WO2018179993A1

WO2018179993A1 - Titanium sponge, method for manufacturing titanium sponge, and method for manufacturing titanium ingot or titanium alloy ingot

Info

Publication number: WO2018179993A1
Application number: PCT/JP2018/005738
Authority: WO
Inventors: 洋介井上; 雅憲山口
Original assignee: 東邦チタニウム株式会社
Priority date: 2017-03-31
Filing date: 2018-02-19
Publication date: 2018-10-04
Also published as: JPWO2018179993A1; CN110462072A; US20210108287A1; CN110462072B; JP6621550B2

Abstract

Titanium sponge manufactured by the Kroll process, the titanium sponge characterized in that the total of the chlorine content and the magnesium content therein is 350 mass ppm and the bulk density thereof is 1.65-1.95 g/cm3. Through the present invention, it is possible to provide titanium sponge for manufacturing of a large-sized ingot in which the composition thereof can easily be controlled and problems due to chloride inclusion during smelting of a large-sized ingot by a melting method not involving compression molding do not readily occur, and a method for manufacturing the titanium sponge with high industrial efficiency.

Description

Method for producing sponge titanium and sponge titanium, and method for producing titanium ingot or titanium alloy ingot

The present invention relates to sponge titanium by a crawl method for producing sponge titanium by reducing titanium tetrachloride with metallic magnesium, a method for producing the same, and a method for producing a titanium ingot or a titanium alloy ingot.

Sponge titanium is industrially manufactured by the crawl method. Processes in the industrial production of sponge titanium by the crawl method are roughly divided into four steps, a chlorinated distillation step, a reduction separation step, a crushing step, and an electrolysis step.

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

The sponge titanium mass produced in this manner is cut and crushed step by step in the subsequent crushing process, and finally becomes sponge titanium of millimeter to centimeter order. Sponge titanium is melt | dissolved as a main raw material of a subsequent melt | dissolution process individually or with an auxiliary material, and turns into a titanium ingot or a titanium alloy ingot. The auxiliary material here refers to, for example, titanium scrap such as chips, plates and blocks of processed titanium products, and additives such as grains of other alloy elements, plates and blocks.

As a method for melting titanium, consumable electrode type arc melting method, electron beam melting method, plasma melting method, vacuum induction melting method, and inert induction melting method are generally used. It is known that the chlorine content of is an important factor that affects dissolution stability and productivity.

For example, in the electron beam melting method, melting is performed under vacuum, but in the case of sponge titanium having a large chlorine content, a lot of splash is generated due to the volatilization of chloride, and thus the dissolution yield deteriorates (Non-Patent Document 2) In some cases, the splash may adhere to or accumulate on the raw material supply port, which may make it impossible to insert the raw material (Patent Document 1). In addition, problems such as generation of an electron beam being inhibited by the volatilized chloride (Non-patent Document 3) and problems such as the generated chloride gas corroding the melting equipment also occur. Therefore, the lower the chlorine content, the better the dissolution stability. In the plasma melting method, the vacuum induction melting method, and the inert induction melting method, the same problems associated with the volatilization of chlorides occur, so the smaller the chlorine content of titanium sponge, the better.

Here, when referring to the chlorine content of a general sponge titanium, the chlorine content is about 700 ppm, and the magnesium content is about 250 ppm. It was low, and the chlorine content was 230 ppm and the magnesium content was 140 ppm (Non-patent Document 2).

Non-Patent Document 4 has a detailed description of the chlorine content of sponge titanium and its residual mechanism, and the distribution within the sponge titanium lump is about 1000 to 1500 ppm at the top of the lump and about 400 to 600 ppm at the bottom of the lump. There are three types of chlorine: Type 1: Magnesium chloride in fine pores in the titanium primary particles, Type 2: Magnesium chloride remaining between the titanium primary particles, Type 3: Titanium dichloride attached to the surface of the titanium primary particles, It has been reported that Type 2 is the main existence form. The titanium primary particles referred to here are titanium particles of the order of several tens μm constituting the sponge titanium, and the sponge titanium is a porous body in which the primary particles are sintered.

In Type 1, magnesium chloride is present in a very finely dispersed manner within the primary titanium particles. In Type 2, magnesium chloride is present in the gaps between the titanium primary particles. In Type 3, the surface of the titanium primary particles is present. Titanium dichloride is present on the top.

In Non-Patent Document 4, as an important factor governing the chlorine content, the supply rate of titanium tetrachloride and the amount of magnesium present in the reduction step are listed, the supply rate of titanium tetrachloride is small, and the amount of magnesium present is large. It is reported that the chlorine content is lower, and the supply rate of titanium tetrachloride is as small as 1.4 (L / m ² / min) (2.4 (kg / m ² / min)), and magnesium In the lower part of the sponge titanium lump produced in a state where there is abundantly present, it has succeeded in setting the chlorine content to less than 400 ppm.

By the way, the quality of the titanium ingot is an important factor in ingot melting, and the casting surface and components of the ingot are particularly important.

If the titanium content of the sponge titanium is high, troubles such as electron beam shifting or electron gun suspension may occur due to chloride during the melting process. The electron beam cannot be irradiated to the surface, which causes a defective casting surface.

As for the casting surface, there is a report example (non-patent document 2) on the relationship between the beam output and the pulling speed during melting of the electron beam and the casting surface.

Regarding the component, there is a report example (Non-patent Document 5) in which the component distribution of the ingot melted by the electron beam melting method is investigated. Particularly important in component control are oxygen concentration and iron concentration. In industrial pure titanium, it is required to control components within a narrow range of about 250 ppm.

Reality 6-23918

However, the chlorine content in the sponge titanium of Non-Patent Document 5 is slightly less than 400 ppm because it is not a sufficient chlorine reduction amount to solve the problem caused by the chloride content in the dissolution process, and therefore still contains the chloride content. There was a problem due to. In addition, the method of Non-Patent Document 5 has a problem that the productivity of titanium sponge is too low for industrialization because the supply rate of titanium tetrachloride is extremely slow.

Therefore, low chlorine content sponges that do not cause problems due to chloride content in melting methods that do not involve compression molding, such as electron beam melting, plasma melting, vacuum induction melting, and inert induction melting. There is a need for titanium.

Further, in the method of Non-Patent Document 2, although the casting surface can be improved at a small production level, when a large ingot of several tons or more is melted, even if the beam output and the pulling-down speed are appropriately controlled, the casting Skin defects often occur and improvements are sought.

Also, when a large ingot of several tons or more is melted, the components often cannot be controlled within a predetermined range, and improvement has been demanded.

