JP5881740B2 - Tungsten alloy and tungsten alloy parts, discharge lamp, transmitter tube and magnetron using the same - Google Patents

Description

  Embodiments described herein relate generally to a tungsten alloy, a tungsten alloy part using the same, an electrode part for a discharge lamp, a discharge lamp, a transmission tube, and a magnetron.

  Tungsten alloy parts are used in various fields by utilizing 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 JP 2011-103240 A (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 Patent No. 4741190

  For example, discharge lamps, which are one type 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.

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

  The present invention is for addressing such problems, and does not use thorium, which is a radioactive substance, but is equivalent to or better than thorium-containing tungsten alloys, tungsten alloy parts using tungsten alloys, discharge lamps, and transmissions. The purpose is to provide a tube and a magnetron.

  According to the embodiment, a tungsten alloy containing a W component and a Ta component containing TaC is provided. The amount of the Ta component is in the range of 0.1 wt% to 5 wt% in terms of TaC, and more preferably in the range of 0.1 wt% to 3 wt% in terms of TaC. The average primary particle diameter of TaC particles is 15 μm or less.

  The tungsten alloy part of the embodiment is a tungsten alloy part containing 0.1 to 3 wt% of Ta in terms of TaC, and contains at least two of Ta, TaC, and C.

Further, Ta, when converted TaC _x the total amount of TaC and C, it is preferable that x <1. Further, Ta, when converted TaC _x the total amount of TaC and C, it is preferable and 0 <x <1. Further, Ta, when converted TaC _x the total amount of TaC and C, is preferably 0.001 <x <0.5.

  Further, when the carbon content of the surface portion of the tungsten alloy part is C1 (wt%) and the carbon content of the central portion is C2 (wt%), it is preferable that C1 <C2. Moreover, it is preferable to contain 0.01 wt% or less of at least one of K, Si, and Al. Further, when the Ta content is 100 parts by mass, the Nb content is preferably 5 parts by mass or less. The average crystal grain size of tungsten is preferably 1 to 100 μm.

  Further, it is preferably used for at least one of a discharge lamp part, a transmission tube part, and a magnetron part.

  In addition, the discharge lamp of the embodiment includes the tungsten alloy component of the embodiment. The transmission tube of the embodiment includes the tungsten alloy component of the embodiment. In addition, the magnetron of the embodiment includes the tungsten alloy component of the embodiment.

  The discharge lamp electrode component of the embodiment is a discharge lamp electrode component made of a tungsten alloy. The tungsten alloy contains a Ta component in an amount of 0.1 to 5 wt% in terms of TaC, and TaC particles are average grains in the Ta component. The diameter is 15 μm or less.

  The TaC particles preferably have an average particle diameter of 5 μm or less and a maximum diameter of 15 μm or less. Moreover, it is preferable that two types of Ta component exist, TaC and metal Ta. Further, the Ta component preferably has metal Ta on the surface of TaC particles. Alternatively, it is preferable that a part or all of the metal Ta among the Ta component is dissolved in tungsten. Moreover, when the total content of the Ta component is 100 parts by mass, the proportion of Ta that is TaC particles is preferably 0.1 to 50 masses. The tungsten alloy preferably contains 0.01 wt% or less of a doping material composed of at least one of K, Si, and Al. The tungsten alloy preferably contains 2 wt% or less of at least one of Ti, Zr, V, Nb, Hf, Mo, and rare earth elements. Moreover, it is preferable that a wire diameter is 0.1-30 mm. The tungsten alloy preferably has a Vickers hardness in the range of Hv 330 to 700. Moreover, it is preferable that the electrode component for discharge lamps has a front-end | tip part which made the front-end | tip a taper shape, and a cylindrical body part.

  Moreover, when the crystal structure of the cross section in the circumferential direction of the body portion is observed, it is preferable that 1 to 80 μm of the tungsten crystal per unit area of 300 μm × 300 μm is 90% or more. Further, when the crystal structure of the cross section in the side surface direction of the body part is observed, it is preferable that 2 to 120 μm of the tungsten crystal per unit area of 300 μm × 300 μm is 90% or more.

  Further, the discharge lamp of the embodiment is characterized by using the electrode component for a discharge lamp of the embodiment. Moreover, it is preferable that the applied voltage of a discharge lamp is 100V or more.

  Since the tungsten alloy of the embodiment does not contain thorium (including thorium oxide) which is a radioactive substance, there is no adverse effect on the environment. In addition, it has the same or better characteristics as the thorium-containing tungsten alloy. Therefore, tungsten alloy parts, electrode parts for discharge lamps, discharge lamps, transmitter tubes, and magnetrons using them can be made environmentally friendly products.

It is a figure which shows an example of the tungsten alloy component of 1st Embodiment. It is a figure which shows another example of the tungsten alloy component of 1st Embodiment. It is a figure which shows an example of the discharge lamp of 1st Embodiment. It is a figure which shows an example of the components for magnetrons of 1st Embodiment. It is a figure which shows an example of the electrode component for discharge lamps of 2nd Embodiment. It is a figure which shows another example of the electrode component for discharge lamps of 2nd Embodiment. It is a figure which shows an example of the circumferential direction cross section of the trunk | drum part of the electrode component for discharge lamps of 2nd Embodiment. It is a figure which shows an example of the side surface direction cross section of the trunk | drum part of the electrode component for discharge lamps of 2nd Embodiment. It is a figure which shows an example of the discharge lamp of 2nd Embodiment. It is a figure which shows the relationship of the emission current density-applied voltage of Example 1 and Comparative Example 1.

(First embodiment)
According to the first embodiment, a tungsten alloy containing a W component and a Ta component containing TaC is provided. The amount of the Ta component is in the range of 0.1 wt% to 3 wt% in terms of TaC. The Ta component contains at least TaC, and may contain a Ta-containing compound other than TaC, Ta alone, or the like. Examples of the Ta-containing compound include Ta ₂ O ₃ .

  The tungsten alloy part according to the embodiment is characterized in that in a tungsten alloy part containing a Ta component in an amount of 0.1 to 3 wt% in terms of TaC, at least two of Ta, TaC, and C are contained.

  By including the Ta (tantalum) component in an amount of 0.1 to 3 wt% in terms of TaC (tantalum carbide), characteristics such as emission characteristics and strength can be improved. That is, when the Ta component content is less than 0.1 wt% in terms of TaC, the effect of addition is insufficient, and when it exceeds 3 wt%, the characteristics are deteriorated. Moreover, it is preferable that Ta component content is 0.5-2.5 wt% in conversion of TaC.

