WO2019198476A1

WO2019198476A1 - Impurity removal method

Info

Publication number: WO2019198476A1
Application number: PCT/JP2019/012518
Authority: WO
Inventors: 山口　勝弘; 憲章中塚
Original assignee: 株式会社神戸製鋼所
Priority date: 2018-04-09
Filing date: 2019-03-25
Publication date: 2019-10-17

Abstract

An impurity removal method of one embodiment comprises: a step for adding Mg or an Mg alloy to Al or an Al alloy melt containing impurities; a step for maintaining the melt after said addition step to within a temperature range of 470 to 650°C; and a step for separating an intermetallic compound generated in said maintenance step from the melt. The Mg concentration in the addition step is at least 11 mass% with respect to the melt.

Description

Impurity removal method

The present invention relates to a method for removing impurities.

In recent years, weight reduction of automobiles and the like has been promoted all over the world due to social demands for suppressing carbon dioxide emissions, and the demand for Al is expected to increase in the future. In the future, it is expected that the amount of Al scrap discharged will increase as demand increases. In general, Al is considered to be a metal material with excellent recyclability, and many Al products made from Al expanded material such as aluminum cans and die-cast products are remelted after disposal and recycled to new products. Is done. However, impurities are attached to Al products after disposal, and the concentration of impurity elements gradually increases by repeated recycling, so it is common to cascade-recycle to products with less component specifications. .

As a method for suppressing the contamination of impurities into Al, sophistication of the separation technique after shredding is in progress. However, since it is difficult to completely remove deposits, finally, a technique for removing impurities from the molten Al or Al alloy is necessary.

Many methods for removing impurities from Al or Al alloy molten metal have been reported. In particular, as a method for removing Fe that is difficult to remove, Mn as an impurity is added and Al—Fe—Mn intermetallic compounds are added. A technique for removing the intermetallic compound by centrifuging, suction or the like after crystallization has been proposed (see Patent Document 1 and Patent Document 2).

Also, as a technique for reducing the impurity concentration from Al or Al alloy molten metal, a technique using a three-layer electrolytic refining method or a segregation method in a process of manufacturing an aluminum ingot is disclosed (see Non-Patent Document 1).

Japanese Unexamined Patent Publication No. 08-035021 Japanese Patent Laid-Open No. 07-070666

However, in the techniques disclosed in Patent Document 1 and Patent Document 2, the added Mn may increase as an impurity. In addition, although the technique disclosed in Non-Patent Document 1 can in principle remove Fe by this method, the yield may be lowered as a method of refining scrap containing a large amount of impurity elements. . In addition, the three-layer electrolysis method has poor profitability in Japan where the power cost is high, and the segregation method has a risk that the yield decreases as the impurity concentration of the raw material increases. As described above, the above prior art is not sufficient as a method for recycling Al scrap containing a large amount of impurities recovered from the city in Japan.

Therefore, in order to realize horizontal recycling from wrought material of Al to wrought material, impurities that adversely affect quality can be removed from Al or Al alloy molten metal and reduced to below the allowable concentration of wrought material. A technique that can be used is desired.

The present invention has been made in view of such circumstances, and an object thereof is to provide an impurity removal method capable of efficiently removing impurities that are mixed in Al or an Al alloy and are difficult to remove from the molten metal.

As a result of diligent research, the present inventor has found that Al or an Al alloy molten metal containing impurities contains Mg, which is an essential element in a JIS-A5000 series Al alloy or the like, at a high concentration, and the molten metal is an Al—Mg binary phase diagram. It was found that an intermetallic compound containing an impurity element as an initial crystal was produced by maintaining the temperature around the liquidus temperature. Based on this finding, it was conceived that the impurity concentration can be reduced by removing the intermetallic compound.

In one embodiment of the present invention made to solve the above problems, a step of adding Mg or an Mg alloy into an Al or Al alloy molten metal containing impurities, and a molten metal after the adding step of 470 ° C. or more and 650 ° C. or less And a step of separating the intermetallic compound produced in the holding step from the molten metal, and the Mg concentration in the adding step is 11% by mass or more with respect to the molten metal. It is a removal method.

