JPH08120359A - Method for refining aluminum or aluminum alloy - Google Patents

Abstract

PURPOSE: To reproduce a higher purity of Al than Ti-containing Al by reacting carbon or carbide with molten Al containing Ti as impurity and separating Ti as the carbide from the molten Al. CONSTITUTION: Scrap, etc., of Al or Al alloy containing Ti as impurity is melted and powdery, granular, bar-like, platy or bulky carbon or carbide of SiC, B4 C, etc., is added at >=0.3wt.% in terms of C to the Ti quantity in the Al and brought into contact with the molten metal to make the Ti as the carbide or the Ti-containing composite carbide. In this case, the production of the Ti carbide or the Ti-containing composite carbide is promoted by holding the molten Al to the high temp. at 1200-1500 deg.C and also, pressurizing. Inert gas is blown in this molten Al, and after separating and floating up the Ti carbide or the Ti-containing composite carbide from the molten Al, the Ti carbide, etc., is filtered and separated through a fire-resistant filter. Alternatively, the Ti-containing molten Al is passed through carbon or carbide-filling filter and the Ti is separated and removed as the carbide, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of refining Al or Al alloy, and more particularly, Al or Al alloy having high cleanliness by efficiently removing Ti, which is an impurity contained in molten Al or Al alloy, in a melting stage. Is about how to get.

[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, the inclusion of impurity elements causes problems such as coarsening of the eutectic compound, resulting in strength, toughness,
There is a problem that the surface treatability is adversely affected. In recent years, from the viewpoint of resource saving and energy saving, Al or Al
Although it is necessary to recycle alloy products, A can be obtained by recycling unless impurity elements are reduced as much as possible.
l or Al alloy becomes unusable.

From such a point, various studies have been conducted on a method of removing an impurity element from Al or an Al alloy, and a part of them has been put into practical use. Focusing on Ti among various impurity elements, for example, Japanese Patent Laid-Open No. 4-14
Japanese Patent No. 7928 discloses a method in which the melting temperature of Al or an Al alloy is set to be low and the mixing and mixing of Ti itself is suppressed, but this method can be applied only to Ti mixed in a solid state. It cannot be applied to the removal of Ti once melted and mixed in Al or Al alloy molten metal, and the Ti content increases as the scrap compounding amount increases.

In addition, in Japanese Patent Publication No. 2-500600,
A method is disclosed in which metals such as Mn, W, and V are added together with Cr and Mn to form and remove an intermetallic compound with the impurity Ti. However, this method is also pointed out to have a problem that the treatment efficiency is low because the reaction rate of the formation of the intermetallic compound is slow and that the molten metal is contaminated by the addition of the additional element.

Further, Japanese Patent Application Laid-Open No. 4-56744 discloses A
Although there is a description that the impurity Ti in the 1-alloy reacts with B and is removed as boride, even if it is attempted to utilize this for the removal of Ti, the reaction rate of boride formation is slow and the treatment efficiency is low. When a large amount of B is added in order to improve the processing efficiency, the excess B is mixed and the molten metal is contaminated instead.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and its purpose is to
l or a method capable of efficiently removing Ti, which is an impurity element, from the molten Al alloy at a low cost,
An object of the present invention is to provide a refining method capable of obtaining high-purity Al or Al alloy.

[0007]

The structure of the refining method of Al or Al alloy according to the present invention, which has been able to achieve the above object, comprises contacting an Al or Al alloy molten metal containing Ti as an impurity with carbon and / or carbide. The main point is to include the step of producing Ti carbide and / or Ti-containing composite carbide and separating the same.
The carbon and / or carbide used here includes
A powdery material, a granular material, a rod-shaped material, a plate-shaped material, a lumped material or the like can be used, and these carbon and / or carbides are 0.3 in terms of C with respect to the Ti content in the Al or Al alloy molten metal. By adding at least wt%, the impurity Ti can be efficiently removed as a carbide.

As the carbide, for example, SiC, B ₄
C, Al ₄ C ₃ , VC, Ni ₃ C, Mo ₂ C and the like are exemplified, and these can be used alone or in combination of two or more if necessary.

In carrying out the above method, the temperature of the molten metal is set to 1200 to 150 before or after the carbon and / or carbide is brought into contact with the molten aluminum or aluminum alloy.
Hold at 0 ℃, or 1kgf / cm
^{It is} preferable to apply a pressure of about ² or more because the reaction of forming Ti carbide and / or Ti-containing composite carbide is promoted.

