KR101888357B1 - Manufacturing method of magnesium and magnesium alloy ingots containing low contents of iron - Google Patents

Abstract

The present invention relates to a method for producing a recycled magnesium alloy having a low iron content using magnesium scrap and a recycled magnesium alloy having a low iron content produced by the method. More particularly, the present invention relates to a method for producing a recycled magnesium alloy containing aluminum (Al) and zirconium ) Is added to form a three-phase precipitate of iron-aluminum-zirconium (FeAlZr), which is separated and removed by gravity, and a method for producing a recycled magnesium alloy having a low iron content using the magnesium scrap. The present invention relates to a recycled magnesium alloy having a low iron content.

Description

TECHNICAL FIELD The present invention relates to a method for producing a recycled magnesium alloy having a low iron content using magnesium scrap and a recycled magnesium alloy having a low iron content,

The present invention relates to a method for producing a recycled magnesium alloy having a low iron content using magnesium scrap and a recycled magnesium alloy having a low iron content produced by the method. More particularly, the present invention relates to a method for producing a recycled magnesium alloy containing aluminum (Al) and zirconium ) Is added to form a three-phase precipitate of iron-aluminum-zirconium (Fe-AL-Zr), which is separated and removed by gravity, to produce a recycled magnesium alloy having a low iron content And a recycled magnesium alloy having a low iron content produced thereby.

In recent years, the demand for lightweight materials has increased sharply due to the need for weight reduction in portable electronic devices, aerospace and automobiles. Accordingly, magnesium alloys are attracting attention as substitutes for iron alloys and aluminum alloys.

In particular, demand for magnesium alloys will continue to increase, as it is in contact with research and development of hybrid and electric vehicles, and global environmental issues.

Such magnesium-based alloys can be improved in mechanical properties including strength, hardness, elongation, and high-temperature strength as heat resistance properties by adding specific alloying elements to magnesium-iron alloy and magnesium-zinc alloy systems or by changing manufacturing conditions including specific heat treatment can do.

The magnesium-based alloy thus produced is produced in various forms such as plate, rod and powder. Examples of the magnesium-based alloy manufacturing method include a casting method including a high-pressure die casting step, a sand casting, Mold casting, continuous casting, semi-molten molding and composite powder metallurgy are being used.

Among them, Die casting process, which is generally applied in magnesium alloy-based parts manufacturing, has already been commercialized through research on recycling technology of high-quality scrap such as runner and overflow However, there is no recycling technology for low-quality scrap recovered from spent parts in automobiles and electronic devices that have reached the end of their useful life, and development of related technologies is urgent.

The recycling process for obtaining magnesium from general magnesium scrap is performed by dividing the scrap according to the grade, melting it after washing and crushing, or melting the scrap directly in the melting furnace without going through the previous process. Followed by impurity refining and casting into ingots.

If recycled low-grade magnesium scrap, such as automobile waste parts, it can be recycled at a price of 70 ~ 80% compared to the primary ingot. This can directly reduce raw material costs and reduce indirect costs due to landfill There is an advantage to be able to do. In addition, the amount of energy and carbon dioxide generated in the process of producing the recycled ingot can be reduced by 30% or more compared to the process of producing the primary ingot, which is expected to reduce environmental load and energy.

The cast magnesium alloy is mainly composed of AM-based (Mg-Al-Mn) and AZ (Mg-Al-Zn) based alloys. The role of each metal element contained in the magnesium alloy is as follows. Aluminum (Al) improves mechanical properties by refining the casting structure of magnesium, zinc (Zn) improves castability and strength, and manganese (Mn) has an effect of improving corrosion resistance. Calcium (Ca) improves the mechanical properties by increasing grain refinement effect and stability at high temperature, and is applied to alloys used at high temperatures. Therefore, 6-10% of Al, 1-3% of Zn, and about 0.3% of Mn are added to general magnesium alloy, and a small amount of calcium (Ca) or rare earth metal is added.

It is usual that a small amount of iron (Ni), iron (Fe), copper (Cu), silicon (Si) or the like is contained in the magnesium alloy as impurities. However, when the recovered magnesium scrap is remelted and the ingot is manufactured, a small amount of impurities such as iron (Ni), iron (Fe), copper (Cu), and silicon (Si) contained in the magnesium alloy are mechanically It is essential to develop a core technology for controlling the composition of these elements. At present, recycling technology and harmful element control technology of low-grade magnesium scrap are in the early stage of technology development both domestically and abroad.

