JP5814236B2 - End hat for magnetron, method for producing the same, and magnetron - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a magnetron end hat, a method for manufacturing the same, and a magnetron using the same, and more particularly to an end hat for a magnetron capable of extending the life and exhibiting high reliability over a long period of time. And a manufacturing method thereof and a magnetron using the same.

  As shown in FIG. 1, the cathode part of a magnetron used in a microwave oven or the like has a coiled filament 1 that emits thermoelectrons, and a Mo-Ru brazing material 2 at the upper and lower ends of the coiled filament 1, respectively. The upper end hat 3 and the lower end hat 4 made of Mo joined together, the center lead 5 connected and fixed to the upper end hat 3, and the side lead 6 connected to the lower end hat 4. Has been widely known.

  A magnetron is a kind of bipolar tube, and a magnetron is widely used as an electron tube for generating microwaves in microwave communication devices and home appliances. This magnetron generates a microwave by applying a high DC voltage of several kilovolts between a cylindrical cathode (cathode) and an anode (anode) surrounding the cathode. At present, it is widely used as a microwave oven part for cooking food by an induction heating method using a microwave having a frequency of 2450 MHz and an output of about 500 to 1500 W.

  As a conventional method for producing a magnetron end hat, for example, as disclosed in Japanese Patent Publication No. 3-51048 (Patent Document 1), there is a method of sintering Mo powder. Patent Document 1 discloses a method in which Mo powder is formed to produce an intermediate sintered body, an Mo-Ru brazing material intermediate sintered body is placed, and then main sintering is performed. This method improves the bonding strength between the Mo—Ru brazing material and the Mo sintered body (end hat).

  However, there has been a problem in that long-term reliability is reduced (lifetime is short) when used in a magnetron.

Japanese Patent Publication No. 3-51048

  As a result of investigating the cause of the decrease in the reliability, it has been found that the cause is carbon existing on the surface of the Mo sintered body (end hat). Carbon is the resin binder remaining when the Mo molded body is made. When carbon is present on the end hat surface, the end hat surface is easily sputtered when a high voltage is applied in a vacuum tube. Due to this sputtering phenomenon, the surface of the end hat is scraped and eroded and carbon is increased in the vacuum. As a result, it has been found that the output of the magnetron decreases and the life as a magnetron decreases.

  From the above situation, the conventional magnetron end hat has been required to further improve the life.

  The present invention has been made in view of such technical problems, and an object of the present invention is to provide an end hat with high end hat reliability, excellent manufacturing yield and manufacturing efficiency, a manufacturing method thereof, and a magnetron. To do.

In order to achieve the above object, a magnetron end hat according to the present invention is a magnetron end hat comprising a Mo sintered body, and the carbon content in the surface region from the surface of the Mo sintered body to 100 μm is 30 wt. The carbon content in the central region within ± 100 μm from the central point in the thickness direction of the Mo sintered body is 50 to 300 wt. It is characterized by being in ppm.

In the magnetron end hat, the density of the Mo sintered body is preferably 9.6 to 10.0 g / cm ³ .

  Further, in the magnetron end hat, the Mo sintered body has a Mo content of 99.9% by mass or more and, as an impurity element, an Al content of 0.005% by mass or less, and a Ca content. Is 0.003 mass% or less, Cr content is 0.005 mass% or less, Cu content is 0.002 mass% or less, Fe content is 0.03 mass% or less, Mg The content is 0.002% by mass or less, the Mn content is 0.002% by mass or less, the Ni content is 0.008% by mass or less, and the Pb content is 0.002% by mass or less. The Si content is preferably 0.005% by mass or less, and the Sn content is preferably 0.002% by mass or less.

  The magnetron end hat is preferably provided with a Mo-Ru brazing material.

Furthermore, the end hats for the magnetron, wherein the Mo-R u filter cormorants material, as the impurity element is not less than 0.05 wt% carbon content, Fe content is not more than 0.009 mass%, Ni The content is preferably 0.007% by mass or less.

  Moreover, the magnetron according to the present invention is formed using the above-described magnetron end hat.

The method for producing an end hat for a magnetron according to the present invention includes a pressing step of press-molding an end-hat shaped Mo molded body using Mo powder having a purity of 99.9% by mass or more and a resin binder, and the Mo molded body. a first firing step to obtain a first fired body by firing in a redox atmosphere, and this first fired body by firing in a reducing atmosphere to obtain a second fired body second firing step It is characterized by comprising.

In the above-described method for producing a magnetron end hat, the oxidation-reduction atmosphere is preferably wet hydrogen gas. Furthermore, in the first firing step, the wet hydrogen gas flow rate is 0.2 m ³ / hour or more, the maximum temperature reached is 1000 to 1200 ° C., and the holding time at the maximum temperature is 1 to 4 hours. It is preferably carried out under conditions.

