JP2000288691A - Production of cast alkali metal ingot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the occurrence degree of shrinkage hole and shrinkage pipe that the center part is extremely recessed at the solidified time by cooling molten alkali metal in a forming vessel while regulating a Y value having a specified relation in specified range. SOLUTION: In the case of using H (mm) for height of the cast alkali metal, (d) (mm) for inner diameter of the forming vessel at H/2 height, (h) (mm) for effective height of a cooling jacket, the molten alkali metal is cooled under condition, in which Y value in the equation Y=(H-h).d/h (mm) becomes 3-25, desirably 8-15. Coolant is circulated in the cooling jacket 7 and the inner part in the forming vessel body 2 is replaced with argon gas and the molten alkali metal having a prescribed temp. is poured by a prescribed quantity. In the case of lithium, molten lithium is held at e.g. 200-270 deg.C and in the case the total casting quantity is e.g. 0.5-3.0 kg, the casting speed is desirable to be 10-30 g/sec. The forming vessel desirably has a truncated conical shape and as the desirable coolant oil is used at 15-40 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cast alkali metal ingot which prevents the occurrence of shrinkage holes or shrinkage cavities in which the center of the upper part of the ingot is dented when a molten alkali metal is poured into a molding machine and cast. For example, the present invention relates to a method for producing a cast lithium ingot.

[0002]

2. Description of the Related Art Metallic lithium is used as an electrode material for lithium batteries. To form a lithium ingot into foil, it is required that the ingot has no grooves or the like on the ingot. However, alkali metals such as lithium have a large volume expansion coefficient at the time of melting.
The volume increases by about 5%, and conversely, when it solidifies, the volume decreases. On the contrary, unless the cooling rate is extremely high, the molten alkali metal is usually allowed to cool naturally in a molding machine such as a deep vat. It has been known that when coagulated by solidification, as shown in FIG. 1, a phenomenon such as a shrinkage hole or a shrinkage cavity in which the center is dented occurs. FIG. 1 shows a state in which the mold is cast into a molding machine and a state in which shrinkage holes are generated.

[0003] Conventionally, the following prior art is known for solidification of molten metal. JP-A-52-113327
In the publication, an ingot having a large number of through-holes on the peripheral surface, a sand mold for air permeability fitted in the inner cylinder, and an outer cylinder surrounding the inner cylinder with a gap therebetween is used as a steel ingot mold. And a method for controlling the solidification rate of a steel ingot in which a coolant is blown into the sand mold from the lower part of the mold immediately after completion of casting.

Japanese Patent Application Laid-Open No. 55-68155 discloses an ingot manufacturing apparatus for ordinary ingot casting, ordinary ingot casting, and continuous casting. A heat sink formed at the bottom of the mold, a funnel nozzle provided at the molten metal injection section in the mold to collect molten metal and reduce the impact caused by the injection of molten metal, By reducing the horizontal temperature gradient of the metal in the mold by an internal temperature control means comprising one or two or more of an air supply pipe for injecting the active gas and a cooler provided at an axial end in the mold, Alternatively, there is described an ingot manufacturing apparatus in which a vertical temperature gradient is increased so that a ratio of a vertical temperature gradient to a horizontal temperature gradient is increased.

Japanese Patent Application Laid-Open No. 55-153663 discloses that a water pipe is inserted through a water pipe above a vertical hole formed in a mold, and a pressure gauge and a pressure control valve are provided at appropriate positions of the water pipe. A mold cooling device is described.

Japanese Unexamined Patent Publication (Kokai) No. 62-227550 discloses that the ratio of the height (H) to the average diameter (D) of the mold is one.
In the method for producing a steel ingot of ~ 4, the platen and the lower end of the mold (H / 2 or less to H / 4 or more) are cooled, the upper part of the mold is insulated using an insulating board, and the solidification rate without the accelerated solidification zone A method for producing a steel ingot to be solidified by is described.

[0007] Japanese Patent Application Laid-Open No. 63-2535 discloses that a molten metal is cast into an ingot mold frame comprising a surface plate, a mold and a feeder frame.
In the method for producing a forged steel ingot product obtained by solidifying the molten metal, the platen is cooled during production of the steel ingot, and 1 / 4H of the mold height (H) from the lower end of the mold.
A method for manufacturing a steel ingot for forging, which cools down to １ ／ H, and insulates from the upper end of the mold to 1 / 10H to ５H of the mold height (H).