The impurity removal method is such that Mg is contained at a high concentration of 11% by mass or more with respect to Al or Al alloy molten metal, and the molten metal is held in a temperature range of 470 ° C. or higher and 650 ° C. or lower, thereby forming an impurity element as an initial crystal. An intermetallic compound containing is efficiently produced. The reason why the effect of the present invention can be obtained is assumed as follows. By adding 11 mass% or more of Mg to the Al or Al alloy molten metal to obtain an Al-Mg alloy containing Mg at a high concentration, the liquidus temperature of the Al or Al alloy molten metal is lowered. It is presumed that an intermetallic compound containing an impurity element generated during solidification of the Al alloy molten metal is likely to be formed as a primary crystal. Further, it is presumed that the activity of the impurity element is increased by Mg, and further the generation of intermetallic compounds is promoted. Then, by removing this intermetallic compound from the molten metal, the impurity concentration can efficiently correspond to the standard concentration of A5000 (Al—Mg alloy) defined by JIS. Moreover, since Mg is an essential element in the A5000 system, a removal step is unnecessary, and the molten metal can be diluted and reused for the Al product.

The holding time in the holding step is preferably 5 minutes or more. When the holding time is 5 minutes or longer, the compound can be effectively grown coarsely.

It is preferable that the impurity contains Fe and the intermetallic compound contains Al and Fe. In the impurity removal method, since the impurity contains Fe and the intermetallic compound contains Al and Fe, the impurity Fe can be efficiently removed from the Al—Mg melt.

It is preferable that the impurity contains Si and the intermetallic compound contains Mg and Si. In the impurity removal method, since the impurity contains Si and the intermetallic compound contains Mg and Si, the impurity Si can be efficiently removed from the Al—Mg melt.

The impurities include Mn, Co, Ti, V, Zr, Cr or a combination thereof, and the intermetallic compound includes Al and Mn, Co, Ti, V, Zr, Cr, or a combination thereof. preferable. In the impurity removal method, the impurity includes Mn, Co, Ti, V, Zr, Cr or a combination thereof, and the intermetallic compound is Al and Mn, Co, Ti, V, Zr, Cr, or a combination thereof. Therefore, impurities such as Mn, Co, Ti, V, Zr, and Cr can be efficiently removed from the Al—Mg-based molten metal.

It is preferable that a cooling pipe supplied with a cooling medium in the separation step is inserted into the molten metal to crystallize the intermetallic compound on the surface of the cooling pipe. A cooling pipe to which a cooling medium is supplied in the separation step is inserted into the molten metal, and locally held at 470 ° C. or more and 650 ° C. or less to crystallize the intermetallic compound on the surface of the cooling pipe. The intermetallic compound can be efficiently separated and removed without cooling the whole.

It is preferable to filter the molten metal with a heat-resistant filter in the separation step. By filtering the molten metal with a heat resistant filter in the separation step, the intermetallic compound can be easily and efficiently removed from the molten metal outside the system.

It is preferable that the intermetallic compound is allowed to settle or float by allowing the molten metal to stand in the separation step. The intermetallic compound having a specific gravity different from that of the molten metal can be removed at a low cost by allowing the molten metal to stand in the separation step so that the intermetallic compound settles or floats.

It is preferable to centrifuge the molten metal in the separation step. Since the molten metal is centrifuged in the separation step, the intermetallic compound can be efficiently removed from the molten metal.

In the separation step, an inert gas containing N ₂ gas, Ar gas or He gas, chlorine gas, flux, or a combination thereof is introduced into the molten metal, and the intermetallic compound is introduced into the bubbles, flux or After adsorbing to these combinations, it is preferably removed by floating and separating. In the separation step, an inert gas containing N ₂ gas, Ar gas or He gas, chlorine gas, flux, or a combination thereof is introduced into the molten metal, and the intermetallic compound is introduced into the bubbles, flux or After adsorbing to these combinations, floating and separating, and scraping out the intermetallic compound using a jig or the like, the intermetallic compound can be efficiently removed out of the system.