Further, the TaC component contained in the tungsten alloy needs to contain at least two of Ta, TaC, and C. That is, as a TaC component, a TaC component is contained in any of a combination of Ta and TaC, a combination of Ta and C (carbon), a combination of TaC and C (carbon), and a combination of Ta, TaC and C (carbon). It is. When the melting points are compared, the metal Ta is 2990 ° C., the TaC is 3980 ° C., and the tungsten is 3400 ° C. (refer to Iwanami Shoten “Rikagaku Encyclopedia”). The melting point of metal thorium is 1750 ° C., and the melting point of thorium oxide (ThO ₂ ) is 3220 ± 50 ° C. Since tantalum has a higher melting point than thorium, the high-temperature strength can be made equal to or higher than that of thorium-containing tungsten alloy.

Further, Ta, when TaC _x terms the total amount of TaC and C (carbon) is preferably x <1. x <1 means that not all TaC components contained in the tungsten alloy are present as TaC, but a part thereof is metal Ta. The work function of the metal Ta is 4.25, which is larger than the work function of the metal Th. Therefore, it is considered that the emission characteristics are deteriorated. However, this is not a problem in applications such as discharge lamps. . Metal tantalum is an element effective in improving strength because it forms a solid solution with tungsten.

  Further, when the total amount of Ta, TaC and C is converted to TaCx, 0 <x <1 is preferable. x <1 is as described above. Moreover, 0 <x means that either TaC or C exists as a TaC component contained in the tungsten alloy. TaC 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. Further, when the total amount of Ta, TaC and C is converted to TaCx, it is preferable that 0.001 <x <0.5. Within this range, the metal Ta, TaC, or C exists in a well-balanced manner, and characteristics such as emission characteristics, strength, electrical resistance, and life are improved. More preferably, 0.010 ≦ x ≦ 0.050.

Moreover, the ICP analysis method and the combustion-infrared absorption method shall be used as a method for measuring the content of Ta, TaC, and C in the tungsten alloy part. If it is an ICP analysis method, Ta amount which totaled Ta amount of Ta and Ta amount of TaC can be measured. Moreover, the carbon amount which totaled the carbon amount of TaC, the carbon amount which exists independently, or the carbon amount which exists as another carbide | carbonized_material by a combustion-infrared absorption method can be measured. ICP analysis and combustion in embodiments - Ta amount by an infrared absorption method, and measuring the amount of C, shall be converted into TaC _x.

  Moreover, you may contain 0.01 wt% or less of at least 1 sort (s) 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. Further, the lower limit of the content of the dope material is not particularly limited, but is preferably 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.

  Further, when the Ta content is 100 parts by mass, the Nb content is preferably 5 parts by mass or less. This Ta content indicates the total amount of Ta and TaC. Since Nb (niobium) has a high melting point of 2470 ° C., there is little adverse effect even if it is contained in tungsten parts. Also, commercially available Ta powder and the like may contain several percent Nb depending on the grade of the powder. The use of high-purity Ta powder or high-purity TaC powder from which impurities are removed is effective for improving characteristics. On the other hand, increasing the purity of the raw material increases the cost. If the content of Nb (niobium) is 5 parts by mass or less when Ta part is 100 parts by weight, it is not necessary to deteriorate the characteristics more than necessary.

Further, when the carbon content of the surface portion of the tungsten alloy part is C1 (wt%) and the carbon content of the central portion is C2 (wt%), it is preferable that C1 <C2. The surface portion indicates a portion from the surface of the tungsten alloy to 20 μm. The central part is the central part in the cross section of the tungsten alloy part. This carbon amount is a total value of both carbon of a carbide such as TaC and carbon present alone, and is 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. In addition, a decrease in the amount of carbon in the surface portion means a state in which the amount of Ta in the surface portion relatively increases. For this reason, it is particularly effective when Ta is used as the emitter material.

  The average crystal grain size of tungsten is preferably 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. Further, by performing a forging process, a rolling process, a drawing process, and the like on the sintered body, it is easy to process the wire (including filaments), coil parts, and the like.

  Further, when the tungsten crystal is a sintered body, the crystal having an aspect ratio of less than 3 has an isotropic crystal structure of 90% or more. Further, when the drawing process is performed, a crystal having an aspect ratio of 3 or more becomes a flat crystal structure of 90% or more. In order to determine the grain size of the tungsten crystal, the crystal structure is taken with an enlarged photograph of a metal microscope or the like. The maximum ferret diameter is measured with one tungsten crystal in the image to obtain the particle diameter. This operation is performed for any 100 grains, and the average value is defined as the average crystal grain diameter.

  Also, 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 Ta, TaC or C uniform. The dispersed component is present at the grain boundary between the tungsten crystals. For this reason, 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, so that it is difficult to uniformly disperse the dispersed components. On the other hand, when the average of the maximum ferret diameter of the tungsten crystal exceeds 100 μm, the strength as a sintered body is lowered. Therefore, the average of the maximum ferret diameter of the tungsten crystal is preferably 1 to 100 μm, more preferably 10 to 60 μm.

  Further, from the viewpoint of uniform dispersion, the average value of the maximum ferret diameter of the dispersion component such as Ta, TaC or C is preferably smaller than the average value of the maximum ferret diameter of tungsten. Further, 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 dispersion component is B (μm), it is preferable that B / A ≦ 0.5. Dispersion components such as Ta, TaC or C exist at the grain boundaries between the tungsten crystals, and function 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 in the tungsten crystal grain boundary, and characteristic variation can be reduced.

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

  Examples of the discharge lamp component include a cathode electrode, an electrode support rod, and a coil component used for the discharge lamp. 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. Further, the tip 3 of the electrode may have a trapezoidal shape (conical truncated cone shape) as shown in FIG. 1, or a triangular shape (conical shape) as shown in FIG. If necessary, the tip is polished. The electrode body 2 is preferably a cylinder having a diameter of 2 to 35 mm, and the length of the electrode body 2 is preferably 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. In addition, a phosphor layer (not shown) is provided inside the glass tube 6. Further, inside the glass tube, mercury, halogen, argon gas (or neon gas) or the like is sealed as necessary.

  Further, 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 for the portion to be joined to the cathode electrode, and the rest This part may be shaped to be joined to another lead material.