U.S. Pat. No. 3,869,281 A (issued 1975.03.04) Korean Registered Patent No. 10-1234053 (Registered on March 23, 2013)

 Current Status on the Domestic Recycling of Magnesium, J.of Korean Inst. Of Resources Recycling Vol.20, No. 3, 2011, 3-11  Microstructure Control, Forming Technologies of Mg Alloys and Mg Scrap Recycling, J.of Korean Inst. Of Resources Recycling Vol.20, No.1, 2011, 69-79

Disclosure of Invention Technical Problem [7] Accordingly, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a new method for manufacturing a recycled magnesium alloy having reduced iron content by using magnesium scrap.

The present invention also aims at providing a recycled magnesium alloy having reduced iron produced by using the magnesium scrap according to the production method of the present invention.

The present invention has been made to solve the above problems

 (a) dissolving Fe-containing magnesium scrap;

(b) adding Al and Zr to the molten magnesium scrap to form an Fe-Al-Zr ternary alloy;

(c) precipitating the Fe-Al-Zr ternary alloy obtained in the step (b);

(d) separating the sediment and the suspended matter precipitated in the step (c); And

and (e) casting a recycled magnesium alloy as the suspended matter separated in the step (d). The present invention also provides a method of manufacturing a recycled magnesium alloy having reduced iron using magnesium scrap.

In the step (b) of forming the Fe-Al-Zr ternary alloy, the Al is added in an amount of 1 to 10 parts by weight per 100 parts by weight of the magnesium scrap in the method for producing a recycled magnesium alloy in which iron scraps are reduced using the magnesium scrap of the present invention, And Zr is added in a proportion of 0.001 to 5 parts by weight.

In the method of manufacturing a recycled magnesium alloy in which iron is reduced by using the magnesium scrap of the present invention, the mass ratio of Al and Zr (Al mass / Zr mass) in the magnesium scrap dissolved in the step (b) And Zr are added.

In the method of manufacturing a recycled magnesium alloy in which iron scraps are reduced using magnesium scrap of the present invention, the step (b) includes a step of stirring for one to ten minutes to 30 minutes, and a step of stirring once more for a plurality of times.

The present invention also provides a recycled magnesium alloy in which iron is reduced using magnesium scrap produced by the method of manufacturing a recycled magnesium alloy with reduced iron using magnesium scrap of the present invention.

The iron-reduced recycled magnesium alloy according to the present invention has an iron content of 0.01% by weight or less.

The method of manufacturing a recycled magnesium alloy in which iron is reduced by using the magnesium scrap of the present invention is characterized in that aluminum and zirconium are added to a magnesium alloy to reduce iron content acting as an impurity in the magnesium-iron (Mg-Fe) alloy, Can be recycled to produce a magnesium alloy with reduced iron content.

FIG. 1 is a graph showing the Fe content in an alloy according to an addition amount of Al, Mn, and Zr to an Mg-Fe alloy according to an embodiment of the present invention, using ICP-OES.
Fig. 1 (a) shows a change in Fe content with respect to Al content (0 to 5 wt%) when Al alone is added.
1 (b) shows the change in Fe content according to the addition amount of Mn (0.25 to 1.50% by weight) in the case where Mn is additionally added to Al (5% by weight).
Fig. 1 (c) shows the change in Fe content according to the addition amount of Zr (0.25 to 1.50% by weight) when Zr is additionally added to Al (5 wt%).
FIG. 2 is a result of an optical microscope analysis of the microstructure of a sample specimen prepared by adding Al and Zr to an Mg-Fe alloy according to an embodiment of the present invention.
FIG. 3 is a graph showing the results of analyzing sample specimens prepared by adding Al and Zr to the Mg-Fe alloy according to an embodiment of the present invention and then collecting the lower layer portion. FIG. 3 (a) As a result of the analysis by electron microscope, FIG. 3 (b) shows the result of analyzing the composition of the specimen by EDS.
FIG. 4 is a result of analysis of phase identification by X-ray diffraction analysis of sample specimens prepared by adding Al and Zr to Mg-Fe alloy according to an embodiment of the present invention and collecting the lower layer portion.
FIG. 5 is a graph illustrating the Fe content of the AM50 commercial magnesium alloy according to an embodiment of the present invention when Al, Mn, and Zr are added, and the Fe content according to the fixed time after the addition is analyzed using a mass spectrometer.
5 (a) shows changes in Fe content with the standing time after adding Al and Mn to the AM50 commercial magnesium alloy.
FIG. 5 (b) shows a change in Fe content with the standing time when Zr is additionally added, with a standing time of 30 minutes after adding Al and Mn to the AM50 commercial magnesium alloy.
6 is a graph showing changes in Fe content with increasing Zr content when Al, Mn and Zr are added to an AM50 commercial magnesium alloy according to an embodiment of the present invention.
FIG. 7 is a graph showing changes in Fe content according to a standing time after adding Al, Mn, and Zr to an AZ91 commercial magnesium alloy according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited by the examples.

