JP2019100645A - Vacuum heating device, and method for producing high melting point metallic body - Google Patents

Abstract

To produce a high melting point metallic body having high purity.SOLUTION: A vacuum heating device comprises a vacuum vessel, an exhaust mechanism, a stage and a pedestal. The exhaust mechanism exhausts gas in the vacuum vessel. The stage is provided at the inside of the vacuum vessel. The pedestal is mounted on the stage. The pedestal can support a high melting point metallic oxide and a carbon-containing molded body. The pedestal includes: an upper edge part to be contacted with the molded body; and a lower edge part to be contacted with the stage. In the pedestal, a first space part is formed in a space with the molded body by contacting the upper edge part with the molded body, and a second space part is formed in a space with the stage by contacting the lower edge part with the stage. The heating mechanism heats the molded body.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a vacuum heating apparatus and a method of manufacturing a refractory metal body.

  A carbon reduction method is known as a method of extracting a high melting point metal from a metal oxide containing a high melting point metal such as tantalum (see, for example, Non-Patent Document 1). For example, a compact containing tantalum oxide and graphite is placed in a plasma arc furnace, and the compact is exposed to a plasma torch of several thousand degrees or more to obtain a high melting point metal body from the compact. However, the plasma arc method is not excellent in mass productivity because the area of the molded body exposed to the plasma torch is limited.

  On the other hand, there is vacuum heat treatment as another method for heat treatment of a molded body to several thousand degrees or more (see, for example, Patent Document 1). The vacuum heat treatment allows a relatively large compact to be installed in the vacuum vessel, so that the amount of compact which can be reduced by carbon at one time increases, and the mass productivity is excellent. And in such a vacuum heating process, it becomes important how to efficiently promote carbon reduction of a molded object and to obtain a high purity high melting point metal body.

Patent No. 4023774

Japan Mining Journal / 96 1105 ('80 -3) 165 <45> -170 <54>

  In view of the above circumstances, an object of the present invention is to provide a vacuum heating apparatus and a method for producing a high melting point metal body, which produce a high purity high melting point metal body by carbon reduction.

In order to achieve the above object, a vacuum heating apparatus according to an aspect of the present invention includes a vacuum vessel, an exhaust mechanism, a stage, a pedestal, and a heating mechanism. The exhaust mechanism exhausts the gas in the vacuum vessel. The stage is provided in the vacuum vessel. The pedestal is mounted on the stage. The pedestal is capable of supporting a shaped body containing refractory metal oxide and carbon. The pedestal has an upper end in contact with the molded body and a lower end in contact with the stage. The pedestal has a first space formed between the upper end portion and the molded body when the upper end portion contacts the molded body, and a second space between the lower end portion and the stage when the lower end portion contacts the stage. A space is formed. The heating mechanism heats the molded body.
With such a vacuum heating device, the pedestal supports the compact containing the refractory metal oxide and carbon, and when the compact is heated by the heating mechanism, the heat diffusion from the compact to the stage is suppressed. The high melting point metal oxide is efficiently carbon reduced to the high melting point metal.

In the above-mentioned vacuum heating device, the above-mentioned heating mechanism may have a pair of heater boards which sandwich the above-mentioned stage and are mutually opposed.
With such a vacuum heating device, the compact is uniformly heated from the left and right by the pair of heater plates, and the refractory metal oxide is efficiently carbon-reduced to the refractory metal.

In the above-described vacuum heating apparatus, the pedestal may be horizontally extended and contracted, and the height may change according to the horizontal extension and contraction.
With such a vacuum heating apparatus, the degree of heat conduction from the compact to the stage through the pedestal can be adjusted according to the height of the pedestal, so that the heat diffusion from the compact to the stage can be suppressed. The high melting point metal oxide is efficiently carbon reduced to the high melting point metal.

In the above-described vacuum heating apparatus, the cross-sectional shape in the horizontal direction of the pedestal may be configured in a stripe shape.
With such a vacuum heating device, the thermal diffusion from the compact to the stage through the pedestal is suppressed, so the refractory metal oxide is efficiently carbon-reduced to the refractory metal.

In the above-described vacuum heating device, the pedestal may have a height of 4 mm or more.
With such a vacuum heating device, the thermal diffusion from the compact to the stage through the pedestal is suppressed, so the refractory metal oxide is efficiently carbon-reduced to the refractory metal.

The pedestal may be made of the same material as the refractory metal contained in the refractory metal oxide.
In such a vacuum heating apparatus, since the refractory metal and the pedestal are made of the same material, it is difficult for impurities to enter the refractory metal body formed by carbon reduction from the pedestal.

