A method for straightening a niobium plate

Abstract

The present application provides a kind of niobium plate leveling method, which comprises: first leveling: niobium plate is first fed to leveling machine for leveling, with first bending angle, to get first leveling plate;Second leveling: after rotating the first leveling plate by α angle, it is fed to the leveling machine for the second time to carry out leveling, with second bending angle, to get second leveling plate;Wherein, the first bending angle is the included angle between the tangent of the first discharge end of niobium plate and the horizontal direction, the second bending angle is the included angle between the tangent of the second discharge end of niobium plate and the horizontal direction, 45°≤α≤90°, 50°≥the first bending angle≥the second bending angle>0°.The leveling method can improve the flatness and thickness uniformity of niobium plate, simplify the process flow, and meet the processing needs of high-precision pure niobium plate at a lower production cost.

Description

Technical Field

[0001] This invention relates to the field of non-ferrous metal material processing technology, specifically to a method for leveling niobium plates. Background Technology

[0002] Niobium, due to its high thermal strength, high melting point, and excellent corrosion resistance, is widely used in high-end fields such as aerospace and nuclear reactors. However, there is a significant technical bottleneck in the cold rolling process of niobium plates: due to niobium's rapid work hardening characteristics, the deformation resistance increases sharply during rolling, causing the rolls to bear extremely high compressive stress and intensifying elastic deformation and accelerating frictional loss. This phenomenon directly results in uneven stress distribution within the rolled piece, forming a mixed wave defect of central, edge, and rib waves, accompanied by thickness fluctuations, which severely restricts the yield of high-precision, small-sized niobium plates. In traditional rolling processes, the main methods for controlling wave and thickness defects include adjusting the roll profile curve, optimizing the reduction distribution, calibrating the roll gap, and temperature-controlled rolling. However, for niobium plates with small-sized, high-precision requirements, the above methods are still insufficient to completely eliminate wave and thickness unevenness defects caused by residual stress.

[0003] Therefore, a leveling process is typically introduced after rolling to further improve the flatness and thickness uniformity of the sheet metal. Common leveling methods include high-tonnage presses, long-term pressure holding, multi-pass leveling, and heating assistance. However, these methods generally suffer from high production costs, long processing cycles, and high equipment energy consumption, making it difficult to meet the leveling requirements of high-precision, small-sized pure niobium sheets. Furthermore, niobium metal hardens rapidly during processing, making it difficult to precisely control the parameters of the leveling machine, thus increasing the difficulty of leveling the sheet metal and making it difficult to meet usage standards.

[0004] Currently, there is limited research on optimizing the flatness and thickness uniformity of pure niobium plates through the leveling process. Existing related patents and research mainly focus on leveling methods for other metal plates. For example, Chinese patent application CN116516305A discloses a leveling method for target materials, employing multi-pass leveling and controlling the leveling area in each pass. However, this method requires prolonged 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, determining the appropriate leveling pressure through a calculated pressure formula and controlling the downward pressure using an overflow valve to ensure plate flatness. However, this method requires additional specialized equipment and is only applicable to plates within a specific size range, failing to meet the needs of multi-specification production. Chinese patent application CN117753824A proposes an improved scheme for a multi-roller leveling machine, improving the leveling accuracy of side plates by adding a feeding platform and limiting components. However, this method requires significant equipment modification, impacting production efficiency and having limited applicability to multi-specification plates. In addition, the paper "Research on Leveling and Annealing Process of Zirconium Alloy Plates" (DOI: 10.3969 / j.issn.1002-5065.2019.06.003) explores the use of annealing fixtures to heat treat zirconium alloy plates to improve their flatness and mechanical properties. However, this method requires additional tooling investment and faces compatibility issues in the production of plates of various specifications. Furthermore, the tooling loading process may damage the surface quality of the plates, affecting the performance of the final product.

