JPS6017008B2 - Aluminum refining method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an aluminum refining method for obtaining high purity aluminum from low purity aluminum.

If aluminum contains impurities, especially impurities such as Fe, Si, Cu, Mg, etc. that form eutectics with aluminum, in order to remove these impurities, it is necessary to melt the aluminum containing these impurities. The principle that it is effective to selectively take out the primary crystal aluminum from the cuttings that are cooled and solidified is well known.

Conventional methods for refining impure aluminum using this principle include, for example, maintaining molten aluminum containing impurities such as Fe, Si, Cu, Mg, etc. near its liquidus temperature, and then purifying the molten aluminum. The cooling body is immersed in the cooling body to crystallize dendritic aluminum on the surface of the cooling body,
After scraping off the crystallized aluminum and letting it settle at the bottom of the tank containing the molten aluminum, the precipitated aluminum is tamped down by an appropriate means to solidify the entire molten metal, and then the coin coins are made into coins. There is a method of cutting out the high-purity region B at the bottom and separating it from the impurity concentration region. However, this method requires highly accurate temperature control of molten aluminum, scraping of primary crystal aluminum from the cooling body,
It also has the disadvantage of requiring industrially troublesome work such as tamping work. Other purification methods include fox nemelti
As an applied technology for NG, a cooling body is immersed in low-purity molten aluminum kept at a temperature near the freezing point, and primary crystal aluminum is crystallized extremely slowly on the surface of the cooling body. There is a method of obtaining purified aluminum that has solidified by adhering to it, melting this purified aluminum in another tank, and repeating the same operations as above to increase the purity. However, with this method, a certain degree of refining effect can be obtained when the aluminum is solidified very slowly around the cooling body, but when the solidification rate is on the order of several ribs per minute or more, the horizontal branched crystals of primary aluminum are produced. Since the liquid with many impurities is solidified in between, only a slight purification effect can be obtained, and the industrial cost becomes extremely high as a method for obtaining high-purity aluminum. The present invention eliminates the drawbacks of the conventional refining methods as described above and provides a highly efficient method for refining aluminum.

In the aluminum refining method of this invention, after the aluminum to be purified is melted, a cooling body whose lower surface is covered with a heat insulating material is immersed in the molten aluminum, and while the cooling body is rotated, the molten aluminum is heated by the cooling body. The cooling body is characterized by crystallizing high-purity aluminum on the circumferential surface of the cooling body.

When a cooling body whose lower surface is covered with a heat insulating material is immersed in molten aluminum and the molten aluminum is cooled by the cooling body, aluminum crystallizes on the circumferential surface of the cooling body.

This horizontal branch-like primary crystal of aluminum is of high purity, but Fe, Si, Mg, which forms a eutectic with aluminum,
, Cu, etc. are concentrated in the molten aluminum, and this is particularly noticeable in the interstices of the cylindrical crystals. In addition, depending on the concentration of impurities in the gaps between dendrites, FeA
Intermetallic compounds such as In order to obtain high-purity aluminum by solidification, the aluminum is crystallized while keeping the impurity element-concentrated liquid or the already formed intermetallic compound of the impurity element away from the vicinity of the solid-liquid interface. It is necessary to collect the crystals.
When a cooling body immersed in molten aluminum is rotated,
The concentrated impurities or intermetallic compounds of impurity elements are removed from the interstices of the dendrites, released into the molten aluminum, and dispersed and mixed. Furthermore, the above effect can be further improved by reversing the direction of rotation of the cooling body at an appropriate frequency. The reason why the lower surface of the cooling body is covered with a heat insulating material is as follows. In other words, the effect of the rotation of the cooling body is inferior on the lower surface of the cooling body than on the peripheral surface, and the concentrated impurities and intermetallic compounds of impurity elements in the gaps between the horizontal branched crystals crystallized on the lower surface of the cooling body are absorbed into the molten aluminum. Because it is difficult to release, the purity of the aluminum that crystallizes on the bottom surface of the cooling body is lower than that of the aluminum that crystallizes on the surface of the cooling body. This is because it mixes with aluminum crystallized on the surface, reducing the overall purification efficiency. Therefore, in order to prevent aluminum from crystallizing on the lower surface of the cooling body,
Cover the bottom surface of the cooling body with a heat insulating material. When the cooling body is immersed so that the entire cooling body is immersed in molten aluminum, the top surface of the cooling body is also covered with a heat insulating material for the same reason that the bottom surface of the cooling body is covered with a heat insulating material. As the cooling body, a cylindrical body, a tapered cylindrical body whose diameter gradually decreases downward, etc. are used. It is preferable to use a tapered cylindrical one because it facilitates recovery of high-purity aluminum crystallized on the circumferential surface of the cooling body, as will be described later. To recover the high-purity aluminum crystallized on the circumferential surface of the cooling body, there are, for example, a method of melting and separating the crystallized high-purity aluminum, or a mechanical method such as scraping.