Furthermore, in the above-described method for producing a magnetron end hat, the first firing step is preferably performed by raising the temperature from 600 ° C. to the highest temperature over 3 to 7 hours. In the second baking step, the hydrogen gas flow rate is 0.2 m ³ / hour or more, the maximum reached temperature is 1600 to 1900 ° C., and the holding time at the maximum reached temperature is 30 minutes to 5 hours. It is preferably carried out below.

  In the above-described method for producing a magnetron end hat, it is preferable to obtain a barrel polished body by subjecting the second fired body to barrel polishing. Furthermore, it is preferable to press the barrel polishing body.

Further, in the above-described method for producing a magnetron end hat, the obtained magnetron end hat has a carbon content in the surface region from the surface of the Mo sintered body to 100 μm of 30 wt. On the other hand, the carbon content in the central region within ± 100 μm from the central point in the thickness direction of the Mo sintered body is 50 to 300 wt. It is preferable to set it as ppm.

  According to the magnetron end hat of the present invention, since there is little residual carbon in the surface area of the Mo end hat, it is less likely to be sputtered when used as a magnetron. Can be obtained.

  Moreover, according to the manufacturing method of the end hat which concerns on this invention, the end hat of this invention can be manufactured efficiently with a sufficient yield.

It is sectional drawing which shows the structural example of the cathode part of a magnetron. It is sectional drawing which shows the structural example of the end hat for magnetrons. It is sectional drawing which shows the example of a state into which the some molded object was thrown into the baking furnace at once.

  The magnetron end hat according to the present invention is a magnetron end hat made of a Mo sintered body, wherein the carbon content in the surface region from the surface of the Mo sintered body to 100 μm is 30 ppm or less, and the thickness of the Mo sintered body is The carbon content in the central region within ± 100 μm from the central point in the vertical direction is 50 to 300 ppm.

  FIG. 2 shows an example of a magnetron end hat. In FIG. 2, 2 is a brazing material, 3 is an upper end hat (end hat main body), 7 is a center lead mounting hole, 8 is a joint bottom surface between the end hat and the brazing material, and 9 is an end hat and brazing material. It is a joining side surface part. Although the upper end hat is illustrated in FIG. 2, the basic structure is the same in the lower end hat. FIG. 2 illustrates a state where the brazing material 2 is mounted.

  The main body 3 of the end hat is composed of a Mo sintered body. The Mo sintered body is obtained by forming Mo powder and sintering the formed body under predetermined conditions to obtain a Mo sintered body. A preferred production method will be described later.

  The magnetron end hat according to the present invention is made of a Mo sintered body, and as shown in FIG. 2, the carbon content in the surface region 11 from the surface S to 100 μm is 30 ppm or less, and the Mo sintered body has a thickness direction. The carbon content in the central region 12 within ± 100 μm from the central point 10 is 100 to 300 ppm. Here, the “surface” indicates an arbitrary surface S of the end hat main body. The “surface region of 100 μm from the surface” indicates the region 11 from the arbitrary surface S up to 100 μm in the depth direction. In the present invention, the carbon content in the surface region 11 is 30 ppm or less. Preferably, it is 20 ppm or less (including 0 ppm).

  Further, the carbon content in the central region 12 within ± 100 μm from the central point 10 in the thickness direction of the Mo sintered body (end hat main body) is 50 to 300 ppm. Here, the “center region” indicates a region of ± 100 μm from the center point (W / 2) of W with respect to the thickness W of the Mo sintered body in FIG. Although FIG. 2 illustrates the center region of the side wall of the end hat, a sample (sample) in the center region may be collected from the bottom.

  The carbon content is measured by a high frequency combustion-infrared absorption method. In the surface region 11, the surface S is scraped off to 100 μm to obtain a sample. The sample for measuring the carbon content in the central region is measured using a sample obtained by scraping the region of (W / 2) ± 100 μm.

  The present invention is characterized in that when the carbon content in the surface region 11 and the central region 12 is compared, the carbon content in the surface region 11 is relatively very small. If carbon is present in the surface region of the Mo sintered body (end hat main body), the surface of the Mo sintered body is easily sputtered and eroded. Therefore, it is preferable that no carbon exists in the surface region 11. On the other hand, in order to produce a Mo sintered body, Mo powder and a resin binder are mixed to produce a molded body and sintered. When sintered at this time, the resin binder is burned out, but carbon remains as an impurity. For this reason, molding without using a resin binder is also conceivable, but there is a problem that the production yield of the molded body is greatly reduced. However, since the use of a resin binder is inevitable in reality, impurity carbon tends to remain in the Mo sintered body.

  The environment in which the magnetron is used is generally a microwave having a frequency of about 2450 MHz and an output of about 500 to 1500 W. When the magnetron is operated in this use environment, electrons are emitted from the coiled filament 1 toward the anode between the coiled filament 1 and the anode (not shown) in a vacuum vessel (not shown). This emitted electron is used to convert it into a large microwave. For this reason, it is important to efficiently convert the electrons emitted in the vacuum vessel into microwaves.