The upper end portion of the pedestal may be made of the same material as the refractory metal contained in the refractory metal oxide.
With such a vacuum heating apparatus, since the refractory metal and the upper end portion of the pedestal are made of the same material, it is difficult for impurities from the pedestal to enter the refractory metal body formed by carbon reduction.

In the above vacuum heating apparatus, the stage may include a carbon sheet in contact with the pedestal.
In such a vacuum heating apparatus, since the carbon sheet is interposed between the pedestal and the stage, a direct reaction between the pedestal and the stage can be suppressed.

In order to achieve the above object, a vacuum heating apparatus according to an aspect of the present invention includes a vacuum vessel, an exhaust mechanism, a stage, a pedestal, and a heating mechanism. The exhaust mechanism exhausts the gas in the vacuum vessel. The stage is provided in the vacuum vessel. The pedestal is mounted on the stage. The pedestal is capable of supporting a shaped body containing refractory metal oxide and carbon. The pedestal has an upper end in contact with the molded body and a lower end in contact with the stage. With the pedestal, the upper end portion is in contact with the molded body, and the lower end portion is in contact with the stage, thereby forming a space portion communicating the molded body with the stage. The heating mechanism heats the molded body.
With such a vacuum heating device, the pedestal supports the compact containing the refractory metal oxide and carbon, and when the compact is heated by the heating mechanism, the heat diffusion from the compact to the stage is suppressed. The high melting point metal oxide is efficiently carbon reduced to the high melting point metal.

The cross-sectional shape of the pedestal in the horizontal direction may be any one of a honeycomb shape, a lattice shape, and a circular shape.
With such a vacuum heating device, the thermal diffusion from the compact to the stage through the pedestal is suppressed, so the refractory metal oxide is efficiently carbon-reduced to the refractory metal.

In order to achieve the above object, a method of manufacturing a high melting point metal body according to an aspect of the present invention can support a molded body containing high melting point metal oxide and carbon on a stage provided in a vacuum vessel. An upper end in contact with the molded product, and a lower end in contact with the stage, and the upper end is in contact with the molded product to form a first space between the molded product and the molded product; The mounting of the pedestal in which the second space portion is formed between the lower end portion and the stage by contacting the lower end portion. The molded body is supported by the pedestal. The inside of the vacuum vessel is heated by the heating mechanism while being evacuated by the exhaust mechanism. The refractory metal oxide is carbon-reduced to form a refractory metal body.
In such a method, the pedestal supports the compact containing the refractory metal oxide and carbon, and when the compact is heated by the heating mechanism, the thermal diffusion from the compact to the stage is suppressed. The high melting point metal oxide is efficiently carbon reduced to the high melting point metal.

  As described above, according to the present invention, carbon reduction produces a high-purity refractory metal body.

It is a schematic sectional drawing of the vacuum heating apparatus which concerns on this embodiment. Figure (a) is a schematic cross-sectional view of the pedestal. Figure (b) is a schematic top view of the pedestal. It is a schematic sectional drawing which shows an example of the flow of the heat which moves to a stage from a molded object through a base. It is a schematic graph which shows an example of operation | movement of the vacuum heating apparatus which concerns on this embodiment. Figure (a) is the result of X-ray diffraction of the tantalum metal body formed by the vacuum heat treatment according to the comparative example. FIG. (B) is the result of X-ray diffraction of the tantalum metal body formed by the vacuum heat treatment according to the present embodiment. FIG. (C) is a schematic bottom view of a tantalum metal body subjected to carbon reduction. The figure (d) is a schematic sectional view in a dashed line of a figure (c). The figures (a) and (b) are schematic cross-sectional views of modifications of the pedestal. The figures (a) and (b) are schematic cross-sectional views of another modified example of the pedestal. The figures (a) to (c) are schematic perspective views of another modified example of the pedestal.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing, XYZ axis coordinates may be introduced.

  FIG. 1 is a schematic cross-sectional view of a vacuum heating apparatus according to the present embodiment. The vacuum heating device 1 shown in FIG. 1 is an example and is not limited to this example.

  The vacuum heating apparatus 1 includes a vacuum vessel 10, a leg 11, a base 12, an exhaust mechanism 20, a stage 30, a pedestal 40A, a heating mechanism 50, a heat insulating member 60, and a gas supply mechanism 80. Do. In the example of FIG. 1, the state in which the molded object 100 was mounted on the base 40A is shown. In this state, the molded body 100 is in a state before being heated.

