JP2008226700A - Thoriated tungsten conductor rod for quartz glass sealing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thoriated tungsten conductor rod which has a proper joining force when sealed to a quartz glass vessel of a light bulb, an electron tube or a similar component and in which cracks are hard to occur in the quartz glass vessel. <P>SOLUTION: The thoriated tungsten conductor rod is disposed in the quartz glass vessel of the light bulb, the electron tube or the similar component, is used by sealing at least a part thereof to the quartz glass vessel, and contains at least one kind selected from among thorium and a thorium compound, and the remaining part is made of a tungsten alloy being substantially tungsten. The total content of the thorium and the thorium alloy in the tungsten lead rod is 0.3 wt.% or more and 0.5 wt.% or less, and a surface roughness Ra in an arbitrary range of 50 μm×50 μm on the surface of the thoriated tungsten conductor rod is 0.30 μm or less. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a quartz glass sealing triated tungsten wire rod excellent in sealing performance with a quartz glass container of a light bulb, an electron tube or similar parts.

  Conventionally, tungsten or a tungsten alloy has been used in various applications because of its excellent heat resistance and mechanical strength. A thorium-tungsten alloy (triated tungsten) to which thorium is added is suitably used as various filaments and coil materials for cathode structures for electron tubes and electron tubes. For such triated tungsten, for example, the content of thorium or thorium compound dispersed in a matrix made of tungsten is set to a predetermined amount, and the average particle size of these particles is set to a predetermined average particle size. It is known that the mechanical strength can be improved (for example, refer to Patent Document 1).

In addition, for triated tungsten, the sintered body is primary processed to have a small diameter to some extent, and then further secondary processed to a finer wire or the like, the carbon used for the primary processing is included. Since the lubricant remains on the surface of the secondary processing material and embrittles the secondary processing material during the secondary processing, for example, by optimizing the surface properties of the secondary processing material, It is known that the lubricant is easily volatilized during the high temperature heat treatment to suppress embrittlement (see, for example, Patent Document 2).
JP 2002-226935 A JP 2006-016696 A

  By the way, conventionally, as the tritated tungsten wire rod sealed in a quartz glass container of a light bulb, an electron tube or similar parts, one having a content of thorium and a thorium compound of 1 to 2% by weight is mainly used. . Except for impurities, tungsten, which is a base metal, and particulate thorium and thorium compounds are present on the surface of such a tritated tungsten conductive rod. The amount of thorium and thorium compound present on the surface is proportional to the amount of thorium and thorium compound contained in the base metal tungsten.

  Of the thorium and thorium compounds present on the surface, thorium oxide easily diffuses into the quartz glass, so that the bonding strength to the quartz glass is improved compared to tungsten, which is the base metal. In addition, in the case of a tritium tungsten wire rod having the same diameter, a surface having a rough surface, that is, a surface having a larger surface roughness has a larger surface area, and the amount of thorium oxide present on the surface also increases. growing.

However, the coefficient of thermal expansion of triated tungsten is approximately 4.6 × 10 ⁻⁶ / K, whereas that of quartz glass is 4.6 × 10 ⁻⁷ / K, There is a difference in thermal expansion coefficient of about 10 times. For this reason, for example, when heated at 1500 ° C. or higher and the tritated tungsten wire rod is sealed on the quartz glass container, if the bonding force is large, the quartz glass container is distorted due to the difference in thermal expansion coefficient. Cracks are likely to occur as a starting point. For general light bulbs, electron tubes or similar parts, the internal pressure in the quartz glass container is used in a state where the internal pressure is positive or negative compared to the atmospheric pressure. This may cause product failure.

  The present invention has been made to solve the above-mentioned problems, and is disposed in a quartz glass container of a light bulb, an electron tube or similar parts, and at least a part thereof is sealed and used in the quartz glass container. Then, it is an object of the present invention to provide a tritiated tungsten wire rod for sealing quartz glass that has an appropriate bonding force when sealed in a quartz glass container and hardly generates cracks in the quartz glass container.

  The quartz glass sealing triated tungsten conductor rod of the present invention is disposed in a quartz glass container of a light bulb, an electron tube or similar parts, and at least a part thereof is sealed and used in the quartz glass container. The tungsten alloy includes at least one selected from thorium compounds, and the balance is substantially tungsten, and the total content of thorium and thorium compounds in the tungsten alloy is 0.3% by weight or more. The surface roughness Ra of the surface is 0.5% by weight or less and an arbitrary range of 50 μm × 50 μm of the surface is 0.30 μm or less.

