JP2003147445A - Method for refining magnesium alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refining method having good workability without using inert gas and a filter, to the refining of a molten Mg alloy remelted in recycling Mg alloy scrap. SOLUTION: The Mg alloy scrap 3 is melted in a crucible 2 to obtain the molten magnesium alloy 5. Impurities 7 in the molten Mg alloy 5 are settled by giving the vibration of an ultrasonic vibrator 13 to the sludge 8 on the bottom part. Thus it is unnecessary to use flux, bubbling with the inert gas and the filter for removing the impurities, and the Mg alloy scrap can be economically be recycled under good working environment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for refining a magnesium (hereinafter also referred to as Mg) alloy which is lightweight and has excellent recyclability.

[0002]

2. Description of the Related Art As a method of recycling Mg alloy scrap, a method of remelting the Mg alloy scrap in a melting furnace and using a flux to remove impurities is generally used. However, the use of flux deteriorates the working environment and produces a large amount of industrial waste such as dross and sludge, which has a large impact on the global environment. Therefore, a fluxless refining method that does not use flux is being developed. As a fluxless refining method, a method of filtering impurities with a filter (Japanese Patent Publication No. 56-
18063), a method of separating impurities by bubbling an inert gas (JP-A-3-291350, JP-A-6-158192, etc.) and the like have been proposed. These conventional techniques will be described below with reference to the accompanying drawings.

FIG. 2 illustrates a refining method using flux. In the figure, 1 is a burner, 2 is a crucible, and 3
Indicates Mg alloy scrap. As shown in (a) of the figure, the Mg alloy scrap 3 is put into the crucible 2 and is heated while sprinkling a flux for melting to melt the Mg alloy scrap.

FIG. 1B shows a state after heating and melting, 4 is a refining flux, 5 is a Mg alloy melt, 6 is a stirring tool, and 7 is suspended in the Mg alloy melt 5. Indicates an impurity. After the Mg alloy scrap 3 is completely melted,
The flux 4 is charged and the impurities 7 are aggregated by stirring with the stirrer 6, and are precipitated on the bottom of the crucible 2.

FIG. 1C shows the state in which the impurities 7 are settled, and 8 shows the set impurities (sludge).
After that, the sludge 8 is removed, the components are adjusted, and the clean Mg alloy molten metal 5 from which impurities are separated is cast into a mold by using a ladle or a metal pump to obtain a clean M
A g ingot can be obtained.

FIG. 3 illustrates a method of removing impurities by bubbling an inert gas. As shown in (a) of the figure, the Mg alloy scrap 3 is put into the crucible 2 and adjusted so that the inside of the crucible becomes an inert gas atmosphere, and then heated.
Melt alloy scrap. Thereafter, as shown in FIG. 3B, a jig 9 having a large number of holes is dipped in the molten Mg alloy 5 and an inert gas such as argon (Ar) gas is blown through the inert gas blowing pipe 10 for bubbling. . At this time, there are two methods, namely, a method of actively stirring and floating the impurities 7 to separate them, and a method of shaking the molten metal surface as much as possible to prevent oxidation. As shown in (c) of the figure, after removing the impurities (dross) 11 that have been floated and separated, clean M
The g alloy melt 5 is cast into a mold using a ladle or a metal pump.

FIG. 4 illustrates a method of removing impurities using a filter. As shown in (a) of the figure,
The method of charging the Mg alloy scrap 3 into the crucible 2 and melting it is the same as that in the case of gas bubbling in FIG.
After the melting is completed as shown in (b), the filter 12 is immersed in the Mg alloy molten metal 5 as shown in (c) to filter impurities 7, and the clean Mg alloy molten metal 5 which has entered the filter 12 is obtained. Is cast into a mold using a ladle or a metal pump.

[0008]

Among the conventional refining methods described above, the refining method using flux described with reference to FIG. 2 has a problem that the load on the global environment is large. As described above. The bubbling method described with reference to FIG. 3 and the filter method described with reference to FIG. 4 can solve the problems of the flux method because no flux is used, but the refining method by bubbling in FIG. However, in addition to the atmosphere gas, an inert gas such as Ar gas is required for bubbling, which is not economical. Also, FIG.
In the case of filtration with the filter of No. 3, it was necessary to clean the filter after use, and workability was poor.

The present invention has been made in view of the above circumstances, and regarding the recycling of the Mg alloy scrap, the refining of the remelted Mg alloy molten metal does not require an inert gas or a filter, and the workability is also improved. The purpose is to provide a good refining method.

[0010]

In the structure of the present invention for solving the above problems, ultrasonic waves are applied to the molten Mg alloy through a crucible or directly to the molten Mg alloy,
The impurities were settled by utilizing the difference in specific gravity between the impurities and the molten Mg alloy to separate them from the Mg alloy.

