JP7264746B2 - Molten metal container, container, method for detecting leakage of molten metal, and method for producing titanium sponge. - Google Patents

Description

TECHNICAL FIELD The present invention relates to a molten metal container, a container, a method for detecting leakage of molten metal, and a method for producing titanium sponge.

Conventionally, metallic titanium has been produced in the form of sponge titanium by the Kroll method. In recent years, the titanium sponge is required to reduce the amount of impurity metals such as Ni and Cr due to the development of the electronic component business and the material business. In particular, there is a demand for reducing the amount of Ni in sponge titanium (for example, 10 ppm by mass or less).

However, some of the Ni mixed in the titanium sponge migrates from the inner wall of the metal reduction reaction vessel used in the reduction step to the titanium sponge generated inside the vessel. Further, for example, if the molten magnesium supplied to the metal reduction reaction vessel contains Ni, the Ni also transfers from the molten magnesium to the titanium sponge. It is difficult to remove Ni transferred to sponge titanium at low cost. Therefore, it is preferable not to contaminate the molten magnesium used in the reduction step with Ni in order to purify the titanium sponge. Therefore, it is desired that the molten magnesium used in the reduction process has a low Ni concentration.

For example, in Patent Document 1, low-nickel steel is disposed over the entire inner surface of a stainless steel container via a solid support, and the solid support intervenes between the inner surface of the stainless steel container and the low-nickel steel. There has been proposed a container for transporting and holding molten magnesium, which holds a gap between the stainless steel and the low-nickel steel to prevent nickel from diffusing from the stainless steel to the low-nickel steel.

JP 2004-340552 A

As in Patent Document 1, if clad steel is adopted as a container material for a container for transporting and holding molten magnesium, and low-nickel steel such as carbon steel is placed inside the container, molten magnesium and stainless steel do not come into contact with each other. Ni contamination can be suppressed. However, in order to keep the molten magnesium in the container for carrying and holding molten magnesium, the bottom side of the container for carrying and holding molten magnesium is generally heated and held from the outside with a heater or the like. As the number of times of use of the transporting and holding container increases, the bottom-side low-nickel steel of the molten magnesium transporting and holding container tends to wear out. However, it is difficult to confirm this with the naked eye. Since molten magnesium is easily oxidized, a container for storing molten magnesium usually has a closed structure, and the inside of the container cannot be observed in detail from the outside.

Even if the nickel concentration in the molten magnesium injected into the metal reduction reaction vessel is periodically analyzed, the time when the molten magnesium is found to be contaminated with impurity metals such as Ni in the analysis of the molten magnesium. It is thought that the wear of the container for transporting and holding molten magnesium has progressed considerably. From the standpoint of stably producing high-purity titanium sponge, there is still room for improvement in quickly grasping the state of the container.

Therefore, in one embodiment, an object of the present invention is to provide a molten metal storage container capable of quickly grasping the state of internal damage in order to stop the use of molten metal contaminated with Ni at an early stage. and

That is, in one aspect of the present invention, a bottomed carbon steel inner cylinder containing molten magnesium or molten magnesium chloride, a bottomed outer cylinder provided around the inner cylinder and provided with a top cover, a connecting portion disposed between the inner cylinder and the outer cylinder and connecting the entire circumference of the opening of the inner cylinder and the outer cylinder; and a space defined between the inner cylinder and the outer cylinder. and a sensing sensor connected to said space.

In one embodiment of the molten metal container according to the invention, the connection is made of carbon steel.

In one embodiment of the molten metal storage container according to the present invention, the detection sensor is a pressure detection sensor.

In one embodiment of the molten metal storage container according to the present invention, the detection sensor is an electrical resistance detection sensor.

In another aspect, the present invention is a container comprising any one of the molten metal containers and a heater.

In another aspect of the present invention, there is provided a molten metal leakage detection method including a detection step of detecting leakage of molten metal using any of the above-described molten metal containers.

Furthermore, in another aspect of the present invention, there is provided a method for producing titanium sponge, including a step of producing titanium sponge using any one of the molten metal containers described above.

