KR102373916B1 - Polycrystalline tungsten sintered compact, polycrystalline tungsten alloy sintered compact, and method for manufacturing same - Google Patents

Abstract

Raw material powder composed of W particles, or raw material powder obtained by blending W particle powder with one or more alloy component particles selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and Mn, or its The green compact is charged in a pressure sintering apparatus and sintered in a temperature range of 1200° C. or higher and lower than or equal to the melting point in a state in which a pressing force of 2.55 GPa or more and 13 GPa or less is applied. Polycrystalline W sintered compact and polycrystalline W alloy sintered compact having a high density, fine grain structure and no anisotropy having a pore ratio of 0.2 area% or less, an average grain size of 50 µm or less, and an average aspect ratio of grains of 1 to 2.5 measured in .

Description

Polycrystalline tungsten sintered compact, polycrystalline tungsten alloy sintered compact, and manufacturing method thereof

The present invention relates to a polycrystalline tungsten sintered compact having high density and high isotropy, a polycrystalline tungsten alloy sintered compact, and a method for manufacturing the same.

This application claims priority based on Japanese Patent Application No. 2015-60039 for which it applied to Japan on March 23, 2015 and Japanese Patent Application No. 2016-051244 for which it applied to Japan on March 15, 2016, The content is cited here.

Polycrystalline tungsten and polycrystalline tungsten alloy are used in many fields, for example, a non-consumable electrode for welding, a target material, an X-ray shielding material, a corrosion-resistant material, etc. are used. In general, polycrystalline tungsten and polycrystalline tungsten alloys are required to have high strength, hardness, and high specific gravity.

As a conventionally known use and manufacturing method of polycrystalline tungsten and polycrystalline tungsten alloy, what is shown to the following patent documents 1-4 is mentioned, for example.

In Patent Document 1, an electrode for fusing welding in which heating and pressing are repeatedly applied, in order to suppress detachment and wear and tear at the tip and to increase durability stably, an electrode body made of Cu or a Cu alloy. As the electrode core material of a dual structure electrode in which an electrode core material based on W or Mo or an alloy based on them is mounted at the tip of It is proposed to use W or Mo having a fibrous structure extending in the axial direction so as to be 50 µm or more and an aspect ratio of 1.5 or more, or an alloy based on them as an electrode material for fusing welding.

In Patent Document 2, the refining effect of molybdenum, tungsten, or a high-purity, high-melting-point metal or alloy containing these as a main component is enhanced, and the material's functionality (superconductivity, corrosion resistance, high-temperature heat resistance, etc.) and workability (forgeability, rollability, machinability, etc.) ) in order to significantly improve Preliminarily press-molding a powder or small lump raw material of one or two or more additional elements selected in Forms of low-order compounds or non-stoichiometric compounds (a form of an additive element or impurity metal and an impurity gas component, or a compound that maintains a fixed composition between metals under conditions of high pressure and high temperature) It has been proposed to volatilize and purify various impurities contained in the furnace lysate at once to enhance the effect of removing impurities.

In Patent Document 3, in order to increase the durability of the electrode and also to improve the impact resistance and fracture resistance of the electrode, a sintered alloy of either tungsten and molybdenum in which a fibrous structure is formed by rolling constitutes an electrode material for resistance welding, The electrode for resistance welding which made the cross section of the fibrous structure of this electrode material into the welding surface which pinches a workpiece|work is proposed.

Moreover, in patent document 4, for the purpose of densification of the sputtering target material used for a flat display and lengthening of life, 30-70 wt% tungsten as a sputtering target material, and the molybdenum-tungsten alloy which balance consists of molybdenum is used as a sputtering target material. In order to make the relative density of this alloy 96% to 99.9%, the molybdenum-tungsten powder of a predetermined composition is subjected to a combination of press molding using a predetermined press pressure and sintering under predetermined sintering conditions to achieve a relative density of 93% It is proposed that density increase can be attained by making a sintered compact which has - 94.5 %, and then rolling or forging at a heating temperature of 1400-1600 degreeC.

Japanese Laid-Open Patent Publication No. 2008-73712 (A) Japanese Patent Application Laid-Open No. 8-165528 (A) Japanese Patent Application Laid-Open No. 2000-158178 (A) Japanese Laid-Open Patent Publication No. 9-3635 (A) Japanese Laid-Open Patent Publication No. 2003-226964 (A)

As shown in Patent Documents 1 to 4, as a method for producing polycrystalline tungsten and polycrystalline tungsten alloy, a powder metallurgy method (see Patent Documents 1, 3, 4, 5) or a melting method (see Patent Document 2) is well known. there is.

However, since the polycrystalline tungsten sintered compact and the polycrystalline tungsten alloy sintered compact produced by the powder metallurgical method have low density (low specific gravity), post-processing such as forging and rolling is generally performed as a means for achieving densification (Patent Document) 3, 4). However, when post-processing such as rolling or forging is performed, since anisotropy occurs in the crystal structure by the processing, anisotropy occurs in the properties (eg, strength) of the sintered body after processing.