  For this purpose, it is necessary that there is no impurity in the vacuum vessel so that the movement of electrons is not affected. Among the impurities in the Mo sintered body, carbon is an element that is particularly easily sputtered, and easily becomes an impurity in the vacuum tube. Further, since carbon is sputtered, Mo is easily sputtered together, so that the durability of the end hat is lowered. Therefore, in the present invention, the amount of carbon in the surface region is reduced to a predetermined range.

The density of the Mo sintered body is preferably 9.6 g / cm ³ or more. More preferably, it is 9.6-10.0 g / cm < ³ >. When the density of the Mo sintered body is less than 9.6 g / cm ³ , the strength of the end hat may be insufficient. On the other hand, the theoretical density of Mo is 10.22 g / cm ³ (see Physics and Chemistry Dictionary). When the density is close to the theoretical density, the strength of the Mo sintered body is improved. However, when the density is excessively high, Ru in the brazing material becomes difficult to diffuse. Thus, the density of the Mo sintered body is preferably 9.6 g / cm ³ or more, more preferably in the range of 9.6~10.0g / cm ^3, more preferably 9.6~9.8g / cm ³ range. The density is measured by Archimedes method.

  The Mo sintered body preferably has a Mo (molybdenum) ratio of 99.9% by mass or more. That is, the impurity element is preferably 0.1% by mass or less. More preferably, as the impurity element, the Al content is 0.005 mass% or less, the Ca content is 0.003 mass% or less, the Cr content is 0.005 mass% or less, and the Cu content Is 0.002 mass% or less, Fe content is 0.03 mass% or less, Mg content is 0.002 mass% or less, Mn content is 0.002 mass% or less, Ni The content is 0.008% by mass or less, the Pb content is 0.002% by mass or less, the Si content is 0.005% by mass or less, and the Sn content is 0.002% by mass or less. It is preferable. When there are many impurity elements as described above, it causes a decrease in the strength of the end hat, a decrease in the life of the magnetron, a poor bonding with the Mo—Ru brazing material, and the like.

  Further, as shown in FIG. 2, the end hat preferably has a diameter L of 10 mm or less and a thickness T of 4 mm or less.

  Next, the Mo—Ru brazing material will be described. The Mo—Ru brazing material is preferably a brazing material having a Ru content of 35 to 50 mass%. If the Ru content is less than 35% by mass or excessively more than 50% by mass, the melting point of the brazing filler metal will increase. Since Mo and Ru form a eutectic, Ru 40-45 mass%, which is near the composition of Ru 42.9 mass% -Mo balance, which has the lowest melting point of 1960 ° C., and the Mo remainder are more preferable ranges.

  As a method for lowering the melting point of the brazing material, a method of adding 40% by mass or less of Ni or the like can also be used. The Mo-Ru brazing filler metal has a carbon content as an impurity element of 0.05% by mass or less, an Fe content of 0.009% by mass or less, and a Ni content of 0.007% by mass or less. It is preferable that If a large amount of impurities is contained in the brazing material, it may be scattered in the vacuum vessel.

  The magnetron end hat according to the present invention may have a structure in which an end hat made of a Mo sintered body and a Mo-Ru brazing material are integrally joined. As shown in FIG. 1, the end hat is configured using an upper end hat and a lower end hat, and constitutes a cathode portion of the magnetron. Either the upper end hat or the lower end hat must face the brazing material attachment portion downward. At this time, if the joining of the brazing material and the end hat is weak, the brazing material is peeled off. When the brazing material is peeled off, it becomes defective and the production yield is lowered. Therefore, it is important to make the joint between the end hat and the brazing material strong.

  In the Mo—Ru brazing material integrally bonded to the surface of the Mo sintered body, it is preferable that Ru of the Mo—Ru brazing material is diffused in the Mo sintered body. It is preferable that the region in which Ru is diffused is a region extending 5 μm or more from the bonding interface.

  In addition, a joining interface is the surface of Mo sintered compact (end hat). As a place where the Mo sintered body (end hat) and the brazing material are in contact with each other, the joining bottom surface portion 8 between the end hat and the brazing material is first mentioned. In the joint bottom surface portion 8 between the end hat and the brazing material, Ru in the brazing material diffuses in the direction of the end hat, whereby the joining strength of the brazing material can be improved. In addition, regarding the joint side surface portion 9 between the end hat and the brazing material, similarly, if Ru is diffused in the brazing material, the joining strength of the brazing material is improved.

  As described above, by improving the bonding strength between the end hat and the brazing material, problems such as dropping or peeling of the brazing material are suppressed in the assembly / joining process with the coiled filament 1 and the like. Therefore, it is possible to efficiently manufacture the cathode part of the magnetron with a high yield.

  Next, a method for manufacturing a magnetron end hat according to the present invention will be described. The production method of the magnetron end hat of the present invention is not particularly limited, but the following method can be mentioned as a method of producing efficiently with a high yield.

