Fabrication process for single-crystallization anti-evaporation X-ray tube anode target

Abstract

A fabrication process for a single-crystallization anti-evaporation X-ray tube anode target (1), comprises the following steps: step 1, preparing a single-crystallization fabrication device and an ano

Description

SPECIFICATION FABRICATION PROCESS FOR SINGLE-CRYSTALLIZATION ANTI-EVAPORATION X-RAY TUBE ANODE TARGET TECHNICAL FIELD The disclosure relates to a fabrication process of an X-ray tube, in particular to a fabrication process of a single-crystallization anti-dissipation X-ray tube anode target. BACKGROUND X-ray tube (X-ray bulb tube), a vacuum diode working at high voltage, is the main component used to emit X-rays on CT machine. It contains two electrodes: a filament for emitting electrons as a cathode, and a target for receiving electron bombardment as an anode. Both electrodes are sealed within a high-vacuum glass or ceramic shell. In the prior art, the anode target of the X-ray tube includes a working surface subjected to electron bombardment, referred as an anode target surface, and the fabrication process of the anode target surface is implemented by powder metallurgy, high-purity tungsten powder and tungsten-rhenium alloy powder are processed by casting, sintering, forging and cutting, and the internal grains in the working zone are polycrystalline (with 10,000-20,000 grains or more per square millimeter). However, in the working process of an X-ray tube, there is a defect in the anode target of the X-ray tube. When ultra-high voltage current is applied to the anode target surface, a large number of fine particles of tungsten will be separated from the polycrystalline interface due to the fact that the polycrystalline grains are impacted by anode ultra-high voltage electrons, which will pollute a tube wall and X-ray window of the X-ray tube and produce electronic interference caused by the tungsten particles to the X-ray, resulting in poor X-ray definition, directly affecting the quality of images and increasing the difficulty of lesion diagnosis. With the continuous dissipation of the anode target at each operation, the life of X-ray tube will be terminated due to the decline of image quality. SUMMARY In order to overcome the shortcomings of the prior art, the disclosure provides a fabrication process of a single-crystallization anti-evaporation X-ray tube anode target. The technical schemes adopted by the disclosure to solve the technical problems are as follows: A fabrication process of single-crystallization anti-dissipation X-ray tube anode target is characterized by comprising the following steps: Step 1: preparing a single-crystallization fabrication device and an anode target, wherein the anode target is provided with an anode target surface annularly arranged along a circumferential direction thereof, and the single-crystallization fabrication device is provided with a working cavity for performing single-crystallization to the anode target surface; Step 2: fixedly placing the anode target in the working cavity, and starting up the single-crystallization fabrication device to melt the anode target surface at a melting temperature of 3360-4000 degrees Celsius; Step 3: cooling and condensing the molten anode target surface, so that the anode target surface is in a single crystal state, a glass crystal or a local quasi-monocrystalline state. In the disclosure, in the step 2, before the single-crystallization fabrication device is started, a first gas supply device is used to introduce inert gas into the working cavity. In the present disclosure, in the step 2, after the anode target surface is melted, the melting depth of the anode target surface is between 0.02 and 5 mm. In the present disclosure, in the step 3, the molten anode target surface is cooled and condensed at a rate of 1000 degrees Celsius or more per second. In the disclosure, the anode target comprises a tungsten alloy layer, a metal molybdenum layer and a graphite layer arranged in sequence from top to bottom, and the anode target surface is arranged on the tungsten alloy layer. In the disclosure, the single-crystallization device comprises a rotating device which drives the anode target to rotate, and an irradiation generator which is used for irradiating and melting the anode target surface. The working cavity is arranged on the rotating device, a rotating end of the rotating device is provided with a fixture placed in the working cavity. The irradiation generator has an irradiation output end for irradiating and melting the anode target surface, which extends into the working cavity and is placed above the fixture. The anode target is fixed on the fixture and the anode target surface corresponds to the irradiation output end. In the disclosure, the irradiation generator also has an adjusting mechanism for driving the irradiation output end to move up and down, and the distance between the irradiation output end and the anode target surface can be adjusted by moving the irradiation output end up and down. In the disclosure, the rotating device comprises a frame and a rotating motor arranged on the frame, the rotating end of the rotating motor extends out of the top of the frame and is connected with the fixture, a protective cover is provided at the top of the frame, and an inner cavity of the protective cover and the frame together define the working cavity. In the disclosure, the protective cover is made of transparent material. The disclosure has the following beneficial effects: 