According to one embodiment of the present invention, the state of internal damage can be quickly grasped in order to stop the use of Ni-contaminated molten metal early.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic sectional drawing which is shown typically in order to demonstrate the internal structure of one Embodiment of the molten metal storage container which concerns on this invention. FIG. 4 is a schematic cross-sectional view schematically showing the internal structure of another embodiment of the molten metal container according to the present invention. FIG. 4 is a schematic cross-sectional view schematically showing the internal structure of another embodiment of the molten metal container according to the present invention. 1 is a schematic cross-sectional view schematically showing the internal structure of an embodiment of a container according to the present invention; FIG. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flowchart for explaining an embodiment of a molten metal leak detection method according to the present invention; 2 is a schematic cross-sectional view schematically showing the internal structure of a molten metal container used in Comparative Example 1. FIG.

Specific embodiments of the present invention will be described in detail below. In addition, the present invention is not limited to the following embodiments, and various modifications are possible without changing the gist of the present invention. 1 to 4 may schematically represent the width, thickness, shape, etc. of each part compared to the actual embodiment, but this is an example and does not limit the interpretation of the present invention. Furthermore, in this specification, the term "upward" means the axial direction of the outer cylinder 20 from the bottom wall portion 22 of the outer cylinder 20 toward the upper lid 25 (see FIG. 1).

[1. overview]
The method for producing sponge titanium in the Kroll method consists of a reduction step in which titanium tetrachloride is added dropwise to molten magnesium charged under inert conditions into a metal reduction reaction vessel to form a sponge titanium mass, and a metal reduction reaction vessel. After extracting molten magnesium chloride, which is a by-product, and molten magnesium, if any, from the reaction vessel through a metal pipe, the titanium sponge lumps are subjected to a vacuum separation process, and the titanium sponge lumps are sorted. and a sorting/crushing step of crushing to obtain sponge titanium. In the electrolysis step, magnesium chloride is electrolyzed into magnesium and chlorine gas by molten salt electrolysis of the molten magnesium chloride by-produced in the reduction step. Molten magnesium produced in the electrolysis process is transported after being stored in a transport container (hereinafter referred to as "container") whose interior is maintained at a high temperature and with an inert gas from the electrolytic cell, and the transported molten magnesium is reduced. A predetermined amount is injected into the metal reduction reaction vessel waiting for the reaction.

Conventionally, from the viewpoint of not contaminating the molten magnesium with Ni, it is known to make the molten metal storage container made of clad steel with the inner side in contact with the molten magnesium made of carbon steel (Patent Document 1). Carbon steel can have a composition that does not substantially contain Ni, and stainless steel has excellent mechanical strength even at high temperatures. Therefore, carbon steel and stainless steel have been used in combination for the molten metal storage container in order to suppress Ni contamination and ensure the mechanical strength of the molten metal storage container during high-temperature heating. It should be noted that the carbon steel inside the molten metal storage container is reduced in thickness due to repeated use. Then, when the carbon steel is damaged, the contained molten magnesium comes into contact with the stainless steel containing Ni, Ni in the stainless steel migrates to the molten magnesium, and the molten magnesium is contaminated with Ni. In addition, the molten metal storage container adopts an airtight structure in order to suppress the formation of magnesium oxide.

Therefore, conventionally, the presence or absence of Ni contamination was confirmed by chemically analyzing the molten magnesium transferred in the molten metal storage container, instead of visually checking the structure inside the molten metal storage container. Since the determination takes too much time, a method for early detection of Ni contamination has been desired.

Therefore, as a result of intensive studies, the present inventors found that by dividing a space in the molten metal storage container and connecting a detection sensor for detecting molten magnesium to the space, the molten metal can be detected without disassembling the molten magnesium storage container. We have obtained knowledge that it is possible to detect damage inside the storage container at an early stage.
Each embodiment will be described below.

[2. Molten metal container]
According to the molten metal storage container 1A of the present invention, when the molten metal leaks from the bottomed inner cylinder 10 into the space 40, the detection sensor quickly detects the leakage of the molten metal. The container in which leakage of the molten metal to the space 40 is detected is stopped, and as a result, the use of the molten metal in which the metal components such as Ni contained in the bottomed outer cylinder 20 with the upper lid 25 are diffused is effectively stopped. can be avoided. As shown in FIG. 1, in one embodiment, a molten metal container 1A according to the present invention includes an inner cylinder 10, an outer cylinder 20, a connecting portion 30, a space 40, and a detection sensor that is a pressure detection sensor 50. , a metal pipe 55 , an inert gas supply pipe 70 , and a Mg pipe 80 . Note that the molten metal container 1A may contain molten magnesium and molten magnesium chloride, and the member denoted by reference numeral 80 shown in FIG. 1 is simply called the Mg pipe 80 for convenience. Further, in the present invention, molten magnesium chloride is treated as a molten metal to be accommodated. Each component will be described below.

