JPH0931562A - Method for purifying aluminum or aluminum alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop a method for purifying Al or an Al alloy in which Bi contained as an impurity in Al or an Al alloy, particularly, in recovered scraps thereof is efficiently be removed away at a low cost. SOLUTION: The molten metal of Al or an Al alloy contg. <0.1wt.% Bi as an impurity is added with alkaline earth metals or alkaline earth metal compounds by >=0.3wt.% to the molten metal to form intermetallic compounds of impurity Bi and alkaline earth metals, which are removed away, and after that, the alkaline earth metals or alkaline earth metal compounds remaining in the molten metal are removed away by halogen refining or the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a melting method of Al or Al alloy, and more specifically, a small amount of Bi or a small amount of Bi and S contained as impurities in Al or Al alloy.
The present invention relates to a method for efficiently removing and cleaning i in a dissolved state.

[0002]

2. Description of the Related Art Al or Al alloys are used for various purposes because they have characteristics such as light weight, workability and surface beauty. However, there is a problem that a coarse eutectic compound is generated due to the mixing of the impurity element, and the strength, toughness, surface treatment property, etc. are significantly deteriorated. Therefore, the impurity elements must be reduced as much as possible, but no effective removal method has been proposed for Bi impurities.

Further, Al or Al alloy is also widely used as a fin material for a heat exchanger because it has an excellent heat transfer property, and is considerably suitable for a brazing sheet or a brazing material used for its molding. Amounts of Bi and Si are included. Therefore, when recovering and reusing Al or Al alloy scrap such as fin material for heat exchangers, a considerable amount of Bi and Si are mixed in the remelted product of the recovered product, which is left as it is. When reused, coarse eutectic compounds are formed, resulting in poor physical properties, moldability, and surface treatment properties.
In order to reuse it as an alloy recovery product, it is necessary to remove Bi and Si as much as possible for cleaning.

However, for Bi contained as impurities in Al or Al alloy, no industrially practical removal method has been developed as described above, while for Si, the following removal method has been proposed. However, it is not always satisfactory in terms of processing efficiency and processing cost.

Segregation method: Japanese Patent Publication No. 1-279712
As described in Japanese Patent Publication, when the molten Al or Al alloy is solidified, the principle of solidifying from a high-purity portion is utilized, and the impurity Si is concentrated in the portion that remains unsolidified at the end of solidification. However, this method has low processing efficiency and is not suitable for large-scale processing.

Electrolysis method: Japanese Patent Publication No. 62-103
As described in Japanese Patent Publication No. 15, a method of separating and removing impurity Si from Al or molten Al alloy by electrolysis, but this method has a high processing cost and is not suitable for large-scale processing. Lacks practicality.

[0007]

The present invention focuses on the above-mentioned problems of the prior art, and efficiently removes Bi or Bi and Si and Si contained as impurities in Al or Al alloy at low cost and cleans them. As a result of conducting research to provide a method capable of achieving the above, a compound containing an alkaline earth metal, particularly Ba, Ca or Mg is added to an Al or Al alloy molten metal, and Bi contained as an impurity in the molten metal is added. Based on these findings, it was found that if it is produced in a crystallized or semi-molten state as an intermetallic compound with an earth metal, it can be efficiently removed from the molten metal by filtration while suppressing metal loss as much as possible. And applied for a patent first (Japanese Patent Application No. 6-217685).
issue).

In the invention of this prior application, as a preferable condition for efficiently removing Bi, the addition amount of the alkaline earth metal compound to the molten Al alloy is a chemical capable of forming an intermetallic compound with Bi contained in the molten metal. The stoichiometric equivalent of 1.
By setting the amount to 5 to 3 times, Bi can be efficiently removed.

However, after further research,
When the content of Bi contained as an impurity in the molten alloy is 0.1% by weight or more, which is relatively large,
As clarified in the invention of the prior application, Bi can be efficiently removed by adding 1.5 to 3 times the stoichiometric equivalent of an alkaline earth metal compound capable of forming an intermetallic compound with Bi. The content of Bi contained as an impurity is 0.1
It has been found that a sufficient cleaning effect cannot be obtained even if this method is directly applied to an Al alloy melt having a weight less than that.

