JP2009167533A - Aluminum alloy thick plate for spinning - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum alloy thick plate having excellent spinning workability, and whose surface after working is smooth. <P>SOLUTION: Disclosed is an aluminum alloy thick plate for spinning with a thickness of 5 to 10 mm, in which the size of recrystallized grains from the surface of the alloy plate to a depth position of 0.5 mm is ≤50 μm by the average value in an equivalent circle diameter, and the size of recrystallized grains at the central part is ≥70 μm by the average value in an equivalent circle diameter. The aluminum alloy thick plate has a composition comprising Mg of 2.0 to 3.4 wt.%, Cu of 0.05 to 0.10 wt.%, Si and Fe of 0.05 to 0.09 wt.% in total, a cast structure refining agent of 0.005 to 0.2 wt.%, and the balance Al with inevitable impurities, and in the inevitable impurities, each content of Mn, Cr and Zr is ≤0.01 wt.%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention is an aluminum alloy thick plate that is excellent in spinning workability for obtaining products such as wheel rims, parabolic antennas, end plates, pans and other cylindrical products such as automobiles, cups and bowls, and has a smooth surface after processing. it relates to.

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 rolling plate 3 as a workpiece with a plate presser 4 into a mold 1 having a predetermined shape that rotates about an axis. The rolled plate 3 which is a work material is formed into a desired shape by moving the roll 2 which moves along the axial direction. An example of a typical rim shape as the mold 1 in this case is as shown in a cross-sectional view of FIG.

By the way, the spinning process as described above is mainly performed with the forming die 1 as shown in FIG. 1 and can be processed without preparing a particularly large facility, and the aluminum alloy has good formability and plastic processing from a rolled plate. Since these products have high toughness and the thickness of the compact can be reduced to reduce the weight, many of the products as described above are manufactured by spinning aluminum alloy rolled plates. In addition, the thick plate for spinning is manufactured by recrystallization after cold rolling in order to make the entire thick plate into a uniform fine structure from the viewpoint of a processed material.

If the recrystallized grains of the thick plate are refined in order to smooth the skin of the spinning processed product, the proof stress of the thick plate is increased and the spinning workability is lowered. Further, if the recrystallized grains are coarsened to reduce the yield strength of the plate in order to improve the spinning processability, the skin of the spinning processed product becomes rough. That is, the present invention proposes a thick plate with good spinning workability, which solves the above-mentioned drawbacks of the conventional materials and has a smooth surface of a spinning processed product and a low proof stress.

The inventors obtained a thick plate with a smooth surface and a good spinning workability if the surface layer of the spinning plate is a fine recrystallized grain and the inside is a coarse recrystallized grain. As a result, the present invention has been completed.

That is, according to the present invention, the thickness of the aluminum alloy plate is 5 to 10 mm, and 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 equivalent circle diameter average value. aluminum alloy thick plate der for spinning, wherein the recrystallized grain size is 70μm or more in circle-equivalent diameter average value is, the composition, Mg is 2.0 to 3.4 wt%, Cu 0. 05 to 0.10% by weight, the total amount of Si and Fe is 0.05 to 0.09% by weight, the cast structure refiner is 0.005 to 0.2% by weight, and the balance is Al and inevitable impurities. In the inevitable impurities, Mn, Cr and Zr are each 0.01% by weight or less . By using a thick plate having such a structure and composition , the surface of the spinning processed product has a smooth surface and low proof stress, and has an effect of good spinning workability .

The spinning process described above is a processing method in which the thick plate and the mold are rotated together and the thick plate is shaped into a mold surface shape using a roll jig. The crystal grains in the surface layer portion become the appearance of the processed product in an extended state. If the crystal grain size of the thick plate surface layer portion is small, it is small even if it is extended, and the smoothness is not impaired. The crystal grain size of the thick plate surface layer part before processing that does not impair the smoothness is about 50 μm or less in terms of the equivalent circle diameter average value. Smaller sizes are better. However, when the whole thick plate has a small crystal grain size, the yield strength increases as is known by the Hall Petch's law, and the spinning speed decreases and productivity decreases. Therefore, as in the present invention, the thick plate surface layer portion has a small recrystallized grain size and the central portion has a coarse recrystallized grain size.

Since it is about 0.5 mm that affects the surface properties of the processed product in the spinning process as described above, the thickness of the surface layer portion may be a small crystal grain size in the range of 0.5 mm. On the other hand, the central portion has a coarse recrystallized grain size, and the yield strength of the portion is lowered to improve the workability as a whole. If the crystal grain size at the center is about 70 μm or more in terms of the equivalent circle diameter average value, the overall proof stress is lowered and the spinning processability is improved. The crystal grain size gradually increases from the surface layer to the center. The thickness of the central portion may be a coarse crystal grain size in the range of 2 mm. Here, the average value of the equivalent circle diameter of the crystal grains means the equivalent circle diameter per average recrystallized grain calculated from the number of recrystallizations in the unit visual field.

