Niobium plate leveling method

Abstract

The invention provides a niobium plate leveling method which comprises the following steps: primary leveling: feeding a niobium plate to a leveling machine for the first time for leveling, and discharging at a first bending angle to obtain a primary leveled plate; secondary leveling is conducted, specifically, after the primary leveling plate is rotated by an angle alpha, the primary leveling plate is fed into the leveling machine for leveling in a secondary feeding mode, discharging is conducted at a second bending angle, and a secondary leveling plate is obtained; wherein the first bending angle is the included angle between the tangent line of the primary discharging end of the niobium plate and the horizontal direction, the second bending angle is the included angle between the tangent line of the secondary discharging end of the niobium plate and the horizontal direction, alpha is larger than or equal to 45 degrees and smaller than or equal to 90 degrees, and the first bending angle is larger than or equal to 50 degrees and larger than or equal to the second bending angle and larger than 0 degree. According to the leveling method, the technological process can be simplified while the flatness and the thickness uniformity of the niobium plate are improved, and the machining requirement of the high-precision pure niobium plate is met with low production cost.

Description

Technical Field

[0001] The present invention relates to the technical field of non-ferrous metal material processing, and particularly to a leveling method for niobium plates. Background Art

[0002] Due to its high thermal strength, high melting point and excellent corrosion resistance, metallic niobium is widely used in high-end fields such as aerospace and nuclear reactors. However, there are significant technical bottlenecks in the cold rolling forming process of niobium plates: due to the rapid work hardening characteristics of niobium, the deformation resistance increases sharply during rolling, resulting in extremely high compressive stress on the rolls, which in turn causes increased elastic deformation and accelerated friction loss. This phenomenon directly leads to uneven internal stress distribution in the rolled piece, forming a mixed waviness defect of center wave, edge wave and rib wave, and at the same time accompanied by thickness fluctuations, seriously restricting the yield of high-precision small-size niobium plates. In traditional rolling processes, the means for controlling waviness and thickness defects mainly include adjusting the roll profile curve, optimizing the reduction distribution, calibrating the roll gap clearance, and temperature-controlled rolling, etc. However, for niobium plates with small-size and high-precision requirements, the above methods are still difficult to completely eliminate the waviness and thickness unevenness defects caused by residual stress.

[0003] Therefore, it is usually necessary to introduce a leveling process after rolling to further improve the flatness and thickness uniformity of the plate. Common leveling means include large-tonnage presses, long-time pressure holding, multi-pass leveling, and heating assistance, etc. However, these methods generally have problems such as high production cost, long processing cycle, and high equipment energy consumption, and are difficult to meet the leveling requirements of high-precision small-size pure niobium plates. In addition, niobium metal hardens relatively fast during processing, making it difficult to accurately control the parameters of the leveling machine, thus increasing the difficulty of leveling the plate and making it difficult to meet the usage standards.

[0004] At present, there is little technical research on optimizing the flatness and thickness uniformity of pure niobium plates through the leveling process. Existing related patents and research mainly focus on the leveling methods of other metal plates. For example, Chinese Patent Application CN116516305A discloses a leveling method for target materials, which adopts multi-pass leveling and controls the leveling area range during each pass of leveling. However, this method requires long-term pressure holding, resulting in low processing efficiency and high production costs; Chinese Patent Application CN116116931A provides a leveling device for small and medium-sized plates, which determines the appropriate leveling pressure by calculating the pressure formula and uses an overflow valve to control the downward pressure to ensure the flatness of the plate. However, this method requires additional equipment investment and is only applicable to plates within a specific size range, unable to meet the production requirements of multiple specifications; Chinese Patent Application CN117753824A proposes an improvement scheme for a multi-roll leveling machine, which improves the leveling accuracy of the side plates by adding a feeding platform and a limiting component. However, this method has high requirements for equipment transformation, affects production efficiency, and has limited applicability to plates of multiple specifications. In addition, the paper "Research on the Leveling and Annealing Process of Zirconium Alloy Plates" (DOI: 10.3969 / j.issn.1002-5065.2019.06.003) discusses the heat treatment of zirconium alloy plates through an annealing tooling to improve their flatness and mechanical properties. However, this method requires additional tooling investment, faces adaptability problems in the production of plates of multiple specifications, and may damage the surface quality of the plates during the tooling loading process, affecting the performance of the final product.

