JP2024127396A - Flux, its manufacturing method and molten metal treatment method - Google Patents

Abstract

To provide novel flux capable of efficiently removing Mg from aluminum matrix molten metal.SOLUTION: Flux contains iron oxide and chloride, can convert Mg contained in aluminum matrix molten metal into MgO to remove Mg. Iron oxide is contained by 10 to 90 mass%, for example, to the whole flux. Iron oxide may be one or more kinds of FeO, Fe2O3 and Fe3O4. Regarding iron oxide in flux, the oxidation number of Fe is reduced to convert Mg into MgO, and iron oxide is brought into contact with oxygen to increase and restore the oxidation number of Fe. A thickness of flux (molten salt) on the aluminum matrix molten metal can be set to 0.05 to 5 mm for example. According to the present invention, while suppressing a use amount of flux and reducing waste matters generated in performing molten metal treatment, Mg can be continuously efficiently removed from aluminum matrix molten metal.SELECTED DRAWING: Figure 5

Description

The present invention relates to fluxes and other materials for use in aluminum-based molten metals.

As environmental awareness grows, lightweight aluminum-based components are being used in a variety of fields. Reusing scrap aluminum rather than using newly refined aluminum can promote the use of aluminum-based components while saving energy, reducing environmental impact, and achieving decarbonization.

When scrap is used, various elements other than Al may be present in the molten metal. Unnecessary or excess elements must be removed from the raw molten metal (Al-based molten metal) produced by melting scrap. As an example, the following document describes the removal of Mg.

US4097270A JP2007-154268A Patent Publication 2008-50637 JP2011-168830 Patent Publication No. 2021-110025 Patent Publication No. 2021-110026 JP2007-154268A Patent Publication 2008-50637 Patent Publication 2011-168830

Light Metals 33 (1983) 243-248 Light Metals 54 (2004) 75-81

Patent Document 1 describes a method in which an Al-based molten metal containing Mg is reacted with silica (SiO ₂ ) (2Mg+SiO ₂ →2MgO+Si) to remove Mg as MgO (a type of metal oxide treatment method).

Patent Document 2 proposes a method in which pellets containing aluminum borate (9Al ₂ O ₃ .2B ₂ O ₃ ) are added to an Al-based molten metal containing Mg, Mg is deposited on the pellets, and then removed as a reaction product (MgAl ₂ O ₄ ).

Patent Documents 3 and 4 propose a method of removing Mg by adding powdered battery slag obtained by roasting used dry batteries to an Al-based molten metal containing Mg. The main components of battery slag are ZnO and _MnO2 , and Mg is removed as a reaction product with these oxides (MgO, _MgMn2O4 or _{MgMnO3 )} . The chlorides contained in the battery slag increase the wettability of these oxides with the Al-based molten metal and promote the generation of reaction products. When using battery slag from an alkaline dry battery, which has a smaller amount of chloride than a manganese dry battery, chlorides (a mixed salt of KCl and NaCl) are replenished.

In Patent Documents 5 and 6, CuO is added to a molten salt formed to a sufficient thickness on the aluminum-based molten metal, and the Mg contained in the aluminum-based molten metal is removed by being absorbed into the thick molten salt. In this case, the amount of Mg removed depends on the amount of CuO added to the molten salt, so continuous replenishment of CuO is required to continuously remove Mg.

Patent Document 7 proposes removing Mg by adsorbing it onto a fired mixture of ceramic aggregate (MnO ₂ : 45 wt %, ZnO: 40 wt %, Fe ₂ O ₃ : 15 wt %) and aluminum borate.

Patent Document 8 proposes adding powder (battery slag) obtained by roasting used dry batteries to an Al-based molten metal to remove Mg contained in the Al-based molten metal. Battery slag also contains _Fe2O3 and _KCl , but its main components are _MnO2 and ZnO. Patent Document 8 describes that iron is not effective as a material for recovering aluminum, and that iron oxide does not react with Mg and serves as an aggregate that adsorbs and removes Mg ([0010], [0020], etc.).

