JPH07207364A - Production of al or al alloy - Google Patents

Abstract

PURPOSE:To efficiently obtain high purity Al or Al alloy by adding a borate to molten Al or Al alloy contg. Li as an impurity and then removing the formed lithium borate. CONSTITUTION:A borate is added to molten Al or Al alloy contg. Li as an impurity to form an intermetallic compd. made of lithium borate represented by Li2B4O7, etc., and then the lithium borate is separated and removed from the molten Al or Al alloy contg. the formed lithium borate. The upper limit, of the amt. of boron in the added borate is regulated to <=3 times the stoichiometric equiv. of the boron capable of forming the lithium borate. The added borate is, e.g. magnesium borate, calcium borate or potassium borate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing Al or an Al alloy, and more particularly to a method for removing Li, which is an impurity, from a molten Al or Al alloy.

[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 significantly deteriorated. Therefore, it is necessary to reduce the impurity element as much as possible. Among them, as for the Li impurity, for example, Japanese Patent Publication No. 60-1341
There has been proposed a method in which potassium cryolite and AlF ₆ are added to No. 4 to form a compound with lithium and the compound is removed. However, this method is not industrially applicable because fluorine gas may be generated due to the use of fluoride and the removal rate is not so high.

[0003]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and removes Li from molten Al or Al alloy.
It is an object of the present invention to provide a method capable of removing impurities inexpensively and with good productivity.

[0004]

Means for Solving the Problems Al or Al of the present invention
The method for producing an alloy has a gist in that it includes a step of adding borate to an Al or Al alloy melt containing Li as an impurity to form Li borate and separating the Li borate. As the borate, one or more selected from the group consisting of magnesium borate, calcium borate, and potassium borate is used, and an inert gas is used as a carrier gas.
Blowing borate with a nozzle is a preferred embodiment of the invention. A method of injecting an inert gas into an Al or Al alloy melt in which an intermetallic compound is formed to promote floating separation of the intermetallic compound in the melt, or a method of removing the intermetallic compound through a fireproof filter It can be preferably adopted.

[0005]

The free energy for forming oxides of Al and lithium is such that Al ₂ O ₃ is -217 kJ / molO ₂ ,
i ₂ O is about the same as −223 kJ / molO ₂ . Therefore, Li cannot be removed as an oxide. As a result of earnest studies by the present inventors, they have found that lithium borate exists in the molten aluminum in a crystallized or semi-molten state and can be separated and removed by filtration without metal loss, and has reached the present invention. Li ₂ which is a typical lithium borate
The free energy of formation of B ₄ O ₇ is the melting point of aluminum 6
It is considered to be -630 kJ / molO ₂ at 60 ° C., which is likely to be formed in the molten Al.

In the present invention, borate is used to form lithium borate in the molten metal. As borate,
Magnesium borate, calcium borate, potassium borate and the like can be mentioned, and one or more of these can be used.

The amount of borate added must be adjusted according to the amount of Li contained in the molten Al or Al alloy. The lower limit for the total amount of boron in the borate is the stoichiometric equivalent capable of forming lithium borate. This is because if the amount is less than the equivalent amount, all the impurities Li cannot be removed as an intermetallic compound. A typical lithium borate is Li ₂ B ₄ O ₇ , and since Li: B = 1: 2 is a stoichiometric equivalent, 2 moles of B are required for 1 mole of Li. The weight ratio is 6.9: 20.8. However, from the experimental results described below, it was possible to remove Li considerably even with a slightly smaller amount of boron than the stoichiometric equivalent. Therefore, the amount of magnesium borate added is preferably 20 times (weight ratio) or more (0.8 equivalents or more) that of Li in the molten metal.

On the other hand, if these borates are present in an amount more than the amount of Li in the molten metal, they will rather cause contamination of the molten metal, which may lead to deterioration of the performance of Al or Al alloy obtained by inclusions. . Pure Al according to JIS
The content of boron is 0.03% or less, and that of Al alloys is 0.0
It is set to 5% or less. Therefore, the upper limit of the total amount of addition is set to 3 times or less, preferably 2 times or less, of the stoichiometric equivalent capable of forming lithium borate. The magnesium borate is 75 times or less, preferably 50 times or less, that of Li in the molten metal.

In the present invention, the borate may be added directly to the melting furnace or may be added by a method of blowing it together with an inert gas into the molten metal through a nozzle. If these compounds are mixed with an inert gas such as nitrogen, argon, He, or neon and blown into the molten metal in the form of fine bubbles, the intermetallic compounds floating in the molten metal will form bubbles. It also has the effect of being floated and easily removed. Also, dehydrogenation can be achieved at the same time.

In the present invention, Al formed by the intermetallic compound
Alternatively, the impurities Li can be removed by separating these intermetallic compounds from the molten Al alloy.
The method for removing the intermetallic compound is not particularly limited. It is preferable to remove the intermetallic compound by allowing the molten metal to stand still and allowing the intermetallic compound to settle or float up, and then to filter the molten metal with a refractory porous filter.

After forming an intermetallic compound in the molten Al or Al alloy and filtering it, refining is carried out by a known method, whereby highly pure Al or an Al alloy can be produced.

[0012]

The present invention will be described in more detail with reference to the following examples, but the following examples do not limit the present invention.
All modifications and implementations that do not depart from the spirit of the description below are included in the technical scope of the present invention.

As a raw material, JI containing 0.1% by weight of Li
S1100 system Al scrap (No. 1), a system containing 0.05 wt% (No. 2), a system containing 0.01 wt% and a 10 ton reflective melting furnace (LNG cook) were used.
Dissolved in air at 75 ° C. Magnesium borate was blown into the melt with nitrogen gas at 10 Nl / min. Mitsui Metal Tubular Filter (HD mesh 48 pieces)
Elemental analysis was performed on the sample after filtration with to obtain the lithium concentration and the boron concentration in the molten metal, and the weight ratio of magnesium borate to initial Li is plotted on the horizontal axis in FIG. In addition, the presence of 10 m ² by the fluorescent flaw detection test
The number of inclusions having a size of μm or more is shown in Table 1.

[0014]

[Table 1]

When 20 to 75 times as much magnesium borate as the initial Li weight is added, the amount of the pure Al system can be reduced to 0.001% by weight or less while suppressing the contamination of the molten metal and generating no inclusions. It was found that Li can be removed. In addition, other Al alloy system (JIS2000, 300
0, 4000, 5000, 6000, and 7000), Li can be reduced to 0.01% by weight or less, and when argon, neon, or He is used as an inert gas, or when calcium borate is used instead of magnesium borate, Similar results were obtained when using potassium borate.

[0016]

The present invention is constituted as described above, and A
It was possible to remove impurities Li in Al or Al alloy at low cost and efficiently, and to manufacture high-purity Al and Al alloy.

[Brief description of drawings]

FIG. 1 is a graph showing the amount of magnesium borate added and the lithium concentration in an Al melt.

Claims (4)

[Claims] 1. Al or Al containing Li as an impurity
A method for producing Al or an Al alloy, which comprises the step of adding borate to the molten alloy to form Li borate and separating the Li. 2. A borate such as magnesium borate,
The production method according to claim 1, wherein at least one selected from the group consisting of calcium borate and potassium borate is used. 3. The production method according to claim 1, wherein borate is blown using a nozzle using an inert gas as a carrier gas. 4. A boric acid Li in an Al or Al alloy melt.
Is removed through a fireproof filter.