  Further, depending on the type of the discharge lamp, there is a type in which a coil component is attached to an electrode support rod to form an electrode. It is also possible to apply the tungsten alloy of the embodiment to this coil component.

  In addition, the discharge lamp of the embodiment uses the tungsten alloy or the tungsten alloy component 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 light cleaning devices such as semiconductors. 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.

  Moreover, 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. In addition, the mesh grid may be one obtained by knitting a wire rod in a mesh shape, or one obtained 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.

  Moreover, the tungsten alloy component of the embodiment is also suitable for a magnetron component. 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 is 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 preferably has a wire diameter of 0.1 to 1 mm of the tungsten wire used. The diameter of the coil component is preferably 2 to 6 mm. The tungsten alloy component of the embodiment exhibits excellent emission characteristics and high temperature strength when used in a magnetron component. Therefore, the reliability of the magnetron using it can be improved.

  Next, the manufacturing method of the tungsten alloy and tungsten alloy component of embodiment is demonstrated. A manufacturing method of the tungsten alloy and the tungsten alloy component of the embodiment is not particularly limited as long as the tungsten alloy and the tungsten alloy part have the above-described configuration, but examples of the efficient manufacturing method include the following methods.

  First, a tungsten powder as a raw material is prepared. The tungsten powder preferably has an average particle size of 1 to 10 μm. When the average particle size is less than 1 μm, the tungsten powder is likely to aggregate and it is difficult to uniformly disperse the TaC component. On the other hand, if it exceeds 10 μm, the average crystal grain size as a sintered body may exceed 100 μm. Further, the purity is preferably 99.0 wt% or more, more preferably 99.9 wt% or more, although it may be used for the intended purpose.

  Next, TaC powder is prepared as a TaC component. Further, a mixture of Ta powder and carbon powder may be used instead of TaC powder. Further, instead of TaC powder alone, TaC powder mixed with one or two kinds of Ta powder or carbon powder may be used. In this, it is preferable to use TaC powder. TaC powder is preferable because part of carbon decomposes and reacts with impurity oxygen in tungsten powder in the sintering process, and is released out of the system as carbon dioxide, contributing to the homogenization of the tungsten alloy. When dealing with a mixed powder of Ta powder and carbon powder, both Ta powder and carbon powder must be uniformly mixed, increasing the load on the manufacturing process. Moreover, since Ta metal is easily oxidized, it is preferable to use TaC powder.

  The TaC component 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 TaC powder is large and difficult to uniformly disperse. On the other hand, when the thickness exceeds 5 μm, it is difficult to uniformly disperse at the grain boundaries of the tungsten crystal. From the viewpoint of uniform dispersion, it is preferable that the average particle diameter of TaC powder ≦ the average particle diameter of tungsten powder.

  The TaC powder or Ta powder preferably has Nb of 5 parts by mass or less when the Ta amount is 100 parts by mass. The TaC powder or Ta powder may contain an Nb component as an impurity. If the amount of Nb is 5 parts by mass or less with respect to the amount of Ta, goodness of the characteristics of the Ta component can be prevented. Further, the smaller the amount of Nb, the better. However, increasing the purity of the raw material causes an increase in cost. Therefore, the amount of Nb is more preferably 0.1 to 3 parts by mass.

  Moreover, at least 1 sort (s) or more of dope materials chosen from K, Si, and Al shall be added as needed. 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. Moreover, it is good also as a slurry by mixing with an organic binder and an organic solvent as needed. Moreover, you may perform a granulation process as needed.

  Next, it presses with a metal mold | die and produces a molded object. 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. Moreover, it is preferable to perform sintering conditions at 1400-3000 degreeC 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. Further, if the sintering temperature exceeds 3000 ° C. or the sintering time exceeds 20 hours, the tungsten crystal may grow too much. In addition, 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. Further, the sintering process is not particularly limited, such as electric current sintering, atmospheric pressure sintering, and pressure sintering.

  Next, a process for processing the sintered body into a part is performed. Examples of the process for processing the part include a forging process, a rolling process, a drawing process, a cutting process, and a polishing process. Moreover, a coiling process is mentioned when using it as a coil component. Moreover, when producing a mesh grid as parts for transmission pipes, a step of assembling filaments into a mesh can be mentioned.

  Next, after processing into a part, a strain relief heat treatment is performed as necessary. The strain relief heat treatment is preferably performed in a 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.

(Second Embodiment)
According to the second embodiment, a tungsten alloy containing a W component and a Ta component containing TaC particles, a tungsten alloy part using the tungsten alloy, a discharge lamp, a transmission tube, and a magnetron are provided. The amount of the Ta component is in the range of 0.1 wt% to 5 wt% in terms of TaC. The Ta component contains at least TaC, and may contain a Ta-containing compound other than TaC, Ta alone, or the like. Examples of the Ta-containing compound include Ta ₂ O ₃ . The average primary particle diameter of TaC particles is 15 μm or less.

  An electrode component for a discharge lamp according to an embodiment is a discharge lamp electrode component made of a tungsten alloy. The tungsten alloy contains a Ta component in an amount of 0.1 to 5 wt% in terms of TaC, and a primary particle of TaC particles in the Ta component. The diameter is an average particle diameter of 15 μm or less.

  5 and 6 show an example of an electrode component for a discharge lamp according to 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.

First, the tungsten alloy contains a Ta component in an amount of 0.1 to 5 wt% in terms of TaC. Examples of the Ta component include TaC and Ta. In the case of TaC ( tantalum carbide), the atomic ratio of C / Ta is not limited to 1, but includes those having an atomic ratio of C / Ta in the range of 0.75 to 1. Further, the Ta component is contained in an amount of 0.1 to 5 wt% in terms of TaC (C / Ta atomic ratio = 1). The Ta component is a component that functions as an emitter material in an electrode component for a discharge lamp. If the content of the Ta component is less than 0.1 wt% in terms of TaC, the emission characteristics are insufficient. On the other hand, if it exceeds 5 wt%, the strength may be lowered. Therefore, the Ta component is preferably 0.3 to 3.0 wt%, more preferably 0.5 to 2.5 wt% in terms of TaC.

