strength increases as known by the Hall-Petch law, and the spinning speed is reduced, thereby lowering productivity. Therefore, as in the present invention, the surface layer of the thick plate has a small recrystallized grain size, and the central portion has a coarse recrystallized grain size.

[0009] Since the above-mentioned spinning process affects the surface properties of the processed product by about 0.5 mm, the thickness of the surface layer may be in the range of 0.5 mm as long as the crystal grain size is small. . On the other hand, the center part has a coarse recrystallized grain size,
The proof stress of that part is reduced, and the workability as a whole is improved. When the crystal grain size at the center is not less than about 70 μm in terms of the equivalent circle diameter, the overall proof stress is reduced and spinning workability is improved. The crystal grain size gradually increases from the surface layer to the center. The thickness of the central portion may be in the range of 2 mm as long as it has a coarse crystal grain size. Here, the average value of the crystal grain size of the circle-equivalent diameter refers to the average circle-equivalent diameter per recrystallized grain calculated from the number of recrystallizations in a unit visual field.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION A specific embodiment of the present invention as described above will be described. First, a preferred composition of a thick plate according to the present invention will be described as follows. Mg: 2.0 to 3.4% by weight, and Cu: 0.05
To 0.10% by weight. Mg and Cu are for imparting strength to a non-heat-treated type processed product. If the value is less than the lower limit, the strength of the actual product is insufficient, and if the value exceeds the upper limit, work hardening is large and the spinning speed is reduced. In addition, these elements are solid-solution type elements, and if the content is at this level, it is difficult to form an intermetallic compound in combination with the regulation of the content of other elements, and it is difficult to form a nucleus for recrystallization.

The total amount of Si and Fe is 0.05 to 0.09% by weight. Si and Fe form one or two of Al-Fe-based compounds and Al-Si-Fe-based compounds, and serve as nuclei for recrystallization. Below the lower limit, the number of recrystallization nuclei is small, making it difficult to refine recrystallized grains in the surface layer of the thick plate. If the upper limit is exceeded, the recrystallized grains at the center of the thick plate will also be refined. Si and Fe
May be added, or may be contained by adjusting the return material.

[0012] 0.005 to 0.2% by weight of a casting structure refining agent
use. The cast structure refining agent is added to prevent casting cracks. If the amount is less than the lower limit, the effect is small, and if the amount exceeds the upper limit, the effect is saturated and it is not economical. Examples of the cast structure refining agent include Ti alone and a combination of Ti and B.
In the case of Ti alone, Ti: 0.005 to 0.2% by weight, and in the case of combined use of Ti and B, Ti: 0.005 to 0.2% by weight and B: 0.00%.
What is necessary is just to make 005-0.2 weight% contain in an aluminum alloy molten metal.

Mn, Cr and Zr are each made 0.01% by weight or less. Aluminum contains a large number of elements coming from smelting and return materials, and among them, the elements that are high in content and whose compounds tend to be nuclei of recrystallized grains are selected from raw materials, and high-grade ingots and Use return material. That is, when the respective elements of Mn, Cr and Zr exceed the upper limit values, an intermetallic compound is formed, and the center of the thick plate is also undesirably formed as fine recrystallized grains. Other unavoidable impurities are 0.05 each
It is preferable that the content be not more than weight%.

Next, a preferred production method of the present invention will be described as follows. The aluminum alloy ingot having the above composition is homogenized. Although the homogenization treatment is not particularly limited, for example, the heating rate of the ingot is set to 150 ° C.
/ Hour or less, the heating temperature range is 440 to 540 ° C., the holding time is 1 to 24 hours, or the heating temperature range of the ingot is a temperature suitable for the solid solution condition of the contained alloy element, for example, 44
It may be divided into two stages of a low temperature part of 0 to 490 ° C. and a high temperature part of 490 to 540 ° C., and may be heated and held in each temperature region.