[0005] In summary, existing leveling techniques still have many limitations when applied to high-precision pure niobium plates. There is an urgent need for an efficient leveling method that can improve the flatness and thickness uniformity of the plates, reduce production costs, and simplify the process to meet the processing requirements of high-precision pure niobium plates. Summary of the Invention

[0006] To improve the flatness and thickness uniformity of niobium plates, thereby meeting the processing requirements of high-precision pure niobium plates, while reducing production costs and simplifying the process, this application provides a niobium plate leveling method, which includes:

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

[0008] Secondary leveling: After rotating the primary leveling plate by an angle α, feed it into the leveling machine for a second time for leveling, and discharge it with a second bending angle to obtain the secondary leveling plate;

[0009] Wherein, the first bending angle is the angle between the tangent of the first discharge end of the niobium plate and the horizontal direction, and the second bending angle is the angle between the tangent of the second discharge end of the niobium plate and the horizontal direction, 45°≤α≤90°, 50°≥first bending angle≥second bending angle>0°. Attached Figure Description

[0010] The accompanying drawings are provided to further illustrate the invention and form part of this invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0011] Figure 1 This is a schematic diagram of the distribution of the leveling rollers and the rotation angle α in some embodiments of this application.

[0012] Figure 2 These are photographs of the niobium plate morphology before and after leveling in Embodiment 1 of this application. Detailed Implementation

[0013] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings and examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified, specific conditions in the examples are performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0014] As described in the background art, existing leveling techniques still have many limitations when applied to high-precision pure niobium plates. To improve the flatness and thickness uniformity of niobium plates while reducing production costs and simplifying the process, the first embodiment of this application provides a leveling method for niobium plates, which includes:

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

[0016] Secondary leveling: After rotating the primary leveling plate by an angle α, feed it into the leveling machine for a second time for leveling, and discharge it with a second bending angle to obtain the secondary leveling plate;

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

[0018] Figure 1 A schematic diagram is shown of the angle α of the rotation between the two leveling operations.

[0019] This invention, taking advantage of the properties of niobium metal, employs a two-stage bending and leveling process, along with adjustments to the infeed and discharge angles, to release the concentrated stress caused by undulations in the niobium plate and to homogenize the internal stress. This method avoids problems such as heating and pressure holding, effectively reducing production costs, improving the leveling accuracy of the niobium plate, and shortening the niobium plate leveling process.

[0020] In this invention, the bending angle of the niobium plate is created by adjusting the reduction 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 high-intensity initial deformation, while the smaller bending angle of the second leveling finely adjusts the microscopic residual stress, avoiding 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°, 4 The second bending angle may be 6°, 47°, 48°, 49°, 50° or within any two of the above angles; and / or the second bending angle may be 10°, 11°, 12°, 13°, 14°, 15°, 16°, 17°, 18°, 19°, 20°, 21°, 22°, 23°, 24°, 25°, 26°, 27°, 28°, 29°, 30° or within 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 with a first edge and a second edge that are perpendicular to each other. The niobium plate enters the leveling machine with the angle between the first edge and the axis of the roller of the leveling machine as 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°. Entering the leveling machine with the above-mentioned passing angle can reduce the stress concentration when the edge of the niobium plate contacts the roller, making the force on the niobium plate more uniform during the leveling process and improving the leveling accuracy.

[0023] For example, the angle of passage during a single leveling process 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 any two of the above angles.

[0024] For example, the angle of passage during secondary 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 any two of the above angles.

[0025] In some implementations, the temperature of the niobium plate is controlled between 20°C and 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 any two of the above temperature ranges. Controlling the niobium plate at the above temperatures enhances its plasticity, making its mechanical properties more stable and reducing the internal stress generated during the leveling process, thereby improving the leveling accuracy. Furthermore, because niobium itself has good low-temperature plasticity, low yield strength, and low sensitivity to oxidation, it can achieve good leveling results even at relatively low temperatures, while also achieving energy saving and consumption reduction, and improving the operational stability of the leveling machine. During the leveling process, the niobium plate will heat up due to the pressure. If the temperature of the niobium plate is found to be too high, it can be cooled down by means of air cooling or by using intermittent leveling to control the temperature of the niobium plate.