Patent Document 9 proposes a mixed salt of sodium chloride and potassium chloride added to battery slag as a magnesium concentration adjuster for molten aluminum alloy. _MnO2 and _ZnO , which are the main components of battery slag, contribute to reducing the magnesium concentration. Although battery slag contains 3.1 mass% _Fe2O3 ([0016], Table 1), Patent Document 9 does not include any description of iron oxide ( _{Fe2O3 )} or the like.

Non-Patent Documents 1 and 2 describe the chlorine gas treatment method and the flux treatment method. In the chlorine gas treatment method, Mg reacted with gases such as chlorine, hexachloroethane, and carbon tetrachloride injected into the Al-based molten metal is removed as _MgCl2 (Mg+ _Cl2 → _MgCl2 ). In the flux treatment method, Mg reacted with fluorides ( _AlF3 , _NaAlF4 , _{K3AlF6 ,} etc.) added to the Al-based molten metal is removed as _MgF2 (for example, 3Mg+ _2AlF3 → _3MgF2 +2Al). In such treatment methods, much of the Al is trapped in dross and lost, and the working environment is deteriorated and hazardous waste is generated.

The present invention was made in consideration of these circumstances, and aims to provide a new flux for use in aluminum-based molten metal.

As a result of intensive research into solving this problem, the inventor discovered that iron oxide is effective in removing Mg from aluminum-based molten metal, and came up with the idea for a new flux. By expanding on this result, the inventor was able to complete the present invention, which is described below.

Flux
The present invention is a flux containing iron oxide and chloride, the iron oxide being contained in an amount of 10 to 90 mass% based on the total mass of the flux, and capable of converting Mg contained in an aluminum-based molten metal into MgO and removing it.

By using the flux of the present invention, Mg can be removed from aluminum-based molten metal (Al-based molten metal).

Furthermore, by using the flux of the present invention, it is possible to, for example, reduce the amount of flux used, reduce waste (dross, etc.) generated after using the flux, and prevent the generation of hazardous waste and deterioration of the working environment. In other words, it is possible to reduce the costs required for flux and disposal, reduce the environmental load, and ultimately reduce the processing costs of Al-based molten metal. The mechanism by which such excellent effects are obtained is thought to be as follows.

When the flux of the present invention is added to an Al-based molten metal, a molten salt (molten chloride) is formed on the Al-based molten metal. The iron oxide in the molten salt oxidizes (Mg → MgO) the Mg that was absorbed into the molten salt from the Al-based molten metal in exchange for its own reduction (change in the oxidation number (valence) of Fe: +III → +II/+II → 0). Iron oxide with a reduced oxidation number of Fe (simply called "oxidation number" or "valence") increases its oxidation number under conditions where oxygen can be supplied (e.g., in the air). Iron oxide with a restored oxidation number oxidizes Mg (producing MgO) as described above, and reduces its own oxidation number again.

In this way, iron oxide repeatedly decreases its oxidation number (reduction) and increases its oxidation number (oxidation) in the molten salt. This makes it possible to continuously remove Mg from the Al-based molten metal without having to continually replenish iron oxide from the outside to the molten salt formed on the Al-based molten metal, thereby achieving the effects described above.

Incidentally, the above-mentioned reaction in which iron oxide changes the oxidation number of Fe and the oxidation reaction of Mg (producing MgO) are exothermic reactions in total, so using the flux of the present invention can suppress the solidification of the molten salt and save energy by reducing the amount of heat. Also, as is clear from the above explanation, molten metal treatment using the flux of the present invention can avoid the large-scale generation of harmful gases and waste, and deterioration of the working environment.

<Production method of flux>
The present invention can also be understood as a method for producing a flux. The flux can be obtained, for example, by mixing iron oxide and chloride (mixing raw materials (e.g., powders), melting and mixing, etc.). The chloride can be a molten salt or a solid salt (lump, particulate, powder, etc.).

The flux may contain iron oxides with different oxidation numbers. In other words, the flux may contain a single type or multiple types of iron oxides. Iron oxides generally include ferrous oxide (FeO), ferric oxide (Fe ₂ O ₃ ), and triiron tetroxide (Fe ₃ O ₄ ). The flux may contain at least one of these. Note that the oxidation number of at least a part of the iron oxide contained in the flux may change not only during use (during molten metal treatment) but also during production, storage, transportation, etc.