  Further, the Ta component exists as TaC or Ta as described above. Among these, the primary particle diameter of TaC needs to be particles having an average particle diameter of 15 μm or less. That is, it is important that TaC is TaC particles. TaC particles exist at the grain boundaries between tungsten crystal particles. For this reason, if the TaC particles are too large, the gaps between the tungsten crystal particles are enlarged, which causes a decrease in density and strength. Moreover, since the TaC particles function not only as an emission material but also as a dispersion strengthening material due to the presence at the grain boundaries between tungsten crystal particles, the strength of the electrode parts can be improved.

  Moreover, it is preferable that the primary particle diameter of TaC particles is an average particle diameter of 5 μm or less and a maximum diameter of 15 μm or less. The TaC particles preferably have an average particle size of 0.1 to 3 μm. Moreover, it is preferable that a maximum diameter is 1-10 micrometers or less. Small TaC 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 of the electrode, the TaC particles preferably have an average particle diameter of 0.1 μm or more or a maximum diameter of 1 μm or more.

  Moreover, it is preferable that the dispersion state of TaC particle | grains is the range of 2-30 pieces on arbitrary linear 200 micrometers. If the number of TaC particles is less than 2 (0 to 1) per 200 μm in a straight line, the TaC particles are partially reduced, and the emission variation is increased. On the other hand, if the number of TaC particles is more than 30 per line (200 μm) (31 or more), TaC particles are excessively increased in part, which may cause adverse effects such as strength reduction. As a method for measuring the dispersion state of TaC particles, an arbitrary cross section of a tungsten alloy is magnified. The magnified photo should be 1000 times or more. An arbitrary straight line 200 μm (line thickness 0.5 mm) is drawn on the enlarged photograph, and the number of TaC particles existing on the line is counted.

  The secondary particles of TaC particles preferably have a maximum diameter of 100 μm or less. The secondary particles of TaC particles 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 TaC particles is preferably as small as 100 μm or less, 50 μm or less, and further 20 μm or less.

  Of the Ta components, Ta (metal Ta) has various dispersion states.

The first dispersed state exists as metal Ta particles. Similar to TaC particles, metal Ta particles exist at the grain boundaries between tungsten crystal particles. By being present at the grain boundaries between the tungsten crystal particles, the metal Ta particles also function as an emission material and a dispersion strengthening material. For this reason, the primary particle diameter of the metal Ta particles is preferably 15 μm or less, more preferably 10 μm or less, and preferably 0.1 to 3 μm. The maximum diameter is preferably 15 μm or less, and more preferably 10 μm or less. The metal Ta particles may be prepared by mixing TaC particles and metal Ta particles in advance when producing a tungsten alloy, or by decarburizing the TaC particles during the manufacturing process. In addition, it is preferable to use a decarburizing method because a deoxidizing effect of reacting with oxygen in tungsten and releasing it as carbon dioxide out of the system can be obtained. If deoxidation can be performed, the electrical resistance of the tungsten alloy can be lowered, so that the conductivity of the electrode is improved. Further, some of the metal Ta particles may be Ta ₂ O ₃ particles.

  In the second dispersion state, metal Ta is present on the surface of TaC particles. When a sintered body of a tungsten alloy is produced in the same manner as in the first dispersion state, carbon is decarburized from the surface of TaC particles, and a metal Ta film is formed on the surface. Even TaC particles with a metal Ta coating show excellent emission characteristics. The TaC particles with a metal Ta coating preferably have an average particle size of 15 μm or less, more preferably 10 μm or less, and 0.1 to 3 μm. The maximum diameter is preferably 15 μm or less, and more preferably 10 μm or less.

  In the third dispersion state, a part or all of the metal Ta is dissolved in tungsten. Metal Ta is a combination that forms a solid solution with tungsten. By forming a solid solution, the strength of the tungsten alloy can be improved. Moreover, the measuring method of the presence or absence of solid solution is possible by XRD analysis. First, the contents of Ta component and carbon are measured. Further, TaC is converted from Ta amount and carbon amount in Ta component, and it is confirmed that TaCx, x <1. Next, XRD analysis is performed to confirm that no metal Ta peak is detected. Although TaCx, x <1 and tantalum that is not tantalum carbide exist, the fact that the peak of metal Ta is not detected means that metal Ta is dissolved in tungsten.

  On the other hand, TaCx, x <1 and tantalum that is not tantalum carbide exist, and the peak of metal Ta is detected thereon, which means that metal Ta does not dissolve and exists at the grain boundary between tungsten crystals. It means that it is in one dispersed state. Moreover, it can analyze that it is a 2nd dispersion state by using EPMA (electron beam microanalyzer) and TEM (transmission electron microscope).

  The dispersion state of the metal Ta 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.

  Moreover, when the total content of the Ta component (Ta content) is 100 parts by mass, the ratio of Ta that is TaC particles is preferably 0.1 to 50 parts by mass. Of course, all of the Ta component may be TaC particles. If it is TaC particle | grains, an emission characteristic will be acquired. On the other hand, the conductivity and strength of the tungsten alloy can be improved by dispersing the metal Ta. However, if all Ta components are metallic Ta, the emission characteristics and high-temperature strength are reduced. Metal Ta has a melting point of 2990 ° C., TaC has a melting point of 3980 ° C., and metal tungsten has a melting point of 3400 ° C. Since TaC has a higher melting point, the high temperature strength is improved by containing a predetermined amount of TaC.

  As a method for analyzing the contents of TaC and metal Ta, the total amount of Ta in the tungsten alloy is measured by ICP analysis. Next, the total carbon content in the tungsten alloy is measured by a combustion-infrared absorption method. When the tungsten alloy is a binary system consisting of a Ta component and a W component, it can be considered that all the measured carbon amounts are TaC. Therefore, the TaC amount in the Ta component can be measured by comparing the measured total Ta amount and the total carbon amount. In this method, the amount of TaC is calculated with C / Ta = 1.

  The size of the TaC particles is measured by taking an enlarged photograph of an arbitrary cross section of the tungsten alloy sintered body and measuring the longest diagonal line of the TaC particles appearing there as the particle size of the TaC particles. In this operation, 50 TaC particles are measured, and the average value is defined as the average particle size of the TaC particles. The largest value among the TaC particle diameters (longest diagonal line) is defined as the maximum diameter of the TaC particles.

  Further, the tungsten alloy may contain 0.01 wt% or less of a doping material composed of at least one 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. Further, the lower limit of the content of the dope material is not particularly limited, but is preferably 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 deteriorate and mass productivity deteriorates.