< Example > Waste scrap  Used magnesium alloy ( Mg - Fe )

Due to the difference in melting point between iron and magnesium, Mg-5 wt% Fe master alloy ingot was first prepared. 2 kg of Mg-0.03 wt% Fe alloy was dissolved in the crucible by using the ingot, and then aluminum (Al), manganese ( Mn) and zirconium (Zr).

Mn is an element added to lower the content of iron in the commercial magnesium alloy and added here for comparison.

content Magnesium alloy Al (wt%) Mn (wt%) Zr (wt%) Comparative Example 1 Mg-Fe alloy 0.00 0.00 0.00 Comparative Example 2 Mg-Fe alloy 1.00 0.00 0.00 Comparative Example 3 Mg-Fe alloy 2.00 0.00 0.00 Comparative Example 4 Mg-Fe alloy 3.00 0.00 0.00 Comparative Example 5 Mg-Fe alloy 4.00 0.00 0.00 Comparative Example 6 Mg-Fe alloy 5.00 0.00 0.00 Comparative Example 7 Mg-Fe alloy 5.00 0.25 0.00 Comparative Example 8 Mg-Fe alloy 5.00 0.50 0.00 Comparative Example 9 Mg-Fe alloy 5.00 0.75 0.00 Comparative Example 10 Mg-Fe alloy 5.00 1.00 0.00 Comparative Example 11 Mg-Fe alloy 5.00 1.50 0.00 Example 1 Mg-Fe alloy 5.00 0.00 0.25 Example 2 Mg-Fe alloy 5.00 0.00 0.50 Example 3 Mg-Fe alloy 5.00 0.00 0.75 Example 4 Mg-Fe alloy 5.00 0.00 1.00 Example 5 Mg-Fe alloy 5.00 0.00 1.50 Example 6 AM50 5.00 0.4 0.014 Example 7 AM50 5.00 0.9 0.00 Example 8 AM50 5.00 0.9 2.00 Example 9 AZ91 5.00 0.4 0.46

The alloying solutions containing Al and Zr in the same amounts as in Table 1 were stirred for 1 minute, 10 minutes, and 1 minute after the addition of the elements as in the compositions according to Examples and Comparative Examples, .

Thereafter, the alloy solution was allowed to stand at 720 占 폚 for 30 minutes, 5 cc of the molten magnesium alloy in the upper part of the crucible was collected and solidified by pouring into a mold to prepare a disk-shaped magnesium alloy specimen having an average diameter of 29 mm and a thickness of 7 to 10 mm.

< Experimental Example  1 > ICP- OES  Used Fe  Content analysis

The content of Fe in the samples prepared in Examples 1 to 5 and Comparative Examples 1 to 11 was analyzed by ICP-OES (inductively coupled plasma optical emission spectrometry). The results are shown in FIG.

Fig. 1 (a) shows the change in Fe content in the magnesium alloy according to the addition amount of 0 to 5 wt% Al, Fig. 1 (b) shows the change in the content of Fe in the present magnesium- And shows a change in the Fe content in the magnesium alloy due to the addition of 0.25 to 1.50 wt% of Mn added for reduction. Fig. 1 (c) shows the change of the Fe content in the magnesium alloy according to the addition amount of 0.25 to 1.50 wt.% Zr in addition to 5 wt% of Al.

As shown in FIG. 1 (a), according to Comparative Examples 1 to 6, the Fe content in the magnesium alloy was irregular when Al alone was added in an amount of 0 to 5% by weight, The content of Fe decreased significantly.

As shown in FIG. 1 (c), according to Examples 1 to 6, when Zr added in an amount of 0.25 to 1.5 wt% in addition to 5 wt% Al is further added, the Fe content in the magnesium alloy is further reduced Can be confirmed.

