JP5751724B2 - Refractory metal manufacturing method - Google Patents

Description

  The present invention relates to a refractory metal production method for producing a refractory metal such as titanium metal or zirconium by a crawl method.

  The crawl method is used for industrial production of titanium metal. This method reduces titanium tetrachloride with magnesium by filling molten magnesium into a reaction vessel made of a heat-resistant metal having a diameter of 2 m and a height of about 3 m held at a high temperature, and dropping titanium tetrachloride into the reaction vessel. In this method, titanium metal is used. Titanium produced in the reaction vessel is a cylindrical block having a diameter of about 2 m and a height of about 2 m, and is produced in the reaction vessel in a porous state.

  This reduction reaction step usually lasts about 100 hours. In this process, magnesium chloride is by-produced. The vacuum separation step of the next step is to remove this byproduct and residual magnesium from the sponge titanium. In this process, a reaction vessel containing the produced sponge titanium and an empty reaction vessel are arranged adjacent to each other, the upper portions of both are connected by piping, and the inside of the latter reaction vessel is heated while heating the former reaction vessel from the outside. By vacuuming, the magnesium and magnesium chloride contained in the sponge titanium in the former reaction vessel are moved into the empty reaction vessel.

  The reaction vessels used in the reduction reaction step and the vacuum separation step are the same, and have a two-layer structure in which the inner surface of a vessel body made of stainless steel is lined with iron. The reason why the inner surface is made of iron is to prevent so-called heavy metal contamination that stainless steel components such as nickel and chromium contain in the sponge titanium via magnesium as a reducing agent in the reduction reaction step. However, as long as the inner surface of the container is iron, the tendency of the iron content level in the titanium sponge, particularly the iron content level in the first batch using an unused reaction container, is unavoidable. This tendency is similarly observed not only on the surface of the sponge titanium but also in the center.

  High iron concentration sponge titanium is not a defective product, but its product value is significantly inferior to low iron concentration sponge titanium for aircraft and so on, so an unused reaction vessel is used for the reduction reaction process first. The occurrence of high-iron and low-grade products in the first batch is an obstacle in production management and yield management.

  One of the countermeasures for preventing the occurrence of high-iron low-grade products in the first batch is an alloy forming method described in Patent Document 1. This is one of the processes to be performed before using the manufactured unused reaction vessel. The same metal as the metal to be produced is held in the reaction vessel, and the reaction vessel is evacuated. Heat from outside. As a result, the same metal as the generated metal is evaporated in the reaction vessel and deposited on the inner surface of the vessel, thereby forming an alloy layer of iron and the generated metal on the inner surface of the reaction vessel. The main point of the alloy forming method is that the alloy layer prevents the elution of iron from the inner surface of the reaction vessel into the molten magnesium and prevents the generation of high iron low-grade products in the first batch.

  However, this alloy formation method has the following problems. First, a dedicated pretreatment must be performed in advance on the manufactured reaction vessel. This pretreatment is an isolated process separate from the original operation for producing titanium sponge. For these reasons, the adverse effects on the original operation and the increase in costs associated with the pretreatment are significant problems. Second, problems remain in terms of effectiveness and feasibility. This is because, in this alloy formation method, it is necessary to reduce the pressure in the reaction vessel in order to cause a gas phase reaction, and the degree of pressure reduction is preferably 10 to 100 Pa according to the description in Patent Document 1. However, the vapor pressure of titanium metal is 10 Pa or less at 1000 ° C. For this reason, the generated metal held in the reaction vessel hardly evaporates at a reduced pressure of about 10 to 100 Pa.

  Moreover, even if the degree of vacuum in the reaction vessel is further reduced, the amount of evaporation is extremely small, and it is considered that it does not lead to the formation of a sufficient alloy layer. In order to increase the vapor pressure, a method of increasing the temperature of the reaction vessel is conceivable, but the melting point of stainless steel is at most about 1050 ° C., which does not lead to an increase in the amount of evaporation. Therefore, the alloy forming method described in Patent Document 1 still has problems in terms of effectiveness and feasibility.