Accordingly, the present invention provides a sponge titanium for manufacturing a large ingot that is difficult to cause problems due to the inclusion of chlorides and can be easily controlled when melting a large ingot by a melting method that does not involve compression molding. It aims at providing the method of manufacturing the said sponge titanium efficiently.

The above problems are solved by the present invention described below.
That is, the present invention (1) is a sponge titanium produced by a crawl method, the total of chlorine content and magnesium content is 350 mass ppm or less, and the packing density is 1.65 to 1.95 g / cm. ^The present invention provides a titanium sponge characterized by being ³ .

Also, the present invention (2) provides the sponge titanium according to (1), wherein the average particle diameter is 1.7 to 19.1 mm.

In the present invention (3), the ratio of fine sponge titanium particles having a particle diameter of 0.84 mm or less is 0.8% by mass or less, wherein the sponge titanium is either (1) or (2) It is to provide.

Further, the present invention (4) is a method for producing titanium sponge by a crawl method,
The reaction bath surface area is 2.5 m ² or more, and (i) titanium sponge is produced from the start of the supply of titanium tetrachloride to the metal magnesium to the position corresponding to the upper limit position of the sample to be collected in the crushing process. During the time, the following formula (1):
A = average feed rate of titanium tetrachloride per minute (kg / min) / area of reaction bath surface (m ² ) (1)
The average supply rate A of titanium tetrachloride per unit area of the reaction bath calculated in step 2.8 is 2.8 to 4.0 kg / (min · m ² ), and (ii) the total supply amount of titanium tetrachloride is The following formula (2):
B = mass of titanium sponge lump (t) / area of disk or pedestal with which the lower side of the titanium sponge lump contacts (m ² ) (2)
A reduction separation step in which the bottom load index B of the sponge titanium mass calculated in step 1 is 3.5 to 5.5 t / m ² ;
The upper limit position of the collection target is a position within the range of 40 to 50% on the mass basis from the bottom of the sponge titanium lump, and the sponge titanium lump below the upper limit position of the collection target is cut, crushed and Crushing to obtain sponge titanium,
Having
A method for producing titanium sponge by the crawl method is provided.

Further, the present invention (5) provides a method for producing a titanium ingot or a titanium alloy ingot characterized by using any of titanium sponges (1) to (3) as a melting raw material.

Further, the present invention (6) provides a method for producing a titanium ingot or a titanium alloy ingot characterized by using sponge titanium obtained by carrying out the method for producing sponge titanium of (4) as a melting raw material.

According to the present invention, when producing a large ingot by a melting method not involving compression molding, problems caused by the inclusion of chloride are unlikely to occur, and sponge titanium for producing a large ingot that is easy to control components and industrially A method for efficiently producing the titanium sponge can be provided.

It is a schematic diagram for demonstrating the presence form of chlorine in sponge titanium (porosity 40%). It is a schematic diagram for demonstrating the presence form of chlorine in sponge titanium (porosity 20%).

The sponge titanium of the present invention is a sponge titanium produced by a crawl method, wherein the total of the chlorine content and the magnesium content is 350 mass ppm or less, and the packing density is 1.65 to 1.95 g / cm ³ . It is a sponge titanium characterized by being.

In the industrial production of sponge titanium by the crawl method, the process mainly comprises a chlorodistillation process, a reduction separation process, a crushing process, and an electrolysis process. And the titanium sponge of the present invention is a titanium sponge produced by the crawl method, i.e., titanium tetrachloride is dropped on the molten magnesium, to reduce the titanium tetrachloride, to produce a titanium sponge lump, Vacuum separation separates by-product magnesium chloride and residual magnesium from the titanium sponge lump, and the sponge titanium lump obtained by performing the reductive separation step is cut, crushed and sieved to obtain desired particles. And a crushing step for obtaining a sponge titanium having a diameter. Hereinafter, the titanium sponge mass obtained by reducing titanium tetrachloride is also simply referred to as a titanium sponge mass.

The total of chlorine content and magnesium content in terms of atoms in the sponge titanium of the present invention is 350 mass ppm or less, preferably 300 mass ppm or less. When the total amount of chlorine and magnesium in terms of sponge titanium is in the above range, a large titanium ingot or a large titanium alloy ingot is melted by a melting method without compression molding. Problems caused by chloride are unlikely to occur, and an ingot having no defective casting surface can be produced efficiently. Hereinafter, large titanium ingots and large titanium alloy ingots are collectively referred to as large titanium ingots. In addition, the chlorine content and magnesium content in sponge titanium are calculated | required as follows. First, the sponge titanium to be measured is pulverized to form a sponge titanium lot. Next, according to JIS H 1610-2008 titanium and titanium alloy-sampling method, a large sample is sampled from each sponge titanium lot, and then the large sample is reduced to obtain four test samples having a mass of 250 g. Next, the chlorine content of the four test samples is measured by the silver nitrate titration method described in JIS H 1615-1997, and the average value of the four is the chlorine content of the sponge titanium lot. Further, the magnesium content of the four test samples is measured by the atomic absorption method described in JIS H 1616-1995, and the average value of the four is set as the magnesium content of the sponge titanium lot.

The packing density of the sponge titanium of the present invention is 1.65 to 1.95 g / cm ³ , preferably 1.70 to 1.95 g / cm ³ . Due to the packing density of sponge titanium being in the above range, when a large titanium ingot is melted by a melting method that does not involve compression molding, component deregulation occurs due to local concentration of components in the large titanium ingot. It can be made difficult, that is, component control can be facilitated. In the component standard for titanium ingots and titanium alloy ingots, the iron and oxygen content is required to be 250 ppm by mass or less. However, a large titanium ingot having a scale of several tons or more satisfies the standard over the entire length. Specifically, when three or five locations are analyzed from the bottom end portion to the top end portion, it is necessary to satisfy a predetermined component standard at all locations. However, the degree of difficulty is high, and only one bottom measurement value exceeds the upper limit value, or only one top measurement value exceeds the upper limit value. Often occurs. One factor contributing to the local concentration of the component is the presence of titanium sponge fine particles having a particle size of 0.84 mm or less. The titanium sponge fine particles present in the sponge titanium have an iron content higher than 10 times and an oxygen content higher than 2 times compared to the sponge titanium. Such sponge titanium fine particles are not a problem in the melting method that compresses and molds titanium raw materials like the consumable electrode arc melting method, but the melting method that does not involve compression molding of raw materials like the electron beam melting method However, when the raw material is supplied from the raw material supply facility, a phenomenon occurs in which the titanium sponge fine particles are supplied unevenly or the titanium sponge fine particles are locally deposited in the water-cooled copper hearth. When the grains are supplied unevenly or when the local deposits of titanium sponge fine particles are melted, the iron content and oxygen content in the large titanium ingot are locally increased, which is not within the component specifications of the titanium ingot. Connected.

