JPH0673265B2 - X-ray target manufacturing method - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a method of manufacturing an X-ray target for a rotary anode X-ray tube.

[Prior art]

The X-ray target of a rotary anode type X-ray tube is normally designed by "skimming" a threaded stem protruding from the flange mounting part of the support shaft into the center hole of the target disk and tightening a nut on this stem to tighten the target disk. Is clamped to the above-mentioned flange mounting portion, and thereby the target disk is fixed to the support shaft to be manufactured. The X-ray target thus assembled is subjected to dynamic balance adjustment and then sealed in a glass envelope.

[Problems to be Solved by the Invention]

However, an inconvenience may occur in the X-ray target having such an assembly. That is, the X-ray target is 12 times in 10 seconds when the rotary anode X-ray tube is actually used.
May be heated to 00 ° C, and 10,000 rp within 2 seconds
Can be rotated up to m. Due to these thermal stress and mechanical stress, the disk may be eccentric, the dynamic balance may be lost, vibration and noise may be increased, and the bearing life may be shortened. In rare cases, the vibration may be large enough to cause tube breakage. Further, the heat radiation of the target disk having a high temperature as described above is performed by both radiation and conduction, but the heat conduction is conducted from the disk through the support shaft to the rotor. However, not only the thermal resistance is large due to the surface contact between the target disk and the support shaft, but also the value thereof may vary due to the thermal stress and the mechanical stress described above and become larger. In such a case, the temperature of the entire target and the temperature of the focus trajectory exceed the designed values, and as a result, the performance deteriorates at an accelerated rate. Therefore, as disclosed in, for example, Japanese Patent Application No. 62-168317, it is considered to devise a method of fixing the target disk and the support shaft. However, the method disclosed in this publication is also effective in that it uses a brazing material, but basically, the diameter of the center hole of the disk is made larger than the diameter of the tip of the supporting shaft fitted therein. Since the tip of the support shaft is put into the center hole and then tightened with a nut, the center shafts of both must be aligned before tightening with the nut, and this centering work is difficult. It is doubtful whether it is practically effective. The present invention prevents the X-ray target member from being eccentric or the thermal resistance between the target member and the supporting member does not fluctuate, and can be easily used practically by a simple operation. It is intended to provide a manufacturing method.

[Means for Solving the Problems]

In order to achieve the above object, the method of manufacturing an X-ray target according to the present invention comprises a first step of fitting the tip of a supporting member made of a refractory metal into a central hole of a target member made of a refractory metal by a "shrink fit". The second step of heating the thus assembled and assembled parts under a condition in which the temperature is lower or the time is shorter than the lower annealing condition of the both members, and then the above-mentioned fitting is performed. It is characterized by a third step of heating the assembly thus assembled under the condition that the temperature is higher or the time is longer than the lower one of the annealing conditions of the both members.

[Action]

In the first step, when the tip end of the support member is fitted into the center hole of the target member by "shrink fit", a large surface pressure is generated at the fitting interface. In the next second step, the thus-assembled product is heated under the condition that the temperature is lower or the time is shorter than the lower annealing condition of these two members. At this time, due to the above surface pressure, diffusion bonding occurs at the fitting interface. At this time, an annealing effect may occur, but since the heating is performed under a condition lower than the annealing condition as described above, the annealing effect is only slight. Further, in the third step, the heating is performed under the condition that the temperature is higher or the time is longer than the lower annealing condition of these both members. As described above, since heating is performed in the third step under a condition higher than the annealing condition, a sufficient annealing effect is generated in this step, and residual stress remaining after the second step is removed. .