The impurity removal method of the present invention can efficiently remove impurities that are mixed in Al or Al alloy and are difficult to remove from the molten metal.

Hereinafter, embodiments of the impurity removal method of the present invention will be described in detail.

The impurity removal method of the present invention is a method of removing impurities that are mixed in Al or Al alloy and are difficult to remove from the molten metal using Mg, which is a 5000-based essential element. The impurity removal method includes an Mg addition step of adding Mg or Mg alloy to the molten metal, a temperature holding step of holding the molten metal after the adding step in a predetermined temperature range, and an intermetallic compound generated in the holding step. An intermetallic compound separation step of separating. The impurity removal method further includes a cooling step after the temperature holding step.

The impurity removal method is a method for efficiently removing metal elements that are difficult to remove in the Al recycling process from the Al—Mg melt. The inclusion of Mg, which is an essential element in a JIS-A5000 series Al alloy or the like, is promoted to promote the eutecticization of impurities, and the generated intermetallic compound is separated to remove the impurities. The present invention does not require a step of mixing unnecessary impurities in order to generate an intermetallic compound as conventionally performed, and can improve the yield. Thus, by using the impurity removal method, the impurity element can be reduced below the allowable value of the JIS-A5000 impurity concentration used as the wrought material.

The impurity removal method includes (1) Fe, (2) Si, (3) Mn, Co, Ti, V, Zr, Cr, or a combination thereof as impurities contained in the molten Al or Al alloy. Impurities of all combinations of Fe, Si, Mn, Co, Ti, V, Zr, and Cr listed in the above (1) to (3) are to be removed by the impurity removal method. In the impurity removal method, an intermetallic compound containing these impurities is formed by containing Mg at a high concentration.

(1) Fe
The element which is most easily mixed and difficult to remove as an impurity element in the molten Al or Al alloy is Fe. Fe is easily mixed from fastening parts and shredder machines. However, since Al is an element that is easily oxidized, an oxidation refining process such as a converter in the steel industry cannot be applied, and it is difficult to remove Fe. In the impurity removal method, Fe can be efficiently removed from the Al or Al alloy molten metal. Therefore, Fe can be reduced below the specified concentration of A5000 series (Al—Mg series alloy) defined by JIS, and horizontal recycling from the stretched material to the stretched material can be facilitated.

(2) Si
As an impurity element in the molten Al or Al alloy, Si is an element which is likely to be mixed next to Fe and difficult to remove. Si may be a mixture of castings and die-cast products in scrap and a mixture of silica sand containing SiO ₂ as a main component. In the impurity removal method, when Si is contained as an impurity of Al or Al alloy molten metal, an intermetallic compound containing Si and Mg is formed. Therefore, in the impurity removal method, Si can be efficiently removed from the Al or Al alloy molten metal.

(3) Mn, Co, Ti, V, Zr, Cr or a combination thereof As for the impurity element in Al or Al alloy molten metal, the impurity removal method also applies to Mn, Co, Ti, V, Zr, Cr or a combination thereof. In, an intermetallic compound containing Al and Mn, Co, Ti, V, Zr, Cr or a combination thereof is formed. Therefore, in the impurity removal method, the impurity element containing Mn, Co, Ti, V, Zr, Cr, or a combination thereof can be efficiently removed from the Al or Al alloy molten metal. In addition, Mn, Ti, V, Zr, and Cr are mixed as an additive element of the Al alloy, an element contained in the crystal grain refining material, metal, or the like. Co is an element contained in the battery and may be mixed from scrap in the future.