  The vacuum vessel 10 encloses the base 12, the stage 30, the pedestal 40 A, the heating mechanism 50, the heat insulating member 60, and the molded body 100. The vacuum vessel 10 is, for example, a cylindrical vacuum vessel and extends in the X-axis direction. In the vacuum heating device 1, a door (not shown) which is a part of the vacuum vessel 10 is disposed at the front and back of FIG. 1, and the gas in the vacuum vessel 10 is exhausted by the exhaust mechanism 20. Thus, the inside of the vacuum vessel 10 is maintained in a reduced pressure state. The exhaust mechanism 20 includes, for example, a vacuum pump such as a rotary pump or a mechanical booster pump. The vacuum vessel 10 is supported by the legs 11. The substrate 12 is fixed in the vacuum vessel 10 and disposed under the heat insulating member 60. The base 12 also functions as a heat insulating material.

  In the vacuum vessel 10, a heat insulating member 60 is provided. The heat insulating member 60 is fixed to the inner wall 10 w of the vacuum vessel 10 by a fixing jig 65. The heat insulating member 60 surrounds a part of the stage 30, the pedestal 40A, a part of the heating mechanism 50, and the molded body 100. The inside of the heat insulating member 60 is not sealed from the outside of the heat insulating member 60, and in the vacuum vessel 10, gas can flow between the inside and the outside of the heat insulating member 60.

  The heat insulating member 60 has a lower heat insulating member 61, side heat insulating members 62a and 62b, and an upper heat insulating member 63. The lower heat insulating member 61 is disposed in parallel to the XY plane. The lower heat insulating member 61 faces the upper heat insulating member 63 in the Z-axis direction. The side heat insulating member 62a and the side heat insulating member 62b face each other in the Y-axis direction. Each of lower heat insulating member 61, side heat insulating members 62a and 62b, and upper heat insulating member 63 extends in the X-axis direction. In the vacuum vessel 10, a heat insulating member may be disposed in front of and behind the molded body 100.

  A part of the stage 30 is provided in the heat insulating member 60. The stage 30 includes a stage body 31, a plurality of columns 33, a carbon plate 32, and a carbon sheet 34. The stage body 31 and the support 33 are made of, for example, a carbon material. The carbon plate 32 and the carbon sheet 34 may be removed from the stage 30 as appropriate.

  Each of the plurality of columns 33 penetrates the lower heat insulating member 61, for example, and is erected vertically to the base 12. The stage main body 31 is supported by a plurality of columns 33 (for example, four-point support). Thereby, the stage main body 31 is arrange | positioned in parallel with respect to a XY plane. Furthermore, the stage 30 is configured such that the stage main body 31 is not in direct contact with the lower heat insulating member 61.

  The carbon plate 32 is mounted on the stage main body 31. The stage main body 31 and the carbon plate 32 extend in the X-axis direction in the heat insulating member 60. For example, when the stage main body 31 and the carbon plate 32 are viewed from the Z-axis direction, the planar shapes of the stage main body 31 and the carbon plate 32 are, for example, rectangular.

  By disposing the lower heat insulating member 61 under the stage main body 31, when the molded body 100 is heated by the heating mechanism 50, the heat given to the molded body 100 is less likely to escape to the vacuum vessel 10. Further, the carbon plate 32 has a small coefficient of linear expansion and is excellent in heat resistance characteristics. By arranging such a carbon plate 32 on the stage main body 31, the stage main body 31 is less likely to be directly damaged from the molded body 100 and the pedestal 40A, and is stable over a wide area of the molded body 100 and the pedestal 40A. Can be supported.

  Further, by disposing the carbon sheet 34 between the pedestal 40A and the carbon plate 32, direct reaction between the pedestal 40A and the carbon plate 32 is suppressed even if the pedestal 40A reaches a high temperature of several thousand degrees or more. Be In this case, even if the pedestal 40A reacts with the carbon sheet 34, corrosion of the carbon plate 32 due to metal reaction is avoided by periodically replacing the carbon sheet 34.

  A pedestal 40A is mounted on the stage 30. The details of the pedestal 40A will be described later.

  The molded body 100 is placed on the pedestal 40A. Molded body 100 contains a refractory metal oxide and carbon. The molded body 100 is a pellet or a block formed by mixing a powder of a high melting point metal oxide and a powder of carbon and molding it by a high pressure press. The refractory metal is, for example, any of Ta (tantalum), W (tungsten), Mo (molybdenum), Nb (niobium), titanium (Ti) and the like. In the present embodiment, Ta is exemplified below as the high melting point metal.

For example, the molded body 100 contains tantalum oxide (for example, Ta ₂ O ₅ ) and carbon (C). The molded body 100 is, for example, a powder of tantalum oxide having an average particle diameter of 25 μm and a powder of carbon having an average particle diameter of 15 μm, which are pressure-formed at a pressure of 40 MPa.

The molar concentration (mol / m ³ ) of carbon in the compact 100 is about 5 times the molar concentration of tantalum oxide. The average particle size is measured, for example, by laser scattering. The shape of the molded body 100 is, for example, a pellet of 10 mm in thickness and 30 mm in diameter. The shape of the molded body 100 is not limited to the pellet body, and may be, for example, a block body having a side of 10 mm to 100 mm.