(Inner cylinder)
The inner cylinder 10 has a function of containing the molten magnesium M. In addition, in the present invention, instead of the molten magnesium M, molten magnesium chloride can also be applied as described above.

The material of the inner cylinder 10 may be a steel material containing almost no Ni, such as carbon steel, from the viewpoint of preventing Ni, which is an impurity metal, from diffusing into the molten magnesium M. Carbon steel is steel having a carbon content of 2% by mass or less, and includes so-called ultra-low carbon steel, low carbon steel, medium carbon steel, high carbon steel, and the like. Specific examples of carbon steel include SS400. Molten magnesium M may be produced by molten salt electrolysis of molten magnesium chloride by-produced in the reduction step.

The inner cylinder 10 has a bottomed shape and includes an opening 11 , a bottom wall 12 , and side walls 13 connecting the opening 11 and the bottom wall 12 .

(Outer cylinder)
The outer cylinder 20 is provided around the inner cylinder 10 via a space 40 into which the molten magnesium M flows when the molten magnesium M leaks from the inner cylinder 10 . In other words, a space 40 is provided between the inner cylinder 10 and the outer cylinder 20, and the space 40 is a space communicating with the installation position of the detection sensor, which is the pressure detection sensor 50. As shown in FIG. The material of the outer cylinder 20 is preferably stainless steel or clad steel (laminated steel of carbon steel and stainless steel) from the viewpoint of ensuring wear resistance, chemical corrosion resistance, and strength at high temperatures. Here, stainless steel is steel to which chromium (Cr), nickel (Ni), or the like is added. Specific examples of stainless steel include ferritic stainless steel, austenitic stainless steel, martensitic stainless steel, and duplex stainless steel. Note that the explanation of carbon steel overlaps with that of the material of the inner cylinder 10, so it is omitted.

The outer cylinder 20 has a bottomed shape, and includes an opening 21 , a bottom wall 22 , and side walls 23 connecting the opening 21 and the bottom wall 22 . The opening 21 is closed by an upper lid 25 to prevent the molten magnesium M from coming into contact with the outside air and becoming magnesium oxide. Further, the outer cylinder 20 may have a shape substantially similar to that of the inner cylinder 10 from the viewpoint of securing a space 40, which will be described later. A portion of the wall 12 may be contacted. Also, a spacer (not shown) that mechanically supports the inner cylinder 10 may be installed so as to connect the inner cylinder 10 and the outer cylinder 20 . When the spacer is arranged, a space 40 communicating with the pressure detection sensor 50 is secured.

(connection part)
The connecting portion 30 is arranged between the inner cylinder 10 and the outer cylinder 20 and connects the entire circumference of the opening 11 of the inner cylinder 10 and the outer cylinder 20 . At this time, since the connection portion 30 is provided over the entire circumference of the opening portion 11 of the inner cylinder 10 , a space 40 is formed between the inner cylinder 10 and the outer cylinder 20 . By providing the connecting portion 30 over the entire circumference of the opening 11, the space 40 is set so as to cover the outer side of the inner cylinder 10, so leakage of the molten magnesium M can be detected over a wider range. In the molten metal storage container 1A shown in FIG. As another form, the connecting portion 30 may be provided so as to connect the opening 11 of the inner cylinder 10 and the opening 21 of the outer cylinder 20 along the entire circumference. In this case, the connecting portion 30 may be in contact with the lower end of the upper lid 25 . As means for forming the connecting portion 30, for example, a member may be arranged between the inner cylinder 10 and the outer cylinder 20 and welded to form the connecting portion 30. FIG. The material of the connecting portion 30 is preferably carbon steel from the viewpoint of not diffusing impurity metals such as Ni into the molten magnesium M even when the connecting portion 30 comes into contact with the molten magnesium M contained in the inner cylinder 10 . Alternatively, the entire periphery of the opening 11 of the inner cylinder 10 and a suitable portion of the outer cylinder 20 may be welded together, and the welded portion having a reduced Ni or Cr content may be used as the connecting portion 30 . Note that the explanation of carbon steel overlaps with that of the material of the inner cylinder 10, so it is omitted.

