JPH05279766A - Method for melting specific metal into aluminum - Google Patents

Abstract

PURPOSE:To finely and uniformly disperse the under mentioned metal into Al by forming a metal, such as Pb, In, Ti, and Bi, into a sheet, covering this sheet with a metal foil having a melting point higher than that of the sheet and capable of melting in molten Al, and then adding the resulting covered material into molten Al. CONSTITUTION:At least one metal among Pb, In, Ti, and Bi which do not enter into solid solution is finely dispersed into Al by about 0.5wt.%, by which an Al alloy excellent in machinability can be obtained. In the method for melting the metal, the metal is formed into a sheet of <=0.5mm thickness and, preferably, is formed into small pieces of about 10-300mm major axis and about 5-300mm minor axis. Subsequently, this sheet is covered with a metal foil having a melting point higher than that of the sheet but capable of melting in molten Al. As the metal foil, Al foil, Cu foil, Zn foil, etc., can be used and suitable thickness of covering is about 0.015-0.2mm. Then the resulting covered material is added into molten Al and melted by agitation. By this method, the metal can be uniformly dispersed into Al to an average grain size about one-tenth the thickness of the sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to Pb in aluminum,
The present invention relates to a dissolution method for finely and uniformly dispersing at least one metal selected from In, Tl and Bi.

[0002]

2. Description of the Related Art Generally, criteria for evaluating machinability include (1) chip disposability, (2) surface finish quality, (3) tool life, and (4) cutting resistance. Since the aluminum alloy is relatively soft, the properties of (3) and (4) are hardly problematic, and the properties of (1) and (2) are emphasized. When it comes to cutting, the chip treatment characteristic of (1) is given the highest priority.

In order to improve the machinability of an aluminum alloy, an alloy composition or compound having a low melting point such as Pb or Bi which is not solid-dissolved in aluminum and which is finely dispersed is used. This is because the alloy composition or compound with a low melting point is melted by cutting heat to give a liquid metal embrittlement action or a notch action, and the volume expansion during melting increases the internal stress of the aluminum phase, so that chips are easily fragmented. In addition, it is believed that the friction surface between the chips and the tool exerts a lubricating action to prolong the life of the tool.

As such an aluminum alloy, AA
2011 (Pb 0.5 wt%, Bi 0.5 wt%)
And AA6262 (Pb 0.5 wt%, Bi 0.5 wt%).

Further, Japanese Patent Publication No. 62-42370, Japanese Patent Publication No. 61-44139, and Japanese Patent Publication No. 60-47896.
As disclosed in Japanese Patent Publication No. 62-25248 and Japanese Patent Publication No. 62-25248, Pb, In,
By adding Bi and Tl, the etching characteristics and the electrostatic capacity are improved.

However, these metals such as Pb are listed in Table 1.
As shown in, the specific gravity is larger than that of aluminum, and the liquid and aluminum do not separate from each other by two liquid phases. In order to secure the performance of the aluminum alloy for cutting and the aluminum foil for electrolytic capacitors, it is important to finely and uniformly disperse these metals such as Pb in the solid phase of the aluminum alloy.

[0007]

As described above, since these metals such as Pb do not even dissolve in molten aluminum, in order to disperse finely and evenly in the solid phase of the aluminum alloy, Pb and the like in molten aluminum should be dispersed. It is important how finely and uniformly these metals are dispersed. However, no industrially good method for finely and uniformly dispersing these metals such as Pb in molten aluminum has been known.

[0008]

In view of such circumstances, the inventors of the present invention have conducted extensive studies for the purpose of finely and uniformly dispersing these metals such as Pb in molten aluminum, and as a result, the present invention has been achieved. It came to completion.

That is, the present invention is a method for dissolving at least one metal selected from Pb, In, Tl and Bi in molten aluminum, wherein the metal has a thickness of 0.5 m.
After thinning the plate to m or less, and then encapsulating the thin plate with a metal foil having a melting point higher than that of the thin plate but soluble in molten aluminum, the encapsulating material is added to molten aluminum and dissolved by stirring. It is intended to provide a characteristic method for dissolving a specific metal in aluminum.

The present invention will be described in detail below. The metal to be dissolved in molten aluminum, which is the object of the present invention, is P
At least one selected from b, In, Tl, and Bi. As mentioned above, these metals such as Pb do not even melt molten aluminum and separate into two liquid phases. If a metal having a low melting point such as Pb or the like and a large specific gravity as compared with the specific gravity of molten aluminum of 2.3 g / cm ³ is added in a lump form, the molten aluminum is melted even if it is sufficiently stirred. These metals such as Pb formed into large drops and gradually settle after the stirring due to the difference in specific gravity.

In the method of the present invention, first, the metal to be dissolved in molten aluminum is thinned to a thickness of about 0.5 mm or less. The thinning method is not particularly limited as long as it is a known method. Of course, a commercially available product may be used as long as it is a thin plate having a thickness of about 0.5 mm or less. The lower limit of the thickness is preferable, because fine particles can be dispersed when dissolved in molten aluminum, but from the viewpoint of economy or handling, it is about 0.05 mm or more, and usually about 0.1 mm or more.