  The quartz glass sealing triated tungsten wire rod of the present invention has a thorium oxide ratio of 70% of the metal thorium and thorium compound portion present on the surface obtained by analyzing the surface by X-ray photoelectron spectroscopy (XPS). % Or more is preferable. Moreover, it is preferable that the diameter of the triated tungsten wire rod for sealing quartz glass of the present invention is 0.15 mm or more and 0.40 mm or less. Such a fused tungsten wire rod for sealing quartz glass of the present invention is used, for example, as an electrode rod of a high-pressure discharge lamp.

  According to the present invention, the total content of thorium and thorium compound in the tungsten alloy constituting the tritated tungsten wire rod for sealing quartz glass is 0.3 wt% or more and 0.5 wt% or less, and the surface roughness When Ra is 0.30 μm or less, it has an appropriate bonding force when sealed in a quartz glass container of a light bulb, an electron tube or similar parts, and is less likely to cause cracks in the quartz glass container. can do.

Hereinafter, the present invention will be described in detail.
The quartz glass sealing triated tungsten wire rod of the present invention (hereinafter simply referred to as the triated tungsten wire rod) is disposed in a quartz glass container of a light bulb, an electron tube or a similar part, and at least a part thereof is made of quartz. It is used by being sealed in a glass container. The triated tungsten conductor rod of the present invention comprises a tungsten alloy containing at least one selected from thorium and a thorium compound, with the balance being substantially tungsten, and the thorium in this tungsten alloy And the total content of the thorium compound is 0.3 wt% or more and 0.5 wt% or less, and the surface roughness Ra in the range of 50 μm × 50 μm of the surface is 0.30 μm or less. Yes.

  In the present invention, the total content of thorium and thorium compound in the tungsten alloy constituting the triated tungsten conductor rod is set within a predetermined range, and the surface roughness Ra is set within a predetermined range. When sealed in a quartz glass container of an electron tube or similar parts, it can have an appropriate bonding force and can hardly cause cracks in the quartz glass container.

  That is, when the total content of thorium and thorium compounds in the tungsten alloy constituting the triated tungsten conductor rod exceeds 0.5% by weight, the surface thorium oxide contributing to the bonding with the quartz glass container is excessively increased. In addition, the bonding force with the quartz glass container is excessively increased. For this reason, it becomes easy to generate | occur | produce a crack from a distortion in a quartz glass container from the difference with the thermal expansion coefficient of a quartz glass container, and to make it a starting point. In particular, in the conventional triated tungsten conductor rod, the total content of thorium and thorium compound in the tungsten alloy is 1 to 2% by weight, so that it is easy to generate cracks in the quartz glass container.

  On the other hand, when the total content of thorium and the thorium compound is less than 0.3% by weight, the generation of cracks in the quartz glass container is suppressed, but the bonding force with the quartz glass container becomes excessively small. It becomes difficult to maintain the airtightness of the container. Thorium and thorium compounds are added to improve electron emission, but when the content is less than 0.3% by weight, it is difficult to impart sufficient electron emission. In addition, the measurement of the content of thorium and thorium compound in the tungsten alloy is performed, for example, by wet chemical analysis.

  Furthermore, even if the content of thorium and thorium compound is 0.3 wt% or more and 0.5 wt% or less, the surface roughness Ra in the range of an arbitrary 50 μm × 50 μm of the surface of the triated tungsten conductive rod is 0.00. When it exceeds 30 μm, the surface area is substantially increased, and the amount of thorium oxide on the surface contributing to the bonding with the quartz glass container is increased, so that the bonding force with the quartz glass container is also increased. For this reason, it becomes easy to generate | occur | produce a crack from a distortion in a quartz glass container from the difference with the thermal expansion coefficient of a quartz glass container, and to make it a starting point. Here, the surface roughness Ra is an arithmetic average roughness Ra, and the value of the arithmetic average roughness Ra is determined by 3 “Definition and display of defined arithmetic average roughness” of JIS B0601 (1994). It is expressed. The measurement of the surface roughness Ra is performed using, for example, a laser microscope.

The ratio of the metal thorium and the thorium compound contained in the tungsten alloy constituting the triated tungsten conductor rod is not particularly limited, and either one of them may be contained, or both may be contained. Good. Examples of the thorium compound include thorium oxide (ThO ₂ ) and thorium nitrate (Th (NO ₃ ) ₄ ). The thorium compound in the present invention is preferably thorium oxide. In addition, the tungsten alloy may contain raw materials and inevitable components inevitably mixed in the manufacturing process, specifically, aluminum, silicon, potassium and the like. Such inevitable components are preferably 0.1% by weight or less in total in the tungsten alloy.

