Niobium plate surface treatment method and planar niobium plate

Abstract

The invention provides a surface treatment method for a niobium plate. The surface treatment method comprises the steps that wet polishing treatment and cleaning treatment after polishing are conducted on the niobium plate. By means of the method, residues and chippings generated by surface polishing and grinding can be removed in time, the surface roughness of the niobium plate is reduced, and the machining efficiency is improved. In addition, the invention further provides a planar niobium plate obtained after treatment through the niobium plate surface treatment method.

Description

Technical Field

[0001] The present application relates to the technical field of niobium material processing, and in particular to a niobium plate surface treatment method and a flat niobium plate. Background Art

[0002] High-energy particle accelerators have outstanding advantages such as low loss, high current and high stability. High-energy particle accelerators and light source projects based on particle accelerators are important platforms for current frontier research in basic science and have become the mainstream of current accelerator technology development. Radio frequency superconducting cavities are the core components of high-energy particle accelerators. Niobium plates have become the preferred material for manufacturing radio frequency superconducting cavities due to their excellent superconducting properties and stability.

[0003] Since the low temperature performance of the RF superconducting cavity is directly affected by its surface quality, the surface quality of the niobium plate is also subject to relatively strict requirements. The prior art requires that the surface roughness of the finished superconducting niobium plate must meet Ra≤1.6μm and Rt≤15μm in both the vertical rolling direction and the rolling direction. In the prior art, dry polishing is commonly used to treat the surface of niobium plates. The disadvantages are: the surface roughness is high and foreign matter is easily pressed into the surface of the plate, making it difficult to obtain a high degree of smoothness and flatness. In addition, dry polishing usually produces a large amount of dust, causing environmental pollution. Summary of the invention

[0004] In view of the above-mentioned defects of the dry polishing process, the present application provides a surface treatment method for a niobium plate and a flat niobium plate. The surface treatment method can effectively reduce the surface roughness of the niobium plate.

[0005] A first aspect of the present application provides a surface treatment method for a niobium plate, the surface treatment method comprising: performing a wet polishing treatment on the niobium plate and a cleaning treatment after polishing.

[0006] In any embodiment of the first aspect, the wet polishing treatment of the surface treatment method comprises: humidifying the sand belt to obtain a wet sand belt; performing surface polishing treatment on the niobium plate using the wet sand belt, and moisturizing the wet sand belt using a polishing liquid during the surface polishing treatment.

[0007] In any embodiment of the first aspect, the polishing liquid is added at a rate of 3000 mL / min to 5000 mL / min.

[0008] In any embodiment of the first aspect, the abrasive belt is a nylon abrasive belt.

[0009] In any embodiment of the first aspect, a nylon sanding belt with a mesh size of 240 to 400 is selected and used.

[0010] In any embodiment of the first aspect, the abrasive belt is immersed in the polishing liquid for 0.5 to 2 minutes to obtain a wet abrasive belt.

[0011] In any embodiment of the first aspect, the wet polishing is performed using a wet polishing device, and the current of the wet polishing device is 12A-20A.

[0012] In any embodiment of the first aspect, the moving speed of the niobium plate is 2 m / min to 10 m / min, and / or the rotation speed of the abrasive belt is 200 rpm to 1500 rpm.

[0013] In any embodiment of the first aspect, the polishing liquid injected during the polishing process includes water and / or mineral oil.

[0014] In any embodiment of the first aspect, the cleaning treatment after polishing includes water washing and acid washing.

[0015] In any embodiment of the first aspect, the cleaning treatment after polishing includes cleaning agent cleaning, water cleaning and acid cleaning, and the cleaning agent includes a degreasing cleaning agent.

[0016] In any embodiment of the first aspect, before the wet polishing process, the surface treatment method further comprises the steps of sequentially performing a leveling process and a surface grinding process on the niobium plate.

[0017] In any embodiment of the first aspect, the flatness of the niobium plate after leveling is less than 0.6 mm.