[0008]

Normally, when a molten alkali metal is naturally cooled in a molding machine and solidified, as shown in FIG. 1, shrinkage holes or shrinkage cavities whose center is depressed are formed. Therefore, when commercialized, these dents must be cut, and the yield is reduced. In addition, the molten alkali metal has a large heat capacity, and a special cooling facility is required to reduce the degree of shrinkage holes or shrinkage cavities, to increase the cooling rate in a supercooled state and to cool and solidify the molten alkali metal. .

It is an object of the present invention to provide a method in which a molten alkali metal cast in a molding machine is cooled down by circulating a cooling medium through a cooling jacket, and the molten alkali metal is solidified into a hollow state when solidified. It is an object of the present invention to provide a method for producing a cast alkali metal ingot such as a cast lithium ingot having a very small degree of shrinkage holes and shrinkage cavities.

[0010]

Means for Solving the Problems The present inventors prototyped a large number of molding devices of different types and a cooling jacket corresponding to the molding devices, and used a room temperature refrigerant to produce cast lithium without shrinkage holes or shrinkage cavities. We had been studying a simple and practical method for manufacturing ingots.In the course of this research, when cooling from a few cm below the top surface of the cast metal lithium, a shrinkage hole was formed in the center of the solidified lithium ingot. And the occurrence of shrinkage nests is reduced,
The present inventors have made intensive studies on the relationship between the height of the cast metal lithium and the effective height of the cooling jacket and the shape of the molding device, and have completed the present invention.

That is, according to the present invention, a molten alkali metal such as molten metal lithium is cast into a molding machine having a truncated cone shape or the like having a cooling jacket, and a cooling medium such as 1
In a method for producing an alkali metal ingot in which an oil at 5 to 40 ° C. is circulated to cool a molten alkali metal in a molding machine, the height of the molten alkali metal cast is H (mm), H
When the inner diameter of the molding device at a height of / 2 is d (mm) and the effective height of the cooling jacket is h (mm), the following expression is obtained: Y = (H−h) · d / h · (mm) The present invention relates to a method for producing a cast alkali metal ingot, characterized by cooling a molten alkali metal in a molding machine under a condition where a Y value is 3 to 25, preferably 8 to 15.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing a cast alkali metal ingot according to the present invention comprises casting a molten alkali metal into a molding machine provided with a cooling jacket, circulating a refrigerant through the cooling jacket, and melting molten alkali in a columnar molding machine. It is characterized in that metal is cooled under specific cooling conditions to prevent shrinkage holes and shrinkage cavities from occurring. FIG. 2 shows a state in which molten alkali metal is solidified in a molding machine by the method for producing a cast alkali metal ingot of the present invention. In FIG. 2, 1 is a molding device,
2 is a molding machine main body, 3 is a molding machine main body upper flange, 4 is a molding machine main body lower flange, 5 is a surface plate, 6 is a flange portion of a casting device, 7 is a cooling jacket, 8 is a refrigerant inlet, 9 is a refrigerant outlet, 10 is a solidified cast alkali metal ingot,
11 represents a contraction hole.

In the present invention, the term "alkali metal" means a metal belonging to Group 1 of the periodic table, such as lithium Li, sodium Na, potassium K, and the like. The term "cast alkali metal ingot" means that a molten alkali metal is injected into a columnar molding machine. Columnar ingot obtained by solidification. In the method for producing a cast alkali metal ingot of the present invention, particularly preferable results are obtained when the method is applied to lithium metal having the highest melting point among alkali metals.

The molding machine in the present invention may be any molding machine capable of forming a mold into which a molten alkali metal is injected. For example, the molding machine includes a molding machine main body and a surface plate. Things can be mentioned. Usually, a flange portion for screwing with a platen and a flange portion of a casting device is provided at an upper portion and a lower portion of the molding device main body. Also, as the shape of the molding device body, truncated cone shape, truncated pyramid shape with rounded corners, columnar shape, prismatic shape with rounded corners, etc. can be exemplified.
A frustoconical shape is preferred from the viewpoint of releasing the solidified ingot from the molding machine smoothly. In addition, examples of the material of the molding device include iron, stainless steel, and copper.
A mold having a thickness of about 1 to 10 mm is usually used.