As the impurities that can be removed by the impurity removal method, various combinations can be selected from Fe, Si, Mn, Co, Ti, V, Zr, and Cr listed in the above (1) to (3). Impurities can be efficiently removed by forming and removing these combinations of intermetallic compounds. However, when Si is included in the intermetallic compound, Mg is also included in the intermetallic compound. Examples of intermetallic compounds to be removed include intermetallic compounds of Al, Fe, Mn, Co and Cr, intermetallic compounds of Mg and Si, and intermetallic compounds of Al, Ti, V and Zr. More specifically, Al ₁₃ Fe ₄ , Mg ₂ Si, Al ₆ Mn, Al ₉ Co ₂ , Al ₃ Ti, Al ₁₀ V, Al ₃ V, Al ₃ Zr and the like can be mentioned. Al ₁₃ Fe ₄ , Mg ₂ Si, Al ₆ Mn, Al ₉ Co ₂ , Al ₃ Ti, Al ₁₀ V, Al ₃ V, Al ₃ Zr, etc. are Fe, Si, Mn, Co, Ti, V, Zr And other metals of Cr may be included as a trace component.

Hereinafter, each process will be described.

<Mg addition process>
In the Mg addition step, Mg, which is an essential element such as a JIS-A5000 series Al alloy, is added to Al or Al alloy molten metal containing impurities and contained at a high concentration. When the Al or Al alloy molten metal contains Mg at a high concentration, the formation of an intermetallic compound of impurities in the Al—Mg based molten metal is promoted. Therefore, there is no need to mix unnecessary impurities to generate intermetallic compounds as was done in the past, and metal elements that are difficult to remove in the Al recycling process are efficiently removed from the Al-Mg melt. can do. Moreover, since Mg is not an impurity, a step of removing Mg is unnecessary, and the molten metal can be diluted and used for an Al product.

The following effects can be mentioned as an effect by the said Mg addition process.
(A) Since the liquidus temperature is lowered, the molten metal can be held at a low temperature, and the production of the compound is promoted.
(B) The formation of the compound is promoted by increasing the activity of the impurity element by Mg.
(C) The added Mg directly reacts with the impurity element to form an intermetallic compound.
Due to the effects of the above (a), (b), (c), or a combination thereof, impurities can be made into an intermetallic compound in the molten metal.

For example, it is considered that intermetallic compound formation is promoted by the effects (a) and (b) above for the removal of Fe and the effects (a) and (c) for the removal of Si. Other impurity elements can also be removed by any of the effects (a) to (c).

In the Mg addition step, Mg or Mg alloy is added to Al or Al alloy molten metal containing impurities. Examples of the Mg alloy include JIS-MC5 and JIS-MDC2A.

The lower limit of the Mg concentration is 11% by mass, preferably 14% by mass, more preferably 17% by mass, and still more preferably 20% by mass or more based on the Al or Al alloy molten metal containing impurities. If the lower limit of the concentration is less than 11% by mass, the effects (a) to (c) described above cannot be sufficiently obtained, and the intermetallic compound may not be sufficiently produced.

Further, the upper limit of the Mg concentration is not particularly limited, but when the Mg concentration increases, the amount of dilution increases and the cost increases. Therefore, 50% of the molten Al or Al alloy containing impurities from the economical viewpoint. % By mass is preferable, 40% by mass is more preferable, 30% by mass is further preferable, and 25% by mass is particularly preferable.

<Temperature holding process>
In the temperature holding step, the molten metal after the adding step is held in a temperature range of 470 ° C. or higher and 650 ° C. or lower for 5 minutes or more, thereby promoting the generation of an intermetallic compound containing an impurity element.

The liquidus temperature of the Al—Mg binary phase diagram of an Al—Mg alloy having an Mg concentration of 11 mass% or more and 50 mass% or less in the Al—Mg alloy is expressed by the following equation.
(1) When the Mg concentration in the Al—Mg-based alloy is 11 mass% or more and less than 35 mass% Liquidus temperature (° C.) of the Al—Mg binary phase diagram = −6.6 × Mg concentration (mass%) +680 (2) When the Mg concentration in the Al—Mg alloy is 35% by mass or more and 50% by mass or less The liquidus temperature (° C.) of the Al—Mg binary system phase diagram = 450