The ingot homogenized under the above conditions is hot-rolled in a plurality of passes. In the hot rolling, the rolling reduction of the final pass of the hot rolling is 43% or more, the thickness of the roll exit side plate is 5 to 10 mm, and the hot rolled plate is coiled and recrystallized by self-heating. The reason why the rolling reduction in the final pass of hot rolling is set to 43% or more is that a large work strain is imparted to the surface layer of the thick plate, and the strain is attenuated at the center of the thick plate, resulting in a slight work strain. The thick plate processed in this manner is recrystallized by the heat of the thick plate itself on the roll-roll exit side, or is re-heated again to be recrystallized. By doing so, the recrystallized grains in the surface layer of the thick plate are refined, and Si, Fe, Mn, Cr and
Recrystallization grains in the center of the thick plate are coarsened due to the fact that a small number of elements forming a compound serving as a nucleus for recrystallization such as Zr are combined with a slight processing strain at the center. Roll exit side plate thickness is 5
The reason why the thickness is set to 10 mm is that if the thickness of the plate is small, a large processing strain propagates to the center, and the recrystallized grains become finer as in the surface layer of the thick plate. The upper limit of the thickness is a value as an actual spinning plate. If the temperature of the hot-rolled thick plate is 320 ° C. or higher, recrystallization of equiaxed crystals can be obtained. The upper limit is about 380 ° C. If the temperature is exceeded, the growth of recrystallized grains tends to occur.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention as described above will be described as follows.

EXAMPLE 1 The composition of the alloy specifically adopted by the present inventors is as shown in Table 1 below.

[0017]

[Table 1]

The alloy codes 1-A and 1-
An aluminum alloy having the composition shown in B was melted and semi-continuously cast to cast a slab ingot having a thickness of about 500 mm. The surface of the ingot was heated at a rate of 120 ° C./hour after removing the surface of 15 mm in thickness, and kept at 500 ± 10 ° C. for 12 hours for homogenization. Hot rolling is performed in 7 passes, and the plate thickness after 6 passes is 9.4.
mm, 14.5 mm and 17.5 mm, and were rolled to 8 mm in the final hot rolling in the seventh pass and coiled. The rolling reduction was 15%, 45%, 54%, and the roll exit side plate temperature was 340 ° C.

After completion of the recrystallization by self-heating, the mechanical properties and the size of crystal grains 0.5 mm below and at the center of the surface of the thick plate at room temperature were measured. The measurement surface is a cross section in the thickness direction in the rolling direction. The measurement method is 0 using the image analyzer.
This is the average value of the circle equivalent diameter calculated from the number of recrystallized grains in 28 mm ² . The measurement results are as shown in Table 2 below.

[0020]

[Table 2]

The following Table 3 shows the mechanical properties of the 45% reduction plate in the above-described embodiment after hot rolling and recrystallization by self-heating.

[0022]

[Table 3]

From the results shown in Table 2 above, at a rolling reduction of 15%, there is no remarkable difference in the size of recrystallized grains between the surface portion and the central portion, and the recrystallized size of the surface portion is large. 45
% And 54%, a remarkable difference is seen, and the recrystallized size of the surface layer is small.

As a comparative example, a hot-rolled plate having a thickness of 12.3 mm obtained in the same manner as described above was cold-rolled into a cold-rolled plate having a thickness of 8 mm. Then, the mixture was heated to a temperature of 340 ° C. and kept for 1 hour to recrystallize. The mechanical properties and the circle equivalent diameter of the recrystallized grains were measured. The measurement conditions are the same as in the example,
Such results are shown in Table 4 below.

[0025]

[Table 4]

According to the results of Table 4 as described above,
In the thick plate cold rolled and recrystallized at a rolling reduction of 35%, there is no large difference in the size of recrystallized grains between the surface layer portion and the central portion.
Moreover, the recrystallized size of the surface layer is large.