  Further, the tungsten alloy may contain 2 wt% or less of at least one selected from the group consisting of Ti, Zr, V, Nb, Hf, Mo, and rare earth elements. Examples of Ti, Zr, V, Nb, Hf, Mo, and rare earth element include any one of a single metal, an oxide, and a carbide. Moreover, you may contain 2 or more types. In addition, even if it contains 2 or more types, the sum total is preferably 2 wt% or less. These contained components mainly function as a dispersion reinforcing material. Since TaC particles function as an emission material, they are consumed when the discharge lamp is used for a long time. Since Ti, Zr, V, Nb, Hf, Mo, and rare earth elements have weak emission characteristics, the consumption as a result of emission is small, so that the function as a dispersion strengthening material can be maintained over a long period of time. Although the minimum of content is not specifically limited, It is preferable that it is 0.01 wt% or more. Among these components, Zr, Hf, and rare earth elements are preferable. Since these components are atoms having a large atomic radius of 0.16 nm or more, they are components having a large surface current density. In other words, it can be said that the metal simple substance or the compound containing the element whose atomic radius is 0.16 nm or more is preferable.

  Moreover, it is preferable that the electrode component for discharge lamps has a front-end | tip part which made the front-end | tip a taper shape, and a cylindrical body part. 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 determined according to the application.

  Moreover, it is preferable that the wire diameter (phi) of the electrode component for discharge lamps is 0.1-30 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.

  Further, when the crystal structure of the circumferential cross section (cross section) of the body portion is observed, it is preferable that the tungsten crystal having a crystal grain size of 1 to 80 μm per unit area of 300 μm × 300 μm has an area ratio of 90% or more. . FIG. 7 shows an example of a circumferential cross section of the body portion. In the figure, 24 is a body part, and 25 is a circumferential section. When measuring the crystal structure of the circumferential cross section, the cross section at the center of the length of the body part is taken with an enlarged photograph. In addition, when the wire diameter is small and a unit area of 300 μm × 300 μm cannot be measured in one field of view, an arbitrary circumferential cross section is taken a plurality of times. In the enlarged photograph, the longest diagonal line of the tungsten crystal particles shown there is taken as the maximum diameter, and the area% of the maximum diameter falling within the range of 1 to 80 μm is measured.

  The tungsten crystal having a crystal grain size of 1 to 80 μm per unit area in the circumferential cross section of the body portion has an area ratio of 90% or more means that the crystal grain size is smaller than 1 μm and larger than 80 μm. It shows that there are few tungsten crystals. If there are too many tungsten crystals of less than 1 μm, the grain boundaries between tungsten crystal particles become too small. When the proportion of TaC particles increases in the grain boundary, when the TaC particles are consumed by the emission, a large defect is caused and the strength of the tungsten alloy is lowered. 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. More preferably, the crystal grain size is 1 to 80 μm and the area ratio is 96% or more, and further the area ratio is 100%.

  In addition, the average particle size of the tungsten crystal particles in the circumferential cross section is preferably 50 μm or less, more preferably 20 μm or less. The average aspect ratio of the tungsten crystal particles is preferably less than 3. When measuring the aspect ratio, an enlarged photograph with a unit area of 300 μm × 300 μm was taken, and the maximum diameter (ferret diameter) of the tungsten crystal particles reflected there was a long diameter L, a particle diameter obtained by extending vertically from the center of the long diameter L Is the minor axis S, and the major axis L / minor axis S = aspect ratio. 50 grains of this work are performed, and the average value is defined as the average aspect ratio. Moreover, when calculating | requiring an average particle diameter, it is set as (major axis L + minor axis S) / 2 = particle diameter, and let the average value of 50 grains be an average particle diameter.

  Further, when the crystal structure of the cross section in the lateral direction (longitudinal section) of the body portion is observed, it is preferable that the tungsten crystal has a crystal grain size of 2 to 120 μm per unit area of 300 μm × 300 μm and the area ratio is 90% or more. FIG. 8 shows an example of a cross section in the lateral direction. In the figure, 24 is a body part, and 26 is a cross section in the side direction. When measuring the crystal structure of the cross section in the lateral direction, the cross section passing through the center of the wire diameter of the body portion is measured. In addition, when a unit area of 300 μm × 300 μm cannot be measured in one field of view, an arbitrary cross section in the lateral direction is taken a plurality of times. In the enlarged photograph, the longest diagonal line of the tungsten crystal particles shown therein is taken as the maximum diameter, and the area% of the maximum diameter falling within the range of 2 to 120 μm is measured.

  The fact that the tungsten crystal in the cross section in the lateral direction of the body part has a crystal grain size of 2 to 120 μm per unit area has an area ratio of 90% or more means that a small tungsten crystal with a crystal grain size of less than 2 μm and a large tungsten with a crystal grain size exceeding 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. When the proportion of TaC particles increases in the grain boundary, when the TaC particles are consumed by the emission, a large defect is caused and the strength of the tungsten alloy is lowered. 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. More preferably, the crystal grain size is 2 to 120 μm and the area ratio is 96% or more, and further the area ratio is 100%.

  Further, the average particle size of the tungsten crystal particles in the cross section in the lateral direction is preferably 70 μm or less, more preferably 40 μm or less. The average aspect ratio of the tungsten crystal particles is preferably 3 or more. In addition, the measuring method of an average particle diameter and an average aspect ratio is the same as the circumferential cross section.

  As described above, by controlling the size of the tungsten crystal particles and the size and ratio of the Ta component, 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.

In addition, the tungsten alloy 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 method for obtaining the relative density is a value obtained by dividing the actually measured density by the Archimedes method by the theoretical density. (Measured density / theoretical density) × 100 (%) = relative density. The theoretical density is calculated by calculation according to the mass ratio of tungsten as a theoretical density of 19.3 g / cm ³ , tantalum as a theoretical density of 16.65 g / cm ³ , and tantalum carbide as a theoretical density of 13.9 g / cm ³ . Shall. For example, in the case of a tungsten alloy composed of 1 wt% TaC, 0.2 wt% Ta, and the balance tungsten, 16.65 × 0.01 + 13.9 × 0.002 + 19.3 × 0.988 = 19.2627 g / cm ³ Become theoretical density. Further, when calculating the theoretical density, it is not necessary to consider the presence of impurities.

  The tungsten alloy preferably has a Vickers hardness of HV330 or higher. Furthermore, it is preferable to be within the 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. In addition, the three-point bending strength of the tungsten alloy can be increased to 400 MPa or more.