<Method of treating molten metal>
The present invention can also be understood as a molten metal treatment method for removing Mg from an Al-based molten metal using the above-mentioned flux. The molten metal treatment may be performed in an atmosphere (e.g., air atmosphere) in which the flux (particularly iron oxide) is in contact with oxygen. The form of the flux on the Al-based molten metal is not important. For example, if the flux or molten salt is in the form of a layer of a predetermined thickness on the Al-based molten metal, contact between the iron oxide and oxygen can be promoted. At that time, a gas containing oxygen (e.g., air) may be actively pumped, circulated, etc.

Since iron oxide removes Mg from the Al-based molten metal by repeatedly changing its oxidation number, the flux of the present invention can be used continuously or repeatedly even if the Al-based molten metal to be treated is replenished or replaced. When the chloride (molten salt) decreases during molten metal treatment due to evaporation or seepage into the crucible, chloride (which may be in liquid or solid phase) can be replenished. This maintains the appropriate amount of molten salt or flux, allowing for stable continuation of molten metal treatment.

<<Aluminum-based alloy>>
The present invention may be understood as an Al-based alloy made of an Al-based molten metal (including a semi-molten state) after melt treatment (after purification) or a solidified product thereof (ingot, etc.).

"others"
(1) The "flux" referred to in this specification may be either a liquid phase (molten salt containing iron oxide) or a solid phase (solid salt containing iron oxide). As appropriate, a liquid phase flux is referred to as a "molten flux" and a solid phase flux is referred to as a "solid flux". A solid flux may be a mixture (e.g., a mixed powder) of flux raw materials (solid phase) or a solidified product of molten flux. The "flux" referred to in this specification may be regenerated (reused) any number of times as long as Mg contained in the Al-based molten metal can be removed (concentration reduced).

Unless otherwise specified, elements indicated only by the element name (e.g., magnesium) or element symbol (e.g., Mg) can be in any state (simple element, compound, ion, etc.). Unless otherwise specified, concentrations and compositions referred to in this specification are mass percentages (mass%) of the entire object (molten metal, composition, etc.) and are simply indicated as "%".

(2) In this specification, "x to y" includes a lower limit of x and an upper limit of y, unless otherwise specified. Any numerical value included in the various numerical values or numerical ranges described in this specification may be used as a new lower limit or upper limit to create a new range such as "a to b." In this specification, "x to y μm" means x μm to y μm. The same applies to other units.

1 is a graph showing the relationship between the Mg concentration and the Fe concentration in an Al-based molten metal and the treatment time of the Al-based molten metal. 1 is a photograph showing the change over time of the upper surface of the flux (Fe ₂ O ₃ ) during molten metal treatment. 1 is a photograph showing the change over time of the upper surface of the flux (Fe ₃ O ₄ ) during molten metal treatment. 1 is a photograph showing the change over time of the upper surface of the flux (FeO) during molten metal treatment. 1 shows an XRD profile of the flux (Fe ₂ O ₃ ) after treatment. 1 shows an XRD profile of the flux (Fe ₃ O ₄ ) after treatment. 1 is an XRD profile of the flux (FeO) after treatment. This is an enlarged view in which the XRD profiles (2θ=44° to 46°) are superimposed. 1 shows an SEM image and an EDX image of the flux (Fe ₂ O ₃ ) after washing with water. 1 is a SEM image of the raw material (Fe ₂ O ₃ ). FIG. 2 is a schematic diagram for explaining the mechanism by which Mg is removed from an Al-based molten metal by a flux.

One or more components selected arbitrarily from the present specification may be added to the components of the present invention described above. These may be method-related components or components related to substances (e.g., flux (Mg removal agent), Al alloy (molten metal), etc.).

<Magnesium removal principle>
The principle by which Mg is removed from the Al-based molten metal is believed to be as follows.

