Surface treatment method, stainless steel parts, X-ray tube, X-ray tube apparatus, method for manufacturing stainless steel parts, and method for manufacturing X-ray tubes

Abstract

The present invention provides a surface treatment method for obtaining a film with high emissivity that can be used in a vacuum, is low-cost, and has a low environmental impact, as well as stainless steel parts, X-ray tubes, X-ray tube apparatus, a method for manufacturing stainless steel parts, and a method for manufacturing X-ray tubes. [Solution] The surface treatment method according to the present disclosure includes a sandblasting step of applying a sandblasting treatment to the surface of stainless steel, and a greening step of applying a greening treatment to the surface after the sandblasting step, wherein the surface roughness Ra of the surface after the greening step is 0.70 μm or more and 1.00 μm or less, and the stainless steel part according to the present disclosure is a stainless steel part that has been subjected to a greening treatment on the surface after sandblasting, wherein the surface roughness Ra of the surface after the greening treatment is 0.70 μm or more and 1.00 μm or less.

Description

[Technical Field]

[0001] The present disclosure relates to a surface treatment method, a stainless steel component, an X-ray tube, an X-ray tube device, a method for manufacturing a stainless steel component, and a method for manufacturing an X-ray tube, and particularly relates to a surface treatment technique for obtaining a film with high emissivity. [Background Art]

[0002] An X-ray CT (Computed Tomography) apparatus includes an X-ray tube device that irradiates a subject with X-rays. The X-ray tube device includes an X-ray tube that generates X-rays by causing an electron beam to collide with an anode target. A rotating anode X-ray tube that rotates an anode target is used in X-ray CT apparatuses. The rotating anode X-ray tube includes an envelope that maintains a high vacuum inside, and an anode including the target and a rotor connected to the target is held inside the envelope.

[0003] The temperature of the target rises to about 1000°C due to the generation of X-rays. Most of the generated heat is radiated from the surface of the target to the envelope via radiation.

[0004] Patent Document 1 discloses a rotating anode X-ray tube having a structure that minimizes the amount of radiant heat transfer from the anode target to the rotor. [Prior Art Documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Unexamined Patent Publication No. Hei 5-62622 [Summary of the Invention] [Problem to be Solved by the Invention]

[0006] If the temperature of the target cannot be kept lower than the melting point of the target, there is a problem that the target melts. Therefore, in order to efficiently radiate heat from the anode, obtaining a film having high emissivity has been an issue to be solved.

[0007] This invention has been made in view of these circumstances, and aims to provide a surface treatment method that can be used in a vacuum, is low-cost, and produces a film with high emissivity with minimal environmental impact, as well as stainless steel parts, X-ray tubes, X-ray tube apparatus, a method for manufacturing stainless steel parts, and a method for manufacturing X-ray tubes. [Means for solving the problem]

[0008] To achieve the above objective, a surface treatment method according to a first aspect of this disclosure includes a sandblasting step of applying a sandblasting treatment to the surface of stainless steel, and a greening step of applying a greening treatment to the surface after the sandblasting step, wherein the surface roughness Ra of the surface after the greening step is 0.70 μm or more and 1.00 μm or less.

[0009] In the surface treatment method according to the second aspect of this disclosure, it is preferable that the surface roughness Ra of the surface after the greening treatment step is 0.75 μm or more and 0.90 μm or less, in the surface treatment method according to the first aspect.

[0010] In the surface treatment method according to the third aspect of this disclosure, it is preferable that the surface roughness Ra of the surface after the greening treatment step is 0.78 μm or more and 0.85 μm or less, in the surface treatment method according to the first aspect.

[0011] In the surface treatment method according to the fourth aspect of this disclosure, in the surface treatment method according to any one of the first to third aspects, the sandblasting treatment preferably includes blasting with an abrasive having a particle size of F150 or F180 as specified in JIS R6001.

[0012] A surface treatment method according to a fifth aspect of this disclosure, in a surface treatment method according to any one of the first to fourth aspects, the greening treatment includes holding in a wet hydrogen atmosphere of 1000°C or higher for 10 minutes or more.

[0013] In the surface treatment method according to the sixth aspect of this disclosure, in the surface treatment method according to any one aspect of the first to fifth aspects, it is preferable that the stainless steel is a martensitic stainless steel.

