JP3462617B2 - Purification method of Al or Al alloy - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for refining Al or Al alloy, and more particularly to Al or Al alloy having high cleanliness by efficiently removing Si, which is an impurity contained in molten Al or Al alloy, in the 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, due to the inclusion of impurity elements,
There is a problem that the eutectic compound becomes coarse, and the strength, toughness, surface treatability, etc. are adversely affected.
In recent years, from the viewpoint of resource saving and energy saving, Al or A
It is necessary to recycle the 1-alloy product, but unless the impurity elements are reduced as much as possible, the Al or Al alloy obtained by the recycling cannot be used.

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 Si among various impurity elements, for example, Japanese Patent Publication No. 1-27
No. 9712 utilizes the principle that when Al or Al alloy molten metal is solidified from the phase diagram, a portion having high Al purity is solidified first, and Si in the molten metal is converted into unsolidified molten metal at the final stage of solidification. A method of concentrating and removing (segregation method) has been proposed, but this method is not suitable for large-scale processing and has low productivity, and there is a problem that a large amount of Al loss is unavoidable, so that it is industrially scaled. Lacks the practicality of. See also Shokoku 6
Japanese Patent Laid-Open No. 2-10315 also proposes a method of removing Si by an electrolysis method, but this method has a very high processing cost and also lacks practicability on an industrial scale.

[0004]

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 the impurity element Si from the molten Al alloy at low cost,
It is intended to provide a method capable of obtaining high-purity Al or Al alloy.

[0005]

The structure of the refining method of Al or Al alloy according to the present invention, which has been able to achieve the above-mentioned object, is to provide Ca and / or Ca in an Al or Al alloy molten metal containing Si as an impurity. A step of adding a compound to form Si and an intermetallic compound with Ca and removing the intermetallic compound; and Al or Al after removing the intermetallic compound
The gist is to suppress the amount of Ca remaining in the molten alloy to 0.13% by weight or less.

In carrying out this method, in the molten Al or Al alloy in which the intermetallic compound is formed,
A preferred method is to blow an inert gas to promote floating separation of the intermetallic compound in the molten metal, or to remove the intermetallic compound through a fireproof filter. The Ca compound used in this method includes silicates, carbides, fluorides, borides, chlorides,
Sulfides are used as preferable ones, and they can be used alone or in combination of two or more kinds.
In addition, Al or A from which Si is removed by the above method
The amount of Ca remaining in the molten 1-alloy is preferably controlled to 0.13% by weight or less in order to more reliably enhance the strength, toughness, corrosion resistance, moldability and the like of the Al or Al alloy product.

[0007]

Function Al or Al alloy is extremely easy to oxidize, and its oxidation tendency is larger than that of Si. Therefore, Al or A
It is known that it is impossible to remove Si as an oxide from a molten 1-alloy. However, while the present inventors proceeded with research aiming at the development of an efficient Si removal method,
Si easily forms an intermetallic compound with an alkaline earth metal such as Ca (see FIG. 2: free energy of formation of Si compound ΔG), and the intermetallic compound is Al or A.
l It exists as a solid crystallized substance or a semi-molten state in the molten alloy and can be separated and removed relatively easily by filtration or the like.
Alkaline earth metal is not only added as a single metal or as an alloy having an alkaline earth metal as a mother alloy, but also silicates, carbides, fluorides, borides, chlorides, and sulfides of 1
It has been found that even when added as a seed or more, an intermetallic compound is similarly formed with Si and can be easily separated and removed from the molten Al or Al alloy melt.

That is, in the present invention, an alkaline earth metal and / or an alkaline earth metal compound such as Ca is added to an Al or Al alloy melt containing Si as an impurity element to form an intermetallic compound with Si. By
Al and / or Al alloy is to be removed from the molten metal, and the addition amount thereof is the impurity S mixed in the molten metal.
It is necessary to increase or decrease according to the amount of i.

