JP2019139881A - Rotary anode x-ray tube and manufacturing method therefor - Google Patents

Abstract

To provide a rotary anode X-ray tube and a manufacturing method therefor.SOLUTION: A rotary anode X-ray tube comprises: a cathode; an anode target; an anode target support shaft to which the anode target is fixed; a rotary body to which the anode target support shaft is coupled; and a fixed body which is coupled to the rotary body via a bearing. A coupling part between the anode target support shaft and the rotary body is bonded by a brazing material. The brazing material has the following compounding ratio: 27 to 50 wt.% of iron; 20 to 30 wt.% of chromium; 30 to 50 wt.% of nickel; and 5 to 10 wt.% of phosphorus. The brazing material also has a melting temperature ranging from 1,000 to 1,100°C.SELECTED DRAWING: Figure 2

Description

  Embodiments described herein relate generally to a rotary anode X-ray tube and a method for manufacturing the same.

  In general, a rotary 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 a bearing. An electromagnetic coil is arranged outside the vacuum vessel, and by applying an electric current to the electromagnetic coil, an X-ray is emitted by applying the electron beam emitted from the cathode to the rotating anode target surface while rotating the rotating body at a 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 a nickel (Ni) alloy instead of a commonly used brazing material made of a copper (Cu) alloy. Is disclosed.

Japanese Patent Laid-Open No. 11-045675

  However, in a repetitive environment at a 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, there is a possibility that the toughness of the joint portion may be lowered. As a result, the deterioration of the joint portion proceeds, the rotation of the anode target becomes unbalanced, and abnormal vibration may occur.

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

  A rotary anode X-ray tube according to an embodiment includes an anode target that generates X-rays when electrons emitted from a cathode collide, an anode target support shaft to which the anode target is fixed, and the anode target support shaft. And a fixed body connected to the rotating body via a bearing, 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 to 1100 ° C.

  A method of manufacturing a rotary 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 rotary body connected to the fixed body via a bearing, and the anode target support Placing the brazing material on the connecting portion between the shaft and the rotating body, melting the brazing material in a furnace and brazing the connecting portion, the brazing material comprising 27 to 50% by weight of iron, chromium It is a blending ratio of 20 to 30% by weight, nickel 30 to 50% by weight and phosphorus 5 to 10% by weight, and a melting temperature of 1000 ° C to 1100 ° C.

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

  Hereinafter, a rotary anode X-ray tube and a manufacturing method thereof according to an embodiment will be described in detail with reference to the drawings. In addition, although the drawings may be schematically represented with respect to the width, thickness, shape, and the like of each part as compared with the actual mode for clarity of explanation, they are merely examples, and The interpretation is not limited. In addition, in the present specification and each drawing, components that perform the same or similar functions as those described above with reference to the previous drawings are denoted by the same reference numerals, and repeated detailed description may be omitted as appropriate. .

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

  The inside of the vacuum envelope 3 is kept in a vacuum.

  The cathode 5 is a member that emits electrons.

  The anode target 7 has a disk shape, and generates X-rays when electrons emitted from the cathode 5 collide with a surface 7 a facing the cathode 5. The anode target 7 is made of a heavy metal having a high melting point. 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 by a nut 17.

  A lower end portion 9 a of the anode target support shaft 9 is connected to the rotating body 11 by a 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 includes 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. Each of the outer cylindrical rotating body 11a and the inner cylindrical rotating body 11b has 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 disc-shaped flange 14 is fixed to the lower opening of the rotating body 11.

  In the outer cylindrical rotating body 11a, the outer peripheral surface portion 22 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 connection part 12 of the anode target support shaft 9 and the rotary body 11 is demonstrated. At the lower end portion 9 a of the anode target support shaft 9, a flange portion 19 and a male screw 21 are formed below the flange portion 19.

  On the other hand, a hole 25 is formed at the center of the bottom 23 of the outer cylindrical rotating body 11a. A concave step 27 and a female screw 29 are formed in the hole 25 below the step 27. In the connecting portion 12, a male screw 21 formed on the lower end portion 9a of the anode target support shaft 9 is connected to a female screw 29 formed on the bottom portion 23 of the outer cylindrical rotating body 11a by screwing. Furthermore, the flange portion 19 of the anode target support shaft 9 is disposed on the inner periphery of the step portion 27 in the bottom portion 23, and the gap between the inner peripheral surface of the step portion 27 and the outer peripheral surface of the flange portion 19 is melted. In the connecting portion 12 between the lower end portion 9a of the anode target support shaft 9 and the outer cylindrical rotating body 11a, the brazing material 31 is poured by screws 21 and 29 and joined by the brazing material 31. Yes. In this specification, the brazing material 31 indicates the brazing material after melting, but the brazing material before melting has the same composition and melting temperature.

  Note that the brazing material 31 melted at the step portion 27 also flows between the male screw 21 and the female screw 29 by capillary action, and the male screw 21 and the female screw 29 are also joined by the brazing material 31.

  In the component of the brazing filler metal 31, the weight ratio of iron, chromium, nickel and phosphorus is 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. This is because these weight ratios can provide balanced strength, toughness, and hardness, and the melting temperature can be easily set in the range of 1000 ° C to 1100 ° C.

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

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

  Further, in the case of a nickel brazing material containing nickel (Ni) as a main component, the hardness is high and brittle, so that the deterioration of the joint portion is likely to proceed by 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 material 31 according to the present embodiment, when the material of the anode target support shaft 9 that is brazed is Mo or Mo alloy, Mo is slightly diffused into the brazing and alloyed. As a result, the joint strength of the connecting portion 12 can be further increased.

