JP2013182739A - Cathode component support rod for discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-durability cathode component support rod for a discharge lamp.SOLUTION: A cathode component support rod for a discharge lamp is comprised of a tungsten alloy containing a cobalt component in 0.005 to 0.1 wt.% in Co conversion. The cathode component support rod has a wire diameter ranging from 1 to 20 mm. When a crystal particle size of tungsten is observed in an area ratio in a unit area 300 μm×300 μm, in a circumferential direction cross section, a range of 1 to 80 μm is 90% or more and in a side face direction cross section, a range of 10 to 120 μm is 90% or more.

Description

  The present invention relates to a cathode component support rod for a discharge lamp.

Discharge lamps 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. Thus, the discharge lamp is used in various devices such as a lighting device and a manufacturing device.
Conventionally, tungsten alloys containing thorium oxide (ThO ₂ ) have been used for cathode components for discharge lamps. Japanese Unexamined Patent Publication No. 2002-226935 (Patent Document 1) discloses a thorium-containing tungsten alloy having improved deformation resistance by finely dispersing thorium and a thorium compound with an average particle size of 0.3 μm or less. .
On the other hand, the cathode component of the discharge lamp is joined to a component called a support bar to constitute a discharge lamp. The discharge lamp exerts emission characteristics by applying a voltage of 10V or more, and further several hundreds of volts. For this reason, the support rod that supports the cathode component is also required to have high temperature strength.

JP 2002-226935 A

In addition, it was a heavy burden on the manufacturing process to uniformly disperse thorium as fine as 0.3 μm or less. If the dispersion of thorium is non-uniform, it will lead to non-uniformity of the location where the emission occurs in the cathode component, and this also makes it difficult to extend the service life. In addition, since thorium itself is a radioactive element, development of a cathode component support rod that does not use thorium itself has been required due to adverse environmental effects.
The present invention is intended to solve such a problem. For example, it is possible to achieve a long life in a discharge lamp in which a high voltage of 10 V or higher is applied, and a cathode component support rod that does not use a thorium component. Is intended to provide.

The cathode component support rod for a discharge lamp of the present invention is a cathode component support rod for a discharge lamp made of a tungsten alloy containing 0.005 to 0.1 wt% of a cobalt component in terms of Co. When the crystal grain size of tungsten is observed at an area ratio in a unit area of 300 μm × 300 μm, the circumferential cross section is 90% or more in the range of 1 to 80 μm, and the range of 10 to 120 μm in the lateral direction is 90%. This is the feature described above.
Moreover, it is preferable that the cobalt component forms a solid solution with tungsten. Further, the crystal grain size of tungsten is preferably such that the circumferential section has an aspect ratio of less than 3, and the lateral section has an aspect ratio of 3 or more.
Moreover, it is preferable that Al content is 0.001-0.010 wt%. Moreover, it is preferable that Si content is 0.01-0.05 wt%. Moreover, it is preferable that K content is 0.005-0.030 wt%. Moreover, it is preferable that Mo content is 0.03 wt% or less. Moreover, it is preferable that Fe content is 0.02 wt% or less. Moreover, it is preferable that specific gravity exists in the range of 17-19 g / cm < ³ >. Further, the surface roughness Ra is preferably 5 μm or less. Moreover, it is preferable that the applied voltage of a discharge lamp is 100V or more.

  The cathode component for a discharge lamp of the present invention is excellent in high-temperature strength because the tungsten crystal size is controlled in both the cross-sectional direction and the lateral cross-section. Therefore, a discharge lamp using the same can have a long life.

The figure which shows an example of the cathode component support rod of this invention. The figure which shows an example of the circumferential direction cross section. The figure which shows an example of a side surface cross section. The figure which shows an example of the discharge lamp of this invention.

The cathode component support rod for a discharge lamp of the present invention is a cathode component support rod for a discharge lamp made of a tungsten alloy containing 0.005 to 0.1 wt% of a cobalt component in terms of Co. When the crystal grain size of tungsten is observed at an area ratio in a unit area of 300 μm × 300 μm, the circumferential cross section is 90% or more in the range of 1 to 80 μm, and the range of 10 to 120 μm in the lateral direction is 90%. This is the feature described above.
First, the cobalt component is one or two of metallic cobalt and cobalt oxide. The cobalt component is preferably contained in an amount of 0.005 to 0.1 wt% in terms of Co. If the amount is less than 0.005 wt%, the effect of addition is small, and if it exceeds 0.1 wt%, the sinterability and workability deteriorate. Therefore, the content of the cobalt component is preferably in the range of 0.01 to 0.05 wt% in terms of Co.