  The method for producing an end hat for a magnetron according to the present invention includes a pressing step of press-molding an end-hat-shaped Mo molded body using Mo powder having a purity of 99.9% by mass or more and a resin binder, and oxidizing the Mo molded body. A first firing step in which a first fired body is obtained by firing in a reducing atmosphere; and a second firing step in which the first fired body is fired in a reducing atmosphere to obtain a second fired body. It is characterized by.

  First, Mo powder having a purity of 99.9% by mass or more is prepared. The Mo powder preferably has an average particle size of 1 to 8 μm. The amount of impurity elements in the Mo powder is 0.1 mass% or less. More preferably, the Al content as an impurity element is 0.005 mass% or less, the Ca content is 0.003 mass% or less, the Cr content is 0.005 mass% or less, and the Cu content Is 0.002 mass% or less, Fe content is 0.03 mass% or less, Mg content is 0.002 mass% or less, Mn content is 0.002 mass% or less, Ni The content is 0.008% by mass or less, the Pb content is 0.002% by mass or less, the Si content is 0.005% by mass or less, and the Sn content is 0.002% by mass or less. The carbon content is 0.01% by mass or less. It is preferable to use Mo powder with a low content of such impurity elements.

  Next, the Mo powder and the resin binder are mixed and granulated. As the resin binder, a normal resin binder such as PVA (polyvinyl alcohol) can be applied.

Next, the obtained Mo granulated powder is packed in a mold and press-molded to perform a press step of obtaining an end-hat-shaped Mo molded body. At this time, the press pressure is preferably in the range of 3 to 13 ton / cm ² (294 to 1274 MPa). When the press pressure is less than ³ ton / cm ³ , the strength of the molded body is insufficient. On the other hand, when it exceeds 13 ton / cm ² , the density of the molded body becomes excessively high and Ru diffusion hardly occurs. . A preferable press pressure is in the range of 4 to 10 ton / cm ² .

  Next, a first firing step is performed in which the obtained Mo molded body is fired in an oxidation-reduction atmosphere to obtain a first fired body. In the first firing step, it is preferable that the maximum temperature is 1000 to 1200 ° C. and the holding time at the maximum temperature is 1 to 4 hours. The first firing step is positioned as pre-sintering (or intermediate sintering before the main sintering) when the second firing step described later is the main sintering.

  When the maximum temperature reached is less than 1000 ° C., the compacted body is insufficiently densified, while when it exceeds 1200 ° C., it is excessively densified. If it is excessively densified, Ru diffusion does not proceed sufficiently in the step of joining the Mo—Ru brazing material. The redox atmosphere is preferably wet hydrogen gas. Wet hydrogen gas is hydrogen gas containing water vapor.

In the first firing process, the final product is not intended to densify the Mo sintered body (end hat), but by firing in an oxidation-reduction atmosphere, the surface of the Mo sintered body is removed and the Mo firing is performed. This is a process aimed at preventing the union from being oxidized more than necessary. By using wet hydrogen (hydrogen gas containing water vapor), carbon can be removed from the surface of the Mo sintered body. The removed carbon is removed as carbon dioxide (CO ₂ ) or carbon monoxide (CO). This is because water vapor (H ₂ O) heated by heating easily reacts with carbon (C) and is easily removed from the Mo sintered body as carbon monoxide (CO) or carbon dioxide (CO ₂ ).

  Moreover, in a 1st baking process, it is preferable to heat up a molded object over 3 to 7 hours from the temperature of 600 degreeC to the highest attained temperature. In the first firing step, if the rate of temperature rise is too fast, non-uniform portions appear in the disappearance and densification of the binder in the molded body, which may result in a sintered body with non-uniform density. On the other hand, if the temperature is raised over 7 hours or more, the non-uniformity is eliminated, but it takes too much time and the production efficiency is lowered.

In the first firing step, firing in a wet hydrogen-containing atmosphere is preferable in order to prevent the Mo molded body from being oxidized during firing. In this case, from the viewpoint of preventing unnecessary oxidation, after the inside of the firing furnace is replaced with nitrogen gas, the flow rate of the wet hydrogen gas is 0.2 m ³ / H (hour) or more, and further 0.2 to 17 m ³ / It is preferable to control to H (time). It is preferable to adjust so that wet hydrogen gas is supplied as an air flow and fresh wet hydrogen gas is supplied to the Mo molded body. Further, if there is a predetermined gas flow rate, the removed carbon components (carbon dioxide, carbon monoxide) can be removed out of the sintering furnace together with the air flow.

In particular, when a plurality of Mo compacts are arranged on a firing boat (Mo boat) and 200 or more compacts are fired simultaneously in one batch (one-time operation), adjustment of the wet hydrogen gas flow rate is necessary. At that time, it is preferable that a portion where the wet hydrogen gas flow rate in the firing furnace is 2 m ³ / H or more is formed.

