KR20230088769A - Impurity removal method and ingot manufacturing method - Google Patents

Abstract

An object of the present invention is to provide an impurity removal method capable of efficiently removing impurities that are mixed in aluminum or an aluminum alloy and are difficult to remove. An impurity removal method according to one aspect of the present invention includes a step of mixing Mg or an Mg alloy with a molten metal containing aluminum or an aluminum alloy and impurities, and a step of maintaining the temperature of the molten metal after the mixing step within a solid-liquid coexistence temperature range. and a step of separating the solid aluminum generated in the holding step and the intermetallic compound containing the impurities from or in the molten metal in the solid-liquid coexistence temperature range, and stirring the molten metal in the separation step or squeeze

Description

Impurity removal method and ingot manufacturing method

The present invention relates to a method for removing impurities and a method for producing an ingot.

BACKGROUND OF THE INVENTION [0002] In recent years, the weight reduction of automobiles and the like is progressing all over the world due to the social demand for carbon dioxide emission control, and the demand for aluminum is expected to increase in the future. Therefore, it is expected that the amount of aluminum scrap will increase in the future along with the increase in demand. Generally, aluminum is regarded as a metal material with excellent recyclability. Many aluminum products made of aluminum wrought materials, including aluminum cans, are discarded and then remelted and recycled into new products. However, impurities adhere to the aluminum product after disposal, and the concentration of the impurity element gradually increases as recycling is repeated. Therefore, it is common for aluminum products after disposal to be recycled in a cascade into products with less stringent component specifications.

As a technique for suppressing the incorporation of impurities into aluminum, advancement of the fractionation technique after shredding is being pursued. However, since it is difficult to completely remove deposits, a technology for removing impurities from aluminum or aluminum alloy molten metal is ultimately required.

A lot of reports have been made on techniques for removing impurities from aluminum or aluminum alloy molten metal, and as a technique for removing Fe, which is particularly difficult to remove, Mn, which is an impurity, is dared to be added to crystallize an Al-Fe-Mn-based intermetallic compound, Techniques for removing the intermetallic compound by centrifugation, suction, or the like have been proposed (see Japanese Unexamined Patent Publication Nos. 8-35021 and 70666).

Further, as a technique for reducing the impurity concentration in aluminum or aluminum alloy molten metal, a technique using a three-layer electrolytic refining method or a segregation method in a step of producing aluminum ingot is disclosed (Mertier, Vol. 33 (1994), No. 1).

Further, after adding Mg or Mg alloy to an aluminum or aluminum alloy molten metal containing impurities, the molten metal is cooled to a temperature at which only intermetallic compounds are crystallized to crystallize intermetallic compounds containing impurities in the molten metal, thereby crystallizing the metal A method for separating liver compounds from molten metal has also been proposed (see Japanese Unexamined Patent Publication No. 2019-183265).

Japanese Unexamined Patent Publication No. 8-35021 Japanese Unexamined Patent Publication No. 7-70666 Japanese Unexamined Patent Publication No. 2019-183265

Kondo et al., Materia, 1994, Vol. 33, no. 1, 62-68

However, in the techniques described in Patent Literature 1 and Patent Literature 2, the added Mn may increase as an impurity. Further, the technique described in Non-Patent Document 1 can in principle remove Fe, but as a method for refining scrap containing a large amount of impurity elements, the yield may be low. In addition, the three-layer electrolytic refining method has poor profitability in regions where electricity costs are high, and the segregation method may have a lower yield as the impurity concentration of the raw material increases. As such, the prior art is not sufficient as a method for recycling aluminum scrap containing a large amount of impurities recovered from the market.

On the other hand, according to the technique described in Patent Literature 3, horizontal recycling from a wrought material to a wrought material of aluminum can be realized to a certain extent. However, as a result of intensive examination by the present inventors, it has been found that there is room for further improvement in the removal efficiency of impurities and the like with respect to the technology described in Patent Literature 3.

The present invention has been made in view of such a situation, and an object of the present invention is to provide an impurity removal method capable of efficiently removing impurities that have been mixed in aluminum or an aluminum alloy and are considered difficult to remove.

The inventors of the present invention, after mixing Mg, which is an essential element in JIS-A5000 series aluminum alloy, etc., with an aluminum or aluminum alloy molten metal containing impurities, intermetallic compounds containing solid aluminum and impurities in or from the molten metal. It was discovered that impurities can be efficiently removed by separation, and the present invention was completed.

An impurity removal method according to one aspect of the present invention includes a step of mixing Mg or an Mg alloy with a molten metal containing aluminum or an aluminum alloy and impurities, and setting the temperature of the molten metal after the mixing step to a solid-liquid coexistence temperature range. and a step of separating an intermetallic compound containing solid aluminum and the impurities generated in the holding step from or in the molten metal in the solid-liquid coexistence temperature range, In the separation process, the molten metal is stirred or compressed.