In the conventional sponge titanium, even if the sponge titanium is sieved with a sieve of 0.84 mm or more, the sponge titanium is crushed in the mixing process after sieving. As a result, about 1.5 to 2.5% by mass of sponge is obtained. Titanium fine particles accompany sponge titanium. The sponge titanium fine particles produced by the crushing have a higher iron content and oxygen content than the sponge titanium as described above. Sponge titanium locally has a portion with a high iron or oxygen content, and a portion with a high iron or oxygen content is more easily crushed than a low portion. Sponge titanium granules having a high content and high oxygen content were likely to occur. Therefore, even if the sponge titanium fine particles are removed by sieving the sponge titanium, the titanium sponge fine particles having high iron content and oxygen content are generated in the subsequent process. Has a problem of local concentration of components in a large titanium ingot caused by sponge titanium fine particles having a high iron content and oxygen content. On the other hand, the titanium sponge of the present invention has a high packing density of 1.65 to 1.95 g / cm ³ , preferably 1.70 to 1.95 g / cm ^3, and therefore has a high bulk density. Even if a portion having a high iron or oxygen content is present locally in the sponge titanium of the present invention, the portion is difficult to break. Therefore, in the sponge titanium of the present invention, it is difficult to produce sponge titanium fine particles having a high iron content and oxygen content. Therefore, the local titanium in the large titanium ingot caused by the sponge titanium fine particles having a high iron content and oxygen content is used. The problem of general component concentration is less likely to occur, and the problem of local component deviation of the large titanium ingot is less likely to occur.

In addition, the packing density of sponge titanium is an index representing the bulk density of sponge titanium. In the present invention, the filling density refers to a density when titanium sponge is filled in a 200 L drum. Specifically, the packing density of the titanium sponge is determined as follows. A steel open drum type D / M class described in JIS Z 1600-2006 is used as a measuring container. First, the inner diameter D (cm) of the drum can and the inner height H (cm) (the distance from the upper surface of the drum bottom plate to the upper end of the drum can) are measured. Next, 100 kg or more of the titanium sponge to be measured is put into a drum can so that the upper surface of the sponge titanium becomes flat. Next, the distance from the upper end of the drum can to the upper surface of the sponge titanium is measured with a ruler. This measurement is performed at four points (0 °, 90 °, 180 °, 270 °) different in the radial direction in the drum, and the average value is defined as the distance C (cm) between the drum upper end and the sponge. Next, the packing density ρ (g / cm ³ ) is expressed by the following formula (3):
1 / ρ = V / M = (π / M) · (D / 2) ² · (HC) (3)
The inner diameter D (cm), the inner height H (cm), the drum top-sponge distance C (cm), and the titanium sponge mass M (g). Here, V (cm ³ ) is a filling volume of sponge titanium. Sponge titanium has a mean particle size in the range of 1.7 to 19.1 mm.

In the sponge titanium of the present invention, the proportion of fine sponge titanium particles having a particle size of 0.84 mm or less is 0.8 mass% or less, preferably 0.7 mass% or less, more preferably 0.4 mass% or less. . The ratio of the fine titanium sponge particles having a particle size of 0.84 mm or less in the titanium sponge is in the above range, so that the local content in the large titanium ingot caused by the fine titanium sponge particles having a high iron content and oxygen content is obtained. Therefore, it is difficult to cause a problem of component concentration, and a problem of local component deviation of a large titanium ingot hardly occurs. In the present invention, it is a method for measuring the proportion of sponge titanium fine particles having a particle size of 0.84 mm or less. The target particle size distribution is according to JIS H 2151: 2015 for sponge titanium sampled according to JIS H 1610: 2008. Measure and determine the proportion of titanium sponge fine particles having a particle size of 0.84 mm or less. In the present invention, sponge titanium having a particle size of 0.84 mm or less is defined as sponge titanium fine particles.

The average particle diameter of the sponge titanium of the present invention is 1.7 to 19.1 mm. In the present invention, it is a method for measuring the average particle diameter of titanium sponge, but the titanium sponge passed through a sieve having an opening of 19.1 mm or less and did not pass through a sieve having an opening of 1.7 mm or more. If it is, it is clear that the average particle diameter is in the range of 1.7 to 19.1 mm, so that the measurement can be omitted. When more accurate measurement is required, it is as follows. Measured by passing a plurality of sieves having different openings in accordance with JIS H 2151: 2015, targeting sponge titanium sampled according to JIS H 1610: 2008. Specifically, sieves having an opening of 1.7, 4.75, 12.7, 19.1, and 25.4 mm are used, and the mass percentage of the sponge titanium group that has passed through each sieve is measured. Thereafter, the particle size of the group of 1.7 mm or less is 0.85 mm, the group of 1.7 to 4.75 mm is 3.25 mm, the group of 4.75 to 12.7 mm is 8.73 mm, 12.7 to 19. The particle size of the 1 mm group is 15.9 mm, the particle size of the 19.1 to 25.4 mm group is 22.3 mm, and the weighted average value is the average particle size.

The porosity ε before pulverization of the sponge titanium of the present invention is 20 to 50%, preferably 20 to 40%. Due to the porosity of the sponge titanium being in the above range, the problem of local component concentration in the large titanium ingot caused by the sponge titanium fine particles having a high iron content and oxygen content hardly occurs, and the large titanium ingot. It becomes difficult to cause a problem of delocalization. In the present invention, it is determined as follows that the porosity ε before pulverization is in the above range. First, in the vicinity of the upper limit position of the collection target of the titanium sponge lump, the vicinity of the axis A1, the vicinity of the outer periphery B1, and the vicinity of the outer periphery B1 are the vicinity of the outer periphery C1 at a position shifted by 180 degrees about the axis. Take a sponge titanium sample with a mass of 100 to 300 g (diameter is about 50 to 150 mm) from a total of three locations, and measure the porosity of each sample by the measurement method described later. Is the porosity in the vicinity of the upper limit position. Next, in the vicinity of the lower limit position of the collection target of the titanium sponge lump, the vicinity of the axis A2, the vicinity of the outer periphery B2, and the vicinity of the outer periphery B2 are the vicinity of the outer periphery C2 at a position shifted by 180 degrees about the axis. Titanium sponge samples each having a mass of 100 to 300 g are collected from a total of three locations, and the porosity of each sample is measured by the measurement method described later, and the average value is taken as the porosity at the lower limit position. If both the porosity ε at the upper limit position of the sampling target and the porosity ε at the lower limit position of the sampling target are in the range of 20 to 50%, the porosity ε before pulverization of the sampling target is 20 to 50%. It is determined that it is in the range.