  FIG. 3 shows an arrangement example in which the compacts when firing a plurality of Mo compacts in one batch are placed in a firing furnace. In FIG. 3, reference numeral 20 denotes a Mo molded body, 21 denotes a firing container, 22 denotes a firing boat on which the Mo molded body 20 is placed, and 23 denotes a separator that provides a space between the plurality of firing boats 22. is there. A plurality of Mo molded bodies 20 are placed on the firing boat 22.

  At this time, in order to make it easy for hydrogen gas to pass through the gaps between the molded bodies 10, it is preferable that the gaps between the molded bodies 20 be 1 mm or more. A plurality of firing boats 22 on which a plurality of molded bodies 20 are placed are stacked via separators 23. This laminate is placed in the firing container 21.

  By disposing the above firing containers in a firing furnace, 200 or more, further 400 or more, and even 2000 or more molded bodies can be fired at one time in one batch. In addition, it is preferable that the firing boat, the separator, and the firing container are made of Mo which is a heat-resistant metal. Moreover, you may use the baking boat which the coating of the oxide ceramics is given as needed.

  Next, a second firing step is performed in which the first fired body is fired in a hydrogen-containing atmosphere to obtain a second fired body. The second firing step is a step corresponding to a so-called main sintering step.

In the second firing step, it is preferable that the maximum reached temperature of the first fired body is 1600 to 1900 ° C., and the holding time at the maximum reached temperature is 30 minutes to 5 hours. If the maximum temperature reached is less than 1600 ° C., densification does not proceed sufficiently, and the density of the second fired body tends to be less than 9.6 g / cm ³ .

  On the other hand, if the maximum temperature exceeds 1900 ° C., the melting point of the brazing material is close to 1960-2050 ° C., so that the brazing material may melt more than necessary. If the brazing filler metal melts more than necessary, there will be a problem in joining the filament and leads when forming the cathode portion. A preferred maximum temperature is in the range of 1650-1800 ° C.

  Further, if the holding time at the maximum temperature is less than 30 minutes, the Mo sintered body is not sufficiently densified, and if it exceeds 5 hours, Ru from the brazing material to the Mo sintered body is excessively diffused. There is a risk that.

  Moreover, it is necessary to perform a 2nd baking process in a hydrogen containing atmosphere in order to prevent the oxidation of Mo sintered compact similarly to a 1st baking process. For this reason, it is preferable to employ a method of supplying hydrogen gas after first replacing the inside of the firing furnace with nitrogen gas. Moreover, since it is preferable to supply fresh hydrogen gas, it is preferable to adjust a hydrogen gas stream on the same conditions as a 1st baking process. In particular, in order to obtain a large number of sintered bodies of 200 or more, further 400 or more in one batch, it is necessary to adjust the flow rate of wet hydrogen gas or hydrogen gas.

  Here, the process of arranging the Mo—Ru brazing material will be described. There are roughly two methods for arranging the Mo-Ru brazing material.

  The first method is a method of performing a brazing material arranging step of arranging a ring-shaped Mo—Ru brazing material on the first fired body. In this arrangement step, a method of applying a Mo-Ru brazing paste at a predetermined position, a method of placing a brazing material previously formed into a ring shape, or a heat-treated brazing material formed into a ring shape is arranged. The method etc. are mentioned. In order to efficiently perform the arranging step, it is preferable to use a ring-shaped brazing material obtained by heat-treating a Mo-Ru brazing material formed into a ring shape. The heat treatment increases the strength of the ring-shaped Mo—Ru brazing material, so that the handleability of the ring-shaped brazing material is improved. That is, when the ring-shaped brazing material is disposed on the first fired body, the problem that the ring-shaped brazing material is broken is less likely to occur. The diameter size of the ring-shaped brazing material is adjusted to the brazing material mounting portion of the end hat (corresponding to the joint surface 8 with the brazing material), and the thickness is preferably 0.3 to 2.5 mm.

  Examples of the second method include a method of applying a Mo-Ru brazing paste to the second fired body, a method of fixing a ring-shaped brazing material by laser treatment after the placement, and the like.

  The first method uses a step of arranging a brazing material between the first baking step and the second baking step, and the second method arranges the brazing material after the second baking step. It is a method using a process.

  The basic magnetron end hat defined in the present invention can be manufactured by the above steps. Hereinafter, additional steps that can further increase the yield will be described.

  In the second sintered body, Mo protrusions (burrs) may be partially formed. In this case, it is preferable to perform barrel polishing on the second fired body because a barrel polished body free from burrs can be obtained.

  The barrel polishing conditions are arbitrary, but the following method is given as an example. For example, when using a centrifugal barrel machine, the pot capacity is set to 10 to 15 liters, and 4000 to 15000 pieces of Mo sintered body are filled in the pot in one batch, and further, the number of revolutions is set with abrasives and water. Defects such as burrs are removed by performing barrel polishing for about 3 to 10 minutes while rotating the pot at 60 to 130 / min. After the barrel polishing process, the barrel polishing body is dried.

