JP7019440B2 - Rotating anode X-ray tube and its manufacturing method - Google Patents

Description

Embodiments of the present invention relate to a rotating anode X-ray tube and a method for manufacturing the same.

Generally, a rotating anode type X-ray tube includes a cathode and an anode target arranged in a vacuum vessel, the anode target is fixed to an anode target support shaft, and the anode target support shaft is connected to a rotating body. , The rotating body is supported by the fixed body via the anode. An electromagnetic coil is arranged outside the vacuum vessel, and by applying an electric current to the electromagnetic coil, the electron beam emitted from the cathode is applied to the rotating anode target surface to emit X-rays while rotating the rotating body at high speed. ing.

In Patent Document 1, the connecting portion between the anode target support shaft and the rotating body is joined with a brazing material made of nickel (Ni) alloy instead of the commonly used brazing material made of copper (Cu) alloy. Is disclosed.

Japanese Unexamined Patent Publication No. 11-045675

However, in a repetitive environment at high temperature such as a rotating anode X-ray tube, when the connecting part between the anode target support shaft and the rotating body is joined with a brazing material of nickel alloy, it is compared with a copper (Cu) brazing material. Although the strength is high, the toughness of the joint may decrease, and as a result, the joint may deteriorate, the rotation of the anode target may become unbalanced, and abnormal vibration may occur.

It is an object of the present invention to provide a rotating anode X-ray tube and a method for manufacturing the same, in which the anode target can continue to maintain stable rotation even in repeated operation at a high temperature.

The rotating anode X-ray tube according to one embodiment includes an anode target that generates X-rays by collision of electrons emitted from a cathode, an anode target support shaft to which the anode target is fixed, and the anode target support shaft. A rotating body connected to the rotating body and a fixed body connected to the rotating body via a bearing are provided, and a connecting portion between the anode target support shaft and the rotating body is joined with a brazing material. The material has a blending ratio of 27 to 50% by weight of iron, 20 to 30% by weight of chromium, 30 to 50% by weight of nickel and 5 to 10% by weight of phosphorus, and a melting temperature of 1000 ° C. to 1100% by weight.

The method for manufacturing a rotating anode X-ray tube according to an embodiment includes a step of connecting an anode target support shaft to which an anode target is fixed and a rotating body connected to the fixed body via a bearing, and the anode target support. The brazing material is provided with a step of placing a brazing material on the connecting portion between the shaft and the rotating body, melting the brazing material in the furnace, and brazing the connecting portion, and the brazing material is 27 to 50% by weight of iron and chromium. The mixing ratio is 20 to 30% by weight, 30 to 50% by weight of nickel and 5 to 10% by weight of phosphorus, and the melting temperature is 1000 ° C. to 1100% by weight.

FIG. 1 is a vertical sectional view showing a schematic configuration of a rotating anode X-ray tube according to an embodiment. FIG. 2 is an enlarged cross-sectional view showing a portion A shown in FIG.

Hereinafter, the rotating anode X-ray tube and the manufacturing method thereof according to the embodiment will be described in detail with reference to the drawings. In addition, in order to make the explanation clearer, the drawings may schematically represent the width, thickness, shape, etc. of each part as compared with the actual embodiment, but they are merely examples and are merely examples of the present invention. It does not limit the interpretation. Further, in the present specification and each figure, the same reference reference numerals may be given to the components exhibiting the same or similar functions as those described above with respect to the above-mentioned figures, and the overlapping detailed description may be omitted as appropriate. ..

As shown in FIG. 1, the rotating anode X-ray tube 1 includes a vacuum enclosure 3, a cathode 5 housed in the vacuum enclosure 3, an anode target 7, an anode target support shaft 9, and a rotating body. An 11 and a fixed body 13 are provided, and a stator coil 15 is provided on the outside of the vacuum enclosure 3.

The inside of the vacuum enclosure 3 is held in a vacuum.

The cathode 5 is a member that emits electrons.

The anode target 7 has a disk shape, and X-rays are generated by collision of electrons emitted from the cathode 5 with the surface 7a facing the cathode 5. The anode target 7 is made of a heavy metal having a high melting point, and as the heavy metal, for example, molybdenum (Mo), tungsten (W) or an alloy thereof is used.