That is, the invention of claim 1 is a method of refining a magnesium alloy for removing impurities from a magnesium alloy melt in which magnesium alloy scrap is melted, by applying ultrasonic waves to the magnesium alloy melt, A method for refining a magnesium alloy, characterized in that impurities are precipitated and separated.

The invention of claim 2 is the method for refining a magnesium alloy according to claim 1, wherein the ultrasonic wave is applied through a crucible containing the molten magnesium alloy. This method can be performed by transmitting the vibration of an ultrasonic oscillator or the like to the crucible.

The invention of claim 3 is the method for refining a magnesium alloy according to claim 1, wherein the ultrasonic wave is directly applied to the molten magnesium alloy. In this method, for example, ultrasonic waves can be directly applied to the molten alloy by inserting a plate-shaped vibrating piece into the molten metal.

The invention according to claim 4 is the method for refining a magnesium alloy according to any one of claims 1 to 3, wherein the composition of the magnesium alloy melt is adjusted before applying ultrasonic waves to the magnesium alloy melt. .

According to a fifth aspect of the invention, the ultrasonic wave is carried out at a temperature of the molten magnesium alloy of 700 to 780 ° C., preferably 72.
The method for refining a magnesium alloy according to claim 1, wherein the method is applied while being kept at 0 to 760 ° C.

In the invention of claim 6, the ultrasonic wave has a frequency of 5k.
The method for refining a magnesium alloy according to claim 1, wherein the frequency is -50 kHz, preferably 10-20 kHz.

[0017]

In the Mg alloy refining method of the present invention as described above, the applied ultrasonic wave acts so as to easily separate the impurities from the molten Mg alloy. Since the impurities are heavier than the molten Mg alloy, they settle at the bottom of the melting furnace (crucible). As a result, it became possible to remove impurities from the molten Mg alloy without using an inert gas for bubbling or a filter for filtration as well as the flux.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the refining method for Mg alloy of the present invention will be described below with reference to FIG.

In FIG. 1A, 1 is a burner, 2 is a crucible, 3 is a Mg alloy scrap, and 13 is an ultrasonic transducer. First, the Mg alloy scrap 3 is put into the crucible 2 and adjusted so that the inside of the crucible 2 is in an inert gas atmosphere and heated to melt the Mg alloy scrap 3.

(B) of the figure shows the state after heating and melting, 5 indicates the Mg alloy melt, and 7 indicates impurities floating in the Mg alloy melt 5. After the Mg alloy scrap 3 is completely melted, the molten Mg alloy 5 is kept at 700 ° C. or higher,
The molten Mg alloy 5 through the crucible 2 by the ultrasonic vibrator 13
Apply ultrasonic waves to.

The composition of the molten Mg alloy 5 may be adjusted by adding an appropriate elemental component before applying ultrasonic waves, such as before melting, during melting, or after melting. This is because the Mg alloy obtained by refining has a desired composition. The metals added for the purpose of adjusting the components include Al, Zn, and pure M.
g etc. In this case, Al, Zn, and the like are added as additional elements, and pure Mg is added for the purpose of thinning the molten metal (for example, if the amount of the component elements deviates from the upper limit, the amount of dissolution is increased and kept within a predetermined value).

While the ultrasonic wave is being applied, the molten Mg alloy 5 is kept at 700 ° C. or higher, and the holding temperature range is 700 to 780 ° C., preferably 720 to 760.
The range of ° C is desirable. If it is less than 700 ° C, it is difficult to obtain the separating action by ultrasonic waves. Further, if it exceeds 780 ° C., it is not preferable because it easily burns.

The ultrasonic wave applied to the molten Mg alloy 5 has a frequency of 5 to 50 kHz, preferably 10 to 20 kHz. If the frequency is less than 5 kHz, the action of separating impurities from the Mg alloy is unlikely to appear. Also, when it exceeds 50 kHz,
A separation action and a stirring action also appear, which is not preferable.

In the illustrated embodiment, the ultrasonic vibrator 13 vibrates the crucible 2 so that the vibration is transmitted to the molten Mg alloy 5 through the vibration of the crucible 2.
A vibrating body (not shown) may be immersed in the molten Mg alloy 5 in the crucible 2 for direct transmission.

FIG. 1 (c) shows a state in which ultrasonic waves are applied to the molten Mg alloy melt 5 to precipitate the impurities 7. In the figure, 8 indicates precipitated impurities (sludge). Impurities 7 are easily separated from the molten Mg alloy 5 by ultrasonic waves,
The impurities 7 settle and separate due to the difference in specific gravity between the molten Mg alloy 5 and the impurities 7, and become sludge 8.

Clean Mg alloy molten metal 5 with impurities 7 separated
A clean Mg alloy ingot can be obtained by casting into a mold with a ladle or a metal pump.

[0027]

EXAMPLE The composition of the alloy is Al: 8.6 mass%, Zn:
0.5% by mass, Mn: 0.3% by mass, the balance is substantially M
The result of refining the Mg alloy scrap of g by the above method will be described below.