[0027]

EXAMPLE 2 Spinning workability was compared under the following conditions using the recrystallized sheet after hot rolling at 45% in the inventive example of Example 1 and the recrystallized sheet after 25% cold rolling of the comparative example. did. That is, using the apparatus as shown in FIG. 1 described above, the above plate forming die was pressed by a plate press. Mold size: 250mmφ Plate size: 8mm x 350mmφ Mold rotation speed: 300rpm Roll feed rate: 600mm / min Interval between roll and mold: 7mm No lubrication oil

After the completion of the working, the surface of the plate was visually observed, and the result of visually judging the occurrence of cracks and the presence or absence of skin roughness is shown in Table 5 below.

[0029]

[Table 5]

That is, the spinning thick plate of the present invention as described above has the effect of producing excellent processed products with good productivity because the skin is smooth and the spinning workability is good. Since the method for producing a thick plate for spinning according to the present invention is recrystallized by self-heating after hot rolling, it is also apparent that it has an energy saving effect.

[0031]

According to the present invention as described above, the spinning processability for obtaining various products such as wheel rims for vehicles, parabolic antennas, head plates, pots, and other cylindrical or cup-shaped or bowl-shaped products can be obtained. It is evident that an excellent and smooth aluminum alloy plate having excellent surface properties after processing and a preferable production of the alloy plate can be obtained, and it is clear that the invention is industrially effective.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view showing a state of spinning processing.

FIG. 2 is a cross-sectional view of an example of a wheel mold as the mold in FIG.

FIG. 3 is an explanatory diagram of a recrystallized grain measurement position in the present invention.

[Explanation of symbols]

 1 Forming die that rotates around an axis 2 Roll that moves the forming die in the lateral direction 3 Plate as work piece 4 Plate holder 5 Recrystallized grain size measurement position 6 Central part 7 Plate thickness direction

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[Procedure amendment]

[Submission date] March 1, 2001 (2001.3.1)

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Fig. 1

[Correction method] Change

[Correction contents]

FIG.

Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C22F 1/00 623 C22F 1/00 623 630 630K 682 682 683 683 684 684C 694 694Z 694A (72) Inventor Yasushi Tajima Aichi 1-11-1 Koike, Inazawa-shi Nippon Light Metal Co., Ltd. Nagoya Plant (72) Inventor Yuichi Tamaki 1-11-1 Koike, Inazawa-shi, Aichi Prefecture Nippon Light Metal Co., Ltd. Nagoya Plant (72) Inventor Shinobu Takahashi 1-1-11 Koike, Inazawa, Aichi Prefecture Nippon Light Metal Co., Ltd. Nagoya Plant

Claims (4)

[Claims] 1. A thickness of the aluminum alloy plate 5~10mm
Wherein the recrystallized grain size at a depth of 0.5 mm from the surface of the alloy plate is 50 μm or less in terms of the average equivalent circle diameter, and the recrystallized grain size in the center is 70 μm or more in terms of the average equivalent circle diameter. An aluminum alloy plate for spinning, characterized in that: 2. The composition of an aluminum alloy plate having a Mg content of 2.
0 to 3.4% by weight, 0.05 to 0.10% by weight of Cu, 0.05 to 0.09% by weight of the total amount of Si and Fe, and 0.
005 to 0.2% by weight, with the balance being Al and inevitable impurities, of which Mn, Cr and Zr
2 is 0.01% by weight or less, respectively. 3. Mg is 2.0 to 3.4% by weight, and Cu is 0.05 to 0.5% by weight.
10% by weight, the total amount of Si and Fe is 0.05 to 0.09% by weight,
The cast structure refining agent is 0.005 to 0.2% by weight, the balance being Al and inevitable impurities, and among the inevitable impurities, Mn,
When an aluminum alloy ingot in which Cr and Zr are each controlled to 0.01% by weight or less is homogenized, and then the ingot is hot-rolled in a plurality of passes, the rolling reduction in the final pass of hot rolling is 43%. As described above, the work roll exit side plate thickness is 5 to 1
A method for producing an aluminum alloy thick plate for spinning, wherein the thickness is set to 0 mm and the hot-rolled plate is recrystallized by the self-heating of the plate. 4. The method for producing an aluminum alloy thick plate for spinning according to claim 3, wherein the hot-rolled sheet recrystallized by self-heating of the sheet is recrystallized again.