  Next, it is preferable to carry out a step of pressing the barrel polishing body. When the brazing material surface has a wavy shape by pressing, it can be made flat. The barrel polishing described above is effective for removing burrs formed on the outer peripheral surface of the Mo sintered body (end hat), but it is sufficiently effective for removing burrs on the inner surface where there are burrs on the surface of the brazing material. Cannot be obtained.

  Further, if the abrasive is small, burrs may be generated in the brazing material by the barrel polishing process. In addition, if the brazing material is deburred, it is predicted that the absolute amount of the brazing material will be insufficient, which may adversely affect the brazing operation of the filament in a subsequent process.

  Therefore, it is effective to give the effect of adjusting the shape of the brazing material by pressing the barrel polishing body.

It is also possible to remove burrs that could not be removed by barrel polishing. Arranging such a shape (deburring) is called sizing. The pressing pressure for carrying out this sizing is arbitrary, but the pressing pressure is preferably 6 ton / cm ² or less (588 MPa or less).

  It is also effective to heat and press the press mold at a temperature of 400 to 750 ° C. It is particularly effective to warm the mold in order to adjust the shape of the brazing material.

  Moreover, when press oil (lubricating oil) is apply | coated and pressed to a metal mold | die at the time of a press work, it can suppress effectively that a metal mold | die and Mo sintered compact (end hat) adhere. When press oil is used, it is preferable to carry out a step of degreasing the pressed product. In this degreasing step, it is effective to heat at a temperature at which the press oil volatilizes.

  Moreover, it is preferable to perform the 3rd baking process which heat-processes the degreased product. When barrel polishing, sizing, or press oil degreasing is performed, the end hat may be oxidized. Therefore, it is preferable to perform a step of removing surface oxide by heat treatment in a hydrogen atmosphere. The heat treatment conditions are preferably carried out in a hydrogen gas stream at a maximum temperature of 600 to 900 ° C. If the temperature is less than 600 ° C., it takes time until the oxide removing effect is exhibited. On the other hand, if the temperature exceeds 900 ° C., no further effect can be obtained, which causes an increase in manufacturing cost.

  If it is the above manufacturing method, the end hat for magnetrons can be manufactured efficiently with high yield. Further, for example, when the firing operation is performed in a state where the firing boats are stacked in multiple stages as shown in FIG. 3, 200 or more Mo molded bodies per batch can be sintered simultaneously. By using the magnetron end hat manufacturing process according to the present invention, the manufacturing yield can be increased to 80% or more even when 200 or more treatments are performed per batch. Moreover, the manufacturing yield can be improved to 99% or more by performing barrel processing, press processing (sizing), degreasing, and a third firing step thereafter.

[Example]
Next, the present invention will be specifically described with reference to the following examples.

(Examples 1-5)
A high-purity Mo powder having an average particle size of 3 μm and a purity of 99.9% or more was prepared. As a result of investigating the impurity element amount of the high-purity Mo powder, the impurity element (nonvolatile component) was 0.08% by mass or less. Each impurity element component has an Al content of 0.005 mass% or less, a Ca content of 0.003 mass% or less, a Cr content of 0.005 mass% or less, and a Cu content of 0. 0.002 mass% or less, Fe content is 0.03 mass% or less, Mg content is 0.002 mass% or less, Mn content is 0.002 mass% or less, Ni content Is 0.008 mass% or less, Pb content is 0.002 mass% or less, Si content is 0.005 mass% or less, Sn content is 0.002 mass% or less, carbon The content was 0.01% by mass or less.

(Process A: Molding process)
Next, the Mo powder was mixed with a resin binder (PVA), granulated, filled in a mold, and press molded. The press pressure (molding pressure) was as shown in Table 1. The size of the molded body was such that the diameter L of the end hat was 7.5 mm × thickness was T2.5 mm, the inner diameter was 3.3 mm, and the inner diameter of the place where the brazing material was placed was 3.9 mm.

(Process B: First firing process)
As shown in FIG. 3, a Mo boat having a length of 320 mm × a width of 220 mm × a thickness of 15 mm was prepared as the firing boat 22 and 500 Mo molded bodies 20 were placed (the gap between the molded bodies was 1 mm or more). . 10 stages of firing boats 22 were stacked on the firing container 21 through the separator 23 (5000 pieces per batch). This was put into a push-type firing furnace and fired under the firing conditions shown in Table 2. In charging, the inside of the furnace was replaced with nitrogen gas, and then a predetermined amount of wet hydrogen gas shown in Table 2 was supplied.

(Step C: Second firing step)
About the 1st baking body prepared as mentioned above, the 2nd baking process was implemented on the baking conditions shown in Table 3. FIG. In the second firing step, firing boats similar to those in the first firing step were stacked and placed in a firing container. The firing container was put into a push-type second firing furnace. In firing, the furnace was replaced with nitrogen gas, and then the hydrogen gas flow rate was adjusted.

