JP2018172755A - Method of manufacturing sponge titanium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a highly pure sponge titanium capable of diminishing a chip-off work load in a reduction reaction vessel, and prolonging a life of the reduction reaction vessel.SOLUTION: In a method of manufacturing a sponge titanium by a Kroll method, the method of manufacturing a highly pure sponge titanium includes: a process of chipping off to remove deposited titanium which deposits on an inner surface of a reduction reaction vessel and on a surface of a grade when reductively reacting last time; and a process of thereafter reusing the reduction reaction vessel with which chip-off removal is done to manufacture a sponge titanium by the Kroll method, where the chip-off removal of titanium is done so that the exposure rate A is 70% or more in the chip-off removal.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing high purity sponge titanium, in which titanium tetrachloride is reduced with metallic magnesium to produce sponge titanium.

  Conventionally, titanium metal is industrially manufactured based on sponge titanium manufactured by a crawl method. In recent years, demand for high-purity titanium for semiconductor devices has increased, and accordingly, it has been demanded to produce high-purity sponge titanium at low cost.

  The titanium sponge production process by the crawl method is roughly divided into four processes, ie, a chlorodistillation process, a reduction separation process, a crushing process, and an electrolysis process.

  The reduction separation process which is one of these processes includes a reduction process and a vacuum separation process. In the reduction step, titanium tetrachloride is added dropwise to molten metal magnesium in a stainless steel reduction reaction vessel to cause a reduction reaction, thereby generating sponge titanium. Next, in the vacuum separation step, the sponge titanium produced in the reduction step is evacuated under high temperature and reduced pressure to produce sponge titanium from which the remaining magnesium chloride and metal magnesium are removed (Non-patent Document 1). .

  The sponge titanium after the vacuum separation is extruded by a punching floor member installed at the bottom of the container called a rooster or a punching punch. Moreover, it was thought that the remaining sponge titanium adhering to the extracted rooster and reduction reaction vessel surface contained a large amount of impurity metals. Therefore, titanium-based impurities (hereinafter referred to as “adhered titanium”) mainly composed of titanium adhering to the inner surface of the reduction reaction vessel and the surface of the rooster are physically removed by chipping called “hanging removal”. It was thought that the purity of the sponge titanium produced in the batch was improved (Patent Document 1).

  From this, it is considered that the more the titanium attached to the inner surface of the reduction reaction vessel is cut, the more the purity is improved, and it is considered preferable to remove the attached titanium so that the background is exposed over a wide area in the reduction reaction vessel. And these hanger removal operations have been considered to be unavoidable, although the productivity is remarkably deteriorated.

  In addition, in the method for producing high-purity titanium sponge according to the present invention, since there is elution of Ni from the material of the reduction reaction vessel, a clad vessel or a buttering vessel in which the inner surface of the reduction reaction vessel is made of iron is used. Since these reduction reaction containers for high-purity titanium sponge are expensive, it is important to extend the container life. And since the lifetime of a reduction reaction container is influenced by the thickness of the inner and outer surfaces of the container, it is important how to suppress the amount of thickness reduction per cycle of the reduction separation process on the outer and inner surfaces of the reduction reaction container. As a method for suppressing the thickness reduction per cycle of the reduction separation process, a method using a special stainless steel having excellent oxidation resistance on the outer surface side of the clad steel is known (Patent Document 1).

  However, the stainless steel as described in Patent Document 1 has a small circulation amount and is expensive, and even if it exhibits an effect on oxidation consumption on the outer surface of the reduction reaction vessel, It cannot prevent thinning. Therefore, a method for suppressing the thinning of the inner surface of the reduction reaction container is also required at the same time.

Resources and materials Vo. 1.109 P1157-1163 (1993)

JP 2006-265587 A JP 2006-131976

  The present invention solves the above-mentioned problems related to the production of high-purity sponge titanium, and can reduce the load of the suspension removal work in the reduction reaction vessel, and can extend the life of the reduction reaction vessel. The purpose is to provide.

  In order to solve the above-mentioned problems, the present inventors focused on the Ni contamination path in the adhered titanium adhering to the inner surface of the reduction reaction container after taking out the sponge titanium produced from the reduction reaction container, and intensively studied As a result, the mechanism of Ni concentration in the attached titanium is not contamination due to the gettering effect on the initially formed titanium described in Patent Document 1, but Ni in the raw material Mg, and in the reduction reaction vessel during the reduction reaction It is found that the main factor is that Ni eluted from molten Mg from the metal does not evaporate in the vacuum separation process after the reduction reaction, and the remaining Ni in Mg is taken into the adhered titanium on the inner surface of the reduction reaction vessel. It was.