(1) Basic reaction Mg in an Al-based molten metal can be oxidized as follows:
Anode reaction: Mg → Mg ^{+ 2e} (a)

The Fe that constitutes the iron oxide reacts as follows to change its valence (oxidation number).
Cathodic reaction: ^Fe + ^e → ^Fe (b1)
Fe ²⁺ +2e ^- → Fe (b2)
Anode reaction: Fe ²⁺ → Fe ³⁺ + e ^- (c)

The redox reaction between Mg and iron oxide is thought to be one of the following:
3Fe ₂ O ₃ +Mg → 2Fe ₃ O ₄ +MgO (1)
Fe ₃ O ₄ +Mg →3FeO +MgO (2)
FeO +Mg → Fe +MgO (3)

(2) Oxidation of Iron or Iron Oxide It is believed that when iron or iron oxide comes into contact with oxygen, it restores its oxidation number as follows:
Fe + 1/2O ₂ → FeO (0 → +II) (4)
3FeO + 1/2O ₂ → Fe ₃ O ₄ (+II → +II,+III) (5)
2Fe ₃ O ₄ + 1/2O ₂ → 3Fe ₂ O ₃ (+II,+III → +III) (6)

As shown in reaction formulas (1) to (6), the process in which Mg in the Al-based molten metal is taken into the flux as MgO and removed by iron oxide, and the process in which the iron oxide changes are shown in Fig. 5. Generally, as shown in reaction formulas (a), (b1), and (c) or reaction formulas (1 ₎ and (6), it is considered that the reaction (circulation ₎ between _Fe2O3 and _Fe3O4 mainly occurs.

Incidentally, the reduction reaction of iron oxide (reverse reaction of reaction formulas (b1), (b2) or reaction formulas (4) to (6)) is an endothermic reaction, while the oxidation reaction of metallic Mg (Mg + 1/2O ₂ → MgO) is an exothermic reaction. However, the amount of heat generated by the oxidation reaction of metallic Mg is much greater than the amount of heat absorbed by the reduction reaction of iron oxide. For this reason, the reactions in which iron oxide is reduced and metallic Mg is oxidized (reaction formulas (1) to (3)) are exothermic reactions when viewed as a whole. The heat of reaction (amount of heat generated) obtained at this time can contribute to maintaining the molten state of the chloride.

Chloride
(1) The chloride is a metal chloride consisting of a metal element and Cl. Typical examples of the metal element are K, Na, and Ca. In addition, for example, an alkali metal (Li, etc.) or an alkaline earth metal (Ba, etc.) may be included as the metal element. The molten salt or flux may also include a halide other than the chloride (for example, a bromide).

The chloride may be a simple salt (e.g., KCl, NaCl, CaCl ₂ ) or a complex salt thereof. The use of a complex salt allows adjustment of the melting point, density (specific gravity), wettability, vapor pressure, hygroscopicity, etc., and cost reduction. For example, KCl, which lowers the melting point of the chloride, may be contained in an amount of 30 to 70 mass% (simply referred to as "%") or 40 to 65% of the entire chloride. NaCl may be contained in an amount of 30 to 60% or 35 to 47% of the entire chloride. MgCl ₂ may be contained in an amount of, for example, 1 to 20% or 3 to 10% of the entire chloride. MgCl ₂ can perform the function and action of lowering the melting point of the chloride.

The chloride may be a mixture (mixed salt) of multiple types of raw salts, a molten salt obtained by melting and solidifying (coagulating) the entire raw salt, or a mineral-derived chloride obtained from a mineral (e.g., carnallite anhydrous: KMgCl ₃ ), etc.

(2) The chloride content of the flux is, for example, 30-80%, 40-70%, or 45-65%. The mixture ratio (mass ratio) of iron oxide to chloride may be, for example, 0.5-1.5 or 0.8-1.2. If the chloride content is too little or too much, the efficiency of magnesium removal may decrease.

Iron Oxide
The iron oxide may be in any form that can be retained in the chloride (particularly the molten salt). The iron oxide may be, for example, particulate (powdered) or lumpy. The size of the iron oxide is not important, and may be, for example, a maximum length of 1 to 100 μm, 3 to 30 μm, or 5 to 10 μm. The size in this specification is specified, for example, by the arithmetic mean value of the maximum lengths appearing in a field of view (horizontal: 50 to 500 μm × vertical: 50 to 500 μm). The form (shape, size) of the iron oxide may change before and after molten metal treatment (before and after addition to the Al-based molten metal) and even during the molten metal treatment.