The anode target 7 is supported by the anode target support shaft 9 at the center of the disk, and is fixed to the upper end of the anode target support shaft 9 with a nut 17.

The lower end portion 9a of the anode target support shaft 9 is connected to the rotating body 11 by the connecting portion 12. The anode target support shaft 9 is made of, for example, molybdenum (Mo), tungsten (W), or an alloy thereof.

The rotating body 11 is composed of an outer cylindrical rotating body 11a and an inner cylindrical rotating body 11b arranged on the inner peripheral side of the outer cylindrical rotating body 11a. The outer cylindrical rotating body 11a and the inner cylindrical rotating body 11b each have a bottomed cylindrical shape. A fixed body 13 is connected to the inner peripheral side of the inner cylindrical rotating body 11b via a dynamic pressure sliding bearing (bearing) 19. A disk-shaped flange 14 is fixed to the lower opening of the rotating body 11.

The outer peripheral surface portion 22 of the outer cylindrical rotating body 11a is made of copper or an alloy thereof, and the bottom portion 23 is made of an iron-based metal, for example, pure iron. The inner cylindrical rotating body 11b is made of an iron-based metal, for example, pure iron.

Here, with reference to FIG. 2, the connecting portion 12 between the anode target support shaft 9 and the rotating body 11 will be described. At the lower end portion 9a of the anode target support shaft 9, a male screw 21 is formed on the lower side of the flange portion 19 and the flange portion 19.

On the other hand, a hole 25 is formed in the center of the bottom 23 of the outer cylindrical rotating body 11a. A concave step portion 27 and a female screw 29 are formed below the step portion 27 in the hole portion 25. In the connecting portion 12, the male screw 21 formed on the lower end portion 9a of the anode target support shaft 9 is screwed to the female screw 29 formed on the bottom portion 23 of the outer cylindrical rotating body 11a. Further, in the bottom portion 23, the flange portion 19 of the anode target support shaft 9 is arranged on the inner circumference of the step portion 27, and melts between the inner peripheral surface of the step portion 27 and the outer peripheral surface of the flange portion 19. The brazing filler metal 31 is poured into the connecting portion 12, and the connecting portion 12 between the lower end portion 9a of the anode target support shaft 9 and the outer cylindrical rotating body 11a is screwed by screws 21 and 29 and joined by the brazing filler metal 31. There is. In the present specification, the brazing filler metal 31 indicates the brazing filler metal after melting, but the brazing filler metal before melting has the same composition and melting temperature.

The brazing filler metal 31 melted at the step portion 27 also flows between the male screw 21 and the female screw 29 due to the capillary phenomenon, and the male screw 21 and the female screw 29 are also joined by the brazing filler metal 31.

In the components of the brazing filler metal 31, the weight ratios of iron, chromium, nickel and phosphorus are 27 to 50% by weight of iron, 20 to 30% by weight of chromium, 30 to 50% by weight of nickel and 5 to 10% by weight of phosphorus. With these weight ratios, it is possible to have a well-balanced strength, toughness and hardness, and the melting temperature can be easily set in the range of 1000 ° C to 1100 ° C.

The melting temperature of the brazing filler metal 31 is set to 1000 ° C. to 1100 ° C. within this temperature range, which can be close to the melting temperature of the conventional brazing filler metal containing copper (Cu) as a main component. This is because the existing furnace can be used for melting. Further, according to the brazing filler metal 31 of the present embodiment, since it can be melted at substantially the same temperature as the copper (Cu) brazing filler metal used conventionally, it is not necessary to change the material of the anode target support shaft 9 and the rotating body 11.

Further, in the brazing filler metal 31 according to the present embodiment, the weight ratio is 27 to 50% by weight of iron and 20 to 30% by weight of chromium because the corrosion resistance and heat resistance can be improved and the connection strength can be prevented from being lowered. be. That is, the iron-chromium alloy brazing material has a higher high temperature strength than the copper brazing material. For example, the copper brazing material has a remarkable strength decrease at about 300 ° C., but the iron-chromium alloy brazing material is used at 600 to 700 ° C. Even in that case, the decrease in strength is small.