(space)
A space 40 is partitioned between the inner cylinder 10 and the outer cylinder 20 while maintaining airtightness. For example, the space 40 is configured so that the molten magnesium M leaked from the inner cylinder 10 can flow. Here, on the premise that the connecting portion 30 is formed around the entire circumference of the opening 11 of the inner cylinder 10 and that the space 40 communicates with the detection sensor, at least one portion between the inner cylinder 10 and the outer cylinder 20 is connected. The space 40 may be formed at the part, or the space 40 may be formed over the entire area between the inner cylinder 10 and the outer cylinder 20 . Moreover, in the space 40, a desired separation distance can be secured between the inner cylinder 10 and the outer cylinder 20 by interposing a spacer (not shown).

(detection sensor)
The detection sensor has a function of detecting leakage of molten magnesium M from the inner cylinder 10 . A detection sensor is connected to the space 40 . Here, the detection sensor is preferably either the pressure detection sensor 50 or the electric resistance detection sensor 60 (see FIG. 3). The pressure detection sensor 50 and a monitor (not shown) that displays the detection results are connected via a cable 51 . The pressure detection sensor 50 may be arranged outside the space 40 or inside the space 40 . For example, the through hole 41 shown in FIG. 1 connects the space 40 and the inside of the metal pipe 55 . Therefore, if the metal pipe 55 and the pressure detection sensor 50 are connected, the pressure detection sensor 50 can detect pressure changes when the molten magnesium M leaks into the space 40 . Even in such an embodiment, it is determined that the space 40 is communicated with the pressure detection sensor 50 . A pressure detection sensor 50 is installed in the space 40 in the molten metal container 1B shown in FIG.

(metal pipe)
The interior of the metal pipe 55 may be a space connecting the pressure detection sensor 50 and the space 40 , or may accommodate the cable 51 attached to the pressure detection sensor 50 . The material of the metal pipe 55 is preferably stainless steel or clad steel from the viewpoint of ensuring wear resistance, chemical corrosion resistance, and strength at high temperatures. The metal pipe 55 communicates with the through hole 41 of the outer cylinder 20 provided near the connecting portion 30 . The metal pipe 55 extends upward in the vertical direction V along the side wall portion 23 of the outer cylinder 20, but the arrangement of the metal pipe 55 can be changed as appropriate.

(pressure detection sensor)
The pressure detection sensor 50 has a function of detecting pressure fluctuations in the space 40 due to leakage of the molten magnesium M from the inner cylinder 10 into the space 40 . Normally, molten magnesium M is maintained at a high temperature of about 700°C. Since the heater 120 of the container 100 (FIG. 4) is generally installed on the bottom side of the molten metal container 1A, the pressure detection sensor 50 is placed above the space 40 from the viewpoint of reducing the influence of heat. and is preferably arranged near the connecting portion 30 or inside the metal pipe 55 .

(electric resistance detection sensor)
As shown in FIG. 3, in the molten metal storage container 1C, the through hole 42 on the bottom side of the space 40 and the metal pipe 65 are connected, the electric resistance detection sensor 60 is arranged on the bottom side of the space 40, and the cable 61 is connected. It is housed inside a metal pipe 65 . The electrical resistance detection sensor 60 has a function of detecting a sudden drop in resistance when the molten magnesium M leaking from the inner cylinder 10 into the space 40 comes into contact with the electrical resistance detection sensor 60 . Since the leaked molten magnesium M flows to the bottom side of the space 40 , the electrical resistance detection sensor 60 is preferably arranged on the bottom side of the space 40 . Note that if the heater 120 (see FIG. 4) is installed near the bottom of the space 40, the electrical resistance detection sensor 60 may be placed on a side other than the bottom of the space 40 in consideration of thermal damage. .

The inert gas supply pipe 70 feeds the molten metal containers 1A, 1B, and 1C with an inert gas such as argon gas or helium gas so that the molten magnesium M contained in the inner cylinder 10 does not become magnesium oxide due to the influence of oxygen. It has the function of filling with The inert gas supply pipe 70 is provided on the upper lid 25 .