Based on such knowledge, the present invention efficiently removes Bi even from an Al alloy melt containing a small amount of Bi of 0.1% by weight or less, or efficiently adds Si together with a small amount of Bi. They are trying to establish a method that can be removed.

[0011]

Means for Solving the Problems The constitution of the present invention capable of achieving the above object is 0.1% by weight as an impurity.
In an Al or Al alloy melt containing less than Bi, 0.3% by weight or more of an alkaline earth metal or an alkaline earth metal compound is added to the melt to form an intermetallic compound of impurities Bi and an alkaline earth metal. The main point is that the alkaline earth metal remaining in the molten metal is removed after the formation of the metal and the separation thereof.

At this time, when the Bi-containing intermetallic compound formed in the molten Al or Al alloy is separated and removed, an inert gas is blown into the molten metal to accelerate the floating separation of the intermetallic compound, or Bi The method of removing the contained intermetallic compounds with a fireproof filter can be effectively used,
Further, it is advantageous to employ halogen refining for removing the alkaline earth metal remaining in the molten metal.

Another structure according to the present invention is Al or A containing Si together with Bi of less than 0.1% by weight as an impurity.
At least one element selected from the group consisting of Nb, V, Ti and Mo, or at least one metal compound of these is added to the molten alloy of alloy No. 1 and the impurity Si in the melt and the metal The gist thereof resides in that the step of forming a compound and separating it and the step of separating a small amount of Bi by the above method are combined and carried out.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, according to the invention of the prior application, Bi contained as an impurity in the molten Al alloy can be easily mixed with an alkaline earth metal, particularly an alkaline earth metal composed of Ba, Ca or Mg. It is based on the finding that it forms an intermetallic compound and exists in the molten Al in a crystallization or semi-molten state, and can be easily separated and removed by filtration or the like without metal loss, which is preferable for efficiently removing Bi. As a requirement, by setting the amount of the alkaline earth metal compound added to the molten Al alloy to be 1.5 to 3 times the stoichiometric equivalent capable of forming an intermetallic compound with Bi contained in the molten alloy, It was intended to efficiently remove Bi. However, this method can be effectively used when the content of Bi contained as an impurity in the molten Al alloy is relatively large, such as 0.1% by weight or more.
When applied to an Al alloy melt containing a small amount of Bi less than 0.1% by weight, particularly 0.08% by weight or less, a satisfactory Bi removing effect cannot be obtained.

However, when the Bi content in the melt is low, Bi and the alkaline earth metal compound in the melt can be added even if about 3 times the stoichiometric equivalent to the Bi content is added. It is thought that this is because the place for the reaction of is not sufficiently secured. Therefore, as a result of further research to efficiently remove even a small amount of Bi, the addition amount of the alkaline earth metal compound is not regulated by the stoichiometric equivalence ratio to the Bi content, but Al alloy If a sufficient amount of molten metal is specified and the Bi-containing intermetallic compound formation site is sufficiently secured, a small amount of Bi can be sufficiently removed, and in order to ensure a satisfactory Bi removal effect, an alkaline earth metal is required. It has been found that the amount of the metal compound added may be set to 0.3% by weight or more with respect to the amount of molten Al alloy.

However, when a large amount of the alkaline earth metal compound is added to the impurities Bi as described above, the surplus alkaline earth metal compound remains in the molten metal and causes reverse pollution. It is necessary to establish a cleaning method based on this. Therefore, as a means for solving such a problem of reverse contamination, a method of removing excess alkaline earth metal compound by halogen refining or the like after the Bi removal treatment is adopted.

Halogen refining is a known method as a means for removing alkaline earth metals from molten Al alloy.
In this method, a halogen gas, most commonly chlorine gas is blown into the molten metal or an alkali halide such as KCl is added to refine and remove an alkaline earth metal compound as a halide. The method is used to remove an alkaline earth metal compound that has been added in a large amount to remove Bi and remains as an excess in the molten metal. The Bi removal treatment and the halogen refining removal of the excess alkaline earth metal compound are performed. By carrying out in combination, without causing reverse pollution by alkaline earth metal compounds,
It succeeded in removing as little Bi as possible from the molten Al alloy and cleaning it.