The impurity removal method according to one aspect of the present invention can efficiently remove impurities that are difficult to remove because they are mixed in aluminum or an aluminum alloy from the molten metal.

1 is a flowchart showing a method for removing impurities according to an embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view showing an example of a stirring procedure in a separation step of the impurity removal method of FIG. 1 .
Fig. 3 is a schematic cross-sectional view showing an example of a pressing procedure in a separation step of the impurity removal method of Fig. 1;
4 is a flowchart showing a method for manufacturing an ingot according to an embodiment of the present invention.

[Description of Embodiments of the Invention]

Embodiments of the present invention are first listed and described.

An impurity removal method according to one aspect of the present invention includes a step of mixing Mg or an Mg alloy with a molten metal containing aluminum or an aluminum alloy and impurities, and a step of maintaining the temperature of the molten metal after the mixing step within a solid-liquid coexistence temperature range. and a step of separating the solid aluminum generated in the holding step and the intermetallic compound containing the impurities from or in the molten metal in the solid-liquid coexistence temperature range, and stirring the molten metal in the separation step or squeeze

The method for removing impurities can efficiently separate solid aluminum and intermetallic compounds containing impurities from or from the molten metal by stirring or compressing the molten metal in the solid-liquid coexistence temperature range in the separation step. there is. Therefore, according to the method for removing impurities, it is possible to efficiently remove impurities that are difficult to remove because they are mixed in aluminum or an aluminum alloy.

As content of Mg in the said molten metal after the said mixing process, 5 mass % or more is preferable. In this way, when the content of Mg in the molten metal after the mixing step is equal to or more than the lower limit, the intermetallic compound can be easily and efficiently generated in the molten metal.

In the separation step, the solid aluminum and the intermetallic compound may be unevenly distributed in the molten metal. In this way, in the separation step, by allowing the solid aluminum and the intermetallic compound to be unevenly distributed in the molten metal, the impurities can be easily removed.

It is only necessary that the solid aluminum contains α-aluminum dendrites, and the α-aluminum dendrites are destroyed in the separation step. In this way, the solid aluminum contains α-aluminum dendrites, and the intermetallic compound can be easily separated from the molten metal by destroying the α-aluminum dendrites in the separation step.

A method for manufacturing an ingot according to another embodiment of the present invention includes a step of mixing Mg or an Mg alloy with a molten metal containing aluminum or an aluminum alloy and impurities, and the temperature of the molten metal after the mixing step is brought into a solid-liquid coexistence temperature range. A step of maintaining; a step of separating the intermetallic compound containing solid aluminum and the impurities generated in the holding step from or in the molten metal in the solid-liquid coexistence temperature range; A step of solidifying is provided, and in the separation step, the molten metal is stirred or compressed.

In the method for producing the ingot, impurities can be easily removed from the ingot obtained by efficiently separating solid aluminum and an intermetallic compound containing impurities from the molten metal in the separation step. In the method for producing the ingot, an ingot having a reduced content of impurities can be produced by efficiently separating solid aluminum and an intermetallic compound containing impurities from the molten metal in the separation step.

On the other hand, in the present invention, "solid-liquid coexistence temperature" means a temperature that is lower than the liquidus temperature and higher than the solidus temperature. That is, in the present invention, the "solid-liquid coexistence temperature" is the temperature at which solid aluminum (α-aluminum) and liquid aluminum coexist.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail, referring drawings.

[Impurity removal method]

In the impurity removal method, impurities that are mixed in aluminum or an aluminum alloy and are difficult to remove can be removed using Mg (magnesium), which is an essential element of the JIS-A5000 system. The impurity removal method can remove impurities such as metal elements that are difficult to remove in the aluminum recycling process. In the impurity removal method, by incorporating Mg, which is an essential element in aluminum alloys of the JIS-A5000 series, etc. into the molten metal, intermetallic compounds of impurities are promoted, and the resulting intermetallic compounds are separated, thereby removing impurities. there is. The impurity removal method does not require the addition of additional impurities in order to generate the intermetallic compound. In addition, since the impurity removal method includes a separation step (S3) described later, the addition amount of Mg can be suppressed to a relatively low level.

As shown in FIG. 1 , the impurity removal method includes a step of mixing Mg or an Mg alloy with a molten metal containing aluminum or an aluminum alloy and impurities (mixing step S1), and the molten metal after the mixing step S1. A step of maintaining the temperature within the solid-liquid coexistence temperature range (maintaining step (S2)), and the intermetallic compound containing solid aluminum and impurities generated in the holding step (S2) in the solid-liquid coexistence temperature range in the molten metal or in the A step of separating from the molten metal (separation step (S3)) is provided. In the impurity removal method, in the separation step (S3), the molten metal is stirred or compressed.