According to the present invention as described above, it is excellent in spinning workability to obtain various products such as cylindrical or cup-shaped, bowl-shaped products such as vehicle wheel rims, parabolic antennas, end plates, pots, etc. It is apparent that a smooth aluminum alloy thick plate with excellent surface properties can be obtained, which is an industrially highly effective invention.

It is sectional explanatory drawing which showed the state of the spinning process. It is sectional drawing about one example of a wheel shaping | molding die as a shaping | molding die in what was shown in FIG. It is explanatory drawing about the recrystallized grain measurement position in this invention.

A specific embodiment of the present invention as described above will be described. First , the composition of the thick plate in the present invention will be described as follows. Mg: 2.0 to 3.4 wt% and Cu: 0.05 to 0.10 wt%. Mg and Cu are for imparting strength to a non-heat treated type processed product, and if it is less than the lower limit value, the strength as an actual product is insufficient, and if it exceeds the upper limit value, work hardening is large and spinning processing speed is reduced. In addition, these elements are solid solution type elements, and if they are contained at this level, it is difficult to form an intermetallic compound in combination with restrictions on the contents of other elements, and it is difficult to become a nucleus of recrystallization.

The total amount of Si and Fe is 0.05 to 0.09% by weight. Si and Fe form one or two of an Al—Fe-based compound and an Al—Si—Fe-based compound and serve as a nucleus for recrystallization. If it is less than the lower limit, the number of recrystallized nuclei is small and it becomes difficult to refine the recrystallized grains in the surface layer portion 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.

The cast structure refiner is used in an amount of 0.005 to 0.2% by weight. The cast structure refining agent is added to prevent casting cracks. Less than the lower limit is less effective, and exceeding the upper limit is not economical because the effect is saturated. 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 wt%, in the case of combined use of Ti and B, Ti: 0.005 to 0.2 wt% and B: 0.005 to 0.2 wt% May be contained in the molten aluminum alloy.

Mn, Cr and Zr are each 0.01% by weight or less. Aluminum has many elements that come from smelting and reclaiming materials. Among them, elements that are high in content and whose compounds are likely to become the core of recrystallized grains are selected as raw materials. Use return material. That is, when each element of Mn, Cr, and Zr exceeds the upper limit value, an intermetallic compound is formed, and the central portion of the thick plate becomes fine recrystallized grains, which is not preferable. The other inevitable impurities are preferably 0.05% by weight or less.

Next, a preferable production method of the present invention will be described as follows. The aluminum alloy ingot having the above composition is homogenized. The homogenization treatment is not particularly limited. For example, the heating rate of the ingot is 150 ° C./hour or less, the heating temperature range is 440 to 540 ° C., the holding time is 1 to 24 hours, or the above ingot The heating temperature range may be divided into two stages, a temperature suitable for the solid solution conditions of the contained alloy element, for example, a low temperature part of 440 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 that has been homogenized under the conditions described above is hot-rolled in multiple passes. In hot rolling, the rolling reduction in the final pass of hot rolling is 43% or more, the roll outlet side plate thickness is 5 to 10 mm, and the hot rolled plate is used as a coil for recrystallization by self-heating. The reduction ratio of the final pass of the hot rolling is set to 43% or more because a large processing strain is given to the surface layer portion of the thick plate, and the strain is attenuated at the central portion of the thick plate to become a mild processing strain. The thick plate thus processed is recrystallized by the heat of the thick plate itself on the rolling roll exit side, or reheated again to be recrystallized. By doing so, the recrystallized grains in the surface layer portion of the thick plate are refined, and there are few elements that form a compound that becomes the core of recrystallization such as Si, Fe, Mn, Cr, and Zr, and the mildness of the central portion. Combined with this processing strain, the recrystallized grains at the center of the thick plate become coarse. The roll exit side plate thickness is set to 5 to 10 mm because if the plate thickness is small, a large processing strain propagates to the center, and the recrystallized grains become finer as in the surface layer portion of the plate. . The upper limit value of the plate thickness is a value as an actual spinning plate. If the thick plate temperature after hot rolling is 320 ° C. or more, equiaxed recrystallization can be obtained. The upper limit is about 380 ° C., and if this temperature is exceeded, the growth of recrystallized grains tends to occur.