In the present invention, Be, Mg, Ca, Sr, Ba and Ra are used as the alkaline earth metal added to remove Bi, as has been clarified in the invention of the prior application. Among them, Mg, Ca, and Ba are particularly preferable in view of economic efficiency, and they can be used alone or, if necessary, can be used in combination of two or more kinds to form a complex intermetallic compound to remove Bi. it can. Further, these alkaline earth metals can be used not only as a simple metal but also by adding in the form of an alkaline earth metal compound such as a silicide, a carbide, a fluoride, a boride, a chloride or a sulfide. It can serve the purpose of Bi removal.

Among the above-mentioned alkaline earth metal compounds, it is particularly preferable that even if a considerable amount remains in the treated molten metal as a surplus despite the halogen refining as described later, it has a bad influence on the physical properties of the Al alloy. It is Mg that has little effect.

The amount of the alkaline earth metal or its compound added is 0.3 based on the molten Al alloy in order to secure a sufficient reaction field with Bi contained in a small amount and obtain a satisfactory Bi removal rate. It is necessary to add it in an amount of not less than 0.5% by weight, preferably not less than 0.5% by weight, and if it is less than this amount, a sufficient Bi removal rate as intended in the present invention cannot be obtained. The satisfactory Bi removal rate intended in the present invention means that the Bi content after the treatment is 9 ppm or less, more preferably 7 pp.
It can be considered that the value is reduced to m or less.

In removing Bi, the Bi removal rate increases as the amount of the alkaline earth metal compound added increases, but the effect is almost saturated at about 5% by weight, and the amount of Bi added further increases. However, since the Bi removal rate hardly increases, it is 5 from the viewpoint of suppressing the subsequent halogen refining load.
It is desired to control the content to be not more than 5% by weight, more preferably not more than 3% by weight.

The impurities Bi can be removed by separating these intermetallic compounds from the molten Al alloy formed by the intermetallic compounds. The method for removing the intermetallic compound is not particularly limited, but it is considered that the produced intermetallic compound is heavier than the Al alloy, and the intermetallic compound is allowed to settle by allowing the molten metal to stand and calm down. It is preferable to remove it by a method such as filtering the molten metal with a filter. In addition, since many intermetallic compounds are suspended in the molten metal, inert gas such as nitrogen, argon, He, and neon are blown into the molten metal in the form of fine bubbles, and the intermetallic compounds float as the bubbles float. A separation method such as removing the slag by removing it can also be preferably used. In this case, dehydrogenation can also be achieved at the same time.

In the present invention, since a large amount of alkaline earth metal compound is added for Bi removal as described above, a large amount of surplus alkaline earth metal compound that does not bind to Bi as it is remains in the molten metal, and thus clean. Has not achieved the goal of Therefore, in the present invention, the excess alkaline earth metal compound is removed by halogen refining.

Halogen refining may be carried out in accordance with a known method. Specifically, a method of bubbling by blowing a halogen gas (generally chlorine gas) into the molten metal, K
A method in which an alkali halide flux such as Cl is added for treatment may be adopted.

Next, Si is added as another impurity in the molten Al.
When present, the Si must be removed as much as possible. Therefore, the Si is also removed as an intermetallic compound in the same manner as adopted in the above-mentioned prior invention. Nb, V, Ti, Mo are the elements that form a metal compound with Si.
As shown in FIG. 1, these elements have a low free energy of intermetallic compound formation between Si, easily form an insoluble intermetallic compound in the molten Al alloy, and are easily separated and removed from the molten Al alloy. In addition to the case where these metals are used as a simple substance, their metal compounds (for example, silicide, carbide, fluoride, boride, chloride,
Even when it is added as a sulfide) to the molten aluminum, it reacts with Si in the molten metal to form an intermetallic compound, which can be easily separated and removed from the molten aluminum.