The present invention has been made based on such findings and is as follows.
That is, according to the present invention (1), in the production of sponge titanium by the crawl method, the suspension is removed after removing the attached titanium adhering to the inner surface of the reduction reaction vessel and the surface of the rooster in the previous reduction reaction. Reusing the reduction reaction vessel that has been removed, a method for producing high-purity sponge titanium having a step of producing sponge titanium by a crawl method,
In the removal of the suspension, the background is exposed after the removal of the suspension with respect to the total area of the inner surface of the reduction reaction vessel and the surface of the rooster in a range of 20% from the bottom to the total height of the reduction reaction vessel. Removing the attached titanium so that the ratio of the total area of the inner surface of the reduction reaction vessel and the surface of the rooster (exposure rate A) is 70% or more,
The present invention provides a method for producing high-purity titanium sponge.

  Further, the present invention (2) is characterized in that the melt outlet of the reduction reaction vessel is located in a range of 5 to 20% from the bottom with respect to the total height inside the reduction reaction vessel ( The method for producing high purity titanium sponge 1) is provided.

  According to the present invention, there is provided a method for producing a high-purity sponge titanium, which can reduce the load of the suspension removal work in the reduction reaction vessel and can extend the life of the reduction reaction vessel. Can be provided.

It is a typical longitudinal end view which shows the reduction reaction apparatus used for the manufacturing method of the high purity sponge titanium of this invention. It is a vertical end view of the reduction reaction container for demonstrating the total height of a reduction reaction container.

The method for producing high-purity sponge titanium according to the present invention was carried out by removing suspended titanium from the inner surface of the reduction reaction vessel and the surface of the rooster in the previous reduction reaction in the production of sponge titanium by the crawl method. After that, reusing the reduction reaction vessel from which the removal of hulls is performed, and a method for producing high-purity sponge titanium having a step of producing sponge titanium by a crawl method
In the removal of the suspension, the background is exposed after the removal of the suspension with respect to the total area of the inner surface of the reduction reaction vessel and the surface of the rooster in a range of 20% from the bottom to the total height of the reduction reaction vessel. Removing the attached titanium so that the ratio of the total area of the inner surface of the reduction reaction vessel and the surface of the rooster (exposure rate A) is 70% or more,
Is a method for producing high-purity titanium sponge.

  The method for producing high-purity titanium sponge of the present invention is a crawl method, that is, by previously putting molten Mg in a reduction reaction vessel, dropping titanium tetrachloride into the reduction reaction vessel, and reacting with molten Mg, It is a manufacturing method of high purity sponge titanium which manufactures sponge titanium.

  Then, in the method for producing high-purity sponge titanium according to the present invention, the adhered titanium adhered to the inner surface of the reduction reaction vessel and the surface of the rooster in the previous reduction reaction is scraped to remove the adhered titanium from the inner surface of the reduction reaction vessel and the rooster. The method for producing high-purity sponge titanium having a step of removing sponge from the surface, that is, removing the suspension and then reusing the reduction reaction vessel from which the suspension has been removed to produce sponge titanium by the crawl method It is.

  In the present invention, high purity titanium sponge refers to titanium sponge having a Ni content of 0.5 mass ppm or less.

  The reduction reaction container according to the method for producing high-purity sponge titanium of the present invention is a clad container or a buttering container in which iron is clad on the inner surface of stainless steel, and the rooster is made of iron.

  The structure of the reduction reaction container according to the method for producing high purity titanium sponge of the present invention will be described with reference to FIG. FIG. 1 is a schematic end view showing a reduction reaction apparatus used in the method for producing high purity titanium sponge of the present invention. The reduction reaction device 1 includes a reduction reaction vessel 2, an eluate extraction pipe 4 connected to the lower part of the reduction reaction vessel 2, and an inner lid 6 and an outer lid 5 that block the upper side of the reduction reaction vessel 2. The bottom of the reduction reaction vessel 2 is closed with a bottom cap 8. A rooster 3 is installed in the lower part of the reduction reaction vessel 2. In the reduction process, the production of titanium sponge is carried out by putting molten Mg in the reduction reaction vessel 2 in advance, dropping titanium tetrachloride into the reduction reaction vessel 2 and reacting with molten Mg, thereby producing a roastol. The formed sponge titanium is deposited on 3. In the reduction step, by-product magnesium chloride is extracted from the eluate extraction tube 4 while dropping titanium tetrachloride into molten Mg. After the dropping of titanium tetrachloride into molten Mg is completed, a separation step is performed in which the inside of the reduction reaction vessel 2 is heated in a vacuum to separate unreacted Mg and by-product magnesium chloride in vacuum. After performing the separation step, the titanium sponge lump generated together with the reduction reaction vessel is cooled, the bottom cap 8, the inner lid 6 and the outer lid 5 are removed, the sponge titanium lump is pushed up together with the rooster 3 from below, and the sponge titanium lump is removed. Then, it is taken out of the reduction reaction container 2.

