WO2014006779A1 - Tungsten alloy part, and discharge lamp, transmitting tube and magnetron using same - Google Patents

Abstract

Provided is a tungsten alloy part which comprises tungsten and at least two types of components selected from the group consisting of Zr, ZrO₂, ZrC and C. This tungsten alloy part contains 0.1-5 wt% of Zr in terms of ZrO₂.

Description

Tungsten alloy parts, and discharge lamps, transmitter tubes and magnetrons using the same

Embodiments of the present invention relate to a tungsten alloy part, and a discharge lamp, a transmission tube, and a magnetron using the tungsten alloy part.

Tungsten alloy parts are used in various fields using the high-temperature strength of tungsten. Examples thereof include a discharge lamp, a transmission tube, and a magnetron. In a discharge lamp (HID lamp), tungsten alloy parts are used for cathode electrodes, electrode support rods, coil parts, and the like. In the transmission tube, tungsten alloy parts are used for filaments and mesh grit. In the magnetron, tungsten alloy parts are used for coil parts. These tungsten alloy parts have a shape of a coil part in which a sintered body having a predetermined shape, a wire, and a wire are coiled.

Conventionally, tungsten alloys containing thorium (or a thorium compound) are used for these tungsten alloy parts as described in JP-A-2002-226935 (Patent Document 1). The tungsten alloy of Patent Document 1 improves deformation resistance by finely dispersing the average particle diameter of thorium particles and thorium compound particles to 0.3 μm or less. Thorium-containing tungsten alloys are used in the aforementioned fields because of their excellent emitter characteristics and mechanical strength at high temperatures.

However, since thorium or a thorium compound is a radioactive substance, a tungsten alloy part that does not use thorium is desired in consideration of the influence on the environment. In Japanese Patent Laid-Open No. 2011-103240 (Patent Document 2), a tungsten alloy part containing lanthanum boride (LaB ₆ ) has been developed as a tungsten alloy part that does not use thorium.

On the other hand, Patent Document 3 describes a short arc type high-pressure discharge lamp using a tungsten alloy containing lanthanum oxide (La ₂ O ₃ ) and HfO ₂ or ZrO ₂ . According to the tungsten alloy described in Patent Document 3, sufficient emission characteristics cannot be obtained. This is because the melting point of lanthanum oxide is as low as about 2300 ° C., so when the applied voltage or current density is raised, the lanthanum oxide evaporates early when the temperature of the component becomes high, and the emission characteristics deteriorate. .

JP 2002-226935 A JP 2011-103240 A Japanese Patent No. 4741190

For example, discharge lamps, which are a kind of application of tungsten alloy parts, can be broadly divided into two types: low pressure discharge lamps and high pressure discharge lamps. Examples of the low-pressure discharge lamp include various arc discharge type discharge lamps such as general lighting, special lighting used for roads and tunnels, paint curing devices, UV curing devices, sterilization devices, and semiconductor photo-cleaning devices. In addition, high-pressure discharge lamps include water and sewage treatment equipment, general lighting, outdoor lighting for stadiums, UV curing equipment, exposure equipment for semiconductors and printed circuit boards, wafer inspection equipment, high-pressure mercury lamps for projectors, metal halide lamps, Examples include ultra-high pressure mercury lamps, xenon lamps and sodium lamps.

A voltage of 10 V or more is applied to the discharge lamp according to its application. In the tungsten alloy containing lanthanum boride described in Patent Document 2, a life equal to that of the thorium-containing tungsten alloy was obtained when the voltage was less than 100V. However, as the voltage increased to 100 V or higher, the emission characteristics were lowered, and as a result, the life was greatly reduced.

Similarly, the transmitter tube and magnetron have a problem that sufficient characteristics cannot be obtained as the applied voltage increases.

The present invention provides a tungsten alloy part that does not use thorium, which is a radioactive substance, and exhibits characteristics equivalent to or better than those of a thorium-containing tungsten alloy part, and a discharge lamp, a transmission tube, and a magnetron using the tungsten alloy part. It is the purpose.

According to the embodiment, there is provided a tungsten alloy part including tungsten and at least two components selected from the group consisting of Zr, ZrO ₂ , ZrC, and C (hereinafter referred to as Zr component). The tungsten alloy part contains the Zr component in an amount of 0.1 to 5 wt% in terms of ZrO ₂ . The tungsten alloy part preferably contains 0.1 to 3 wt% of the Zr component in terms of ZrO ₂ . When the contents of Zr and O are converted to ZrO _x, x <2 is preferable, and 0 <x <2 is more preferable.

The tungsten alloy part may further contain 0.01 wt% or less of at least one element selected from the group consisting of K, Si and Al. Further, the tungsten alloy may contain 2 wt% or less of at least one of Ti, Hf, V, Nb, Ta, Mo, and rare earth elements. In particular, when the total content of Zr is 100 parts by mass, it may contain 15 parts by mass or less of Hf.

The primary particles of ZrO ₂ preferably have an average particle size of 15 μm or less, more preferably an average particle size of 5 μm or less and a maximum diameter of 15 μm or less. The secondary particles of ZrO ₂ preferably have a maximum diameter of 100 μm or less.

The Zr component is preferably present as two types of ZrO ₂ and metal Zr. It is preferable that at least a part of the metal Zr is dissolved in tungsten. The metal Zr is preferably present on the surface of the tungsten alloy part. Further, when the total content of Zr is 100 parts by mass, the content of Zr constituting ZrO ₂ is preferably 30 to 98 parts by mass.

The tungsten alloy part preferably has a wire diameter of 0.1 to 30 mm and a Vickers hardness Hv of 330 or more, particularly preferably in the range of 330 to 700.

It is preferable that the electrode component for a discharge lamp has a tip portion having a tapered tip and a cylindrical body portion. When the crystal structure of the transverse section (radial section) of the body part is observed, the area ratio of tungsten crystals having a crystal grain size of 1 to 80 μm per unit area (for example, 300 μm × 300 μm) is 90% or more. preferable. When the crystal structure of the longitudinal section of the body portion is observed, the area ratio of tungsten crystals having a crystal grain size of 2 to 120 μm per unit area (for example, 300 μm × 300 μm) is preferably 90% or more.

The tungsten alloy component of the embodiment is used for a discharge lamp component, a transmitter tube component, or a magnetron component, for example.

The discharge lamp of the embodiment uses the tungsten alloy part of the embodiment. The transmission tube of the embodiment uses the tungsten alloy component of the embodiment. The magnetron of the embodiment uses the tungsten alloy component of the embodiment.

When the tungsten alloy part of the embodiment is applied to an electrode of a discharge lamp, it is preferable that an applied voltage to the electrode is 100 V or more. Since the tungsten alloy part of the embodiment constituting the electrode for the discharge lamp does not contain thorium (or thorium oxide) which is a radioactive substance, there is no adverse effect on the environment. In addition, the discharge lamp electrode made of the tungsten alloy component of the embodiment has characteristics equal to or better than those made of a thorium-containing tungsten alloy. For this reason, the discharge lamp using the tungsten alloy component of the embodiment is environmentally friendly.

FIG. 1 is a diagram illustrating an example of an electrode component for a discharge lamp according to an embodiment. FIG. 2 is a diagram illustrating another example of the electrode component for a discharge lamp according to the embodiment. FIG. 3 is a diagram illustrating an example of the discharge lamp according to the embodiment. FIG. 4 is a diagram illustrating an example of a magnetron component according to the embodiment. FIG. 5 is a diagram illustrating an example of an electrode component for a discharge lamp according to the embodiment. FIG. 6 is a diagram illustrating another example of the electrode component for a discharge lamp according to the embodiment. FIG. 7 is a diagram illustrating an example of a cross section of the body portion of the electrode component for a discharge lamp according to the embodiment. Drawing 8 is a figure showing an example of the longitudinal section of the body part of the electrode component for discharge lamps of an embodiment. FIG. 9 is a diagram illustrating an example of the discharge lamp according to the embodiment. FIG. 10 is a graph showing the relationship between the emission current density and the applied voltage in Example 1 and Comparative Example 1.