1. The definition of X-ray emitted by X-ray tube is greatly improved because the anode target surface is changed from a polycrystalline state to a single-crystallization state; 2. An electron layer including an integrated grain formed by tens of thousands of micro-grains is in an active state, which enhances the intensity of X-ray; 3. The service life of the anode target after single-crystallization process is prolonged by 3-5 times or more; 4. The anode target surface has anti-dissipation performance after single-crystallization process, as particles of tungsten will not be separated when the anode target surface in is operation, which effectively avoids the electronic interference of X-rays caused by the tungsten particles, so that a variety of critical lesions can be correctly judged and diagnosed at an early stage, greatly reducing the burden on medical resources, human suffering and high treatment and maintenance costs, and greatly reducing the loss of social resources caused by misdiagnosis of various personnel, which not only has economic benefits, but also has great social benefits. To sum up, the disclosure changes the anode target surface from a polycrystalline state to a single-crystallization state, so that the definition and intensity of X-rays emitted by the X-ray tube are greatly improved, and the service life of the X-ray tube is effectively prolonged. Moreover, the single-crystallization anode target surface has anti-dissipation performance, so that the accuracy of X-rays is effectively improved, and the accuracy of detection results of a CT machine is ensured. The process is suitable for being promoted for broad applications. BRIEF DESCRIPTION OF THE DRAWINGS The disclosure will be further explained with the attached drawings and embodiments: FIG. 1 is a schematic diagram of the working state of an embodiment; FIG. 2 is a schematic structural diagram of an anode target. DETAILED DESCRIPTION In order to make the purpose, technical scheme and advantages of the embodiments of the disclosure more clear, the technical schemes in the embodiments of the disclosure will be described clearly and completely with the attached drawings. Referring to FIGs. 1-2, a fabrication process of a single-crystallization anti-dissipation X-ray tube anode target includes the following steps: step 1: preparing a single-crystallization fabrication device and an anode target 1, wherein the anode target 1 is provided with an anode target surface 11 annularly arranged along a circumferential direction thereof, and the anode target surface 11 has a width of 10-12 mm; the single-crystallization fabrication device is provided with a working cavity 2 for performing single-crystallization to the anode target surface 11; in addition, the anode target 1 is provided with a central hole 15 at its middle part, which is used for connecting with other parts of the X-ray tube; the anode target 1 comprises a tungsten alloy layer 12, a metal molybdenum layer 13 and a graphite layer 14 arranged in sequence from top to bottom, and the anode target surface 11 is arranged on the tungsten alloy layer 12 made of high-purity tungsten powder or tungsten-thenium alloy powder; step 2: fixedly placing the anode target 1 in the working cavity 2, and inert gas is introduced into the working cavity 2 by a first gas supply device to avoid oxidation of the anode target 1 in the process of single-crystallization; starting up the single-crystallization fabrication device to melt the anode target surface 11 at a melting temperature of 3360-4000 degrees Celsius; in this embodiment, the preferred range of the melting temperature is 3400-3800 degrees Celsius to improve the melting stability, and the most preferred melting temperature is 3500 degrees Celsius; after the anode target surface 11 is melted, the anode target surface 11 has a melting depth of 0.02-5Smm, so as to ensure the single-crystallization; when the melting depth of the anode target surface 11 is 0.2mm, the single-crystallization performance is the best; step 3: cooling and condensing the molten anode target surface 11 at a rate of 1,000 degrees Celsius or more per second, such that 10,000 to 20,000 or more grains per square millimeter are merged into one grain, thereby the anode target surface 11 is in a single crystal state, a glass crystal or a local quasi-monocrystalline state. Therefore, when the anode target 1 is impacted by cathode ultra-high voltage electrons during operation, particles of tungsten will not be separated when X-rays are emitted, and the following effects are achieved: 1. the definition of X-ray emitted by X-ray tube is greatly improved because the anode target surface is changed from a polycrystalline state to a single-crystallization state; 2. an electron layer including an integrated grain formed by tens of thousands of micro-grains is in an active state, which enhances the intensity of X-ray; 3. the service life of the anode target 1 after single-crystallization process is prolonged by 3-5 times or more; 4. the anode target surface has anti-dissipation performance after single-crystallization process, as particles of tungsten will not be separated when the anode target surface is in operation, which effectively avoids the electronic interference of X-rays caused by tungsten particles, so that a variety of critical lesions are correctly judged and diagnosed at an early stage, greatly reducing the burden on medical resources, human suffering and high treatment and maintenance costs, and greatly reducing the loss of