[0014] To achieve the above objective, the stainless steel part according to the seventh aspect of this disclosure is a stainless steel part in which a greening treatment is applied to the surface after sandblasting, wherein the surface roughness Ra of the surface after the greening treatment is 0.70 μm or more and 1.00 μm or less.

[0015] To achieve the above objective, the X-ray tube according to the eighth aspect of this disclosure is an X-ray tube comprising a cathode that generates an electron beam, an anode that emits X-rays when the electron beam collides with it, an enclosure that insulates and supports the cathode and anode in a vacuum atmosphere, a rotor that supports the anode, and a stainless steel component according to the seventh aspect.

[0016] To achieve the above objective, the X-ray tube apparatus according to the ninth aspect of this disclosure is an X-ray tube apparatus comprising an X-ray tube according to the eighth aspect and a container for housing the X-ray tube together with insulating oil.

[0017] To achieve the above objective, a method for manufacturing stainless steel parts according to the tenth aspect of this disclosure includes a sandblasting step of applying a sandblasting treatment to the surface of a stainless steel part, and a greening step of applying a greening treatment to the surface after the sandblasting step, wherein the surface roughness Ra of the surface after the greening step is 0.70 μm or more and 1.00 μm or less.

[0018] In order to achieve the above object, a method for manufacturing an X-ray tube according to an eleventh aspect of the present disclosure is a method for manufacturing an X-ray tube including: a cathode that generates an electron beam; an anode that emits X-rays when collided with by the electron beam; an envelope that insulates and supports the cathode and the anode in a vacuum atmosphere; and a rotor that supports the anode, the method comprising: a sandblasting step of performing sandblasting on a surface of at least a part of the rotor and the envelope; and a blackening step of performing blackening treatment on the surface after the sandblasting step, wherein a surface roughness Ra of the surface after the blackening step is 0.70 µm or more and 1.00 µm or less. [Advantageous Effects of Invention]

[0019] According to the present invention, a film with high emissivity that can be used in vacuum, is low-cost, and has low environmental load can be obtained. [Brief Description of Drawings]

[0020] [Figure 1] FIG. 1 is a schematic configuration diagram of an X-ray tube apparatus according to an embodiment. [Figure 2] FIG. 2 is a schematic configuration diagram of an X-ray tube. [Figure 3] FIG. 3 is a table showing measurement results of surface roughness Ra and emissivity ε in Tests 1 to 24. [Figure 4] FIG. 4 is a graph plotting the measurement results of Tests 1 to 22 with the horizontal axis representing surface roughness Ra and the vertical axis representing emissivity ε. [Figure 5] FIG. 5 is a photograph of the surface of a blackbody tape. [Figure 6] FIG. 6 is a photograph of the surfaces of Test 23 and Test 24. [Figure 7] FIG. 7 is a photograph of the surfaces of Test 3 and Test 8. [Figure 8] FIG. 8 is a photograph of the surfaces of Test 5 and Test 10. [Figure 9] FIG. 9 is a photograph of the surfaces of Test 12 and Test 18. [Figure 10] FIG. 10 is a photograph of the surfaces of Test 16 and Test 22. [Figure 11]FIG. 11 is surface roughness curves of Test 23 and Test 24. [Figure 12] FIG. 12 is surface roughness curves of Test 3, Test 8, Test 5, and Test 10. [Figure 13] FIG. 13 is surface roughness curves of Test 12, Test 18, Test 16, and Test 22. [Figure 14] FIG. 14 is a diagram for explaining the effect of the greening treatment. [Figure 15] FIG. 15 is a diagram for explaining a comparison between sandpaper treatment and sandblasting treatment. [Figure 16] FIG. 16 is a diagram for explaining the optimal value of surface roughness Ra. DETAILED DESCRIPTION OF EMBODIMENTS

[0021] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification, identical components are assigned identical reference signs, and overlapping descriptions are omitted as appropriate.

[0022] <X-ray tube device> FIG. 1 is a schematic configuration diagram of an X-ray tube device 10 according to an embodiment. The X-ray tube device 10 includes an X-ray tube container 12, a cooler 14, and an X-ray tube 100.

[0023] The X-ray tube container 12 is an aluminum plate case that houses the X-ray tube 100, and is lined with a lead plate for X-ray protection. The X-ray tube container 12 houses the X-ray tube 100 together with cooling oil 16 which is insulating oil. The X-ray tube 100 is immersed in the cooling oil 16 housed in the X-ray tube container 12, and is insulated from the X-ray tube container 12.