  Subsequently, in order to reuse the reduction reaction vessel 2 for the next reduction reaction, the removal of the attached titanium adhering to the inner surface of the reduction reaction vessel 2 and the surface of the rooster 3 after removing the sponge titanium lump is performed. . In the removal of suspension, when the position 14 that is 20% lower than the total height 13 of the reduction reaction vessel 2 is set as the upper end of the 20% range, it exists in the lower portion 15 from the upper end 14 of the 20% range. The inner surface of the reduction reaction vessel 2 and the surface of the rooster 3 are removed from the center of the titanium, and if necessary, the inner surface of the reduction reaction vessel 2 in the range 16 above the upper end 14 of the 20% range is removed. Do. In the case of the reduction reaction vessel 2, the bottom surface 9 and the side surface 10 of the bottom cap 8 are also within the 20% range from the bottom, and after removing the suspension, the bottom cap 8 is again connected to the bottom portion of the reduction reaction vessel 2. Therefore, the bottom surface 9 and the side surface 10 of the bottom cap 8 are the objects to be removed.

  Then, the reduction reaction vessel 2 after removing the hanger is reused for the next reduction reaction.

  In the present invention, the “total height of the reduction reaction vessel” means that when the reduction reaction vessel is viewed in the vertical direction, the reduction reaction vessel is reduced from the deepest position inside the reduction reaction vessel in contact with molten Mg. The length to the upper end position of the inner surface of the reaction vessel is indicated. When the reduction reaction container does not have a bottom cap as in the embodiment shown in FIG. 2 (A), the deepest position of the bottom of the reduction reaction container is the deepest position inside the reduction reaction container, When the reduction reaction container has a bottom cap as in the embodiments shown in FIGS. 2B to 2D, the deepest position of the bottom cap is the deepest position inside the reduction reaction container. In the embodiments (A) to (D) shown in FIG. 2, the position indicated by reference numeral 11 is the deepest position inside the reduction reaction vessel in contact with molten Mg, and the position indicated by reference numeral 12 is The distance from the position indicated by reference numeral 11 to the position indicated by reference numeral 12 is the total height 13 of the reduction reaction container, which is the upper end position of the inner surface of the reduction reaction container. Further, in the present invention, the “range of 20% from the bottom relative to the total height of the reduction reaction vessel” is a position higher by 20% of the total height inside the reduction reaction vessel than the deepest position inside the reduction reaction vessel. Is the lower part from the position of the upper end of the 20% range.

  In the method for producing high-purity sponge titanium according to the present invention, the method for removing the suspension is not particularly limited, and may be any method that is used in the production of ordinary sponge titanium, for example, by hitting the adhered titanium with a chipping machine. A method of scraping while scraping, a method of removing with a scraper or a wire brush, and the like can be mentioned. The chipping machine method is suitable for removing strongly adhered titanium and large adhered titanium on the inner surface of the reduction reaction vessel and the surface of the rooster, and the method using a scraper or wire brush is suitable for reducing reaction. It is suitable for removing adhered titanium that has weak adhesion to the inner surface of the container and the surface of the rooster.

  In the suspension removal according to the method for producing high-purity titanium sponge of the present invention, removal of suspension is performed for the total area of the inner surface of the reduction reaction vessel and the surface of the rooster in the range of 20% from the bottom to the total height of the reduction reaction vessel. The ratio of the total area of the inner surface of the reduction reaction vessel and the surface of the rooster whose surface is exposed after being performed (also referred to as exposure rate A) is 70% or more, preferably 80% or more, particularly preferably 90% or more. Then, the attached titanium is removed by suspending. In the method for producing high-purity titanium sponge according to the present invention, in the removal of suspension, the attached titanium is removed by suspension so that the exposure rate A after removal of the suspension is within the above range. Adhesive titanium with a high Ni content remaining on the surface is removed from the inner surface of the reduction reaction vessel and the surface of the rooster, so that the load of the removal work can be reduced, and the sponge titanium produced in the next batch Ni contamination on the surface can be efficiently reduced.