Therefore, when Si is contained in the molten Al alloy together with a small amount of Bi as an impurity, B as described above is used.
At any stage before and after the i removal process, N is added to the molten metal.
Si contained in the melt containing at least one element selected from b, V, Ti and Mo, or one or more of these metal compounds.
By adding according to the amount, it is possible to form an insoluble intermetallic compound in the Al melt with Si and separate and remove it from the melt. In this case, the preferable addition amount is a weight ratio of Si: 1 contained in the molten metal to Nb of 5.5.
˜16.5 (more preferably 6.0 to 15.0), V is 1.0 to 16.3 (more preferably 1.5 to 15.
0) and Ti are 1.5 to 5.1 (more preferably 2.0 to
5.0) and Mo are in the range of 5.5 to 30.2 (more preferably 6.0 to 25.0), and S is less than the above range.
If i is insufficiently removed, on the other hand, if it is added in excess of the above range, an excessive amount of Nb, V, Ti, and Mo will remain and cause the contamination of the molten metal.

The lower limit of the amount of addition of the above elements and the like is the impurity S
It is a stoichiometric equivalent capable of forming an intermetallic compound with i, but for example, when Nb is used as an additional element to produce the intermetallic compound Nb ₅ Si ₃ , the stoichiometric equivalent is N.
b: Si = 5: 3, and Nb is 1.67 atoms with respect to Si: 1 atom in the molten metal, and the Nb: Si ratio in terms of weight ratio is 1.
54: 28.10, which is almost the same as the lower limit of the above-mentioned preferable addition amount range. However, a sufficient field for the reaction for the formation of the intermetallic compound is ensured, and sufficient S
To achieve i removal efficiency, a stoichiometric equivalent ratio of 1.5
It is desirable to use about 3.0 times or more of the element, and to prevent the contamination of the molten metal due to excessive addition, it is desired to be suppressed to about 3.0 times or less, more preferably about 2.0 times or less.

When two or more of the above-mentioned additional elements are added in combination, the element having a low free energy of formation of the intermetallic compound first forms the intermetallic compound with Si, and the other element is consumed until the element is consumed. It has been confirmed that an intermetallic compound with and is not generated, and Mo is the most likely to remain among the above-mentioned additional elements. Therefore, in the case of compound addition, in consideration of the free energy for forming an intermetallic compound between these elements and Si. It is desirable to determine the addition amount of each.

The method for separating and removing the produced intermetallic compound from the molten metal is similar to the method for separating and removing the Bi-containing intermetallic compound described above. The method of filtering the molten metal with the porous body filter, the inert gas such as nitrogen, argon, He, neon, etc. is blown into the molten metal in the form of fine bubbles, and the intermetallic compounds are levitated along with the floating of the bubbles to remove them. A method or the like may be adopted.

As described above, according to the present invention, when the molten aluminum contains a small amount of Bi as an impurity, the alkaline earth metal or its compound is contained in an amount of 0.3% by weight or more based on the molten aluminum alloy. Added, and separated and removed from the melt as a Bi-alkaline earth intermetallic compound, the surplus alkaline earth metal compound is removed by halogen refining, and when Bi and Si are contained as impurities, the above Bi- By performing Bi removal as an alkaline earth intermetallic compound and halogen refining, and separation and removal as a Si-containing intermetallic compound by adding Nb, V, Ti, Mo or their element-containing compounds in any order. , Without causing reverse contamination of alkaline earth metal compounds,
A small amount of Bi or this and Si can be removed efficiently.

The Al or Al alloy molten metal from which a small amount of Bi or Si has been removed in this way is regenerated as Al or Al alloy having a further improved cleanliness by refining to remove other impurities as necessary. be able to.

[0032]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which do not limit the present invention.
Modifications and alterations that do not depart from the spirit described below are all included in the technical scope of the present invention.

Example 1 As a raw material, JIS-41 containing Bi: 0.05% by weight
04 Al alloy scrap was used. As the melting furnace, a 10-ton reflective melting furnace (fuel oil burning) was used for atmospheric melting.
After performing the Bi removal treatment with the added elements and amounts shown in Table 1, chlorine gas was blown at 0.6 m ³ / h for 20 minutes to remove the excess alkaline earth metal compound. This molten metal was sampled and filtered through a filter having a mesh size of 200 μm to remove insoluble matter, and then elemental analysis was performed.
The removal rate and residual rate of alkaline earth metal were determined.