  The brazing material 31 is more preferably a blending ratio of iron 27 to 30% by weight, chromium 20 to 22% by weight, nickel 42 to 46% by weight and phosphorus 7 to 10% by weight. If the blending ratio is within this range, the melting temperature is likely to be closer to 1000 ° C. to 1100 ° C., and the strength is further balanced as compared with conventional copper (C) brazing material and nickel (Ni) brazing material. It is because toughness and hardness can be provided.

  When the specific blending ratio is, for example, 30% by weight of iron, 20% by weight of chromium, 40% by weight of nickel, and 10% by weight of phosphorus, it can be melted at about 1050 ° C., which is close to copper brazing material and Ni brazing material.

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

  For joining the anode target 7 and the anode target support shaft 9, the anode target support shaft 9 is fitted into the center hole of the disc-shaped anode target 7 and fixed with a nut 17. On the other hand, the male target 21 is formed on the outer peripheral surface of the lower end portion 9a of the anode target support shaft 9.

  In the rotating body 11, in the cylindrical outer cylindrical rotating body 11 a, a female screw 29 is formed on the bottom 23 to which the male screw 21 of the anode target support shaft 9 is screwed. In addition, a concave 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.

  Thereafter, 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 rotator 11a to connect the anode target support shaft 9 and the outer cylindrical rotator 11a. The brazing material 31 is disposed around the stepped portion 27 in the portion 12 (not shown), and the brazing material 31 is melt-bonded in the furnace.

  When the furnace is a hydrogen atmosphere furnace, the atmosphere in the furnace when the brazing filler metal 31 is brazed is preferably a hydrogen atmosphere having a dew point of −37 ° C. or less. This is because the brazing material 31 is an iron material containing chromium, so that oxidation in a hydrogen heating environment is prevented. That is, in a hydrogen atmosphere having a dew point higher than −37 ° C., the brazed portion may be oxidized by moisture in the furnace. The reason why the dew point in the hydrogen atmosphere is regulated is to suppress oxidation due to moisture. Therefore, it is desirable that the dew point is as low as possible as long as it is −37 ° C. or lower.

On the other hand, when the furnace is a vacuum furnace, when the brazing environment of the brazing material 31 is vacuum heating, the degree of vacuum is 1 to 1 × 10 ⁻³ (Pa) from the vapor pressure of the molten brazing material. It is preferable that 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 will diffuse 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 11 b via a dynamic pressure slide bearing 19, and a vacuum envelope is provided. Install in 3. A cathode 5 is attached to the vacuum envelope 3. A stator coil 15 is provided outside the vacuum envelope 3 to assemble the rotary anode X-ray tube 1.

  In the rotating anode X-ray tube 1, the rotating body 11 is rotated by the electromagnetic force by energizing the stator coil 15, and electrons emitted from the cathode 5 are opposed to the rotating anode target 7. To generate X-rays, and the X-rays are emitted to the outside of the vacuum envelope 3.

  According to the present embodiment, at the connecting portion 12 between the anode target support shaft 9 and the rotator 4, the male screw 21 formed at the lower end portion 9a of the anode target support shaft 9 and the outer cylindrical rotator 11a screwed to the male screw 21 are provided. Since the flange portion 19 formed on 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 female screw 29 of the bottom portion 23 of the anode target support shaft 9 by brazing, The joining strength of the connecting portion 12 is high.

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

  The brazing material 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. The strength, toughness, and hardness can be provided, and the anode target 7 can continue to maintain stable rotation even when the rotary 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-based alloy or pure iron, the anode target support shaft 9 is formed of a molybdenum (Mo) -based metal, and these are joined by an iron-chromium brazing material. Therefore, molybdenum (Mo) eluted from the anode target support shaft 9 is dissolved in the brazing material 31, so that the strength of the joint portion by the brazing material 31 can be further increased.

  The above-described embodiment has been presented as an example, and is not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Rotary anode X-ray tube, 7 ... Anode target, 9 ... Anode target support shaft, 11 ... Rotating body, 12 ... Connection part, 13 ... Fixed body, 31 ... Brazing material.

Claims (6)

An anode target that generates X-rays by collision of electrons emitted from the cathode;
An anode target support shaft to which the anode target is fixed;
A rotating body connected to the anode target support shaft;
A fixed body connected to the rotating body via a bearing,
The connecting portion between the anode target support shaft and the rotating body is joined with a brazing material, and the brazing material is composed of 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 rotary anode X-ray tube having a blending ratio of 10 wt% and a melting temperature of 1000 ° C. to 1100 ° C.   2. The rotary anode X-ray tube according to claim 1, wherein the anode target support shaft is made of molybdenum or molybdenum alloy, and the rotating body is made of iron or an iron alloy at the connecting portion with the anode target support shaft. Connecting an anode target support shaft to which the anode target is fixed, and a rotating body connected to the fixed body via a bearing;
Placing a brazing material on the connecting portion between the anode target support shaft and the rotating body and melting the brazing material in a furnace to braze the connecting portion;
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 to 1100 ° C. X-ray tube manufacturing method.   The said anode target support shaft is a product made from molybdenum or molybdenum alloy, The said rotary body manufactures the rotating anode type | mold X-ray tube of Claim 3 whose said connection part with the said anode target support shaft is made from iron or an iron alloy. Method.   The method for producing a rotary anode X-ray tube according to claim 3 or 4, wherein the atmosphere in the furnace for melting the brazing material is a hydrogen atmosphere having a dew point of -37 ° C or lower. The method for producing 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 degree of vacuum of 1 to 1 x ^10-3 (Pa).

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