The casting of the molten alkali metal into the molding machine is performed by circulating a coolant through a cooling jacket, replacing the inside of the molding machine body with argon gas, and then melting the molten alkali metal in a measuring tank controlled at a predetermined temperature. Is carried out by pouring a predetermined amount of. In the case of an alkali metal other than lithium, it can be cast into a molding machine under a nitrogen gas atmosphere.
When the alkali metal is lithium, the molten lithium in the measuring tank is usually maintained at 200 to 270 ° C., and the casting speed when the total casting amount in the molding machine is, for example, 0.5 to 3.0 kg is usually 10 to 30 g / sec is preferred.

As the cooling jacket in the present invention,
Any type can be used as long as it can cool the side surface of the molding device into which the molten alkali metal is injected, from the surroundings.For example, a coolant inlet is provided at a lower portion, and a coolant outlet is provided at an upper portion. A cooling jacket capable of circulating a coolant in the jacket body can be given. Further, a structure can be provided in which the effective height of the cooling jacket can be changed as appropriate, such as a structure in which a plurality of refrigerant outlets having different heights are provided in the upper portion and any one of them can be appropriately selected. Here, the effective height of the cooling jacket is
When the refrigerant is circulated through the cooling jacket, it refers to the highest position where the refrigerant comes into contact with the molding device, that is, the height up to a position where the refrigerant can be substantially cooled. Also, the molding device can be cooled from below the platen.

Examples of the refrigerant include oil, water, cooling gas and the like. However, the oil is used in view of safety when the molding machine is damaged by corrosion and comes into contact with an alkali metal such as lithium, and heat transfer. preferable. The lower the temperature of the refrigerant, the better. However, in the present invention, a refrigerant at normal temperature, for example, 15 to 40 ° C. can be used.

In the method for producing a cast alkali metal ingot according to the present invention, the molten alkali metal is cooled under specific cooling conditions. That is, the height of the cast molten alkali metal is H (mm), the inner diameter of the forming device at half the height of the cast molten alkali metal (H / 2) is d (mm), and the effective height of the cooling jacket. Is h (mm)
And Y = (H−h) · d / h · (mm)
By adjusting the amount of the molten alkali metal to be cast into the molding device and / or the effective height of the cooling jacket so that the Y value in the above becomes 3 to 25, preferably 8 to 15, and particularly preferably 9 to 13, It is characterized in that the molten alkali metal in the vessel is cooled. Here, the height H (mm) of the cast molten alkali metal is the height in the melt before solidification, not the height in the solidified and contracted solid. When the cooling is performed under the condition that the Y value is 3 to 25, preferably 8 to 15, and particularly preferably 9 to 13, the Y value is 3
The degree of occurrence of the shrinkage hole is reduced to about 1/20 to 1/2 as compared with the case of less than or more than 25, and the shrinkage hole can be stably reduced to about 10 mm or less.

For example, when a cylindrical molding device is used, the inner diameter d of the molding device at the height of H / 2 is equal to the upper or lower portion of the molding device regardless of the height H of the molten alkali metal cast. When using a frusto-conical molding device, the inner diameter d of the molding device at a height of H / 2 is a (mm) where the upper diameter of the frusto-conical molding device is
The lower diameter is b (mm) and the height of the molding machine body is L (mm)
Is given by the following equation. d = b-{(ba). (H / 2) / L}

[0020]

The present invention will be described in more detail with reference to the following examples, but the technical scope of the present invention is not limited to these examples. (Manufacture of Cast Lithium Ingot) The dimensions and materials are shown in Table 1, and the outline shape and specification are shown in FIG. 3, respectively. 1.0kg type and 2.5k
g type). First, after cleaning and drying the molding machine main body and the surface plate, a Viton O-ring was placed in a circular groove provided on the surface plate, and combined with the molding machine body and fixed with bolts. This was fixed and sealed with bolts together with the flange portion of the lithium casting apparatus, and a cooling oil pipe was connected to the cooling jacket of the molding machine to circulate the refrigerant. Next, the inside of the molding machine main body was replaced with argon gas, a predetermined amount of molten lithium was transferred from the storage tank of the lithium casting apparatus to the measuring tank, and the temperature was set at 2 ° C.
The temperature was controlled at 10 to 260 ° C. Then, argon gas was pressurized in the measuring tank, and molten lithium was cast into the molding device at a casting speed of 10 to 30 g / sec. Room temperature oil was used as the refrigerant.

[0021]

[Table 1]

(Experimental Example 1) In a 0.7 kg type molding machine, the height H (mm) of the molten lithium cast was:
The height of the cooling jacket is 20 mm, 50 mm and 80 mm higher than the effective height h = 350 (mm), respectively.
0.65 kg, 0.7 kg and 0.8 kg of molten lithium were cast, respectively. The depth of the shrinkage hole is (Hh),
20 to 30 mm, 50 m when 20 mm (Y = 3.8)
m (Y = 9.4), 0 to 10 mm, 80 mm (Y =
15.0) was 15 to 25 mm.