[0018] In any embodiment of the first aspect, the surface defect depth of the niobium plate after the surface grinding treatment is less than the polishing reserve amount of the wet polishing treatment.

[0019] In any embodiment of the first aspect, the niobium plate is a superconducting niobium plate.

[0020] The second aspect of the present application provides a planar niobium plate, which is obtained by surface treatment using the surface treatment method of the first aspect. DETAILED DESCRIPTION

[0021] The following embodiments further describe the implementation of the present application in detail. The detailed description of the following embodiments is used to illustrate the principle of the present application, but cannot be used to limit the scope of the present application, that is, the present application is not limited to the described embodiments.

[0022] As described in the background of this application, the surface treatment effect achieved by the dry polishing process is not ideal and it is difficult to meet the surface finish and flatness requirements of niobium plates, especially superconducting niobium plates. In order to solve this problem, this application provides a surface treatment method for niobium plates, and a flat niobium plate obtained by using the surface treatment method.

[0023] In a first embodiment of the present application, a surface treatment method for a niobium plate is provided. The surface treatment method comprises: performing a wet polishing treatment on the niobium plate and a cleaning treatment after polishing.

[0024] When wet polishing niobium plates, the abrasive residues and metal debris generated during the surface polishing process can be removed in time, reducing the resulting surface wear and pollution, and reducing the surface roughness of the niobium plates. At the same time, the polishing liquid absorbs and reduces the temperature of the workpiece during wet polishing, playing a cooling role. In addition, compared with chemical polishing and electrochemical polishing, wet polishing is a more economical and environmentally friendly method, and it is not easy to form a hard passivation film on the surface of the plate after polishing, and there is no need to eliminate it through heat treatment later, which improves the processing efficiency.

[0025] In some embodiments of the present application, the wet polishing treatment of the surface treatment method includes: humidifying the sand belt to obtain a wet sand belt; polishing the niobium plate surface with the wet sand belt, and moisturizing the wet sand belt with a polishing liquid during the surface polishing process.

[0026] The abrasive belt is humidified in advance to give full play to the advantages of wet polishing and improve polishing efficiency. During the surface polishing process, the wet abrasive belt is moisturized with polishing liquid. On the one hand, the contact surface between the niobium plate and the abrasive belt is fully moistened. On the other hand, the polishing liquid can promptly remove the abrasive residue and metal debris on the surface of the niobium plate, reducing the resulting surface wear and pollution. At the same time, the polishing liquid absorbs and reduces the temperature of the workpiece, playing a cooling role.

[0027] The polishing speed and polishing effect are affected by the speed of adding the polishing liquid. If the speed of adding the polishing liquid is too fast, the polishing liquid will be wasted and the cost will increase. If the speed of adding the polishing liquid is too slow, the timeliness of removing the residue will decrease, which will affect the surface finish effect of wet polishing. In some embodiments, the speed of adding the polishing liquid is 3000mL / min to 5000mL / min, which not only avoids the waste of the polishing liquid, but also can use the polishing liquid to remove debris and pollutants in time and achieve a better cooling effect.

[0028] Generally, abrasive belts used for polishing metals are divided into fabric abrasive belts, paper abrasive belts and steel abrasive belts according to their base materials. Among them, fabric abrasive belts include non-woven abrasive belts, nylon abrasive belts, polyester cloth abrasive belts, blended cloth abrasive belts, etc., and the abrasives therein can be abrasives commonly used for metal polishing. Those skilled in the art can also select the abrasive belts used for the present application from the abrasive belts used for dry polishing of niobium plates. In some embodiments of the present application, the abrasive belt is a nylon abrasive belt, which has the characteristics of high strength, good flexibility and wear resistance, and light weight. Based on the above characteristics, the viscosity of the contact surface between the niobium plate and the nylon abrasive belt during wet polishing can be significantly smaller than that of abrasive belts of other base materials.