  The main part of the magnetron end hat according to Examples 1 to 5 was prepared by combining the molding process A, the first firing process B, and the second firing process C shown in Tables 1 to 3 as follows. .

Example 1: A1 → B1 → C1
Example 2: A1 → B2 → C2
-Example 3: A2->B2-> C2
Example 4: A2 → B3 → C3
Example 5: A3 → B4 → C4
In addition, as a comparative example 1, the process B4 of the example 5 was processed in a process in which the wet hydrogen gas was changed to the hydrogen gas to prepare a magnetron end hat according to the comparative example 1.

  For the magnetron end hats according to Examples 1 to 5 and Comparative Example 1 thus prepared, the density of the Mo sintered body (end hat) and the production yield were measured. Further, the carbon content (wt. Ppm) in the surface region (region from the surface to a depth of 100 μm) and the central region (region of ± 100 μm from the center point (W / 2) of the thickness W of the side wall) was measured. .

The density was measured by the Archimedes method. The production yield was measured by the ratio of non-defective products per 5000 batches. The carbon content was measured by a high frequency combustion-infrared absorption method. The measurement results are shown in Table 4 below.

As is apparent from the results shown in Table 4, the magnetron end hats according to the respective examples had a density of 9.6 g / cm ³ or more and a production yield of 90% or more. Further, the end hat according to each example had a carbon content (carbon content) in the surface region lower than that in the central region.

  Next, the magnetron was manufactured using the end hat which consists of Mo sintered compact concerning each Example and a comparative example, and the lifetime was measured.

  That is, Mo-Ru brazing paste (Mo: 57 wt%, Ru: 43 wt%, impurity carbon is 0.05 wt% or less, Fe is 0.009 wt% or less, Ni is 0.007 wt% or less at a predetermined position of the end hat. Then, as shown in FIG. 1, the center lead 5, the side lead 6, and the coiled filament 1 were brazed to produce a cathode assembly. This was incorporated into a vacuum tube to form a magnetron. A microwave oven was constructed using this magnetron, and the lifetime was measured. The lifetime was measured by measuring the presence or absence of erosion in the Mo sintered body (end hat surface) after 1000 sets and 10,000 sets after 1500 W × 5 minutes as one set. The results are shown in Table 5.

  As apparent from the results shown in Table 5, there was no problem after 1000 sets and after a short time, but when the set time was as long as 10,000 sets, erosion was confirmed in the cathode structure having a large amount of carbon in the surface region as in Comparative Example 1. It was. When eroded, carbon diffuses into the vacuum tube, reducing the function of the magnetron. In other words, it was confirmed that the magnetron using the end hat according to each example without erosion has high long-term reliability.

(Examples 6 to 10)
Next, an embodiment in which the following steps are incorporated as a method for further increasing the manufacturing yield will be described.

  The following steps were performed for the magnetron end hats according to Example 2 and Example 3.

(Process D: Brazing material arrangement process)
The following process was performed as a brazing material arrangement process.

  Step D1: A step of placing a pre-sintered Mo—Ru brazing material was placed between the first firing step (Step B) and the second firing step (Step C).

  Step D2: After Step C, a step of joining by laser irradiation was performed after placing a pre-sintered Mo-Ru brazing material.

(Process E: Barrel polishing process)
Each magnetron end hat was mixed with an abrasive and water, and a barrel polishing step was performed under the conditions shown in Table 6 below (one batch amount, pot rotation speed, polishing time).

(Process F: Sizing)
Each magnetron end hat subjected to step E was subjected to a sizing step in which the pressing pressure shown in Table 7 below was applied to correct the deformation of the brazing material. Note that a lubricating oil was applied to the mold when the pressing pressure was applied.

(Process G: Degreasing)
Each magnetron end hat subjected to Step F was degreased to remove the lubricating oil, and the degreasing step was performed.

(Process H: 3rd baking process)
Each magnetron end hat subjected to Step G was fired under the conditions shown in Table 8 below, and a third firing step was performed.

  And with respect to the said Example 2 and 3, each process of the said brazing material arrangement | positioning process D, the barrel polishing process E shown in Tables 6-8, the sizing process F, the degreasing process G, and the 3rd baking process H is as follows. In combination, magnetron end hats according to Examples 6 to 10 were prepared.

Example 6:
Example 2 → (Process D1) → Process E1 → Process F1 → Process G → Process H3
Example 7:
Example 2 → (Process D1) → Process E2 → Process F1 → Process G → Process H1
Example 8: Example 2 → Step D2 → Step E3 → Step F2 → Step G → Step H2
Example 9: Example 3 → Step D2 → Step E2 → Step F1 → Step G → Step H1
Example 10:
Example 3-> Process E3-> Process G-> Process H2-> Solder paste application drying The magnetron end hats according to Examples 6 to 10 were measured for production yield in the same manner as in Example 1. The measurement results are shown in Table 9 below.