On the other hand, when used in a low density state, for example, when used as a tungsten target material for sputtering described in Patent Document 5, particle defects at the time of sputtering film formation are increased. there is.

Here, "anisotropy" means a state in which many crystal grains with a high aspect ratio are contained in the crystal structure of the crystal grains constituting the sintered body, and more specifically, it means a case where the average aspect ratio of the crystal grains exceeds 2.5.

When anisotropy occurs as a sintered body characteristic of a polycrystalline tungsten sintered body and a polycrystalline tungsten alloy sintered body, when the polycrystalline tungsten sintered body and a member made by the polycrystalline tungsten alloy sintered body are used, the biased behavior depending on the direction of the grains (for example, one direction It shows locally biased wear and tear).

And the deflected behavior depending on the direction of the crystal grains causes deterioration of durability, reliability, etc. in the mid-to-long term of the member manufactured by the polycrystalline tungsten sintered compact and the polycrystalline tungsten alloy sintered compact. For example, when it is repeatedly used as an electrode material for resistance welding (refer patent document 3), it is easy to generate|occur|produce the crack at a grain boundary along a rolling direction, and as a result, a comparatively short life is shown. The rolled tungsten has a fibrous structure, but is prone to cracking along the structure by accumulation of residual stress.

On the other hand, when polycrystalline tungsten and polycrystalline tungsten alloy are produced by a melting method (see Patent Document 2), densification (high specific gravity) is achieved, but crystal grains are larger than those produced by powder metallurgy, and when cooling In the solidification process, anisotropy occurs because the growth rate of crystals is different depending on the cooling temperature gradient, and it is difficult to produce polycrystalline tungsten or polycrystalline tungsten alloy having a fine and uniform structure.

Depending on the intended use of the member, polycrystalline tungsten and polycrystalline tungsten alloy having a high density and no anisotropy (or low anisotropy) microstructure may be required. From the above, polycrystalline tungsten and polycrystalline tungsten alloy having high density and having no anisotropy as a fine structure are demanded.

The inventors of the present application studied various manufacturing methods for the purpose of obtaining polycrystalline tungsten and polycrystalline tungsten alloy having high density and having no anisotropy as a fine structure. As a result, by sintering the polycrystalline tungsten powder, polycrystalline tungsten alloy powder, or green compact thereof at an ultra-high pressure of 2.5 GPa or more and a high temperature of 1200 ° C. or more, a high-density, fine-grained structure with no anisotropy (or low anisotropy), It was discovered that a polycrystalline tungsten sintered compact and a polycrystalline tungsten alloy sintered compact could be obtained.

And it was discovered that said polycrystalline tungsten sintered compact and a polycrystalline tungsten alloy sintered compact were provided with the homogeneous material and characteristic while being excellent in intensity|strength and hardness.

This invention was made based on the said knowledge, and has the following aspects.

(1) In the polycrystalline tungsten sintered body, the relative density of the sintered body is 99% or more, the pore ratio measured in an arbitrary section of the sintered body is 0.2 area% or less, the average crystal grain size is 50 µm or less, and the average aspect ratio of the crystal grains is A polycrystalline tungsten sintered body having a high density of 1 to 2.5, a fine structure, and no anisotropy.

(2) The polycrystalline tungsten sintered body according to (1), wherein the porosity is 0.02 area% to 0.19 area%.

(3) The polycrystalline tungsten sintered body according to (1), wherein the porosity is 0.02 area% to 0.15 area%.

(4) The polycrystalline tungsten sintered body according to (1), wherein the average crystal grain size is 0.8 µm to 33.4 µm.

(5) The polycrystalline tungsten sintered body according to (1), wherein the average grain size is 0.8 µm to 18.3 µm.

(6) The polycrystalline tungsten sintered body according to (1) above, wherein the average aspect ratio is 1.0 to 2.2.

(7) The polycrystalline tungsten sintered body according to (1) above, wherein the average aspect ratio is 1.0 to 1.4.

(8) A polycrystalline tungsten alloy sintered body containing 25 mass% or more of tungsten, wherein the tungsten alloy is one or more alloys selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and Mn A tungsten alloy containing a component, wherein the relative density of the sintered body is 99% or more, the porosity measured in an arbitrary section of the sintered body is 0.2 area% or less, the average grain size is 50 µm or less, and the average aspect ratio of the crystal grains is 1 A high-density, fine-grained, non-anisotropic polycrystalline tungsten alloy sintered body of ~ 2.5.

(9) The polycrystalline tungsten alloy sintered body according to (8), wherein the porosity is 0.02 area% to 0.19 area%.