[0029] Generally, the smaller the mesh number of the abrasive belt, the higher the grinding efficiency, but the roughness of the processed surface is greater; on the contrary, the larger the mesh number of the abrasive belt, the lower the grinding efficiency, and the lower the roughness of the processed surface. In some embodiments of the present application, a nylon abrasive belt with a mesh of 240 to 400 is selected, and the abrasive belt within this mesh range is used for polishing, which can reduce the surface roughness required for the niobium plate and effectively improve the production efficiency.

[0030] In some embodiments of the present application, before being loaded into the polishing equipment for surface polishing, the sanding belt is humidified, for example, the sanding belt is immersed in the polishing liquid for 0.5 minute to 2 minutes to obtain a wet sanding belt, so that the sanding belt is fully moistened, and the surface quality obtained by polishing has good continuity and uniformity.

[0031] Conventional wet polishing equipment includes wet dust removal and environmental protection polishing all-in-one machine, wet polishing and grinding all-in-one machine, wet polishing machine, etc. In some embodiments of the present application, wet polishing is implemented using wet polishing equipment. Regardless of the type of wet polishing equipment, the pressure between the sand belt and the workpiece surface can be adjusted more accurately by adjusting the current. Increasing the current can increase the pressure and thus increase the friction between the two. Reducing the current will reduce the pressure and thus reduce the friction between the two. After experimental exploration, in some embodiments, the current of the wet polishing equipment is 12A to 20A, which is conducive to efficiently achieving high-quality polishing.

[0032] To better control the polishing amount and polishing efficiency, in some embodiments of the present application, the moving speed of the niobium plate is 2 m / min to 10 m / min, and / or the grinding belt speed is 200 rpm to 1500 rpm.

[0033] The polishing liquid used for wet polishing in the present application can be a conventional wet polishing liquid. In some embodiments of the present application, the polishing liquid injected during the polishing process includes water and / or mineral oil. In particular, when water is used as the polishing liquid, the cost of wet polishing is lower and the subsequent processing of the polishing liquid is more convenient.

[0034] In some embodiments of the present application, the cleaning treatment after polishing includes water washing and pickling. In some embodiments, the water washing step includes using high-pressure tap water to fully rinse the front and back surfaces of the plate. Optionally, the pressure range of the high-pressure tap water is 5MPa to 12MPa. In some embodiments, the pickling step includes using a pickling solution to pickle the niobium plate for 10 seconds to 60 seconds, and then using running water to rinse the surface for at least 10 seconds to remove residual acid. The surface of the niobium plate after pickling should maintain its metallic color, and the metallic luster can be seen without spots when observed with the naked eye. In some embodiments, the pickling solution in the above pickling step is composed of phosphoric acid with a concentration of not less than 85%, nitric acid with a concentration of 66%-68%, and hydrofluoric acid with a concentration of not less than 40%, preferably uniformly mixed according to a volume ratio of (phosphoric acid + nitric acid): hydrofluoric acid of 2:1 to 4:1. For example, the volume ratio of phosphoric acid, nitric acid, and hydrofluoric acid can be 1:1:1, 1:2:1, 2:1:1 or 2:2:1.

[0035] In some embodiments, the cleaning process after polishing includes cleaning with a cleaning agent, water washing and pickling, wherein the cleaning agent includes a degreasing cleaning agent, etc., and the cleaning agent is used to remove grease, dirt and other residues that may exist on the metal surface. Water washing and pickling can refer to the above methods.

[0036] When the flatness of the niobium plate treated by wet polishing in the present application is insufficient, or there are many surface defects, in some embodiments, the surface treatment method further includes the steps of leveling and surface grinding the niobium plate in sequence before wet polishing. Optionally, after leveling, the flatness of the niobium plate is less than 0.6 mm; optionally, after surface grinding, the depth of surface defects (such as pits, peeling, folds, cracks, etc.) of the niobium plate is less than the polishing reserve amount of wet polishing. The above-mentioned leveling and surface grinding can refer to conventional technologies, and this application will not repeat them.