Further, the cathode component support rod has a wire diameter of 1 to 20 mm. FIG. 1 shows an example of a cathode component support rod for a discharge lamp according to the present invention. In the figure, 1 is a cathode component support rod, 2 is a body portion, and 3 is a tip portion. The body part 2 has a cylindrical shape, and the body part 2 has a diameter of 1 to 20 mm. Moreover, it is preferable that the length of the trunk | drum 2 is 10-600 mm. As described above, the use of the discharge lamp has various fields, and the brightness required therefor also varies. Therefore, the thickness of the body part of the cathode part support rod is changed according to the required brightness. Further, the length of the body portion is also changed in accordance with the size of the discharge lamp.
Further, the tip portion 3 is exemplified by a flat surface as shown in FIG. The tip is used as a joint surface with the cathode component. The tip portion is not limited to a flat surface as long as it has a shape for joining with the cathode component, and may be a convex portion, a concave portion, or an R shape.

Further, when the crystal grain size of tungsten in the body part is observed at an area ratio in a unit area of 300 μm × 300 μm, the circumferential cross section is 90% or more in the range of 1 to 80 μm, and the cross section in the lateral direction is 90% in the range of 10 to 120 μm. This is necessary.
FIG. 2 shows an example of a circumferential section, and FIG. 3 shows an example of a side section. As shown in FIG. 2, the circumferential cross section is perpendicular to the side surface. As long as it is perpendicular to the side surface, the section to be taken is arbitrary. Moreover, it is preferable to measure in the cross section at the center of the body part length. Further, the cross section in the side direction is a cross section parallel to the side surface. Further, it is preferable that the cross section at the center of the length of the body part is a circumferential cross section, and the cross section in the lateral direction is perpendicular to the midpoint.
In the present invention, when a tungsten crystal is observed at an area ratio in a unit area of 300 μm × 300 μm, the circumferential cross section is characterized in that the range of 1 to 80 μm is 90% or more. The fact that the tungsten crystal in the range of 1 to 80 μm has an area ratio of 90% or more indicates that the tungsten crystal particles having a unit area of 300 μm × 300 μm are less than 1 μm and more than 80 μm are less than 10% in the area ratio. In other words, it means that the proportion of fine crystals less than 1 μm and coarse crystals exceeding 80 μm is small. Moreover, it is preferable that the tungsten crystal of the range of 1-80 micrometers is 100% by area ratio.

  Further, when the tungsten crystal is observed at an area ratio in a unit area of 300 μm × 300 μm, the cross section in the lateral direction is characterized in that the range of 10 to 120 μm is 90% or more. The fact that the tungsten crystal particles in the range of 10 to 120 μm have an area ratio of 90% or more indicates that the tungsten crystal particles having a unit area of 300 μm × 300 μm are less than 10 μm and more than 120 μm are less than 10% in the area ratio. Moreover, it is preferable that the range of 10-120 micrometers is 100%.

  The size of the tungsten crystal particles affects the strength of the cathode component support rod, particularly the high temperature strength. The Co component preferably forms a solid solution with tungsten. When a solid solution is formed, Co is dispersed in the tungsten crystal. When the tungsten crystal size is set as described above, the uniformity of the tungsten crystal in which the cobalt component is dispersed can be controlled three-dimensionally. That is, by controlling both the circumferential cross section and the side cross section, not just the unidirectional cross-sectional structure, the grain boundaries between the tungsten crystals can exist uniformly in a three-dimensional manner. As a result, the dispersion state of the cobalt component can be made uniform. Also, from the viewpoint of uniform dispersion, when the tungsten crystal is observed at an area ratio of 300 μm × 300 μm, the tungsten crystal 2-30 μm is 90% or more and the side surface cross section 15-50 μm is 90% or more. Is preferred.