【Example】

Next, an embodiment of the present invention will be described with reference to the drawings. In FIG. 1A, the X-ray target member 1
Is a disc-shaped base member 11 (for example, outer diameter 100 mm, thickness 8.8 mm) made of a heat-resistant TZM (titanium-zirconium-molybdenum) alloy with a focal track member 12 clad. That is, the focal track member 12 is made of, for example, a tungsten alloy containing 5% rhenium and having a thickness of 1 mm, and is clad at an inclined portion of about 12 ° provided near the outer periphery of the base member 11. At the center of the target member 1, a support member 2 to be described later is fitted, and an eye hole 13 is formed.
(For example, diameter ▲ 12 ^+0.018 ₀ ▼ mm) is provided. The support member 2 is made of a non-recrystallized product of TZM alloy and is formed so as to project from the rotor portion 3.
It is composed of 22 and pillars 23. The diameter of the blind eye shaft 21 is made larger than the diameter of the aforementioned blind eye hole 13 (for example, diameter ▲
12 ^0.071 _0.060 ▼ mm), and the side surface is cross-knurled with a depth of 0.02 to 0.03 mm. This hameai axis
The base portion 21 is provided with a seat portion 22 for positioning the target member 1. The column part 23 is a size for limiting the heat conduction from the target member 1 to the rotor part 3 and maintaining axial strength (for example, outer diameter 11.5 mm, inner diameter 9 mm, length 19 mm).
It is said that The X-ray target member 1 and the supporting member 2 are placed in a vacuum chamber (not shown) as shown in FIG. 1A.
The target assembly is placed in the same direction as the finished product, with their axes aligned. Then, the ring-shaped electron gun 4 for heating is arranged facing the target member 1 at a distance of about 5 mm. A heat insulating plate 5 is set between the target member 1 and the support member 2. This heat shield 5
Is formed of, for example, a molybdenum material into a disc shape, and has an opening at the center thereof through which the seat portion 22 of the support member 2 can pass. Further, the outer periphery of the central opening portion can be removed so that it can be removed after the target assembly is completed. An opening having a width larger than the diameter of the pillar portion 23 is provided. Although not shown in the figure, in order to measure the temperature of the target member 1 and adjust it, a two-color thermometer is arranged so that the target member 1 is in focus. The output of the ring-shaped electron gun 4 is controlled by the output. When the degree of vacuum in the chamber reaches a predetermined value, an electron beam is generated from the ring-shaped electron gun 4 and collided with the target member 1 to heat the target member 1. For example, when the electron beam output is DC 10 KV-400 mA, the temperature of the target member 1 reaches 1350 ° C. in about 100 seconds, so this temperature is held for 90 seconds (first step in FIG. 2). Then, the diameter of the blind hole 13 of the target member 1 expands by 0.1 mm. On the other hand, the temperature of the supporting member 2 is kept at 80 ° C. or lower due to the effect of the heat insulating plate 5, and the diameter of the blind eye shaft 21 is not expanded. Therefore, the support member 2 is rapidly moved toward the target member 1 side by a hydraulic cylinder (not shown) or the like, and the fit shaft 21 of the support member 2 is inserted into the fit hole 13 of the target member 1. When the seat portion 22 of the support member 2 hits the target member 1, the movement of the support member 2 is stopped. This state is as shown in FIG. 1B. In this way, the hameai axis 21 of the support member 2 becomes the target member 1
When it is inserted into the eyelet hole 13, the heat exchanger makes the eyelet axis 21 almost equal to the temperature of the 6 target member 1 in about 6 seconds. The temperature is 1250 ° C due to the heat absorption of the supporting member 2.
It will be about. Then, since the hameai shaft 21 thermally expands and its diameter increases, a large surface pressure is generated at the fitting interface with the hameai hole 13 (see FIG. 4d). Then, as shown in FIG. 2, the second step is carried out by holding this 1250 ° C. for about 150 seconds. During the second step, diffusion bonding occurs due to the above-mentioned surface pressure at the contact interface 19 (see FIG. 1C) between the eyelet hole 13 of the target member 1 and the eyelet shaft 21 of the support member 2. Also, as shown in Fig. 1C,
21 is provided with a concave portion 24 by knurling, and in this example, since the support shaft 2 has higher strength at high temperature than the target member 1, the target member 1 side is plastically deformed and the concave portion 24 has a depth of 10 to 10 mm. Engagement of about 20 μm occurs. The surface pressure generated in the first step is reduced due to this plastic deformation and a slight annealing effect at 1250 ° C. The diffusion bonding of both members that has occurred up to the second step is not so perfect that both members are completely integrated, and the strength of the bonding portion is lower than that of the base material. Therefore, in this embodiment, the hameai shaft 21 is knurled so that the recess 24 is bitten from the target member 1 side to improve the strength of the contact interface in the shearing direction. Here, in this second step, the heating condition is set to 1250 ° C-150.
The reason for setting to seconds is as follows. Generally, diffusion bonding is more likely to occur at higher temperatures and higher surface pressures. On the other hand, the relationship between the temperature and the time of the stress relief condition of the TZM alloy is as shown in FIG. 3, and the time may be inverse exponentially shorter as the temperature becomes higher. The annealing conditions generally used in industry are 1100 ° C.-6 hours and 1200 ° C.-20 minutes. Furthermore, at high temperatures, 1250 ° C-5 minutes, 1300 ° C-70 seconds, etc. are also used.
The surface pressure of “similar fit” depends only on self-generation, and when the stress is completely released by annealing, the surface pressure disappears and diffusion bonding stops. Therefore, in this embodiment, 50% of the annealing condition of 1250 ° C. for 5 minutes is used.