Further, an inert gas is blown into the Al or Al alloy molten metal produced by the Ti carbide and / or the Ti-containing composite carbide, and the Ti carbide and / or T in the molten metal is injected.
By adopting a method of promoting floating separation of the i-containing composite carbide, a method of removing the intermetallic compound through a refractory filter, or the like, it is possible to efficiently remove them.

Further, as another example of using carbon and / or carbide in the form of powder, granules, rods, plates or agglomerates, a layer filled with these powders or granules, etc. Al or A is passed through a molten metal of Al or Al alloy or is applied to a filter formed of carbon and / or carbide.
The molten Al alloy is passed through and Ti in the Al or molten Al alloy
A method of removing C by reacting with these carbons and / or carbides is also recommended as a preferable method. in this case,
The temperature of the molten metal when passing through the filter is 1200 to 1500 ° C,
If the pressure is increased to about 1 kgf / cm ² or more, Ti contained in the molten metal can be removed more efficiently.

[0012]

[Function] Since Ti contained as an impurity in Al or Al alloy molten metal easily forms an intermetallic compound with Al, T
It is considered almost impossible to remove i as an intermetallic compound with a metal other than Al. However, as the present inventors describe the development of an efficient Ti removal method and proceed with the research, Ti contained as an impurity forms a carbide or a composite carbide that is more stable than Ti-Al with C or a carbide. The Ti carbide or the composite carbide is A
It was found that it exists as a solid in the molten metal of Al or Al alloy and can be separated and removed relatively easily by filtration or the like.
The present invention has been completed based on these findings.

That is, according to the present invention, an Al or Al alloy molten metal containing Ti as an impurity element is brought into contact with C and / or a carbide to form a Ti carbide and / or a Ti compound carbide, and these are Al and / or Al. It is to be removed from the molten alloy. Here, C means C: 100% carbon or graphite, etc., and carbide means C as a main component and a small amount of SiO ₂ , MgO,
Carbon-based mixture containing Al, Co, TiO _2, etc., or SiC, B ₄ C, Al ₄ C ₃ , VC, Ni
_A general term for metal carbides that can form stable composite carbides with Ti such as ₃ C and Mo ₂ C.

The most general method for bringing these carbons and carbides into contact with the molten Al or Al alloy is to add powdery, granular, plate-like, or lumpy carbon or carbide to the molten Al or Al alloy and mix them. Method, a method of passing a molten Al or Al alloy melt through a packed bed of granular materials or agglomerates of carbon or carbide, or a filter formed of carbon or carbide, forming a gutter or baffle plate with a carbonaceous material, A method of bringing them into contact with Al or a molten Al alloy, or the like is adopted, and Ti contained in Al or an Al alloy reacts with C or a carbide to form an insoluble carbide or a composite carbide by these methods, or It adheres to the surface of carbide or the like as carbide or composite carbide. Therefore, if these are separated and removed from the molten metal by filtration or the like, Ti can be efficiently removed. Further, when the above method is adopted, by appropriately adjusting the passing speed of the molten metal, the passing molten metal can be obtained as the one having high cleanliness with the impurities Ti removed.

When carbon or carbide is added to the molten metal in the form of powder or particles, it may be added in a chemical equivalent amount with respect to the amount of Ti contained in the Al or Al alloy molten metal. Considering the combustion loss and the like, it is desirable to add about 1.5 times or more in terms of equivalent ratio. Unreacted carbon and carbides float to the surface of the molten metal almost as they are and are removed from the molten metal together with the carbides in the filtration step, so there is no upper limit to the amount added, but excessive addition is economically wasteful. It is desirable to suppress the equivalence ratio to about 3 times or less.

Carbide etc. are added as a plate or a lump,
Alternatively, a gutter or baffle is formed from carbide and Ti
In the case of adhering and removing carbon as a carbide, it is desirable to sufficiently increase the contact area with the molten metal in order to increase the contact rate with the molten metal and to add sufficient stirring to the molten metal. Then, when the amount of adhered carbides on these surfaces becomes saturated, the carbides may be replaced with new carbides. In the present invention, as described above, carbon carbide or carbide is brought into contact with the molten metal to be treated to generate Ti carbide or Ti compound carbide, and these are separated and removed from the Al or Al alloy molten metal to remove the impurity Ti. Can be achieved.

