JP2001181884A - Titanium manufacturing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a more inexpensive titanium manufacturing device by which the elution of the impurities resulting from the material consituting an electrolytic vessel is prevented, and the quality of the formed high-purity titanium is not adversely affected. SOLUTION: An electrode is put in an electrolytic bath held in the electrolytic vessel, raw titanium is introduced to surround the electrode, a voltage is applied with the electrode as a cathode and the raw titanium as an anode, and the raw titanium is refine in this titanium manufacturing device. The vessel is formed of clad steel with the side in contact with the bath being a nickel material of 99.0-99.8% nickel purity or titanium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for producing titanium for obtaining high-purity titanium by preventing contamination of a metal constituting a molten salt electrolytic vessel.

[0002]

2. Description of the Related Art In recent years, the use of high-purity titanium as a material for semiconductor manufacturing has become popular. A typical example is a titanium target used for forming a film barrier material between layers in a semiconductor device by sputtering. There is. Titanium for semiconductors such as this titanium target is used to improve reliability, such as alkali metals such as sodium, potassium and lithium, radioactive metals such as uranium and thorium,
It is necessary to minimize impurities such as heavy metals such as iron, chromium and nickel and oxygen. By the way, recent 64M
The titanium target required for DRAM is 99.99.
A high purity product of 5% [= 4N5 (Four Nine Five), excluding gas components] or more is required.

[0003] As a method for producing high purity titanium as described above, a molten salt electrorefining method is known. In this molten salt electrorefining method, a raw material titanium is put in a peripheral portion of an electrolytic vessel containing an electrolytic bath and a titanium rod electrode is put in a central portion, and a voltage is applied using the titanium rod electrode as a cathode and the raw material titanium as an anode. Then, purified titanium is deposited and generated on a titanium rod electrode. According to the law, iron, chromium,
Impurities such as heavy metals such as nickel and oxygen can be significantly reduced, which is useful as a method for producing high-purity titanium.

Attempts have been made to produce titanium with higher purity by using this molten salt electrorefining method. One of the causes of the contamination of titanium by the same method is that the material constituting the electrolytic vessel itself is an impurity. As a result, it is eluted into the electrolytic bath, the impurities are deposited on the titanium rod electrode as the cathode, and the obtained titanium is contaminated by the impurities. For example, in the literature, "USBereau of Mines, Report of
Investigation 5351,44 (1957) "states that when the electrolytic vessel is made of mild steel, the iron content in the generated titanium is 10%.
It is described that it becomes higher as it exceeds 0 ppm. To solve this situation, Japanese Patent Application Laid-Open No. 3-177594 has been proposed.
In the publication, other members and parts that come into contact with the molten salt, such as a crucible, a titanium sponge basket, and an anode pipe, are all made of high-purity nickel of 99.9% (3N) or more to form impurities in the electrolytic bath. A technique has been disclosed for reducing the elution of e.g.

[0005]

However, the above 9
It is difficult to industrially obtain a high-purity nickel material of 9.9% (3N) or more, and its use increases the production cost of the electrolytic container. Also, for example, in an electrolytic container in which a carbon steel container body is plated with high-purity nickel, during electrolytic refining, the plating is peeled off by heat and a part of the container body is eluted into the electrolytic bath, which adversely affects the quality of the generated titanium. Exert. Therefore, it has been desired to develop a more inexpensive titanium manufacturing apparatus that prevents elution of impurities resulting from the material constituting the electrolytic vessel into the electrolytic bath and does not adversely affect the quality of the produced titanium.

[0006] Accordingly, an object of the present invention is to provide an inexpensive titanium production method that prevents impurities derived from the material constituting the electrolytic vessel from being eluted into the electrolytic bath and does not adversely affect the quality of the high purity titanium produced. It is to provide a device.