[0037] In some embodiments of the present application, the niobium plate treated by the above surface treatment method is a superconducting niobium plate, thereby better reducing the surface roughness of the superconducting niobium plate.

[0038] In the second embodiment of the present application, a planar niobium plate is provided, which is obtained after being treated according to the surface treatment method of the first embodiment of the present application. The surface treatment method of the first embodiment of the present application greatly reduces the surface roughness of the niobium plate and improves the surface quality of the niobium plate. In some embodiments, the surface roughness Rt of the obtained planar niobium plate can reach 0.2μm to 0.9μm, and the maximum defect depth can be controlled below 15μm. Combined with the surface roughness requirements of the finished superconducting niobium plate in the prior art, the planar niobium plate in the second embodiment of the present application has excellent surface quality.

[0039] The beneficial effects of the present application will be further illustrated below in combination with examples and comparative examples, but the scope of the present invention is not limited to these examples.

[0040] Example 1

[0041] Step 1: The niobium plate is leveled and surface ground in sequence, so that the flatness of the niobium plate is less than 0.6 mm and the depth of surface defects is less than the polishing reserve of the wet polishing process.

[0042] Step 2: Select a nylon sanding belt with 400 mesh brown corundum or alumina as abrasive, humidify it, soak the sanding belt in water for 1 minute, and obtain a wet sanding belt.

[0043] Step 3: Use a wet polisher, load the wet sand belt obtained in step 2, and perform surface polishing on the niobium plate. During the surface polishing process, continuously inject water to moisturize the wet sand belt and fully moisten the contact surface between the niobium plate and the sand belt. The water addition rate is 3500mL / min. During the surface polishing process, the equipment current of the wet polisher is 16A, the moving speed of the niobium plate is 6 meters / minute, and the sand belt speed is 1200 revolutions / minute.

[0044] Step 4: The niobium plate obtained in step 4 is fully rinsed on the front and back surfaces with high-pressure tap water, and the pressure range of the high-pressure tap water is 5-12 MPa.

[0045] Step 5: pickling the niobium plate obtained in step 4, wherein the pickling solution is prepared by uniformly mixing phosphoric acid with a concentration of ≥85%, nitric acid with a concentration of 65%-68%, and hydrofluoric acid with a concentration of ≥40% in a volume ratio of 1:1:1, and the niobium plate is pickled for 1-300 seconds with the pickling solution, and then the surface is rinsed with running water for at least 10 seconds to remove residual acid, thereby obtaining a flat niobium plate.

[0046] Example 2

[0047] The only difference from Example 1 is the operation of step 2:

[0048] Step 2: Select a 400-mesh nylon sanding belt and use brown corundum or alumina as the abrasive for the sanding belt, humidify it, and soak the sanding belt in water for 0.5 minutes to obtain a wet sanding belt.

[0049] The remaining steps are the same as those in Example 1.

[0050] Example 3

[0051] The only difference from Example 1 is the operation of step 2:

[0052] Step 2: Select a 400-mesh nylon sanding belt and use brown corundum or alumina as the abrasive for the sanding belt, humidify it, and soak the sanding belt in water for 2 minutes to obtain a wet sanding belt.

[0053] The remaining steps are the same as those in Example 1.

[0054] Example 4

[0055] The only difference from Example 1 is the operation of step 2:

[0056] Step 2: Select a 240-mesh nylon sanding belt and use brown corundum or alumina as the abrasive for the sanding belt, humidify it, and soak the sanding belt in water for 1 minute to obtain a wet sanding belt.

[0057] The remaining steps are the same as those in Example 1.

[0058] Example 5

[0059] The difference from Example 1 is the operation of step 3:

[0060] Step 3: Use a wet polisher, load the wet sand belt obtained in step 2, and perform surface polishing on the niobium plate. During the surface polishing process, continuously inject water to moisturize the wet sand belt and fully moisten the contact surface between the niobium plate and the sand belt. The water addition rate is 3000mL / min. During the surface polishing process, the equipment current of the wet polisher is 16A, the moving speed of the niobium plate is 6 meters / minute, and the sand belt speed is 1200 revolutions / minute.