The tungsten alloy component of the embodiment includes tungsten and at least two components selected from the group consisting of Zr, ZrO ₂ , ZrC, and C, and contains 0.1 to 5 wt% of Zr in terms of ZrO _2. . Zr is preferably contained in an amount of 0.1 to 3 wt% in terms of ZrO ₂ .

By containing 0.1 to 5 wt% of Zr (zirconium) in terms of ZrO ₂ (zirconium oxide), characteristics such as emission characteristics and strength can be improved. That is, if the Zr content is less than 0.1 wt% in terms of ZrO ₂ , the effect of addition is insufficient, and if it exceeds 3 wt%, the characteristics deteriorate. The Zr content is preferably 0.5 to 2.5 wt% in terms of ZrO ₂ .

The tungsten alloy component of the embodiment contains at least two components selected from the group consisting of Zr, ZrO ₂ , ZrC, and C. Specifically, a combination of Zr and ZrO _2, a combination of ZrO ₂ and ZrC (zirconium carbide), a combination of ZrO ₂ and C (carbon), a combination of Zr, ZrO ₂ and ZrC, and a combination of ZrO ₂ , ZrC and C , Zr and ZrO ₂ and C combined, contains a ZrO ₂ component in any combination of Zr and ZrO ₂ and ZrC and C (carbon). Comparing the melting points, metal Zr is 1850 ° C., ZrO ₂ is 2720 ° C., ZrC is 3420 ° C., and tungsten is 3400 ° C. (refer to Iwanami Shoten “Rikagaku Encyclopedia”). Metal thorium has a melting point of 1750 ° C., and thorium oxide (ThO ₂ ) has a melting point of 3220 ± 50 ° C. Since zirconium has a higher melting point than thorium, the tungsten alloy component of the embodiment can have high temperature strength equal to or higher than that of thorium-containing tungsten alloy component.

When the contents of Zr and O are converted to ZrOx, it is preferable that x <2. The fact that x <2 does not mean that all ZrO ₂ components contained in the tungsten alloy are present in the form of stoichiometric ZrO ₂ , and that some of them are metals Zr and ZrC. means. Although the work function of the metal Zr is 4.1 and is larger than the work function of the metal Th, it is considered that the emission characteristics are deteriorated. However, there is no particular problem in applications such as discharge lamps. . Metal zirconium is an effective element for improving strength because it forms a solid solution with tungsten. When the contents of Zr and O are converted to ZrOx, 0 <x <2 is preferable. x <2 is as described above. In addition, 0 <x means that either ZrC or C is present in the tungsten alloy. ZrC or C has a deoxidizing effect for removing impurity oxygen contained in the tungsten alloy. By reducing the impurity oxygen, the electrical resistance value of the tungsten component can be lowered, so that the characteristics as an electrode are improved. When Z of ZrOx is in the above range, metals Zr, ZrO ₂ , ZrC or C exist in a well-balanced manner, and characteristics such as emission characteristics, strength, electrical resistance, and life are improved.

The contents of Zr, ZrO ₂ , ZrC, and O in the tungsten alloy part can be measured using an ICP analysis method and an inert gas melting-infrared absorption method. In the ICP analysis method, the total amount of Zr of metal Zr and the amount of Zr of ZrO ₂ and ZrC can be measured. In the inert gas melting-infrared absorption method, the total amount of oxygen of ZrOx and the amount of oxygen present alone or as another oxide can be measured. In the embodiment, the Zr amount and the O amount are measured by an ICP analysis method and an inert gas melting-infrared absorption method, and converted to ZrOx.

The tungsten alloy component of the embodiment may contain 0.01 wt% or less of at least one element selected from the group consisting of K, Si, and Al. K (potassium), Si (silicon), and Al (aluminum) are so-called dope materials, and recrystallization characteristics can be improved by adding these dope materials. By improving the recrystallization characteristics, it becomes easier to obtain a uniform recrystallized structure when the recrystallization heat treatment is performed. Although the minimum of content of dope material is not specifically limited, It is preferable that it is 0.001 wt% or more. If it is less than 0.001 wt%, the effect of addition is small, and if it exceeds 0.01 wt%, the sinterability and workability may be deteriorated and the mass productivity may be reduced.

The tungsten alloy component of the embodiment preferably contains 15 parts by mass or less of Hf when the Zr content is 100 parts by mass. The content of Zr indicates the total amount of Zr of Zr, ZrO ₂ and ZrC. Since Hf (hafnium) has a high melting point of 2207 ° C., there is little adverse effect even if it is contained in tungsten alloy parts. Commercially available Zr powder may contain several percent of Hf depending on the grade. The use of high-purity Zr powder or high-purity ZrO ₂ powder from which impurities are removed is effective for improving the characteristics. On the other hand, increasing the purity of the raw material increases the cost. When Zr is 100 parts by weight, if the Hf (hafnium) content is 15 parts by mass or less, it is not necessary to deteriorate the characteristics more than necessary.

In the tungsten alloy component of the embodiment, it is preferable that C1 <C2 when the carbon content in the surface portion is C1 (wt%) and the carbon content in the central portion is C2 (wt%). The surface portion indicates a portion from the surface of the tungsten alloy part to 20 μm. The central portion is a central portion in the cross section of the tungsten alloy part. This carbon amount is a total value of both carbon of a carbide such as ZrC and carbon present alone, and can be analyzed by a combustion-infrared absorption method. The fact that the amount of carbon in the surface portion C1 <the amount of carbon in the central portion C2 indicates that the carbon in the surface portion was converted to CO ₂ by deoxidation and went out of the system. When the amount of carbon in the surface portion decreases, the amount of Zr in the surface portion relatively increases. For this reason, it is particularly effective when Zr is used as an emitter material.

The tungsten alloy part of the embodiment preferably contains a tungsten crystal having an average crystal grain size of 1 to 100 μm. The tungsten alloy part is preferably a sintered body. If it is a sintered body, it is possible to produce parts having various shapes by using a molding process. In addition, the sintered body can be easily processed into a wire rod (including a filament), a coil component, and the like by performing a forging process, a rolling process, a drawing process, and the like. The sintered tungsten crystal has an isotropic crystal structure with 90% or more of crystals having an aspect ratio of less than 3. When such a sintered body is drawn, a crystal having an aspect ratio of 3 or more becomes a flat crystal structure of 90% or more. The grain size of the tungsten crystal can be determined as follows. First, a crystal structure is taken with an enlarged photograph of a metal microscope or the like. The maximum ferret diameter is measured for one tungsten crystal existing in the cross section to obtain a particle diameter. This measurement is performed on any 100 tungsten crystals, and the average value is defined as the average crystal grain size.

If the average of the maximum ferret diameter of the tungsten crystal is as small as less than 1 μm, it becomes difficult to make the dispersion state of the dispersed components such as Zr, ZrO ₂ , ZrC or C uniform. This is because if the average of the maximum ferret diameter of the tungsten crystal is as small as less than 1 μm, the grain boundary becomes small, and thus it becomes difficult for the dispersed component to be uniformly dispersed at the grain boundary between the tungsten crystals. On the other hand, if the average of the maximum ferret diameter of the tungsten crystal is larger than 100 μm, the strength as a sintered body is lowered. Therefore, the average maximum ferret diameter of the tungsten crystal is preferably 1 to 100 μm, and more preferably 10 to 60 μm.

From the viewpoint of uniform dispersion, the average value of the maximum ferret diameter of the dispersion component such as Zr, ZrO ₂ , ZrC, or C is preferably smaller than the average value of the maximum ferret diameter of the tungsten crystal. Specifically, it is preferable that B / A ≦ 0.5 when the average value of the maximum ferret diameter of the tungsten crystal is A (μm) and the average value of the maximum ferret diameter of the dispersed component is B (μm). . A dispersion component such as Zr, ZrO ₂ , ZrC, or C exists at the grain boundary between tungsten crystals, and functions as an emitter material or a grain boundary reinforcing material. By reducing the average particle size of the dispersed component to ½ or less of the average crystal particle size of tungsten, the dispersed component can be easily dispersed uniformly at the grain boundary of the tungsten crystal, and the characteristic variation can be reduced.