Flux
As long as the flux melts on the Al-based molten metal, it may be in a liquid state or a solid state. The flux before being poured into the Al-based molten metal may be a mixture of raw materials (mixed powder, etc.) or a solid (molten product) obtained by dissolving and solidifying the mixture. The solid may be, for example, in a lump or granular form (crushed powder, granules, powder, etc.).

The flux may contain magnesium oxide. The magnesium oxide may be formed during the treatment of the molten metal. Porous magnesium oxide can contribute to reducing the density (specific gravity) of the flux and accelerating the redox reaction.

Molten metal treatment
The flux (or molten salt) does not necessarily have to be in a layer on the Al-based molten metal. The thickness of the flux on the Al-based molten metal may be, for example, 0.05 to 5 mm, 0.1 to 4 mm, 0.5 to 3 mm, or 1 to 2.5 mm. By controlling the thickness of the flux within a desired range, the reaction between the iron oxide in the flux and the oxygen above it is promoted. Therefore, the molten metal treatment may be performed, for example, in an atmosphere in which at least the flux is in contact with oxygen. Such an oxygen-containing atmosphere may be the air atmosphere or an atmosphere in which the oxygen concentration (oxygen pressure) is controlled.

The flux can be continuously used or reused even when replenishing or replacing the Al-based molten metal. When the chloride (molten salt) in the flux decreases, it should be replenished as appropriate. Such replenishment may be controlled, for example, based on the thickness of the flux (molten salt) on the Al-based molten metal.

The flux may cover only a portion of the surface of the Al-based molten metal. Covering the entire surface of the Al-based molten metal improves the efficiency of Mg removal and inhibits oxidation of Al.

The longer the treatment time, the more the Mg concentration in the Al-based molten metal can be reduced. However, when recycling scrap, etc., it is often sufficient if the Mg concentration is within the desired range. The treatment time per session is, for example, 0.1 to 3 hours, 0.3 to 2 hours, or 0.5 to 1 hour. The Mg concentration in the Al-based molten metal may be gradually reduced by repeating the molten metal treatment to remove Mg.

The present invention will be explained in more detail while showing a specific example of the removal of Mg from Al-based molten metal using flux.

［Overall Overview］
Unless otherwise stated, the various experiments were carried out under the conditions shown below.

(1) Raw Materials Commercially available pure Al (purity 99.7%) and Al-20% Mg alloy (purity 99.7%) were melted in a graphite crucible to prepare an Al-1.0% Mg molten metal (710°C ± 20°C). The concentration (%) is a mass percentage (mass%) unless otherwise specified. When the concentration of this initial molten metal was confirmed by XRF analysis described later, it was found to contain about 0.1% Fe (impurity).

The chloride used was a mixed salt (KCl-41% NaCl-5% MgCl ₂ ) prepared by blending commercially available reagents. The mixed salt was prepared by crushing melted and solidified solid salt into particles of about 3 mm. The density (specific gravity) of the mixed salt was 2.4 g/cm ³ or less, and the molten salt separated into two phases from the Al-based molten metal and formed on the Al-based molten metal. Instead of a solid salt (particulate, etc.), a mixture of raw salts (powder, etc.) may be used as the chloride as it is.

As the iron oxide, ferrous oxide (FeO), ferric oxide (Fe ₂ O ₃ ) or triiron tetroxide (Fe ₃ O ₄ ) powder (commercially available reagent) was used.

(2) Molten metal treatment The molten metal treatment was carried out in an open atmosphere unless otherwise specified. During the molten metal treatment, the Al-based molten metal was kept at 710° C.±20° C., and no stirring or other operations were performed.

(3) Concentration Analysis The chemical components (Mg concentration, etc.) of the Al-based molten metal were analyzed as follows. First, the Al-based molten metal sampled from approximately the center of the crucible was poured into a mold (stainless steel analytical mold) and allowed to solidify naturally in the air. The chemical components (Mg concentration, Fe concentration) of the resulting Al alloy casting (sample) were measured using an X-ray fluorescence analyzer (XRF: ZSX Primus II manufactured by Rigaku Corporation).