The Mg pipe 80 has a function of feeding the molten magnesium M to the molten metal containers 1A, 1B, and 1C. A liquid feed port 81 of the Mg pipe 80 is arranged on the bottom side of the inner cylinder 10 .

[3. container]
As shown in FIG. 4, one embodiment of the container 100 according to the present invention includes the above-described molten metal container 1A, the furnace 110 that maintains the temperature in the molten metal container, and the molten metal container that heats the inside of the molten metal container. and a ring-shaped support member 130 for supporting the molten metal container 1A. Besides the molten metal container 1A, the molten metal container 1B and the molten metal container 1C can also be used. According to one embodiment of the container 100 according to the present invention, the state of the container 100 can be grasped in order to stably produce high-purity titanium sponge. The separation distance d between the heater 120 and the bottom wall portion 22 of the molten metal container 1A in the vertical direction V is, for example, a few It may be about 100 millimeters. A base end portion 131 of the support member 130 is joined to the upper lid 25 , and a tip end portion 132 of the support member 130 is in contact with and supported by the upper end surface 111 of the furnace 110 . A hole (not shown) is formed in the support member 130, and the metal pipe 55 is inserted through the hole. In addition, in one embodiment of the container 100 according to the present invention, the support member 130 is not limited to a ring shape as long as it can support the molten metal container 1A. .

[4. Molten metal leak detection method]
In one embodiment of the molten metal leakage detection method according to the present invention, as shown in FIG. including. According to one embodiment of the method for detecting leakage of molten metal according to the present invention, even if molten magnesium M leaks from the inner cylinder 10, the detection sensors 50 and 60 quickly detect it and the molten metal storage containers 1A, 1B and 1C are detected. damage can be known. Each step will be described below. In addition, the description which overlaps with the molten metal container 1A, 1B, 1C mentioned above is omitted.

(Detection process)
In the detection step S11, leakage of molten magnesium M is detected by a detection sensor. When molten magnesium M leaks into space 40, the pressure in space 40 increases. The pressure detection sensor 50 can detect this pressure variation. When the molten magnesium M leaks into the space 40 , the molten magnesium M flows toward the bottom wall portion 22 of the outer cylinder 20 . When the molten magnesium M contacts the electric resistance detection sensor 60 provided on the bottom wall portion 22, the resistance changes. As described above, the pressure detection sensor 50 and the electrical resistance detection sensor 60 quickly detect the life of the molten metal containers 1A, 1B, and 1C. By utilizing these detection sensors, it is possible to know the life of the molten metal container without waiting for the results of chemical analysis.

(Suspension process)
In the stopping step S21, use of the molten metal containers 1A, 1B, and 1C is stopped after the molten metal leakage is detected in the detecting step S11. A molten metal storage container in which leakage of molten metal has been detected cannot maintain the molten magnesium M at a high purity. Therefore, the molten metal containers 1A, 1B, and 1C may be replaced with other molten metal containers so as not to increase the impurity concentration of the molten magnesium M.

[5. Method for manufacturing sponge titanium]
The method for producing titanium sponge according to the present invention includes the step of producing titanium sponge using the aforementioned molten metal containers 1A, 1B, and 1C. According to the method for producing titanium sponge, the difference in Ni content of titanium sponge between batches is small, and stable operation is possible.

EXAMPLES The content of the present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Incidentally, in Examples 1 and 2 and Comparative Example 1, the Ni concentration was measured by ICP-OES.

(Example 1)
In Example 1, the inner cylinder 10 made of carbon steel, the outer cylinder 20 made of stainless steel, the upper lid 25, the connection part 30, the space 40, the pressure detection sensor 50, the metal pipe 55, and the inert A molten metal container 1A (see FIG. 1) provided with a gas supply pipe 70 and a Mg pipe 80 was assembled. Next, the molten metal container 1A was placed in a container 100 equipped with a heater 120. As shown in FIG. Next, after the molten magnesium M obtained in the electrolysis step was sent to the molten metal container 1A, the inside of the molten metal container 1A was filled with argon, and the temperature of the molten magnesium M was heated and maintained at 700°C.