(Experimental Example 2) In a 1.0 kg type molding machine, the height H (mm) of the molten lithium cast was
0.9 kg, 1.0 kg and 1. kg of molten lithium are respectively set so that the effective height h of the cooling jacket is 0 mm, 25 mm and 50 mm respectively from the effective height h = 210 (mm).
1 kg was cast. The depth of the shrinkage hole is (Hh) is 0 m
m (Y = 0.0), 50 to 80 mm, 25 mm (Y
= 12.3) 0 to 15 mm, 50 mm (Y = 2
In the case of 4.4), it was 20 to 30 mm.

(Comparative Example 1) As shown in FIG. 4, the effective height h was 325 (m).
m) was performed in the same manner as in Experimental Example 2 except that 1.0 kg of molten lithium was cast using the cooling jacket. That is, the casting was performed such that the height H (mm) of the molten lithium was 235 mm. In this case, the Y value was a negative value, and the depth of the shrinkage hole was 50 to 70 mm.

(Comparative Example 2) As shown in FIG. 1, the same procedure as in Experimental Example 2 was carried out except that the cooling jacket was removed from the above-mentioned 1 kg-type molding machine, allowed to cool naturally, and 1.0 kg of molten lithium was cast. went. That is, the casting was performed such that the height H (mm) of the molten lithium was 235 mm.
In this case, the Y value becomes an impossible value, and the depth of the shrinkage hole is 60.
８０80 mm.

(Experimental Example 4) In a 2.5 kg type molding machine, the height H (mm) of the molten lithium cast was
The effective height h of the cooling jacket is 10 mm, 30 mm and 50 mm higher than the effective height h = 395 (mm), respectively.
2.4 kg, 2.5 kg and 2.6 kg of molten lithium were cast, respectively. The depth of the shrinkage hole is (Hh),
40-60 mm, 30 m when 10 mm (Y = 3.1)
m (Y = 9.2), 10 to 25 mm, 50 mm (Y
= 15.3), it was 20 to 40 mm.

[0027]

According to the present invention, the molten alkali metal cast in the molding machine is solidified as shown in FIG. 4 by using a simple method of circulating a cooling medium through a cooling jacket and cooling it. It is possible to obtain a cast alkali metal ingot such as a cast lithium ingot in which the degree of shrinkage holes and shrinkage cavities where the center is sometimes dented is extremely small.

[Brief description of the drawings]

FIG. 1 is a view showing a state in which a molten alkali metal is allowed to cool naturally and solidify in a molding machine.

FIG. 2 is a diagram showing a state where molten alkali metal is solidified in a molding machine by the method for producing a cast alkali metal ingot of the present invention.

FIG. 3 is a diagram showing shapes and specifications of a molding device and a cooling jacket used for manufacturing the ingot of the present invention.

FIG. 4 is a diagram showing a state in which molten alkali metal is solidified in a molding machine using the cooling jacket described in Comparative Example 1.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Molder 2 Molder body 3 Molder body upper flange 4 Molder body lower flange 5 Surface plate 6 Flange part of casting device 7 Cooling jacket 8 Refrigerant inlet 9 Refrigerant outlet 10 Cast alkali metal ingot 11 Shrinkage hole

Claims (5)

[Claims] 1. A method of manufacturing an alkali metal ingot for casting a molten alkali metal into a molding machine having a cooling jacket, circulating a refrigerant through the cooling jacket, and cooling the molten alkali metal in the molding machine. The height of the metal is H (mm), the inner diameter of the molding machine at the height of H / 2 is d (mm), and the effective height of the cooling jacket is h.
(Mm), cooling the molten alkali metal in the molding machine under the condition that the Y value in the formula: Y = (H−h) · d / h · (mm) is 3 to 25. A method for producing a cast alkali metal ingot, which is characterized by the following. 2. The method for producing a cast alkali metal ingot according to claim 1, wherein the Y value is 8 to 15. 3. The method for producing a cast alkali metal ingot according to claim 1, wherein the molding device has a truncated cone shape. 4. The method for producing a cast alkali metal ingot according to claim 1, wherein the refrigerant is oil at 15 to 40 ° C. 5. The method for producing a cast alkali metal ingot according to claim 1, wherein the alkali metal is lithium.