Further, in the case of a nickel brazing material containing nickel (Ni) as a main component, the hardness is high and the material is hard and brittle, so that the joint portion tends to deteriorate due to repeated high and low temperatures. On the other hand, the iron-chromium brazing material 31 according to the present embodiment has toughness and less progress of deterioration than the nickel brazing material.

Then, by adding 30 to 50% by weight of nickel to the iron-chromium alloy, a predetermined hardness can be obtained, and a balance between toughness and hardness can be obtained.

Further, according to the brazing filler metal 31 according to the present embodiment, when the material of the anode target support shaft 9 to be brazed is Mo or Mo alloy, Mo is slightly diffused in the brazing filler metal and alloyed. As a result, the joint strength of the connecting portion 12 can be further increased.

The brazing filler metal 31 is more preferably in a blending ratio of 27 to 30% by weight of iron, 20 to 22% by weight of chromium, 42 to 46% by weight of nickel and 7 to 10% by weight of phosphorus. With a blending ratio in this range, it is easier to bring the melting temperature closer to 1000 ° C to 1100 ° C, and the strength is more balanced than that of conventional copper (C) brazing material and nickel (Ni) brazing material. This is because it can have toughness and hardness.

As a specific compounding ratio, for example, when iron was 30% by weight, chromium was 20% by weight, nickel was 40% by weight, and phosphorus was 10% by weight, it could be melted at about 1050 ° C., which is close to that of copper brazing material or Ni brazing material.

Next, a method for manufacturing a rotating anode X-ray tube according to the first embodiment will be described.

To join the anode target 7 and the anode target support shaft 9, the anode target support shaft 9 is fitted into the central hole of the disk-shaped anode target 7 and fixed with a nut 17. On the other hand, on the anode target support shaft 9, a male screw 21 is formed on the outer peripheral surface of the lower end portion 9a.

In the rotating body 11, in the cylindrical outer cylindrical rotating body 11a, a female screw 29 in which the male screw 21 of the anode target support shaft 9 is screwed is formed on the bottom portion 23. Further, a recessed step portion 27 into which the flange portion 19 of the anode target support shaft 9 is inserted is formed on the upper portion of the female screw 29.

After that, the male screw 21 of the anode target support shaft 9 is screwed into the female screw 29 formed on the bottom 23 of the outer cylindrical rotating body 11a to connect the anode target support shaft 9 and the outer cylindrical rotating body 11a, and then the connecting. In the portion 12, the brazing filler metal 31 is arranged around the stepped portion 27 (not shown), and the brazing filler metal 31 is melt-bonded in the furnace.

When the furnace has a hydrogen atmosphere, the atmosphere inside the furnace when the brazing filler metal 31 is brazing is preferably a hydrogen atmosphere having a dew point of −37 ° C. or lower. This is because the brazing material 31 is an iron material containing chromium to prevent oxidation in a hydrogen heating environment. That is, when the dew point is higher than −37 ° C., the brazing portion may be oxidized by the moisture in the furnace. Since the dew point in the hydrogen atmosphere is specified in order to suppress oxidation due to moisture, it is desirable that the dew point is as low as possible if it is −37 ° C. or lower.

On the other hand, when the furnace is a vacuum furnace and the brazing environment of the brazing filler metal 31 is vacuum heating, the degree of vacuum from the vapor pressure of the molten brazing filler metal is 1 to 1 × 10 ^-3 (Pa). Is preferable. That is, if it is higher than 1 Pa (Pascal), there is a risk of oxidation due to moisture, and if it is lower than 10 ^-3 (Pa), the vapor of the molten brazing material diffuses too much.

In the anode target 7, the anode target support shaft 9 and the rotating body 11 assembled in this way, a fixed body 13 is provided on the inner peripheral side of the inner cylindrical rotating body 11b via a dynamic pressure sliding bearing 19, and a vacuum enclosure is provided. Install in 3. Further, a cathode 5 is attached to the vacuum enclosure 3. Then, a stator coil 15 is provided outside the vacuum enclosure 3, and the rotating anode X-ray tube 1 is assembled.