This inventor prescribed | regulated the retention temperature of a molten metal from a viewpoint of the production | generation of an intermetallic compound, and the separability from a molten metal. The lower limit of the holding temperature is 470 ° C., preferably the higher of 470 ° C. and the liquidus temperature −20 ° C., more preferably the higher of 470 ° C. and the liquidus temperature −10 ° C. It is. This is because when the holding temperature is lower than 470 ° C., the fluidity of the molten metal is lowered and it is difficult to stably hold the molten metal.
The holding temperature is preferably the higher of 470 ° C. and the liquidus temperature −20 ° C., more preferably the higher of 470 ° C. and the liquidus temperature −10 ° C. Since the temperature is used as a reference, the production amount of solid Al can be kept low, and the intermetallic compound can be efficiently separated without reducing the yield of the molten metal.
On the other hand, the upper limit of the holding temperature is 650 ° C, preferably 630 ° C, and more preferably 600 ° C. This is because when the holding temperature exceeds 650 ° C., an intermetallic compound is not generated, and as a result, it may be difficult to reduce the impurity concentration.

The lower limit of the holding time is preferably 5 minutes, more preferably 10 minutes, and even more preferably 20 minutes for coarse growth of the compound. On the other hand, the upper limit of the holding time is not particularly limited, but 150 minutes is preferable for efficient processing.

<Cooling process>
In the cooling step, the molten metal is cooled to a temperature at which only the intermetallic compound is crystallized after the holding step. The intermetallic compound in the molten metal can be crystallized by the cooling step. As the cooling means, the entire molten metal may be cooled, or a cooling pipe to which a cooling medium is supplied may be inserted into the molten metal to locally lower the temperature of the molten metal. When the cooling pipe to which the cooling medium is supplied is used, the cooling medium is not particularly limited, and water is an example.

<Intermetallic compound separation process>
In the intermetallic compound separation step, the intermetallic compound produced in the holding step is separated from the molten metal. By separating and removing the intermetallic compound, it can be efficiently removed from the molten metal to the outside of the system, so that impurities can be efficiently reduced below the allowable concentration of the Al alloy specified by JIS. Examples of the separating means include filtration with a heat-resistant filter, standing of the molten metal, and centrifugal separation of the molten metal. In addition, when the molten metal contains Fe as an impurity and the intermetallic compound is Al ₁₃ Fe ₄ which is an Al—Fe-based intermetallic compound, since Al ₁₃ Fe ₄ is paramagnetic, it is adsorbed and fixed by a magnet. You can also. By these methods, Al ₁₃ Fe ₄ can be efficiently removed out of the system from the Al—Mg melt.

[Crystal crystallization of intermetallic compounds by cooling pipe]
When using the cooling pipe to which the cooling medium is supplied, the cooling pipe to which the cooling medium is supplied is inserted into the molten metal as a separation step, and is locally held at 470 ° C. or more and 650 ° C. or less on the surface of the cooling pipe. It is also possible to crystallize the intermetallic compound. By using the cooling pipe to crystallize the intermetallic compound on the surface of the cooling pipe, the intermetallic compound can be efficiently crystallized without cooling the entire molten metal and lowering the temperature.

[Filtration with heat-resistant filter]
By filtering the molten metal using a heat resistant filter, the intermetallic compound can be easily and efficiently removed from the molten metal. An example of the heat resistant filter is a refractory filter. A refractory filter refers to a filter made of a chemically stable oxide that can withstand high temperatures. Examples of the oxide include magnesia, alumina, silica, mullite, zirconia, and the like. Examples of the refractory filter include a ceramic foam filter and a tube filter, and a molten metal filtration device including the refractory filter can be used.

[Lease of molten metal]
By allowing the molten metal to stand, an intermetallic compound having a specific gravity different from that of the molten metal is levitated or settled. By separating by allowing the molten metal to stand, the intermetallic compound can be removed at low cost. And, after removing the floating substance of the intermetallic compound, by tilting the container in the state where the precipitate of the intermetallic compound remains, the method of collecting only the supernatant, the method of sucking only the supernatant from above with a suction tube, etc. Collect only molten metal with low impurity concentration.

[Centrifuged molten metal]
Moreover, an intermetallic compound can be efficiently removed by collecting an intermetallic compound having a large specific gravity from the molten metal using a centrifuge. After centrifugation, only the molten metal with a low impurity concentration is recovered.