  By repeatedly reusing the reduction reaction vessel and the rooster, the inner surface of the reduction reaction vessel and the surface of the rooster are partially alloyed by reacting with sponge titanium. The iron surface of the inner surface of the original reduction reaction vessel and the iron surface of the surface of the rooster, or the surface of the titanium iron alloy on the inner surface of the reduction reaction vessel whose average Ti concentration from the surface layer to 300 μm is 30% by mass or less in surface analysis by EPMA And the titanium-iron alloy surface of the surface of the rooster.

  In the present invention, “the surface is exposed” means that there is no adhesion of attached titanium, and the original iron surface or alloyed titanium-iron alloy surface of the inner surface of the reduction reaction vessel or the surface of the rooster is visually confirmed. Refers to that.

  In the present invention, it is a method for measuring the total area of the inner surface of the reduction reaction vessel and the surface of the rooster, where the background is exposed. First, after removing the suspension, the total height of the reduction reaction vessel is within a range of 20% from the bottom. Take pictures of the inner surface of the reduction reaction vessel and the surface of the rooster. At this time, the imaging range of one field of view is about 300 mm × 400 mm, the number of pixels is 1600 × 1200 pixels or more, and the inner surface of the reduction reaction vessel and the surface of the rooster are within 20% of the total height of the reduction reaction vessel. Shoot over the entire range. Next, each obtained photograph is binarized using an image processing analysis device (manufactured by Luzex AP NIRECO), and then a portion where the background is exposed is selected to measure the area ratio. The area ratio is obtained by the formula “(X / (X + Y)) × 100”, where X is the area of the portion where the background is exposed, and Y is the area of the other portion. About each obtained photograph, an area rate is measured by the said method, and the average value of the area rate of all the photographs exists in the range of 20% from the bottom with respect to the exposure rate A (%) (the total height of a reduction reaction container). The ratio of the total area of the inner surface of the reduction reaction vessel and the surface of the rooster, to which the ground surface is exposed after the removal of the suspension, with respect to the total area of the inner surface of the reduction reaction vessel and the surface of the rooster.

In the suspension removal according to the method for producing high-purity sponge titanium of the present invention, the inner surface of the reduction reaction vessel after removing the suspension in a range excluding the range of 20% from the bottom relative to the total height inside the reduction reaction vessel. The difference between the exposure rate B (%) of the surface of the surface of the rooster and the exposure rate C (%) of the background surface of the reduction reaction vessel and the surface of the rooster before removing the hull (exposure rate B−exposure rate C) ) Is 20% or less, preferably 10% or less, particularly preferably 0%, so that the attached titanium is removed by suspending, so that the load of the detaching operation can be reduced. Therefore, it is preferable in that the life of the reduction reaction vessel can be extended. The titanium sponge above the lower 20% range relative to the total height of the reduction reaction vessel is less contaminated with Ni due to leaving Ni in the melt during vacuum separation, so the total height of the reduction reaction vessel Even if the attached titanium adhering to the range excluding the 20% range from the bottom is left in the reduction reaction vessel and used in the next batch, the yield of high purity sponge titanium is affected. Absent. Then, by reducing the amount of removal of the attached titanium in the range excluding the range of 20% from the bottom with respect to the total height of the reduction reaction vessel, the load of the removal work can be reduced. In addition, since the adhered titanium remains in contact with the iron on the surface of the reduction reaction vessel and remains at a high temperature of 1000 ° C. or more for a long time in the vacuum separation process, the adhered titanium and the iron surface on the inner surface of the reduction reaction vessel form an alloy layer. And very strong adhesion. The adhered titanium forming these titanium-iron alloy layers is partly peeled off when the sponge lump is pushed out from the reduction reaction vessel, and at that time, part of the titanium-iron alloy layer and the base material are attached together with the adhered titanium. The container may peel off and the inner surface of the container may be consumed. In addition, a part of the adhered titanium forming the titanium-iron alloy layer remains adhered to the inner surface of the reduction reaction vessel, and when the adhered titanium is removed by suspending, a part of the titanium-iron alloy layer and the base material are adhered to the adhered titanium. They may peel off together and the inner surface of the container may be consumed. Therefore, leaving the adhered titanium without removing it suppresses the thinning of the inner surface of the container. In particular, Mg and TiCl ₄ react in the vicinity of the molten Mg liquid surface, so that a large amount of adhering titanium is generated on the inner surface of the reduction reaction vessel near the reaction liquid surface, and these adhering titaniums are near the liquid surface near the reaction field. Therefore, it is exposed to high temperature, and there is a tendency to increase the adhesion strength and the alloying with iron on the inner surface of the reduction reaction vessel compared to the lower part of the reduction reaction vessel. Therefore, by leaving the adhered titanium in the range excluding the range of 20% from the bottom of the total height of the reduction reaction vessel without removing it, or by reducing the amount of removed titanium, the inner surface of the reduction reaction vessel is reduced. Thinning can be suppressed, and the life of the reduction reaction vessel can be extended. It should be noted that it is preferable to exceptionally remove the adhered titanium having a thickness of more than about 20 mm, which disturbs the pushing-out of the titanium sponge lump in the next reduction reaction.