Further, the range of the porosity ε ′ after pulverization of the sponge titanium of the present invention is wider than the range of the porosity ε before pulverization, and becomes 5% to 50%. This is because, during the pulverization process, grains that have been extremely compressed to reduce the porosity and grains that have not been compressed and have not changed in porosity are mixed in the same lot. When determining the porosity ε ′ after pulverization, collect five or more sponge titanium particles larger than the average particle diameter, measure the porosity of each sample by the measurement method described later, and pulverize the average value. The porosity ε ′. The reason why sponge titanium particles larger than the average particle diameter are targeted is that it is difficult to accurately measure the porosity of a sample having an extremely small particle diameter by the measurement method described later.

Here, the method for measuring the porosity is explained. First, the mass W (g) of the sponge titanium sample is measured. Next, paraffin (Tissue-Tech paraffin wax) is heated to about 80 ° C. to 120 ° C. in a heat-resistant container and dissolved. Next, the sponge titanium sample is hung with a thread-like material and immersed in a paraffin solution. After confirming that bubbles are not generated, the sponge titanium sample is gently lifted and cooled while being suspended in the air. Next, a container filled with water is prepared and placed on a weighing machine. The cooled sponge titanium sample is gently dipped in water while being hung with a thread so as not to touch the container, and the amount of mass change (g) before and after dipping is recorded with a weigher. The apparent volume V (cm ³ ) of the titanium sponge sample is determined by dividing the mass change (g) by the density of water (g / cm ³ ). By dividing the mass W of the sponge titanium sample by the volume V, the bulk density ρ (g / cm ³ ) of the sponge titanium is obtained (ρ = W / V). From this bulk density ρ, the following formula (4):
Porosity (%) = (1− (ρ / 4.51)) × 100 (4)
Is used to determine the porosity (%).

Chlorine that exists as an impurity in sponge titanium exists as the following three types. Type 1 is chlorine existing as magnesium chloride in the fine pores in the titanium primary particles, Type 2 is chlorine existing as magnesium chloride remaining in the gap between the titanium primary particles, and Type 3 is on the surface of the titanium primary particles. Chlorine is present as adhering titanium dichloride. Of these, Type 2 is the main existence form. In the cross-sectional observation photograph of the sponge titanium sample shown in FIG. 1, Type 1 magnesium chloride 1 is scattered in the portion surrounded by the upper dotted line. Further, a portion surrounded by a solid line on the lower side in FIG. 1 is Type 2 magnesium chloride 2, and there are voids around the magnesium chloride. Further, the portion surrounded by the solid line on the lower side in FIG. 2 is Type 2 magnesium chloride 2, and this magnesium chloride is confined in the densely sintered titanium primary particles. In addition, the cross-sectional observation photograph of the sponge titanium sample shown in FIG.1 and FIG.2 is a schematic diagram.

As a result of intensive studies on the relationship between the residual amount of chlorine of these types and the process conditions and operations, the present inventors have found the following. As for the analysis of the presence of chlorine in the sponge titanium, the sponge titanium sample to be measured was filled with resin, polished with # 1000 emery paper, and then the cross section was analyzed with an electron beam microanalyzer (SUPERPROBE XXA-8100, Japan This was done by observing with an electronic company). At this time, in order to prevent the elution and moisture absorption of chloride in water, the work was performed quickly without touching water from cutting to polishing to observation.

As a result of a plurality of tests, the presence form of chlorine observed in the sponge titanium at the upper part of the sponge titanium lump obtained by performing the reduction and separation step is mostly Type 1, and chloride is encapsulated in the titanium particles. It was confirmed that it could not be volatilized and removed by vacuum separation because it was dispersed widely and finely. Therefore, it was found that the chlorine content in the upper part of the sponge titanium lump is as high as 1000-1500 mass ppm.

In contrast, the existence form observed in the sponge titanium at the lower part of the sponge titanium lump was mostly Type 2, and magnesium chloride remained in the gaps between the titanium primary particles. A part of Type 2 was completely confined in the sponge titanium by the close sintering of the titanium primary particles. A small amount of Type 1 was also observed. It has been found that the chlorine content in the lower part of the sponge titanium lump is about 400 to 600 mass ppm in combination of Type 2 and Type 1.

From these facts, it was found that it is important to reduce chlorine of Type 1 and Type 2 in order to reduce the chlorine content of sponge titanium.

As can be seen from the observation result of the upper part of the titanium sponge block, the amount of Type 1 is estimated to increase when the metal magnesium supply rate is insufficient with respect to the titanium tetrachloride supply rate at the reaction site. The metal magnesium supply rate here means that magnesium chloride by-produced on the reaction bath surface settles into the bath due to the difference in specific gravity, and instead the magnesium in the bath floats and is supplied to the reaction bath surface. Refers to speed. For this reason, in order to reduce Type 1 chlorine, it was estimated that it is important to appropriately control the ratio of the supply rate of titanium tetrachloride to the reaction site and the supply rate of magnesium metal.

As for Type 2, attention was paid to Type 2 magnesium chloride (hereinafter referred to as closed type 2) that was completely confined between the titanium primary particles by dense sintering of the titanium primary particles. “When the porosity of titanium is reduced to some extent, the occurrence frequency of closed type 2 increases.” “Even in the lower part of the sponge titanium lump, the closed type 2 generates a high chlorine content site with a chlorine content exceeding 1000 ppm by mass. I found something to do. And it turned out that the porosity (epsilon) is mainly controlled by the sintering of the titanium primary particles at the time of the vacuum separation of a reduction separation process. Therefore, in order to reduce the chlorine content, it has been estimated that it is effective to reduce the occurrence frequency of closed type 2 by not reducing the porosity of sponge titanium too much. On the other hand, in the large titanium ingot caused by the sponge titanium fine particles with high iron content and oxygen content, making the packing density high, making it difficult to locally break the part with high iron content and oxygen content In order to make it difficult for the local component concentration problem to occur, it is presumed that a smaller porosity is desirable.

From these facts, it was found that, for the reduction of Type 2, it is important to adjust the porosity of the sponge titanium to an appropriate range by appropriately controlling the sintering conditions of the titanium sponge. The inventors have found that if the compressive load becomes too large, the porosity of the sponge titanium becomes too small and the closed type 2 is likely to be generated, so that the compressive load needs to be in an appropriate range. It was.

Based on these findings, the present inventors have conceived the following method for producing sponge titanium according to the present invention.