[0007]

Under such circumstances, the present inventors have conducted intensive studies and as a result, have found that the molten salt electrolysis apparatus has a nickel purity of 9% on the side where the electrolysis vessel is in contact with the electrolysis bath.
If the clad steel is composed of 9.0% to 99.8% of a nickel material or a titanium material, the nickel material or the titanium material is not peeled or damaged even after a long operation, and the nickel material is used. The present inventors have found that even if the nickel purity is an industrial purity, it does not adversely affect the quality of the produced titanium at all, and thus an industrially inexpensive titanium manufacturing apparatus can be obtained, and the present invention has been completed.

That is, in the present invention (1), an electrode is placed in an electrolytic bath housed in an electrolytic vessel, and a raw material titanium is placed so as to surround the electrode, and a voltage is applied using the electrode as a cathode and the raw material titanium as an anode. In the titanium manufacturing apparatus for refining titanium raw material, the electrolytic vessel is formed of clad steel having a nickel purity of 99.0% to 99.8% of nickel material or titanium material on the side in contact with the electrolytic bath. An object of the present invention is to provide an apparatus for producing titanium.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The electrolytic vessel used in the present invention has a nickel purity of 99.0% to 99.8% on the side in contact with an electrolytic bath.
Is not particularly limited as long as it is made of a clad steel that is a nickel material or a titanium material, and can be heated by a general heating furnace. A cover made of a lid that tightly adheres to the inside is used. In the case of an electrolytic vessel having a bottomed cylindrical shape and a flange at the top, the above-mentioned clad steel may be used at least for an electrolytic vessel main body containing an electrolytic bath.

[0010] Cladded steel is a laminated composite material formed by forming a metallurgical bond between the surfaces of two or more metallic materials, and specifically, nickel-stainless steel, titanium-stainless steel. , Nickel-carbon steel-stainless steel, titanium-carbon steel-stainless steel, nickel-titanium-stainless steel, titanium-nickel-stainless steel, nickel-titanium-carbon steel-stainless steel, titanium-nickel-carbon steel-stainless steel Among them, nickel-carbon steel-stainless steel, nickel-titanium-stainless steel, and nickel-titanium-carbon steel-stainless steel are preferable in that they have corrosion resistance to the molten salt.
In the notation of the above specific example, the material described on the left end is on the side in contact with the electrolytic bath, and the outer members are in order from right to left. The manufacturing method of the clad steel is not particularly limited, and generally used manufacturing methods such as an assembling rolling method, a casting rolling method, an explosion bonding method, a build-up welding method, a diffusion welding method, and a method using cold welding are used. No.

As the nickel material used in the clad steel, industrial nickel having a nickel purity of 99.0% to 99.8% can be used. The nickel purity may be appropriately selected within the above range depending on the purity of the target titanium. For example, in order to obtain high-purity titanium with a purity of 99.999% (5N) or more, nickel purity of 99.3% or more, Preferably 9
What is necessary is just to use what is 9.5%-99.8%. By setting the nickel purity of the nickel material within the above range, the high purity titanium of 5N or more can be produced over a long period of time using less expensive nickel which is industrially available without using the conventional high purity nickel material of 3N or more. It can be manufactured stably. Further, the titanium material used in the clad steel is appropriately determined depending on the purity of the generated titanium. For example, when obtaining high-purity titanium having a titanium purity of 5N or more, a titanium purity of 5N
It is desirable to use N or more titanium materials. Also, commercially available stainless steel such as SUS304 and 316 can be used, and carbon steel such as SS400 can be used.