The tungsten alloy parts as described above are preferably used for at least one of discharge lamp parts, transmitter tube parts, and magnetron parts.

Examples of parts for discharge lamps include cathode electrodes, electrode support rods, and coil parts used for discharge lamps. An example of a discharge lamp cathode electrode is shown in FIGS. In the figure, 1 is a cathode electrode, 2 is an electrode body, and 3 is an electrode tip. The cathode electrode 1 is formed of a tungsten alloy sintered body. The tip of the electrode tip 3 may be a truncated cone as shown in FIG. 1, or the tip may be a cone as shown in FIG. If necessary, the tip is polished. The electrode body 2 is preferably cylindrical with a diameter of 2 to 35 mm and a length of 10 to 600 mm.

Fig. 3 shows an example of a discharge lamp. In the figure, 1 is a cathode electrode, 4 is a discharge lamp, 5 is an electrode support rod, and 6 is a glass tube. In the discharge lamp 4, the pair of cathode electrodes 1 are arranged so that the electrode tip portions face each other. The cathode electrode 1 is joined to the electrode support bar 5. A phosphor layer (not shown) is provided on the inner surface of the glass tube 6. The glass tube 6 is filled with mercury, halogen, argon gas (or neon gas) or the like as necessary. When the tungsten alloy component of the embodiment is used as the electrode support rod 5, the entire electrode support rod may be the tungsten alloy of the embodiment, or the tungsten alloy of the embodiment is used as a portion to be joined to the cathode electrode, and the remaining portion. Alternatively, a shape in which another lead material is joined may be used.

Depending on the type of discharge lamp, there is an electrode that has a coil component attached to an electrode support rod. It is also possible to apply the tungsten alloy of the embodiment to this coil component.

The discharge lamp of the embodiment uses the tungsten alloy part of the embodiment. The type of the discharge lamp is not particularly limited, and can be applied to both a low pressure discharge lamp and a high pressure discharge lamp. Examples of the low pressure discharge lamp include various arc discharge type discharge lamps such as general lighting, special lighting used for roads and tunnels, paint curing devices, UV curing devices, sterilizing devices, and light cleaning devices such as semiconductors. High pressure discharge lamps include water and sewage treatment equipment, general lighting, outdoor lighting for stadiums, UV curing equipment, exposure equipment for semiconductors and printed circuit boards, wafer inspection equipment, high pressure mercury lamps for projectors, metal halide lamps, A high pressure mercury lamp, a xenon lamp, a sodium lamp, etc. are mentioned.

The tungsten alloy part of the embodiment is also suitable for a transmission pipe part. Examples of the transmission tube component include a filament or a mesh grid. The mesh grid may be obtained by knitting a wire material in a mesh shape or by forming a plurality of holes in a sintered body plate. Since the transmission tube of the embodiment uses the tungsten alloy component of the embodiment as a transmission tube component, the emission characteristics and the like are good.

The tungsten alloy part of the embodiment is also suitable for a magnetron part. Examples of magnetron parts include coil parts. FIG. 4 shows a cathode structure for a magnetron as an example of a magnetron component. In the figure, 7 is a coil component, 8 is an upper support member, 9 is a lower support member, 10 is a support rod, and 11 is a magnetron cathode assembly. The upper support member 8 and the lower support member 9 are integrated via a support bar 10. A coil component 7 is disposed around the support rod 10 and integrated with the upper support member 8 and the lower support member 9. Such a magnetron component is suitable for a microwave oven. The coil component is preferably made of a tungsten wire having a wire diameter of 0.1 to 1 mm. The diameter of the coil component is preferably 2 to 6 mm. When the tungsten alloy part of the embodiment is used for a magnetron part, it exhibits excellent emission characteristics and high temperature strength. Therefore, the reliability of the magnetron using it can be improved.

Next, a method for manufacturing the tungsten alloy part of the embodiment will be described. The manufacturing method of the tungsten alloy component of the embodiment is not particularly limited as long as it has the above-described configuration, but the following method can be given as an efficient manufacturing method.

First, a tungsten powder as a raw material is prepared. The tungsten powder preferably has an average particle size of 1 to 10 μm. If the average particle size is less than 1 μm, the tungsten powder tends to aggregate and it is difficult to uniformly disperse the ZrO ₂ component. If the average grain size exceeds 10 μm, the average crystal grain size as a sintered body may exceed 100 μm. The purity of the tungsten powder is preferably 99.0 wt% or more, more preferably 99.9 wt% or more, although it depends on the application.

Next, ZrO ₂ powder is prepared as the Zr component, and ZrC powder is prepared as the ZrC component. Instead of ZrC powder, a mixture of Zr powder and carbon powder may be used. Further, instead of the ZrC powder alone, it is possible to mix ZrC powder with one or two kinds of Zr powder or carbon powder. Among these, it is preferable to use ZrO ₂ powder or ZrC powder. ZrC powder is preferable because part of the carbon decomposes and reacts with impurity oxygen in the tungsten powder in the sintering step, and becomes carbon dioxide which is released out of the system and contributes to the homogenization of the tungsten alloy. When a mixed powder of Zr powder and carbon powder is used, the load of the manufacturing process increases because both Zr powder and carbon powder are uniformly mixed. Moreover, since metal Zr is easy to oxidize, it is preferable to use ZrC powder.

As will be described later, the primary particles of the ZrO ₂ powder preferably have an average particle size of 15 μm or less, and more preferably 0.5 to 5 μm. When the average particle size is less than 0.5 μm, the aggregation of the ZrO ₂ powder is large and it is difficult to uniformly disperse. When the average particle diameter exceeds 15 μm, it is difficult to uniformly disperse the tungsten crystal grain boundaries. The ZrC powder preferably has an average particle size of 0.5 to 5 μm. When the average particle size is less than 0.5 μm, the aggregation of ZrC powder is large and it is difficult to uniformly disperse. When the average particle diameter exceeds 5 μm, it is difficult to uniformly disperse the tungsten crystal grain boundaries. From the viewpoint of uniform dispersion, it is preferable that the average particle diameter of the ZrO ₂ powder or the ZrC powder ≦ the average particle diameter of the tungsten powder.

As described above, when the Zr content of the ZrO ₂ powder, the ZrC powder, and the Zr powder is 100 parts by mass, the Hf content is preferably 15 parts by mass or less, and more preferably 10 parts by mass or less. The smaller the amount of Hf, the better. However, since high purity of the raw material causes an increase in cost, the amount of Hf is more preferably 0.1 to 3 parts by mass.

If necessary, at least one dope material selected from the group consisting of K, Si and Al is added. The amount added is preferably 0.01 wt% or less.

Next, each raw material powder is uniformly mixed. The mixing step is preferably performed using a mixer such as a ball mill. The mixing step is preferably performed for 8 hours or longer, more preferably 20 hours or longer. If necessary, it may be mixed with an organic binder or an organic solvent to form a slurry. You may perform a granulation process as needed.

Next, press with a mold to produce a compact. A degreasing process is performed to a molded object as needed. Next, a sintering process is performed. The sintering step is preferably performed in an inert atmosphere such as hydrogen or nitrogen or in a vacuum. Sintering is preferably performed at a temperature of 1400 to 3000 ° C. for 1 to 20 hours. If the sintering temperature is less than 1400 ° C. or the sintering time is less than 1 hour, the sintering is insufficient and the strength of the sintered body is lowered. If the sintering temperature exceeds 3000 ° C. or the sintering time exceeds 20 hours, the tungsten crystal may grow too much. By performing sintering in hydrogen, an inert atmosphere, or in a vacuum, carbon on the surface of the sintered body can be easily released out of the system. Sintering can be performed by electric current sintering, atmospheric pressure sintering, pressure sintering, etc., and is not particularly limited.

Next, a process for processing the sintered body into a part is performed. Examples of the processing process include a forging process, a rolling process, a drawing process, a cutting process, and a polishing process. A coiling process is mentioned when making it a coil component. In the case of producing a mesh grid as a transmission tube component, a step of assembling filaments into a mesh shape can be mentioned.