The method for producing sponge titanium of the present invention is a method for producing sponge titanium by a crawl method,
The reaction bath surface area is 2.5 m ² or more, and (i) titanium sponge is produced from the start of the supply of titanium tetrachloride to the metal magnesium to the position corresponding to the upper limit position of the sample to be collected in the crushing process. During the time, the following formula (1):
A = average feed rate of titanium tetrachloride per minute (kg / min) / area of reaction bath surface (m ² ) (1)
The average supply rate A of titanium tetrachloride per unit area of the reaction bath calculated in step 2.8 is 2.8 to 4.0 kg / (min · m ² ), and (ii) the total supply amount of titanium tetrachloride is The following formula (2):
B = mass of titanium sponge lump (t) / area of disk or pedestal with which the lower side of the titanium sponge lump contacts (m ² ) (2)
A reduction separation step in which the bottom load index B of the sponge titanium mass calculated in step 1 is 3.5 to 5.5 t / m ² ;
The upper limit position of the collection target is a position within the range of 40 to 50% on the mass basis from the bottom of the sponge titanium lump, and the sponge titanium lump below the upper limit position of the collection target is cut, crushed and Crushing to obtain sponge titanium,
Having
It is the manufacturing method of sponge titanium by the crawl method characterized by these.

The method for producing sponge titanium according to the present invention is a method for producing titanium sponge by a crawl method. Titanium tetrachloride is dropped on molten metal magnesium, titanium tetrachloride is reduced to form a titanium sponge lump, The reduction separation process of removing magnesium chloride and residual magnesium as by-products from the sponge titanium lump by vacuum separation, and the sponge titanium lump is cut, crushed and sieved to obtain sponge titanium having a desired particle size. Crushing step.

In the reduction and separation step according to the method for producing titanium sponge of the present invention, first, titanium tetrachloride is supplied onto the metal magnesium bath in the reaction vessel, and the metal magnesium and titanium tetrachloride are reacted to reduce titanium tetrachloride. To do. At this time, the main reaction takes place on the reaction bath surface in the reaction vessel and the space above it, primary particles of titanium are generated, magnesium metal in the vicinity of the reaction bath surface is consumed, and magnesium chloride is a secondary agent. To be born. The produced titanium primary particles settle to the bottom of the reaction vessel and deposit on a disk or pedestal provided at the bottom of the reaction vessel. In addition, since the specific gravity of metallic magnesium is smaller than that of magnesium chloride, the by-produced magnesium chloride settles downward in the container, and instead, metallic magnesium rises. During the reduction reaction, the precipitated magnesium chloride is appropriately extracted from the bottom of the reaction vessel, but it is impossible to completely extract it, and after the reduction reaction, the remaining magnesium chloride and unreacted metallic magnesium are Both remain in the sponge titanium mass.

In the reduction separation step, the remaining magnesium chloride and unreacted metallic magnesium are then removed from the sponge titanium lump by vacuum separation. At this time, a reaction vessel containing the generated sponge titanium lump and an empty reaction vessel are disposed adjacent to each other, and the upper portions of both are connected by piping. Then, while heating the former reaction vessel from the outside, the inside of the latter reaction vessel is evacuated, so that the metallic magnesium and magnesium chloride contained in the sponge titanium mass in the former reaction vessel are exchanged between the upper portions of the reaction vessel. It is moved into an empty reaction vessel in a gas state through the connected piping. Note that the magnesium metal moved into the empty reaction vessel is used again for the reduction step.

In the method for producing sponge titanium according to the present invention, in the reduction separation step, when the area of the reaction bath surface is 2.5 m ² or more and titanium tetrachloride is supplied onto the metal magnesium bath, (i) metal magnesium During the generation of titanium sponge up to a position corresponding to the upper limit position of the object to be collected in the crushing process after starting the supply of titanium tetrachloride to the following formula (1):
A = average feed rate of titanium tetrachloride per minute (kg / min) / area of reaction bath surface (m ² ) (1)
The average feed rate A of titanium tetrachloride per unit area of the reaction bath calculated in step 2.8 is from 2.8 to 4.0 kg / (min · m ² ), preferably from 2.8 to 3.6 kg / (min · m ² ) to supply titanium tetrachloride onto the metal magnesium bath. Then, the area of the reaction bath surface is set to 2.5 m ² or more, and titanium titanium chloride is generated up to the position corresponding to the upper limit position of the collection target in the crushing process after the supply of titanium tetrachloride to the metal magnesium is started. The average feed rate A of titanium tetrachloride per unit area of the reaction bath is 2.8 to 4.0 kg / (min · m ² ), preferably 2.8 to 3.6 kg / (min. By making m ² ), the total of the chlorine content and the magnesium content of the sponge titanium can be 350 mass ppm or less, preferably 300 ppm or less.

In the method for producing sponge titanium according to the present invention, first, before supplying titanium tetrachloride to the reaction vessel, the upper limit position of the sample to be collected in the crushing step is set to a position on the mass basis from the bottom of the sponge titanium lump. The target to be collected in the crushing process when the titanium tetrachloride is supplied to the reaction vessel with the theoretical amount of titanium tetrachloride required to produce titanium sponge up to that position. The time point (mass basis) at which the sponge titanium is produced up to the upper limit position is grasped. For example, when the upper limit position of the collection target in the crushing process is set to 50% on the mass basis from the bottom of the sponge titanium lump, the supply in the crushing process is started after the supply of titanium tetrachloride to the metal magnesium is started. During the generation of titanium sponge up to the position corresponding to the upper limit position of the target, the supply of titanium tetrachloride to the molten metal magnesium is started, and then the titanium tetrachloride supplied to the reaction vessel The time until the supply of 50% by mass of titanium tetrachloride is completed. In addition, for example, when the upper limit position of the collection target in the crushing process is set to a position of 40% based on the mass from the bottom of the sponge titanium lump, the supply of titanium tetrachloride to the metal magnesium is started, and then the crushing process. During the generation of sponge titanium up to the position corresponding to the upper limit position of the sample to be collected, the supply of titanium tetrachloride to the molten metal magnesium is started, and then all the titanium tetrachloride supplied to the reaction vessel The time until the supply of 40% by mass of titanium tetrachloride is completed.

The feed rate of titanium tetrachloride per unit area of the reaction bath surface during the generation of sponge titanium at a position corresponding to the upper limit position of the sample to be collected in the crushing process is appropriately selected according to the production efficiency of the titanium sponge. However, it is generally selected in the range of 1.0 to 5.5 kg / (min · m ² ). Since the metal magnesium in the reaction vessel decreases as the reaction ends, the titanium tetrachloride supply rate is preferably set to a smaller value at the end of the reaction.