(10) The polycrystalline tungsten alloy sintered body according to (8), wherein the porosity is 0.02 area% to 0.15 area%.

(11) The polycrystalline tungsten alloy sintered body according to (8), wherein the average grain size is 0.8 µm to 33.4 µm.

(12) The polycrystalline tungsten alloy sintered body according to (8), wherein the average grain size is 0.8 µm to 18.3 µm.

(13) The polycrystalline tungsten alloy sintered body according to (8) above, wherein the average aspect ratio is 1.0 to 2.2.

(14) The polycrystalline tungsten alloy sintered body according to (8) above, wherein the average aspect ratio is 1.0 to 1.4.

(15) a raw material powder comprising tungsten particles having an average particle diameter of 50 μm or less, or a tungsten particle powder having an average particle diameter of 50 μm or less and Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and A raw material powder containing one or two or more alloy component particle powders selected from Mn or a green compact thereof is charged into a pressure sintering apparatus, and a pressing force of 2.55 GPa or more and 13 GPa or less is applied to the raw material powder or the green compact. A method for producing a polycrystalline tungsten sintered compact or polycrystalline tungsten alloy sintered compact with high density, fine structure, and no anisotropy, characterized in that in one state, sintering is carried out in a temperature range of 1200° C. or higher and less than or equal to the melting point.

The W sintered compact and W alloy sintered compact of one aspect of the present invention (hereinafter referred to as "the W sintered compact of the present invention" and "the W alloy sintered compact of the present invention") has a relative density of 99% or more, in any cross-section of the sintered compact. The measured pore ratio is 0.2 area% or less, the average grain size is 50 µm or less, and the average aspect ratio of the crystal grains is 1 to 2.5. Therefore, in various application fields, such as a target material and an electrode material, the outstanding characteristic can be exhibited over a long term.

1 : shows an example of the structure|tissue photograph of the W sintered compact of this invention.
Fig. 2 shows an example of a photograph of the structure of a W sintered compact produced by a conventional method (a combination of powder metallurgy and rolling).
3 : shows an example of the structure photograph of the W sintered compact produced by the conventional method (dissolution method).
4 : shows an example of the structure photograph of the W alloy (W: 50 mass %, Mo: 50 mass %) sintered compact of this invention.
5 : shows an example of the pore detection result measured with respect to the W alloy (W: 50 mass %, Mo: 50 mass %) sintered compact of this invention of FIG. 4 (used software: Image J). In this pore detection result, the pore rate was below the detection limit.
6 : shows an example of the structure photograph of the W alloy (W: 50 mass %, Mo: 50 mass %) sintered compact produced by the conventional method (HIP method).
Fig. 7 shows an example of pore detection results measured (used software: Image J) on a W alloy (W: 50 mass%, Mo: 50 mass%) sintered body produced by the conventional method (HIP method) of Fig. 6 . . In this pore detection result, the pore rate was 0.659% area.

Here, the "relative density" in the present invention means the ratio of the density of the polycrystalline tungsten sintered body measured by the Archimedes method to the theoretical density of tungsten, and the density of the polycrystalline tungsten alloy sintered body, tungsten and its It means the ratio with respect to the theoretical density of the alloy calculated|required by the content ratio of an alloying element element.

In addition, the "pore rate (area %)", "average crystal grain size (μm)" and "average aspect ratio of crystal grains (long side of crystal grain / short side of crystal grain)" in the sintered body are all in an arbitrary cross section of the sintered body. , means the average value of the numerical values measured from tissue observation performed using a scanning electron microscope (SEM) and an electron beam backscattering diffraction apparatus (EBSD).

In the structure observation by EBSD, 210 µm × 140 µm (vertical and horizontal dimensions) of an arbitrary cross section of the sintered body is an observation field, and all crystal grains included in this observation field are an observation object for obtaining an average value. In this case, the thing which exists in the observation field boundary part and contains only a part of crystal|crystallization in an observation field is excluded from observation.

In addition, the "average particle size" of the raw material powder refers to the particle size (cumulative median diameter: median diameter, d50) at 50% of the integrated value in the particle size distribution obtained by the laser diffraction/scattering method (microtrack method) with respect to the powder before sintering. ) means

In addition, the "polycrystalline tungsten alloy sintered compact" as used in this invention means the sintered compact which consists of a tungsten alloy containing 25 mass % or more of tungsten.

EMBODIMENT OF THE INVENTION This invention is demonstrated in detail below.

In addition, the present invention relates to a polycrystalline tungsten sintered compact, a polycrystalline tungsten alloy sintered compact, and a method for manufacturing the same. Hereinafter, the polycrystalline tungsten sintered compact is abbreviated as "W sintered compact", and the polycrystalline tungsten alloy sintered compact is abbreviated as "W alloy sintered compact", In addition, tungsten is abbreviated as "W".