In particular, when 5 wt% of Al and 1.5 wt% of Zr were added, the Fe content in the magnesium alloy was reduced from 0.021 wt% to 0.001 wt%, which represents a reduction rate of about 95% of the initial Fe content.

On the other hand, as shown in FIG. 1B, according to Comparative Examples 7 to 11, when 0.25 to 1.5 wt% of Mn was added in addition to 5 wt% of Al, the Fe content in the magnesium alloy was 0.021 wt% to 0.007 wt% % &Lt; / RTI &gt; by weight.

When Mn added to the commercial alloy is added, the Fe content in the magnesium alloy is 0.073 Fe% by weight, and when Zr is further added, the Fe content in the magnesium alloy is 0.034 Fe% by weight And decreased the Fe content by 84% compared with the initial value. These results indicate that the effect of reducing Fe is about twice as much as that of Mn currently used.

< Experimental Example  2> Optical microscope  observe

The specimen of the sample prepared in the lower layer portion of Example 5 was observed through an optical microscope, and the result is shown in FIG. 2

FIG. 2 (a) is an optical microscope image of a sample specimen prepared by adding 5 weight% of Al alone by the comparative example 6, FIG. 2 (b) And 1.5 wt% Zr were simultaneously added to the sample.

As a result of observation, it can be seen that the fraction of the second phase significantly increases in the sample containing Al and Zr at the same time, compared with the sample in which Al is added alone.

< Experimental Example 3> Scanning electron microscope  observe

The specimen of the sample prepared in the lower layer of Example 5 was observed through a scanning electron microscope and the result of analysis of the sample was shown in FIG.

3 (a) shows the microstructure of a sample prepared by adding 5 wt% Al and 1.5 wt% Zr, and Fig. 3 (b) The results of the analysis are shown.

As shown in FIG. 3, it was observed that the second phase fraction increased remarkably in the sample containing 1.5 wt% Zr and 5 wt% Al simultaneously. As a result of SEM-EDS analysis, Fe- It can be confirmed that an image of -Zr ternary system exists.

< Experimental Example  4> Phase identification by X-ray diffraction

The specimen prepared in the lower layer portion of Example 5 was confirmed by X-ray diffractometry, and the result was shown in FIG.

Fig. 4 shows phase identification results of the sample specimen prepared in the lower layer portion of Example 5 containing 5 wt% Al and 1.5 wt% Zr simultaneously by X-ray diffraction.

4, in Example 5 containing 5 wt% Al and 1.5 wt% Zr at the same time, a large amount of intermetallic compounds including Al ₂ Zr, Al ₂ Zr ₃ and AlFeZr was observed in the lower layer portion of the molten metal .

All of these intermetallic compounds have a specific gravity higher than that of Mg. Among them, the main reason for decreasing the Fe content in the magnesium melt is that the AlFeZr ternary compound is formed during dissolution and precipitated by the specific gravity difference .

< Experimental Example  5> AM50 commercial magnesium Applied to alloys

The target composition (wt%) for the Fe reduction effect test in the AM50 commercial alloy is shown in Table 2 below.

element Al Mn Zr Fe Mg Content (wt%) 5.0 0.4 0.014 0.0284 Honey.

According to one embodiment, the Fe reduction effect obtained by adding Al, Mn and Zr to a magnesium alloy is applied to an AM50 commercial magnesium alloy, and the results are analyzed.

Approximately 2 kg of Mg-Fe metal was dissolved in the crucible, and then Al and Mn were added thereto to prepare a molten metal in the composition of the AM50 alloy (composition in which 5 wt% Al and 0.4 wt% Mn were slightly dissolved).

According to Example 6 of the present invention, 0.014 wt% of Zr was added to the prepared AM50 alloy melt to reduce the content of Fe, and in order to confirm the Fe reduction effect according to the standing time of the alloy melt, The Zr was added and stirred and allowed to stand for 120 minutes.

First, Al and Mn were added to the AM50 alloy, and stirring was continued for 5 minutes so that the additive element could be sufficiently dissolved in the melt. After stirring at 0, 10, 20 and 30 minutes after the stirring, 5 cc of the molten metal at the upper part of the crucible was sampled at 720 ° C. and the content of Fe was analyzed using a mass spectrometer. Fig. 5 (a) shows the results of changing the content of Fe in the AM50 alloy melt according to the settling time.