  Although one molded body 100 is supported by the pedestal 40A in FIG. 1, a plurality of pedestals 40A are disposed in the X-axis direction or the Y-axis direction, and the molded body 100 is mounted on these pedestals 40A. The pedestal 40A may be placed on the molded body 100, and another molded body 100 may be placed on the pedestal 40A.

  The heating mechanism 50 heats the molded body 100 by radiant heat. The heating mechanism 50 has a first heating mechanism 51 and a second heating mechanism 52.

  The first heating mechanism 51 has a heater plate 51 a and an insulating support jig 51 b. The support jig 51 b is fixed to the inner wall 10 w of the vacuum vessel 10 and penetrates the upper heat insulating member 63. The support jig 51 b supports the heater plate 51 a and is provided with a wire for supplying power to the heater plate 51 a from the outside of the vacuum vessel 10. The heater plate 51 a extends in the X-axis direction and in the direction from the upper heat insulating member 63 toward the lower heat insulating member 61. The heater plate 51a is not in contact with the side heat insulation member 62a, and is disposed in parallel with the side heat insulation member 62a.

  The second heating mechanism 52 has a heater plate 52a and an insulating support jig 52b. The support jig 52 b is fixed to the inner wall 10 w of the vacuum vessel 10 and penetrates the upper heat insulating member 63. The support jig 52 b supports the heater plate 52 a and is provided with a wire for supplying power to the heater plate 52 a from the outside of the vacuum vessel 10. The heater plate 52 a extends in the X-axis direction and in the direction from the upper heat insulating member 63 toward the lower heat insulating member 61. The heater plate 52a is not in contact with the side heat insulation member 62b, and is disposed in parallel with the side heat insulation member 62b.

  The pair of heater plates 51a, 52a facing each other is a heater made of carbon. The lower ends of the heater plates 51 a and 52 a are located below the stage main body 31. Thereby, the molded object 100 is equally heated from the left and right by the radiant heat from the heater boards 51a and 52a. For example, the molded body 100 can be heated to 1900 ° C. or higher.

  The heater plate may be disposed above the compact 100 or may be disposed in front of or behind the compact 100. Thereby, heat can be more uniformly applied to the compact 100 from the side and the top.

  On the other hand, in the vacuum heating apparatus 1, since mass production of a high melting point metal body utilizing carbon reduction is assumed, the number of the compacts 100 is not limited to one, and the weight of the compact on the stage 30 is It may be bulky. For this reason, in the vacuum heating device 1, a strong stage 30 for supporting the molded body 100 is essential.

  Therefore, the stage 30 is disposed below the molded body 100, and the heater plate is not disposed. Here, there is also a method of arranging a heater plate under the stage main body 31. However, in this configuration, the radiation heat from the heater plate is blocked by the stage main body 31. Furthermore, when the heater plate is disposed below the stage main body 31, the heater plate needs to be disposed avoiding the columns 33, and the structure of the heater plate disposed below the stage main body 31 becomes complicated.

  The temperature of the molded body 100 is obtained by, for example, finding in advance the relation between the electric power supplied to the heater plates 51a and 52a and the temperature of the molded body 100, the relation between the temperature of the heater plates 51a and 52a and the temperature of the molded body 100, etc. Calculated by The temperature of the heater plates 51a, 52a may be measured by a thermocouple, or the temperature of the molded body 100 may be measured directly by a radiation thermometer. In addition, a sample for temperature measurement which indirectly measures the temperature of the molded body 100 may be placed in the vicinity of the molded body 100.

The gas supply mechanism 80 can supply a gas such as N ₂ or Ar into the vacuum vessel 10. For example, after heating of the molded body 100 is completed and the molded body 100 is cooled to a predetermined temperature, a gas for purge (for example, N ₂ ) is supplied into the vacuum vessel 10 by the gas supply mechanism 80.

  FIG. 2A is a schematic cross-sectional view of a pedestal. FIG. 2 (b) is a schematic top view of the pedestal.

  The pedestal 40A is, for example, configured to have a triangular waveform in cross section. The pedestal 40A has a first plate-like portion 41 parallel to the first direction (for example, a direction between the Y-axis direction and the Z-axis direction) and a second direction (line-symmetrical to the first direction) intersecting the first direction. And the second plate-like portions 42 parallel to each other are alternately connected. The thickness of the first plate-like portion 41 and the second plate-like portion 42 is typically 0.5 mm or more.

  In the pedestal 40A, the upper end 40u faces the molded body 100, and the lower end 40d opposite to the upper end 40u faces the stage 30. For example, the upper end 40 u is in contact with the molded body 100, and the lower end 40 d is in contact with the stage 30.