The W sintered compact of the present invention is produced by sintering W particle powder having an average particle diameter of 50 µm or less. However, when the purity of the W particles is less than 99.9 mass%, the impurity component contained in W under the high-temperature sintering temperature causes W Since the sinterability of the sintered compact tends to vary, and the structure, material, and characteristics of the W sintered compact tend to become heterogeneous, the purity of the W particles used as the raw material powder is preferably 99.9 mass% or more.

In sintering, the W particle powder can be directly charged into the pressure sintering apparatus for sintering. However, the W particle powder can be prepared as a green compact in advance and charged into the pressure sintering apparatus for sintering.

When the average particle diameter of the W particles of the raw material powder exceeds 50 µm, a fine structure having an average grain size of 50 µm or less of the sintered body cannot be obtained due to grain growth during sintering. is set to 50 µm or less, but a more preferable average particle size is 0.25 to 50 µm.

With respect to the W sintered body of the present invention, when the relative density is measured by the Archimedes method, the measured relative density is 99% or more, and high density is achieved.

In addition, if the relative density is less than 99%, since densification of the sintered body is not sufficient, the pore ratio cannot be reduced to 0.2 area% or less, so the relative density of the W sintered body is made 99% or more.

1 shows an example of a photograph of the structure of the W sintered compact of the present invention, however, in the W sintered compact shown in this photograph of the structure, the presence of pores was not confirmed (pore ratio ≒ 0 area%), and the average crystal grain size was 50 µm. Hereinafter, it turns out that an isotropic crystal structure is provided as a fine structure which satisfies the average aspect-ratio of 1-2.5 of crystal grains. The W sintered compact of the present invention shown in Fig. 1 is a high-density W sintered compact having a relative density of 99.69% (specific gravity: 19.24), as sintered at 1700°C for 20 minutes at 1700°C in a state of adding a pressing force of 6.1 GPa, and measured by the Archimedes method. , and also had high hardness at Vickers hardness HV: 460.

Vickers hardness HV can be measured by the method defined by JIS standard Z2244.

In the sintered body of the present invention, when the pore ratio is set to 0.2 area% or less, when the pore ratio exceeds 0.2 area%, it cannot be said to be a dense and high-density W sintered body having a large specific gravity, for example, the pore ratio is 0.2 It is because when the W sintered compact exceeding area% is used as an electrode for welding, only the part of a pore becomes an insulating state, and especially in high voltage welding, it becomes easy to become a fracture origin. Moreover, when a pore ratio uses the W sintered compact exceeding 0.2 area% as a target material, any part of a pore will generate|occur|produce abnormal discharge, or will show the non-uniform|heterogenous reduction method.

Although not particularly essential, the preferred range of the pore ratio is more than 0 area% to 0.2 area%. A more preferable range of the pore ratio is 0.02 area% to 0.19 area%. A more preferable range of the pore ratio is 0.02 area% to 0.15 area%. A more preferable range of the pore ratio is 0.02 area% to 0.12 area%.

In the sintered body of the present invention, the average grain size is set to 50 µm or less because, when the average grain size exceeds 50 µm, it becomes a coarse grain structure and a fine grain structure excellent in strength and hardness cannot be obtained.

Although not particularly essential, the preferred range of the average grain size is 0.8 mu m to 33.4 mu m. A more preferable range of the average grain size is 0.8 µm to 18.3 µm. A more preferable range of the average crystal grain size is 2.6 µm to 14.0 µm.

In addition, in the sintered body of the present invention, when the average aspect ratio of the crystal grains (=long side of the crystal grain / short side of the crystal grain) is set to 1 to 2.5, when the average aspect ratio is outside this range, anisotropy occurs in the crystal structure, resulting in a homogeneous material This is because the characteristic cannot be obtained. That is, in this specification, "there is no anisotropy" with respect to a crystal structure means that the average aspect-ratio of the crystal grain in the target sintered body exists in the range of 1-2.5. Conversely, "there is anisotropy" means that the said average aspect-ratio exists outside the range of 1-2.5.

Although not particularly essential, the preferred range of the average aspect ratio is 1 to 2.2. A more preferable range of the average aspect ratio is 1 to 1.4.

The W sintered compact of the present invention is not a specific cross-section, and since the pore ratio, average grain size, and average aspect ratio of grains measured in any cross-section of the sintered compact are all within the above ranges, the sintered compact structure has no anisotropy and isotropic It can be seen that the organization is provided.

2, 3, the structure|tissue photograph of the W sintered compact produced by the conventional method is shown.

2 : is an example of the structure photograph in the surface along the rolling direction of the W sintered compact (refer patent documents 3 and 4) produced by combining powder metallurgy method and rolling.

After producing the W sintered compact by the powder metallurgy method, by performing processing such as rolling, the density of the sintered compact can be increased to some extent, and in FIG. 2 , relative density: 99.48% (specific gravity: 19.2), and Vickers hardness HV: 500 is being obtained.