The area of the reaction bath surface is the area of the upper surface of the metallic magnesium in a molten state in the reaction vessel, and corresponds to the area of the horizontal cross section of the reaction vessel at the position of the upper surface of the metallic magnesium.

Furthermore, in the titanium sponge production method of the present invention, when supplying titanium tetrachloride to the metal magnesium bath in the reduction separation step, (ii) the total supply amount of titanium tetrachloride is expressed by the following formula (2):
B = mass of titanium sponge lump (t) / area of disk or pedestal with which the lower side of the titanium sponge lump contacts (m ² ) (2)
The bottom load index B of the titanium sponge lump calculated in (5) is 3.5 to 5.5 t / m ² , preferably 4.0 to 5.5 t / m ² . The total supply amount of titanium tetrachloride is adjusted so that the bottom load index B of the sponge titanium block is 3.5 to 5.5 t / m ² , preferably 4.0 to 5.5 t / m ^2. Since the porosity ε of the sponge titanium can be 20 to 50%, preferably 20 to 40%, the packing density of the sponge titanium is 1.65 to 1.95 g / cm ³ , preferably 1.70. Up to 1.95 g / cm ³ . When the bottom load index B of the titanium sponge mass obtained by performing the reduction separation process exceeds the above range, the compression load applied to the titanium sponge during vacuum separation increases, so the porosity decreases and the bulk density increases. Although the packing density becomes high, the compressive load applied to the sponge titanium is too large, so the porosity of the sponge titanium becomes too small, and the magnesium chloride of the closed type 2 increases, so the chlorine content of the sponge titanium Becomes higher. On the other hand, if the bottom load index B of the sponge titanium mass obtained by performing the reduction separation process is less than the above range, the compression load applied to the sponge titanium is too small at the time of vacuum separation, so the porosity becomes too large. The bulk density is less than the above range, and the packing density is less than the above range.

The area of the disc or pedestal with which the lower side of the sponge titanium mass contacts is the area of the disc when the pedestal and the disc placed on the pedestal are installed under the sponge titanium mass. It refers to the area of the upper surface, and when no pedestal is placed under the sponge titanium mass and only the pedestal is installed, it refers to the area of the upper surface of the pedestal. In addition, the mass of the titanium sponge lump when calculating the B value is a theoretical value calculated as if all of the titanium tetrachloride supplied into the reaction vessel was converted to titanium metal, This is a value calculated by multiplying the total number of moles of titanium tetrachloride supplied by the atomic weight of titanium.

Conditions other than those described above in the reduction reaction of the reduction separation process, for example, the temperature outside the reaction vessel during the reduction reaction may be any conditions that are usually used in the production of sponge titanium by the crawl method. 950 ° C.

The vacuum heating temperature in the vacuum separation in the reduction separation step is not particularly limited, but is preferably 900 to 1080 ° C. Moreover, the vacuum heating time in the vacuum separation in the reduction separation step is not particularly limited, and a time for removing magnesium chloride and metal magnesium capable of volatile separation is appropriately selected. Note that, as described above, Type 1 and closed Type 2 chlorine exists so as to be confined in the sponge titanium, and thus is not removed even if the vacuum heating time is increased. For this reason, if the vacuum heating time is unnecessarily prolonged, time and energy are wasted. Therefore, the vacuum heating time may be any time for removing magnesium chloride and metal magnesium capable of volatile separation. The vacuum heating time in the vacuum separation in the reduction separation step is p (hour) as the vacuum heating time, and r (mm) as the radius of the disk or pedestal with which the lower part of the sponge titanium lump contacts (where r is 600 mm or more). )), A range satisfying “112 ≦ 0.26 × rp ≦ 125” is preferable in that vacuum separation can be performed without wasting time and power. When the disk or pedestal upper surface is a perfect circle, the radius is r, and when it is an ellipse, the average value of the maximum diameter and the minimum diameter is r.

In the crushing step according to the method for producing titanium sponge of the present invention, the upper limit position of the collection target is set to a position within the range of 40 to 50% on the mass basis from the bottom of the sponge titanium lump, and the lower position from the upper limit position of the collection target. The sponge titanium lump is cut, crushed and sieved as a sample to be collected to obtain sponge titanium. The upper limit position of the collection target in the crushing process is a position determined as the upper limit position of the collection target in the crushing process before supplying titanium tetrachloride to the reaction vessel. Note that the position of X% on the mass basis from the bottom of the sponge titanium lump means that when the titanium at the same height is accumulated vertically from the bottom of the sponge titanium lump, the accumulated mass is the total mass of the sponge titanium lump. Is a position where X%. The collection target site in the present invention may be a part within the range, for example, 5% to 30%, 20 to 35%, as long as it is within the range below the upper limit position.

In the crushing step, the titanium sponge block obtained by performing the reduction and separation step is taken out from the reaction vessel by a known punching device, cut and crushed into a round shape with a known large press, and divided into parts. Furthermore, the coarsely crushed small-sized sponge titanium is pulverized to 100 mm or less with a known shear or the like to obtain sponge titanium. At this time, the sponge titanium lump existing below the position determined as the upper limit position of the collection target is cut, pulverized, and sieved as the collection target. Then, the upper limit position of the collection target is set within a range of 40 to 50% based on the mass from the bottom of the titanium sponge lump, and the sponge titanium lump existing below the upper limit position of the collection target is cut, crushed and sieved. As a result, sponge titanium having a packing density of 1.65 to 1.95 g / cm ³ , preferably 1.70 to 1.95 g / cm ³ can be obtained, and the Type 1 chlorine content is large. Therefore, avoiding the upper side of the sponge titanium lump that tends to increase the chlorine content, the lower side of the sponge titanium lump with a small content of Type 1 and a low chlorine content is targeted for collection. The chlorine content of can be reduced.

In addition, the vicinity of the lower end of the sponge titanium mass obtained by performing the reduction and separation process is sponge titanium produced in the initial stage of the reaction, and iron, nitrogen, aluminum, nickel in the metal magnesium used as a raw material is concentrated, and the general sponge titanium In the crushing process, the titanium sponge in the vicinity of the lower end of the sponge titanium mass obtained by performing the reduction and separation process is not taken as a sampling target. In the crushing process, the percentage of the position below the sponge titanium lump that is the lower limit position of the sponge titanium collection target is appropriately selected depending on the chlorine content and the magnesium content in the sponge titanium. It is preferable that the position of 2 to 8% on the basis of mass from the bottom of the lump is the lower limit position of the collection target of sponge titanium, and the position of 2 to 5% on the basis of mass from the bottom of the sponge titanium lump is set to sponge titanium. It is particularly preferable to set the lower limit position of the sampling target.