  The surface roughness Ra of the discharge lamp electrode component is preferably 5 μm or less. In particular, the surface roughness Ra of the tip is preferably as small as 5 μm or less, more preferably 3 μm or less. If the surface irregularities are large, the emission characteristics will deteriorate.

  The discharge lamp electrode parts as described above can be applied to various discharge lamps. Therefore, a long life can be achieved even when a large voltage of 100 V or higher is applied. Further, the low pressure discharge lamp and the high pressure discharge lamp as described above are not particularly restricted in use. In addition, the wire diameter of the body part is 0.1-30 mm, the thin wire diameter is 0.1 mm to 3 mm, the medium size is over 3 mm, the medium size is 10 mm or less, and the thick one is over 10 mm to 30 mm or less. Applicable. 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 a pair of electrode components 22 so that the electrode tip portions face each other. The electrode component 22 is joined to the electrode support rod 28. Further, a phosphor layer (not shown) is provided on the inner surface of the glass tube 29. Further, inside the glass tube, mercury, halogen, argon gas (or neon gas) or the like is sealed as necessary.

  The discharge lamp of the embodiment uses the electrode component 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 light cleaning devices such as semiconductors. 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. In addition, 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, a manufacturing method will be described. The manufacturing method of the tungsten alloy and the electrode component for a discharge lamp of the embodiment is not particularly limited as long as the tungsten alloy and the discharge lamp electrode component have the above-described configuration.

  First, as a method for producing a tungsten alloy, a tungsten alloy powder containing a Ta component is prepared.

  First, TaC powder is prepared as a Ta component. TaC particles preferably have a primary particle size of 15 μm or less, more preferably 5 μm or less. Moreover, it is preferable to remove beforehand what exceeds 15 micrometers in maximum diameters using a sieve. When the maximum diameter is desired to be 10 μm or less, large TaC particles are removed using a sieve having a target mesh diameter. Further, when it is desired to remove TaC particles having a small particle size, they are removed using a sieve having a target mesh diameter. Moreover, it is preferable to perform a grinding | pulverization process of TaC particle | grains with a ball mill etc. before sieving. By performing the pulverization step, the aggregates can be broken, so that it is easy to control the particle size by sieving.

  Next, a step of mixing metal tungsten powder is performed. The metal tungsten powder preferably has an average particle size of 0.5 to 10 μm. A tungsten powder having a tungsten 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 is preferable. Further, similarly to the TaC particles, it is preferable to pulverize beforehand with a ball mill or the like and remove small particles and large particles by a sieving step.

  Metal tungsten powder shall be added so that it may become the target Ta component amount (TaC conversion 0.1-5 wt%) when converted to TaC. A mixed powder of TaC particles and metallic tungsten powder is put in a mixing container, and the mixing container is rotated to mix uniformly. At this time, the mixing container can be made into a cylindrical shape and can be smoothly mixed by rotating in the circumferential direction. Through this step, a tungsten powder containing TaC particles can be prepared. Also, a small amount of carbon powder may be added in consideration of decarburization during the sintering process described later. At this time, the amount of carbon to be decarburized is the same or less.

  Next, a compact is prepared using the obtained tungsten powder containing TaC particles. When forming a molded body, a binder is used as necessary. Moreover, when a molded object is a column shape, it is preferable that it is a column shape with a diameter of 0.1-40 mm. Moreover, when cutting out from a plate-shaped sintered body as described later, the size of the molded body is arbitrary. Moreover, the length (thickness) of a molded object is arbitrary.

  Next, a step of pre-sintering the molded body is performed. Presintering is preferably performed at 1250 to 1500 ° C. By this step, a presintered body can be obtained. Next, a step of subjecting the pre-sintered body to current sintering is performed. In the current sintering, it is preferable to supply current so 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. On the other hand, when the temperature exceeds 2500 ° C., TaC particles and tungsten particles grow too much to obtain the intended crystal structure.

  Another method is to perform the molded body 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. Further, 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 TaC 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 Ta component-containing tungsten sintered body can be obtained. Further, 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 step of cutting out to a predetermined size is performed. By this cutting process, a cylindrical sintered body (ingot) is obtained.

  Next, a step of adjusting the diameter of the cylindrical sintered body (ingot) by forging, rolling, drawing, or the like is performed. It is preferable that the processing rate in that case is 30 to 90% of range. This processing rate means that the processing rate = [(A−B) / 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 32% = [(460.6-314) /460.6 ] × 100% 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.

  On the other hand, when the processing rate is as low as less than 30%, the crystal structure is not sufficiently extended in the processing direction, and the tungsten crystal and the thorium component particles are less likely to have the 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 30 to 90%, preferably 35 to 65%.

  When the relative density of the sintered tungsten alloy is 95% or more, it is not always necessary to process at a predetermined processing rate.

  Moreover, after processing a wire diameter into 0.1-30 mm, it becomes an electrode component by cut | disconnecting to required length. Further, if necessary, the tip is processed into a tapered shape. Further, polishing processing, heat treatment (such as recrystallization heat treatment), and shape processing are performed as necessary.

  Further, the recrystallization heat treatment is preferably performed in a reducing atmosphere, an inert atmosphere, or a vacuum at a temperature in the range of 1300 to 2500 ° C. 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 tungsten alloy and the electrode component for a discharge lamp according to the embodiment can be efficiently manufactured.

  By specifying the physical properties mentioned in the second embodiment in the tungsten alloy of the first embodiment or by specifying the physical properties mentioned in the first embodiment in the tungsten alloy of the second embodiment. Further improvement of characteristics can be expected. For example, in the tungsten alloy of the first embodiment, the primary particle size and secondary particle size of TaC particles, the dispersion state of TaC particles, the dispersion state of metal Ta, the proportion of Ta that is TaC, the dispersion strengthening material, the relative Emission characteristics can be improved by specifying either density or Vickers hardness as in the second embodiment. Further, in the tungsten alloy component of the first embodiment, the emission characteristics can be improved by specifying the crystal structure of the cross section and the surface roughness Ra as in the second embodiment.

Example 1
As a raw material powder, TaC 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%. The TaC powder had an impurity Nb content of 0.5 parts by mass when the Ta content was 100 parts by mass.

  The raw material powder was mixed by 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 cross section was prepared 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, heat treatment at 1600 ° C. was performed in hydrogen as strain relief heat treatment.