When the cooling body has a tapered cylindrical shape, high-purity aluminum crystallized on the circumferential surface of the cooling body can be collected by pulling it downward, which facilitates the collection work. The cooling body is cooled by passing air, argon gas, nitrogen gas, or a mixture of air and water into its interior. The next invention will be explained with reference to the drawings.

In the drawing, a crucible 1 contains molten aluminum 2 containing impurities that form eutectic with aluminum, and a cylindrical cooling body 3 that is rotatable and closed at both ends is immersed in the molten aluminum 2. It's being crushed.

A hollow rotary shaft 4 extending upward and extending through the inside of the cooling body 3 is disposed at the upper end of the cooling body 3, and a lower end portion of the rotary shaft 4 enters into the cooling body 3. A cooling gas blow pipe 5 is inserted therein. Further, the lower and upper surfaces of the cooling body 3 and the portion of the rotary ball 4 that is present in the molten aluminum 2 are covered with a heat insulating material 6. The reason why the part of the rotating shaft 4 that exists in the molten aluminum 2 is covered with a heat insulating material is because the purity of the aluminum that crystallizes in this part is lower than the purity of the aluminum that crystallizes on the circumferential surface of the cooling body. be. In such an apparatus, the molten aluminum 2 is maintained at a temperature close to its melting point, and the cooling body 3 is rotated. At this time, a cooling gas such as air, nitrogen, or argon is fed into the cooling body 3 from the cooling gas blow pipe 5 while being controlled so that the molten aluminum 2 around the cooling body 3 is gradually cooled. Then, primary crystals of high-purity aluminum begin to crystallize on the circumferential surface of the cooling body 3. After a predetermined amount of aluminum has crystallized, the cooling body 3 is taken out and the crystallized high-purity aluminum is recovered. By repeating each of the above operations in molten aluminum with progressively higher aluminum purity, aluminum of even higher purity can be obtained.

As described above, according to the present invention, by rotating the cooling body whose lower surface is covered with a heat insulating material, the melt with high impurity concentration remaining in the gaps between the dendritic primary crystal aluminum is discharged. Since aluminum can be crystallized only on the peripheral surface of the cooling body, the purification effect is great and the purity of the obtained aluminum is high.

Next, examples of this invention will be shown.

This example was carried out using the apparatus shown in the drawings. Example 1 Feo. 0 fear% and Sio
．． 670q with molten aluminum containing 05wt%
Hold at o.

Next, while feeding air into the inside of the cooling body 3 with an outer diameter of 5 through the cooling gas blow pipe 5, the cooling body 3 is heated to a temperature of 30 mm.
It was rotated at a speed of m. After continuing this operation for 30 minutes,
Cooling body 3 was taken out. 3.1k9 on the circumferential surface of the cooling body 3
of aluminum was crystallized, and when the impurity concentration in this aluminum was measured, it was found that Feo. 03Wt%, S
io. It was 03K%. 'Example 2 Fe in crucible 1
o. 0 touch% and Sio. Add molten aluminum 2 containing 0.05 wt% and maintain at 670 qo.

Next, the cooling body 3 was rotated forward and backward intermittently at a rotational speed of 30 pm while blowing air into the cooling body 3 in the same manner as in Example 1 above. The rotation time was 3 tochisand, and the stopping time was 5 seconds. After this operation was continued for 30 minutes, the cooling body 3 was taken out. Aluminum of 3.0k9 is crystallized on the circumferential surface of the cooling body 3, and the impurity concentration in this aluminum is Feo.
．． 01 wt%, Sio. It was 0.02 wt%.

[Brief explanation of the drawing]

The drawing is a longitudinal sectional view showing an example of an apparatus used for carrying out the present invention.

Claims (1)

[Claims] 1. After melting the aluminum to be purified, a cooling body whose bottom surface is covered with a heat insulating material is immersed in the molten aluminum, and the molten aluminum is cooled by the cooling body while rotating the cooling body. An aluminum refining method characterized by crystallizing high-purity aluminum on the peripheral surface.