JPH0240732B2 - RICHIUMUGANJUARUMINIUMUGOKINBANNOSEIZOHOHO - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing an aluminum alloy containing lithium, which is particularly suitable as an aircraft structural material.

Metallic lithium has a low specific gravity of 0.53, so when it is added to an aluminum alloy, the specific gravity decreases. According to simple calculations, the decrease in specific gravity is 3.93% for 1% lithium, and 10% for 2.54% lithium. Therefore, since it is possible to obtain an alloy with high specific strength and high specific modulus, it has recently been researched and developed as an aircraft structural material, and full-scale adoption is being considered for the next new passenger aircraft Boeing's 7J7 and Airbus Industries' A320. ing.

The aluminum alloy containing lithium currently under development research is Al-Li-Cu-Zr system (2090) or Al-Li-
It is broadly classified into Cu-Mg-Zr series (8090, 8091).

(Prior Art) A typical manufacturing method of a conventional lithium-containing aluminum alloy plate will be explained with reference to FIG. 1B, using an Al-Cu-Zr-Li alloy plate as an example.

That is, first, an Al-Cu-Zr alloy is melted, and metallic lithium or aluminum is added to it. A lithium master alloy (manufacturing method is exemplified in JP-A-60-110891) is added, an ingot for rolling is produced from this, the ingot is hot-rolled, cold-rolled, etc. to form a plate, and then Products are made by performing known treatments such as solution treatment, water quenching, and tempering.

Furthermore, in the specification of Japanese Patent Application No. 1982-236350 filed by the present applicant, a molten aluminum alloy is used as a cathode, a molten salt bath containing lithium chloride as a main component is used as an electrolytic bath, and a porous hollow body is placed between the two electrodes. The molten aluminum alloy used as the cathode is made to contain lithium through electrolysis. (FIG. 1C) The lithium-containing aluminum alloy thus obtained can be made into a plate by, for example, the known treatment shown in FIG. 1B described above.

Metallic lithium is chemically extremely reactive and easily reacts with oxygen and nitrogen in the air. The method of adding a lithium master alloy to molten aluminum alloy has problems that are not seen in the conventional aluminum alloy manufacturing process, and there are problems in the melting, casting, rolling, and heat treatment steps, and Japanese Patent Application No. 60-236350. Even with the method described in the book, this occurs in each step after casting.

(Problems to be solved by the invention) (1) Problems in the melting process When metallic lithium is added, metallic lithium has a low specific gravity, so it easily floats on the surface of the molten aluminum alloy and oxidizes. For this reason, methods such as covering a flux consisting of lithium chloride and lithium fluoride in an argon gas atmosphere have been taken, but even then, 10 to 20% of the expensive metallic lithium oxidizes, resulting in a deviation from the target composition. There are many. Furthermore, if the generated lithium oxide gets mixed into a plate or the like, it will significantly deteriorate the mechanical properties, so it needs to be removed, but it is difficult to completely remove it and it becomes a problem if it gets mixed into the plate or the like.

Note that if the aforementioned aluminum-lithium mother alloy is added instead of metallic lithium, the effects of oxidation are somewhat reduced, but not completely.

The method described in JP-A-60-236350 solves the above-mentioned problems.

(2) Problems in the ingot process Slabs, which are ingots for plates, are usually made using the continuous ingot method (DC casting method), which uses a large amount of water for cooling. Metallic lithium easily reacts with water, and there have been cases where lithium containing 1.5% or more in an aluminum alloy reacted and caused an explosion.The use of ethylene glycol instead of water is also being researched, making it safe and low-cost. The development of an ingot method is desired.

(3) Problems in the rolling process Aluminum alloys containing lithium are prone to processing cracks during the rolling process, and there are problems such as the optimum processing temperature range being limited.

(4) Problems in the heat treatment process Even when lithium is contained in an aluminum alloy, it oxidizes during heat treatment and its concentration at the surface decreases, resulting in a decrease in the mechanical properties of the alloy. Therefore, it is necessary to use an argon gas atmosphere, and low-cost oxidation prevention has become a problem.