A preferred lower limit of the amount of the alkaline earth metal or its compound added as an alkaline earth metal is a stoichiometric equivalent amount capable of forming an intermetallic compound with Si contained in Al or an Al alloy. If the amount is less than the equivalent, it becomes impossible to remove all of the impurity Si as an intermetallic compound. For example, when adding Ca to form an intermetallic compound of Ca and Si, the stoichiometric equivalent is Ca: Si =
Since it is 1: 1, the lower limit of the preferable addition amount of Ca is
It is 1 mol with respect to 1 mol of Si contained in Al or Al alloy. This is converted to the weight ratio and Ca: Si =
Although it is 40.09: 28.086, actually, considering that there are few reaction fields for forming an intermetallic compound, it is preferable to allow 1.5 times or more equivalent amount of the alkaline earth metal to be present. .

On the other hand, if the alkaline earth metal is added in an excessively large amount with respect to the amount of Si in the molten metal, it will rather cause contamination of the molten metal, which may lead to deterioration of the performance of the obtained Al or Al alloy. Therefore, the amount of the alkaline earth metal or its compound added is, in terms of alkaline earth metal, about 3 times or less the stoichiometric equivalent amount capable of forming an intermetallic compound with Si,
It is more preferable to suppress the amount to about 2 times or less of the equivalent amount, and when showing the specific preferable addition amount, the preferable addition amount range of Ca to 1.4 parts by weight of Si contained in the molten metal is 1.4 to 2. The range is 9 parts by weight.

In the above description, the case where an alkaline earth metal forms an intermetallic compound with a stoichiometric equivalent amount of Si has been described. However, depending on the treatment temperature and the like, Si and Ca form an intermetallic compound at an equimolar ratio. Not necessarily, for example, Ca ₂ S
i, Ba ₂ Si, Mg ₂ Si, CaSi ₂ Al ₂ , Ba
Si ₂ Al ₂ , MgSi ₂ Al _2, etc. may be produced alone or in a mixed state. Therefore, in this case,
It has been confirmed that a similar calculation is performed according to the intermetallic compound to be formed, and the addition amount of the alkaline earth metal or the alkaline earth metal compound is calculated, and thereby the theoretical result can be obtained.

In the present invention, an intermetallic compound with Si is produced by adding the alkaline earth metal or its compound as described above, and the intermetallic compound is Al or Al.
By separating and removing from the molten alloy, the removal of the impurity Si can be achieved. The method of removing the intermetallic compound is not particularly limited, but as a general method, since the intermetallic compound has a higher specific gravity than Al or an Al alloy, the molten metal is allowed to stand still as "molten metal quenching". After sedimentation, the method of collecting the supernatant by slanting, the method of filtering the intermetallic compound through a refractory filter, and the like are recommended as preferable methods. In addition, some of the intermetallic compounds may be suspended in the molten metal depending on the kind of the intermetallic compound. In such a case, nitrogen, argon, He,
It is also one of the preferable methods to blow inactive gas such as neon in the form of fine bubbles and float the bubbles to levitate and remove the complex oxide, and if this method is adopted, dehydrogenation is also promoted at the same time. You can also enjoy the advantage of being able to.

As described above, the present invention is characterized in that Si contained as an impurity in Al or an Al alloy is separated and removed as an intermetallic compound with an alkaline earth metal, which is added here. It is conceivable that a part of the alkaline earth metal formed is taken into the Al or molten Al alloy. Then, among the alkaline earth metals, Ca is easy to form an intermetallic compound with Al and further with metals such as Mg and Cu. This intermetallic compound does not substantially affect the physical properties if it is fine, but if a coarse intermetallic compound is formed, it will affect the formability, strength, toughness, corrosion resistance, etc. of Al or Al alloy. It is considered to have a considerable adverse effect, so it is necessary to give due consideration to them.

From this point of view, when the effect of the amount of Ca remaining in the molten Al or Al alloy on the amount of intermetallic compounds produced and the particle size thereof was investigated, the results shown in FIG. 3 were obtained. As is clear from this figure, when the Ca concentration exceeds 0.13% by weight, the amount of the produced intermetallic compound tends to increase sharply and tends to become significantly coarse.