  The crystal grain size of tungsten is preferably such that the circumferential section has an aspect ratio of less than 3 and the side section has an aspect ratio of 3 or more. If the aspect ratio of the tungsten crystal in the circumferential cross section is less than 3, the tungsten crystal in the circumferential cross section of the body portion has an elliptical or circular crystal structure. When the aspect ratio of the tungsten crystal in the side surface section is 3 or more, the tungsten crystal in the side surface section of the body portion has a long and thin fibrous crystal structure. Strength can be improved by forming a fibrous crystal having an aspect ratio of 3 or more into a bundle (sintered body). From the viewpoint of improving the strength, it can be considered that the aspect ratio of the circumferential cross section is 3 or more to be a fibrous structure. If both the circumferential section and the side section have an aspect ratio of 3 or more, the strength increases, but the workability decreases. If the fibrous crystals are randomly oriented, breakage due to contact with the die during the drawing process is likely to occur. If only the cross section in the side direction is fibrous, contact with the die is smooth, and disconnection in the drawing process can be suppressed. In addition, when the fiber crystals are randomly oriented, the contact angle between the grindstone and the tungsten crystals becomes random when processing into a shape with a tapered tip, resulting in variations in the amount of scraping. If the amount of scraping varies, it takes time to uniformly process the tip. Further, if the contact angle with the grindstone is random, the grindstone is consumed quickly, resulting in an increase in cost.

Moreover, it is preferable that Al content is 0.001-0.010 wt%. Moreover, it is preferable that Si content is 0.01-0.05 wt%. Moreover, it is preferable that K content is 0.005-0.030 wt%. K (potassium), Al (aluminum), and Si (silicon) function as doping materials, and are effective in controlling the recrystallized structure when added. By controlling the recrystallized structure, it is easy to control the tungsten crystal size and the dispersion state of the cobalt component. Moreover, K, Al, and Si may be one kind of these, or may contain two or more kinds.
Moreover, it is preferable that Mo content is 0.03 wt% or less, and Fe content is 0.02 wt% or less. The tungsten alloy of the present invention may contain impurity metal components in a total amount of 0.1 wt% or less (including zero). Among the impurity metal components, Mo (molybdenum) and Fe (iron) are components that are easily mixed in the raw material or the manufacturing process. If Mo exceeds 0.03 wt% (300 wtppm) or Fe exceeds 0.02 wt% (200 wtppm), the high temperature strength of the tungsten alloy may be reduced. Moreover, Ni, Cr, Cu, Ca, Mg, and C are mentioned as impurities other than Mo and Fe. Respectively, Ni (nickel) is 50 wtppm or less, Cr (chromium) is 50 wtppm or less, Cu (copper) is 50 wtppm or less, Ca (calcium) is 50 wtppm or less, Mg (magnesium) is 50 wtppm or less, Na (sodium) is 20 wtppm or less, C (carbon) is preferably 50 wtppm or less. Moreover, it is preferable that an impurity component is 0% (below detection limit), respectively.
In addition, the analysis method of each component is as follows. K and Na are analyzed by acid decomposition-atomic absorption. Co, Al, Si, Fe, Ni, Cr, Mo, Cu, Ca, and Mg are analyzed by acid decomposition-ICP emission spectroscopy. C is analyzed by a high frequency induction furnace combustion-infrared absorption method.

Moreover, it is preferable that specific gravity exists in the range of 17-19 g / cm < ³ >. When the specific gravity is less than 17 g / cm ³ , the density is low and the gap is large, and the strength as a component is reduced. Further, if the specific gravity exceeds 19 g / cm ³ , no further effect can be obtained.
Further, the surface roughness Ra 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. The tip is used by being joined to the cathode component. Various methods such as brazing and diffusion bonding are applied to the bonding. By making the tip portion a flat surface, it is possible to reduce the displacement of the cathode component.

  The cathode part support rod for a discharge lamp 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. Moreover, the wire diameter of the body portion is 1 to 20 mm, and the wire diameter can be applied from a thin one having a diameter of 1 mm to less than 5 mm to a thick one having a diameter of 5 mm to 20 mm.

Next, a manufacturing method will be described. The production method of the cathode component support rod of the present invention is not particularly limited as long as it has the above-described configuration, but examples of the production method for obtaining it efficiently include the following.
First, as a tungsten alloy manufacturing method, a tungsten alloy powder containing a cobalt component is prepared. A wet method is preferable for the preparation of the tungsten alloy powder.
In the wet method, first, a step of preparing a tungsten component powder is performed. Examples of the tungsten component powder include ammonium tungstate (APT) powder, metal tungsten powder, and tungsten oxide powder. These tungsten component powders may be used singly or in combination of two or more. Also, ammonium tungstate powder is desirable because of its relatively low price. The tungsten component powder preferably has an average particle size of 5 μm or less.
When ammonium tungstate powder is used, the ammonium tungstate powder is heated to 400 to 600 ° C. in the air or in an inert atmosphere (nitrogen, argon, etc.) to change the ammonium tungstate powder to tungsten oxide powder. . If it is less than 400 ° C., the change to tungsten oxide is not sufficient, and if it exceeds 600 ° C., the tungsten oxide particles tend to be coarse. Through this step, tungsten oxide powder is prepared.
Next, a step of adding cobalt component powder and tungsten oxide powder to the solution is performed. Examples of the cobalt component powder include metallic cobalt powder, cobalt oxide powder, and cobalt chloride powder. Of these, cobalt chloride powder is preferred. Cobalt chloride powder is a component that is easy to mix uniformly in a liquid. By this step, a solution containing a cobalt component and tungsten oxide powder is prepared. Moreover, it is preferable to add so that the final cobalt concentration is the same or slightly higher. The cobalt component powder preferably has an average particle size of 5 μm or less. The solution is preferably pure water.
In addition, a predetermined amount of one or more dope materials selected from Al, Si, and K is added as necessary.