[Floating separation of intermetallic compounds]
In the separation step, an inert gas containing N ₂ gas, Ar gas or He gas, chlorine gas, flux, or a combination thereof is introduced into the molten metal, and the intermetallic compound is introduced into the bubbles, flux or It can also be removed by floating and separating after adsorbing to these combinations. The intermetallic compound is floated and separated, and the intermetallic compound is scraped and removed using a jig or the like, so that only the molten metal having a low impurity concentration can be efficiently recovered. As the flux, for example, a mixture of two or more of NaCl, KCl, and MgCl ₂ can be used.

By combining the above steps, it is possible to obtain an Al—Mg molten metal having a low impurity concentration.

<Dilution process>
When the Mg addition step, the temperature holding step, the cooling step, and the intermetallic compound separation step are finished, the molten metal with a high concentration of Mg after the removal of the intermetallic compound is pure aluminum melted in advance or aluminum with a low Mg concentration. It can be used after being mixed with scrap (for example, 1000 series) and diluted to the Mg reference concentration of A5000 series (Al-Mg series alloy) defined by JIS. The dilution step is a step of diluting the molten metal after removal of the intermetallic compound containing a high concentration of Mg so that the Mg concentration is equal to or lower than the standard concentration of the JIS-A5000 system. Thus, since Mg is not an impurity, the process of removing is unnecessary, and the molten metal can be diluted and used for Al products. Further, by holding the molten metal after removal of the intermetallic compound containing high concentration of Mg under vacuum, Mg having a high vapor pressure can be evaporated, and an Al—Mg based molten metal having a low Mg concentration can be obtained.

It should be noted that the molten metal after removal of the intermetallic compound containing high concentration of Mg can be used as an Mg intermediate alloy by solidifying with a mold or the like.

The impurity removal method can efficiently remove impurities that are mixed in Al or Al alloy and are difficult to remove from the molten metal. Impurities are removed by isolating the produced intermetallic compounds by containing Mg, which is an essential element in a JIS-A5000 series Al alloy or the like in a high concentration to promote compounding of impurities. The present invention does not require a step of mixing unnecessary impurities in order to generate an intermetallic compound as conventionally performed, and can improve the yield.

According to the impurity removal method, metal elements that are difficult to remove in the Al recycling process can be efficiently reduced below the allowable concentration of the wrought material, so horizontal recycling from the wrought material to the wrought material is possible. Can be realized.

The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is not limited to the configuration of the embodiment described above, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[Example 1]
As shown in Table 1, 0.12 kg of molten Al—Fe alloy was melted at 700 ° C. so that the concentration of Fe was 1.00% by mass after addition of Mg. Next, after adding Mg so that the density | concentration with respect to a molten metal might be 20 mass%, the temperature of the molten metal was lowered | hung to 560 degreeC, hold | maintained for 35 minutes, and left still. Next, the crucible containing the molten metal was taken out of the furnace and allowed to cool. After the molten metal was solidified, the lower part of the ingot was cut, and the Fe concentration in the upper part of the sample was analyzed by ICP emission spectrometry.

[Examples 2 to 16]
The impurity removal treatment of Examples 2 to 16 was performed in the same manner as in Example 1 except that the Mg concentration, holding temperature, and holding time were changed as shown in Table 1. Next, the molten alloy after the impurity removal treatment was collected, and the concentration of the impurity element after the impurity removal treatment was measured by ICP emission spectroscopy.

[Example 17]
After melting the Al—Fe—Si alloy at 700 ° C., Mg is added, and finally 1.5 kg of Al alloy containing 30% by mass of Mg, 1.00% by mass of Fe and 1.00% by mass of Si is prepared. did. Next, the temperature of the molten metal was lowered to 550 ° C. and held for 6 minutes. Next, the molten metal was filtered while pressurizing with an inert gas using a refractory filter. After the molten metal solidified, the ingot after filtration was cut, and the Fe and Si concentrations were analyzed by ICP emission spectrometry.