[0005] In summary, there are still many limitations in the existing leveling technologies when applied to high-precision pure niobium plates. There is an urgent need for an efficient leveling method that can not only improve the flatness and thickness uniformity of the plates but also reduce production costs and simplify the process flow to meet the processing requirements of high-precision pure niobium plates. Summary of the Invention

[0006] In order to improve the flatness and thickness uniformity of niobium plates to meet the processing requirements of high-precision pure niobium plates while reducing production costs and simplifying the process flow, the present application provides a leveling method for niobium plates, which includes:

[0007] Primary leveling: The niobium plate is fed into the leveling machine for the first time for leveling and discharged at the first bending angle to obtain a primary leveled plate;

[0008] Secondary leveling: The primary leveled plate is rotated by an angle α and then fed into the leveling machine for the second time for leveling and discharged at the second bending angle to obtain a secondary leveled plate;

[0009] Wherein, the first bending angle is the angle between the tangent line at the first discharging end of the niobium plate and the horizontal direction, the second bending angle is the angle between the tangent line at the second discharging end of the niobium plate and the horizontal direction, 45° ≤ α ≤ 90°, and 50° ≥ the first bending angle ≥ the second bending angle > 0°. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The accompanying drawings here are used to provide a further understanding of the present invention, and constitute a part of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention, and do not constitute an improper limitation to the present invention. In the drawings:

[0011] Figure 1 It is a schematic diagram of the leveling roller distribution and the rotation angle α in some embodiments of the present application.

[0012] Figure 2 It is a photo of the niobium plate before and after leveling in Example 1 of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0013] The following will describe the implementation schemes of the present invention in detail with reference to the drawings and embodiments. However, those skilled in the art will understand that the following embodiments are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. For those not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments not specified in the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0014] As described in the background art, there are still many limitations in the existing leveling technology when applied to high-precision pure niobium plates. In order to improve the flatness and thickness uniformity of the niobium plate, while reducing the production cost and simplifying the process flow. The first embodiment of the present application provides a leveling method for a niobium plate, and the leveling method includes:

[0015] Primary leveling: The niobium plate is first fed into the leveling machine for leveling, and discharged at the first bending angle to obtain a primary leveled plate;

[0016] Secondary leveling: The primary leveled plate is rotated by an angle of α and then fed into the leveling machine for leveling for the second time, and discharged at the second bending angle to obtain a secondary leveled plate;

[0017] Wherein, the first bending angle is the angle between the tangent line at the first discharging end of the niobium plate and the horizontal direction, the second bending angle is the angle between the tangent line at the second discharging end of the niobium plate and the horizontal direction, 45° ≤ α ≤ 90°, and 50° ≥ the first bending angle ≥ the second bending angle > 0°.

[0018] Figure 1 It shows a schematic diagram of the rotation angle α during the two-leveling process.

[0019] The present invention combines the characteristics of niobium metal, adopts two bending leveling and adjusts the feeding and discharging angles to release the wave-shaped concentrated stress in the niobium plate and homogenize the internal stress of the niobium plate. This method avoids problems such as heating and pressure holding, effectively reduces production costs, improves the leveling accuracy of the niobium plate, and shortens the niobium plate leveling process.

[0020] In the present invention, the niobium plate is bent at an angle by adjusting the amount of pressure of the rollers in the leveling machine. In some embodiments, 50°≥first bending angle≥10°, and / or 30°≥second bending angle≥10°. The larger bending angle of the first leveling quickly eliminates the macroscopic internal stress of the niobium plate after rolling through the higher intensity initial deformation, while the smaller bending angle of the second leveling is finely leveled for the microscopic residual stress to avoid lattice distortion or edge cracking caused by a single large deformation.

[0021] For example, the first bending angle can be 10°, 11°, 12°, 13°, 14°, 15°, 16°, 17°, 18°, 19°, 20°, 21°, 22°, 23°, 24°, 25°, 26°, 27°, 28°, 29°, 30°, 31°, 32°, 33°, 34°, 35°, 36°, 37°, 38°, 39°, 40°, 41°, 42°, 43°, 44°, 45°, 46°, 47°, 48°, 49°, 50°, 51°, 52°, 53°, 54°, 55°, 56°, 57°, 58°, 59°, 60°, 61°, 62°, 63°, 64°, 65°, 66°, 67°, 68°, 69°, 70°, 71°, 72°, 73°, 74°, 75°, 76°, 77°, 78°, 79°, 80°, 6°, 47°, 48°, 49°, 50° or within the range of any two of the above angles; and / or, the second bending angle can be 10°, 11°, 12°, 13°, 14°, 15°, 16°, 17°, 18°, 19°, 20°, 21°, 22°, 23°, 24°, 25°, 26°, 27°, 28°, 29°, 30° or within the range of any two of the above angles, and the second bending angle ≤ the first bending angle.