Next, the process of evaporating the liquid component of the solution containing the cobalt component and the tungsten oxide powder is performed. Next, the decomposition process which heats at 400-900 degreeC in air | atmosphere and uses cobalt components, such as a cobalt chloride, as a cobalt oxide is performed. By this step, a mixed powder in which cobalt oxide powder and tungsten oxide powder are mixed can be prepared. Moreover, when the cobalt oxide density | concentration of the mixed powder with which the completed cobalt oxide powder and tungsten oxide powder were mixed is measured and a density | concentration is low, it is preferable to add tungsten oxide powder.
Next, a process of reducing the tungsten oxide powder to a metallic tungsten powder by heating the mixed powder obtained by mixing the cobalt oxide powder and the tungsten oxide powder at 750 to 950 ° C. in a reducing atmosphere such as hydrogen is performed. Through this step, a tungsten powder containing cobalt oxide or metal cobalt powder can be prepared.

Next, a compact is prepared using the obtained tungsten powder containing the cobalt component. When forming a molded body, a binder is used as necessary. Moreover, it is preferable that a molded object is a cylindrical shape with a diameter of 1.3-25 mm. Moreover, the length 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., the cobalt component particles and the tungsten particles grow too much to obtain the intended crystal structure. By this step, a cobalt component-containing tungsten sintered body can be obtained. In addition, if the pre-sintered body has a cylindrical shape, the sintered body also has a cylindrical shape.

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 70% 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 cathode component having a high density 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 cobalt 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, the durability of the cathode part support rod may be reduced. On the other hand, if the processing rate is larger than 70%, there is a risk of disconnection due to excessive processing and a decrease in yield. For this reason, the processing rate is 30 to 70%, preferably 35 to 55%.
Moreover, after processing a wire diameter into 1-20 mm, it becomes a cathode component support rod by cut | disconnecting to required length. Further, polishing, heat treatment, and shape processing are performed as necessary.
According to the manufacturing method as described above, the cathode component support rod for a discharge lamp of the present invention can be efficiently manufactured.

(Example)
(Examples 1-5)
Ammonium tungstate (APT) powder having an average particle size of 3 μm was heated to 500 ° C. in the atmosphere to change the ammonium tungstate powder to tungsten oxide powder. Next, cobalt nitrate powder having an average particle diameter of 2 μm was added to the tungsten oxide powder, pure water was added, and then the mixture was stirred and mixed uniformly for 20 hours.
Further, if necessary, a doping material composed of Al, Si, and K was added, and further stirred and uniformly mixed.
Next, the water was completely evaporated to obtain a mixed powder in which cobalt chloride powder and tungsten oxide powder were uniformly mixed. Next, it heated at 500 degreeC in air | atmosphere, and changed the cobalt chloride powder into cobalt oxide.
Next, the tungsten oxide powder was reduced to metallic tungsten powder by heat treatment at 800 ° C. in a hydrogen atmosphere (in a reducing atmosphere). Thus, a mixed powder (first raw material powder) of cobalt oxide powder and metal tungsten powder was prepared.
Separately, an ammonium tungstate (APT) powder having an average particle diameter of 2 μm was heated to 450 ° C. in a nitrogen atmosphere to change the ammonium tungstate powder to tungsten oxide powder. Next, the tungsten oxide powder was reduced to metallic tungsten powder by heat treatment at 700 ° C. in a hydrogen atmosphere (in a reducing atmosphere). Thereby, metal tungsten powder (second raw material powder) was prepared.
Next, the second raw material powder was added to the first raw material powder, and a tungsten powder having a cobalt component of 0.008 wt% in terms of Co was prepared as Example 1. Similarly, a tungsten powder having a cobalt component of 0.01 wt% in terms of Co is Example 2, a tungsten powder having a cobalt component of 0.02 wt% in terms of Co, and a cobalt component of 0.03 wt% in terms of Co. A tungsten powder was prepared as Example 4, and a tungsten powder having a cobalt component of 0.05 wt% in terms of Co was prepared as Example 5.
The contents of Al, Si, and K are as shown in Table 1.