  In the pedestal 40A configured of such a plate-like portion, the heat conduction path from the upper end 40u to the lower end 40d is narrowed, and heat applied to the molded body 100 is less likely to escape to the stage 30 via the pedestal 40A. .

  FIG. 3 is a schematic cross-sectional view showing an example of the flow of heat moving from the molded body to the stage via the pedestal.

  The cross-sectional shape when the pedestal 40A is cut along the XY plane is configured in a stripe shape. Thereby, pedestal 40A contacts with molding 100 and stage 30 not by surface contact but by line contact. If the molded body 100 is placed directly on the carbon sheet 34 without providing the pedestal 40A, heat is transferred from the molded body 100 to the carbon sheet 34, and the temperature of the bottom of the molded body 100 is lowered. In addition, CO gas generated by the reaction is less likely to escape from the molded body 100. The present embodiment solves such problems.

  For example, the upper end 40 u located at the center of the heat transfer to the stage 30 will be described as an example. The heat conducted from the molded body 100 to the upper end portion 40 u is split into a fork between the first plate-like portion 41 and the second plate-like portion 42. The heat conducted from the upper end 40u to the first plate 41 is partially dissipated to the stage 30 through the lower end 40d, but conducted to the second plate 42 and returned to the molded body 100. There is also. Similarly, although the heat conducted from the upper end 40u to the second plate-like portion 42 partially escapes to the stage 30 through the lower end 40d, the heat is conducted to the first plate-like portion 41 and the molded body 100 side There is also a fever back.

  Therefore, by using the pedestal 40A, the heat conduction from the molded body 100 to the stage 30 can be suppressed as much as possible, and the molded body 100 can be sufficiently heated. Thus, the molded body 100 is efficiently heated by the heating mechanism 50.

  When the molded body 100 is placed on the pedestal 40A, the upper end 40u comes in contact with the molded body 100, and a space portion 410 (first space portion) is formed between the molded body 100 and the molded body 100. When the pedestal 40A is placed on the stage 30, the lower end 40d contacts the stage 30, and a space 420 (second space) is formed between the lower end 40d and the stage 30. Here, the height h of the pedestal 40A is set to be equal to or greater than the mean free path of the gas in the vacuum vessel 10 when carbon reduction occurs in the molded body 100.

  For example, the height h of the pedestal 40A is set to 4 mm or more. The height h of the pedestal 40A can be prepared by changing the pitch of the upper end 40u and the lower end 40d in the Y-axis direction. Thereby, the depth of the space portion 410 becomes about 4 mm or more, the heat conduction by the gas between the green body 100 and the stage 30 is suppressed, and the green body 100 is efficiently heated by the heating mechanism 50. For example, assuming that the temperature of the molded body 100 is T1 and the temperature of the stage 30 (carbon sheet 34) is T2 (T1> T2), the distance h between the molded body 100 and the stage 30 becomes longer than the mean free path λ (λ << h), the heat flux q in the steady state can be expressed, for example, by q = k (T1-T2) / d (k: thermal conductivity of gas), and the heat flux q becomes larger as the spacing h becomes larger. It is thought that it reduces.

  The pedestal 40A is made of the same material as the refractory metal contained in the refractory metal oxide of the molded body 100. As a result, even if the refractory metal oxide in the molded body 100 becomes a refractory metal body by carbon reduction, it becomes difficult for impurities other than the refractory metal to enter the refractory metal body from the pedestal 40A.

Next, one example of a method of manufacturing the refractory metal body according to the present embodiment will be described by taking the pedestal 40A as an example.
FIG. 4 is a schematic graph showing an example of the operation of the vacuum heating apparatus according to the present embodiment.
The horizontal axis in FIG. 4 is time, the right vertical axis is the pressure in the vacuum vessel 10, and the left vertical axis is the temperature of the molded body 100.

  In the vacuum heating process according to the present embodiment, the pedestal 40A is placed on the stage 30 provided in the vacuum vessel 10 in advance. Subsequently, the molded body 100 is supported on the pedestal 40A.

  Next, the inside of the vacuum vessel 10 is evacuated to several Pa (for example, 2 Pa) by the exhaust mechanism 20, and the molded body 100 is heated by the heating mechanism 50 at a rate of, for example, 10 ° C./min while evacuation is performed. Thereby, the temperature of the molded object 100 rises gradually.

  The pressure in the vacuum vessel 10 is such that the gas physically adsorbed on the inner wall 10w of the vacuum vessel 10, the stage 30, the heat insulating member 60, the compact 100, etc. is removed until the temperature of the compact 100 changes from room temperature to 600.degree. The gas rises and rises once to 2 Pa or more. As the degassing relaxes, the pressure in the vacuum vessel 10 decreases again.