The thickness of the nickel material used in the clad steel is not particularly limited, but when it is made of two metal materials, it is preferably in the range of 5 to 10 mm, and it is made of three or more metal materials. When the nickel material is on the inner side of the container, the thickness is preferably in the range of 3 to 8 mm, which is made of three or more metal materials. When the nickel material is used as the intermediate layer, the thickness is preferably in the range of 2 to 5 mm.
If the thickness of the nickel material is too small, the nickel layer may peel off or disappear due to thermal deformation and corrosion during long-term operation. If the thickness is too large, the effect is saturated, which is economically disadvantageous. Further, the thickness of the titanium material used in the clad steel is not particularly limited, but when it is made of two metal materials, it is preferable that the thickness be in the range of 10 to 15 mm.
When the titanium material is made of three or more metal materials and the titanium material is on the inner side of the container, the range is 5 to 10 mm. It is preferable that the thickness be in the range of 5 to 5 mm. If the thickness of the titanium material is too small, the titanium layer may peel off or disappear due to thermal deformation, corrosion, or the like during long-term operation, which is undesirable, as in the case of the nickel material. If the thickness is too large, the effect is saturated, which is economically disadvantageous.

In the molten salt electrorefining method using the apparatus of the present invention, it is possible to produce high-purity titanium of 99.999% (5N) or more. High-purity titanium of 5N or more has a content of metal components such as iron, chromium, nickel, copper, and aluminum of 5 ppm or less, preferably 1 ppm or less, more preferably 0.5 ppm or less, respectively. ) Is less than 200 ppm, preferably 100 ppm
ppm or less, more preferably 50 ppm or less.

The electrolytic bath to be charged into the electrolytic vessel of the present invention includes NaCl, NaCl-KCl, LiCl-KC
l, chloride used in NaCl-K typically molten salt electrolysis method for purifying titanium such as ₂ TiF ₆ or a mixture of chlorides and fluorides are used. Although the purity of these compounds is not particularly limited, any of commercially available high-grade, special-grade reagent levels, primary reagent levels to which impurities have been removed to some extent, and industrial chemical levels having a low degree of purification can be used. At the reagent level,
The contents of metal components such as iron, chromium, nickel, copper, and aluminum are each 1 to 5 ppm, magnesium and calcium are each 1 to 20 ppm, and the water content is 20 to 100.
ppm. First-class reagents and industrial reagents naturally have an impurity content higher than that of the above-mentioned special-grade reagents, but they can be used as they are, or they can be used after being subjected to purification treatment such as heat dehydration treatment in advance. .

The raw material titanium used in the present invention is generally sponge titanium, but briquette-like titanium can also be used. When the purpose is to obtain high-purity titanium as in the present invention, it is preferable to select a raw material titanium having a low impurity concentration. The raw material titanium is accommodated in a ring-shaped basket container so as to surround the electrode, and the entire ring-shaped cage container is immersed in an electrolytic bath in the electrolytic container.
The ring-shaped basket container is supported by the lid of the electrolytic container in a non-contact manner, and is connected to an anode of a power supply. In addition, iron or nickel is used for the material of the ring-shaped basket container. However, in order to obtain high-purity titanium having a purity of 5N or more, nickel having a purity of 99.0% or more, preferably 99.5% or more is preferable.

The electrode is not particularly limited as long as it can clear a physical surface such as temperature and strength and a chemical surface such as corrosiveness, but a titanium rod is preferable. Also, assuming a case of accident such as peeling of nickel or titanium material, as a countermeasure that the material itself (impurities) constituting the core material of the electrolytic container elutes into the electrolytic bath, during the electrolysis, the raw titanium is used as an anode, A method may be adopted in which the container is used as a cathode and a voltage lower than the titanium generation voltage is separately applied between them, thereby preventing elution of impurities from the electrolytic container and preventing precipitation of titanium into the electrolytic container. be able to. This applied voltage is usually 500 mV or less, preferably 10 to 150 mV.
V, more preferably 30 to 100 mV.