The metal sheet is then encapsulated with a metal foil whose melting point is higher than that of the sheet but which is soluble in molten aluminum. Examples of such metal foil include aluminum foil, copper foil, zinc foil and the like. When using a metal foil other than an aluminum foil, calculation as a desired alloy composition is required. The thickness of the metal foil is only required to be able to cover the thin metal plate, and its thickness is not particularly limited,
Usually, a thickness of about 0.015 mm to about 0.2 mm is used.

In the case of encapsulating with a metal foil, it is recommended that the metal thin plate be made into small pieces from the viewpoints of workability such as addition to molten aluminum or encapsulation with a metal foil, dispersibility by stirring and the like. The shape of the small piece is not particularly limited, such as rectangular or circular. The size of the small piece is also not particularly limited, but is usually about 10 mm to about 300 mm in major axis and about 5 m in minor axis.
It is used in the range of m to about 300 mm.

In carrying out the method of the present invention, Pb, In,
When metals such as Tl and Bi are added in a thin plate without being covered with a metal foil, even if the molten aluminum is added in a sufficiently stirred state, it is at the same level as the plate thickness of the added metal. Since it is only dispersed in small droplets of the size, and there is a limit to thinning these metals, several μm to several tens of μm
Particles having a particle size cannot be finely and uniformly dispersed.
However, when these metals such as Pb are thinned and wrapped with a metal foil, that is, after encapsulation, this encapsulation is added to molten aluminum and melted with stirring, it is about 1/10 of the thin plate thickness. It was found to disperse to an average particle size. Therefore, the one having an average particle size of about 50 μm or less in a dispersed state in molten aluminum can be obtained by making the thickness of the thin plate 0.5 mm or less.

It is not clear why such a metal such as Pb can be finely dispersed in molten aluminum by such a structure, but it is presumed that the reason is as follows. That is,
By wrapping the metal pieces with a metal foil such as an aluminum foil, the apparent specific gravity becomes lighter than that of molten aluminum, and the metal pieces are added in a state of floating on the molten aluminum. Further, although these metals such as Pb in the metal foil are immediately melted, the metal foil having a higher melting point is not melted at that time, and thus these metals such as Pb are melted in the metal foil in a thin plate shape. .. In such a state, when the metal foil encapsulating the melted Pb or other metal is melted, the molten metal in the encapsulation is also released into the molten aluminum with sufficient stirring, and is subjected to sufficient stirring. Therefore, it is considered that the particles will be finely and uniformly dispersed in the molten aluminum soon after they settle.

[0016]

EXAMPLES The method of the present invention will be described below with reference to examples, but the present invention is not limited to these examples. In this example, the Pb dispersion state was measured by buffing the sample and observing the microstructure.

Example 1 A Pb thin plate rolled to a thickness shown in Table 2 was cut into small pieces each having a width of 1 cm and a length of about 5 cm, and then wrapped with a commercially available aluminum foil (thickness: about 20 μm) to form a Pb small piece of aluminum. A foil envelope was created. Then purity 99.99% in crucible
5 kg of high-purity aluminum of No. 3 was melted, and the aluminum foil-encapsulated thin Pb piece obtained by the above method was stirred as it was held at 750 ° C., and 7.5 g (Pb15
(Corresponding to 00 ppm) was gradually added. After the addition, the mixture was sufficiently stirred and then cast into a graphite mold, and the sample was observed for microstructure. The results are shown in Table 2.

Comparative Examples 1 and 2 Example 1 was carried out using Pb thin plates rolled to the thickness shown in Table 2.
As in the case of Example 1, Comparative Example 1 was wrapped with an aluminum foil (thickness: about 20 μm), and Comparative Example 2 was wrapped with an aluminum foil.
While stirring in 5 kg of 9% high-purity aluminum, 7.5 g of Pb was added in the same manner as in Example 1, cast into a graphite mold in the same manner as in Example 1, and the sample was observed for microstructure. The results are shown in Table 2.

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

According to the present invention, fine and uniform dispersion of Pb, In, Tl and Bi, which have been difficult to dissolve in aluminum, into the molten aluminum, which has hitherto been difficult, is carried out by thinning the metal into a metal foil. It is made possible by the extremely simple operation of encapsulating with and economical method, and its industrial value is enormous.

Claims (2)

[Claims] 1. Pb, In, Tl in molten aluminum
And a method of dissolving at least one metal selected from Bi, the metal being thinned to a thickness of 0.5 mm or less, and then the thin plate having a melting point higher than that of the thin plate but capable of melting in molten aluminum. A method for dissolving a specific metal in aluminum, which comprises encapsulating with foil and then adding the encapsulated material to molten aluminum with stirring to dissolve. 2. The metal foil is at least one of aluminum foil, copper foil and zinc foil.
A method for dissolving a specific metal in aluminum as described.