Using the molten metal storage container 1A, the molten magnesium M produced in the electrolysis process is conveyed 400 times to the metal reduction reaction vessel used in the reduction process, and Ni in the molten magnesium M injected into the metal reduction reaction vessel Concentrations were measured periodically. During the 400th transport, the pressure detection sensor 50 detected a pressure fluctuation due to the leakage of the molten magnesium M, so the transport of the molten metal storage container 1A was stopped. The Ni concentration in the molten magnesium M transported in the molten metal storage container 1A for each batch from the first transport to the 399th transport is almost the same as the average concentration of Ni in the molten magnesium M produced in the electrolysis process. rice field. Specifically, the Ni concentration in the molten magnesium M in the first transportation was 1 mass ppm, and the Ni concentration in the molten magnesium M in the 399th transportation was equivalent to that in the first transportation, The Ni concentration in the molten magnesium M was 50 mass ppm at the 400th transfer when leakage of the molten magnesium M was detected.

(Example 2)
In Example 2, an inner cylinder 10 made of carbon steel, an outer cylinder 20 made of stainless steel, an upper lid 25, a connection part 30, a space 40, and an electric resistance detection sensor 60 arranged on the bottom side of the space 40 , a molten metal container 1C (see FIG. 3) provided with a metal pipe 65, an inert gas supply pipe 70, and a Mg pipe 80 was assembled. Next, the molten metal storage container 1C was stored in a container 100 equipped with a heater 120. As shown in FIG. Next, after the molten magnesium M obtained in the electrolysis step was sent to the molten metal container 1C, the inside of the molten metal container 1C was filled with argon, and the temperature of the molten magnesium M was heated and maintained at 700°C.

Using the molten metal container 1C, the molten magnesium M was conveyed 400 times from the electrolysis process to the reduction process, and the Ni concentration in the molten magnesium M injected into the metal reduction reactor was periodically measured. The material of the two metal wires in the cable 61 attached to the electrical resistance detection sensor 60 is Fe, and these metal wires are inserted through an insulator made of aluminum oxide and magnesium oxide so as not to contact each other. The metal wire was partially exposed. When the molten magnesium M is filled between the exposed metal wires, the electric resistance is lowered. Incidentally, the measurement tester (analog tester) attached to one end of the cable 61 was normally 200 to 500Ω. In the meantime, when the resistance value of the measuring tester dropped below 150Ω, it was determined that leakage of molten magnesium M from the inner cylinder 10 was detected, and use of the molten magnesium M was stopped. At the time of the 400th transportation, the resistance value of the measuring tester decreased to 150Ω or less, so the transportation of the molten metal storage container 1C was stopped. The Ni concentration in the molten magnesium M transported in the molten metal storage container 1C for each batch from the first to the 399th transportation was almost the same as the Ni concentration in the molten magnesium M produced in the electrolysis step. Specifically, the Ni concentration in the molten magnesium M in the first transportation was 1 mass ppm, and the Ni concentration in the molten magnesium M in the 399th transportation was equivalent to that in the first transportation, The Ni concentration in the molten magnesium M was 50 mass ppm at the 400th transfer when leakage of the molten magnesium M was detected.

(Comparative example 1)
In Comparative Example 1, the molten metal container 500 includes a clad steel outer cylinder 520 having an inner carbon steel and an outer stainless steel outer cylinder 520, an upper lid 525, an inert gas supply pipe 570, and a Mg pipe 580. (see Figure 6) was assembled. Next, the molten metal container 500 was placed in a container equipped with a heater. Using the molten metal storage container 500, the molten magnesium M was conveyed from the electrolysis step to the reduction step. Then, similarly to Example 1, the Ni concentration in the molten magnesium M injected into the metallic reduction reactor was periodically measured. As a result, the Ni concentration continued to increase gradually after the 200th transfer. As a result, the Ni concentration in the molten magnesium M during the first transport was 1 mass ppm, the Ni concentration in the molten magnesium M during the 200th transport was 3 mass ppm, and further during the 400th transport. The Ni concentration in the molten magnesium M exceeded 10 mass ppm. Therefore, the use of the molten metal container 500 was stopped during the 400th transfer.
When the Ni concentration in the molten magnesium M used in the reduction step is 3 ppm by mass or more, the Ni transferred to the titanium sponge is concentrated. There is a high probability that there will be. That is, in Comparative Example 1, it can be said that the molten magnesium M after at least the 200th transfer was not suitable for use in the reduction step, but the molten metal container 500 that was damaged 200 times after that was used. .