Next, a method for producing titanium will be described with reference to the drawings. FIG. 1 is a schematic view showing an example of the titanium production apparatus of the present invention. In FIG. 1, a titanium manufacturing apparatus 1 is set in a heating furnace (not shown), and a side in contact with an electrolytic bath is, for example, nickel-stainless steel (SU) having a nickel purity of 99.3%.
In step S304), the electrode 5 is inserted into the electrolytic bath 2 housed in the electrolytic container 3 having the container body 11 made of clad steel, and the raw material titanium 4 is put so as to surround the electrode 5, and the electrode 5 is used as a cathode. A voltage is applied using the raw material titanium 4 as an anode, and the raw material titanium 4 is purified to obtain high purity titanium of 5N or more.

The electrolytic vessel 3 is a vessel body 11 made of clad steel having a bottomed cylindrical body and a flange 10 at the upper end edge.
And a lid 12 which is in close contact with the flange portion 10 and seals the inside of the container body 11. A supply pipe 13 made of stainless steel is attached to a lower portion of the container body 11.
Is a pipe for supplying and discharging the molten salt into the container body 11. And the raw material titanium 4 surrounding the electrode 5
It is put into a nickel-made ring-shaped basket container 14 and is housed in the peripheral portion 3 a in the electrolytic container 3 together with the ring-shaped basket container 14. In FIG. 1, reference numeral 14a indicates a mesh of the basket container.

The electrode 5 inserted in the center of the raw material titanium 4 surrounding the electrode 5, that is, almost in the center 3 b of the electrolytic vessel 3.
Is made of titanium. The electrode 5 has its upper shaft portion 24 penetrating through the lid 12 and is vertically movably supported on the upper portion of the electrolytic container 3. The electrode 5 is moved downward during electrolysis to move the lower shaft portion 25 of the electrolytic container 3. It can be put in the electrolytic bath 2 located at the central portion 3b, and after the electrolysis is completed, it can be moved upward and separated.

Then, the ring-shaped cage container 14 into which the raw material titanium 4 is charged and the electrode 5 are connected to a power source 26 by the following electrolysis circuit. That is, the anode of the power supply 26 is electrically connected to the terminal 14 a of the ring-shaped basket container 14, and the cathode is electrically connected to the electrode 5 via the changeover switch 27. Further, a power supply 28 is provided as an impurity elution prevention circuit.
Is connected to the terminal 14 of the basket 14 via the switch 29.
b, and the cathode is the container body 1 of the electrolytic container 3.
1 electrically.

Next, based on this titanium manufacturing apparatus 1,
A method for producing titanium will be described. First, NaCl- previously mixed at a molar ratio of 1: 1 in the container body 11 of the electrolytic container 3 was used.
The mixed chloride of KCl is introduced through the supply pipe 13. Next, the mixed chloride in the container body 11 was heated to 650 ° C. under reduced pressure and dehydrated well. After the inside of the vacuum heating furnace was replaced with an argon atmosphere, the temperature was raised to 740 ° C. to melt the mixed chloride. This is referred to as electrolytic bath 2. The switch 29 of the impurity elution prevention circuit is turned on, a voltage is applied from the power supply 28 by a direct current, and then the raw material titanium 4 is charged into the ring-shaped basket container 14, and the electrolytic container 3 is covered with the lid 4. Subsequently, liquid TiCl ₄ is appropriately blown into a bottom portion of the electrolytic vessel 3 from a supply pipe (not shown) to generate titanium ions in the electrolytic bath 2.
The power supply 28 of the electrolysis circuit is turned off by the changeover switch 29, and then the electrode 5 is inserted into the electrolytic bath 2 in the central portion 3 b of the electrolysis container 3, and the changeover switch 27 is turned on to turn on the power
To apply a voltage to a circuit for electrolysis with a direct current to perform electrolysis. At this time, the raw material titanium 4 is added as needed. After performing the electrolysis for a predetermined time, the power supply 26 of the electrolysis circuit is turned off by the changeover switch 27, the electrode 5 is pulled up to the upper part of the electrolysis container 3, and cooled to room temperature under an argon atmosphere. Next, the electrode 5 is taken out of the vacuum heating furnace, and the entire titanium formed on the electrode 5 is quickly washed with a dilute acid solution, further washed with pure water, and once dried under vacuum to remove moisture. Vacuum drying to obtain high purity titanium. During the electrolysis, impurities from the electrolytic vessel 3 are prevented by providing the electrolytic vessel with, for example, clad steel having a nickel material on the electrolytic bath side and providing an impurity elution prevention circuit as described above. Can be obtained. Note that the impurity elution prevention circuit is an optional installation circuit, and the impurity elution prevention circuit does not have to be particularly installed.