[0024] The X-ray tube container 12 and the cooler 14 are connected internally by a first conduit 18A and a second conduit 18B. The cooler 14 includes a fan (not shown) and a radiator (not shown), which cool the cooling oil 16 inside the cooler 14. The X-ray tube apparatus 10 includes a supply pump (not shown) that sends the insulating oil inside the cooler 14 into the X-ray tube container 12, and a recovery pump (not shown) that sends the insulating oil inside the X-ray tube container 12 into the cooler 14.

[0025] The cooling oil 16 cooled in the cooler 14 is circulated by the supply pump and recovery pump in the following order: cooler 14, first pipeline 18A, X-ray tube container 12, second pipeline 18B, and back to cooler 14. This allows the cooler 14 to cool the X-ray tube 100.

[0026] The X-ray tube container 12 is provided with a connector 20A that is electrically connected to the cathode 30 (see Figure 2) of the X-ray tube 100, and a connector 20B that is electrically connected to the rotating anode 40 (see Figure 2). A high-voltage generator (not shown) for applying a high voltage between the cathode 30 and the rotating anode 40 is connected to connectors 20A and 20B.

[0027] On the anode side of the X-ray tube 100, a drive coil 22 is positioned to receive power from a drive unit (not shown) and generate rotational force in the rotor 48 (see Figure 2).

[0028] Figure 2 is a schematic diagram of the X-ray tube 100. The X-ray tube 100 includes a cathode 30, a rotating anode 40 having a rotation mechanism that rotates around the central axis 100A of the X-ray tube 100, and an enclosure 50 that encloses and insulates the cathode 30 and the rotating anode 40 in a vacuum atmosphere.

[0029] The cathode 30 includes a filament (not shown) that emits electrons and a focusing body 32 that supports the filament and focuses electrons.

[0030] The rotating anode 40 includes a disc-shaped target 42 and a rotor 48. The target 42 is made of molybdenum. The target 42 has a target surface 44 that is inclined to emit X-rays toward an X-ray emission window 58, which will be described later. The target surface 44 is made of tungsten. The target 42 also has a heat storage section 46 on the side opposite to the target surface 44. The heat storage section 46 is made of graphite. The rotor 48 is rotatably supported by a rotation shaft (not shown) and rotates and supports the target 42. The rotor 48 is made of copper, and a thin layer of martensitic stainless steel is provided on the side surface 48A of the rotor 48.

[0031] The enclosure 50 includes a cylindrical metal enclosure 52 surrounding the cathode 30's focuser 32 and the rotating anode 40's target 42, a cathode-side glass enclosure 54 that provides insulating support for the cathode 30, and an anode-side glass enclosure 56 that provides insulating support for the rotating anode 40. The glass constituting the cathode-side glass enclosure 54 and the anode-side glass enclosure 56 has an emissivity of approximately 0.8 [dimensionless]. The metal enclosure 52 is made of martensitic stainless steel. The metal enclosure 52 has an opening, and an X-ray emission window 58 made of a heat-resistant metallic material with high X-ray transparency is coupled to the opening. In addition, a drive coil 22 (see Figure 1) is arranged around the anode-side glass enclosure 56.

[0032] When a negative voltage is applied to the filament of the cathode 30 from a high-voltage generator (not shown), the filament heats up and thermionic electrons are generated. When a positive voltage is applied to the target 42 of the rotating anode 40, thermionic electrons (electron beam) emitted from the filament and focused by the focuser 32 are accelerated by the potential difference between the filament and the target 42 and collide with the target 42. X-rays are generated when thermionic electrons collide with the target 42. Since the target surface 44 of the target 42 is inclined with respect to the central axis 100A of the X-ray tube 100, the generated X-rays are directed towards the X-ray emission window 58 and are emitted from the X-ray emission window 58 to the outside of the X-ray tube 100.

[0033] The X-ray tube apparatus 10 rotates the target 42 of the rotating anode 40 using the drive coil 22 and rotor 48. By rotating the target 42, the X-ray tube apparatus 10 changes the position where thermionic electrons collide on the target surface 44, thereby dispersing the heat load generated by the thermionic electron collisions.