social resources caused by misdiagnosis of various personnel, which not only has economic benefits, but also has great social benefits. Preferably, the single-crystallization device comprises a rotating device 3 for driving the anode target 1 to rotate, and an irradiation generator 4 for irradiating and melting the anode target surface 11. The working cavity 2 is arranged on the rotating device 3, and a fixture is provided at a rotating end of the rotating device 3 and disposed in the working cavity 2. The irradiation generator 4 has an irradiation output end 41 for irradiating and melting the anode target surface 11, which extends into the working cavity 2 and is placed above the fixture. The anode target 1 is fixed on the fixture and the anode target surface 11 corresponds to the irradiation output end 41. In addition, the irradiation generator 4 also has an adjusting mechanism for driving the irradiation output end 41 to move up and down. The distance between the irradiation output end 41 and the anode target surface 11 can be adjusted by moving the irradiation output end 41 up and down, so as to keep the distance between the irradiation output end 41 and the anode target surface 11 at 202 mm, and most preferably at 20mm, thus ensuring reliability of melting the anode target surface 11. In the above structure, the irradiation generator 4 is any one of a plasma generator, a laser generator, an electron beam irradiation device, a rhenium heater, an intermediate frequency heating device, a high frequency heating device, and an ultra-audio heating device. Table 1 below shows the power parameters of various heating devices. Table 1: device name power range Plasma generator 30~200KW Laser generator <30KW electron beam irradiation device 10~180KW rhenium heater 10~200KW intermediate frequency heating device | 15~600KW high frequency heating device 3~500KW ultra-audio heating device 100~300KW In this embodiment, the irradiation generator 4 is a plasma generator, which generates high temperature on the anode target surface 11 through its output end, thereby melting the anode target surface 11, and the output end of the plasma generator is the irradiation output end 41. In addition, during irradiation heating, the power and spot size range of the irradiation generator 4 can be adjusted according to the size and cooling rate of the target. Preferably, the rotating device 3 comprises a frame 31 and a rotating motor 32 arranged on the frame 31. A rotating end of the rotating motor 32 extends out of the top of the frame 31 and is connected with the fixture, which can be a screw. The rotating end of the rotating motor 32 is provided with a screw hole at its top, and a threaded end of a screw passes through the central hole 15 and is screwed with the screw hole to fix the anode target 1 to the rotating end of the rotating motor 32. Obviously, without limitation to the above structure, a fixation structure added to the rotating end of the rotating motor 32 and configured for achieving the same purpose is possible. Further, the frame 31 is covered with a protective cover 33 at its top, and the inner cavity of the protective cover 33 and the frame 31 together define the working cavity 2, and the protective cover 33, at its top, is provided with an inlet for insertion of the irradiation output end 41 into the working cavity 2. Preferably, the protective cover 33 is made of transparent material, so that the processing status of the anode target 1 inside the protective cover 33 can be seen during processing, which is convenient for workers to operate and process. In this embodiment, the protective cover 33 is a tank-shaped container, and the protective cover 33 is made of sapphire glass, which has the advantages of wear resistance, high temperature resistance, high hardness and the like, thus ensuring that the protective cover 33 will not be damaged due to high temperature when the single-crystallization device melts the anode target surface 11. In addition, the diameter of the protective cover 33 is 30% greater than the diameter of the anode target 1, so as to ensure the stable implementation of the irradiation melting operation without affecting the protective cover 33. In the above step 2, the first gas supply device is a device that can supply inert gas, and the purpose is achieved as long as it can supply inert gas. In addition, in the step 3, a second gas supply device can be used to introduce cooling gas into the working cavity 2, and the cooling gas is liquid nitrogen. The first gas supply device and the second gas supply device are both belong to the prior art, referring to the existing devices for gas supply, the first gas supply device and the second gas supply device are not shown. When the first gas supply device and the second gas supply device supply gas into the working cavity 2, the protective cover 33 can be provided with a first gas inlet for introducing inert gas and a second gas inlet for introducing cooling gas, and the first gas inlet and the second gas inlet are respectively provided with connectors for connecting the first gas supply device and the second gas supply device. Obviously, the inert gas and the cooling gas can also be directly supplied into the working cavity 2 from the inlets through manual operation. The described above is only the preferred embodiments of the present disclosure, and all technical solutions that achieve the purpose of the present disclosure by basically the same schemes are within the protection scope of the present disclosure.