〔impurities〕

As the impurity, either (1) Fe (iron), and (2) Mn (manganese), Co (cobalt), Ti (titanium), V (vanadium), Zr (zirconium), Cr (chromium), or can take both sides. As said impurity, you may contain 1 type, or 2 or more types of arbitrary elements included in said (1) and said (2). When Fe is included as the impurity, the intermetallic compound separated in the separation step (S3) contains aluminum and Fe. When Mn, Co, Ti, V, Zr, Cr or a combination thereof is included as the impurity, the intermetallic compound separated in the separation step (S3) is aluminum, Mn, Co, Ti, V, Zr, Cr or a combination thereof.

[Fe]

Fe is an element that is most easily mixed as an impurity element in molten metal containing aluminum or an aluminum alloy and is difficult to remove. Fe is easily incorporated from fastening parts, shredders, and the like. On the other hand, since aluminum is an element easily oxidized and cannot undergo oxidative refining like a converter in the steel industry, it is considered difficult to remove Fe. Since the impurity removal method can efficiently remove Fe from a molten metal containing aluminum and Mg (Al-Mg-based molten metal), horizontal recycling from a wrought material to a wrought material of aluminum can be easily realized.

[Mn, Co, Ti, V, Zr, Cr or a combination thereof]

Mn, Ti, V, Zr, and Cr are incorporated as additive elements in aluminum alloys, grain refinement materials, metals, and the like. Also, Co is an element included in batteries and may be mixed in from scrap. According to the impurity removal method, when Mn, Co, Ti, V, Zr, Cr or a combination thereof is included as the impurity, aluminum and Mn, Co, Ti, V, Zr are removed by the holding step (S2). , Cr, or a combination thereof is thought to be easily produced. In addition, according to the impurity removal method, it is considered that impurities containing Mn, Co, Ti, V, Zr, Cr or a combination thereof can be efficiently removed from the Al-Mg-based molten metal in the separation step (S3). .

(mixing process)

In the mixing step (S1), for example, Mg or an Mg alloy is added to the molten metal containing aluminum or an aluminum alloy and the impurities. More specifically, in the mixing step (S1), Mg or Mg alloy is added to the molten metal in which the aluminum scrap is melted.

Mg is an essential element in JIS-A5000 system aluminum alloys and the like. When the molten metal containing aluminum or aluminum alloy properly contains Mg, the formation of intermetallic compounds containing the above impurities in the Al-Mg-based molten metal is promoted. According to the impurity removal method, it is not necessary to intimidate unnecessary impurities in order to generate an intermetallic compound, as has been conventionally done. That is, in the mixing step (S1), it is not necessary to mix components other than Mg or Mg alloy with the molten metal. In addition, since Mg is not an impurity, the impurity removal method does not require a step for removing Mg. Therefore, in the impurity removal method, for example, the molten metal from which the impurities are removed can be diluted as necessary and used for aluminum recycling. Meanwhile, the dilution procedure (dilution process) of the molten metal after the impurities are removed will be described later. Examples of the Mg alloy to be mixed in the mixing step (S1) include JIS-MC5 and JIS-MDC2A.

Examples of the effect of mixing Mg or Mg alloy in the mixing step (S1) include the following (a) to (c).

(a) By lowering the liquidus temperature, the molten metal can be maintained at a low temperature, and the formation of intermetallic compounds is promoted.

(b) When Mg increases the activity of an impurity element, the formation of an intermetallic compound is promoted.

(c) Mg directly reacts with impurity elements to form intermetallic compounds.

For example, when Fe is included as the impurity, it is estimated that the removal of Fe is promoted by the effects of (a) and (b) above. Regarding impurities other than Fe, the formation of an intermetallic compound is promoted by any of the above effects (a) to (c) or a combination of the effects (a) to (c), and the intermetallic compound is removed from the molten metal. It is assumed that it can be effectively removed.

The lower limit of the Mg content in the molten metal after the mixing step (S1) is preferably 5% by mass, more preferably 8% by mass, and still more preferably 10% by mass. If the content of Mg is less than the lower limit, there is a possibility that the liquidus temperature cannot be lowered sufficiently. On the other hand, the upper limit of the content of Mg in the molten metal after the mixing step (S1) is not particularly limited, but the amount of dilution in the dilution step described later increases to suppress an increase in the cost required for aluminum recycling. From a viewpoint, for example, 30 mass % is preferable, 20 mass % is more preferable, and 15 mass % is still more preferable.

(maintenance process)

In the holding step (S2), the molten metal after the mixing step (S1) is maintained in a solid-liquid coexistence state. In the impurity removal method, by maintaining the molten metal in a solid-liquid coexistence state in the holding step (S2), the intermetallic compound containing the impurity can be sufficiently separated in a separation step (S3) described later. Since the impurity removal method needs only to maintain the molten metal in a solid-liquid coexistence state, the content of Mg in the molten metal can be made relatively small, so that the molten metal after the impurities have been removed can be diluted. , aluminum scrap with a low Mg concentration, etc.) can be reduced.