[0022] In some embodiments, the niobium plate is a rectangular plate having a first edge and a second edge perpendicular to each other. The angle between the first edge of the niobium plate and the axis of the roller of the leveling machine is the passing angle. The passing angle during the first leveling is between 0° and 45°, and the passing angle during the second leveling is between 90° and 135°. The niobium plate enters the leveling machine at the above passing angle, which can reduce the stress concentration when the edge of the niobium plate contacts the roller, so that the niobium plate is subjected to more uniform force during the leveling process, thereby improving the leveling accuracy.

[0023] For example, the passing angle during the first leveling can be 0°, 1°, 2°, 3°, 4°, 5°, 6°, 7°, 8°, 9°, 10°, 11°, 12°, 13°, 14°, 15°, 16°, 17°, 18°, 19°, 20°, 21°, 22°, 23°, 24°, 25°, 26°, 27°, 28°, 29°, 30°, 31°, 32°, 33°, 34°, 35°, 36°, 37°, 38°, 39°, 40°, 41°, 42°, 43°, 44°, 45° or within the range of any two of the above angles.

[0024] For example, the passing angle during the second leveling can be 90°, 91°, 92°, 93°, 94°, 95°, 96°, 97°, 98°, 99°, 100°, 101°, 102°, 103°, 104°, 105°, 106°, 107°, 108°, 109°, 110°, 111°, 112°, 113°, 114°, 115°, 116°, 117°, 118°, 119°, 120°, 121°, 122°, 123°, 124°, 125°, 126°, 127°, 128°, 129°, 130°, 131°, 132°, 133°, 134°, 135° or within the range of any two of the above angles.

[0025] In some embodiments, the temperature of the niobium plate is controlled at 20°C - 200°C during the leveling process. For example, the temperature of the niobium plate can be 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C or within the range of any two of the above temperatures. Controlling the niobium plate at the above temperatures can enhance its plasticity, make the mechanical properties more stable, reduce the internal stress generated during the leveling process, and thus improve the leveling accuracy. In addition, due to the good low-temperature plasticity, low yield strength, and low sensitivity to oxidation of niobium itself, it can achieve good leveling effects even at relatively low temperatures, while achieving the effects of energy conservation and consumption reduction, and improving the operation stability of the leveling machine. During the leveling process, the temperature of the niobium plate will rise due to the pressure effect. If it is found that the temperature of the niobium plate is high, it can be cooled by air cooling or other means or intermittent leveling can be used to control the temperature of the niobium plate.

[0026] In some embodiments, the feeding speed of the niobium plate is 1 m / min - 10 m / min. For example, the feeding speed of the niobium plate can be 1 m / min, 2 m / min, 3 m / min, 4 m / min, 5 m / min, 6 m / min, 7 m / min, 8 m / min, 9 m / min, 10 m / min, or within the range of any two of the above values. Controlling the feeding speed of the niobium plate within a certain range can enable the niobium plate to fully release stress during the leveling force application process and make the stress fully uniform within the plane of the niobium plate, better reducing the defects on the surface of the niobium plate, thereby improving the leveling accuracy and the controllability of the leveling process.

[0027] In some embodiments, the leveling machine includes an inlet roller and an outlet roller. The difference in the vertical compression amount applied by the inlet roller and the outlet roller to the plate is defined as the reduction difference. The reduction difference between the inlet roller and the outlet roller during one-time leveling is 0.4 mm - 0.8 mm. For example, the reduction difference between the inlet roller and the outlet roller during one-time leveling can be 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, or within the range of any two of the above values. In some embodiments, the reduction difference between the inlet roller and the outlet roller during secondary leveling is 0.3 mm - 0.6 mm. For example, the reduction difference between the inlet roller and the outlet roller during secondary leveling can be 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, or within the range of any two of the above values. The magnitude of the reduction difference between the inlet roller and the outlet roller directly affects the degree of deformation of the niobium plate during the leveling process. The above reduction difference can cause the niobium plate to produce more uniform bending deformation when passing through the rollers, gradually eliminate the original unevenness, and ultimately achieve higher leveling accuracy.