[0034] The heat generated by thermionic electron collisions causes the target 42 to reach a high temperature of approximately 1000°C. Most of this heat is dissipated to the metal enclosure 52 by radiation from the surface of the rotating anode 40, and the remaining heat is transferred to the rotor 48 by thermal conduction. The metal enclosure 52 receives the heat from the target 42 and dissipates it to the cooling oil outside the X-ray tube 100. The rotor 48 dissipates the heat transferred from the target 42 mainly by radiation to the opposing anode-side glass enclosure 56.

[0035] Therefore, it is important to improve the emissivity of the inner surface 52A of the metal enclosure 52 and the side surface 48A of the rotor 48 in order to efficiently dissipate heat.

[0036] <Improved Emissivity> Surface treatment and film formation treatments are known as methods to improve emissivity. For example, black chrome plating, painting, titanium dioxide thermal spraying, greening treatment (wet hydrogen treatment) in which a metal containing chromium as the main component is treated at high temperature in hydrogen containing water vapor to form chromium oxide on the surface, and sandblasting treatment (sandblasting) in which abrasive material is sprayed.

[0037] However, each method had the following drawbacks: Black chrome plating generates wastewater, which is an environmental burden. Painting has the problem that solvents in the paint are gradually released into the vacuum, causing a decrease in the vacuum level. Titanium dioxide spraying is expensive and costly. Greening treatment is easy, but the improvement in emissivity is insufficient. Sandblasting is easy and low-cost, but the improvement in emissivity is insufficient.

[0038] Thus, both sandblasting and greening treatments have the effect of increasing emissivity. Therefore, it is conceivable that combining the two could further increase emissivity. However, suitable conditions are necessary to maximize emissivity by combining the two, and as a result of diligent research, the inventor has come to the conclusion that it is preferable to perform sandblasting and greening treatments to create a surface that satisfies the conditions described below.

[0039] <Examples> Each sample was subjected to sandpaper treatment, sandblasting treatment, and greening treatment, and its surface roughness Ra, emissivity ε, and surface condition were examined.

[0040] 〔material〕 The sample material used was unpolished SUS430 (SUS: Stainless Used Steel), a martensitic stainless steel with a high chromium content.

[0041] [Sandpaper treatment] For the sanding process, the sample surface was polished using sandpaper with grits of #40, #100, #500, #1000, and #2000, respectively.

[0042] [Sandblasting] For the sandblasting treatment, the sample surface was polished using abrasives with grit sizes F46, F70, F110, F150, F180, and F220, as specified in JIS R6001.

[0043] [Greening treatment] The greening treatment involved holding the sample in a wet hydrogen atmosphere at 1000°C for 10 minutes.

[0044] [Processing details for each sample] Tests 1-5 are samples in which the surface of the material was sanded. The grit sizes of the sandpaper used for the sanding process in Tests 1-5 were #2000, #1000, #500, #100, and #40, respectively. Tests 6-10 are samples in which the surfaces of Tests 1-5 were further treated with a greening process.

[0045] Tests 13-16 are samples in which the surface of the material was polished using sandblasting. The grit sizes of the abrasives specified in JIS R6001 used in the sandblasting of Tests 11-16 were F220, F180, F150, F100, F60, and F46, respectively. Tests 17-22 are samples in which the surfaces of Tests 11-16 were further treated with a greening process.

[0046] Test 23 is a sample of solid wood. Test 23 is a glossy board that has not undergone sanding or sandblasting. Test 24 is a sample of Test 23 with a greening treatment applied to its surface.

[0047] 〔measurement〕 The surface roughness Ra was measured using a SURFCOM-FLEX-35B surface roughness measuring instrument manufactured by Tokyo Seimitsu.

[0048] The emissivity ε was measured using a Horiba IT-340 radiation thermometer. For the measurement of emissivity ε, a blackbody tape and each of the 1-24 samples were placed on a hot plate. The temperature of the blackbody tape (ε=0.95) was measured, followed by the temperature of the sample. The emissivity ε was then adjusted to match the temperature of the blackbody tape.

[0049] 〔result〕 Figure 3 is a table showing the processing conditions for Tests 1-24, the measurement results for surface roughness Ra [μm], and the measurement results for emissivity ε [dimensionless]. Figure 4 is a graph plotting the measurement results for Tests 1-22 with surface roughness Ra [μm] on the horizontal axis and emissivity ε [dimensionless] on the vertical axis. As shown in Figures 3 and 4, the following results were obtained.