As described above, when the intermetallic compound becomes coarse and its amount increases, stress concentration occurs when the coarse intermetallic compound receives stress, which serves as a starting point of fracture and deteriorates strength and toughness. Moreover, the intermetallic compound and Al
Electrochemical inhomogeneity with the matrix causes adverse effects on corrosion resistance. Furthermore, in the case of applying to a use requiring a large processing amount and excellent surface smoothness such as a magnetic disk, a photosensitive drum, a substrate for printing plate making, etc., even if the amount of the coarse intermetallic compound is very small, It causes work cracks and surface defects.

Therefore, in order to avoid such obstacles due to the formation of coarse intermetallic compounds, the amount of Ca remaining in the Al or Al alloy molten metal after the Si removal treatment is 0.13% by weight or less, and particularly excellent workability and When applied to applications where surface accuracy is required, it is desirable to keep it to about 10 ppm or less.

The melting temperature of Al or Al alloy in the present invention may be a usual temperature of 700 to 900 ° C. After forming the intermetallic compound and removing the intermetallic compound, refining is performed by a known method. By this, high-purity Al or Al alloy can be manufactured.

[0018]

EXAMPLES Hereinafter, the constitution and effects of the present invention will be described in more detail with reference to examples. However, the present invention is not limited by the following examples and does not deviate from the spirits of the preceding and the following. All modifications within the scope are included in the technical scope of the present invention.

Example 1 JIS-110 containing Si: 1.0 wt% as a raw material
Using pure Al-based scrap of 0, melting temperature: 720
℃, melting furnace: adopted a method of melting in the atmosphere in a reflection type melting furnace (heavy oil burning) of 10 tons, at this time, a predetermined amount of Ca or Ca compound was added to the molten metal (blown with N ₂ gas)
After that, the produced Si-Ca intermetallic compound was removed by filtration with a 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 based on the amount of the molten metal was blown in with N ₂ gas: flow rate 0.6 m ³ / h for 30 minutes), and then semi-continuous casting was performed to obtain a diameter of 300 mm. The billet (4 pieces) was manufactured. Elemental analysis of the molten metal sampled in the above treatment step was carried out, and those having a Si residual concentration of 200 ppm or less were accepted. Regarding the residual Ca concentration, those having a concentration of 10 ppm or less, which is required when applied to applications such as printing plate making substrates, were accepted.

Further, for each of the obtained billets, a hot work cracking test (◯: cracking occurrence rate of less than 0.1%, ×: cracking 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 ), coatability test of cold-rolled sheet (○: surface defect occurrence rate of 0.1% or less, x:
The surface defect occurrence rate was over 0.1%), and the respective performances were evaluated. The results are shown in Table 1.

[0021]

[Table 1]

Example 2 JIS-400 containing Si: 3.0% by weight as a raw material
50 wt% of Al alloy scrap of No. 0 is used together with Al ingot, and the melting temperature: 720 ° C., melting furnace: 10 tons, is used for atmospheric melting in a reflective melting furnace (heavy oil fired). Alternatively, after a predetermined amount of Ca compound was added (blown with N ₂ gas), the produced Si—Ca intermetallic compound was removed by levitation separation, and then the molten metal was sampled for elemental analysis. The molten metal is subsequently refined (Ar gas is blown at a flow rate of 0.6 m ³ / h in 30 minutes)
After that, semi-continuous casting was performed to manufacture a billet (4 pieces) having a diameter of 300 mm. Elemental analysis of the molten metal sampled in the above treatment step was performed, and those having a Si residual concentration of 200 ppm or less and a Ca residual concentration of 10 ppm or less were accepted. Also, for each billet obtained,
A hot work cracking test, a cold-rolled sheet strength test, and a cold-rolled sheet paintability test were performed in the same manner as in Example 1 above, and the respective performances were evaluated. The results are shown in Table 2.

[0023]

[Table 2]

As is clear from Tables 1 and 2, when an appropriate amount of Ca or a Ca compound is added to the molten Al or Al alloy and treated, Si contained in the molten metal as an impurity element is a Si--Ca system. Al or an Al alloy that is efficiently removed as an intermetallic compound and has high cleanliness can be obtained.