[0026] In some embodiments, the feed rate of the niobium plate is 1 m / min to 10 m / min. For example, the feed rate 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 any two of the above values. Controlling the feed rate of the niobium plate within a certain range allows the niobium plate to fully release stress and achieve sufficient uniformity of stress within the plane of the niobium plate during the leveling process, thereby better reducing defects on the surface of the niobium plate, improving leveling accuracy, and enhancing 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 applied to the sheet metal by the inlet roller and the outlet roller is defined as the compression difference. In a single leveling operation, the compression difference between the inlet roller and the outlet roller is 0.4 mm to 0.8 mm. For example, the compression difference between the inlet roller and the outlet roller in a single leveling operation can be 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, or any two of the above values. In some embodiments, in a secondary leveling operation, the compression difference between the inlet roller and the outlet roller is 0.3 mm to 0.6 mm. For example, the compression difference between the inlet roller and the outlet roller in a secondary leveling operation can be 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, or any two of the above values. The magnitude of the compression difference between the inlet roller and the outlet roller directly affects the degree of deformation of the niobium sheet during the leveling process. The aforementioned pressure difference allows the niobium plate to undergo more uniform bending deformation as it passes through the rollers, gradually eliminating the original unevenness and ultimately achieving higher leveling accuracy.

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

[0029] In some embodiments, the thickness of the niobium plate is 2mm-10mm. For example, the thickness of the niobium plate can be 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm or within 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] In other words, the method in this invention is not only applicable to the industrial production of large-scale niobium plates, but also suitable for the production of small-sized, high-precision niobium thin plates, meeting the diverse material performance requirements of different application scenarios.

[0032] In some implementations, a leveling process also includes reversing the niobium plate back to its initial leveling position.

[0033] In some implementations, the secondary leveling also includes reversing the primary leveling plate back to the initial position of the secondary leveling.

[0034] During the leveling process, the reverse retreat operation can be used to correct areas that are not completely leveled. The deformation direction of the niobium plate is partially reversed, which helps to balance internal stress, reduce residual stress, and make the overall flatness more uniform.

[0035] In some embodiments, the leveling machine includes at least nine rollers, with a spacing of 50mm-150mm between each roller. For example, the roller spacing can be 50mm, 60mm, 70mm, 80mm, 90mm, 100mm, 105mm, 110mm, 120mm, 130mm, 140mm, 150mm, or within any two of these values. Controlling the roller spacing allows for more uniform stress distribution on the niobium plate during leveling, fully releasing the material's internal stress and better accommodating niobium plates of different thicknesses and hardnesses.

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

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

[0038] It is evident that the method of this invention can achieve a flatness of ≤0.3mm by using only two leveling plates. This method not only shortens the process and reduces production costs, but also improves the leveling accuracy of niobium plates, thus meeting the needs of various application scenarios.

[0039] Example

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

[0041] The method for testing the flatness of niobium plates is as follows: Place the niobium plate on the worktable of a coordinate measuring machine, keep the ambient temperature stable and avoid vibration interference, and use a probe to select several measurement points on the surface of the niobium plate in a grid pattern or evenly distributed (usually no less than 9 points / m). 2 After the measurement begins, the system automatically collects the height coordinate data of each point and outputs the flatness result.

[0042] Example 1

[0043] Perform the following steps in sequence to achieve the desired level.

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

[0045] 2) First leveling: Adjust the niobium plate through angle to 0°, adjust the leveling machine parameters to keep the pressure difference between the inlet front roller and the outlet rear roller at 0.5mm, and adjust the outlet niobium plate bending angle to 20°.

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

[0047] 4) Second leveling: Rotate 90° to adjust the niobium plate through angle to 90°, adjust the leveling machine parameters to keep the pressure difference between the inlet front roller and the outlet rear roller at 0.3mm, and adjust the outlet niobium plate bending angle to 10°.

[0048] 5) Reverse return: After the niobium plate passes through the leveling machine in a bent state, push it back into the leveling machine in the same direction and position to level it back to its original position.

[0049] 6) After leveling, the flatness of the niobium plate was significantly improved, and the rolling deformation undulations caused by rolling along the vertical direction of rolling were significantly eliminated (some surfaces, such as...). Figure 2As shown in the right figure, the flatness of the niobium plate was measured to be 0.115 mm. Subsequent grinding reduced the amount of material removed by approximately 20%, resulting in a significant improvement in production efficiency.

[0050] Comparative Example 1

[0051] The only difference from Example 1 is that the plate is not rotated before the second leveling feed, and the passing angle of the niobium plate is kept at 0°.