[0050] • Because sanding is done manually, variations in surface roughness (Ra) are likely to occur.

[0051] Even with the same surface roughness, a sandblasted surface has a higher emissivity ε than a sandpaper-treated surface.

[0052] The emissivity ε is further improved by applying a greening treatment to a surface that has been roughened by sandblasting or sandpaper treatment.

[0053] • Of the samples from Tests 1-10 that underwent sandpaper treatment, the sample from Test 8 had the highest emissivity ε, which was 0.66 [dimensionless].

[0054] • Among the samples from Tests 11-22 that underwent sandblasting, the samples from Test 18 and Test 19 had the highest emissivity ε, with an emissivity ε of 0.81 [dimensionless], respectively.

[0055] The samples from Test 18 and Test 19 had an emissivity ε exceeding 0.8 [dimensionless], with surface roughness Ra of 0.842 [μm] and 0.784 [μm], respectively. Tests 18 and 19 were samples that underwent sandblasting with abrasives with particle sizes F180 and F150, respectively, as defined in JIS R6001, followed by greening treatment.

[0056] The emissivity ε in Tests 18 and 19 is near the maximum value of emissivity ε, and it is presumed that emissivity ε decreases as the surface roughness Ra decreases. Therefore, it is presumed that the lower limit of the surface roughness Ra obtained by sandblasting and greening treatments must be 0.70 to 0.75 [μm].

[0057] From the changes in emissivity ε in Test 17 and Test 18, it can be inferred that the critical point for surface roughness Ra obtained by sandblasting and greening treatments is around 0.90 to 1.00 [μm]. Therefore, the upper limit of surface roughness Ra is 0.90 to 1.00 [μm].

[0058] Based on the above, the conditions for maximizing emissivity are preferably when the surface roughness Ra obtained by sandblasting and greening treatment is 0.70 μm or more and 1.00 μm or less, more preferably 0.75 μm or more and 0.90 μm or less, and even more preferably 0.78 μm or more and 0.85 μm or less. By satisfying these conditions, a high emissivity comparable to graphite, with an emissivity ε of about 0.8 [dimensionless], can be obtained.

[0059] The surface roughness Ra obtained from sandblasting and greening treatments can be confirmed to be within the above-mentioned range by surface observation and measurement using a surface roughness measuring instrument. Specifically, surface observation can confirm the presence or absence of sandblasting and greening treatments, and measurement using a surface roughness measuring instrument can determine the value of the surface roughness Ra. Alternatively, the emissivity ε can be measured using a non-contact thermometer to confirm that the emissivity ε is 0.80 or higher.

[0060] <Surface condition> Figure 5 shows photographs of the surface of a blackbody tape. F5A in Figure 5 is a photograph of the surface magnified 100 times, and F5B in Figure 5 is a photograph of the surface magnified to an arbitrary number of times. The emissivity ε of this blackbody tape was 0.95. As shown in Figure 5, the surface of the blackbody tape is formed by bundles of fine fibers, creating undulations, fine irregularities, and cavities. It is thought that these undulations, fine irregularities, and cavities contribute to the high emissivity.

[0061] Figure 6 shows photographs of the surfaces of Test 23 and Test 24, which is Test 23 with greening treatment applied. F6A in Figure 6 is a photograph of the surface of Test 23 taken at 100x magnification, and F6B in Figure 6 is a photograph of the surface of Test 23 taken at 3000x magnification. F6C in Figure 6 is a photograph of the surface of Test 24 taken at 100x magnification, and F6D in Figure 6 is a photograph of the surface of Test 24 taken at 3000x magnification. The surface of Test 23, which is made of solid wood, is flat, and the surface of Test 24, which has undergone greening treatment, has not changed much compared to the surface of Test 23.

[0062] Figure 7 shows photographs of the surfaces of Test 3, which underwent sandpaper treatment, and Test 8, which underwent greening treatment on Test 3. F7A in Figure 7 is a photograph of the surface of Test 3 taken at 100x magnification, and F7B in Figure 7 is a photograph of the surface of Test 3 taken at 3000x magnification. As shown in F7B, the surface of Test 3 has greater roughness than the surface of Test 23 (F6B) due to the sandpaper treatment. Also, F7C in Figure 7 is a photograph of the surface of Test 8 taken at 100x magnification, and F7D in Figure 7 is a photograph of the surface of Test 8 taken at 3000x magnification. As shown in F7D, granular material, which is a precipitate of chromium oxide, is present on the surface of Test 8 due to the greening treatment.