  About such a triated tungsten conducting rod, the ratio of thorium oxide among thorium and thorium compounds present on the surface obtained by analyzing the surface by X-ray photoelectron spectroscopy (XPS) is 70% or more. It is preferable that

  By analyzing the surface by X-ray photoelectron spectroscopy, the chemical state of the metal on the surface can be analyzed. Depending on the difference in binding energy depending on the chemical state, it can be seen whether it is a metal or an oxide. Moreover, the peak is divided into peaks derived from the respective chemical states, and the composition ratio of the chemical state is known from the area ratio. If the ratio of thorium oxide in the surface thorium and thorium compound analyzed by such X-ray photoelectron spectroscopy is 70% or more, when the quartz glass container is joined, the airtightness of the quartz glass container is increased. It is possible to obtain a bonding force that can maintain the property. In addition, the ratio of this thorium oxide is in the said area ratio.

  That is, thorium oxide present on the surface of the tritated tungsten wire rod contributes to the bonding with the quartz glass container. And when joining with a quartz glass container, vacuum heating etc. are performed with respect to a triated tungsten conducting rod, A part of thorium oxide which exists on the surface is reduced by this vacuum heating etc.

  Therefore, when the proportion of thorium oxide on the surface of the tritated tungsten wire rod is less than 70%, the proportion is further reduced by vacuum heating or the like when actually joining to the quartz glass container, and the airtightness of the quartz glass container is reduced. It is difficult to obtain a bonding force that maintains the property. For this reason, by setting the ratio of thorium oxide on the surface of the tritated tungsten wire rod to 70% or more, even when the quartz glass container is actually joined, the airtightness of the quartz glass container can be maintained. Bonding force can be obtained.

  The diameter of the tritated tungsten wire rod of the present invention is not necessarily limited. For example, the diameter is 0.15 mm or more and 0.40 mm or less so as to be suitably used for a high pressure discharge lamp such as a headlight of an automobile or a railway vehicle. It is preferable that

  Moreover, as a light bulb, an electron tube and similar parts to which the tritated tungsten wire rod of the present invention is applied, at least a quartz glass container is provided, and the triated tungsten wire rod of the present invention is disposed in the quartz glass container. In addition, there is no limitation as long as at least a part of the structure is sealed. For example, a high-pressure discharge lamp such as a headlight of an automobile or a railway vehicle, specifically, a high-pressure mercury lamp, a metal halide lamp, or the like. It is mentioned as what is applied suitably. The triated tungsten wire rod of the present invention is particularly preferably used as an electrode rod in such a high-pressure discharge lamp.

  FIG. 1 shows an example of a high-pressure discharge lamp to which the triated tungsten conductor rod of the present invention is applied, and particularly shows an arc tube that is an inner tube of the high-pressure discharge lamp. The tubular envelope 2 of the arc tube 1 is made of quartz glass, and sealed portions 2a formed by melting and crushing are formed at both ends of the envelope 2 and sandwiched between the sealed portions 2a. This portion is the discharge space 2b.

  Molybdenum foils 3 are hermetically sealed in the respective sealing portions 2a, and further, on the discharge space portion 2b side of each of the molybdenum foils 3 is an inner portion that becomes an electrode rod extending inside the discharge space portion 2b. The conducting wire rod 4 is connected by welding or the like, and an external conducting rod 5 led out to the outside of the enclosing vessel 2 is connected to the opposite side (end portion side of the enclosing vessel 2) by welding or the like. Yes. And the molybdenum foil 3 side of each of the internal conducting bar 4 and the external conducting bar 5 is sealed at the sealing portion 2a in the same manner as the molybdenum foil 3.

  The distal ends of the pair of internal conductor rods 4 on the discharge space 2b side are discharge electrodes. The discharge space 2b is filled with, for example, halide and mercury as a discharge medium. And it is sealed in the outer tube | pipe which consists of hard glass etc. which are not illustrated in this state, and is set as a high voltage | pressure discharge lamp. Here, the internal conductor rod 4 is disposed inside the outer container 2 that is a quartz glass container, and a part thereof is sealed to the sealing portion 2a of the outer container 2, and the tray of the present invention. It is made of a ted tungsten lead wire rod.