  The temperature rising heating to the formed body 100 is continued, and after the temperature of the formed body 100 reaches 1935 ° C., the temperature rising heating is stopped and the temperature of the formed body 100 is maintained at 1935 ° C. for 60 minutes. In the molded body 100, carbon reduction occurs when the temperature is about 1800 ° C. or more, and, for example, tantalum oxide is reduced by carbon to form tantalum (Ta) and carbon monoxide (CO). Thereby, the pressure in the vacuum vessel 10 rises again. During carbon reduction, the pressure in the vacuum vessel 10 is, for example, 2 Pa or more and 10 Pa or less. Carbon monoxide is exhausted out of the vacuum vessel 10 by the exhaust mechanism 20.

  When the carbon in the compact 100 is consumed by carbon reduction, the amount of carbon in the compact 100 is reduced, and the release of carbon monoxide from the compact 100 is gradually alleviated. In response to this, the pressure in the vacuum vessel 10 decreases, and when the pressure drop in the vacuum vessel 10 is saturated, the heating to the molded body 100 is stopped.

After the temperature of the molded body 100 becomes 25 ° C. or lower, the inside of the vacuum vessel 10 is purged with, for example, N ₂ gas several times. Thereafter, the vacuum vessel 10 is opened to the atmosphere, and the tantalum metal body from which the tantalum oxide is carbon reduced is taken out from the vacuum vessel 10. The removed tantalum metal body is transferred, for example, to another vacuum vessel and melted by EB (Electron Beam) irradiation to form a tantalum metal ingot. The tantalum metal ingot is cut out, for example, as a tantalum target on which a tantalum film is sputter-deposited.

  The effects of this embodiment will be described.

  FIG. 5A is a result of X-ray diffraction of a tantalum metal body formed by vacuum heat treatment according to a comparative example. FIG. 5 (b) is the result of X-ray diffraction of the tantalum metal body formed by the vacuum heat treatment according to the present embodiment. FIG. 5C is a schematic bottom view of a tantalum metal body subjected to carbon reduction. FIG. 5D is a schematic cross-sectional view taken along a broken line in FIG.

  X-ray diffraction is by the θ-2θ method. The horizontal axis of the graph is 2θ (°), and the vertical axis is light intensity (arbitrary value). The object to be measured is a tantalum metal body (a pellet of 10 mm in thickness and 30 mm in diameter) subjected to carbon reduction. The solid line A is the result of X-ray diffraction of the end portion Pa of the tantalum metal body shown in FIGS. 5 (c) and 5 (d). The broken line B is the result of X-ray diffraction of the lower central portion Pb of the tantalum metal body shown in FIGS. 5 (c) and 5 (d).

  In the comparative example shown in FIG. 5A, a pedestal in which two tantalum fine wires are arranged in parallel is used. The diameter of the tantalum wire is 2 mm. That is, the height of the tantalum parallel thin line is 2 mm, and the distance between the green body 100 and the stage 30 is 2 mm.

In the comparative example, the peaks of Ta ₂ O ₅ and Ta ₂ C are not observed at the end Pa of the tantalum metal body, but the peaks of Ta are observed. However, although a peak of Ta was observed at the lower central part Pb of the tantalum metal body, peaks of Ta ₂ O ₅ and Ta ₂ C were also observed. The following can be considered as the reason.

  For example, when the height of the pedestal is smaller than 4 mm, the gas remaining in the vacuum vessel 10 is likely to be accumulated between the molded body 100 and the stage 30. As a result, the gas existing between the compact 100 and the stage 30 is likely to be the heat medium, in addition to the tantalum fine wire.

Therefore, even if heat is applied to the compact 100 by the heating mechanism 50, this heat escapes to the stage 30 through the tantalum thin wire and the gas existing between the compact 100 and the stage 30. Thereby, in the comparative example, it is assumed that the heating of the lower central part of the molded body 100 becomes insufficient and the carbon reduction in the lower central part Pb of the tantalum metal body becomes insufficient. When the distance between the green body 100 and the stage 30 is changed using tantalum fine wires having different diameters, Ta ₂ O ₅ and Ta ₂ are obtained when the distance between the green body 100 and the stage 30 is 3 mm or less. The peak of C is observed.

On the other hand, in the present embodiment, as shown in FIG. 5B, the peaks of Ta ₂ O ₅ and Ta ₂ C are not observed at the end Pa and the lower central part Pb of the tantalum metal body. The peak of Ta is observed.

  That is, in the present embodiment, the height of the pedestal 40A is 4 mm or more, the gas is less likely to be a heat medium between the molded body 100 and the stage 30, and the entire molded body 100 is sufficiently heated by the heating mechanism 50. . As a result, carbon reduction proceeds sufficiently in the entire molded body 100.