[0028] In some embodiments, the specifications of the niobium plate are within the range of (300 mm - 800 mm) × (300 mm - 800 mm). For example, the specifications of the niobium plate can be 300 mm × 300 mm, 300 mm × 500 mm, 300 mm × 800 mm, 500 mm × 500 mm, 500 mm × 800 mm, 800 mm × 800 mm, or other specifications within the above range.

[0029] In some embodiments, the thickness of the niobium plate is 2 mm - 10 mm. For example, the thickness of the niobium plate can be 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, or within the range of any two of the above values.

[0030] In some embodiments, the niobium plate is a 3N5 grade niobium plate, a 4N grade niobium plate, or a 4N5 grade niobium plate.

[0031] That is to say, the method of the present invention is not only applicable to the production of large-scale industrial niobium plates, but also suitable for the production of small-sized niobium thin plates with high precision requirements, meeting the various requirements of different application scenarios for material properties.

[0032] In some embodiments, the primary leveling further includes a process of returning the niobium plate to an initial position of the primary leveling.

[0033] In some embodiments, the secondary leveling further includes returning the primary leveling plate to an initial position of the secondary leveling.

[0034] During the leveling process, the reverse return operation can be used to correct the partially incompletely leveled parts. The deformation direction of the niobium plate is partially reversed, which helps to balance the internal stress, reduce the residual stress, and make the overall flatness more uniform.

[0035] In some embodiments, the leveling machine includes at least 9 rollers, and the spacing between the rollers is 50 mm-150 mm. For example, the spacing between the rollers can be 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, 105 mm, 110 mm, 120 mm, 130 mm, 140 mm, 150 mm, or within the range of any two of the above values. Controlling the roller spacing can make the niobium plate more uniformly stressed during the leveling process, fully release the internal stress of the material, and better adapt to niobium plates of different thicknesses and hardnesses.

[0036] In some embodiments, the flatness of the primary calibration plate is ≤0.5 mm. For example, the flatness of the primary calibration plate can be 0.5 mm, 0.48 mm, 0.46 mm, 0.44 mm, 0.42 mm, 0.4 mm, 0.38 mm, 0.36 mm, 0.34 mm, 0.32 mm, 0.3 mm, 0.28 mm, 0.26 mm, 0.24 mm, 0.22 mm, 0.2 mm, 0.18 mm, 0.16 mm, 0.14 mm, 0.12 mm, 0.1 mm, or within the range of any two of the above values, or ≤0.1 mm.

[0037] In some embodiments, the flatness of the secondary correction plate is ≤0.3 mm. For example, the flatness of the secondary correction plate can be 0.3 mm, 0.29 mm, 0.28 mm, 0.27 mm, 0.26 mm, 0.25 mm, 0.24 mm, 0.23 mm, 0.22 mm, 0.21 mm, 0.2 mm, 0.19 mm, 0.18 mm, 0.17 mm, 0.16 mm, 0.15 mm, 0.14 mm, 0.13 mm, 0.12 mm, 0.11 mm, 0.1 mm, or within the range of any two of the above values, or ≤0.1 mm.

[0038] It can be seen that the secondary leveling plate obtained by using the method of the present invention through only two leveling operations can achieve a technical effect of a flatness ≤ 0.3 mm. While shortening the process flow and reducing production costs, this method also improves the leveling accuracy of the niobium plate and can meet the requirements of various application scenarios.

[0039] Example

[0040] The beneficial effects of the present application will be further described below in conjunction with examples and comparative examples, but the scope of the present invention is not limited to these examples.

[0041] The method for detecting the flatness of the niobium plate is as follows: Place the niobium plate on the workbench of a coordinate measuring machine, keep the environmental temperature stable and avoid vibration interference. Use a probe to select several measurement points on the surface of the niobium plate in a grid pattern or evenly distributed (usually not less than 9 points / m 2 ). After starting the measurement, the system automatically collects the height coordinate data of each point and outputs the flatness result.

[0042] Example 1

[0043] The following steps are carried out in sequence for leveling.