  Thus, an emission characteristic measurement electrode was prepared as a tungsten alloy part according to Example 1, and emission current measurement was performed.

(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 TaC component, the x value when the total amount of Ta, TaC and C is converted to TaCx, the amount of carbon in the surface portion and the central portion, and the average grain size of the tungsten crystal were examined. It was. The content of the TaC component was analyzed by ICP analysis and combustion-infrared absorption method to analyze Ta content and carbon content, and converted to TaCx. Moreover, the analysis of the carbon amount of a surface part and a center part cut out the sample for a measurement from the range of 10 micrometers from the surface, and a cylindrical cross section, and measured carbon amount, respectively. The average crystal grain size of tungsten was determined by measuring 100 maximum ferret diameters in an arbitrary cross-sectional structure, and setting the average value as the average crystal grain size. 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.

  As can be seen from FIG. 10, Example 1 was found to have better emission characteristics than Comparative Example 1. As a result, it can be seen that the cathode component 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 2100-2200 ° 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 5)
Next, a raw material mixed powder in which the amount of TaC added and the amount of K added as a doping material was changed as shown in Table 2 was prepared. Each raw material mixed powder was molded and sintered at 1500 to 1900 ° C. for 7 to 16 hours in hydrogen to obtain a sintered body. In Examples 2 to 3, a cutting process was performed in the same manner as in Example 1 by performing forging and the like as necessary. In Examples 4 to 5, the size of the molded body was adjusted to directly obtain a sintered body having a diameter of 2.4 mm and a length of 150 mm.

Each sample was subjected to centerless polishing to have a surface roughness Ra of 5 μm or less. Next, heat treatment at 1400 to 1700 ° C. was performed in hydrogen as strain relief heat treatment. 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 the table, all the cathode parts for the discharge lamp according to this example exhibited excellent characteristics. At the time of measurement, the cathode component was 2100-2200 ° C. For this reason, it turns out that the cathode components which concern on Examples 2-5 are excellent also in high temperature intensity | strength, a lifetime, etc.

(Examples 11 to 18, Comparative Example 11)
Tungsten powder (purity 99.0 wt% or more) and TaC powder shown in Table 5 were prepared as raw material powders. 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, the tungsten powder and the TaC powder were mixed so that the amount of the Ta component in the tungsten alloy in terms of TaC would be the ratio shown in Table 6, and mixed again by a ball mill. Next, the molded body was prepared by molding. 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, an enlarged photograph of the circumferential cross section and the side cross section of the body part of each discharge lamp electrode part is taken, the average particle diameter of the primary particles of the TaC component, the maximum diameter of the primary particles and the secondary particles, the tungsten crystal particles Ratio, average particle diameter, and aspect ratio were measured. Regarding the enlarged photograph, a circumferential cross section and a cross section in the lateral direction passing through the center of the body part were cut out and examined for an arbitrary unit area of 300 μm × 300 μm. The results are shown in Table 8.

  Next, for each electrode component for a discharge lamp, the x value when the total amount of Ta, TaC and C was converted to TaCx and the ratio of TaC in the Ta component were measured. Further, the oxygen content, relative density (%), Vickers hardness (Hv), and three-point bending strength were determined.

As for the ratio of TaC in the Ta component, the amount of Ta in the tungsten alloy is measured by ICP analysis, and the amount of carbon in the tungsten alloy is measured by the combustion-infrared absorption method. It can be considered that the carbon in the tungsten alloy is TaC. Therefore, the total amount of Ta detected is 100 parts by weight, the amount of Ta that becomes TaC 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. Moreover, Vickers hardness (Hv) was calculated | required according to JIS-Z-2244. The three-point bending strength was determined according to JIS-R-1601. 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 TaC has been decarburized. In addition, the Ta component which is not TaC is in the state of any one of those in which metal Ta particles are formed, a part of the surface of TaC particles is in metal Ta, or a solid solution of tungsten and tantalum. there were.

(Examples 19 to 23)
Next, the same tungsten powder and TaC powder as in Example 12 were used, and the second component was changed to the composition shown in Table 10. 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 the table, 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 23A, Comparative Examples 11-1A to 11-2A and Comparative Example 12A)
The emission characteristics of the electrode parts for discharge lamps of Examples 11 to 23, 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.

  Although the electrode parts for discharge lamps according to the respective examples did not use thorium oxide, they exhibited emission characteristics equal to or higher than those of Comparative Example 12 using thorium oxide. Moreover, the cathode component was 2100-2200 degreeC at the time of a measurement. For this reason, the electrode components for discharge lamps according to the respective examples have excellent high temperature strength.

(Examples 24-26)
Next, the discharge lamp electrodes of Example 11, Example 13, and Example 16 were manufactured by the same manufacturing method except that the recrystallization heat treatment condition was changed to 1800 ° C. Example 24 (Example 11) In which the recrystallization heat treatment condition was changed to 1800 ° C.), Example 25 (recrystallization heat treatment condition in Example 13 was changed to 1800 ° C.), Example 26 (recrystallization heat treatment condition in Example 16 was changed to 1800 ° C.) Prepared as above). Similar measurements were made. The results are shown in Tables 14-15.

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 TaC has been decarburized. Moreover, as a result of analyzing the Ta component which is not TaC, both were solid solutions of tungsten and tantalum. That is, there are two types of Ta components, Ta and TaC. For this reason, it can be seen that when the recrystallization heat treatment temperature is set to 1700 ° C. or higher, the metal Ta is easily dissolved in tungsten. The emission characteristics were measured by the same method as in Example 11A. The results are shown in Table 16.

  As described above, it was found that the emission characteristics are improved by dissolving all of the metal Ta in tungsten. This is considered to be because the metal Ta is easily present on the surface of the tungsten alloy due to the solid solution.