For example, even if the temperature of the molded body 100 is lowered from 1935 ° C. to 1875 ° C. by using the pedestal 40A, the peaks related to Ta ₂ O ₅ and Ta ₂ C at the end Pa of the tantalum metal body and the lower central portion Pb Not observed, it is known that carbon reduction sufficiently proceeds at the end portion Pa of the tantalum metal body and the lower central portion Pb even at a temperature of 1875 ° C.

  As described above, according to the vacuum heating apparatus 1 according to the present embodiment, the thermal diffusion from the molded body 100 to the stage 30 via the pedestal 40A is suppressed, and the refractory metal oxide is efficiently carbonized to the refractory metal It is reduced. Thus, a high-purity refractory metal body is formed from the refractory metal oxide.

  For example, in a tantalum metal body, C (carbon), Al (aluminum), Co (cobalt), Cr (Cr), Cu (copper), Fe (iron), Mg (magnesium), Mo (molybdenum), Nb (niobium) And the total concentration of Ni (nickel) is 50 ppm or less.

  Fig.6 (a) and FIG.6 (b) are schematic sectional drawings of the modification of a base.

  The pedestal 40B can be expanded and contracted in the horizontal direction, and its height changes in accordance with the expansion and contraction in the horizontal direction. The horizontal direction is a direction parallel to the X-Y plane. The pedestal 40B includes a first plate-like portion 41, a second plate-like portion 42, a base shaft portion 43, and tightening jigs 44a and 44b. The base shaft portion 43 penetrates the first plate-like portion 41 and the second plate-like portion 42. For example, screw threads are provided on the outer periphery of the base shaft portion 43, and screw grooves corresponding to the screw threads of the base shaft portion 43 are provided on the inner peripheries of the tightening jigs 44a and 44b. The first plate-like portion 41 and the second plate-like portion 42 may be connected by a hinge mechanism.

  For example, FIG. 6A shows a state after each of the fastening jigs 44a and 44b is fitted to both ends of the base shaft portion 43. As shown in FIG. In this state, the pedestal 40B has a height h1. As shown in FIG. 6 (b), by tightening the tightening jigs 44a and 44b and narrowing the distance between the tightening jigs 44a and 44b, the first plate-like portion 41 and the second plate-like portion 42 The angle formed is small. As a result, the pedestal 40B shrinks in the Y-axis direction, and the height of the pedestal 40B becomes h2 higher than the height h1.

  With such a pedestal 40B, the amount of heat conducted from the molded body 100 to the stage 30 via the pedestal 40B can be adjusted according to the height of the pedestal 40B. Thereby, the thermal diffusion from the molded body 100 to the stage 30 is suppressed.

  Further, in the pedestal 40B, the outermost first plate-like portion 41 is in contact with the tightening jig 44a, and is in contact with the outermost second plate-like portion 42 and the tightening jig 44b. Thereby, even if a heavy molded body is placed on the upper end portion 40u, the outermost first plate-like portion 41 is stopped by the tightening jig 44a, and the outermost second plate-like portion 42 is the tightening jig Stopped by 44b. That is, even if the weight of the molded body 100 is increased, the pedestal 40B is unlikely to be crushed.

  Further, in the pedestal 40B, the pitch of the adjacent upper end portions 40u is configured to be variable. Thereby, the molded object 100 can be stably supported by the pedestal 40B by changing the pitch of the upper end 40u according to the width of the molded object 100.

  Fig.7 (a) and FIG.7 (b) are schematic sectional drawings of another modification of a base.

  In the pedestal 40C shown in FIG. 7A, the upper end 40u is made of the same material as the refractory metal contained in the refractory metal oxide. For example, in the pedestal 40C, the recess 45 is formed in the portion where the first plate-like portion 41 and the second plate-like portion 42 intersect, and the Ta piece 46 is supported in the recess 45. Further, in the pedestal 40D shown in FIG. 7B, the thin Ta wire 47 is placed in the recess 45.

  With such pedestals 40C and 40D, since the refractory metal and the upper end 40u of the pedestal are made of the same material, it is difficult for impurities from the pedestals 40C and 40D to enter the refractory metal.

  Fig.8 (a)-FIG.8 (c) are schematic perspective views of another modification of a base. The pedestal shown below has the same height as the pedestal 40A.

  In the pedestal 40E shown in FIG. 8A, the upper end 40u is in contact with the molded body 100, and the lower end 40d is in contact with the stage 30, so that a space 430 communicating the molded body 100 and the stage 30 with each other. Is formed. The cross-sectional shape of the pedestal 40E in the X-Y plane is circular.

  In the pedestal 40F shown in FIG. 8B, the upper end 40u is in contact with the molded body 100, and the lower end 40d is in contact with the stage 30, so that a space 440 communicating between the molded body 100 and the stage 30. Is formed. The cross-sectional shape in the XY plane of the pedestal 40F is lattice-like.