The method for removing the Ti carbide and the composite carbide is not particularly limited, but as a general method, the one in which the Ti carbide is formed and adhered to the surface layer portion such as powder or particles is lighter than the molten aluminum. Since it floats on the surface of the molten metal, the molten metal may be calmed and removed from the surface of the molten metal at the end of the treatment, or filtered by a fire resistant filter or the like. At this time, one of the preferable methods is to blow an inert gas such as nitrogen, argon, He, or neon into the molten metal in the form of fine bubbles to promote the floating of the bubbles and the floating of the carbide. By adopting, it is possible to enjoy the advantage that dehydrogenation can be promoted at the same time.

In the case of using lump-shaped or plate-shaped carbides, it is sufficient to remove those lumps or plate-like materials that have been formed and adhered to the surface of Ti carbide after the treatment, and are removed from the molten metal surface. In the case of performing Ti removal using a baffle plate, it may be repeatedly used until the surface thereof is saturated with Ti carbide or the like, and replaced with a new gutter or baffle plate immediately before the saturation. The same applies to the case where Ti carbide or the like is generated and adhered to the surface of the granular or lump by passing the molten metal into the granular or lump carbide layer, and the new surface is formed before the surface of the granular or the like is saturated with Ti carbide or the like. It may be exchanged for granules.

By the way, when removing Ti as Ti carbide or Ti composite carbide by the above method, the effect of temperature and pressure during the treatment on the Ti removal efficiency was examined. As a result, the treatment temperature was 1200. It was confirmed that if the treatment system is set to not less than 0 ° C. and the treatment system is appropriately pressurized, the production rate of the Ti carbide and the Ti compound carbide is increased, and the Ti removal rate is further enhanced. Incidentally, FIG. 2 is a graph showing the results of examining the relationship between the treatment temperature and the production amount of Ti carbide or Ti compound carbide. As is clear from this graph, the treatment temperature is 1
At 200 ° C. or higher, it is observed that the amount of the above-mentioned carbide formed obviously increases sharply. From this, it can be confirmed that increasing the treatment temperature to 1200 ° C. or higher is effective in increasing the Ti removal rate more effectively. However, if the processing temperature becomes excessively high, the oxidation loss of Al increases, so it is preferable to suppress it to about 1400 ° C. or less. Particularly preferable treatment temperature is 1200 to 14 in order to effectively increase the Ti removal rate while minimizing the Al loss.
It is in the range of 00 ° C.

Further, if the reaction system at the time of forming the carbide is appropriately pressurized, preferably about 1 kgf / cm ² or more, more preferably 1.5 kgf / cm ² or more, the formation of the above carbide is further accelerated. It is preferable because the Ti removal rate can be further increased.

Since the above heating or pressurization is carried out for the purpose of accelerating the formation of carbides, the timing is the time when carbon and / or carbides are brought into contact with the molten Al or Al alloy and the carbon and carbides are removed. It is possible to employ either a method of increasing the temperature and pressurizing after adding, or a method of once increasing the temperature and pressurizing and then adding carbon or carbide. Pressurization is most commonly performed by pressing the molten metal to be treated from the surface of the molten metal. For example, as described above, the formation and removal of carbides are performed simultaneously by passing through a packed bed of carbon or the like or a carbonaceous filter. When the method is adopted, it is also possible to obtain a moderately negative pressure on the packed bed or the outlet side of the filter and obtain a moderately pressurized state by back pressure.

After removing the impurity Ti as described above, high purity Al or Al alloy can be produced by refining by a known method using a potassium chloride type flux or the like, if necessary.

[0023]

EXAMPLES The constitutions and effects of the present invention will be specifically described below with reference to examples, but the present invention is not limited by the following examples and can be adapted to the gist of the preceding and the following. It is of course possible to make changes within the scope of the invention, and all of them are included in the technical scope of the present invention.