(Means for Solving the Problems) The present invention for solving the above problems includes adding at least one of copper, magnesium, and zirconium to 0.05
Lithium is produced by rolling an aluminum alloy ingot containing up to 5.0% by weight to obtain an aluminum alloy plate, and then using this aluminum alloy plate as a cathode to electrolyze a molten salt containing lithium chloride as a main component. Deposited on aluminum alloy plate,
Furthermore, the present invention relates to a method for producing a lithium-containing aluminum alloy plate, which comprises diffusing lithium into the aluminum alloy plate.

The aluminum alloy may contain other metals in addition to the above-mentioned metals. Further, the rolling may be performed by cold rolling, hot rolling, or both, if necessary.

Diffusion is an aluminum alloy plate for a certain range of time, where lithium can be deposited after electrolysis outside of natural diffusion.
This is done by maintaining the temperature within a certain range.

The method of the present invention for producing a lithium-containing aluminum alloy will be explained with reference to FIG. 1A, which shows the production of an Al-Cu-Zr-Li alloy from an Al-Cu-Zr alloy.

The Al-Cu-Zr alloy is melted and then an ingot is obtained.
Next, this ingot is hot rolled and cold rolled to form an Al-Cu
- Obtain a Zr plate, use this plate as a cathode, and electrolyze with a molten salt mainly composed of lithium chloride as an electrolytic bath,
Lithium is deposited on the cathode plate and then diffused. In the above method, by performing electrolysis and diffusion at the solution treatment temperature of the alloy, solution treatment is not necessary, and after the diffusion treatment, water quenching and tempering are performed to obtain an Al-Cu-Zr-Li alloy plate. be able to.

The Al alloy produced according to the present invention is mainly used as a structural material, and must contain at least one of copper, magnesium, and zirconium.
The aluminum alloy to which the present invention is applied is not specified.

As mentioned above, if the electrolysis temperature or diffusion temperature is the same as the solution treatment temperature of the alloy, water quenching can be performed immediately without solution treatment, but diffusion treatment of alloys with a lithium content of up to about 2.6% by weight is is 500~
30 to 1 hour at 520°C.

After finishing the lithium-free aluminum alloy of the present invention to desired dimensions through the melting, ingot and rolling processes, lithium is alloyed by electrolysis, and the electrolysis temperature or diffusion temperature is adjusted to the solution temperature of this alloy. By keeping the treatment temperature the same, all problems in the melting, ingot, rolling, and solution treatment steps in conventional methods are completely solved.

FIG. 2 shows an example of an apparatus for electrolytically alloying lithium onto an aluminum alloy plate in the method of the present invention.

1 is an aluminum alloy plate on which lithium is to be electrolytically alloyed and is used as a cathode. 2 is a carbon electrode plate that acts as an anode, and chlorine is generated on the surface of the electrode plate during electrolysis. 3 is a molten electrolytic bath containing lithium chloride, 4 is a heat-resistant glass container, 5 is an ammeter, and 6 is a voltmeter.

When electrolysis is performed through direct current, metallic lithium is deposited on the aluminum alloy plate serving as the cathode, and when this state is maintained at a constant temperature for a certain period of time, lithium diffuses into the aluminum alloy plate and becomes alloyed. This is because lithium atoms are small and easily diffuse between aluminum lattices.

The lithium content in the alloy can be controlled by electrolysis conditions such as current density and electrolysis time.

In order to conduct alloying of lithium by electrolysis on a large scale and continuously, there is a method in which a long plate is continuously passed through a molten electrolytic bath and electrolysis is carried out, as in the case of applying tin plating to iron plates by electrolysis. can also be considered.

In the method of the present invention, lithium is diffused into the aluminum alloy to obtain a lithium-containing aluminum alloy, so it is practically possible to process the aluminum alloy up to a maximum thickness of about 5 mm.

(Effects) Compared with conventional manufacturing methods, the effects of the method of the present invention are extremely significant, and the benefits are large in terms of quality and economy.

(1) No expensive metallic lithium is required. Therefore, there are no problems with the storage and handling of metallic lithium, which is easily flammable and dangerous to handle.