That was the time. That is, since the target member 1 and the supporting member 2 are diffusion-bonded in the second step, even if some annealing is caused by heating, the annealing effect is mainly reduced as much as possible. The conditions under which diffusion bonding is effectively generated should be selected. From this viewpoint, heating conditions lower than the annealing conditions are selected. The condition may be 1200 ° C. for 10 minutes, but it seems that the temperature of the rotor part 3 becomes too high when the heating in the next step is included, which is not preferable. As described above, the surface pressure generated in the first step is reduced by the plastic deformation and the slight annealing in the second step, but a large circumferential tensile stress remains in the target member 1. Therefore, as it is, tensile stress in the circumferential direction due to thermal stress generated when the X-ray tube is loaded may be superimposed to cause stress cracking from the outer periphery to the blind hole 13.
Therefore, in order to remove the residual stress, heating in the third step is performed under the annealing condition or higher. The conditions were 1300 ° C. and 70 seconds or more in this example. This third step also serves as a degassing step as a target assembly, which is industrially advantageous. However, the rotor part 3
The time is restricted due to the restriction conditions such as the temperature. In this way, the target assembly in which the target member 1 and the support member 2 are fixed to each other is taken out from the vacuum chamber after cooling. The circumferential stress of the target member 1 at this time is shown in FIG.
, All indicate compressive stress. This is because the target member 1 is a TZM alloy base member 11 and a 5% rhenium-containing tungsten alloy focal track member 12 clad, and it is considered that the stress is caused by the difference in expansion coefficient between these materials. . This is because the stress in the circumferential direction of the target member 1 that has been degassed and heated is as shown in FIG. 4a, and shows an approximate distribution in the outer peripheral portion. In FIG. 4, a, b, c, and d are the target member 1 alone, the target member 1 plastically and diffusion-bonded to the support member 2, and the target member 1 plastically and diffusion-bonded, respectively.
Target member 1 at room temperature for the target member 1 at the time of exhaust completion by incorporating into a X-ray tube, and the result when the shrinkage fitting stress is calculated using the target member 1 as a single material
2 represents the stress distribution in the circumferential direction of. In order to test the eye-eye strength of the target member 1 fixed to the supporting member 2 in this manner, when the target member 1 was supported and the tip of the supporting member 2 was pushed out and pulled out, the required load was about 5 tons. The area around the hole 13 was peeled off. In a rotary anode X-ray tube incorporating such a target assembly, the target member 1 is eccentric due to thermal stress or mechanical stress as in the prior art, or the eyelet hole 13 of the target member 1 and the eyelet shaft 21 of the support member 2 are used. The conventional drawbacks are eliminated without the thermal resistance between and fluctuating. Further, in the manufacturing process, there is no difficult work such as centering work, which is easy. As described above, the present invention is applied to a general rotary anode type X-ray tube.
Although two embodiments have been described, the rotary anode type X-ray tube is designed and manufactured according to various uses, and the embodiments described above are adapted to these without departing from the spirit of the present invention. Can be transformed. By the way, from the viewpoint of the stress at the interface between the hameai hole 13 of the target member 1 and the hameai axis 21 of the support member 2, the stress can be classified into thermal stress and mechanical stress as described above, and the thermal stress is generally the base member of the target member 1. It is proportional to the average temperature rise of 11, that is, to the value obtained by dividing the X-ray tube input by the heat capacity of the target, the mechanical stress is generally proportional to the starting torque, and the moment of inertia (target weight x target diameter squared). ) Is divided by the startup time. Therefore, in the case of a model having a small interfacial stress, the formation of the recess 24 in the interlocking shaft 21 may be omitted, and the fitting may be performed by press-fitting with a smaller "shrink fit" margin than the shrink fitting. On the other hand, in the case of a model having a considerably large interfacial stress, the element which easily diffuses is contained in one or both of the eyelet hole 13 of the target member 1 and the eyelet shaft 21 of the supporting member 2 in order to further increase the diffusion bonding strength. It is desirable that a metal film is formed in advance and diffused in both base materials in the above second step. This metal film may be an alloy as long as it has a melting point lower than that of both base materials and easily diffuses into molybdenum, and at this time, does not contain an element that forms a brittle alloy with molybdenum.
Specifically preferred elements are Pd, Pt, Co, Zr, Ti and the like. In the case of a more special application, the temperature of the base member 11 of the target member 1 may remain high for a long time. In such a case, the heat of the target member 1 is transmitted to the bearing from the interference interface through the support column 23 of the support member 2, the rotor unit 3 and the bearing shaft, and the temperature limit of the bearing (depending on the material of the bearing and the material of the lubricating oil). Different). In order to deal with this, in the fixing method of the present invention, since the thermal resistance of the interface between the target member 1 and the supporting member 2 is small as described above, it is necessary to appropriately set the apparent contact area of both members. However, since there is a limit in securing the joint strength, it is desirable to increase the thermal resistance of the column portion 23. Therefore, the heat conduction formula, Q = (λ / σ) (θ1−θ2) A Q; heat quantity [W] λ; thermal conductivity [W / (m · ° C.)] (θ1−θ2); temperature difference [ ° C] σ; Length [m] A; Cross-sectional area [m ² ] of geometrical dimensions (A / σ)