[0061] The remaining steps are the same as those in Example 1.

[0062] Example 6

[0063] The difference from Example 1 is the operation of step 3:

[0064] Step 3: Use a wet polisher, load the wet sand belt obtained in step 2, and perform surface polishing on the niobium plate. During the surface polishing process, continuously inject water to moisturize the wet sand belt and fully moisten the contact surface between the niobium plate and the sand belt. The water addition rate is 5000mL / min. During the surface polishing process, the equipment current of the wet polisher is 16A, the moving speed of the niobium plate is 6 meters / minute, and the sand belt speed is 1200 revolutions / minute.

[0065] The remaining steps are the same as those in Example 1.

[0066] Example 7

[0067] The only difference from Example 1 is the operation of step 3:

[0068] Step 3: Use a wet polisher, load the wet sand belt obtained in step 2, and perform surface polishing on the niobium plate. During the surface polishing process, continuously inject water to moisturize the wet sand belt and fully moisten the contact surface between the niobium plate and the sand belt. The water addition rate is 3500mL / min. During the surface polishing process, the equipment current of the wet polisher is 12A, the moving speed of the niobium plate is 6 meters / minute, and the sand belt speed is 1200 revolutions / minute.

[0069] The remaining steps are the same as those in Example 1.

[0070] Example 8

[0071] The difference from Example 1 is that only step 3 is performed:

[0072] Step 3: Use a wet polisher, load the wet sand belt obtained in step 2, and perform surface polishing on the niobium plate. During the surface polishing process, continuously inject water to moisturize the wet sand belt and fully moisten the contact surface between the niobium plate and the sand belt. The water addition rate is 3500mL / min. During the surface polishing process, the equipment current of the wet polisher is 20A, the moving speed of the niobium plate is 6 meters / minute, and the sand belt speed is 1200 revolutions / minute.

[0073] The remaining steps are the same as those in Example 1.

[0074] Example 9

[0075] The only difference from Example 1 is the operation of step 3:

[0076] Step 3: Use a wet polisher, load the wet sand belt obtained in step 2, and perform surface polishing on the niobium plate. During the surface polishing process, continuously inject water to moisturize the wet sand belt and fully moisten the contact surface between the niobium plate and the sand belt. The water addition rate is 3500mL / min. During the surface polishing process, the equipment current of the wet polisher is 16A, the moving speed of the niobium plate is 2 meters / minute, and the sand belt speed is 1500 rpm.

[0077] The remaining steps are the same as those in Example 1.

[0078] Example 10

[0079] The only difference from Example 1 is the operation of step 3:

[0080] Step 3: Use a wet polisher, load the wet sand belt obtained in step 2, and perform surface polishing on the niobium plate. During the surface polishing process, continuously inject water to moisturize the wet sand belt and fully moisten the contact surface between the niobium plate and the sand belt. The water addition rate is 3500mL / min. During the surface polishing process, the equipment current of the wet polisher is 16A, the moving speed of the niobium plate is 10 meters / minute, and the sand belt speed is 200 revolutions / minute.

[0081] The remaining steps are the same as those in Example 1.

[0082] Embodiment 11

[0083] The only difference from Example 1 is the operation of step 2:

[0084] Step 2: Select a 500-mesh nylon sanding belt, the abrasive used for the sanding belt is brown corundum or alumina, humidify it, soak the sanding belt in water for 1 minute to obtain a wet sanding belt.

[0085] The remaining steps are the same as those in Example 1.

[0086] Example 12

[0087] The only difference from Example 1 is the operation of step 3:

[0088] Step 3: Use a wet polisher, load the wet sand belt obtained in step 2, and perform surface polishing on the niobium plate. During the surface polishing process, continuously inject water to moisturize the wet sand belt and fully moisten the contact surface between the niobium plate and the sand belt. The water addition rate is 3500mL / min. During the surface polishing process, the equipment current of the wet polisher is 16A, the moving speed of the niobium plate is 12 meters / minute, and the sand belt speed is 1200 revolutions / minute.