(Consideration by Example)
In Examples 1 and 2, even if the molten magnesium M leaked from the inner cylinder 10, the pressure detection sensor 50 and the electrical resistance detection sensor 60 quickly detected the leakage, so that the molten magnesium contaminated with Ni in the reduction process was removed. I was able to forestall the use of M. As a result, in the molten metal containers 1A and 1C used in Examples 1 and 2, even if the molten magnesium M leaks from the inner cylinder 10 into the space 40, the use of the molten magnesium M with an improved Ni concentration is stopped early. It can be said that it can contribute to the stable production of high-purity sponge titanium. In addition, in Examples 1 and 2, compared with Comparative Example 1, the number of times that the molten magnesium was able to be conveyed while the concentration of molten magnesium was low was large.

On the other hand, in Comparative Example 1, the Ni concentration in the molten magnesium M injected into the metallic reduction reactor was periodically analyzed, but when it was determined that the molten magnesium M was contaminated with Ni, the molten metal The wear and tear of the storage container 500 has progressed considerably. As a result, the contaminated molten magnesium M was repeatedly used in the reduction process, and the number of batches of titanium sponge in which the amount of Ni could not be reduced to the target amount or less increased. The reason for this is that as the number of batches increases, the inner carbon steel of the clad steel is gradually consumed, and the degree of Ni contamination gradually worsens. In addition, because it takes time to obtain the results of chemical analysis, it was not possible to decide to stop using the contaminated molten magnesium M at an appropriate time.

1A, 1B, 1C, 500 Molten metal container 10 Inner cylinder 11 Opening 12 Bottom wall 13 Side wall 20, 520 Outer cylinder 21 Opening 22 Bottom wall 23 Side wall 25, 525 Top cover 30 Connection part 40 Space 41, 42 Through hole 50 Pressure detection sensors 51, 61 Cables 55, 65 Metal pipe 60 Electric resistance detection sensors 70, 570 Inert gas supply pipes 80, 580 Mg pipe 81 Liquid feed port 100 Container 110 Furnace 111 Upper end surface 120 Heater 130 Support portion 131 Base end portion 132 Tip portion d Spacing distance S11 Detection step S21 Stop step V Vertical direction

Claims (12)

A carbon steel bottomed inner cylinder containing molten magnesium or molten magnesium chloride;
a bottomed outer cylinder provided around the inner cylinder and provided with an upper lid;
a connecting portion disposed between the inner cylinder and the outer cylinder and connecting the entire circumference of the opening of the inner cylinder and the outer cylinder;
a space defined between the inner cylinder and the outer cylinder;
A detection sensor connected to the space ,
A molten metal container for transporting molten magnesium or molten magnesium chloride . 2. The molten metal containment vessel of claim 1, wherein said connecting portion is made of carbon steel. 3. The container for containing molten metal according to claim 1, wherein said detection sensor is a detection sensor for detecting leakage of molten metal. The molten metal storage container according to any one of claims 1 to 3 , wherein the detection sensor is a pressure detection sensor. The molten metal storage container according to any one of claims 1 to 3 , wherein the detection sensor is an electrical resistance detection sensor. The molten metal container is for transporting molten magnesium,
The molten metal storage container according to any one of claims 1 to 5, wherein the Ni concentration of the molten magnesium to be transported is 1 mass ppm or less. A container comprising the molten metal container according to any one of claims 1 to 6 and a heater. Including a detection step of detecting leakage of molten metal using a molten metal container,
The molten metal container includes a bottomed carbon steel inner cylinder for containing molten magnesium or molten magnesium chloride, a bottomed outer cylinder provided around the inner cylinder and provided with an upper lid, and the inner cylinder. and the outer cylinder, a connecting portion that connects the entire circumference of the opening of the inner cylinder and the outer cylinder; a space defined between the inner cylinder and the outer cylinder; and a detection sensor connected to the space . 9. The molten metal leak detection method according to claim 8, wherein the connecting portion is made of carbon steel. 10. The method of detecting leakage of molten metal according to claim 8 or 9, wherein the detection sensor is a pressure detection sensor. 10. The method of detecting leakage of molten metal according to claim 8 or 9, wherein the detection sensor is an electrical resistance detection sensor. A method for producing titanium sponge, comprising a step of producing titanium sponge using the container for containing molten metal according to any one of claims 1 to 6 .

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