[0063] Figure 8 shows photographs of the surfaces of Test 5, which underwent sandpaper treatment, and Test 10, which underwent greening treatment on Test 5. F8A in Figure 8 is a photograph of the surface of Test 5 taken at 100x magnification, and F8B in Figure 8 is a photograph of the surface of Test 5 taken at 3000x magnification. As shown in F8B, the surface of Test 5 has a greater roughness than the surface of Test 3 in F7B. Also, F8C in Figure 8 is a photograph of the surface of Test 10 taken at 100x magnification, and F8D in Figure 8 is a photograph of the surface of Test 10 taken at 3000x magnification. As shown in F8B, granular material, which is a precipitate of chromium oxide, is observed on the surface of Test 10, but there is less granular material compared to the surface of Test 8 in F7D.

[0064] Figure 9 shows photographs of the surfaces of Test 12, which underwent sandblasting, and Test 18, which underwent greening treatment on Test 12. F9A in Figure 9 is a photograph of the surface of Test 12 taken at 100x magnification, and F9B in Figure 9 is a photograph of the surface of Test 12 taken at 3000x magnification. As shown in F9B, the surface of Test 12 has greater roughness due to sandblasting than the surface of Test 23 in F6B, and has a non-directional roughness compared to the surface of Test 3 in F7B. Also, F9C in Figure 9 is a photograph of the surface of Test 18 taken at 100x magnification, and F9D in Figure 9 is a photograph of the surface of Test 18 taken at 3000x magnification. As shown in F9D, the surface of Test 18 has a large number of granular materials, which are precipitates of chromium oxide, compared to the surface of Test 8 in F7D.

[0065] Figure 10 shows photographs of the surfaces of Test 16, which underwent sandblasting, and Test 22, which underwent greening treatment on Test 16. F10A in Figure 10 is a photograph of the surface of Test 16 taken at 100x magnification, and F10B in Figure 10 is a photograph of the surface of Test 16 taken at 3000x magnification. As shown in F10B, the surface of Test 16 has a greater roughness than the surface of Test 12 in F9B. Also, F10C in Figure 10 is a photograph of the surface of Test 22 taken at 100x magnification, and F10D in Figure 10 is a photograph of the surface of Test 22 taken at 3000x magnification. As shown in F10D, granular material, which is a precipitate of chromium oxide, is observed on the surface of Test 22, but there is less granular material compared to the surface of Test 18 in F9D.

[0066] Figures 11 to 13 show the surface roughness curves for each sample. In each figure, the horizontal axis represents the distance from a reference position [mm], and the vertical axis represents the roughness [μm], which is the surface height relative to the average plane. F11A in Figure 11 is the surface roughness curve for Test 23, and F11B in Figure 11 is the surface roughness curve for Test 24. F12A in Figure 12 is the surface roughness curve for Test 3, F12B in Figure 12 is the surface roughness curve for Test 8, F12C in Figure 12 is the surface roughness curve for Test 5, and F12D in Figure 12 is the surface roughness curve for Test 10. F13A in Figure 13 is the surface roughness curve for Test 12, F13B in Figure 13 is the surface roughness curve for Test 18, F13C in Figure 13 is the surface roughness curve for Test 16, and F13D in Figure 13 is the surface roughness curve for Test 22.

[0067] Observation of photographs of the surface after greening treatment reveals undulation due to granular material, fine irregularities, and voids, but as shown in Figures 11 to 13, the roughness measuring instrument was unable to detect the voids. Therefore, the conditions for maximizing the emissivity in the examples require not only a surface roughness Ra of 0.70 μm to 1.00 μm, but also a surface obtained through sandblasting and greening treatment.