  In the present invention, it is a method for calculating the “exposure rate C”, but before removing the suspension, a photograph of the inner surface of the reduction reaction vessel and the surface of the rooster that is above the range of 20% from the bottom to the total height of the reduction reaction vessel. Shoot. At this time, the imaging range of one field of view is about 300 mm × 400 mm, the number of pixels is 1600 × 1200 pixels or more, and the inner surface of the reduction reaction vessel and the rooster of the reduction reaction vessel above the range of 20% from the bottom to the total height of the reduction reaction vessel. Shoot over the entire surface. Next, each obtained photograph is binarized using an image processing analysis device (manufactured by Luzex AP NIRECO), and then a portion where the background is exposed is selected to measure the area ratio. The area ratio is obtained by the formula “(X / (X + Y)) × 100”, where X is the area of the portion where the background is exposed, and Y is the area of the other portion. About each obtained photograph, an area rate was measured by the said method, and the average value of the area rate of all the photographs was set to the exposure rate C (%) (the upper part from the range of 20% from the bottom to the total height of the reduction reaction vessel). The ratio of the total area of the inner surface of the reduction reaction vessel and the surface of the rooster to the total area of the inner surface of the reduction reaction vessel and the surface of the rooster is exposed to the ground before removing the suspension.

  Further, in the present invention, the “exposure rate B” is calculated by the method of calculating the inner surface of the reduction reaction vessel and the surface of the rooster, which are above the range of 20% from the bottom with respect to the total height of the reduction reaction vessel after removing the suspension. Take a photo. At this time, the imaging range of one field of view is about 300 mm × 400 mm, the number of pixels is 1600 × 1200 pixels or more, and the inner surface of the reduction reaction vessel and the rooster of the reduction reaction vessel above the range of 20% from the bottom to the total height of the reduction reaction vessel. Shoot over the entire surface. Next, each obtained photograph is binarized using an image processing analysis device (manufactured by Luzex AP NIRECO), and then a portion where the background is exposed is selected to measure the area ratio. The area ratio is obtained by the formula “(X / (X + Y)) × 100”, where X is the area of the portion where the background is exposed, and Y is the area of the other portion. About each obtained photograph, an area rate was measured by the said method, and the average value of the area rate of all the photographs was set to exposure rate B (%) (from the range of 20% from the bottom to the total height of a reduction reaction container above the range of 20%. The ratio of the total area of the inner surface of the reduction reaction vessel and the surface of the rooster to the total area of the inner surface of the certain reduction reaction vessel and the surface of the rooster is removed).

  In the method for producing high-purity sponge titanium according to the present invention, the outlet of the melt of the reduction reaction vessel is located within a range of 5 to 20% from the bottom relative to the total height inside the reduction reaction vessel. This is preferable in that the amount of the melt remaining below can be reduced, or the possibility of clogging of the melt outlet is reduced.

  The method for producing high-purity sponge titanium according to the present invention is repeated using the same reduction reaction vessel until the deterioration of the reduction reaction vessel proceeds and cannot be used. Further, the high purity sponge titanium production method of the present invention is repeatedly performed using the same reduction reaction vessel until the inner wall is thinned, Ni elution occurs from the SUS side of the clad steel, and it cannot be used. Is called.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, this is merely an example and does not limit the present invention.