  For this reason, in actual operation, the occurrence of high-iron and low-grade products in the first batch when an unused reaction vessel is used is recognized as an inevitable problem.

  In addition, in the production of sponge titanium by the crawl method, there is also a problem of chlorine residue in the vacuum separation process, apart from the generation of high iron low-grade products due to iron contamination. This is as follows. In the vacuum separation process, the separation processing time is determined from various calculated values and empirical values, and based on this, a guideline for the processing end timing is set. However, although rarely, magnesium and magnesium chloride may remain in the sponge titanium after the separation treatment, even though the criteria for completion of the separation are satisfied. Sponge titanium with magnesium chloride remaining becomes a defective product called high chlorine sponge titanium (high chlorine defective product) and cannot be sold as it is.

  The reseparation process described in Patent Document 2 is considered to solve the problem caused by chlorine contamination. In the re-separation process, the manufactured high chlorine sponge titanium is crushed to a particle size of about 2 to 50 mm, and this is again loaded into the reaction vessel and vacuum-separated. As a result, the sponge titanium particles in the reaction vessel are removed from the remaining magnesium and magnesium chloride, resulting in a good product from which chlorine has been removed.

JP 2009-127107 A JP 2001-262246 A

  The object of the present invention is to efficiently and reliably prevent the problem of iron contamination caused by the iron lining of the reaction vessel, and further the problem of heavy metal contamination in the reaction vessel without the iron lining, without adversely affecting the original operation. An object of the present invention is to provide an extremely rational refractory metal production method that can be solved.

  By the way, as described above, there is a regeneration treatment of high chlorine sponge titanium, that is, a re-separation step, as one step for producing sponge titanium by the crawl method. The reaction vessel used for this re-separation treatment was the same as that used for the production of sponge titanium by the crawl method, and in particular, it was an old reaction vessel after repeated use. The reason is as follows.

  As described above, the reaction vessel used for the production of titanium sponge by the crawl method is usually a two-layer structure in which the inner surface of the vessel body made of stainless steel is lined with an iron material, and is repeatedly used in the reduction reaction step. When the iron content on the inner surface elutes into the molten magnesium in the container, the thickness of the iron material layer is reduced. For this reason, when the number of times of use increases, the stainless steel is exposed depending on the location, and the elution of the stainless steel component from the exposed portion to the molten magnesium occurs. Since such a container maintains the quality of sponge titanium, it is not actively used as a reaction container, but is used as a container for re-separation.

  In the re-separation process described above, only a small amount of magnesium and magnesium chloride remaining in the high chlorine sponge titanium is removed by a combination of heating and evacuation, and the container does not fill with molten magnesium. Even if stainless steel is exposed, the problem of elution of stainless steel components does not occur. Above all, high chlorine sponge titanium is a defective product that has been contaminated with chlorine, so if there is no fatal problem, using an old reaction vessel that can no longer be used for the original operation will increase the number of times the reaction vessel is used. Was considered economical. For this reason, an old reaction vessel that can no longer be used for the original operation has been used for the re-separation process described above.

  Under such circumstances, the present inventor has focused on the combination of the manufactured unused reaction vessel and the reseparation process. In other words, aside from psychological resistance, even if an unused brand new reaction vessel is loaded with defective high chlorine sponge titanium and re-separated, there will be no adverse effects on the reaction vessel. Therefore, it can be expected that a high-quality alloy layer that is extremely effective in preventing the generation of low-grade high-iron products, which is a problem with unused reaction vessels, is formed.

  This is because even though high chlorine sponge titanium is a defective product, the chlorine concentration is only higher than the standard value, so there should be no problem even if it is used in a new reaction vessel. In fact, when using an old reaction vessel, there was no particular problem on the side of the reaction vessel. This idea is consistent with the fact that high-iron and low-grade products do not occur from the second batch onward after the sponge titanium is produced once used in the reduction reaction step.