The value obtained by dividing the cross-sectional area of 23 by the length of the column 23 is reduced.
In the experimental data, it is preferable that the dimensional relationship of the pillar portion 23 is such that (A / σ) is 4 × 10 ⁻³ m or less. The lower limit is determined by the mechanical strength of the column portion 23. In the case of the above embodiment (A /
σ) is 2.12 × 10 ^-3 m. Although it is a special application, a large load is added in a short time,
The average temperature rise rate of the base member 11 of the target member 1 may become extremely large. In this case, since the heat generation due to the load occurs in the focal track member 12 near the outer periphery of the target member 1, there is a delay in heat conduction to the center eye portion, and in the fixing method described above, the target member 1 and the support member 2 Due to the low thermal resistance of the blind eye portion between and, the temperature difference between the two becomes small. However, if the thermal resistance of the column portion 23 is too small, tensile stress is generated in the blind eye portion due to the difference in thermal expansion due to the temperature difference between the two, and this cannot be ignored. In such a case, it is necessary to increase the contact area of the fit-eye portion to reduce the heat resistance of the fit-eye portion, and to increase the heat resistance of the support portion 23 to reduce the temperature difference of the fit-eye portion. Experimentally, there is a dimensional relationship such that the apparent contact area A'of the eye-eye part is divided by the above (A / σ) and the value of (A '· σ / A) becomes 2 × 10 ^-4 m or more. desirable.
In the above embodiment, the value of (A ′ · σ / A) is 1.88 ×
It is 10 ^-3 m. Further, in the above-described embodiment, the blind eye hole 13 is a round hole and the blind eye shaft 21 is a cylinder, but the present invention is not limited to this, and combinations of all shapes that can be “similarly fitted” such as circles, corners and cones can be adopted. Further, in the above, the concave 24 by cross knurling is provided on the hameai shaft 21, but such irregularities may not be provided, and if provided, a bite that resists slippage in the shear direction of the bonding interface is formed. Any shape may be used. In the above-mentioned embodiment, the fitting in the first step is a shrink fitting, and the temperature in each step is different, but this is the second and the third.
This is because the annealing condition is set to be equal to or less than the annealing condition in the step of. By the way, the annealing conditions for stress relief can be various combinations of annealing temperature and time as shown in FIG. Therefore, it is possible to make the first step for fitting and the second step for plastic deformation / diffusion joining at the same temperature by selecting the "shrinkage" margin. Further, the temperature of the third step for annealing can be set to be the same as the temperature of the second step. For example, if the temperature is kept at 1200 ° C. for 20 minutes or more, the second and third steps are completed. Further, in the above, the first, second, and third steps are performed by heating continuously, but it is also possible to cool and reheat in the middle of the process because of the manufacturing process. In particular, the second and third steps may be combined with high frequency heating and electron impact heating in the exhaust step after sealing the envelope. However, the above embodiment is preferable because it can also serve as degassing of the target assembly. Although it has been described above that only in the first step, the “shrink fit” stress may remain and the target member 1 may crack.
Although very rare, the same may occur in the following cases. In general, the strength of the target largely depends on the material and structure of the target and also varies depending on variations in manufacturing. For such a reason, the strength of the target is abnormally low. If abnormal temporary thermal stress is applied, such as when an instantaneous large load is applied due to a failure or when the target is rapidly heated by an abnormal arc-shaped discharge in the X-ray tube, as shown in Fig. 4c. This is added to the internal stress of the target material 1, and a single crack is generated in the target member 1 from its outer periphery to the blind eye hole 13. Diffusion bonding strength cannot withstand such extreme stress, and the expansion rate of the hole 13 diameter due to cracking is empirically 0.5-
It becomes about 1% and exceeds the amount of plastic deformation, and the biting effect is canceled. As a result, the target member 1 falls off the support member 2, and in some cases, the envelope is broken. Therefore, in preparation for such a trouble,
It is also effective to take the structure shown in FIGS. 5, 6 and 7 below. In FIG. 5, the tip portion of the eyelet hole 13 of the target member 1 is chamfered to form the inclined surface 14. Caulking 25 is performed to widen the diameter of the tip of the saddle eye shaft 21 up to the inclined surface 14. The slope 14
The maximum diameter of is about 110% of the diameter of the eye hole 13, the angle is 30 °
The degree. In FIG. 6, a male screw is provided on the outer peripheral surface of the end of the hameai shaft 21 to engage the nut 15, and in FIG. 7, a female screw is provided on the inner peripheral surface of the end of the hameai shaft 21 to engage the bolt 16. By these, the movement of the target member 1 in the axial direction is prevented. These are heat-resistant nuts
Caulking is superior because it is expensive because it requires 15 or 16 bolts.