(4) Observation and analysis The appearance of the flux on the Al-based molten alloy was observed. The flux was also observed with a scanning electron microscope (SEM/SU3500 model, Hitachi High-Technologies Corporation). Furthermore, elemental analysis of the flux was performed with an energy dispersive X-ray spectrometer (EDX) attached to the microscope.

Furthermore, the solidified flux collected after the molten metal treatment was crushed in a mortar to produce particles, which were then analyzed using an X-ray diffractometer (Bruker D8ADVANCE/Fe-Kα radiation, 2θ: 30-85°) to identify the compounds. For comparison, X-ray diffraction analysis (XRD) was also performed on the raw powder of iron oxide.

[Example 1] (Mg removal)
Flux preparation
Each iron oxide (9 g) and the mixed salt (9 g) were mixed in a beaker to prepare a flux (mixture ratio: 1). In this way, three types of flux (18 g) with different iron oxides were prepared.

Molten metal treatment
Each flux was added uniformly to the entire surface of the Al-based molten metal and allowed to stand. At this time, the height (thickness) from the surface of the Al-based molten metal to the top surface of the flux was about 3 mm. The thickness was measured with a scale.

Measurement and Observation
(1) Concentration The Mg concentration and Fe concentration in the Al-based molten metal were measured by the above-mentioned method at each predetermined time interval after the addition of the flux. The results are shown in Figure 1. The initial concentration of the Al-based molten metal is shown at 0 min of treatment time.

The theoretical values in Fig. 1 are Mg concentrations calculated on the assumption that the maximum amount of Mg in the Al-based molten metal is removed by the iron oxides contained in the flux based on reactions ( ₁ ) to ( ₃ ). Specifically, the Mg concentrations are calculated on the assumption that reaction (1) → reaction (2) → reaction (3) occurs for _Fe2O3 , reaction (2) → reaction (3) occurs for _Fe3O4 , and reaction (3) occurs for FeO.

(2) Appearance The appearance of the flux on the Al-based molten metal was observed immediately after the flux was added to the Al-based molten metal and after a predetermined time (15 minutes and 30 minutes) had elapsed. The appearance photographs are shown in Figures 2A to 2C (collectively referred to as "Figure 2"). In this example, unless otherwise specified, each flux is distinguished by the iron oxide (raw material) that was added (the same applies below).

(3) XRD
The XRD profiles of the fluxes collected after 120 minutes of molten metal treatment (referred to as "treated fluxes") are shown in Figures 3A to 3C. In each figure, the XRD profile of the iron oxide (raw material) used to prepare the fluxes is also shown. A partially enlarged view (2θ=44° to 46°) in which the XRD profiles of each treated flux are superimposed is also shown in Figure 3D. Figures 3A to 3D are collectively referred to as "Figure 3."

(4) SEM-EDX
After the treatment, the flux (Fe ₂ O ₃ ) was crushed in a mortar and washed with water. The SEM image and EDX image (element distribution) of the residue are shown in FIG. 4A. The iron oxide ( The SEM image of Fe ₂ O ₃ is shown in FIG. 4B. Both figures are collectively referred to as FIG.

"evaluation"
(1) Concentration As is clear from Fig. 1, it was found that the Mg concentration in the Al-based molten metal was reduced almost in proportion to the treatment time, regardless of which flux containing iron oxide was used. Moreover, the Mg concentration reached the theoretical value in about 30 to 60 minutes, and then continued to decrease beyond the theoretical value.

On the other hand, the Fe concentration in the Al-based molten metal hardly changed during the molten metal treatment. It is believed that iron oxide or precipitated Fe hardly dissolved in the Al-based molten metal during the molten metal treatment.

Furthermore, when flux (FeO) was used, the Mg concentration did not decrease at first. However, it gradually decreased with the _treatment time. This is thought to be because FeO was oxidized to produce _Fe3O4 or _Fe2O3 (reaction formulas (5) and (6)). In other words, the amount of Fe that changed its oxidation number from ₊ II to +III increased.

(2) Appearance As is clear from FIG. 2, it was confirmed that the white portion (MgO) increased with time regardless of which flux was used.