However, on the other hand, since anisotropy occurs in the crystal structure of the sintered body by processing (in FIG. 2, vertical stripes or fibrous crystal structures are observed, and the average aspect ratio in the surface along the rolling direction is 6.5 or more. ), a sintered compact having a fine and uniform structure cannot be obtained, and as a result, isotropic properties cannot be expected from this W sintered compact.

3 : is an example of the structure photograph of the W sintered compact produced by the dissolution method (refer patent document 2).

In the W sintered compact obtained by the dissolution method shown in FIG. 3, sufficient densification is not attained (relative density: 99.33% (specific gravity: 19.17)), and also hardness (Vickers hardness HV: 440) is not enough. In addition, in the solidification process after dissolution, anisotropy occurs because the growth rate of crystals differs depending on the cooling temperature gradient, so that a W sintered body having a fine and uniform structure cannot be obtained.

The W sintered compact of this invention can be manufactured by the following method, for example.

As described above, the W particle powder having a purity of 99.9 mass% or more and having an average particle diameter of 0.25 to 50 μm is charged into a pressure sintering apparatus, and a pressing force of 2.55 GPa or more and 13 GPa or less is applied to the powder. , 1200 ° C. or higher melting point or lower (for example, 1200 to 2000 ° C.) by sintering for 10 minutes or more in a high density and fine structure having a pore ratio, average grain size, and average aspect ratio of grains prescribed in the present invention And it is possible to manufacture a W sintered body without anisotropy.

If the sintering pressure is less than 2.55 GPa, densification does not occur, and on the other hand, adding a pressure exceeding 13 GPa is not economical from the viewpoint of device development cost and actual operation, so the sintering pressure is 2.55 GPa or more and 13 GPa or less. did

In addition, when the sintering temperature is less than 1200°C, the solid phase reaction does not proceed, and on the other hand, when the sintering temperature exceeds the melting point, the same problems as in the production by the dissolution method (for example, coarsening of crystal grains, crystals in the solidification process) structure anisotropy) occurs, and a high-density, fine-grained and uniform W sintered body cannot be obtained, so the sintering temperature is in a temperature range of 1200°C or more and less than or equal to the melting point, preferably 1200°C or more and 2000°C or less. The temperature range was determined.

In addition, the W particle powder can be prepared as a green compact in advance prior to sintering, and the green compact is sintered at the above sintering pressure, sintering temperature, and sintering time to obtain the W sintered compact of the present invention.

When using fine W particle powder with a large specific surface area (for example, an average particle diameter of 0.25 to 4 µm) as the raw material powder, this is used as a green compact, and prior to sintering, for example, 10 ^-1 Pa or less When the W particle surface is cleaned by performing heat treatment for 30 to 180 minutes at an ultimate temperature of 450 to 1200°C in a vacuum atmosphere or an atmosphere in which the heat treatment vessel is replaced with nitrogen gas or argon gas, the sintering reaction tends to proceed. Therefore, it is possible to achieve high density of the sintered body in a short time even in a relatively low pressure condition and a low temperature range.

In addition, even if an impurity element such as oxygen exists to some extent in the W particle powder, it can be removed and purified by the above-mentioned vacuum or heat treatment in an inert gas atmosphere, and the purity of the W particle powder is 99.9 mass%. can be raised higher than that.

In addition, the average particle diameter of the W particle powder is preferably within the range of 0.25 to 50 µm as a whole, but it is not necessary that there is only one peak of the particle size distribution frequency (representing the particle size distribution of a unimodal peak), and a plurality of particle size distribution frequency peaks ( W particle powder with multimodal frequency particle size distribution) can also be used. In this case, the sintering reaction proceeds even in a relatively low pressure condition and low temperature range because small particle size particles enter the gaps between the large particle diameter particles, thereby further increasing the density of the sintered body. Together, a W sintered body with a fine structure and no anisotropy is obtained.

In any case, a high-density W sintered compact can be obtained by sintering under the conditions as described above and providing sufficient sintering time to plastically deform and rearrange the W particles under high temperature and high pressure.

As described above for the W sintered body, the present invention provides one or two or more alloy components selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and Mn as an alloy component together with the W particle powder. By using the raw material powder blended with the particle powder, it is possible to obtain a high-density, fine-grained, non-anisotropic W alloy sintered body.

Here, the W alloy sintered body containing one or two or more of each component selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and Mn as an alloy component is, for example, an electrode for resistance welding. Although it is used as a material, a target material, etc., in either case, similarly to the said W sintered compact, a W alloy sintered compact with high density and a fine structure and no anisotropy is calculated|required.

In a W alloy sintered compact with a small W content, it was possible to achieve high density of the sintered compact by a conventional manufacturing method of the sintered compact, for example, HIP, etc., but the W content increases, for example, the W content is 25 mass% or more Regarding the W alloy sintered body, in the conventional method, it was not possible to obtain a high-density, fine-grained, non-anisotropic W alloy sintered body.