Example 1 As a raw material, JIS-containing Ti: 1.0 to 10% by weight
Melting temperature: 7 using 1100 pure Al-based scrap
50 ° C, melting furnace: A method of melting in an induction melting furnace of 3 tons was adopted. At this time, the molten metal had a plate shape (300 mm ^w x 1
000 mm ^l × 50 mm ^t ) or powdery (average particle size: 100 μm) carbon was added in an amount of 0.1 to 200% by weight with respect to the amount of Ti in the molten metal, and the mixture was stirred for 90 minutes. And the powdered C was removed by passing the melt through a refractory filter. As another method, the molten metal was passed through a 300 mesh filter made of C, and Ti contained in the molten metal was removed by adhering it as Ti carbide on the mesh surface of the filter.
After that, the molten metal was sampled for elemental analysis.
The molten metal is subsequently refined (KCl-based flux: 0.1% by weight based on the amount of molten metal, N ₂ gas: flow rate 0.6 m ³ / h, 3
(Blow-in for 0 minutes), then perform semi-continuous casting,
A billet (4 pieces) having a diameter of 300 mm was manufactured. Elemental analysis of the molten metal sampled in the above-mentioned molten metal treatment step was performed, and if the residual Ti concentration was 0.02% or less and the C concentration was less than 0.04%, which was the defect limit, it was passed (○), T
Only when the i concentration is 0.02% or less and the C concentration is 0.04% or more, or when the initial Ti concentration is 0.1% or less, the treated Ti concentration is 0.02% or less and the C concentration is Those with less than 0.04% are semi-passed (△), T after processing
A sample having an i concentration of more than 0.02% was regarded as a failure (x).

Further, for each of the obtained billets, an Al plate having a thickness of 0.3 mm was subjected to hot and cold rolling,
Hot work cracking test (○: cracking occurrence rate is less than 0.1%, ×:
Crack occurrence rate of 0.1% or more), cold-rolled sheet strength test (○: 12
kgf / mm ² or more, x: less than 12 kgf / mm ² ),
Each cold-rolled sheet was subjected to a paintability test (∘: surface defect occurrence rate of 0.1% or less, x: same occurrence rate of more than 0.1%) to evaluate each performance. The results are shown in Table 1. Incidentally, when a similar experiment was conducted using a carbide instead of carbon in the above,
Almost similar results were obtained.

[0026]

[Table 1]

Example 2 JIS-30 containing 0.06% by weight of Ti as a raw material
Melting temperature: 75 using 04 Al alloy scrap
0 ° C, melting furnace: A method of melting in an induction melting furnace of 4 tons was adopted. At this time, the molten metal had a plate shape (250 mm ^w x 80 mm).
0 mm ^l x 60 mm ^t ) or powder (average particle size: 2)
(00 μm) of carbon with respect to the amount of Ti in the molten metal is 0.1 to
After adding 200% by weight and stirring for 45 minutes, the plate C was removed from the molten metal surface, and the powder C was removed by passing the molten metal through a refractory filter. Also, as another method,
The molten metal was passed through a 250-mesh C filter, Ti contained in the molten metal was removed by adhering it as Ti carbide on the mesh surface of the filter, and then the molten metal was sampled for elemental analysis. The molten metal was subsequently subjected to refining (KCl-based flux: 0.1% by weight of the molten metal was blown with nitrogen gas), and then semi-continuous casting was performed to manufacture a billet having a diameter of 300 mm (4 pieces). Elemental analysis of the molten metal sampled in the above treatment step was carried out, and those having a Ti residual concentration of 0.02% or less were accepted. For each of the obtained billets, a hot work cracking test, a cold rolled sheet strength test, and
Each cold-rolled sheet was subjected to a paintability test to evaluate its performance.
Table 2 shows the results.

[0028]

[Table 2]

As is clear from Tables 1 and 2, when an appropriate amount of C or carbide is added to an Al or Al alloy molten metal for treatment or the molten metal is passed through a filter made of carbon, the molten metal is melted. Ti contained as an impurity element therein is efficiently removed as Ti carbide or Ti compound carbide, and Al or Al alloy having high cleanliness can be obtained.

FIG. 1 is a graph showing the relationship between the amount of addition of granular or powdery C and the residual Ti concentration with respect to the amount of Ti contained in Al or Al alloy molten metal.
As is clear from this graph, by adding about 0.3% by weight or more of C to the amount of Ti, S
It can be seen that i can be removed efficiently, and even if the amount of C added is increased more than that, a decrease in Ti concentration can hardly be expected, and addition of more than that is economically wasteful.