  The present inventor has proved the correctness of this idea through further studies, and has reached the following conclusion. If an unused reaction vessel is used for re-separation of high chlorine sponge titanium, not only can the problem of high-iron low-grade products generated by the reaction vessel be solved, but re-separation is an indispensable process for operation. Therefore, since this also serves as a measure against iron contamination, an isolated process different from the original operation for producing sponge titanium, which is a problem in the alloying method described in Patent Document 1, is not necessary. A very effective rationalization is achieved.

  In addition to this, solid phase diffusion treatment by loading sponge titanium particles and alloying thereby prevent heavy metal contamination by nickel and chromium in reaction vessels that are not iron-lined inside, that is, reaction vessels made of stainless steel alone. Also proved effective. That is, according to the solid phase diffusion treatment by loading sponge titanium particles, even when the inner surface of the reaction vessel is stainless steel, the inner surface material and the alloy layer of titanium are formed on the inner surface layer portion. And the elution of chromium is effectively prevented.

The refractory metal production method of the present invention was developed on the basis of such knowledge, and has a high melting point by a reduction reaction in which a chloride of a refractory metal is brought into contact with a molten metal as a reducing agent in a metal reaction vessel. In the method for producing a refractory metal for producing a metal, the reaction vessel is heated to a temperature of 800 ° C. or higher while the refractory metal particles are in contact with the produced unused reaction vessel inner surface. After the solid phase diffusion treatment of the melting point metal, the reaction vessel is used for the first reduction reaction , and in particular, the high melting point metal is titanium, and the solid phase diffusion treatment is performed for reseparation of sponge titanium particles. It is processing .

  In the refractory metal production method of the present invention, the refractory metal particles are in direct contact with the produced unused reaction vessel inner surface, and moreover, because it is a multipoint contact, in the surface layer portion of the reaction vessel inner surface. The solid phase diffusion reaction proceeds in the entire contact region of the refractory metal particles, and an alloy layer of the refractory metal and the container inner surface material is formed on the entire inner surface of the contact region. In the formation of this alloy layer, it is considered that the solid phase diffusion reaction proceeds preferentially in the direction parallel to the inner surface rather than in the depth direction of the container material.

And in the manufacture of sponge titanium by the crawl method , in order to prevent the first batch of iron contamination which becomes a problem when an unused reaction vessel whose inner surface is lined with iron is used in the reduction reaction step, The method for producing a refractory metal of the present invention is particularly effective when the reaction vessel is used for a reseparation process which is a post-treatment of high chlorine sponge titanium.

  That is, regardless of whether the titanium sponge is a high-grade product or a high chlorine sponge titanium, the titanium sponge particles are brought into contact with the inner surface of the reaction vessel by loading the sponge titanium particles into an unused reaction vessel, and the re-separation treatment is performed in this state. As a result, a solid phase diffusion reaction occurs in the entire sponge titanium particle contact region on the inner surface of the reaction vessel, and an iron-titanium alloy layer is formed on the inner surface layer portion. As a result, the first batch of iron contamination can be prevented without interposing an alloying process independent of the original operation on the manufactured unused reaction vessel. In forming the alloy layer, the inner surface of the container and the sponge titanium particles are in multi-point contact, and the solid phase diffusion reaction may proceed preferentially in the direction parallel to the inner surface rather than in the depth direction of the container material. As mentioned above, it is thought that it contributes.

  Further, even in a reaction vessel made of stainless steel alone in which the iron lining on the inner surface is omitted, the inner surface material and the titanium-based alloy layer are formed on the surface layer portion of the inner surface of the container according to the solid phase diffusion reaction loaded with sponge titanium particles. . This alloy layer can effectively prevent not only iron in the inner surface material but also heavy metals such as nickel and chromium from eluting in the first batch.