[0044] 1) Leveling preparation: The raw material is a 4N grade niobium plate with dimensions of L500×B500×δ3mm after rolling deformation (as shown in the left figure for some surfaces), and its flatness is 1.2 mm. As Figure 2 shown, 15 rollers with a diameter of 100 mm are arranged vertically up and down, the roller spacing is set to 105 mm, and the feeding speed is set to 3 m / min. Figure 1 shown, 15 rollers with a diameter of 100 mm are arranged vertically up and down, the roller spacing is set to 105 mm, and the feeding speed is set to 3 m / min.

[0045] 2) First leveling: Adjust the passing angle of the niobium plate to 0°, adjust the parameters of the leveling machine so that the pressure difference between the front roller at the entrance and the rear roller at the exit is maintained at 0.5 mm, and adjust the bending angle of the niobium plate at the exit to 20°.

[0046] 3) Reverse return: After the niobium plate in the bent state passes through the leveling machine, it is pushed into the leveling machine in the same direction and at the same position in reverse to level it to the original position, and its flatness is 0.485 mm.

[0047] 4) Second leveling: Rotate 90° to adjust the passing angle of the niobium plate to 90°, adjust the parameters of the leveling machine so that the pressure difference between the front roller at the entrance and the rear roller at the exit is maintained at 0.3 mm, and adjust the bending angle of the niobium plate at the exit to 10°.

[0048] 5) Reverse return: After the niobium plate in the bent state passes through the leveling machine, it is pushed into the leveling machine in the same direction and at the same position in reverse to level it to the original position.

[0049] 6) After leveling, the flatness of the niobium plate is significantly improved, and the rolling deformation undulations that occurred along the direction perpendicular to rolling due to rolling disappear significantly (for some surfaces, as Figure 2As shown in the right figure, the flatness of the niobium plate was detected to be 0.115 mm. It was observed that the subsequent grinding removal amount decreased by about 20%, and the production efficiency was significantly improved.

[0050] Comparative Example 1

[0051] The difference from Example 1 was only that it did not rotate before the second leveling feeding, and the passing angle of the niobium plate was maintained at 0°.

[0052] Comparative Example 2

[0053] The difference from Example 1 was only that it rotated 30° before the second leveling feeding, and the passing angle of the niobium plate was adjusted to 30°.

[0054] Comparative Example 3

[0055] The difference from Example 1 was only that the difference in the pressing down between the front roller before the entrance and the rear roller after the exit was set to 0 during the first leveling process, so that the first bending angle of the niobium plate was 0°.

[0056] Comparative Example 4

[0057] The difference from Example 1 was that the difference in the pressing down between the front roller before the entrance and the rear roller after the exit was set to 0 during both the first and second leveling processes, so that both the first bending angle and the second bending angle of the niobium plate were 0°.

[0058] The flatness records of the first and second leveling plates in each of the above examples and comparative examples are shown in Table 1.

[0059] Table 1

[0060] Compared with Comparative Examples 1-4, the flatness after two-leveling in Example 1 was significantly improved, and the flatness after the second leveling in Example 1 reached a relatively high precision of 0.125 mm. It can be seen that the leveling method in the present invention can improve the flatness of the niobium plate with a relatively simplified process flow, meeting the processing requirements of high-precision pure niobium plates.

[0061] Next, the effects of the passing angle, the difference in the pressing down, the bending angle, the rotation angle, and the feeding speed on the flatness of the niobium plate were investigated.

[0062] Example 2

[0063] The difference from Example 1 was that the difference in the pressing down between the front roller before the entrance and the rear roller after the exit was maintained at 0.8 mm during the first leveling, the bending angle of the niobium plate at the exit was adjusted to 30°, the difference in the pressing down between the front roller before the entrance and the rear roller after the exit was maintained at 0.4 mm during the second leveling, and the bending angle of the niobium plate at the exit was adjusted to 15°.

[0064] Example 3

[0065] The difference from Example 1 is that in the first leveling, the passing angle of the niobium plate is adjusted to 30°, and after rotating 90° in the second leveling, the passing angle of the niobium plate is 120°.

[0066] Example 4

[0067] The difference from Example 1 is that in the second leveling, the rotation angle is 60°, so that the passing angle of the niobium plate is 60°.