In the above, a specific example of the method of removing Ti by using C is shown, but carbides (SiC, B ₄
The same Ti removing effect can be obtained by using C, Al ₄ C ₃ , VC) or the like.

Example 3 In the above Example 1, powder (average particle diameter: 100 μm)
m) Ti was removed in exactly the same manner as in Example 1 except that the amount of carbon added was set to 10 times the amount of Ti in the molten metal and the treatment temperature was changed in the range of 800 to 1400 ° C.
The residual Ti concentrations in the melts were compared.

After the powdered carbon has been added, when the molten metal is passed through a refractory filter to remove the carbides, the treatment vessel is closed and pressurized air is blown into the inside of the molten metal so that 1.5 kgf / The experiment was conducted in exactly the same manner as above except that filtration was performed after applying a pressure of cm ^2.
The i concentration was checked.

The results are shown in FIGS. 2 and 3, and it can be seen that the Ti removal rate can be more effectively increased by increasing the treatment temperature to 1000 ° C. or higher, more preferably 1200 ° C. or higher (FIG. 2). . Further, it can be seen that the Ti removal rate can be further increased by appropriately pressurizing the molten metal (FIG. 3).

[0035]

The present invention is constituted as described above, and A
It was possible to efficiently remove Ti contained as an impurity element in 1 or Al alloy at low cost, and to produce high-purity Al or Al alloy.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the amount of added C and the residual Ti concentration with respect to the amount of Ti contained in Al or Al alloy melt.

FIG. 2 is a graph showing the results of examining the influence of the treatment temperature on the production rate of Ti carbide or Ti composite carbide.

FIG. 3 is a graph showing the results of examining the effect of temperature and pressure during Ti removal treatment on the residual Ti concentration in the molten metal.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenji Osumi 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo Prefecture Kobe Steel Research Institute, Kobe Steel Co., Ltd.

Claims (10)

[Claims] 1. Al or Al containing Ti as an impurity
The molten alloy is brought into contact with carbon and / or carbide, and T
A method for purifying Al or an Al alloy, which comprises the step of producing an i-carbide and / or a Ti-containing composite carbide and separating the same. 2. Carbon and / or carbide is a powder,
The refining method according to claim 1, wherein the granular or rod-shaped material, the plate-shaped material or the lump-shaped material is added to the molten Al or Al alloy and brought into contact therewith. 3. Carbon and / or carbide is 0.3 in terms of C with respect to the Ti content in Al or Al alloy molten metal.
The refining method according to claim 2, wherein the amount is at least wt%. 4. The carbide is SiC, B ₄ C, Al ₄ C
The purification method according to claim 1, wherein the purification method is at least one selected from ₃ , VC, Ni ₃ C, and Mo ₂ C. 5. The molten aluminum or Al alloy containing carbon and / or
Alternatively, the molten metal temperature is maintained at 1200 to 1500 ° C. before or after the contact with the carbide to promote the formation of the Ti carbide and / or the Ti-containing composite carbide.
5. The purification method according to any one of 4 to 4. 6. A molten aluminum or Al alloy containing carbon and / or
Alternatively, the temperature of the molten metal is maintained at 1200 to 1500 ° C. before or after the contact with the carbide, and the molten metal is pressurized to accelerate the formation of the Ti carbide and / or the Ti-containing composite carbide. The purification method according to Crab. 7. The float separation of Ti carbide and / or Ti-containing composite carbide in the melt is promoted by blowing an inert gas into an Al or Al alloy melt produced by Ti carbide and / or Ti-containing composite carbide. 7. The purification method according to any one of 6 to 6. 8. The molten Al or Al alloy produced by the Ti carbide and / or the Ti-containing composite carbide is passed through a refractory filter, and the Ti carbide and / or the Ti-containing composite carbide is removed by the filter. The purification method according to any one. 9. A molten metal of Al or Al alloy in a powder-, granular-, rod-shaped, plate-shaped or lump-shaped layer filled with carbon and / or carbide, or a filter formed of carbon and / or carbide. Through the Al or A
The refining method according to claim 1, wherein Ti in the molten alloy is removed by reacting it with carbon and / or carbide. 10. The molten metal temperature when passing through the filter is 120.
The purification method according to claim 9, wherein the pressure is 0 to 1500 ° C and the pressure is 1 kgf / cm ² or more.