However, according to the present invention, W content is 25 mass% or more, and W containing one or two or more selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and Mn as the alloy component Also in the alloy sintered body, similarly to the above W sintered body, it is possible to obtain a high-density, fine-grained, non-anisotropic W alloy sintered body.

The W alloy sintered compact of the present invention can be produced by sintering under the same conditions as in the production of the W sintered compact.

However, one or more alloy component particle powders selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and Mn, which are raw material powders, all have an average particle diameter of 50 from the viewpoint of refining the structure of the sintered body. A metal particle powder of ㎛ or less is used.

W particle powder having an average particle diameter of 50 μm or less, and one or more alloy component particle powders selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and Mn having an average particle diameter of 50 μm or less, are prepared in a sintered compact. A raw material powder blended so that the W content is 25 mass% or more, or a green compact produced from the raw material powder is charged in a pressure sintering apparatus, and a pressing force of 2.55 GPa or more and 13 GPa or less is applied, By sintering in a temperature range of 1200°C or higher and lower than or equal to the melting point, a high-density, fine-grained W alloy sintered body having no anisotropy can be produced.

In addition, when using a powder with a large specific surface area (for example, an average particle diameter of 0.25 to 4 µm) as the raw material powder, this is used as a green compact, and prior to sintering, for example, a vacuum of 10 ^-1 Pa or less When the particle surface is cleaned by performing heat treatment for 30 to 180 minutes at an ultimate temperature of 450 to 1200°C in an atmosphere or an atmosphere in which the heat treatment vessel is replaced with nitrogen gas or argon gas, a relatively low pressure condition, low temperature region Even if it is, it is possible to achieve high density of the sintered body in a short time, and even if an impurity element such as oxygen is present to some extent in the particle powder, it is removed/cleaned by the above-mentioned heat treatment in a vacuum or an inert gas atmosphere. can do.

The reason for determining the pore ratio, average grain size, and average aspect ratio of the grains of the W alloy sintered body of the present invention is the same as in the case of the W sintered body, and also in the W alloy sintered body of the present invention, not a specific cross section, but any of the sintered bodies It can be seen that the pore ratio, the average grain size, and the average aspect ratio of the grains measured in the cross section of the sintered compact are all within the specified range, and the sintered compact structure has no anisotropy and an isotropic structure.

An example of the structure|tissue photograph of the W alloy sintered compact of this invention in FIG. 4 is shown.

The W alloy sintered compact shown in FIG. 4 is a W-Mo alloy sintered compact which consists of W: 50 mass % and Mo: 50 mass %, It is produced by sintering for 500 degreeC x 20 minutes in the state which added the pressing force of 5.8 GPa. .

With respect to the W-Mo alloy sintered body of Fig. 4, the relative density measured by the Archimedes method was a high-density W-Mo alloy sintered body of 99.32% (specific gravity: 13.27), and the Vickers hardness HV was 330 and had high hardness.

Moreover, the theoretical density of the W-Mo alloy sintered compact which consists of W: 50 mass % and Mo: 50 mass % is 13.36 (The theoretical density of W: 19.3, The theoretical density of Mo: 10.2).

In Fig. 5, the pore detection result measured (used software: Image J) for the W-Mo alloy sintered compact (hereinafter referred to as "the W-Mo alloy sintered compact of the present invention") which is another aspect of the present invention shown in Fig. 4 . indicates

According to FIG. 5, it was confirmed that the pore ratio with respect to the W-Mo alloy sintered compact of this invention is below a detection limit, and pore does not exist substantially.

For comparison, by a conventional method (HIP method), a W-Mo alloy sintered body composed of W: 50 mass% and Mo: 50 mass% having the same composition as that of the W-Mo alloy sintered body of the present invention was produced.

In addition, the manufacturing conditions in the HIP method are 34.32 Mpa of pressing force, and 1400 degreeC x 3 hours.

An example of the structure|tissue photograph of the W-Mo alloy sintered compact produced by the said conventional method (HIP method) in FIG. 6 is shown.

As a result of measuring the relative density and Vickers hardness HV of the W-Mo alloy sintered body produced by the conventional method (HIP method), the relative density was 96.33% (specific gravity: 12.87), and the Vickers hardness HV was 255, both of the relative density and hardness. It was inferior compared with the W-Mo alloy sintered compact of this invention.

In FIG. 7, an example of the pore detection result measured (used software: Image J) with respect to the W-Mo alloy sintered compact produced by the conventional method (HIP method) shown in FIG. 6 is shown.

According to FIG. 7, the pore ratio is 0.659 area%, and it is clear that densification is not enough.

Hereinafter, the present invention will be described in detail by way of Examples.