In the holding step (S2), impurities contained in the molten metal are generated as intermetallic compounds by maintaining the temperature of the molten metal after the mixing step (S1) within the solid-liquid coexistence temperature range. On the other hand, when the temperature of the molten metal after the mixing step (S1) is maintained within the solid-liquid coexistence temperature range, solid aluminum is produced together with the intermetallic compound. Primary crystals of this solid aluminum show a dendrite form. The solidification of the solid aluminum proceeds as the generation of α-aluminum dendrites. This α-aluminum dendrite is of high purity. These α-aluminum dendrites grow granular. That is, the solid aluminum includes α-aluminum dendrites and grains from which α-aluminum dendrites have grown. The total content ratio of the α-aluminum dendrite and the granular material in the solid aluminum is very large. The intermetallic compound is generated in the vicinity of the solid-liquid interface and is captured in gaps between α-aluminum dendrites (between α-aluminum dendrites). In addition, the intermetallic compound is introduced into the granular body during the growth of α-aluminum dendrites.

In the holding step (S2), the molten metal after the mixing step (S1) is cooled to a temperature range lower than the liquidus temperature and higher than the solidus temperature. When the Mg content [mass%] in the molten metal is C, the lower limit of the holding temperature T [°C] of the molten metal in the holding step (S2) is, for example, in the case of C≤19, T ≥-10.8C+660, and in the case of C>19, T≥450. On the other hand, the upper limit of the holding temperature T [° C.] of the molten metal in the holding step (S2) can be set to T<-5.9C+660 (provided that C≤35).

In the holding step (S2), it is preferable to maintain the molten metal after the mixing step (S1) in a solid-liquid coexistence temperature range in which the liquid phase ratio is 60% or more. Specifically, as the holding temperature T [°C] of the molten metal in the holding step (S2), T≥-7.3C+660 (however, in the case of C≤35) is preferable. If the liquid phase ratio is less than the lower limit, the solid phase ratio becomes too large, and there is a risk that it becomes difficult to stir or press the molten metal in the separation step (S3).

(separation process)

In the separation step (S3), the intermetallic compound is separated from or in the molten metal together with the solid aluminum (combined with the solid aluminum).

In the separation step (S3), the molten metal maintained in the solid-liquid coexistence temperature range in the holding step (S2) is stirred or compressed. In the separation step (S3), the molten metal may be stirred or compressed after the molten metal is maintained in the solid-liquid coexistence temperature range, or the molten metal may be stirred or compressed before the molten metal reaches the solid-liquid coexistence temperature.

In the separation step (S3), it is preferable to unevenly distribute the intermetallic compound containing the solid aluminum and the impurities generated in the holding step (S2) in the molten metal. In the impurity removal method, for example, the solid aluminum and the intermetallic compound can be unevenly distributed in the molten metal by stirring or pressing the molten metal stored in the furnace. According to this configuration, the impurities can be easily removed.

In the separation step (S3), it is preferable to destroy α-aluminum dendrites included in the solid aluminum. As described above, the intermetallic compound containing the impurity is captured in the gap between α-aluminum dendrites in the solid-liquid coexistence temperature range. Therefore, the intermetallic compound can be released from the α-aluminum dendrites by destroying the α-aluminum dendrites in the separation step (S3). Since this intermetallic compound usually has a higher specific gravity than that of molten aluminum (liquid aluminum), the intermetallic compound can be easily separated to the bottom side of the molten metal by destroying α-aluminum dendrites.

In the separation step (S3), it is preferable to destroy the above-described granular bodies included in the solid aluminum together with the α-aluminum dendrites. As described above, the intermetallic compound is introduced into the granular body during the growth of α-aluminum dendrites. Therefore, by destroying the granular material in the separation step (S3), the intermetallic compound introduced into the granular material can be easily and reliably released from the granular material.

Hereinafter, each of the steps of stirring and compressing the molten metal in the separation step (S3) will be described. On the other hand, in the separation step (S3), only one of the agitation and the compression bonding may be performed, but performing both the agitation and the compression compression is not excluded.

[Stirring procedure]

In the case of stirring the molten metal in the separation step (S3), for example, as shown in FIG. 2 , the molten metal X held in the furnace Y in the solid-liquid coexistence temperature range is stirred by the stirrer 10. The stirring means is not particularly limited as long as a stirring force capable of destroying the α-aluminum dendrite (D) is obtained, and for example, mechanical stirring using a rod or a stirring blade, and electromagnetic stirring using a stirrer Stirring, stirring by blowing in an inert gas, etc. are mentioned (in FIG. 2, mechanical stirring using a stirring blade is shown).