  Next, the manufacturing method of the triated tungsten wire rod of this invention is demonstrated. First, powdered ammonium tungstate powder (APT) is made into tungsten oxide by a hydrogen reduction method, and a solution in which thorium or a thorium compound is dissolved in water is mixed with this, and then reduced to produce a mixed powder. As another method, tungsten powder and thorium or thorium compound powder may be put in the same pot and mixed by stirring to produce a mixed powder. Here, by adjusting the amount of thorium or thorium compound solution or powder added, the amount of thorium and thorium compound contained in the finally produced tritated tungsten wire rod is 0.3 wt% or more and 0.0. It can be adjusted within the range of 5% by weight or less.

  Then, the obtained triated tungsten powder is press-molded, and then subjected to current sintering in a hydrogen atmosphere to produce a sintered body. Furthermore, this sintered body is formed into a linear body by repeatedly performing plastic working such as rolling and wire drawing, and annealing for the purpose of crystal control and distortion removal as appropriate.

  Here, generally, in order to obtain a linear body having a diameter of 0.15 to 0.40 mm, the heated sintered body is drawn. At this time, the microscopic unevenness of the wire drawing die used for wire drawing is transferred to the wire body that is the workpiece, and a slight oxide film is formed on the surface of the wire body by heating. The surface of the shaped body is rough, that is, the surface roughness Ra is large. Further, since the wire drawing process is performed using a lubricant, it is necessary to remove the lubricant in consideration of the sealing property with the quartz glass container.

  For this reason, the linear body that has been subjected to wire drawing is straightened into a rod shape, and then the surface is removed by electrolytic polishing, centerless polishing, or the like to finally obtain a triated tungsten wire rod. At this time, by increasing the surface removal rate than usual, that is, in the case of electropolishing, the electropolishing rate (= (1− (cross-sectional area after electropolishing / cross-sectional area before electropolishing)) × 100 [ %]), Or in the case of centerless polishing, by increasing the grain size of the abrasive grains, the surface roughness Ra of the finally obtained triated tungsten wire rod should be 0.30 μm or less. Can do.

  The ratio of thorium oxide in thorium and thorium compounds present on the surface of the triated tungsten wire rod is determined by the heat treatment at the time of processing the triated tungsten wire rod and the contact with the atmosphere. Since it is easily oxidized to thorium oxide, it can be adjusted easily by adjusting such heat treatment and contact with the atmosphere.

  Powdered ammonium tungstate powder (APT) was converted to tungsten oxide by a hydrogen reduction method, and the total content of thorium and thorium compound in the finally obtained tritated tungsten wire rod was 0.1 weight. A solution in which thorium was dissolved in water was mixed so as to be in a range of% to 2.0% by weight, and then reduced to prepare a plurality of mixed powders. Further, this mixed powder was press-molded, and then subjected to electric current sintering in a hydrogen atmosphere to produce a sintered body.

  Then, the sintered body is alternately and repeatedly subjected to plastic working and annealing, and further subjected to electropolishing to adjust the surface roughness Ra to have a diameter of 0.3 mm, a length of 30 mm, and a surface roughness Ra0. A 10 to 1.00 μm sealed tungsten wire rod for sealing test was manufactured. In this case, the ratio of thorium oxide in the thorium and thorium compounds on the surface analyzed by XPS was set to 90%. Further, a tungsten wire rod for sealing test containing no thorium and thorium compound was produced in the same manner except that a solution containing thorium in water was not mixed.

  Next, as shown in FIG. 2, a cylindrical quartz glass piece 10 is prepared, and in this quartz glass piece 10, a tungsten wire rod for sealing test or a tritated tungsten wire rod (hereinafter, these are simply combined). (Referred to as a lead rod for sealing test) 11 was inserted. Thereafter, the quartz glass piece 10 was heated to 1600 ° C., and the end portion was crushed with a carbon die as shown in FIG. 3, and the test wire rod 11 was sealed to obtain a test piece for evaluation. In FIG. 3, a portion that is crushed with a carbon die and to which the test wire rod 11 is sealed is a sealing portion 10 a. FIG. 4 shows a state in which the test specimen for evaluation shown in FIG. 3 is viewed from the crushing direction with a carbon die.

  Here, the quartz glass piece 10 has an outer diameter of 8 mm, an inner diameter of 4 mm, and a length of 20 mm. The sealing portion 10a formed by sealing has an axial length of 15 mm and is crushed by a carbon die. The thickness (length in the vertical direction in the drawing of the sealing portion 10a in FIG. 3) is 4 mm, and the length in the direction perpendicular to the crushing direction (vertical direction in the drawing of the sealing portion 10a in FIG. 4) The width is 10 mm.