Further, since it has excellent emission characteristics as described above, it can be used not only for discharge lamp electrode parts but also for fields such as magnetron parts (coil parts) and transmission tube parts (mesh grids) that require emission characteristics.
Hereinafter, the invention described in the scope of the claims of the present application will be appended.
[1] A tungsten alloy containing a W component and a Ta component containing TaC in a range of 0.1 wt% to 3 wt% in terms of TaC.
[2] Tungsten containing a W component and a Ta component containing TaC particles in a range of 0.1 wt% to 5 wt% in terms of TaC, and the average primary particle diameter of the TaC particles is 15 μm or less. alloy.
[3] The tungsten alloy according to [2], wherein a primary particle diameter of the TaC particles is an average particle diameter of 5 μm or less and a maximum diameter of 15 μm or less.
[4] The tungsten alloy according to [2] or [3], wherein the TaC particles have a secondary particle size of a maximum value of 100 μm or less.
[5] The tungsten alloy according to any one of [1] to [4], wherein the Ta component further contains at least one of Ta and C.
[6] Ta, when TaC _x terms the total amount of TaC and C, tungsten alloy according to [5] characterized in that the x <1.
[7] Ta, when TaC _x terms the total amount of TaC and C, 0 <x <tungsten alloy according to [5], wherein the 1.
[8] Ta, when TaC _x terms the total amount of TaC and C, 0.001 <x <tungsten alloy according to [5], characterized in that 0.5.
[9] The tungsten alloy according to any one of [1] to [8], wherein at least one selected from the group consisting of K, Si and Al is contained in an amount of 0.01 wt% or less.
[10] The tungsten alloy according to any one of [1] to [9], wherein the Nb content is 5 parts by mass or less when the Ta content is 100 parts by mass.
[11] The tungsten alloy according to any one of [1] to [10], wherein the Ta component contains metal Ta dissolved in W.
[12] The tungsten alloy according to any one of [1] to [11], wherein the Ta component contains metal Ta, and the metal Ta is present on a surface.
[13] Any of [1] to [12], characterized in that when the Ta content is 100 parts by mass, the proportion of Ta as TaC is 0.1 parts by mass or more and 50 parts by mass or less. Tungsten alloy described in 1.
[14] The tungsten alloy according to any one of [1] to [13], wherein the Vickers hardness is Hv330 or more.
[15] The tungsten alloy according to any one of [1] to [14], wherein the W component includes tungsten particles having an average crystal grain size of 1 μm to 100 μm.
[16] A tungsten alloy part comprising the tungsten alloy according to any one of [1] to [15].
[17] A tungsten alloy component comprising the tungsten alloy according to any one of [1] to [15], wherein the tungsten alloy component is a wire having a wire diameter of 0.1 mm to 30 mm.
[18] The crystal structure of the cross section of the wire rod is such that an area ratio occupied by a tungsten crystal having a crystal grain size of 1 μm to 80 μm per unit area of 300 μm × 300 μm is 90% or more. Tungsten alloy parts.
[19] The crystal structure of the longitudinal cross-section of the wire is characterized in that the area ratio occupied by tungsten crystals having a crystal grain size of 2 μm to 120 μm per unit area of 300 μm × 300 μm is 90% or more. Tungsten alloy parts.
[20] The tungsten alloy according to any one of [16] to [19], wherein the tungsten alloy is used for at least one component selected from the group consisting of a discharge lamp component, a transmitter tube component, and a magnetron component. parts.
[21] A discharge lamp comprising the tungsten alloy part according to [20].
[22] A transmission tube comprising the tungsten alloy part according to [20].
[23] A magnetron comprising the tungsten alloy part according to [20].

  DESCRIPTION OF SYMBOLS 1 ... Cathode electrode, 2 ... Electrode body part, 3 ... Electrode tip part, 4 ... Discharge lamp, 5 ... Electrode support rod, 6 ... Glass tube, 7 ... Coil component, 8 ... Upper support member, 9 ... Lower support member, DESCRIPTION OF SYMBOLS 10 ... Support rod, 11 ... Cathode structure for magnetrons, 21 ... Electrode components for discharge lamps, 22 ... Electrode components for discharge lamps which have a taper-shaped front-end | tip part, 23 ... End part, 24 ... Body part, 25 ... Circumferential direction Cross section, 26 ... cross section in the lateral direction, 27 ... discharge lamp, 28 ... electrode support rod, 29 ... glass tube.

Claims (17)

A tungsten alloy used for a discharge lamp component, a transmitter tube component, or a magnetron component, containing a W component and a Ta component containing TaC particles in a range of 0.1 wt% to 5 wt% in terms of TaC, the average primary particle size of the TaC particles is at 15μm or less, Ta, when converted TaC _x content of TaC and C, tungsten alloy, which is a 0.01 ≦ x <0.5. 2. The tungsten alloy according to claim 1, wherein the primary particle diameter of the TaC particles is an average particle diameter of 5 μm or less and a maximum diameter of 15 μm or less. 3. The tungsten alloy according to claim 1, wherein a secondary particle diameter of the TaC particles is a maximum value of 100 μm or less. The tungsten alloy according to any one of claims 1 to 3 , wherein 0.01 wt% or less of at least one selected from the group consisting of K, Si and Al is contained. The tungsten alloy according to any one of claims 1 to 4 , wherein when the Ta content is 100 parts by mass, the Nb content is 5 parts by mass or less. The tungsten alloy according to any one of claims 1 to 5 , wherein the Ta component contains metal Ta dissolved in W. The tungsten alloy according to any one of claims 1 to 6 , wherein the Ta component contains metal Ta, and the metal Ta exists on a surface of the TaC particle. 8. The tungsten alloy according to claim 1 , wherein when the Ta content is 100 parts by mass, the ratio of Ta being TaC is 1 part by mass or more and 50 parts by mass or less. . The tungsten alloy according to any one of claims 1 to 8 , wherein the Vickers hardness is Hv330 or more. 10. The tungsten alloy according to claim 1 , wherein the W component includes tungsten particles having an average crystal grain size of 1 μm to 100 μm. A tungsten alloy part comprising the tungsten alloy according to any one of claims 1 to 10 . A tungsten alloy part comprising the tungsten alloy according to any one of claims 1 to 10 and having a wire diameter of 0.1 mm to 30 mm. 13. The tungsten alloy part according to claim 12, wherein the crystal structure of the cross section of the wire material is such that an area ratio occupied by a tungsten crystal having a crystal grain size of 1 μm to 80 μm per unit area of 300 μm × 300 μm is 90% or more. . 13. The tungsten alloy part according to claim 12, wherein the crystal structure of a longitudinal section of the wire is 90% or more of an area ratio occupied by a tungsten crystal having a crystal grain size of 2 μm to 120 μm per unit area of 300 μm × 300 μm. . A discharge lamp comprising the tungsten alloy part according to any one of claims 11 to 14 . A transmission tube comprising the tungsten alloy part according to any one of claims 11 to 14 . A magnetron comprising the tungsten alloy part according to any one of claims 11 to 14 .

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