By stirring the molten metal (X) in the separation step (S3), the α-aluminum dendrites (D) and the above-mentioned granular bodies are destroyed, and the α-aluminum dendrites (D) are trapped between gaps, or the granular bodies are Intermetallic compound (I) containing impurities introduced into the inside can be released. Examples of the intermetallic compound (I) include Al ₃ Fe when the impurity is Fe, Al ₆ Mn when the impurity is Mn, Al ₃ Co when the impurity is Co, and Ti when the impurity is Ti. , Al ₃ Ti, Al ₃ V when the impurity is V, Al ₃ Zr when the impurity is Zr, and Al ₇ Cr when the impurity is Cr. Since these intermetallic compounds have a higher specific gravity than liquid aluminum, when the molten metal (X) is allowed to stand after stirring, they settle to the bottom of the molten metal (X) together with the α-aluminum dendrites (D) and the above-mentioned granular material. In this way, the intermetallic compound (I) can be unevenly distributed at the bottom of the molten metal (X) together with the α-aluminum dendrite (D) and the granular material. On the other hand, it is preferable to perform the stilling after stirring in a state where the temperature of the molten metal (X) is maintained within the solid-liquid coexistence temperature range. In addition, it is more preferable to keep the temperature of the molten metal (X) within the solid-liquid coexistence temperature range and below the temperature at the time of the agitation in the stilling after the stirring.

[Compression procedure]

In the case of compressing the molten metal in the separation step (S3), as shown in FIG. 3, for example, the molten metal X held in the furnace Y in the solid-liquid coexistence temperature range is pressed from the liquid surface side to the compression plate 20. do. As the pressing plate 20, for example, one having a plurality of holes (not shown) capable of passing the molten metal X in the plate thickness direction can be used.

By compressing the molten metal (X) in the separation step (S3), the α-aluminum dendrites (D) and the above-mentioned granular bodies are destroyed, so that the gaps of the α-aluminum dendrites (D) are trapped, or the granular bodies are While releasing the intermetallic compound (I) containing impurities introduced into the inside, the intermetallic compound (I) can be localized at the bottom of the molten metal (X) together with the α-aluminum dendrite (D) and the above-mentioned granular body. there is. As a result, the intermetallic compound (I) can be pressed at the bottom side of the furnace (Y) together with the α-aluminum dendrite (D) and the granular material to be solidified.

On the other hand, as a method of compressing the molten metal in the separation step (S3), it is also possible to use a method other than that described in FIG. 3 . For example, in the separation step (S3), it is also possible to adopt a configuration in which liquid aluminum is discharged out of the furnace while leaving the intermetallic compound and α-aluminum dendrites in the furnace by pressing the molten metal from the liquid surface side.

(dilution process)

Impurities are separated in the separation step (S3), and the molten metal after these impurities are further removed can be diluted and used for aluminum recycling. More specifically, liquid aluminum recovered after separating impurities in the separation step (S3) can be used for aluminum recycling by diluting. An aluminum recycling method in which a dilution step is added to the mixing step (S1), the holding step (S2), and the separation step (S3) described above is one embodiment of the present invention. In the dilution step, the molten metal from which the impurities have been removed through the separation step (S3) is mixed with industrial pure aluminum or aluminum scrap with a low Mg concentration (for example, JIS-A1000 series) to form A5000 series (specified by JIS). It is diluted to the Mg standard concentration of Al-Mg alloy).

In the dilution step, the Mg concentration of the molten metal containing the Mg added in the mixing step (S1) is diluted to a JIS-A5000 standard concentration or less. Since Mg is not an impurity, it does not need to be removed from the molten metal. In the aluminum recycling method, the diluted molten metal can be used for aluminum products by lowering the concentration of Mg in the dilution step. In the dilution step, it is also possible to lower the Mg concentration in the molten metal by evaporating Mg having a high vapor pressure by holding the molten metal containing a relatively high concentration of Mg under vacuum. In the dilution step, Mg can also be removed by blowing chlorine into the molten metal or by using a flux.

On the other hand, the molten metal after the separation step (S3) can also be used for reuse without going through the dilution step. For example, the molten metal may be solidified after removal of impurities and used as recycled metal, or it may be solidified in a state where intermetallic compound (I) is unevenly distributed, and a portion having a high concentration of impurities is selectively cut off to be used as recycled metal. You can do it. Further, in the process of utilizing the reclaimed metal, the molten metal may be diluted as needed. Further, the molten metal after the separation step (S3) can be separated and recovered by suction or the like, or used as an Mg intermediate alloy by hardening with a mold or the like.

In addition, after separating the high impurity concentration part from the ingot or the like obtained after the separation step (S3), the impurity removal method may be performed again on the high impurity concentration part. According to this structure, this part with high impurity concentration can be refined by the said impurity removal method. At this time, in performing the said impurity removal method, you may add aluminum scrap etc. newly. Yield can be improved also by these structures.