[0068] Example 5

[0069] The difference from Example 1 is that in the first leveling, the difference in the depression between the front roll at the entrance and the rear roll at the exit is maintained at 0.8 mm, the bending angle of the niobium plate at the exit is adjusted to 30°, in the second leveling, the difference in the depression between the front roll at the entrance and the rear roll at the exit is maintained at 0.6 mm, and the bending angle of the niobium plate at the exit is adjusted to 20°.

[0070] Example 6

[0071] The difference from Example 1 is that the raw material is a 4N grade niobium plate with φ450×δ8.2 mm, its flatness is 1.2 mm, the feeding speed is set to 4 m / min, the passing angle in the first leveling is 45°, after rotating 90° in the second leveling, the passing angle of the niobium plate is 135°, and the difference in the depression between the front roll at the entrance and the rear roll at the exit in the first leveling is 0.4 mm.

[0072] The flatness of the first and second leveling plates of each of the above examples is recorded in Table 2.

[0073] Table 2

[0074] The data of Examples 3-6 show that after two-leveling carried out according to the method of the present invention, the flatness of the niobium plate has been significantly improved. Not only the process is simplified and the production cost is low, but also the final flatness accuracy is high, which can meet the processing requirements of high-precision pure niobium plates.

[0075] Although the specific embodiments of the present invention have been described in detail, those skilled in the art will understand that according to all the teachings that have been disclosed, various modifications and substitutions can be made to those details, and these changes are all within the protection scope of the present invention. The entire scope of the present invention is given by the appended claims and any equivalents thereof.

Claims

1. A leveling method for niobium plates, the leveling method comprising: Primary leveling: The niobium plate is fed into the leveling machine for the first time for leveling and discharged with a first bending angle to obtain a primary leveled plate; Secondary leveling: After rotating the primary leveled plate by an angle α, it is fed into the leveling machine for the second time for leveling and discharged with a second bending angle to obtain a secondary leveled plate; Wherein, the first bending angle is the included angle between the tangent line of the primary discharge end of the niobium plate and the horizontal direction, and the second bending angle is the included angle between the tangent line of the secondary discharge end of the niobium plate and the horizontal direction, 45° ≤ α ≤ 90°, 50° ≥ the first bending angle ≥ the second bending angle > 0°.

2. The leveling method according to claim 1, wherein 50° ≥ the first bending angle ≥ 10°, and / or 30° ≥ the second bending angle ≥ 10°.

3. The leveling method according to claim 1 or 2, wherein, The niobium plate is a rectangular plate, the rectangular plate has a first edge and a second edge perpendicular to each other, the niobium plate uses the included angle between the first edge and the axis of the roller of the leveling machine as the passing angle, the passing angle during the primary leveling is between 0° - 45°, and / or the passing angle during the secondary leveling is between 90° - 135°.

4. The leveling method according to any one of claims 1-3, wherein, During the leveling process, the temperature of the niobium plate is controlled at 20°C - 200°C.

5. The leveling method according to any one of claims 1-4, wherein, The feeding speed of the niobium plate is 1 m / min - 10 m / min.

6. The leveling method according to any one of claims 1-5, wherein, The leveling machine includes an inlet roller and an outlet roller, the reduction difference between the inlet roller and the outlet roller during the primary leveling is 0.4 - 0.8 mm, and / or the reduction difference between the inlet roller and the outlet roller during the secondary leveling is 0.3 - 0.6 mm.

7. The leveling method according to any one of claims 1-6, wherein, The niobium plate satisfies at least one of the following: The specification of the niobium plate is in the range of (300 mm - 800 mm) × (300 mm - 800 mm); The thickness of the niobium plate is 2 mm - 10 mm; The niobium plate is a 3N5 grade niobium plate, a 4N grade niobium plate or a 4N5 grade niobium plate.

8. The leveling method according to any one of claims 1-7, wherein, The primary leveling also includes the process of reversely retreating the niobium plate to the initial position of the primary leveling.

9. The leveling method according to any one of claims 1-8, wherein, The secondary leveling also includes reversely retreating the primary leveled plate to the initial position of the secondary leveling.

10. The leveling method according to any one of claims 1-9, wherein, The leveling machine includes at least 9 rollers, and the spacing between each roller is 50 mm - 150 mm.

11. The leveling method according to any one of claims 1-10, wherein, The flatness of the primary leveled plate ≤ 0.5 mm; and / or the flatness of the secondary leveled plate ≤ 0.3 mm.

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