(2) Since there is no need to add metallic lithium in the melting process, there is no need to use an argon gas atmosphere, lithium chloride, lithium fluoride, or flux. Furthermore, there is no fear that lithium oxide will be mixed into the molten metal. Therefore, it is sufficient to adopt a conventional melting method for alloys that do not contain lithium, which is economically extremely advantageous.

(3) Even in the ingot process, since alloys that do not contain lithium are handled, there is no danger of explosion, and the work can be carried out safely and economically in normal atmosphere.

(4) Since lithium is not included in the rolling process, it is extremely easy, and there is no problem of processing cracks occurring during rolling.

(5) By making the electrolysis temperature and the diffusion treatment temperature the same as the solution treatment temperature, the solution treatment in an argon gas atmosphere can be omitted and water quenching can be performed directly.

(Example) Examples of the present invention will be shown below.

Example 1 99.9% aluminum base metal, aluminum/copper 34
% master alloy and aluminum-zirconium 5% master alloy were mixed, and an aluminum alloy containing 2.7% copper and 0.14% zirconium was melted into an ingot, which was then rolled into a plate with a thickness of 2 mm. Rolling was extremely easy and could be completed with only cold rolling, and there was no need for hot rolling or intermediate annealing.

This plate was used as a cathode in the electrolytic apparatus shown in Fig. 2, and in a molten salt electrolytic bath consisting of 50% lithium chloride and 50% potassium chloride, the temperature of which was adjusted to 500-520°C, a current of 0.05 A/cm ² was applied. After electrolysis was performed for 40 minutes at a current density, diffusion treatment was performed for an additional hour. The plate after the diffusion treatment was immediately water quenched.

Analysis of the lithium content in the obtained aluminum alloy plate revealed that it was 2.23%, which meets the composition standards of 2090 alloy (Li 1.9-2.6%, Cu 2.4-3.0%, Cu 2.4-3.0%,
Zr0.08~0.15%) passed. Calculating from the theoretical amount of electricity, 3.863 Ah, required to deposit 1 g of lithium, the lithium content is 3.20%, and the current efficiency for depositing lithium alloy is 69.7%.

Example 2 99.9% aluminum base metal, aluminum/copper 34
% master alloy, aluminum/magnesium 10% master alloy, aluminum/zirconium 5% master alloy, copper 1.3%, magnesium 0.8%, zirconium
An aluminum alloy containing 0.14% was melted into an ingot and rolled into a plate with a thickness of 2 mm. Since this alloy contains magnesium, it is harder than the alloy of Example 1, and was hot rolled to a thickness of 4 mm and then cold rolled to a thickness of 2 mm.

Example 1 except that the electrolysis time was 45 minutes.
processed in the same way. The lithium content of the obtained alloy plate was 2.48%, and the composition specifications of 8090 alloy (Li2.3~2.6%, Cu1.0~1.6%, Mg0.5~1.0%,
Zr0.08~0.16%) passed.

In this case, the theoretical content of lithium is 3.60%, and the current efficiency at which lithium is precipitated into an alloy is 68.9%.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the steps of the present invention and the known technology, where a represents the present invention, b and c represent the known technology. FIG. 2 shows an example of a typical apparatus for producing a lithium-containing aluminum alloy by the method of the present invention. In the figure, 1 is an aluminum alloy plate containing lithium, 2 is a carbon anode, 3 is an electrolytic bath, 4 is a container (electrolytic cell), 5 is an ammeter, and 6 is a voltmeter.

Claims (1)

[Claims] 1. An aluminum alloy ingot containing at least one of copper, magnesium, and zirconium in a range of 0.05 to 5.0% by weight is rolled to obtain an aluminum alloy plate, and then this aluminum alloy plate is used as a cathode. A method for producing a lithium-containing aluminum alloy plate, characterized in that lithium is deposited on an aluminum alloy plate by electrolyzing a bath containing lithium chloride as a main component, and lithium is diffused into the aluminum alloy plate. 2. The method for producing a lithium-containing aluminum alloy plate according to claim 1, wherein the aluminum alloy plate after electrolysis is held at a temperature within a certain range for a certain period of time to cause diffusion. 3 Claim 1 in which the electrolysis temperature or diffusion temperature is the same as the solution treatment temperature of the alloy for the purpose
or the method for producing a lithium-containing aluminum alloy plate according to item 2.