[0022]

Next, the present invention will be described in more detail with reference to examples, but this is merely an example and does not limit the present invention. Example 1 NaCl-K mixed in a molar ratio of 1: 1 into an electrolytic vessel made of clad steel in which nickel was lined (nickel thickness: 7 mm) inside mild steel (SS400) having an inner volume of 70 l.
Cl mixed chloride (Table 1 shows the percentage of impurities) 150
kg, and dehydrated and melted at 650 ° C to 740 ° C in an electric furnace to form an electrolytic bath. Shed. 5 kg of titanium sponge was immersed in this electrolytic bath while being placed in a ring-shaped basket made of nickel, and liquid TiCl ₄ was appropriately blown into the electrolytic bath to generate titanium ions in the electrolytic bath.

Next, after the titanium electrode is placed in the electrolytic bath and the voltage of the impurity elution preventing circuit is stabilized, a direct current is applied to the electrolytic circuit at a voltage of 800 mV to start electrolysis.
After a period of time, the power supply to the electrolysis circuit was stopped, and the titanium electrode was pulled up and cooled to room temperature. Thereafter, the titanium formed on the titanium electrode was washed with acid and pure water, and vacuum-dried to obtain titanium as a resin crystal. The obtained titanium was analyzed for impurity elements by a conventional method. Table 2 shows the results
Shown in In the table, the unit is ppm.

Example 2 An impurity elution prevention circuit was not used (OFF state), and the other steps were performed in the same manner as in Example 1. The results are shown in Table 2.

Comparative Example 1 Instead of the electrolytic vessel made of clad steel, mild steel (SS4
Example 2 was carried out in the same manner as in Example 2 except that an electrolytic container manufactured by the Company No. 00) was used. Table 2 shows the results.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

According to the present invention, it is possible to prevent the impurities caused by the material constituting the electrolytic vessel from being eluted into the electrolytic bath and to produce a titanium at a lower cost without adversely affecting the quality of the high purity titanium produced. An apparatus can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a titanium manufacturing apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Titanium manufacturing apparatus 2 Electrolysis bath 3 Electrolysis container 3a Peripheral part 3b Central part 4 Raw material titanium 5 Electrode 10 Flange part 11 Container main body 12 Lid 13 Supply pipe 14 Ring-shaped basket container 14a, 14b Terminal 24 Upper shaft part 25 Lower shaft part 26, 28 power supply 27 selector switch 29 switch

Claims (2)

[Claims] An electrode is placed in an electrolytic bath housed in an electrolytic vessel, and a raw material titanium is put so as to surround the electrode. A voltage is applied using the electrode as a cathode and the raw material titanium as an anode to purify the raw titanium. In the titanium manufacturing apparatus, the electrolysis container has a nickel purity of 99.0% on a side in contact with the electrolysis bath.
An apparatus for manufacturing titanium, comprising: clad steel that is a nickel material or a titanium material of up to 99.8%. 2. The clad steel comprises nickel-stainless steel, titanium-stainless steel, nickel-carbon steel-stainless steel, titanium-carbon steel-stainless steel, nickel-stainless steel.
2. The titanium production apparatus according to claim 1, wherein the apparatus is titanium-stainless steel, titanium-nickel-stainless steel, nickel-titanium-carbon steel-stainless steel, or titanium-nickel-carbon steel-stainless steel.