  In pedestal 40G shown in FIG. 8C, upper end portion 40u comes in contact with molded body 100, and lower end portion 40d comes in contact with stage 30, and a space portion 450 that allows communication between molded body 100 and stage 30. Is formed. The cross-sectional shape in the XY plane of the pedestal 40G is a honeycomb shape.

  Even when these pedestals are used, the thermal diffusion from the molded body 100 to the stage 30 via the pedestals is suppressed, and the refractory metal oxide is efficiently carbon reduced to the refractory metal.

  As mentioned above, although embodiment of this invention was described, this invention is not limited only to the above-mentioned embodiment, of course, a various change can be added.

DESCRIPTION OF SYMBOLS 1 ... Vacuum heating apparatus 10 ... Vacuum vessel 10w ... Inner wall 11 ... Leg part 12 ... Base | substrate 20 ... Exhaust mechanism 30 ... Stage 31 ... Stage main body 32 ... Carbon plate 33 ... Post 34 ... Carbon sheet 40A, 40B, 40C, 40D, 40E , 40F, 40G ... pedestal 40d ... lower end 40u ... upper end 41 ... first plate-like portion 42 ... second plate-like portion 410, 420, 430, 440, 450 ... space portion 43 ... basic shaft portion 44a, 44b ... tightening Jig 45: Recess 46: Ta small piece 47: Ta thin line 50: Heating mechanism 51: First heating mechanism 52: Second heating mechanism 51a, 52a: Heater plate 51b, 52b: Support jig 60: Heat insulation member 61: Lower heat insulation member 62a , 62b ... side heat insulating member 63 ... upper heat insulating member 65 ... fixing jig 80 ... gas supply mechanism 100 ... molded body

Claims (11)

With a vacuum vessel,
An exhaust mechanism for exhausting the gas in the vacuum vessel;
A stage provided in the vacuum vessel;
It is mounted on the stage and can support a molded body containing a refractory metal oxide and carbon, and has an upper end in contact with the molded body and a lower end in contact with the stage, the upper end being A pedestal in which a first space portion is formed between the molded body and the molded body by contacting the molded body, and a second space portion is formed between the lower end portion and the stage by contacting the stage ,
And a heating mechanism for heating the molded body. The vacuum heating apparatus according to claim 1, wherein
The heating mechanism includes a pair of heater plates that sandwich the stage and face each other. The vacuum heating apparatus according to claim 1 or 2, wherein
The pedestal is horizontally extendable and retractable, and its height changes according to the extension and contraction in the horizontal direction. Vacuum heating apparatus. The vacuum heating apparatus according to any one of claims 1 to 3, wherein
The cross-sectional shape in the horizontal direction of the said base is comprised by stripe shape. Vacuum heating apparatus. The vacuum heating apparatus according to any one of claims 1 to 4, wherein
The pedestal has a height of 4 mm or more. The vacuum heating apparatus according to any one of claims 1 to 5, wherein
The base is made of the same material as the refractory metal contained in the refractory metal oxide. Vacuum heating apparatus. The vacuum heating device according to any one of claims 1 to 6, wherein
The said upper end part of the said base is comprised with the same material as the refractory metal contained in the said refractory metal oxide. Vacuum heating apparatus. The vacuum heating device according to any one of claims 1 to 7, wherein
The stage includes a carbon sheet in contact with the pedestal. With a vacuum vessel,
An exhaust mechanism for exhausting the gas in the vacuum vessel;
A stage provided in the vacuum vessel;
It is mounted on the stage and can support a molded body containing a refractory metal oxide and carbon, and has an upper end in contact with the molded body and a lower end in contact with the stage, the upper end being A pedestal which is in contact with the molded body and the lower end portion is in contact with the stage to form a space communicating between the molded body and the stage;
And a heating mechanism for heating the molded body. The vacuum heating apparatus according to claim 9, wherein
The cross-sectional shape in the horizontal direction of the pedestal is configured in any one of a honeycomb shape, a lattice shape, and a circular shape. Vacuum heating device. A molded body containing refractory metal oxide and carbon can be supported on a stage provided in a vacuum vessel, and has an upper end in contact with the molded body and a lower end in contact with the stage, A first space portion is formed between the upper end portion and the molded body by being in contact with the molded body, and a second space portion is formed between the lower end portion and the stage by being in contact with the stage. Place the pedestal to be
Causing the pedestal to support the molded body,
While the inside of the vacuum vessel is evacuated by an exhaust mechanism, the compact is heated by a heating mechanism;
The method for producing a high melting point metal body, wherein the high melting point metal oxide is reduced by carbon to form a high melting point metal body.

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