[0068] <Factors contributing to improved emissivity> [Effects of greening treatment] Figure 14 is a diagram illustrating the effect of the greening treatment. F14A in Figure 14 schematically shows a cross-section of the surface before the greening treatment, and F14B in Figure 14 schematically shows a cross-section of the surface after the greening treatment. When greening treatment is applied, chromium oxide is deposited. This chromium oxide creates undulations and complex irregularities on the surface, increasing the emissivity ε. This is the same principle as why blackbody tape has a high emissivity ε. Furthermore, by roughening the surface in advance as shown in F14A, fine cavities are formed as shown in F14B, further complicating the surface shape. In other words, as granular material aggregates and is distributed, cavities are formed between the granular material, increasing the surface area. This improves the emissivity.

[0069] [Comparison of sandpaper treatment and sandblasting treatment] Figure 15 illustrates a comparison between sandpaper treatment and sandblasting treatment. F15A in Figure 15 schematically shows a cross-section of the surface after sandpaper treatment, and F15B in Figure 15 schematically shows a cross-section of the surface after sandblasting treatment. Sandpaper treatment polishes the surface in a linear pattern, so polished areas tend to remain in some places. On the other hand, sandblasting creates more complex irregularities on the surface on average than sandpaper treatment, resulting in a relatively higher emissivity.

[0070] [Optimal value for surface roughness Ra] Figure 16 is a diagram illustrating the optimal value of surface roughness Ra. F16A, F16B, and F16C in Figure 16 schematically show cross-sections of surfaces after sandpaper treatment, respectively. F16A shows a surface with a relatively small surface roughness Ra, F16C shows a surface with a relatively large surface roughness Ra, and F16B shows a surface with a surface roughness Ra that maximizes the emissivity ε. Furthermore, F16D, F16E, and F16F in Figure 16 schematically show cross-sections of surfaces after sandblasting treatment, respectively. F16D shows a surface with a relatively small surface roughness Ra, F16F shows a surface with a relatively large surface roughness Ra, and F16E shows a surface with a surface roughness Ra that maximizes the emissivity ε. F16G in Figure 16 shows a magnified portion of the surface of F16E.

[0071] As shown in Figure 16, neither sandpaper treatment nor sandblasting treatment necessarily results in higher emissivity with finer or coarser grits of sandpaper or abrasive material. Both sandpaper treatment and sandblasting treatment have peak values ​​for emissivity, and there is an appropriate roughness level at which emissivity is maximized. In other words, there is an appropriate roughness level for creating undulations, irregularities, and cavities across the entire surface.

[0072] <Summary> In the X-ray tube apparatus 10, it is important to improve the emissivity of the inner surface 52A of the metal enclosure 52 of the X-ray tube 100 and the side surface 48A of the rotor 48. To this end, the emissivity of the side surface 48A of the rotor 48 and the inner surface 52A of the metal enclosure 52 can be improved by a surface treatment method that includes a sandblasting step of applying sandblasting treatment to the side surface 48A of the rotor 48 and the inner surface 52A of the metal enclosure 52, and a greening step of applying greening treatment to the surface after the sandblasting step, wherein the surface roughness Ra of the surface after the greening step is 0.70 μm or more and 1.00 μm or less. The surface roughness Ra of the surface after the greening step is more preferably 0.75 μm or more and 0.90 μm or less, and even more preferably 0.78 μm or more and 0.85 μm or less.

[0073] Sandblasting includes blasting with abrasive material having a particle size of F150 or F180 as specified in JIS R6001. Greening includes holding in a wet hydrogen atmosphere at 1000°C or higher for 10 minutes or more.

[0074] A method for manufacturing stainless steel parts to improve emissivity includes a sandblasting step of applying a sandblasting treatment to the surface of the stainless steel part, and a greening treatment step of applying a greening treatment to the surface after the sandblasting step, wherein the surface roughness Ra of the surface after the greening treatment step is 0.70 μm or more and 1.00 μm or less. More preferably, the surface roughness Ra of the surface after the greening treatment step is 0.75 μm or more and 0.90 μm or less, and even more preferably 0.78 μm or more and 0.85 μm or less.

[0075] The stainless steel may be martensitic stainless steel. Stainless steel parts are not limited to those composed entirely of stainless steel, but may include those in which a layer of stainless steel is provided on at least a portion of the surface of a non-stainless steel part. A stainless steel part may be a rotor 48 that rotatably supports the target 42 of the rotating anode 40. The surface of the stainless steel part may be the side surface 48A of the rotor 48. A stainless steel part may be the metal enclosure 52 of the X-ray tube enclosure 50. The surface of the stainless steel part may be the inner surface 52A of the metal enclosure 52.