  About the test piece for evaluation produced in this way, first, the presence or absence of cracks in the sealing portion 10a was observed, and then the peel strength of the test wire rod 11 was evaluated. The results are shown in Table 1. In Table 1, the surface roughness Ra is 0.10 μm or 0.30 μm, and the total content of thorium and thorium compound is 0.3% by weight or 0.5% by weight. This is an example.

  Moreover, the presence or absence of the crack was performed by observing the sealing part 10a with a magnification of 30 times with a stereomicroscope. The evaluation is performed by measuring the length of the crack extending in the thickness direction or the width direction of the sealing portion 10a starting from the test wire rod 11, and the crack length is actually a high-pressure discharge lamp or the like. What was less than 0.7 mm, which is not a problem, is shown as “good”, indicated by “◯”, what was 0.7 mm or more and less than 1.0 mm, “△”, and what was 1 mm or more, “×” Indicated.

  Moreover, the peeling strength pulled the part exposed from the sealing part 10a among the test conducting rods 11 with the strength of 100g, and confirmed whether the testing conducting bar 11 peeled from the sealing part 10a. In the evaluation, those that did not peel off were shown as "Good" as good, and those that were peeled off were shown as "Poor" as bad.

  As shown in Table 1, a triated tungsten conductor rod having a total content of thorium and a thorium compound of 0.3 wt% or more and 0.5 wt% or less and a surface roughness Ra of 0.30 μm or less. With respect to the above, it can be seen that there is no occurrence of cracks which cause problems when actually used as a high-pressure discharge lamp or the like, and that the peel strength is also good.

  Except that the surface roughness Ra was kept constant at 0.20 μm and the ratio of thorium oxide in the surface thorium and thorium compound analyzed by XPS was changed in the range of 0 to 100%, the same as in [Example 1]. The lead wire for sealing test (tungsten wire rod and triated tungsten wire rod) was manufactured. In addition, the ratio of thorium oxide in the surface thorium and thorium compound is determined at a temperature of 1500 ° C. or higher in a high vacuum atmosphere with thorium oxide formed on the surface by heat treatment during processing of the test wire rod and contact with air It adjusted by reducing to metal thorium by heat processing.

  Next, in the same manner as in [Example 1], a lead wire for sealing test was sealed to a cylindrical quartz glass piece to obtain an evaluation test piece, and first, the presence or absence of cracks in the sealed portion was observed, The peel strength of the test wire rod was evaluated. The results are shown in Table 2.

  As shown in Table 2, with respect to the tritated tungsten conductor rod having a total content of thorium and thorium compound of 0.3 wt% or more and 0.5 wt% or less, thorium oxide in thorium and thorium compounds on the surface thereof It can be seen that good peel strength is maintained when the ratio of is 70% or more.

Sectional drawing which showed an example of the high pressure discharge lamp to which the triated tungsten conducting rod of this invention is applied. The external view which showed the preparation methods of the test piece for evaluation used in an Example. The external view which showed the test piece for evaluation produced in the Example. The top view which showed the state which looked at the test piece for evaluation shown in FIG. 3 from the upper surface.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Arc tube, 2 ... Outer container (quartz glass container), 3 ... Molybdenum foil, 4 ... Internal conductor rod (electrode rod, discharge electrode), 5 ... External conductor rod, 10 ... Quartz glass piece, 10a ... Sealing 11, Conductive bar for sealing test (tungsten conductive bar or tritated tungsten conductive bar)

Claims (4)

Disposed in a quartz glass container of a light bulb, an electron tube or similar parts, and used at least partially sealed in the quartz glass container, comprising at least one selected from thorium and thorium compounds; A triated tungsten wire rod made of a tungsten alloy with the balance being substantially tungsten,
The total content of the thorium and the thorium compound in the tungsten alloy is 0.3 wt% or more and 0.5 wt% or less, and the surface roughness of the surface of the triated tungsten conductor rod is in an arbitrary range of 50 μm × 50 μm. A tritated tungsten wire rod for sealing quartz glass, wherein the thickness Ra is 0.30 μm or less.   The ratio of thorium oxide among thorium and thorium compounds present on the surface obtained by analyzing the surface of the triated tungsten conducting rod by X-ray photoelectron spectroscopy (XPS) is 70% or more. Item 3. A sealed tungsten wire rod for sealing quartz glass according to item 1.   The diameter of the said triated tungsten conducting rod is 0.15 mm or more and 0.40 mm or less, The triated tungsten conducting rod for quartz glass sealing of Claim 1 or 2 characterized by the above-mentioned.   The triated tungsten wire rod for sealing quartz glass according to any one of claims 1 to 3, wherein the triated tungsten wire rod is used as an electrode rod of a high pressure discharge lamp.

Images