＜Advantages＞

In the impurity removal method, solid aluminum such as α-aluminum dendrite (D) and intermetallic compound (I) are separated by stirring or compressing the molten metal (X) in the solid-liquid coexistence temperature range in the separation step (S3). It can be efficiently separated from or in the molten metal (X). More specifically, within the solid-liquid coexistence temperature range, solid aluminum (α-aluminum), liquid aluminum, and intermetallic compound (I) are substantially uniformly dispersed in the molten metal X. In this state, the intermetallic compound (I) is trapped between the gaps between α-aluminum dendrites or is introduced into the above-mentioned granular body, and is difficult to remove. In contrast, the impurity removal method involves destroying the α-aluminum dendrites (D) and the granular bodies in the separation step (S3), thereby separating the intermetallic compound (I) from the α-aluminum dendrites (D) and the granular bodies. Together with, it can be efficiently separated from or in the molten metal (X). Therefore, according to the method for removing impurities, it is possible to efficiently remove impurities that are difficult to remove because they are mixed in aluminum or an aluminum alloy.

The impurity removal method involves incorporating Mg, which is an essential element in aluminum alloys of the JIS-A5000 system, etc. into molten metal (X) to promote intermetallic compounding of the impurities and separating the resulting intermetallic compound (I). by removing the impurities. In the impurity removal method, unnecessary impurities are not required to be mixed in order to produce the intermetallic compound (I) as has been conventionally done, and the yield can be improved.

According to the impurity removal method, metal elements that are considered difficult to remove can be efficiently removed in the aluminum recycling process, so that horizontal recycling from an aluminum wrought material to an aluminum wrought material can be realized.

In the impurity removal method, Mg or an Mg alloy is mixed with a molten metal containing aluminum or an aluminum alloy and impurities in the mixing step (S1). On the other hand, in the mixing step (S1), Cu, which is an essential element of JIS-A2000 series alloy, or Zn, which is an essential element of JIS-A7000 series alloy, is mixed with molten metal containing aluminum or aluminum alloy and impurities, In the same way, it is considered that the intermetallic compound containing solid aluminum and impurities can be separated from or in the molten metal in the separation step (S3). In the mixing step (S1), it is considered that Mg or Mg alloy, Cu or Cu alloy, or Zn or Zn alloy may be mixed alone or may be mixed in an arbitrary combination.

[Method of manufacturing ingot]

Next, a method for producing an ingot using the impurity removal method will be described. As shown in FIG. 4 , the ingot manufacturing method includes a step of mixing Mg or an Mg alloy with a molten metal containing aluminum or an aluminum alloy and impurities (mixing step S1), and the molten metal after the mixing step S1. A step of maintaining the temperature of within the solid-liquid coexistence temperature range (maintaining step (S2)), and intermetallic compounds containing solid aluminum and the impurities generated in the holding step (S2) in the solid-liquid coexistence temperature range in the molten metal. Alternatively, a step of separating from the molten metal (separation step (S3)) and a step of solidifying the molten metal after the separation step (S3) (solidification step (S4)) are provided. In the manufacturing method of the ingot, in the separation step (S3), the molten metal is stirred or compressed. The mixing step (S1), the holding step (S2), and the separation step (S3) in the ingot manufacturing method are the mixing step (S1), the holding step (S2), and the separation step in the impurity removal method of FIG. It can be carried out in the same procedure as (S3). Therefore, the description of the mixing step (S1), the holding step (S2) and the separation step (S3) is omitted.

(solidification process)

In the solidification step (S4), the molten metal after impurities are removed through the separation step (S3) may be solidified, or the molten metal in which impurities are unevenly distributed may be solidified by the separation step (S3). In the solidification step (S4), the diluted molten metal after the separation step (S3) may be solidified. In the case of solidifying the diluted molten metal in the solidification step (S4), the manufacturing method of the ingot may include the above-described dilution step between the separation step (S3) and the solidification step (S4).

＜Advantages＞

In the manufacturing method of the ingot, impurities can be easily removed from the obtained ingot by efficiently separating the solid aluminum and the intermetallic compound containing the impurities from the molten metal in the separation step (S3). In the method for producing the ingot, an ingot having a reduced content of impurities can be produced by efficiently separating the solid aluminum and the intermetallic compound containing the impurities from the molten metal in the separation step (S3).

[Other embodiments]

The above embodiment does not limit the configuration of the present invention. Therefore, in the above embodiment, omission, substitution, or addition of components of each part of the above embodiment is possible based on the description and common knowledge of the present specification, and they should all be construed as belonging to the scope of the present invention.

In the above embodiment, the configuration of separating the intermetallic compound containing α-aluminum dendrites and impurities from or from the molten metal in the separation step has been described. However, in the separation step, as long as solid aluminum and the intermetallic compound are separated, it is not required that the solid aluminum contain α-aluminum dendrites. Further, even when the solid aluminum contains α-aluminum dendrites, the α-aluminum dendrites need not be destroyed in the separation step.