A specific embodiment of the present invention as described above will be described as follows.

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

Aluminum alloys having the compositions shown in alloy codes 1-A and 1-B in Table 1 were melted and semi-continuously cast to cast a slab ingot having a thickness of about 500 mm. The surface of the ingot was removed at a thickness of 15 mm and heated at a heating rate of 120 ° C./hour and held at 500 ± 10 ° C. for 12 hours for homogenization. The hot rolling was 7 passes, the plate thickness after 6 passes was 9.4 mm, 14.5 mm, and 17.5 mm, and the final hot rolling of the 7th pass was rolled to 8 mm and coiled. The respective rolling reductions were 15%, 45% and 54%, and the roll exit side plate temperature was 340 ° C.

After recrystallization by self-heating, the mechanical properties and the size of the crystal grains 0.5 mm below and in the center of the surface of the plank were measured at room temperature. The measurement surface is a cross section in the thickness direction in the rolling direction. The measurement method is an average value of equivalent circle diameters calculated from the number of recrystallized grains within a measurement visual field of 0.28 mm ² using an image analyzer. The measurement results were as shown in Table 2 below.

Table 3 below shows the mechanical properties of the 45% rolling reduction plate in the above-described example and recrystallized by self-heating after hot rolling.

From the results shown in Table 2 above, when the rolling reduction is 15%, there is no significant difference in the size of recrystallized grains between the surface layer portion and the center portion, and the recrystallization size of the surface layer portion is large. A significant difference is seen at 45% and 54%, and the recrystallized size of the surface layer is small.

As a comparative example, a hot-rolled sheet having a thickness of 12.3 mm obtained in the same manner as described above was cold-rolled into a cold-rolled sheet having a thickness of 8 mm. Subsequently, it was heated to a temperature of 340 ° C. and held for 1 hour for recrystallization. The mechanical properties and the equivalent circle diameter of the recrystallized grains were measured. The measurement conditions are the same as in the examples, but such results are as shown in Table 4 below.

According to the results of Table 4 as described above, in the thick plate cold-rolled and recrystallized at a reduction rate of 35%, there is no significant difference in the size of the recrystallized grains between the surface layer and the center, and the surface layer The recrystallization size of the part is large.

Using the recrystallized plate after 45% hot rolling in the inventive example of Example 1 and the recrystallized plate after 35% cold rolling of the comparative example, spinning workability was compared under the following conditions. That is, using the apparatus as shown in FIG. 1 described above, the above plate forming die was pressed with a plate press.
Mold size: 250mmφ
Plate size: 8mm × 350mmφ
Mold rotation speed: 300rpm
Roll feed measurement: 600 mm / min Distance between roll and mold: 7 mm
Without lubricant

Table 5 below shows the results of visually observing the surface of the plate after completion of processing and visually determining whether cracks occurred and whether the skin was rough.

That is, the spinning plate of the present invention as described above has an effect of producing an excellent processed product with high productivity because the skin is smooth and the spinning processability is good .

As yet another comparative example, a hot-rolled sheet having a thickness of 20 mm obtained in the same manner as in Example 1 was cold-rolled into a cold-rolled sheet having a thickness of 8 mm (reduction rate of 60%). Subsequently, recrystallization was performed under the same temperature conditions as in the comparative example. The equivalent circle diameter of the recrystallized grains was 30 μm on the surface layer and 45 μm in the center, and was entirely fine recrystallized grains. As a result of visually observing the surface of the plate after completion of the processing by performing spinning processing under the conditions described in Example 2 using the recrystallized plate of this cold-rolled plate, A large crack (2 to 4 mm in length) was generated, and it was confirmed that it was not suitable for spinning.

DESCRIPTION OF SYMBOLS 1 Mold which rotates centering on the axis 2 Roll which moves a mold laterally 3 Plate which is a work material 4 Plate presser 5 Recrystallized grain size measurement position 6 Central part 7 Plate thickness direction

Claims (1)

The thickness of the aluminum alloy sheet is 5 to 10 mm, the recrystallized grain size at a depth of 0.5 mm from the surface of the alloy sheet is 50 μm or less in terms of the equivalent circle diameter average value, and the recrystallized grain size in the center is Ri der above 70μm particles having a circle equivalent diameter average value, composition, Mg is 2.0 to 3.4 wt%, Cu is 0.05 to 0.10 wt%, the total amount of Si and Fe 0.05 to 0.09% by weight, cast structure refining agent is 0.005 to 0.2% by weight, remaining Al and unavoidable impurities, of which Mn, Cr and Zr are each 0.00%. An aluminum alloy thick plate for spinning, characterized by being no more than 01% by weight .

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