Next, the processed parts are subjected to strain relief heat treatment as necessary. The strain relief heat treatment is preferably performed in the range of 1300 to 2500 ° C. in an inert atmosphere or vacuum. By performing the strain relief heat treatment, it is possible to relieve internal stress generated in the processing step for the component and improve the strength of the component.

Tungsten alloy part embodiment contains 0.1 ~ 5 wt% of Zr in terms of ZrO _2, and is preferably the primary particles of ZrO ₂ particles is less than or equal to the average particle size of 15 [mu] m.

The tungsten alloy part preferably contains two kinds of ZrO ₂ and Zr. For ZrO ₂ (hafnium oxide), the atomic ratio of O / Zr is not limited to 2, and may be in the range of 1.6-2. Zr is contained in an amount of 0.1 to 5 wt% in terms of ZrO ₂ (O / Zr atomic ratio = 2). Zr is a component that functions as an emitter material in an electrode component for a discharge lamp. If the Zr content is less than 0.1 wt% in terms of ZrO ₂ , the emission characteristics are insufficient. If Zr exceeds 5 wt%, the strength may be lowered. Therefore, Zr is preferably 0.3 to 3.0 wt% in terms of ZrO ₂ , and more preferably 0.5 to 2.5 wt%.

ZrO ₂ exists in the form of particles, and the primary particles of ZrO ₂ preferably have an average particle size of 15 μm or less. ZrO ₂ particles exist at the grain boundaries between tungsten crystal particles. For this reason, if the ZrO ₂ particles are too large, the gap between the tungsten crystal particles is enlarged, which causes a decrease in density and strength. When ZrO ₂ particles exist at the grain boundaries between tungsten crystal particles, they function not only as an emission material but also as a dispersion strengthening material, which is advantageous in improving the strength of electrode parts.

The primary particles of the ZrO ₂ particles preferably have an average particle diameter of 5 μm or less and a maximum diameter of 15 μm or less. Further, the primary particles of the ZrO ₂ particles preferably have an average particle size of 0.1 μm or more and 3 μm or less and a maximum diameter of 1 μm or more and 10 μm or less. Small ZrO ₂ particles having an average particle diameter of less than 0.1 μm or a maximum diameter of less than 1 μm may disappear quickly due to exhaustion due to emission. In order to extend the life as an electrode, the ZrO ₂ particles preferably have an average particle diameter of 0.1 μm or more or a maximum diameter of 1 μm or more.

The dispersion state of ZrO ₂ particles in the tungsten alloy part is preferably in the range of 2 to 30 on an arbitrary straight line having a length of 200 μm. When the number of ZrO ₂ particles is less than 2 (0 to 1) per 200 μm long straight line, ZrO ₂ particles are partially reduced, resulting in a large variation in emissions. On the other hand, if the number of ZrO ₂ particles exceeds 30 (31 or more) per straight line having a length of 200 μm (31 or more), ZrO ₂ particles may be excessively increased in part, which may cause adverse effects such as strength reduction. The dispersion state of ZrO ₂ particles is examined by magnifying and photographing an arbitrary cross section of the tungsten alloy. The magnification of the enlarged photograph is 1000 times or more. An arbitrary straight line having a length of 200 μm (line thickness: 0.5 mm) is drawn on the enlarged photograph, and the number of ZrO ₂ particles present on the line is counted.

The secondary particles of ZrO ₂ preferably have a maximum diameter of 100 μm or less. The secondary particles of ZrO ₂ are aggregates of primary particles. If the secondary particles are larger than 100 μm, the strength of the tungsten alloy part is lowered. Therefore, the maximum diameter of the secondary particles of the ZrO ₂ particles is preferably as small as 100 μm or less, 50 μm or less, and further 20 μm or less.

Among Zr components, Zr (metal Zr) has various dispersion states.
In the first dispersion state, the metal Zr exists as particles. The metal Zr particles are present at the grain boundaries between the tungsten crystal particles in the same manner as the ZrO ₂ particles. By being present at the grain boundaries between the tungsten crystal particles, the metal Zr particles also function as an emission material and a dispersion strengthening material. Therefore, the primary particles of the metal Zr preferably have an average particle size of 15 μm or less, more preferably 10 μm or less, and further preferably 0.1 to 3 μm. The primary particle of the metal Zr preferably has a maximum diameter of 15 μm or less, and more preferably 10 μm or less. When producing a tungsten alloy, ZrO ₂ particles and metal Zr particles may be mixed in advance, or metal Zr particles may be generated by deoxidizing the ZrO ₂ particles during the manufacturing process. If a method of deoxidizing ZrO ₂ particles is used, it is preferable because oxygen in tungsten is also released from the system. If deoxidation can be performed, the electrical resistance of the tungsten alloy can be lowered, so that the conductivity of the electrode is improved.

In the second dispersion state, metal Zr is present on the surface of the ZrO ₂ particles. Similar to the first dispersion state, when a sintered body of tungsten alloy is produced, oxygen is deoxidized from the surface of the ZrO ₂ particles, and a metal Zr film is formed on the surface. Even ZrO ₂ particles with metal Zr coating exhibit excellent emission characteristics. The primary particles of ZrO ₂ with a metal Zr coating preferably have an average particle size of 15 μm or less, more preferably 10 μm or less, and even more preferably 0.1 to 3 μm. The primary particles of ZrO ₂ with a metal Zr coating preferably have a maximum diameter of 15 μm or less, and more preferably 10 μm or less.

In the third dispersed state, part or all of the metal Zr is solid-solved in tungsten. Metal Zr forms a solid solution with tungsten. By forming a solid solution, the strength of the tungsten alloy can be improved. The presence or absence of solid solution can be determined by XRD analysis. First, the Zr component and oxygen content are measured. The content of Zr and oxygen is converted to ZrOx, and it is confirmed that x <2. Next, XRD analysis is performed to confirm that no metal Zr peak is detected. Thus, although the ZrOx x is smaller than 2 and there is zirconium which is not stoichiometric zirconium oxide, the fact that the peak of the metal Zr is not detected means that the metal Zr is dissolved in tungsten. Means that

On the other hand, when Z of ZrOx is smaller than 2 and there is zirconium which is not stoichiometric zirconium oxide, and the peak of metal Zr is detected, metal Zr is not dissolved and the tungsten crystals are not dissolved. It means the first dispersed state existing at the grain boundary. The second dispersion state can be analyzed using EPMA (electron beam microanalyzer) or TEM (transmission electron microscope).

The dispersion state of the metal Zr may be any one of the first dispersion state, the second dispersion state, and the third dispersion state, or a combination of two or more.

When the total content of Zr is 100 parts by mass, the proportion of Zr that is ZrO ₂ particles is preferably 30 to 98 parts by mass. All of Zr may be ZrO ₂ particles. With ZrO ₂ particles, emission characteristics can be obtained. On the other hand, by dispersing the metal Zr, the conductivity and strength of the tungsten alloy can be improved. However, if all of Zr is metal Zr, emission characteristics and high-temperature strength are lowered. Metal Zr has a melting point of 1850 ° C., ZrO ₂ has a melting point of 2720 ° C., and metal tungsten has a melting point of 3400 ° C. Since ZrO ₂ has a melting point higher than that of metal Zr, the tungsten alloy component containing ZrO ₂ has improved high-temperature strength. Moreover, since the surface current density of ZrO ₂ is substantially equal to that of ThO ₂ , a current equivalent to that of the thorium oxide-containing tungsten alloy component can be passed through the tungsten alloy component of the embodiment. Therefore, when the tungsten alloy component of the embodiment is applied to an electrode of a discharge lamp, a current density equivalent to that of a thorium oxide-containing tungsten alloy electrode can be set, so that a design change such as a control circuit is unnecessary. From these viewpoints, when the total content of Zr components is 100 parts by mass, the content of Zr constituting ZrO ₂ is preferably 30 to 98 parts by mass, and more preferably 60 to 95 parts by mass. preferable.