Example

Hereinafter, the present invention will be described in detail based on examples, but the present invention is not limitedly interpreted based on the description of these examples.

[Example]

[No. One]

An aluminum alloy containing impurities and pure Mg were dissolved in graphite persimmon to prepare a molten metal containing Fe as an impurity and Si as another element (mixing step). Table 1 shows the content of various elements in this molten metal. Thereafter, this molten metal was pre-cooled to 641°C, and a stirring rod made of silicon nitride was inserted into the molten metal to start stirring of the molten metal. While performing this stirring, the molten metal was furnace-cooled to 602° C. or less, and then held within the solid-liquid coexistence temperature range (maintenance step). While the molten metal was maintained within the solid-liquid coexistence temperature range, the agitation was continued, and when the molten metal reached 591°C, the stirring rod was pulled out, and the molten metal was allowed to stand at the solid-liquid coexistence temperature of 590°C for 15 minutes (separation process). In this separation step, an intermetallic compound containing α-aluminum dendrite and Fe was separated toward the bottom side of the molten metal. After this separation process, the furnace was turned off and the molten metal was solidified to obtain an ingot. A part of the ingot was sampled from the upper part, and the concentration of Fe was analyzed by ICP emission spectrometry. The results of this analysis are shown in Table 1.

[No. 2]

An aluminum alloy containing impurities and pure Mg were dissolved in graphite persimmon to prepare a molten metal containing Fe as an impurity and Si as another element (mixing step). Table 1 shows the content of various elements in this molten metal. Thereafter, this molten metal was furnace-cooled to 594° C., which is the solid-liquid coexistence temperature (holding step), and after removing the persimmon from the furnace, the molten metal was quickly pressed from the liquid surface side using an iron jig (separation step). In this separation step, an intermetallic compound containing α-aluminum dendrite and Fe was separated toward the bottom side of the molten metal. After this separation step, an ingot was obtained by air-cooling and solidifying the molten metal. On the other hand, the jig used in the separation process was main-poured while being inserted into the molten metal. A part of the upper side of the jig of this ingot was taken out, and the concentration of Fe was analyzed by ICP emission spectrometry. The results of this analysis are shown in Table 1.

[No. 3]

An aluminum alloy containing impurities and pure Mg were dissolved in graphite persimmon, and a molten metal containing Mn as an impurity and Si, Cu and Zn as other elements was prepared (mixing step). Table 1 shows the content of various elements in this molten metal. After that, the molten metal was furnace-cooled to 593° C., which is the solid-liquid coexistence temperature (holding step), and after removing the persimmon from the furnace, the molten metal was quickly pressed from the liquid surface side using an iron jig (separation step). In this separation step, an intermetallic compound containing α-aluminum dendrite and Mn was separated toward the bottom side of the molten metal. After this separation step, an ingot was obtained by air-cooling and solidifying the molten metal. On the other hand, the jig used in the separation step was main-loaded while being inserted into the molten metal. A part of the upper side of the jig of this ingot was taken out, and the concentration of Mn was analyzed by ICP emission spectrometry. The results of this analysis are shown in Table 1.

[Comparative example]

[No. 4]

An aluminum alloy containing impurities and pure Mg were dissolved in graphite persimmon to prepare a molten metal containing Fe as an impurity and Si as another element (mixing step). Table 1 shows the content of various elements in this molten metal. Thereafter, the molten metal was air-cooled to 600° C., which is the solid-liquid coexistence temperature, and then left still for 15 minutes. After that, the furnace was turned off and the molten metal was solidified to obtain an ingot. A part of the ingot was sampled from the upper part, and the concentration of Fe was analyzed by ICP emission spectrometry. The results of this analysis are shown in Table 1.

[No. 5]

An aluminum alloy containing impurities and pure Mg were dissolved in graphite persimmon to prepare a molten metal containing Fe as an impurity and Si as another element (mixing step). Table 1 shows the content of various elements in this molten metal. Thereafter, this molten metal was furnace-cooled to 651° C., which is higher than the solid-liquid coexistence temperature, and while maintaining this temperature, a stirring bar made of silicon nitride was inserted into the molten metal to stir the molten metal. After this stirring, the molten metal was held at 651°C for 15 minutes. After that, the furnace was turned off and the molten metal was solidified to obtain an ingot. A part of the ingot was sampled from the upper part, and the concentration of Fe was analyzed by ICP emission spectrometry. The results of this analysis are shown in Table 1.

As shown in Table 1, No. 1 to No. In 3, impurities can be sufficiently removed by stirring or compressing the molten metal in the separation step while maintaining the temperature of the molten metal within the solid-liquid coexistence temperature range in the holding step. In contrast, No. In 4, since the molten metal is not stirred or compressed in the separation step, the impurity removal rate is insufficient. Also, No. In 5, when stirring the molten metal, the molten metal is not maintained in the solid-liquid coexistence temperature range, so the impurity removal rate is insufficient.