The sponge titanium obtained by carrying out the method for producing the sponge titanium of the present invention and the sponge titanium of the present invention has a very low chloride content. Therefore, in the dissolution method not involving compression molding, the splash accompanying the volatilization of chloride is not present. It occurs frequently, the dissolution yield deteriorates, the splash adheres to or deposits on the raw material supply port, the raw material cannot be inserted, and the generation of the electron beam is inhibited by the volatile chloride. Occurrence of problems caused by the inclusion of chloride such as corrosion of the dissolved chloride gas by the melting equipment can be prevented. In addition, since the sponge titanium obtained by carrying out the method for producing the sponge titanium according to the present invention and the sponge titanium according to the present invention has a very low chloride content, in the melting method not involving compression molding, there is a problem of poor casting surface. Occurrence can be prevented. The sponge titanium of the present invention and the sponge titanium obtained by carrying out the method for producing the sponge titanium of the present invention have a packing density of 1.65 to 1.95 g / cm ³ , preferably 1.70 to 1.95 g / cm ^3. So, it can prevent the problem of local component concentration in large titanium ingots caused by sponge titanium fine particles with high iron content and oxygen content, which are generated by breaking parts with high iron content and oxygen content. It is possible to prevent the problem of local component deviation of the large titanium ingot.

In the method for producing sponge titanium according to the present invention, the range of the collection target of titanium sponge in the crushing step is 40% to 50% lower than the bottom of the titanium sponge lump, and the reduction reaction. Sometimes, the supply rate of titanium tetrachloride when producing sponge titanium in the range to be collected is 2.8 to 4.0 kg / (min · m ² ), preferably 2.8 to 3.6 kg. / (Min · m ² ) and the area of the reaction bath surface is 2.5 m ² or more, adjusting the total supply amount of titanium tetrachloride during the reduction reaction, 3.5 to 5.5 t / m ² , preferably 4.0 to 5.5 t / m ² , and the porosity of the portion to be collected of the sponge titanium mass is set to 20 to 50%, preferably 20 to 40%. Of chlorine content and magnesium content Total 350 mass ppm or less, preferably 300 ppm by mass or less, and the packing density is 1.65 ~ 1.95g / cm ^3, preferably it is possible to obtain a titanium sponge 1.70 ~ 1.95g / cm ³ .

The method for producing a titanium ingot or titanium alloy ingot according to the first aspect of the present invention is a method for producing a titanium ingot or titanium alloy ingot characterized by using the sponge titanium of the present invention as a melting raw material. The titanium ingot or titanium alloy ingot according to the second aspect of the present invention is a titanium ingot or titanium alloy characterized by using sponge titanium obtained by performing the method for producing sponge titanium according to the present invention as a melting raw material. It is a manufacturing method of an ingot.

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.

Example 1
The standard production amount of titanium sponge per one time is 8.0 tons, the cross-sectional area of the reaction bath surface portion is 2.5 (m ² ), and the radius r of the disk is 750 (mm). Sponge titanium was manufactured using a manufacturing apparatus.
First, 10 t of molten magnesium was put in the production apparatus, and titanium tetrachloride was supplied thereto to carry out a reduction reaction of titanium tetrachloride. At this time, regarding the supply of titanium tetrachloride of 0 to 16 (t), which corresponds to the first 50% of the total supply amount of titanium tetrachloride 32 (t), the average of titanium tetrachloride per unit area of the reaction bath surface The supply rate A was controlled to be 3.3 (kg / (min · m ² )), and then 16 to 32 (t) of titanium tetrachloride corresponding to the second half 50% was supplied. The bottom load index B is 4.5 (t / m ² ).
Next, vacuum separation was performed to obtain a sponge titanium lump. At this time, vacuum heating was performed under such conditions that the vacuum heating temperature was 1050 ° C. and the vacuum heating time p (hour) was 0.26 × rp = 122.
Subsequently, the obtained titanium sponge lump was sequentially cut from below. First, 400 kg corresponding to 5% of 8.0 tons on mass basis with poor quality was excised from below the sponge titanium lump. Next, 3.6 tons corresponding to 5 to 50% of 8.0 tons on a mass basis were collected separately from other parts of the sponge titanium lump. At this time, a sponge titanium sample having a mass of 100 to 300 g is placed in the vicinity of the upper limit position of the sponge titanium lump to be collected, and the vicinity of the axis A1, the vicinity of the outer periphery B1, and the vicinity of the outer periphery B1 are 180 around the axis. Three points were collected from the outer peripheral vicinity C1 of the position shifted by a degree, and the porosity of each sponge titanium was obtained, and the average porosity was found to be 47% before crushing at the upper limit position of the sampled object. there were. Further, from the vicinity of the lower limit position of the collection target of the titanium sponge mass, the vicinity of the axis A2, the vicinity of the outer periphery B2, and the vicinity of the outer periphery B2 from the vicinity of the outer periphery C2 at a position shifted by 180 degrees about the axis. Three points were collected, the porosity of each sponge titanium was determined, and the porosity was averaged. As a result, the porosity ε before pulverization at the lower limit position of the sample was 23%.
Next, sponge titanium other than the sample for which the porosity was measured was pulverized with a shear or the like and sieved to a sieve having an opening of 19.1 mm or less and a sieve having an opening of 0.84 mm or more. Homogenization gave sponge titanium A.
Next, when the chlorine content, the magnesium content, and the packing density of the sponge titanium A were measured, the chlorine content was 200 ppm by mass, the magnesium content was 90 ppm by mass, and the packing density was 1.70 g / cm ³ . . Moreover, 0.2 mass% was contained for the fine granule of 0.84 mm or less. In addition, 5 points larger than 1.27 mm were randomly sampled from sponge titanium A and the porosity was determined and averaged. As a result, the porosity ε ′ after pulverization was 25%. Table 1 shows the results.

(Example 2, Comparative Examples 1 and 2)
Example 1 except that the section for managing the average supply rate of titanium tetrachloride per unit area to 3.3 (kg / (min · m ² ) and the site to be collected for sponge titanium are within the ranges shown in Table 1. The results are shown in Table 1.

As can be seen from Table 1, the site to be collected is lowered from the position of 50% on the basis of the mass from the bottom of the sponge titanium mass, so that the chloride content is 290 mass ppm or less and the packing density is 1.70 g / cm ³ or more.

(Examples 3 and 4, Comparative Example 3)
The average supply rate of titanium tetrachloride per unit area of the reaction bath surface in the first half 50% of the total supply amount of titanium tetrachloride 32 (t) in the first 50% interval is shown in Table 2. The procedure was the same as in Example 1 except that. The results are shown in Table 2.