Therefore, the inner surface of the reaction vessel is iron or an iron alloy such as stainless steel. The refractory metal is titanium .

  An important factor in the method for producing a refractory metal of the present invention is the particle size of the refractory metal particles brought into contact with the inner surface of the reaction vessel. The particle size is desirably 4 to 35 mm, and more desirably 7 to 26 mm. If this particle size is too small, the amount of refractory metal particles to be used increases, and the refractory metal particles adhere to the inner surface of the container at the stage of solid phase diffusion treatment, pushing the processed material from the reaction container. There are problems such as difficulty in removal when removing. On the contrary, if this particle size is too large, the contact area between the inner surface of the reaction vessel and the refractory metal particles becomes small, and it becomes difficult to form an effective alloy layer.

  Another important factor is the amount of high melting point metal particles charged into the reaction vessel, strictly speaking, the contact range of the high melting point metal particles with the inner surface of the vessel. This is because the alloy layer by the solid phase diffusion reaction is formed only in the region where the refractory metal particles are in contact. For this reason, since the high melting point metal grains are not loaded below the rooster, an alloy layer is not formed. However, since the molten metal that is the reducing agent contained in the reaction vessel has the highest temperature due to the reaction heat near the liquid surface, it is not a big problem that an alloy layer is not formed below the rooster. Conversely, the presence of the alloy layer near the liquid surface at the highest temperature is important. From this viewpoint, the formation range of the alloy layer by solid phase diffusion reaction includes 80% or more of the liquid surface fluctuation range of the molten metal as the reducing agent. In practice, the range of contact of the refractory metal particles loaded in the reaction vessel with the inner surface of the vessel is the formation range of the alloy layer by the solid phase diffusion reaction. The upper surface level of the charged particles is a level that includes 80% or more from the lower end of the liquid level fluctuation range during the reduction reaction of the molten metal that is the reducing agent. It is desirable to form an alloy layer, more desirably 90% or more, and still more desirably 100% or more.

  The temperature in the solid phase diffusion reaction is also an important factor, and this is set to 800 ° C. or higher in the method for producing a refractory metal of the present invention. If the reaction temperature is less than 800 ° C., it becomes difficult to form an alloy layer on the inner surface of the container, and even if formed, an extremely long processing time is required. A preferred lower limit temperature is 900 ° C. or higher. With respect to the upper limit of the reaction temperature, the temperature at which the inner surface material of the reaction vessel and the refractory metal are alloyed by melting (eutectic reaction) is 1083 ° C. because it is necessary to use solid phase diffusion reaction. Therefore, in order to advance the diffusion reaction efficiently, it is desirable to advance the alloy formation reaction at 1082 ° C. However, it is more desirable to operate at 1070 ° C. or lower in order to reliably avoid alloy formation due to temperature variations. This temperature overlaps with the heating temperature in the vacuum separation process in the production of sponge titanium by the crawl method.

  The treatment time is also an important factor, but it is determined as appropriate depending on the particle size of the refractory metal particles and the treatment temperature, and its length does not cause a major problem, so it is not specified, but in the case of an extremely short treatment time Since the formation of the alloy layer becomes insufficient and, on the contrary, an extremely long processing time unnecessarily increases the cost, 40 to 200 hours are desirable, and 70 to 150 hours are desirable.

  The method for producing a refractory metal of the present invention relates to a reaction vessel used for producing a refractory metal by a reduction reaction using a molten metal as a reducing agent, and contacting the refractory metal particles with the inner surface of the vessel at an unused stage. By causing a solid phase diffusion reaction, an inner layer material and an alloy layer of a refractory metal are surely formed on the inner surface layer, so that this inner surface becomes a problem when this unused reaction vessel is used for the first reduction reaction. Contamination due to material elution can be effectively avoided.