[No. 6]

From the Al-X binary system equilibrium diagram (where X = Mn), the solubility [mass%] of X in liquid aluminum at 700°C was read. Next, using the calculation software "FactSage 8.0", with respect to Al-10 mass% Mg-1 mass% X, the concentration of X in liquid aluminum in an equilibrium state at 590 ° C., which is a solid-liquid coexistence temperature [mass%] Calculated. These results are shown in Table 2.

[No. 7]

Except for X=Co, No. In the same way as in 6, the solubility [mass%] of X in liquid aluminum at 700 ° C. was read from the Al-X binary system equilibrium diagram, and further, solid-liquid coexistence with respect to Al-10 mass% Mg-1 mass% X The concentration [mass%] of X in liquid aluminum in an equilibrium state at a temperature of 590°C was calculated. These results are shown in Table 2.

[No. 8]

No. except that X = Ti. In the same way as in 6, the solubility [mass%] of X in liquid aluminum at 700 ° C. was read from the Al-X binary system equilibrium diagram, and further, solid-liquid coexistence with respect to Al-10 mass% Mg-1 mass% X The concentration [mass%] of X in liquid aluminum in an equilibrium state at a temperature of 590°C was calculated. These results are shown in Table 2.

[No. 9]

Except for X=V, No. In the same way as in 6, the solubility [mass%] of X in liquid aluminum at 700 ° C. was read from the Al-X binary system equilibrium diagram, and further, solid-liquid coexistence with respect to Al-10 mass% Mg-1 mass% X The concentration [mass%] of X in liquid aluminum in an equilibrium state at a temperature of 590°C was calculated. These results are shown in Table 2.

[No. 10]

Except for X=Zr, No. In the same way as in 6, the solubility [mass%] of X in liquid aluminum at 700 ° C. was read from the Al-X binary system equilibrium diagram, and further, solid-liquid coexistence with respect to Al-10 mass% Mg-1 mass% X The concentration [mass%] of X in liquid aluminum in an equilibrium state at a temperature of 590°C was calculated. These results are shown in Table 2.

[No. 11]

Except for X=Cr, No. In the same way as in 6, the solubility [mass%] of X in liquid aluminum at 700 ° C. was read from the Al-X binary system equilibrium diagram, and further, solid-liquid coexistence with respect to Al-10 mass% Mg-1 mass% X The concentration [mass%] of X in liquid aluminum in an equilibrium state at a temperature of 590°C was calculated. These results are shown in Table 2.

As shown in Table 2, even when X is any of Mn, Co, Ti, V, Zr, and Cr, the concentration of X in liquid aluminum at 590 ° C. in liquid aluminum at 700 ° C. It is sufficiently smaller than the solubility of X in , and specifically, sufficiently smaller than 1% by mass. From this, it is considered that according to the impurity removal method, impurities can be efficiently removed even when X (impurity) is any of Mn, Co, Ti, V, Zr, and Cr.

As described above, the impurity removal method according to one aspect of the present invention can efficiently remove metal elements, etc., which are difficult to remove in the aluminum recycling process, so it is suitable for realization of horizontal recycling from aluminum wrought materials to wrought materials. .

10 agitator
20 pressure plate
D α-aluminum dendrites
I intermetallic compounds
X molten metal
Y no

Claims (5)

A step of mixing Mg or Mg alloy with a molten metal containing aluminum or aluminum alloy and impurities;
A step of maintaining the temperature of the molten metal after the mixing step within a solid-liquid coexistence temperature range;
A step of separating the intermetallic compound containing solid aluminum and the impurities generated in the holding step in or from the molten metal in the solid-liquid coexistence temperature range
to provide,
In the separation process, the impurity removal method of stirring or compressing the molten metal. According to claim 1,
A method for removing impurities, wherein the content of Mg in the molten metal after the mixing step is 5% by mass or more. According to claim 1 or 2,
A method for removing impurities in which the solid aluminum and the intermetallic compound are unevenly distributed in the molten metal in the separation step. According to claim 1 or 2,
The solid aluminum contains α-aluminum dendrites,
In the separation step, the impurity removal method of destroying the α-aluminum dendrites. A step of mixing Mg or Mg alloy with a molten metal containing aluminum or aluminum alloy and impurities;
A step of maintaining the temperature of the molten metal after the mixing step within a solid-liquid coexistence temperature range;
A step of separating the intermetallic compound containing the solid aluminum and the impurities generated in the holding step in or from the molten metal in the solid-liquid coexistence temperature range;
Process of solidifying the molten metal after the separation process
to provide,
In the separation step, the ingot manufacturing method of stirring or compressing the molten metal.

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