  Next, a cylindrical sintered body (ingot) was obtained under the conditions shown in Table 2 using the raw material powder according to each example, and a cathode component support rod for a discharge lamp was prepared at a predetermined processing rate. In addition, the wire diameter was prepared by a plurality of drawing processes. Moreover, it grind | polished so that surface roughness might be Ra5micrometer or less.

(Comparative Examples 1-2)
A tungsten powder having a cobalt component content of 0.5 wt% in terms of Co was prepared, and a cathode component support rod for a discharge lamp was prepared under the conditions shown in Table 3. In addition, the wire diameter was prepared by a plurality of drawing processes. Moreover, it grind | polished so that surface roughness might be Ra5micrometer or less.

The cathode part support rods in Examples 1 to 5 and Comparative Examples 1 to 3 were examined for the tungsten crystal grain size and aspect ratio of the body part, the grain size of cobalt component particles, the amount of impurities Mo and Fe, and the specific gravity.
Regarding the tungsten crystal grain size and aspect ratio of the body part, a circumferential cross section and a side surface cross section passing through the center of the body part were cut out and examined for an arbitrary unit area of 300 μm × 300 μm. Further, the Mo amount and Fe amount were measured by ICP analysis. The specific gravity was measured by the Archimedes method. Tables 4 and 5 show the results.

Co in the tungsten alloy was present as a solid solution in the tungsten crystal.
Moreover, the durability test was implemented with respect to the cathode component support rod of Examples 1-5 and Comparative Examples 1-2. In the durability test, the cathode component support rod was energized and heated at 1700 ° C. for 30 minutes, and then a three-point bending strength was performed. In addition, the three-point bending strength at room temperature (25 ° C.) was also examined.
Further, as Reference Example 1, a cathode component support rod was produced under the same conditions as in Example 1 except that a tungsten alloy containing 2 wt% thorium oxide was used, and the same measurement was performed. The results are shown in Table 6.

As can be seen from the table, it was found that the cathode part support rod according to this example is excellent in high temperature strength.

DESCRIPTION OF SYMBOLS 1 ... Cathode component support rod 2 ... Body part 3 ... Tip part 4 ... Circumferential cross section 5 ... Side surface cross section 6 ... Discharge lamp 7 ... Cathode component 8 ... Glass tube

Claims (11)

  A cathode component support rod for a discharge lamp made of a tungsten alloy containing 0.005 to 0.1 wt% of a cobalt component in terms of Co. The cathode component support rod has a wire diameter of 1 to 20 mm, and the crystal grain size of tungsten is a unit. When observed at an area ratio of 300 μm × 300 μm in area, the circumferential cross section has a range of 1-80 μm in the range of 90% or more, and the lateral cross section in the range of 10-120 μm has a range of 90% or more. Cathode component support rod.   2. A cathode component support bar for a discharge lamp according to claim 1, wherein the cobalt component forms a solid solution with tungsten.   3. The cathode for a discharge lamp according to claim 1, wherein a crystal grain size of tungsten has an aspect ratio of less than 3 in a circumferential section and an aspect ratio of 3 or more in a side section. Parts support bar.
The discharge according to any one of claims 1 to 3, wherein the Al content is 0.001 to 0.010 wt%. Cathode part support rod for lamp.   The cathode component support rod for a discharge lamp according to any one of claims 1 to 3, wherein the Si content is 0.01 to 0.05 wt%.   The cathode component support rod for a discharge lamp according to any one of claims 1 to 3, wherein the K content is 0.005 to 0.030 wt%.   The cathode component support rod for a discharge lamp according to any one of claims 1 to 6, wherein the Mo content is 0.03 wt% or less. 8. The cathode part support rod for a discharge lamp according to claim 1, wherein the Fe content is 0.02 wt% or less. The cathode component support rod for a discharge lamp according to any one of claims 1 to 8, wherein the specific gravity is within a range of 17 to 19 g / cm ³ . 10. The cathode part support rod for a discharge lamp according to claim 1, wherein the surface roughness Ra is 5 [mu] m or less. The cathode lamp support rod for a discharge lamp according to any one of claims 1 to 10, wherein an applied voltage of the discharge lamp is 100 V or more.

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