The contents of ZrO ₂ and metal Zr in the tungsten alloy can be analyzed as follows. The total amount of Zr in the tungsten alloy is measured by ICP analysis. Next, the total amount of oxygen in the tungsten alloy is measured by an inert gas melting-infrared absorption method. When the tungsten alloy is a binary system of tungsten and Zr, it can be considered that the total amount of oxygen measured is substantially all ZrO ₂ . Therefore, the ZrO ₂ amount can be calculated based on the measured total Zr amount and total oxygen amount. In the case of this method, the amount of ZrO ₂ is calculated with O / Zr = 2.

Regarding the size of the ZrO ₂ particles, an enlarged photograph of an arbitrary cross section of the tungsten alloy sintered body is taken, and the longest diagonal of the ZrO ₂ particles existing in the cross section is measured to obtain the particle size of the primary particles of ZrO ₂ . This measurement is performed on 50 ZrO ₂ particles, and the average value is defined as the average particle size of the primary particles of ZrO ₂ . Among the particle diameters of ZrO ₂ primary particles (longest diagonal line), the maximum value is the maximum diameter of the primary particles of ZrO ₂ .

The tungsten alloy component of the embodiment may contain 2 wt% or less of at least one element selected from the group consisting of Ti, V, Nb, Ta, Mo and rare earth elements. At least one element selected from the group consisting of Ti, V, Nb, Ta, Mo and rare earth elements exists in any form of a simple metal, an oxide, and a carbide. You may contain these 2 or more types of elements. Even when two or more elements are contained, the total is preferably 2 wt% or less. These elements mainly function as a dispersion strengthening material. Since ZrO ₂ particles function as an emission material, they are consumed when the discharge lamp is used for a long time. On the other hand, since Ti, V, Nb, Ta, Mo, and rare earth elements have weak emission characteristics, they are less consumed by emission and can maintain their function as a dispersion strengthening material over a long period of time. Although the minimum of content of these elements is not specifically limited, It is preferable that it is 0.01 wt% or more. Of these elements, rare earth elements are preferred. Rare earth elements have a large atomic radius of 0.16 nm or more, which is advantageous for increasing the surface current density. In other words, it is preferable to use a metal simple substance or an element thereof containing an element having an atomic radius of 0.16 nm or more as the dispersion strengthening material.

FIG. 5 and FIG. 6 show an example of the electrode component for the discharge lamp of the embodiment. In the figure, 21 is a discharge lamp electrode part, 22 is a discharge lamp electrode part having a tapered tip part, 23 is a tip part, and 24 is a body part. The discharge lamp electrode part 21 has a cylindrical shape, and a tip part 23 thereof is processed into a tapered shape to form a discharge lamp electrode part 22. The discharge lamp electrode component 21 before processing into a tapered shape is usually a cylindrical shape, but may be a quadrangular prism shape.

It is preferable that the electrode component for a discharge lamp has a tip portion having a tapered tip and a cylindrical body portion. The taper shape, that is, the shape having a sharp tip, improves the characteristics as an electrode component for a discharge lamp. As shown in FIG. 6, the ratio of the length of the front end portion 23 and the body portion 24 is not particularly limited, and is appropriately set according to the application.

The wire diameter φ of the discharge lamp electrode component is preferably 0.1 to 30 mm. If the thickness is less than 0.1 mm, the strength as an electrode part cannot be maintained, and there is a possibility that the electrode part may be broken when assembled into a discharge lamp, or may be broken when the tip is tapered. On the other hand, if it exceeds 30 mm, it becomes difficult to control the uniformity of the tungsten crystal structure as described later.

When the crystal structure of the transverse section (radial section) of the body part is observed, the area ratio of tungsten crystals having a crystal grain size of 1 to 80 μm per unit area (for example, 300 μm × 300 μm) is 90% or more. preferable. FIG. 7 shows an example of a cross section of the body part. In the figure, 24 is a body part and 25 is a transverse section. In order to measure the crystal structure of the cross section, an enlarged photograph of the radial cross section at the center of the length of the body part is taken. Note that, when the wire diameter is small and a unit area of, for example, 300 μm × 300 μm cannot be imaged in one field of view, an arbitrary cross section is imaged multiple times. In the enlarged photograph, the longest diagonal line among the tungsten crystal particles existing in the cross section is defined as the maximum diameter. In the cross section, the area ratio of tungsten crystal particles whose maximum diameter is in the range of 1 to 80 μm is calculated.

The area ratio of tungsten crystals having a crystal grain size of 1 to 80 μm per unit area of the cross section of the body portion is 90% or more. This means that a small tungsten crystal having a crystal grain size of less than 1 μm and a large tungsten having a crystal grain size of more than 80 μm. Indicates that there are few crystals. If there are too many tungsten crystals of less than 1 μm, the grain boundaries between tungsten crystal particles become too small. If the proportion of ZrO ₂ particles in the tungsten crystal grain boundary increases, a large defect occurs when the ZrO ₂ particles are consumed due to emission, and the strength of the tungsten alloy decreases. On the other hand, when there are many large tungsten crystal grains exceeding 80 μm, the grain boundary becomes too large and the strength of the tungsten alloy is lowered. The area ratio of tungsten crystals having a crystal grain size of 1 to 80 μm per unit area of the cross section of the body portion is preferably 96% or more, and more preferably 100%.

The average particle diameter of the tungsten crystal particles in the cross section is preferably 50 μm or less, more preferably 20 μm or less. The average aspect ratio of the tungsten crystal grains in the cross section is preferably less than 3. The aspect ratio is calculated as follows. An enlarged photograph of a unit area (for example, 300 μm × 300 μm) is taken, the maximum diameter (ferret diameter) of the tungsten crystal particles existing in the cross section is the long diameter L, and the particle diameter obtained by vertically extending from the center of the long diameter L is the short diameter S. , Major axis L / minor axis S = aspect ratio. This measurement is performed on 50 tungsten crystal grains, and the average value is defined as the average aspect ratio. Further, (major axis L + minor axis S) / 2 = particle diameter, and an average value of 50 tungsten crystal particles is defined as an average particle diameter.

When the crystal structure of the longitudinal section of the body part is observed, the area ratio of tungsten crystals having a crystal grain size of 2 to 120 μm per unit area (for example, 300 μm × 300 μm) is preferably 90% or more. FIG. 8 shows an example of a longitudinal section. In the figure, 24 is a body part and 26 is a longitudinal section. In order to measure the crystal structure of the longitudinal section, an enlarged photograph of the longitudinal section passing through the center of the diameter of the body part is taken. When a unit area of, for example, 300 μm × 300 μm cannot be photographed in one field of view, an arbitrary longitudinal section is photographed a plurality of times. In the enlarged photograph, the longest diagonal line among the tungsten crystal particles existing in the cross section is defined as the maximum diameter. In the cross section, the area ratio of tungsten crystal particles whose maximum diameter is in the range of 2 to 120 μm is calculated.

The area ratio of tungsten crystals having a crystal grain size of 2 to 120 μm per unit area of the longitudinal section of the body portion is 90% or more, which means that a small tungsten crystal having a crystal grain size of less than 2 μm and a large tungsten having a crystal grain size of more than 120 μm Indicates that there are few crystals. When there are too many tungsten crystals less than 2 micrometers, the grain boundary between tungsten crystal particles will become too small. If the proportion of ZrO ₂ particles in the tungsten crystal grain boundary increases, a large defect occurs when the ZrO ₂ particles are consumed due to emission, and the strength of the tungsten alloy decreases. On the other hand, when there are many large tungsten crystal grains exceeding 120 μm, the grain boundary becomes too large and the strength of the tungsten alloy is lowered. The area ratio of tungsten crystals having a crystal grain size of 2 to 120 μm per unit area of the longitudinal section of the body portion is preferably 96% or more, and more preferably 100%.

The average particle diameter of tungsten crystal particles in the longitudinal section is preferably 70 μm or less, more preferably 40 μm or less. The average aspect ratio of the tungsten crystal particles in the longitudinal section is preferably 3 or more. The method for measuring the average particle diameter and the average aspect ratio is the same as the method described for the cross section.

As described above, by controlling the size of the tungsten crystal particles and the size and ratio of the ZrO ₂ particles, it is possible to provide a tungsten alloy having excellent discharge characteristics and strength, particularly high-temperature strength. Therefore, the characteristics of the discharge lamp electrode component are also improved.