The results are shown in Table 1. If 0.3% by weight or more of the alkaline earth metal compound is added to the molten metal and then halogen refining is carried out, reverse contamination by the alkaline earth metal compound is caused. It can be seen that a small amount of Bi can be efficiently removed without being generated. Incidentally, M in the table is an additive metal element, and in the case of the combined system, the same amount is used. The evaluation criteria for residual concentration are as follows. Bi residual concentration ◯: less than 8 ppm, Δ: 9 to 10 ppm, x: 10 pp
m over alkaline earth metal residual concentration ○: less than 8 ppm, △: 9 to 10 ppm, ×: 10 pp
over m

[0035]

[Table 1]

Example 2 As a raw material, JIS-41 containing Bi: 0.05% by weight
04 alloy scrap was used. As the melting furnace, a 10-ton reflective melting furnace (fuel oil burning) was used for atmospheric melting. As shown in Table 2, Ca and Mg are added in the amounts shown in the same table, and Bi is added.
After removal treatment, Ar gas was blown at a flow rate of 0.6 m ³ / hr for 40 minutes, and then KCl flux was blown into the treated melt using 0.08% nitrogen gas based on the weight of the melt to perform halogen refining. Then, the mixture was passed through a filter having a mesh size of 100 μm. The obtained molten metal was sampled and subjected to elemental analysis to determine the residual concentrations of Bi and alkaline earth metal. Evaluation criteria are the same as above.

The results are shown in Table 2, and it is understood that Bi in the molten metal can be reduced to an extremely low level by adding an alkaline earth metal compound in an amount equal to or more than the amount specified in the present invention. In addition, it is uneconomical to increase the amount of the alkaline earth metal compound added excessively, and the recycling merit is reduced, which is not preferable.

[0038]

[Table 2]

Example 3 As a raw material, an Al-Mg alloy brazing sheet scrap containing Bi: 0.08% by weight was used. As a melting furnace, a 4-ton reflective melting furnace (LNG-fired) was used to melt in the atmosphere. As shown in Table 3, Ca and Mg were added together in the equivalent ratio shown in the same table to remove Bi, and nitrogen gas was blown for 30 minutes at a flow rate of 0.6 m ³ / hr, and chlorine gas was further added to 0.6 m. ^The excess alkaline earth metal compound was removed by blowing at ³ / h for 20 minutes. This molten metal was sampled and filtered through a filter having a mesh size of 200 μm to remove insoluble matter, and then elemental analysis was performed to determine the removal rate of Bi and the residual rate of alkaline earth metal.

The results are shown in Table 3. The evaluation criteria in the table are the same as above. As is clear from this table, those obtained by adding the alkaline earth metal compound in the specified amount or more and then performing the halogen refining treatment are Bi, Ca, M
Al with a very low residual concentration of g and high cleanliness
It can be seen that it is regenerated as an alloy.

[0041]

[Table 3]

Example 4 As a raw material, scraps of automobile heat exchanger parts having a Si content of 10% by weight and a Bi content of 0.08% by weight are used, and Si and Bi are removed by the following method. (Removal of Si) The raw material is melted in the atmosphere using a 30 ton LNG-fired reverberatory furnace (720 ° C.), and V is added to the molten metal in an amount 1.5 times the equivalent amount of Si to produce a Si-V system. Produces an intermetallic compound, which is subsequently 0.1% of the weight of the molten metal.
After refining by injecting the KCl-based flux of 1) together with nitrogen gas, the generated slag is discharged to the outside of the melting furnace by a rake. Then, a degassing process is performed using a Sniff manufactured by Union Carbide Co., and insoluble inclusions are removed by a tubular filter. (Removal of Bi) In the above Si removal method, 1.0 is added to the molten metal for Bi removal in place of V for Si removal.
Except for adding Ca by weight, the same procedure as above for B
i removal processing is performed.