These evaluation results are shown in Table 1.

[Evaluation results]
As shown in Table 1, Examples 1 to 5 in which the molten metal was maintained in a temperature range of 470 ° C. or more and 650 ° C. or less, the Mg concentration was 11% by mass or more, and the separation step was performed by standing, Also, Fe was sufficiently removed. Further, as in Examples 1 to 5, when the impurity in the molten Al or Al alloy is Fe, by changing the treatment conditions of the impurity removal method, the JIS-A5000 series used as the wrought material can be used. It was shown that it can respond widely to the reference value of Fe.
As in Examples 1 to 5, the molten metal was held in a temperature range of 470 ° C. to 650 ° C., the Mg concentration was 11% by mass, and the separation step was performed by standing. In Example 7, Si was sufficiently removed. In all of Examples 8 to 10, Mn was sufficiently removed. In all of Examples 11 to 12, Ti was sufficiently removed. In all of Examples 13 to 14, Cr was sufficiently removed. In Example 15, V was sufficiently removed. In Example 16, Co was sufficiently removed.
Further, Example 17 in which a molten metal containing an Al—Fe—Si alloy and having an Mg concentration of 11% by mass or more was held in a temperature range of 470 ° C. or more and 650 ° C. or less and the separation step was performed using a heat resistant filter is as follows. , Fe and Si were sufficiently removed.

The results of Examples 1 to 17 show that an excellent removal effect can be obtained for all impurities of Fe, Si, Mn, Co, Ti, V, and Cr having different solubility with respect to the Al molten metal. It was. Moreover, since Zr is an element in the same group as Ti, it can be estimated that an excellent removal effect can be obtained for Zr by the impurity removal method of the present invention.

As described above, the impurity removal method of the present invention can efficiently remove impurities that are mixed in Al or Al alloy and are difficult to remove from the molten metal. In addition, the present invention does not require a step of mixing unnecessary impurities to generate an intermetallic compound as conventionally performed, and can improve the yield.

The impurity removal method of the present invention can efficiently reduce metal elements that are difficult to remove in the Al recycling process to below the allowable concentration of the wrought material, so horizontal recycling from Al wrought material to wrought material is possible. Can be realized.

Claims

Adding Mg or Mg alloy into Al or Al alloy molten metal containing impurities;
Maintaining the molten metal after the addition step in a temperature range of 470 ° C. or more and 650 ° C. or less;
Separating the intermetallic compound produced in the holding step from the molten metal,
The impurity removal method whose Mg density | concentration in the said addition process is 11 mass% or more with respect to the said molten metal.
The method for removing impurities according to claim 1, wherein the holding time of the holding step is 5 minutes or more.
The impurities include Fe;
The impurity removal method according to claim 1, wherein the intermetallic compound contains Al and Fe.
The impurities include Si;
The impurity removal method according to claim 1, wherein the intermetallic compound contains Mg and Si.
The impurities include Mn, Co, Ti, V, Zr, Cr or combinations thereof,
The impurity removal method according to claim 1, wherein the intermetallic compound contains Al and Mn, Co, Ti, V, Zr, Cr, or a combination thereof.
The impurity removal according to any one of claims 1 to 5, wherein a cooling pipe to which a cooling medium is supplied in the separation step is inserted into the molten metal, and the intermetallic compound is crystallized on the surface of the cooling pipe. Method.
The impurity removal method according to any one of claims 1 to 5, wherein the molten metal is filtered by a heat-resistant filter in the separation step.
The impurity removal method according to any one of claims 1 to 5, wherein the intermetallic compound is allowed to settle or float by allowing the molten metal to stand in the separation step.
The impurity removal method according to any one of claims 1 to 5, wherein the molten metal is centrifuged in the separation step.
In the separation step, an inert gas containing N 2 gas, Ar gas or He gas, chlorine gas, flux, or a combination thereof is introduced into the molten metal, and the intermetallic compound is introduced into the bubbles, flux or The impurity removal method according to any one of claims 1 to 5, wherein the impurity is removed by floating separation after being adsorbed by the combination.