【The invention's effect】

According to the method of manufacturing an X-ray target of the present invention, the target member can be prevented from being eccentric due to the thermal stress or the mechanical stress between the target member and the supporting member, and the thermal resistance between the both members can be the thermal stress or the mechanical stress. It can be prevented from changing due to stress. Therefore, vibration and noise can be suppressed, the bearing life can be lengthened, and the risk of breaking the tube can be eliminated. Moreover, difficult work is unnecessary in the assembly process, and automation is easy.

[Brief description of drawings]

1A, 1B, 1C show an embodiment of the present invention.
FIG. A is a sectional view before fitting, FIG. 1B is a sectional view after fitting, FIG. 1C is an enlarged sectional view of a portion C of FIG. 1B, and FIG. 2 is a heating temperature time in each step. Fig. 3 is a graph showing the relationship between annealing temperature and time in stress relief of TZM alloy, Fig. 4 is a graph showing the stress distribution in the circumferential direction of the target, Figs. 5, 6 and FIG. 7 is a sectional view showing a modified example. 1 …… X-ray target member, 11 …… Base member, 12 ……
Focal point track member, 13 ... Hame eye hole, 2 ... Support member, 21
...... Hameai axis, 22 ...... seat part, 23 ...... post part, 24 ...... recessed part, 3 ...... rotor part.

Claims (1)

[Claims] 1. A tip of a support member made of a heat-resistant metal is "similarly fitted" into a center hole of a target member made of a heat-resistant metal.
And the second step of heating the assembled and assembled product under the condition that the temperature is lower or the time is shorter than the lower annealing condition of the two members. And the third step of heating the assembled and assembled product under the condition that the temperature is higher or the time is longer than the lower one of the annealing conditions of the both members. X-ray target manufacturing method.