In particular, Oite the production of titanium sponge by the Kroll process, by using a reaction vessel of the unused re-separation step is performed to reproduce high chlorine titanium sponge produced by the vacuum separation step, the reaction vessel inner surface Since the solid phase diffusion treatment is performed, this solid phase diffusion treatment can be performed without adding a new step, and the effect of omission of the step is great.

It is a conceptual diagram of the refractory metal manufacturing method which shows one Embodiment of this invention.

  Embodiments of the present invention will be described below. The method for producing a refractory metal according to this embodiment is a method for producing sponge titanium by a crawl method, and includes a reduction reaction step and a vacuum separation step. In the reduction reaction step, molten magnesium is filled in a reaction vessel maintained at a high temperature, and titanium tetrachloride is dropped into the reaction vessel to reduce titanium tetrachloride with magnesium, and sponge titanium is placed on the rooster in the reaction vessel. Is generated.

  Magnesium chloride is produced as a by-product during the reduction reaction process, and this is appropriately extracted from the reaction vessel, but it is impossible to completely extract it. Therefore, this magnesium chloride reacts with unreacted magnesium even after the end of the process. Remain in the container. Removal of these from the sponge titanium is the next vacuum separation step.

  In the vacuum separation process, the reaction vessel containing the produced titanium sponge and the empty reaction vessel are arranged adjacent to each other, the upper parts of both are connected by piping, and the inside of the latter reaction vessel is heated while the former reaction vessel is heated from the outside. Is evacuated to move the magnesium and magnesium chloride contained in the sponge titanium in the former reaction vessel into the empty reaction vessel.

  However, although rare, magnesium and magnesium chloride may remain in the sponge titanium after the vacuum separation treatment. Sponge titanium in which magnesium chloride remains is a defective product called high chlorine sponge titanium and cannot be sold as it is. For this reason, the high chlorine sponge titanium is crushed and loaded again into the reaction vessel for vacuum separation. This is a second vacuum separation step, that is, a re-separation step.

  The reaction vessels used in the reduction reaction step and the vacuum separation step are the same, and have a two-layer structure in which the inner surface of a vessel body made of stainless steel is lined with iron. When a reaction vessel having a two-layer structure, particularly a manufactured unused reaction vessel, is used in the reduction reaction step, iron is eluted from the inner surface of the vessel in the first batch, and the sponge titanium produced in the vessel is absorbed by the iron. It becomes contaminated with high iron and low grade products.

  Therefore, in the refractory metal production method of the present embodiment, the produced unused reaction vessel is used for the reseparation step. Specifically, as shown in FIG. 1, the high chlorine sponge titanium pulverized particles 10 are loaded on a rooster 21 in an unused reaction vessel 20. The loading level L1 is the upper end of the contact area with the pulverized particles 10 on the inner surface of the reaction vessel 20, and is higher than the level L2 including 80% from the lower end of the liquid level fluctuation range S of the molten magnesium in the reaction vessel in the reduction reaction step. Here, the level includes 100%, that is, the upper end of the liquid level fluctuation range S or above. The particle size of the pulverized particles 10 is approximately 1/2 to 1 inch, and is about 20 mm on average.

  Then, the unused reaction vessel 20 loaded with the pulverized particles 10 is set in the heating furnace 30, and connected to another reaction vessel for reduction reaction arranged next to the reaction vessel 20 at the upper part, and another reaction is performed. With the inside of the reaction vessel 20 evacuated through the vessel, the reaction vessel 20 is heated to 800 ° C. or higher and to 1083 ° C. or lower which is an alloying temperature by melting iron and titanium. This state is continued for about 100 hours. Thereby, the pulverized particles 10 in the reaction vessel 20 become non-defective products in which the chlorine concentration is reduced to a predetermined value or less by removing the magnesium and magnesium chloride remaining inside.