[0089] The remaining steps are the same as those in Example 1.

[0090] Comparative Example 1

[0091] The difference from Example 1 is that step 2 is not performed, and step 3 is dry polishing, which is specifically as follows: a dry polishing machine is used, a nylon abrasive belt is loaded, the equipment current of the dry polishing machine is 16A, the moving speed of the niobium plate is 6 m / min, and the abrasive belt speed is 1200 rpm.

[0092] The remaining steps are the same as those in Example 1.

[0093] The flat niobium plates in the above examples and comparative examples were tested and their surface treatment quality was measured using a laser microscope (3D profilometer). The results are shown in Table 1 below:

[0094] Table 1

[0095] Rt / μm Ra / μm Example 1 11 0.3 Example 2 13 0.6 Example 3 12 0.3 Example 4 13 0.7 Example 5 13 0.7 Example 6 10 0.3 Example 7 13 0.8 Example 8 11 0.4 Example 9 10 0.3 Example 10 15 0.7 Embodiment 11 13 0.9 Example 12 15 0.9 Comparative Example 1 18 1.6

[0096] According to the data comparison of the above embodiments and Table 1, it can be found that the surface quality of the niobium plate is significantly improved after wet polishing in each embodiment. Moreover, the surface quality can be adjusted by controlling the type of abrasive belt, the mesh number of abrasive belt and the polishing conditions.

[0097] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A surface treatment method for a niobium plate, characterized in that: The surface treatment method comprises: performing wet polishing treatment on the niobium plate and cleaning treatment after polishing.

2. The surface treatment method according to claim 1, characterized in that: The wet polishing process comprises: The sand belt is humidified to obtain a wet sand belt; The wet sand belt is used to perform surface polishing on the niobium plate, and during the surface polishing, the wet sand belt is kept moisturized by polishing liquid; Optionally, the polishing liquid is added at a rate of 3000 mL / min to 5000 mL / min.

3. The surface treatment method according to claim 2, characterized in that: The abrasive belt is a nylon abrasive belt, which can be a nylon abrasive belt with meshes of 240 to 400.

4. The surface treatment method according to claim 2 or 3, characterized in that: The abrasive belt is immersed in the polishing liquid for 0.5 to 2 minutes to obtain the wet abrasive belt.

5. The surface treatment method according to any one of claims 1 to 4, characterized in that: The wet polishing is performed using a wet polishing device, and the working current of the wet polishing device is 12A-20A.

6. The surface treatment method according to any one of claims 1 to 5, characterized in that: During the wet polishing process, the moving speed of the niobium plate is 2 m / min to 10 m / min, and / or the rotation speed of the abrasive belt is 200 rpm to 1500 rpm.

7. The surface treatment method according to any one of claims 2 to 5, characterized in that: The polishing liquid includes water and / or mineral oil.

8. The surface treatment method according to any one of claims 1 to 7, characterized in that: The cleaning treatment after polishing includes water washing and acid washing; optionally, the cleaning treatment after polishing includes cleaning agent cleaning, water washing and acid washing, and the cleaning agent includes a degreasing cleaning agent.

9. The surface treatment method according to any one of claims 1 to 8, characterized in that: Before the wet polishing treatment, the surface treatment method further comprises the steps of sequentially performing leveling treatment and surface grinding treatment on the niobium plate. Optionally, after the leveling treatment, the flatness of the niobium plate is less than 0.6 mm; optionally, after the surface grinding treatment, the surface defect depth of the niobium plate is less than the polishing reserve of the wet polishing treatment.

10. The surface treatment method according to any one of claims 1 to 9, characterized in that: The niobium plate is a superconducting niobium plate.

11. A flat niobium plate, characterized in that: The flat niobium plate is obtained by surface treatment according to any one of claims 1 to 10.