The tungsten alloy part preferably has a relative density of 95.0% or more, more preferably 98.0% or more. If the relative density is less than 95.0%, bubbles may increase and adverse effects such as strength reduction and partial discharge may occur. The relative density is obtained from the measured density and the theoretical density by the Archimedes method by calculation of (actual density / theoretical density) × 100 (%) = relative density. The theoretical density is obtained by calculation from the density and mass ratio of known components. Here, the density of the tungsten 19.3 g / cm ^3, the density of zirconium 6.51 g / cm ^3, the density of the zirconium oxide is 6.52 g / cm ^3. For example, in the case of a tungsten alloy composed of 1 wt% ZrO ₂ , 0.2 wt% Zr, and the balance tungsten, 6.52 × 0.01 + 6.51 × 0.002 + 19.3 × 0.988 = 19.146662 g / cm ³ is the theoretical density. become. When calculating the theoretical density, it is not necessary to consider the presence of impurities.

The tungsten alloy component of the embodiment preferably has a Vickers hardness Hv of 330 or more, and more preferably within a range of Hv 330 to 700. If the Vickers hardness is less than Hv330, the tungsten alloy is too soft and the strength is lowered. On the other hand, if it exceeds Hv700, the tungsten alloy is too hard and it is difficult to process the tip into a tapered shape. On the other hand, if it is too hard, in the case of an electrode part having a long body part, there is a possibility that it is not flexible and easily breaks. If the Vickers hardness Hv is 330 or more, the three-point bending strength of the tungsten alloy can be increased to 400 MPa or more.

When the tungsten alloy part of the embodiment is applied to an electrode for a discharge lamp, the surface roughness Ra is preferably 5 μm or less. In particular, the tip has a surface roughness Ra of preferably 5 μm or less, more preferably 3 μm or less. If the surface irregularities are large, the emission characteristics will deteriorate.

The tungsten alloy parts as described above can be applied to various discharge lamps and are not particularly limited, such as a low pressure discharge lamp and a high pressure discharge lamp. Therefore, a long life can be achieved even when a large voltage of 100 V or higher is applied. The wire diameter of the body part is in the range of 0.1 to 30 mm, the wire diameter is 0.1 mm to 3 mm thin size, 3 mm to 10 mm medium size, 10 mm to 30 mm thick Applicable up to. The length of the electrode body is preferably 10 to 600 mm.

Fig. 9 shows an example of a discharge lamp. In the figure, reference numeral 22 denotes an electrode component (tip portion has been tapered), 27 denotes a discharge lamp, 28 denotes an electrode support rod, and 29 denotes a glass tube. The discharge lamp 27 arranges the pair of electrode parts 22 so that the electrode tip portions face each other. The electrode component 22 is joined to the electrode support rod 28. A phosphor layer (not shown) is provided on the inner surface of the glass tube 29. Inside the glass tube 29, mercury, halogen, argon gas (or neon gas) or the like is sealed as necessary.

The discharge lamp of the embodiment uses the tungsten alloy part of the embodiment. The type of the discharge lamp is not particularly limited, and can be applied to both a low pressure discharge lamp and a high pressure discharge lamp. Examples of the low-pressure discharge lamp include various arc discharge type discharge lamps such as general lighting, special lighting used for roads and tunnels, paint curing devices, UV curing devices, sterilization devices, and semiconductor photo-cleaning devices. High-pressure discharge lamps include water and sewage treatment equipment, general lighting, outdoor lighting for stadiums, UV curing equipment, exposure equipment for semiconductors and printed circuit boards, wafer inspection equipment, high-pressure mercury lamps for projectors, metal halide lamps, ultra-high pressure, etc. A mercury lamp, a xenon lamp, a sodium lamp, etc. are mentioned. Since the strength of the tungsten alloy is improved, it can be applied to a field involving movement (vibration) such as an automobile discharge lamp.

Next, the manufacturing method will be described. As long as the tungsten alloy component of the embodiment has the above-described configuration, the manufacturing method is not particularly limited, but examples of the manufacturing method for obtaining efficiently include the following.

First, a tungsten alloy powder containing a Zr component is prepared. A ZrO ₂ powder is prepared as a Zr component. The primary particles of the ZrO ₂ powder preferably have an average particle size of 15 μm or less, and more preferably have an average particle size of 5 μm or less. It is preferable to use a sieve to remove in advance those exceeding the maximum diameter of 15 μm. When it is desired to reduce the maximum diameter to 10 μm or less, large ZrO ₂ particles are removed using a sieve having a predetermined mesh diameter. Even when it is desired to remove ZrO ₂ particles having a small particle diameter, they are removed using a sieve having a predetermined mesh diameter. Prior to sieving, it is preferable to pulverize the ZrO ₂ particles with a ball mill or the like. By performing the pulverization step, the aggregates can be broken, so that it is easy to control the particle size by sieving.

Next, metallic tungsten powder is mixed. The metal tungsten powder preferably has an average particle size of 0.5 to 10 μm. The metal tungsten powder preferably has a purity of 98.0 wt% or more, an oxygen content of 1 wt% or less, and an impurity metal component of 1 wt% or less. Similarly to the ZrO ₂ particles, it is preferable that the particles are pulverized in advance by a ball mill or the like, and small particles and large particles are removed by a sieving step.

Metal tungsten powder is added so that the Zr content is 0.1 to 5 wt% in terms of ZrO ₂ . A mixed powder of ZrO ₂ particles and metal tungsten powder is put in a mixing container, and the mixing container is rotated to mix uniformly. At this time, a cylindrical container is used as the mixing container, and the mixing container can be smoothly mixed by rotating in the circumferential direction. Through this step, a tungsten powder containing ZrO ₂ particles can be prepared. Further, a small amount of carbon powder may be added in consideration of deoxidation during the sintering process described later.

Next, a compact is produced using the tungsten powder containing the obtained ZrO ₂ particles. When forming a molded body, a binder is used as necessary. In the case of forming a cylindrical shaped body, the diameter is preferably 0.1 to 40 mm. Moreover, when cutting a molded object from a plate-shaped sintered compact so that it may mention later, the size of a molded object is arbitrary. Moreover, the length (thickness) of a molded object is arbitrary.

Next, the compact is pre-sintered. Presintering is preferably performed at 1250 to 1500 ° C. By this step, a presintered body can be obtained. Next, the pre-sintered body is subjected to current sintering. The electric current sintering is preferably performed under the condition that the sintered body has a temperature of 2100 to 2500 ° C. If the temperature is less than 2100 ° C., sufficient densification cannot be achieved and the strength is lowered. When the temperature exceeds 2500 ° C., ZrO ₂ particles and tungsten particles grow too much, and the desired crystal structure cannot be obtained.

In another method, the molded body may be sintered at a temperature of 1400 to 3000 ° C. for 1 to 20 hours. If the sintering temperature is less than 1400 ° C. or the sintering time is less than 1 hour, the sintering is insufficient and the strength of the sintered body is lowered. If the sintering temperature exceeds 3000 ° C. or the sintering time exceeds 20 hours, the tungsten crystal may grow too much.

Examples of the sintering atmosphere include an inert atmosphere such as nitrogen and argon, a reducing atmosphere such as hydrogen, and a vacuum. In these atmospheres, the carbon of the ZrO ₂ particles is decarburized during the sintering process. Since impurity oxygen in the tungsten powder is removed together at the time of decarburization, the oxygen content in the tungsten alloy can be reduced to 1 wt% or less, and further to 0.5 wt% or less. When the oxygen content in the tungsten alloy is reduced, the conductivity is improved.

By this sintering step, a Zr-containing tungsten sintered body can be obtained. If the pre-sintered body is cylindrical, the sintered body is also a cylindrical sintered body (ingot). In the case of a plate-like sintered body, a cylindrical sintered body (ingot) can be obtained by a step of cutting to a predetermined size.