(Examples 1-4 and Comparative Examples 1-5)
After carrying out the reduction reaction under the production conditions of titanium sponge shown below, the generated sponge titanium lump is extracted, and the reduction reaction vessel after cooling is removed so that the exposure rate shown in Table 1 is obtained. went. At that time, the load for removing the suspension, the yield of high-purity sponge titanium when the titanium sponge was produced using the reduction reaction vessel, and the thickness reduction of the reduction reaction vessel were determined. The exposure rate D means that the background is exposed to the total area of the inner surface of the reduction reaction vessel and the surface of the rooster in the range of 20% from the bottom with respect to the total height inside the reduction reaction vessel before removing the suspension. It is the ratio of the total area of the inner surface of the reducing reaction vessel and the surface of the rooster.

<Production conditions for sponge titanium>
Weight of sponge titanium after vacuum separation: about 7 tons
Inner diameter of reaction vessel: φ1900mm
Raw material Mg charge: 12000kg
Magnesium and magnesium chloride extracted after the reduction reaction: 9500 kg
Temperature on the outer surface of the reaction vessel during vacuum separation: 1000 to 1050 ° C
Vacuum separation time: 130 hours

<Calculation method of yield of high purity sponge titanium>
Sponge titanium was produced using the reduction reaction vessel and rooster after removal of suspension, and the proportion of the collected amount of sponge titanium having a Ni content of 0.5 mass ppm or less with respect to the collected sponge titanium among the produced sponge titanium Was determined as the yield of high purity sponge titanium. Further, when the height of the sponge lump after removal is H and the diameter is D, the upper surface of the sponge lump is an upper portion from a position corresponding to 0.1 H from the upper end, and the lower surface is 0.1 H from the lower end. The remaining part obtained by cutting and removing the lower part from the position corresponding to 1 and the outer part from the position corresponding to 0.1D in the radial direction from the outer surface in the radial direction was taken as the collected sponge titanium part. The results are shown in Table 1. In Table 1, the yield of the high purity sponge titanium of Comparative Example 1 is 1, and the relative ratio is also described.
In addition, the collection method of sponge titanium with Ni content of 0.5 mass ppm or less is divided into about 30 kg of the collected sponge titanium portion collected by the above method, each Ni content is analyzed, Ni content is A section having an amount of 0.5 mass ppm or less was collected as high-purity titanium sponge.

<Calculation method of thinning amount of inner surface of reduction reaction container per cycle>
An ultrasonic flaw detector was used to measure the thickness of the inner surface of the reduction reaction vessel. In the range excluding the range of 20% from the bottom with respect to the total height inside the reduction reaction vessel, the measurement position is changed in the height direction and radial direction of the reduction reaction vessel, and the thickness of the inner surface of the reduction reaction vessel is measured, The average value was taken as the thickness of the inner surface of the reduction reaction vessel. In addition, the measurement positions were 14 places about every 250 mm in the height direction of the reduction reaction vessel, and 4 places every 90 degrees in the radial direction, for a total of 56 places.
Then, high purity sponge titanium with removal of hanger shown in Table 1 is manufactured, and from the thickness of the inner surface of the reduction reaction vessel before the high purity sponge titanium of the first batch is manufactured, By subtracting the thickness of the inner surface of the reduction reaction vessel after removing the suspension, the amount of thinning is obtained and divided by the number of batches used in the meantime, the amount of thinning of the inner surface of the reduction reaction vessel per batch Asked. In Table 1, the relative ratio is described assuming that the amount of thinning of the inner surface of the reduction reaction container per batch of Comparative Example 1 is 1.

<Calculation method of hanger removal work load>
The actual working time of the lifting work was defined as the time required for the lifting work. For example, in the case where the removal work is performed over a plurality of times, only the time during which the removal work is actually performed is totaled. In Table 1, the relative ratio is described with the time required for the lifting removal operation of Comparative Example 1 as 1.

Claims (2)

In the production of sponge titanium by the crawl method, after removing the suspended titanium adhering to the inner surface of the reduction reaction vessel and the surface of the rooster in the previous reduction reaction, removing the suspended reaction vessel A method for producing high-purity sponge titanium having a step of reusing and producing sponge titanium by a crawl method,
In the removal of the suspension, the background is exposed after the removal of the suspension with respect to the total area of the inner surface of the reduction reaction vessel and the surface of the rooster in a range of 20% from the bottom to the total height of the reduction reaction vessel. Removing the attached titanium so that the ratio of the total area of the inner surface of the reduction reaction vessel and the surface of the rooster (exposure rate A) is 70% or more,
A method for producing high-purity titanium sponge characterized by   2. The high purity sponge titanium according to claim 1, wherein the melt outlet of the reduction reaction vessel is located in a range of 5 to 20% from the bottom with respect to the total height inside the reduction reaction vessel. Production method.

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