As can be seen from Figure _2A , the flux ( _Fe2O3 ) was reddish brown immediately after addition, but some of it turned black over time. When a permanent magnet was brought close to the flux after treatment, the black parts showed ferromagnetic properties. This is thought to be because _Fe2O3 (reddish brown parts ₎ , which is weakly magnetic (or antiferromagnetic), changed to _Fe3O4 (black ₎ , FeO (black), or Fe during the molten metal treatment.

As can be seen from Fig. _2B , the flux ( _Fe3O4 ) was black immediately after addition, but part of _it changed to reddish _brown over time. It is believed that _Fe3O4 changed to _Fe2O3 during the molten metal treatment. Immediately after the addition of each flux (FeO, _Fe3O4 , _Fe2O3 ), red heat due to _{heat generation} was observed.

As can be seen from Figure 2C, the flux (FeO) had fewer black and reddish brown areas than the other fluxes, and the white areas increased over the course of 30 minutes after addition.

(3) XRD
As can be seen from Fig. _3A , the treated flux ( _Fe2O3 ) contained a large amount of the removed Mg oxide (MgO) in addition to the raw material chlorides (NaCl, _KCl ).Furthermore, _{it also contained iron oxide (Fe3O4) and iron (Fe) that were different from the raw material iron oxide (Fe2O3 ) .}

As can be seen from Fig. _3B , the treated flux ( _Fe3O4 ) also contained a large amount of the removed Mg oxide ( _MgO ) in addition to the raw material chlorides (NaCl, _KCl ).It also contained iron oxide ( _Fe2O3 ) and iron different from the raw material iron oxide ( _Fe3O4 ).

As can be seen from Fig. 3C, the treated flux (FeO) also contained a large amount of the oxide of the removed magnesium (MgO) in addition to the raw material chlorides (NaCl, _KCl ).It also contained iron oxide ( _Fe3O4 ) and iron that were different from the raw material iron oxide (FeO).

The treated flux (FeO) contained more iron than the other treated fluxes. Incidentally, the iron oxide (FeO) used as the raw material was of reagent grade, but _it also contained a lot of _Fe3O4 in addition to FeO.

In this way, it was confirmed that by using a flux consisting of iron oxide and chlorides, Mg in the Al-based molten metal is efficiently removed as MgO. It was also confirmed that after processing, other iron oxides and iron with Fe oxidation numbers (valences) different from those in the raw material appear in the flux.

As shown in Figures 1 and 3, when considering the amount of Mg removed that exceeded the theoretical value and the appearance of iron oxide with a higher oxidation number than the raw material, it is believed that oxygen was supplied from the outside to the flux (iron oxide) during molten metal treatment.

(4) SEM-EDX
As is clear from Fig. 4A, the residue after washing with water to remove chlorides was mainly MgO and iron oxides ( _Fe2O3 , _Fe3O4 ). The MgO was, for example, in the form of granules with a particle size of more than 3 _µm or coarse rods with a length of more than 10 _µm .

Furthermore, as can be seen from a comparison between FIG. 4A and FIG. 4B, the iron oxide in the flux after the treatment had the same form (maximum length of about 5 μm or less) as that of the raw material (Fe ₂ O ₃ ).

From the above, it has been confirmed that the present invention can efficiently remove Mg from Al-based molten metal while reducing the amount of flux used and waste generated during molten metal treatment.

Claims (8)

A flux containing iron oxide and chloride,
The iron oxide is contained in an amount of 10 to 90 mass % based on the total mass of the flux,
A flux that can convert Mg contained in aluminum-based molten metal into MgO and remove it. 2. The flux of claim 1, wherein the iron oxide is one or more of FeO, _{Fe2O3 , and Fe3O4} . The flux of claim 1 , wherein the iron oxide comprises at least Fe ₂ O ₃ . A manufacturing method for obtaining the flux described in any one of claims 1 to 3 by mixing iron oxide and chloride. A molten metal treatment method for removing Mg from the aluminum-based molten metal using the flux according to any one of claims 1 to 3. The molten metal treatment method according to claim 5, which is carried out in an atmosphere in which the flux is in contact with oxygen. The molten metal treatment method according to claim 5, wherein the iron oxide reduces the oxidation number of Fe to convert Mg to MgO. The molten metal treatment method according to claim 6, wherein the iron oxide increases the oxidation number of Fe when in contact with oxygen.

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