Next, the diameter of the cylindrical sintered body (ingot) is adjusted by forging, rolling, drawing, or the like. In this case, the processing rate is preferably in the range of 30 to 90%. This processing rate means that the processing rate = [(AB) / A] × where A is the cross-sectional area of the cylindrical sintered body before processing, and B is the cross-sectional area of the cylindrical sintered body after processing. 100%. The wire diameter is preferably adjusted by a plurality of processes. By performing the processing a plurality of times, it is possible to obtain a high-density electrode part by crushing the pores of the cylindrical sintered body before processing.

For example, a case where a cylindrical sintered body having a diameter of 25 mm is processed into a cylindrical sintered body having a diameter of 20 mm will be described. Processing rate since the cross-sectional area A of a circle having a diameter of 25mm 460.6mm ^2, the cross-sectional area B of the circle of diameter 20mm is 314 mm ² is, [(460.6-314) /460.6] × 100 = 32% It becomes. At this time, it is preferable to process from a diameter of 25 mm to a diameter of 20 mm by a plurality of drawing processes.

When the processing rate is as low as less than 30%, the crystal structure is not sufficiently extended in the processing direction, and it becomes difficult to make the tungsten crystal and the ZrO ₂ particles have a desired size. Further, if the processing rate is as small as less than 30%, the pores inside the cylindrical sintered body before processing may not be sufficiently crushed and may remain as they are. If the internal pores remain, it may cause a decrease in the durability of the cathode component. On the other hand, if the processing rate is larger than 90%, there is a possibility that the yield is lowered due to disconnection due to excessive processing. For this reason, the processing rate is preferably 30 to 90%, more preferably 35 to 70%. In addition, when the relative density of the sintered tungsten alloy is 95% or more, the processing is not necessarily performed at the above processing rate.

After processing the wire diameter of the sintered body to 0.1 to 30 mm, the electrode part can be produced by cutting to a required length. If necessary, the tip is processed into a tapered shape. Further, polishing, heat treatment (such as recrystallization heat treatment), and shape processing are performed as necessary.

The recrystallization heat treatment is preferably performed in a range of 1300 to 2500 ° C. in a reducing atmosphere, an inert atmosphere or a vacuum. By performing the recrystallization heat treatment, the effect of the strain relief heat treatment that relieves internal stress generated in the processing step for the electrode component can be obtained, and the strength of the component can be improved.

According to the manufacturing method as described above, the discharge lamp electrode component of the embodiment can be efficiently manufactured.

(Example 1)
As a raw material powder, ZrO ₂ powder (purity 99.0%) having an average particle diameter of 2 μm was added to tungsten powder (purity 99.99 wt%) having an average particle diameter of 2 μm so as to be 1.5 wt%. Note that the ZrO ₂ powder, impurity amount of Hf when the Zr amount is 100 parts by mass was 1.0 parts by mass.

The raw material powder was mixed with a ball mill for 10 hours to prepare a mixed raw material powder. Next, the mixed raw material powder was put into a mold to produce a molded body. The obtained molded body was subjected to furnace sintering in hydrogen at 1800 ° C. for 10 hours. By this step, a sintered body of 16 mm length × 16 mm width × 420 mm length was obtained.

A rod having a square or circular cross section was produced by forging or the like, and then a cylindrical sample having a diameter of 2.4 mm and a length of 150 mm was cut out. The sample was subjected to centerless polishing so that the surface roughness Ra was 5 μm or less. Next, a strain relief heat treatment at 1600 ° C. was performed in hydrogen.

Thereby, an electrode for measuring emission characteristics was produced as a tungsten alloy part according to Example 1, and the emission current was measured.

(Comparative Example 1)
A cathode component for a discharge lamp of the same size made of a tungsten alloy containing 2 wt% ThO ₂ was produced.

Regarding the tungsten alloy part according to Example 1, the content of ZrO ₂ , the carbon content of the surface portion and the central portion, and the average grain size of tungsten crystals were examined. The content of ZrO ₂ was analyzed by ICP analysis and inert gas melting-infrared absorption method to analyze the amount of Zr and the amount of oxygen, and converted to ZrOx. The carbon content in the surface portion and the central portion was measured by a combustion-infrared absorption method by cutting a sample for measurement from a range of 10 μm from the surface and from a cylindrical cross section. The average crystal grain size of the tungsten crystal particles is an average value obtained by measuring the crystal particle size of 100 tungsten crystal particles in an arbitrary cross-sectional structure. The results are shown in Table 1.

Next, the emission characteristics of the cathode component for a discharge lamp according to Example 1 and Comparative Example 1 were examined. The emission characteristics were measured by changing the applied voltage (V) to 100 V, 200 V, 300 V, and 400 V and measuring the emission current density (mA / mm ² ). The measurement was performed at an applied current load of 18 ± 0.5 A / W to the cathode component and an application time of 20 ms. The result is shown in FIG.

FIG. 10 indicates that the emission characteristics of Example 1 are superior to those of Comparative Example 1. Thus, it can be seen that the cathode part for the discharge lamp of Example 1 exhibits excellent emission characteristics without using thorium oxide, which is a radioactive substance. At the time of measurement, the cathode component was 2100 to 2200 ° C. For this reason, it turns out that the cathode component which concerns on Example 1 is excellent also in high temperature strength, a lifetime, etc.

(Examples 2 to 6)
Next, raw material mixed powders were prepared in which the addition amount of ZrO _2, the addition amount of ZrC, and the addition amount of K as a doping material were changed as shown in Table 2. Each raw material mixed powder was molded and sintered in hydrogen at 1500 to 1900 ° C. for 7 to 16 hours to obtain a sintered body. In Examples 2 to 3, the cut-out process was performed in the same manner as in Example 1 in the size of the sintered body. In Examples 4 to 5, a sintered compact having a diameter of 2.4 mm and a length of 150 mm was directly obtained by adjusting the size of the molded body. In Example 6, 0.5 wt% of ZrC powder (purity 99.0%) having an average particle diameter of 2 μm was added. Note that the ZrO ₂ powder, impurity amount of Hf when the Zr amount is 100 parts by mass was 1.0 parts by mass. Further, when the ZrO ₂ powder and the ZrC powder of Example 6 were used, the impurity Hf amount was 1.0 part by mass when the Zr amount was 100 parts by mass.

Each sample was subjected to centerless polishing to have a surface roughness Ra of 5 μm or less. Next, the tip was processed into a conical shape with an inclination angle of 45 °. Next, a strain relief heat treatment at 1400 to 1700 ° C. was performed in hydrogen. As a result, cathode components for discharge lamps according to Examples 2 to 5 were produced, and the same measurements as in Example 1 were performed. The results are shown in Table 3.

Next, the emission characteristics were evaluated under the same conditions as in Example 1. The results are shown in Table 4.

As can be seen from Table 4, all the cathode parts for the discharge lamp according to this example exhibited excellent characteristics. At the time of measurement, the cathode component was 2100 to 2200 ° C. Therefore, it can be seen that the cathode parts according to Examples 2 to 6 are excellent in high temperature strength and life. Incidentally, in Example 1 it was one containing two Zr and ZrO _2. Further, Example 6 contained three kinds of Zr, ZrO ₂ and ZrC.

(Examples 11 to 20, Comparative Example 11)
Tungsten powder (purity 99.0 wt% or more) and ZrO ₂ powder shown in Table 5 were prepared as raw material powder. Each powder was sufficiently loosened by a ball mill, and subjected to a sieving step as necessary so that the maximum diameter was a value shown in Table 5, respectively.

Next, tungsten powder and ZrO ₂ powder were mixed at a ratio shown in Table 6 and mixed again by a ball mill. Next, it shape | molded and the molded object was prepared. Next, the sintering process was performed under the conditions shown in Table 6. A sintered body of 16 mm long × 16 mm wide × 420 mm long was obtained.

Next, a cylindrical sintered body (ingot) was cut out from the obtained tungsten alloy sintered body, and the wire diameter was adjusted by appropriately combining forging, rolling, and drawing. The processing rate is as shown in Table 7. Moreover, after adjusting a wire diameter, it cut | disconnected to predetermined length, and processed the front-end | tip part into the taper shape. Thereafter, the surface was polished to a surface roughness Ra of Ra 5 μm or less. Next, recrystallization heat treatment at 1600 ° C. was performed in a hydrogen atmosphere. Thereby, the electrode part for discharge lamps was completed.