Example 1

As a raw material, W particle powder having an average particle diameter shown in Table 1 was prepared, and this was sintered under pressure under the sintering conditions shown in Table 1 in the same manner to prepare W sintered compacts 1 to 8 of the present invention shown in Table 1 similarly. did

In addition, in the preparation of the W sintered compacts 6 to 8 of the present invention, a W particle powder having a plurality of particle size distribution frequency peaks (multimodal frequency particle size distribution) shown in Table 1 was used as the raw material powder.

In addition, with respect to the W sintered compacts (6 to 8) of the present invention, after producing a green compact from W particle powder, prior to sintering, in a vacuum atmosphere of 10 ^-1 Pa, at an ultimate temperature of 580 to 620°C, and 30 to 40 min. Vacuum heat treatment was performed.

Next, the relative density (specific gravity) of these sintered compacts was measured by the Archimedes method. Next, with respect to these sintered bodies, one sintered body cross section X is set in an arbitrary direction, cross sections Y and Z are set orthogonal to this set cross section X, and the pore ratio in sections X, Y, Z, The average crystal grain size and the average aspect-ratio of the crystal grains are determined by tissue observation using a scanning electron microscope (SEM) and an electron beam backscattering diffraction device (EBSD), and the Vickers hardness HV in the cross-sections X, Y, and Z is further determined measured.

In addition, the pore ratio is a magnification at which about 15 to 30 W particles can be observed on the vertical and horizontal axes of the SEM image (for example, 3000 times when the W particle diameter is 2 to 4 μm, and When the W particle size is 10 to 20 µm, 500 times) WHEREIN: It binarized using Image J, a pore and the part which is not a pore were measured, and it calculated|required by 3 field of view average.

The average crystal grain size and the average aspect-ratio were calculated by the average of three fields of view of the particle information obtained using EBSD at the same observation magnification as described above.

In addition, Vickers hardness HV was computed as a 5-point average of the value measured with 1 kg of load.

These results are shown in Table 2.

In FIG. 1, an example of the structure|tissue of the W sintered compact 5 of this invention is shown.

In addition, for comparison, the relative density (specific gravity), pore rate, and average grain size shown in Table 4 were prepared by preparing W particle powder of the average particle diameter shown in Table 3, and sintering this under the sintering conditions shown in Table 3 similarly. , Comparative Example W sintered compacts (1 to 5) having an average aspect-ratio of crystal grains and Vickers hardness HV were produced.

For this comparative example W sintered compact (1-5), in the same manner as in Example 1, relative density (specific gravity), pore ratio, average crystal grain size, average aspect ratio of crystal grains, and Vickers hardness HV were obtained.

These results are shown in Table 4.

In addition, for reference, using the W particle|grain powder of the average particle diameter shown in Table 3, the conventional example W sintered compact (1, 2) was produced by the conventional manufacturing method.

Moreover, relative density (specific gravity), pore ratio, average grain size, average aspect-ratio of crystal grains, and Vickers hardness HV were calculated|required with respect to the sintered compact of the prior art example W (1, 2).

These results are shown in Table 4.

In addition, the prior art example W sintered compact (1) is a W sintered compact obtained by performing a rolling process as described in patent documents 3, 4, Moreover, the conventional example W sintered compact (2) is described in patent document 2 It is a W sintered compact produced by the dissolution method as described above.

An example of the structure|tissue in the surface along the rolling direction of the sintered compact 1 of the prior art example W is shown in FIG. 2, and an example of the structure|tissue of the sintered body 2 of the prior art example W is shown in FIG.

In addition, the pore ratio, average grain size, average aspect ratio, and Vickers hardness HV of the comparative example W sintered body (1-5) and the conventional example W sintered body (1, 2) are the above-mentioned case of the said invention W sintered body (1-8) was obtained in the same way as

Example 2

As a raw material, one or two selected from W particle powder having the average particle diameter shown in Table 5 and Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and Mn having the same average particle diameter shown in Table 5 The present invention W shown in Table 6 by preparing the above alloy component particle powder, blending it so as to have the composition shown in Table 5, to prepare a mixed raw material powder, and pressurizing the mixed raw material powder under the sintering conditions shown in Table 5. Alloy sintered bodies 11 to 20 were produced.

In addition, with respect to the W alloy sintered compacts 18 to 20 of the present invention, a green compact is produced from a mixed raw material powder of W grain powder and alloy component grain powder, and then, prior to sintering, in a vacuum atmosphere of 10 ⁻¹ Pa at an ultimate temperature of 580 Vacuum heat treatment was performed at -620°C for 30 to 40 min.

Then, in the same manner as in Example 1, the relative density (specific gravity), porosity, average grain size, average aspect ratio of grains, and Vickers hardness HV of the W alloy sintered bodies 11 to 20 of the present invention were obtained.

These results are shown in Table 6.