  As is apparent from the results shown in Table 9, according to the magnetron end hat according to each example in which the barrel polishing step E, the sizing step F, the degreasing step G, and the third firing step H were performed, It became possible to make the magnetron end hats that were poor in appearance due to burrs and deformed brazing materials.

  Moreover, according to the method concerning a present Example, even when various methods were applied as the brazing material arrangement | positioning process D, it became clear that a manufacturing yield could be improved significantly. In addition, as a result of measuring the carbon content of the surface region of the end hat according to each example, there was no change from the state of Example 2 and Example 3. For this reason, it was confirmed that the end hats according to Examples 6 to 10 also have high long-term reliability.

  According to the magnetron end hat of the present invention, since there is little residual carbon in the surface area of the Mo end hat, it is less likely to be sputtered when used as a magnetron. Can be obtained. Moreover, according to the manufacturing method of the end hat which concerns on this invention, the end hat of this invention can be manufactured efficiently with a sufficient yield.

DESCRIPTION OF SYMBOLS 1 ... Coiled filament 5 ... Center lead 6 ... Side lead 7 ... Center lead attachment hole 8 ... End hat and brazing material joining bottom part 9 ... End hat and brazing material joining side part 10 ... Thickness center point DESCRIPTION OF SYMBOLS 11 ... Surface area | region 12 ... Center area | region 20 ... Mo molded object 21 ... Container for baking 22 ... Firing boat 23 ... Separator S ... Surface

Claims (14)

In the magnetron end hat made of a Mo sintered body, the carbon content in the surface region from the surface of the Mo sintered body to 100 μm is 30 wt. The carbon content in the central region within ± 100 μm from the central point in the thickness direction of the Mo sintered body is 50 to 300 wt. Magnetron end hat characterized by being in ppm. 2. The magnetron end hat according to claim 1, wherein a density of the Mo sintered body is 9.6 to 10.0 g / cm ³ .   The Mo sintered body has an Mo content of 99.9% by mass or more, an Al content of 0.005% by mass or less, and a Ca content of 0.003% by mass or less as impurity elements. The Cr content is 0.005 mass% or less, the Cu content is 0.002 mass% or less, the Fe content is 0.03 mass% or less, and the Mg content is 0.002 mass% or less. Mn content is 0.002% by mass or less, Ni content is 0.008% by mass or less, Pb content is 0.002% by mass or less, and Si content is 0.005% by mass. 3 or less, and Sn content is 0.002 mass% or less, The end hat for magnetrons of Claim 1 or Claim 2 characterized by the above-mentioned.   The magnetron end hat according to any one of claims 1 to 3, wherein a Mo-Ru brazing material is provided. The Mo-R u filter cormorants material, as the impurity element is not less than 0.05 wt% carbon content, and the Fe content is less 0.009 wt%, Ni content of less 0.007 wt% The end hat for a magnetron according to claim 4, wherein   A magnetron using the magnetron end hat according to any one of claims 1 to 5. A press step of press-molding an end-hat-shaped Mo molded body using Mo powder having a purity of 99.9% by mass or more and a resin binder, and firing the Mo molded body in an oxidation-reduction atmosphere to perform first firing a first firing step of obtaining the body, production of magnetrons for end hat, characterized by comprising a this first fired body by firing in a reducing atmosphere to obtain a second fired body second firing step Method.   8. The method of manufacturing a magnetron end hat according to claim 7, wherein the oxidation-reduction atmosphere is wet hydrogen gas. In the first firing step, the wet hydrogen gas flow rate is 0.2 m ³ / hour or more, the maximum temperature reached is 1000 to 1200 ° C., and the holding time at the maximum temperature is 1 to 4 hours. The method for manufacturing an end hat for a magnetron according to claim 7 or 8, wherein   10. The magnetron end hat according to claim 7, wherein in the first baking step, the temperature is raised from a temperature of 600 ° C. to a maximum temperature over 3 to 7 hours. Production method. In the second baking step, the hydrogen gas flow rate is 0.2 m ³ / hour or more, the maximum reached temperature is 1600 to 1900 ° C., and the holding time at the maximum reached temperature is 30 minutes to 5 hours. The method for producing a magnetron end hat according to any one of claims 7 to 10, wherein the method is performed.   The method for producing a magnetron end hat according to any one of claims 7 to 11, wherein a barrel polished body is obtained by subjecting the second fired body to barrel polishing.   13. The method for producing a magnetron end hat according to claim 12, wherein the barrel polishing body is pressed. The obtained magnetron end hat had a carbon content in the surface region from the surface of the Mo sintered body to 100 μm of 30 wt. On the other hand, the carbon content in the central region within ± 100 μm from the central point in the thickness direction of the Mo sintered body is set to 100 to 300 wt. The method for producing an end hat for magnetron according to claim 7, wherein the content is ppm.

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