Next, enlarged photographs of the cross section and vertical section of the body part of each discharge lamp electrode part were taken, and the average particle diameter, maximum diameter, ratio of tungsten crystal particles, average particle diameter, and aspect ratio of the ZrO ₂ component were measured. . Regarding the enlarged photograph, a circumferential section and a longitudinal section passing through the center of the body part were cut out, and an arbitrary unit area of 300 μm × 300 μm was examined. The results are shown in Table 8.

Next, the ratio of ZrO _{2 in} the Zr component was measured for each discharge lamp electrode part. Further, the oxygen content, relative density (%), Vickers hardness (Hv), and three-point bending strength were determined.

The proportion of ZrO ₂ in the Zr component is determined by measuring the amount of Zr in the tungsten alloy by ICP analysis and the amount of carbon in the tungsten alloy by the combustion-infrared absorption method. It can be considered that the carbon in the tungsten alloy is ZrO ₂ . Therefore, the total amount of Zr detected is 100 parts by weight, the amount of Zr that becomes ZrO ₂ is converted, and the mass ratio is obtained. The oxygen content in the tungsten alloy was analyzed by an inert gas combustion-infrared absorption method. The relative density was obtained by dividing the measured density analyzed by the Archimedes method by the theoretical density. The theoretical density was determined by the above calculation. The Vickers hardness (Hv) was determined according to JIS-Z-2244. The three-point bending strength was determined according to JIS-R1601. The results are shown in Table 9.

The electrode part for a discharge lamp according to the present example had a high density and an excellent Vickers hardness (Hv). This is because a part of ZrO ₂ was deoxidized. In addition, the Zr component that is not ZrO ₂ is any one of those that have become metal Zr particles, those that have part of the surface of ZrO ₂ particles become metal Zr, and those that have become a solid solution of tungsten and hafnium. It was in a state.

(Examples 21 to 25)
Next, a tungsten powder and a ZrO ₂ powder similar to those in Example 12 were used, and a second component having a composition shown in Table 10 was prepared. An ingot was obtained by sintering the furnace at 2000 ° C. in a hydrogen atmosphere. The ingot was processed at a processing rate of 50% to obtain an electrode part having a wire diameter of 10 mm. Further, a recrystallization heat treatment at 1600 ° C. was performed in a hydrogen atmosphere. The same measurement was performed for each example. The results are shown in Tables 10-12.

As can be seen from Tables 10 to 12, by using the additive element, the dispersion strengthening function was strengthened, and the grain growth of the tungsten crystal was suppressed, so that the strength was improved.

(Examples 11A to 25A, Comparative Examples 11-1A to 11-2A and Comparative Example 12)
The emission characteristics of the electrode parts for discharge lamps of Examples 11 to 25, Comparative Example 11-1, and Comparative Example 11-2 were examined. The emission characteristics were measured by changing the applied voltage (V) to 100 V, 200 V, 300 V, and 400 V and measuring the emission current density (mA / mm ² ). The measurement was performed at an applied current load of 18 ± 0.5 A / W and an application time of 20 ms to the electrode parts for the discharge lamp.

As Comparative Example 12, a discharge lamp electrode part having a wire diameter of 8 mm made of a tungsten alloy containing 2 wt% ThO ₂ was produced. The results are shown in Table 13.

The discharge lamp electrode parts according to each example exhibited emission characteristics equal to or higher than those of Comparative Example 2 using thorium oxide, although thorium oxide was not used. At the time of measurement, the electrode parts were at 2100 to 2200 ° C. For this reason, the electrode components for discharge lamps according to the respective examples have excellent high temperature strength.

(Examples 26 to 28)
Next, the electrode parts for discharge lamps of Example 11, Example 13, and Example 18 were manufactured by the same manufacturing method except that the recrystallization heat treatment condition was changed to 1800 ° C. Example 26 (Example) 11 was changed to 1800 ° C.), Example 27 was changed to 1800 ° C. (Example 13), and Example 28 was changed to 1800. Prepared at a temperature changed to ℃). Similar measurements were made. The results are shown in Tables 14 and 15.

The electrode part for a discharge lamp according to this example had a high density, and also exhibited excellent values of Vickers hardness (Hv) and three-point bending strength. This is because a part of ZrO ₂ was deoxidized. Moreover, as a result of analyzing the Zr component which is not ZrO ₂ , both were solid solutions of tungsten and zirconium. That is, there are two types of Zr components, Zr and ZrO ₂ . For this reason, it has been found that when the recrystallization heat treatment temperature is set to 1700 ° C. or higher, the metal Zr is easily dissolved in tungsten. The emission characteristics were measured by the same method.

It was found that the emission characteristics are improved by dissolving all of the metal Zr in tungsten as described above. This is considered to be because the metal Zr is likely to be present on the surface of the tungsten alloy due to the solid solution.

Also, since it has excellent emission characteristics as described above, it can be used not only for electrode parts for discharge lamps but also for fields such as magnetron parts (coil parts) and transmission pipe parts (mesh grit) that require emission characteristics.

Claims (21)

1. A tungsten alloy part comprising tungsten and at least two components selected from the group consisting of Zr, ZrO ₂ , ZrC and C, and containing 0.1 to 5 wt% of Zr in terms of ZrO ₂ .
2. The tungsten alloy part according to claim 1, wherein Zr is contained in an amount of 0.1 to 3 wt% in terms of ZrO ₂ .
3. The tungsten alloy part according to claim 1 or 2, wherein the content of Zr and O is x <2 when converted to ZrO _x .
4. 4. The tungsten alloy part according to claim 1, wherein the content of Zr and O is 0 <x <2 when converted to ZrO _x . 5.
5. The tungsten alloy part according to any one of claims 1 to 4, further comprising 0.01 wt% or less of at least one element selected from the group consisting of K, Si and Al.
6. 6. The tungsten alloy component according to claim 1, wherein the content of Hf is 15 parts by mass or less when the content of Zr is 100 parts by mass.
7. 7. The tungsten alloy part according to claim 1, wherein the primary particles of the ZrO ₂ have an average particle size of 15 μm or less.
8. The tungsten alloy component according to claim 7, wherein the primary particles of the ZrO ₂ have an average particle size of 5 µm or less and a maximum diameter of 15 µm or less.
9. 9. The tungsten alloy part according to claim 7, wherein the secondary particles of ZrO ₂ have a maximum diameter of 100 μm or less.
10. The tungsten alloy component according to any one of claims 1 to 9, wherein at least a part of the metal Zr is solid-dissolved in tungsten.
11. The tungsten alloy part according to any one of claims 1 to 10, wherein metal Zr is present on a surface of the tungsten alloy part.
12. The tungsten alloy component according to any one of claims 1 to 11, wherein the content of Zr constituting ZrO ₂ is 30 to 98 parts by mass when the content of Zr is 100 parts by mass. .
13. The tungsten alloy part according to any one of claims 1 to 12, wherein the tungsten alloy part has a Vickers hardness Hv of 330 or more.
14. The tungsten alloy part according to any one of claims 1 to 13, wherein the tungsten alloy part has a wire diameter of 0.1 to 30 mm.
15. The tungsten alloy part according to any one of claims 1 to 13, wherein the tungsten alloy part contains a tungsten crystal having an average crystal grain size of 1 to 100 µm.
16. 16. The tungsten alloy part according to claim 15, wherein the area ratio of tungsten crystals having a crystal grain size of 1 to 80 μm per unit area of a cross section of the tungsten alloy part is 90% or more.
17. The tungsten alloy part according to claim 15 or 16, wherein an area ratio of tungsten crystals having a crystal grain size of 2 to 120 µm per unit area of a longitudinal section of the tungsten alloy part is 90% or more.
18. 18. The tungsten alloy part according to claim 1, wherein the tungsten alloy part is used for a discharge lamp part, a transmitter tube part, or a magnetron part.
19. 19. A discharge lamp characterized by using a tungsten alloy part according to claim 18.
20. 19. A transmission tube using a tungsten alloy part according to claim 18.
21. 19. A magnetron according to claim 18, wherein a tungsten alloy part is used.

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