Fig. 4 shows an example of the structure of the W alloy sintered body 15 of the present invention, and Fig. 5 shows the pore detection results measured (used software: Image J) for the W alloy sintered body of the present invention shown in Fig. 4 . An example is shown.

In addition, for comparison, by preparing W particle powder and metal particle powder having an average particle diameter shown in Table 7, and sintering this under the sintering conditions shown in Table 7 similarly, the relative density (specific gravity) and pore rate shown in Table 8 , Comparative Example W alloy sintered bodies (11 to 15) having average grain size, average aspect-ratio of grains, and Vickers hardness HV were produced.

Relative density (specific gravity), porosity, average grain size, average aspect-ratio of grains, and Vickers hardness HV were obtained for this comparative example W alloy sintered body (11-15) in the same manner as in Example 1. These results are shown in Table 8.

For reference, using the W particle powder and metal particle powder of the average particle diameter shown in Table 7, conventional example W alloy sintered bodies 11 and 12 were prepared by a conventional manufacturing method, and the relative density (specific gravity), pore ratio , average grain size, average aspect-ratio of grains, and Vickers hardness HV were obtained.

These results are shown in Table 8.

In addition, the W alloy sintered compact 11 of the prior art example is a W alloy sintered compact obtained by performing rolling processing, and the W alloy sintered compact 12 of the prior art example is a W alloy sintered compact produced by the melting method.

In addition, an example of the structure of the W alloy sintered body 11 of the conventional example is shown in FIG. 6, and in FIG. 7, an example of the pore detection result measured (using software: Image J) for the W alloy sintered body of the conventional example shown in FIG. 6 is shown. indicates

According to the results shown in Tables 2, 4, 6, and 8, the W sintered body and the W alloy sintered body of the present invention have a relative density of 99% or more, and the pore rate observed at any cross section of the sintered body is It is a sintered compact having a fine structure of 0.2 area% or less, an average crystal grain size of 50 µm or less, and an average aspect ratio of crystal grains of 1 to 2.5 and no anisotropy.

On the other hand, in the comparative example W sintered compact, the conventional example W sintered compact, the comparative example W alloy sintered compact, and the conventional example W alloy sintered compact, at least any of the relative density, the pore ratio, the average grain size, or the average aspect ratio of the grains is within the range determined by the present invention. It is clear that it cannot be said to be a sintered compact with high density and no anisotropy as it is out of .

Industrial Applicability

Since the W sintered compact and W alloy sintered compact of this invention are high density and there is no anisotropy, for example, it can use suitably for uses, such as a target material for sputtering, an electrode material for welding.

Claims (16)

delete delete delete delete delete delete delete A polycrystalline tungsten alloy sintered body containing 25 mass% or more of tungsten, wherein the tungsten alloy is a tungsten alloy containing one or more alloy components selected from Ti, Nb and Mn, and the relative density of the sintered body is 99 % or more, a high-density, fine-grained polycrystalline tungsten alloy having a pore ratio of 0.2 area% or less, an average grain size of 50 µm or less, and an average aspect ratio of crystal grains of 1 to 2.5 measured in an arbitrary section of the sintered body, and no anisotropy sintered body. 9. The method of claim 8,
The polycrystalline tungsten alloy sintered body having the porosity of 0.02 area% to 0.19 area%. 9. The method of claim 8,
The polycrystalline tungsten alloy sintered body having the said porosity 0.02 area% - 0.15 area%. 9. The method of claim 8,
The polycrystalline tungsten alloy sintered body having an average grain size of 0.8 µm to 33.4 µm. 9. The method of claim 8,
The polycrystalline tungsten alloy sintered body having an average grain size of 0.8 µm to 18.3 µm. 9. The method of claim 8,
The polycrystalline tungsten alloy sintered body having an average aspect ratio of 1.0 to 2.2. 9. The method of claim 8,
The polycrystalline tungsten alloy sintered body having an average aspect ratio of 1.0 to 1.4. A raw material powder made of tungsten particles having an average particle diameter of 50 µm or less or a green compact thereof is charged into a pressure sintering apparatus, and a pressing force of 2.55 GPa or more and 13 GPa or less is applied to the raw material powder or the green compact, 1200° C. or more High-density, fine-grained, non-anisotropic, characterized by sintering in a temperature range below the melting point A method for manufacturing a polycrystalline tungsten sintered body. Raw material containing tungsten particle powder with an average particle diameter of 50 μm or less and one or more alloy component particle powders selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and Mn with an average particle diameter of 50 μm or less The powder or the green compact is charged into a pressure sintering apparatus, and the raw material powder or the compact is sintered in a temperature range of 1200 ° C. or more and the melting point or less in a state where a pressing force of 2.55 GPa or more and 13 GPa or less is applied. A method for producing a polycrystalline tungsten alloy sintered body having a high density, fine structure, and no anisotropy.

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