After addition of Zr, the mixture was stirred again for 5 minutes and allowed to stand for 120 minutes. The same type of sample was sampled from the upper part of the AM50 alloy melt at each fixed time. Fig. 5 (b) shows the results of changing the content of Fe in the AM50 alloy melt according to the settling time after the addition of the final alloying element.

As shown in FIG. 5 (a), when Al and Mn were added to the AM50 alloy melt, the content of Fe was reduced by 53% from the initial value after 30 minutes of standing, and the content of Fe was greatly reduced by Al and Mn Respectively.

On the other hand, as shown in FIG. 5 (b), when Al and Mn were added to the above AM50 commercial alloy and further a small amount of Zr was added, the Fe content after 30 minutes of standing time was further reduced by 46% .

When Al, Mn, and Zr were added to the AM50 commercial alloy as described above, the content of Fe was changed according to the increase of Mn and Zr, and the results are shown in FIG.

6 is a graph showing the effect of reducing the Fe when the Mn is increased to 0.9 wt%, more preferably increasing the Mn to 0.9 wt% and the Zr to 2 wt% , It can be seen that the initial Fe content significantly decreased from 0.0284 wt% to 0.0025 wt% or less.

Therefore, it was confirmed that the addition of Zr in the magnesium alloy is very effective in removing Fe, and even when the composition is applied to the AM50 commercial magnesium alloy composition, the content of iron in the upper part of the molten metal is effectively reduced with the lapse of the settling time of the melt.

< Experimental Example  6> AZ91 commercial magnesium Applied to alloys

The target composition (wt%) for the Fe reduction effect test in the AZ91 commercial alloy is shown in Table 3 below.

element Al Zn Mn Zr Fe Mg Content (wt%) 5.0 0.9 0.4 0.46 0.03 Honey.

According to one embodiment, the reduction effect of Fe, which is obtained by adding Al, Mn and Zr to a magnesium alloy, is applied to an AZ91 commercial magnesium alloy, and the results are analyzed.

A molten metal was prepared from the composition of AZ91 commercial magnesium alloy (5 wt% Al, 0.9 wt% Zn, and 0.4 wt% Mn in a small amount of solid solution) in the same manner as the previously prepared AM50.

According to Example 9 of the present invention, Zr was added in an amount of 0.46% by weight in order to reduce Fe content in the AZ91 alloy melt, and the content of Fe in the alloy was analyzed according to the set time.

As shown in FIG. 7, when Al and Mn were added to AZ91 alloy melt and Zr was additionally added in a small amount, it was confirmed that Fe content significantly decreased from 0.03 wt% to 0.010 wt% I could.

Claims (6)

(a) dissolving Fe-containing magnesium scrap;
(b) adding any one of i) and ii) to the molten magnesium scrap to form an Fe-Al alloy,
i) Al and Zr
ii) Al, Mn and Zr;
(c) precipitating the Fe-Al alloy obtained in the step (b);
(d) separating the sediment and the suspended matter precipitated in the step (c); And
(e) casting a recycled magnesium alloy as the suspended matter separated in the step (d)
(METHOD FOR MANUFACTURING RECYCLED MAGNESIUM ALLOY WHICH HAS BEEN REDUCED FROM MAGNESIUM SCRAP.
The method according to claim 1,
In the step (b) of forming the Fe-Al alloy, 1 to 10 parts by weight of Al and 0.001 to 5 parts by weight of Zr are added per 100 parts by weight of the magnesium scrap.
(METHOD FOR MANUFACTURING RECYCLED MAGNESIUM ALLOY WHICH HAS BEEN REDUCED FROM MAGNESIUM SCRAP.
The method according to claim 1,
In the step (b), Al and Zr are added so that the mass ratio of Al and Zr (Al mass / Zr mass) is 1 to 1000
(METHOD FOR MANUFACTURING RECYCLED MAGNESIUM ALLOY WHICH HAS BEEN REDUCED FROM MAGNESIUM SCRAP.
The method according to claim 1,
In the step (b), the step of stirring once, the step of stirring for 10 to 30 minutes, and the step of stirring once more are repeated a plurality of times
(METHOD FOR MANUFACTURING RECYCLED MAGNESIUM ALLOY WHICH HAS BEEN REDUCED FROM MAGNESIUM SCRAP.
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