FIG. 1 is a graph showing the relationship between the amount of added Ca and the amount of Si—Ca-based intermetallic compound produced with respect to the amount of Si contained in Al or Al alloy molten metal.
As is clear from this graph, Si can be removed efficiently by adding a slightly larger amount (about 1.5 times mol) of Ca than the equimolar amount to the Si amount. Even if the amount of Ca added is increased above the above
It can be seen that no increase in the amount of -Ca-based intermetallic compound is observed, and excess Ca is mixed as an impurity in the molten metal, so that further addition is not preferable.

In the above, a specific example of a method of adding Ca or a Ca compound to remove Si is shown.
Similar effects of removing Si can be obtained by adding a, Mg, or a compound thereof.

Example 3 As shown in Table 3, various Al or Al alloy scraps were used and Si was removed by treating them with an appropriate amount of Al-Ca alloy, and various component compositions shown in Table 3 were obtained. It was regenerated into Al or molten Al alloy. An ingot was manufactured using each of the obtained molten metals, hot-rolled and cold-rolled to a final plate thickness of 2.5 mm, and then the respective physical properties and corrosion resistance were examined. For 6000 series Al alloys, after solution treatment at 520 ° C for 30 minutes after rolling, 170 ° C
Aged heat treatment for 8 hours to obtain T6 material.
For the 00-based Al alloy, it was treated at 480 ° C. for 30 minutes, then 170 ° C. for 2 hours and 125 ° C. for 2
Aged heat treatment for 4 hours was performed to obtain T6 material.

A strength test (JI
Tensile test by S5 test piece), toughness test (JIS
An impact test using a No. 4 test piece) and a corrosion resistance test (salt spray test) were performed. In the evaluation of the tensile test and the toughness test, the value of the test material is 80% or less based on each value of the equivalent material having a Ca concentration of 0%, and the corrosion resistance test is performed in the same manner. 120% reduction in weight due to corrosion, based on the value of equivalent material with a concentration of 0%
The above was designated as x. The results are shown in Table 4.

[0029]

[Table 3]

[0030]

[Table 4]

As is clear from Tables 3 and 4, the residual Ca concentration in the recycled product is 0.13% by weight or less,
It can be seen that there is no problem in quality when applied to general purposes.

[0032]

The present invention is constituted as described above, and A
It was possible to efficiently remove Si 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 summarizing the relationship between the amount of added Ca and the amount of Si—Ca-based intermetallic compound formation with respect to the amount of Si contained in Al or Al alloy molten metal.

FIG. 2 is a graph showing the free energy of formation of an intermetallic compound with Si.

FIG. 3 is a graph showing the results of examining the effect of the Ca content in an Al alloy product on the number and particle size of intermetallic compounds formed in the Al alloy product.

Front page continuation (72) Inventor Kazutaka Kunii 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo Kobe Steel Co., Ltd., Kobe Research Institute (72) Inventor Kenji Osumi 1 Takatsuka-dai, Nishi-ku, Kobe-shi, Hyogo 5-5 No. 5 Kobe Steel Co., Ltd. Kobe Research Institute (72) Inventor Yo Kojima 1603-1 Kamitomioka-cho, Nagaoka-shi, Niigata (56) References JP-A-1-279712 (JP, A) ( 58) Fields investigated (Int.Cl. ⁷ , DB name) C22B 1/00-61/00

Claims (4)

(57) [Claims] 1. Al or Al containing Si as an impurity
During the molten alloy, the addition of Ca and / or Ca compound, a Si to form Ca intermetallic compound saw including a step of removing this by, or Al after removal of the said intermetallic compound
Or 0.13% by weight of Ca remaining in the molten Al alloy
A method of refining Al or Al alloy characterized by suppressing to the following . 2. A purification method according to claim 1 to promote the flotation of the intermetallic compound formed of Al or blowing a molten Al alloy in an inert gas, said intermetallic compound in the molten metal. 3. A purification method according to claim 1 or 2 the intermetallic compound of the intermetallic compound formed of Al or Al alloy melt, is removed by using a refractory filter. 4. The purification method according to claim 1, wherein the Ca compound is one or more of silicate, carbide, fluoride, boride, chloride and sulfide.