[0076] A method for manufacturing an X-ray tube comprising a cathode 30, a rotating anode 40, and an enclosure 50 that encloses the cathode 30 and the rotating anode 40 in a vacuum and airtight manner and provides insulating support, includes a sandblasting step of sandblasting the surface of at least a portion of the stainless steel of the side surface of the rotor 48 of the rotating anode 40 and the inner surface of the metal enclosure 52 of the enclosure 50, and a greening step of greening the surface after the sandblasting step, wherein the surface roughness Ra of the surface after the greening step is 0.70 μm or more and 1.00 μm or less. More preferably, the surface roughness Ra of the surface after the greening step is 0.75 μm or more and 0.90 μm or less, and even more preferably 0.78 μm or more and 0.85 μm or less.

[0077] The technical scope of the present invention is not limited to the scope described in the embodiments above. The configurations and other elements in each embodiment can be appropriately combined with those in each embodiment without departing from the spirit of the present invention. [Explanation of Symbols]

[0078] 10...X-ray tube device 12...X-ray tube container 14...Cooler 16...Cooling oil 18A…1st conduit 18B…Second conduit 20A… Connector 20B… Connector 22… Drive coil 30...Cathode 32…Focusing body 40... Rotating anode 42…Target 44…Target surface 46...Heat storage part 48... Rotor 48A…Side 50...Envelope 52...Metal envelope 52A...Inner surface 54…Cathode side glass enclosure 56... Anode-side glass enclosure 58...X-ray radiation window 100...X-ray tube 100A…Center axis

Claims

1. The sandblasting process involves applying a sandblasting treatment to the surface of stainless steel, A greening treatment step in which a greening treatment is applied to the surface after the sandblasting treatment step, Includes, The surface roughness Ra of the surface after the greening treatment process is 0.70 μm or more and 1.00 μm or less. Surface treatment method.

2. The surface treatment method according to claim 1, wherein the surface roughness Ra of the surface after the greening treatment step is 0.75 μm or more and 0.90 μm or less.

3. The surface treatment method according to claim 1, wherein the surface roughness Ra of the surface after the greening treatment step is 0.78 μm or more and 0.85 μm or less.

4. The aforementioned sandblasting process includes blasting an abrasive material with a particle size of F150 or F180 as defined in JIS R6001. The surface treatment method according to claim 1.

5. The aforementioned greening treatment includes holding the plants in a wet hydrogen atmosphere at 1000°C or higher for 10 minutes or more. The surface treatment method according to claim 1.

6. The aforementioned stainless steel is a martensitic stainless steel. A surface treatment method according to any one of claims 1 to 5.

7. Stainless steel parts whose surface has been treated with a greening process after sandblasting, The surface roughness Ra of the surface after the greening treatment is 0.70 μm or more and 1.00 μm or less. Stainless steel parts.

8. A cathode that generates an electron beam, The anode emits X-rays upon collision with the aforementioned electron beam, An enclosure that provides insulating support for the cathode and anode in a vacuum atmosphere, A rotor supporting the anode, The stainless steel part according to claim 7, An X-ray tube equipped with [a specific feature / equipment].

9. The X-ray tube according to claim 8, A container for housing the aforementioned X-ray tube together with insulating oil, An X-ray tube apparatus equipped with the following features.

10. The sandblasting process involves applying a sandblasting treatment to the surface of stainless steel parts. A greening treatment step in which a greening treatment is applied to the surface after the sandblasting treatment step, Includes, The surface roughness Ra of the surface after the greening treatment process is 0.70 μm or more and 1.00 μm or less. Manufacturing method for stainless steel parts.

11. A method for manufacturing an X-ray tube comprising: a cathode that generates an electron beam; an anode that emits X-rays when the electron beam collides with it; an enclosure that insulates and supports the cathode and the anode in a vacuum atmosphere; and a rotor that supports the anode, A sandblasting step in which sandblasting is applied to at least a portion of the surface of the rotor and the enclosure, A greening treatment step in which a greening treatment is applied to the surface after the sandblasting treatment step, Includes, The surface roughness Ra of the surface after the greening treatment process is 0.70 μm or more and 1.00 μm or less. A method for manufacturing X-ray tubes.

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