In the rotating anode X-ray tube 1, when the stator coil 15 is energized, the rotating body 11 rotates due to its electromagnetic force, and the electrons emitted from the cathode 5 face the facing surface of the anode target 7 with respect to the rotating anode target 7. X-rays are generated and the X-rays are emitted to the outside of the vacuum anode 3.

According to the present embodiment, in the connecting portion 12 between the anode target support shaft 9 and the rotating body 4, the male screw 21 formed at the lower end portion 9a of the anode target supporting shaft 9 and the outer cylindrical rotating body 11a screwed therein. The female screw 29 of the bottom portion 23 is connected by screwing, and the flange portion 19 formed at the lower end portion 9a of the anode target support shaft 9 and the step portion 27 of the bottom portion 23 are brazed with the brazing material 31. The bonding strength of the connecting portion 12 is high.

Further, the molten brazing material 31 also enters between the male screw 21 and the female screw 29 by a capillary phenomenon, and the threaded portion is also brazed and adhered, so that the strength of the connecting portion 12 can be further increased.

The brazing filler metal 31 has a blending ratio of 27 to 50% by weight of iron, 20 to 30% by weight of chromium, 30 to 50% by weight of nickel, and 5 to 10% by weight of phosphorus. It can be provided with the obtained strength, toughness and hardness, and can maintain stable rotation of the anode target 7 even if the rotating anode X-ray tube 1 is repeatedly driven at a high temperature.

Further, the bottom of the outer cylindrical rotating body 11a is formed of an iron alloy or pure iron, the anode target support shaft 9 is formed of a molybdenum (Mo) metal, and these are joined with an iron-chromium brazing material. Therefore, the molybdenum (Mo) eluted from the anode target support shaft 9 dissolves in the brazing filler metal 31, so that the strength of the joint portion formed by the brazing filler metal 31 can be further increased.

One embodiment described above is presented as an example and is not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and variations thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

1 ... rotating anode X-ray tube, 7 ... anode target, 9 ... anode target support shaft, 11 ... rotating body, 12 ... connecting part, 13 ... fixed body, 31 ... brazing material.

Claims (6)

An anode target that generates X-rays due to collision of electrons emitted from the cathode,
With the anode target support shaft to which the anode target is fixed,
A rotating body to which the anode target support shaft is connected and
A fixed body connected to the rotating body via a bearing is provided.
The connecting portion between the anode target support shaft and the rotating body is joined with a brazing material, and the brazing material is 27 to 50% by weight of iron, 20 to 30% by weight of chromium, 30 to 50% by weight of nickel, and phosphorus 5. A rotating anode type X-ray tube having a compounding ratio of about 10% by weight and a melting temperature of 1000 ° C to 1100 ° C. The rotating anode type X-ray tube according to claim 1, wherein the anode target support shaft is made of molybdenum or a molybdenum alloy, and the rotating body is made of iron or an iron alloy at the connecting portion with the anode target support shaft. The process of connecting the anode target support shaft to which the anode target is fixed and the rotating body connected to the fixed body via a bearing, and
A step of placing a brazing material on a connecting portion between the anode target support shaft and the rotating body, melting the brazing material in a furnace, and brazing the connecting portion is provided.
The brazing filler metal is a rotary anode type having a blending ratio of 27 to 50% by weight of iron, 20 to 30% by weight of chromium, 30 to 50% by weight of nickel and 5 to 10% by weight of phosphorus and a melting temperature of 1000 ° C to 1100 ° C. A method for manufacturing an X-ray tube. The production of the rotating anode type X-ray tube according to claim 3, wherein the anode target support shaft is made of molybdenum or a molybdenum alloy, and the rotating body is made of iron or an iron alloy at the connecting portion with the anode target support shaft. Method. The method for manufacturing a rotary anode type X-ray tube according to claim 3 or 4, wherein the atmosphere in the furnace for melting the brazing filler metal is a hydrogen atmosphere having a dew point of −37 ° C. or lower. The method for manufacturing a rotary anode type X-ray tube according to claim 3 or 4, wherein the atmosphere in the furnace for melting the brazing filler metal has a vacuum degree of 1 to 1 × 10 ^-3 (Pa).

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