Claims

CLAIMS 1. A fabrication process of a single-crystallization anti-evaporation X-ray tube anode target, characterized in that, it comprises the following steps: step 1: preparing a single-crystallization fabrication device and an anode target (1), wherein the anode target (1) is provided with an anode target surface (11) annularly arranged along a circumferential direction thereof, and the single-crystallization fabrication device is provided with a working cavity (2) for performing single-crystallization to the anode target surface (11); step 2: fixedly placing the anode target (1) in the working cavity (2), starting up the single-crystallization fabrication device to melt the anode target surface (11) at a melting temperature of 3360-4000 degrees Celsius; and step 3: cooling and condensing the molten anode target surface (11), so that the anode target surface (11) is in a single crystal state, a glass crystal or a local quasi-monocrystalline state.

2. The fabrication process of a single-crystallization anti-evaporation X-ray tube anode target according to claim 1, characterized in that, in the step 2, before the single-crystallization fabrication device is started, a first gas supply device is used to introduce inert gas into the working cavity (2).

3. The fabrication process of a single-crystallization anti-evaporation X-ray tube anode target according to claim 1, characterized in that, in the step 2, after melting the anode target surface (11), the anode target surface (11) has a melting depth of 0.02-5 mm.

4. The fabrication process of a single-crystallization anti-evaporation X-ray tube anode target according to claim 1, characterized in that, in the step 3, the molten anode target surface (11) is cooled and condensed at a rate of 1000 degrees Celsius or more per second. S. The fabrication process of a single-crystallization anti-evaporation X-ray tube anode target according to claim 1, characterized in that, the anode target (1) comprises a tungsten alloy layer (12), a metal molybdenum layer (13) and a graphite layer (14) arranged in sequence from top to bottom, and the anode target surface (11) is arranged on the tungsten alloy layer (12).

6. The fabrication process of a single-crystallization anti-evaporation X-ray tube CLAIMS anode target according to claim 1, characterized in that, the single-crystallization device comprises a rotating device (3) for driving the anode target (1) to rotate, and an irradiation generator (4) for irradiating and melting the anode target surface (11); the working cavity (2) is arranged on the rotating device (3), and a rotating end of the rotating device (3) is provided with a fixture placed in the working cavity (2); the irradiation generator (4) is provided with an irradiation output end (41) for irradiating and melting the anode target surface (11), which extends into the working cavity (2) and is placed above the fixture, and the anode target (1) is fixed on the fixture and the anode target surface (11) corresponds to the irradiation output end (41).

7. The fabrication process of a single-crystallization anti-evaporation X-ray tube anode target according to claim 6, characterized in that, the irradiation generator (4) further includes an adjusting mechanism for driving the irradiation output end (41) to move up and down, and the distance between the irradiation output end (41) and the anode target surface (11) can be adjusted by moving the irradiation output end (41) up and down.

8. The fabrication process of a single-crystallization anti-evaporation X-ray tube anode target according to claim 7, characterized in that, the rotating device (3) comprises a frame (31) and a rotating motor (32) arranged on the frame (31), a rotating end of the rotating motor (32) extends out of the top of the frame (31) and is connected with the fixture, the frame (31) is covered with a protective cover (33) at its top, and an inner cavity of the protective cover (33) and the frame (31) together define the working cavity (2).

9. The fabrication process of a single-crystallization anti-evaporation X-ray tube anode target according to claim 8, characterized in that, the protective cover (33) is made of transparent material.

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