(Comparative Example 4)
The standard production amount of titanium sponge per time is 6.0 tons, the cross-sectional area of the reaction bath surface portion is 2.2 (m ² ), and the radius r of the disc is 700 (mm). Sponge titanium was manufactured using a manufacturing apparatus.
First, 7.5 t of molten magnesium was put in the production apparatus, and titanium tetrachloride was supplied thereto to carry out a reduction reaction of titanium tetrachloride. At this time, for the supply of 0 to 12 (t) of titanium tetrachloride, which corresponds to the first 50% of the total supply of titanium tetrachloride, 24 (t), the average of titanium tetrachloride per unit area of the reaction bath surface The feed rate A was controlled to be 2.8 (kg / (min · m ² )), and then 12 to 24 (t) of titanium tetrachloride corresponding to the second half 50% section was fed. The bottom load index B is 4.0 (t / m ² ).
Next, vacuum separation was performed to obtain a sponge titanium lump. At this time, vacuum heating was performed under such conditions that the vacuum heating temperature was 1050 ° C. and the vacuum heating time p (hour) was 0.26 × rp = 120.
Thereafter, the same method as in Example 1 was performed. The results are shown in Table 1.

As can be seen from Table 2, the average supply rate of titanium tetrachloride per unit area of the reaction bath surface is 4.0 (kg / (min · m ² )) or less in the first 50% of the total supply amount of titanium tetrachloride. By suppressing to chlorine, chlorine content can be suppressed to 330 mass ppm or less.

Further, as can be seen from the comparison between Example 3 and Comparative Example 4 in Table 2, even when the average feed rate of titanium tetrachloride per unit area of the reaction bath is the same, the area of the reaction bath is 2.5 (m ^When less than ² ), the chlorine content increases.

(Examples 6 and 7, Comparative Examples 5 and 6)
In Example 6 and Comparative Example 5, the total supply amount of titanium tetrachloride was set to the value shown in Table 3, and the same procedure as in Example 1 was performed except that the bottom load index was changed.
In Example 7 and Comparative Example 6, the standard amount of sponge titanium produced per one time was 12.0 tons, the vessel cross-sectional area of the reaction bath surface portion was 3.5 (m ² ), and the radius of the disk The bottom load index was changed with the production of titanium sponge using an 8.0-ton batch production apparatus with r of 800 mm and the total supply of titanium tetrachloride as the values shown in Table 3. Except for this, the method was performed in the same manner as in Example 1.

As can be seen from Table 3, by controlling the bottom load index and controlling the porosity of the collection target site to be in the range of 20 to 50%, the chlorine content is 290 mass ppm or less and the packing density is 1.65 to 1. 90 g / cm ³ can be achieved. On the other hand, in Comparative Example 6 in which the porosity is lower than 20%, although the packing density can achieve a very high value of 2.00 g / cm ³ , the chlorine content is extremely high at over 1400 mass ppm, which is not suitable. .

(Examples 8 and 9, Comparative Examples 7 and 8)
Using Example 2, Example 5, Comparative Example 1 and Comparative Example 2 and sponge titanium produced by the same method as the raw material, four 10t JIS Class 1 titanium ingots were produced by the electron beam melting method. The amount of splash deposits, the number of times the electron gun was suspended, and the production rate of titanium ingots were investigated. As for the amount of splash deposited, the thickness of the splash deposited on the end of the water-cooled copper hearth was observed from the observation window of the melting furnace, and the case of Example 2 was set as 1. The production rate of the titanium ingot is calculated by dividing the mass of the titanium ingot by the time from the introduction of the titanium raw material into the melting furnace until the flow of the molten titanium into the mold is completed. As a relative comparison. In addition, the cast skin and components of the melted ingot were also evaluated. The casting surface is the number of casting surface defects with a depth of 5 mm or more on the surface of the ingot, and the component is the process of iron and oxygen concentration when the ingot is divided equally into 5 parts from the bottom end to the top end. The ability index Cpk was compared. Cpk was calculated by the following formula (1). Here, USL is a standard upper limit value, LSL is a standard lower limit value, μ is an average value, and σ is a standard deviation.

As can be seen from Table 4, by using sponge titanium having a chlorine content of 330 mass ppm or less and a packing density of 1.65 g / cm ³ or more as a melting raw material, the amount of splash deposition, the number of electron gun pauses, ingot production Improvements can be seen not only in the index related to the melting cost such as the speed but also in the index related to the quality of the ingot such as cast skin, iron and oxygen Cpk.

Claims

Sponge titanium manufactured by the crawl method, wherein the total of chlorine content and magnesium content is 350 ppm by mass or less, and the packing density is 1.65 to 1.95 g / cm 3 titanium.
2. The sponge titanium according to claim 1, wherein the average particle size is 1.7 to 19.1 mm.
3. The sponge titanium according to claim 1, wherein the proportion of titanium sponge fine particles having a particle size of 0.84 mm or less is 0.8 mass% or less.
A method for producing sponge titanium by a crawl method,
The reaction bath surface area is 2.5 m 2 or more, and (i) titanium sponge is produced from the start of the supply of titanium tetrachloride to the metal magnesium to the position corresponding to the upper limit position of the sample to be collected in the crushing process. During the time, the following formula (1):
A = average feed rate of titanium tetrachloride per minute (kg / min) / area of reaction bath surface (m 2 ) (1)
The average supply rate A of titanium tetrachloride per unit area of the reaction bath calculated in step 2.8 is 2.8 to 4.0 kg / (min · m 2 ), and (ii) the total supply amount of titanium tetrachloride is The following formula (2):
B = mass of titanium sponge lump (t) / area of disk or pedestal with which the lower side of the titanium sponge lump contacts (m 2 ) (2)
A reduction separation step in which the bottom load index B of the sponge titanium mass calculated in step 1 is 3.5 to 5.5 t / m 2 ;
The upper limit position of the collection target is a position within the range of 40 to 50% on the mass basis from the bottom of the sponge titanium lump, and the sponge titanium lump below the upper limit position of the collection target is cut, crushed and Crushing to obtain sponge titanium,
Having
A method for producing titanium sponge by a crawl method.
A method for producing a titanium ingot or a titanium alloy ingot, wherein the sponge titanium according to any one of claims 1 to 3 is used as a melting raw material.
A method for producing a titanium ingot or a titanium alloy ingot, characterized in that the titanium sponge obtained by carrying out the method for producing a titanium sponge according to claim 4 is used as a melting raw material.