  At the same time, the heating temperature and the heating time here satisfy the solid phase diffusion conditions of titanium. For this reason, the solid phase diffusion reaction of titanium occurs on the inner surface of the reaction vessel 20, particularly the inner surface that contacts the loaded pulverized particles 10, and the reaction takes place at the contact portion with the pulverized particles 10, as well as the inner surface layer. Since it spreads in a direction parallel to the surface rather than in the depth direction of the part, an alloy layer of iron and titanium is formed on the entire inner surface of the pulverized grain 10 loading region. The alloy layer forming region includes a liquid level fluctuation range S of molten magnesium in the reaction vessel 20 in the reduction reaction step. For this reason, when the unused reaction vessel 20 is first used in the reduction reaction step, that is, the iron contamination which becomes a problem when the first batch is used, the reaction vessel 20 is suppressed to a level where there is no problem.

  As an example of the present invention, the effect of preventing iron contamination when the used unused reaction vessel 20 was used for re-separation was investigated. Specifically, after the unused reaction vessel 20 is used for the re-separation process, the reaction vessel 20 is used for the reduction reaction step-vacuum separation step, and the high chlorine charged in the reaction vessel 20 by the re-separation process. The degree of influence of the particle size of the sponge titanium pulverized particles 10 on the iron contamination in the first batch of the subsequent reduction reaction step was investigated. The survey results are shown in Table 1 in comparison with the results when the unused reaction vessel 20 was used as it was in the reduction reaction step-vacuum separation step.

  The comparative example 1 shows the result at the time of using the manufactured unused reaction container 20 for a reduction reaction process-vacuum separation process, without using it for the re-separation process of high chlorine sponge titanium. “Surface concentration of sponge titanium in the first batch” in Table 1 is the average iron at a depth of 50 mm from the outer peripheral surface of the cylindrical titanium sponge lump extracted from the reaction vessel after the reduction reaction step-vacuum separation step. The density is shown as a relative value when Comparative Example 1 is set to 100.

  As can be seen from Table 1, when an unused reaction vessel 20 is used for re-separation of high chlorine sponge titanium, iron contamination of the first batch of sponge titanium is effective when the reaction vessel 20 is used in the reduction reaction step. Is prevented. It can be seen that the particle size of the high chlorine sponge titanium crushed particles 10 loaded in the unused reaction vessel 20 is particularly preferably around 7 to 26 mm.

  Regarding the dechlorination effect in the re-separation treatment, there was no difference between the old and new reaction vessels. When an old reaction vessel is used for the re-separation process, an unused reaction vessel 20 is used for the reduction reaction step, and the generation of high iron low-grade products in the first batch is inevitable. In the case where the pretreatment for preventing the generation of high iron and low-grade products in the first batch is a dedicated process unrelated to the original operation, the process becomes complicated and the cost increases.

10 pulverized granules of sponge titanium 20 reaction vessel 21 rooster 30 heating furnace

Claims (3)

In a refractory metal production method for producing a refractory metal by a reduction reaction in which a chloride of a refractory metal is brought into contact with a molten metal as a reducing agent in a metal reaction vessel,
After subjecting the inner surface of the reaction vessel to a solid-phase diffusion treatment of the refractory metal by raising the temperature of the reaction vessel to 800 ° C. or higher in a state where the refractory metal particles are in contact with the inner surface of the manufactured unused reaction vessel , A refractory metal production method using the reaction vessel for the first reduction reaction ,
The method for producing a refractory metal , wherein the refractory metal is titanium and the solid phase diffusion treatment is a reseparation treatment of sponge titanium particles . The method for producing a refractory metal according to claim 1 , wherein the average particle size of the refractory metal particles is 4 to 35 mm. 3. The refractory metal production method according to claim 1 or 2 , wherein the molten metal in the reaction vessel is subjected to solid phase diffusion treatment on the inner surface of the vessel containing 80% or more of the range in which the liquid level fluctuates during the reduction reaction. Production method.

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