80 kg of Mg alloy scrap 3 was added to the crucible 2
And melt to form Mg alloy melt 5, which is
With the temperature kept at 0 ° C., the vibration of the ultrasonic oscillator 13 was applied to the molten Mg alloy 5 through the crucible 2. The composition of the molten Mg alloy 5 was not adjusted. The frequency of the applied ultrasonic waves was 20 kHz, and the ultrasonic waves were applied for 30 minutes.

Impurities 7 in the molten Mg alloy 5 are separated by ultrasonic waves under the above conditions and settled as sludge 8 on the bottom of the crucible 2, and then a clean molten Mg alloy 5 is cast in a mold to produce an ingot. I chose

The cleanliness of the obtained ingot was evaluated by the corrosion resistance (corrosion rate). Generally, when the cleanliness of a Mg alloy decreases, the corrosion resistance also tends to decrease. The results are shown in Table 1.

[0031]

[Table 1]

For comparison, the corrosion resistance result of an ingot produced without refining and the test result of an ingot produced by refining using a flux (conventional method) are also shown. The test piece was produced by chipping an ingot and injection molding. Further, the corrosion resistance was determined by the corrosion rate by a salt spray test according to JIS Z2371. From these results, the test piece (with refining) obtained by the refining method of the present invention has the same level of corrosion resistance as the test piece (conventional material) obtained by the conventional refining method using flux. It was confirmed that the impurities were sufficiently removed by the refining method of.

[0033]

As described above, according to the present invention, it is possible to remove impurities by applying ultrasonic waves to the crucible or the molten Mg alloy. Therefore, in order to remove impurities, bubbling with a flux or an inert gas is carried out. , No need to use a filter, good working environment and economical
g alloy scrap can be recycled.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, (a) is a diagram showing a state in which Mg alloy scrap is charged into a crucible, and (b) is an M diagram.
FIG. 3 is a diagram showing a state in which g alloy scrap is melted to form a molten Mg alloy, and FIG.

FIG. 2 is a diagram for explaining a conventional Mg alloy refining method using a flux, where (a) is a diagram showing a state in which Mg alloy scrap is loaded into a crucible, and (b) is a diagram showing a state in which Mg alloy scrap is melted to form an Mg alloy. FIG. 4 is a diagram showing a state in which a molten metal and a flux are being added, and FIG.

FIG. 3 is a diagram for explaining a conventional Mg alloy refining method by bubbling an inert gas, (a) showing a state in which Mg alloy scrap is put into a crucible, and (b) melting Mg alloy scrap. FIG. 4C is a diagram showing a state where bubbling is performed as a molten Mg alloy, and FIG. 7C is a diagram showing a state in which impurities are floating as dross.

FIG. 4 is a diagram illustrating a refining method of a Mg alloy using a conventional filter, (a) is a diagram showing a state in which Mg alloy scrap is charged into a crucible, and (b) is a diagram showing a state in which Mg alloy scrap is melted to form an Mg alloy. FIG. 4C is a diagram showing a state of being a molten metal, and FIG. 7C is a diagram showing a state where the filter is immersed in the molten Mg alloy.

[Explanation of symbols]

1 burner 2 crucible 3 Mg alloy scrap 4 flux 5 Mg alloy molten metal 6 Mixing equipment 7 impurities 8 sludge 9 jigs 10 Inert gas blowing pipe 11 Dross 12 filters 13 Ultrasonic transducer

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hitohisa Yamada             4 Chatsu-cho, Muroran-shi, Hokkaido Japan Co., Ltd.             Inside the steel mill F-term (reference) 4K001 AA38 BA22 DA01

Claims (6)

[Claims] 1. A method of refining a magnesium alloy for removing impurities from a magnesium alloy melt in which magnesium alloy scrap is melted, by applying ultrasonic waves to the magnesium alloy melt,
A method for refining a magnesium alloy, which comprises precipitating and separating impurities in a molten magnesium alloy. 2. The method for refining a magnesium alloy according to claim 1, wherein the ultrasonic wave is applied through a crucible containing a molten magnesium alloy. 3. The method for refining a magnesium alloy according to claim 1, wherein the ultrasonic waves are directly applied to the molten magnesium alloy. 4. The method for refining a magnesium alloy according to claim 1, wherein the components of the molten magnesium alloy are adjusted before applying ultrasonic waves to the molten magnesium alloy. 5. The method for refining a magnesium alloy according to claim 1, wherein the ultrasonic wave is applied while maintaining the temperature of the molten magnesium alloy at 700 to 780 ° C., preferably 720 to 760 ° C. 6. The method for refining a magnesium alloy according to claim 1, wherein the ultrasonic wave has a frequency of 5 kHz to 50 kHz, preferably 10 kHz to 20 kHz.