The above Si removal and Bi removal are carried out by the following A and B.
Alternatively, the procedures of C were performed in combination, and elemental analysis was performed on each of the obtained molten metals to check the residual Si and Bi concentrations. In addition, a billet of 400 mm ^t × 1500 mm ^w was manufactured by a semi-continuous casting method using each of the obtained treated molten metals. Next, each billet is subjected to hot rolling and cold rolling to form a plate of 0.3 mm ^t , and the work crack occurrence rate during hot working is measured, and the cold rolled plate strength test (pass:
12 kgf / mm ² or more, reject: 12 kgf / mm ²
Less than) and the surface treatment property test of the cold-rolled sheet (pass: incidence of treatment failure in alumite treatment of less than 0.05%, failure: incidence of more than 0.05%). (Processing procedure) A: After removing Si, subsequently performing Bi removing treatment B: First performing Bi removing treatment, and then performing Si removing treatment C: Simultaneous addition of a predetermined amount of V and Ca into the molten metal, and Si Removal and Bi removal in parallel

The results are collectively shown in Table 4. According to this method, both Si and Bi mixed as impurities in Al or Al alloy molten metal can be efficiently separated and removed. It can be seen that it can be recycled as highly clean Al or Al alloy that can be reused as a recycled product without any trouble. In the above, V is used to remove Si,
An example using Ca for Bi removal is shown as a representative, but Nb, Ti, Mo or their compounds are used in place of V, and other alkaline earth metals or their compounds are used in place of Ca. It has been confirmed that similar results can be obtained even in the case of doing.

[0045]

[Table 4]

A JIS standard Al alloy shown in Table 5 was manufactured using the above-mentioned molten metal that had been cleaned by removing Si and Bi, an untreated molten metal, and an Al base metal, and hot-rolled and cold-rolled. Regarding the Al alloy plate obtained by performing
Tensile strength and elongation were measured according to 3004. The results are shown in Table 5, and it can be seen that the one using the molten metal regenerated according to the present invention shows a value almost equal to the one using the Al metal in any performance.

[0047]

[Table 5]

[0048]

The present invention is configured as described above.
1 or Al alloy, particularly Bi or Bi and Si contained in a small amount of recovered scrap, can be efficiently removed at low cost and can be regenerated as Al or Al alloy having high cleanliness.

[Brief description of drawings]

FIG. 1 is a graph showing free energy of formation of an intermetallic compound with Si.

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Kiyomasa Oga 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo Prefecture Kobe Steel Research Institute, Kobe Steel Co., Ltd. (72) Inventor Motohiro Arai Takatsuka, Nishi-ku, Kobe-shi, Hyogo Prefecture 1-5-5, Taiwan Steel Works, Kobe Steel Co., Ltd. (72) Inventor Jun Takigawa, 15 Kinugaoka, Moka City, Tochigi Prefecture Kamito Steel Works, Ltd., Moka Works (72) Inventor Shunichiro Maezono Tochigi 15 Kinugaoka, Moka-shi, Japan Kamito Steel Works, Ltd. Moka Works (72) Inventor Ryuhei Masuda 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo Kobe Steel Works, Ltd. Kobe Research Institute (72) Inventor Joji Masuda 14-1 Chofu Minatomachi, Shimonoseki City, Yamaguchi Prefecture Inside the Kobe Steel Works, Chofu Works (72) Inventor Takayuki Kitano, Yamaguchi Prefecture No. 14-1 Minatomachi, Chofu, Seki City Kobe Steel Co., Ltd. Chofu Works

Claims (5)

[Claims] 1. An Al or Al alloy melt containing less than 0.1% by weight of Bi as an impurity is added to the melt.
After adding 3% by weight or more of an alkaline earth metal or an alkaline earth metal compound to form an intermetallic compound of impurities Bi and an alkaline earth metal and separating this, excess alkali remaining in the molten metal is formed. A method for cleaning Al or Al alloy, which comprises removing an earth metal compound. 2. The cleaning method according to claim 1, wherein an inert gas is blown into the molten Al or Al alloy in which the intermetallic compound is formed to promote floating separation of the intermetallic compound in the molten metal. 3. The melting method according to claim 1, wherein the intermetallic compound in the molten aluminum or the molten aluminum alloy is removed by a refractory filter. 4. The cleaning method according to claim 1, wherein the alkaline earth metal compound remaining in the molten metal is removed by halogen refining. 5. An Al or Al alloy melt containing Si together with Bi as an impurity in an amount of less than 0.1% by weight, Nb, V,
At least one selected from the group consisting of Ti and Mo
5. A step of adding a certain element or at least one metal compound thereof to form an intermetallic compound of impurity Si in a molten metal and the element, and separating the intermetallic compound; A method for cleaning Al or Al alloy, which is carried out in combination with the step of separating Bi by the method described in 1.