[0052] Comparative Example 2

[0053] The only difference from Example 1 is that the plate is rotated 30° before the second leveling feed, so that the niobium plate passes through at a 30° angle.

[0054] Comparative Example 3

[0055] The only difference from Example 1 is that the pressure difference between the inlet front roller and the outlet rear roller is set to 0 during the first leveling process, so that the first bending angle of the niobium plate is 0°.

[0056] Comparative Example 4

[0057] The difference from Example 1 is that the pressure difference between the inlet front roller and the outlet rear roller is set to 0 during the first and second leveling processes, so that the first bending angle and the second bending angle of the niobium plate are both 0°.

[0058] The flatness of the first and second calibration plates of the above embodiments and comparative examples is recorded in Table 1.

[0059] Table 1

[0060] Compared with Comparative Examples 1-4, Example 1 showed a significant improvement in flatness after two leveling processes, and the flatness after the second leveling in Example 1 reached a high precision of 0.125 mm. It is evident that the leveling method of this invention can improve the flatness of niobium plates with a relatively simplified process, meeting the processing requirements of high-precision pure niobium plates.

[0061] The following investigation examines the effects of angle of penetration, pressure difference, bending angle, rotation angle, and feed rate on the flatness of niobium plates.

[0062] Example 2

[0063] The difference from Example 1 is that in the first leveling, the pressure difference between the inlet front roller and the outlet rear roller is kept at 0.8 mm, and the bending angle of the outlet niobium plate is adjusted to 30°. In the second leveling, the pressure difference between the inlet front roller and the outlet rear roller is kept at 0.4 mm, and the bending angle of the outlet niobium plate is adjusted to 15°.

[0064] Example 3

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

[0066] Example 4

[0067] The difference from Example 1 is that the rotation angle is 60° during the second calibration, so that the niobium plate passes through at an angle of 60°.

[0068] Example 5

[0069] The difference from Example 1 is that in the first leveling, the pressure difference between the inlet front roller and the outlet rear roller is kept at 0.8 mm, and the bending angle of the outlet niobium plate is adjusted to 30°. In the second leveling, the pressure difference between the inlet front roller and the outlet rear roller is kept at 0.6 mm, and the bending angle of the outlet niobium plate 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 a flatness of 1.2mm and a feed speed of 4m / min. The passing angle during the first leveling is 45°. After rotating 90° during the second leveling, the passing angle of the niobium plate is 135°. In addition, the pressure difference between the inlet front roller and the outlet rear roller during the first leveling is 0.4mm.

[0072] The flatness of the primary and secondary calibration plates of the above embodiments is recorded in Table 2.

[0073] Table 2

[0074] Data from Examples 3-6 show that after two leveling operations according to the method of the present invention, the flatness of the niobium plate was significantly improved. This not only simplifies the process and reduces production costs, but also achieves high final flatness accuracy, which can meet the processing requirements of high-precision pure niobium plates.

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

Claims

1. A method for leveling a niobium plate, the leveling method comprising: First leveling: The niobium plate is fed into the leveling machine for the first time for leveling, and is discharged with the first bending angle to obtain a first leveled plate; Secondary leveling: The primary leveling plate is rotated by an angle α and then fed into the leveling machine for a second time for leveling. It is then discharged with a second bending angle to obtain the secondary leveling plate. Wherein, the first bending angle is the angle between the tangent at the primary discharge end of the niobium plate and the horizontal direction, and the second bending angle is the angle between the tangent at the secondary discharge end of the niobium plate and the horizontal direction, where 45°≤α≤90°, and 50°≥first bending angle≥second bending angle>0°. 50° ≥ First bending angle ≥ 10°, and / or 30° ≥ Second bending angle ≥ 10°, The first and second leveling are bending leveling.

2. The leveling method according to claim 1, wherein, The niobium plate is a rectangular plate with a first edge and a second edge that are perpendicular to each other. The angle between the first edge and the roller axis of the leveling machine is the passing angle. The passing angle during the first leveling is between 0° and 45°, and / or the passing angle during the second leveling is between 90° and 135°.

3. The leveling method according to claim 1 or 2, wherein, The temperature of the niobium plate is controlled between 20℃ and 200℃ during the leveling process.

4. The leveling method according to claim 1 or 2, wherein, The feeding speed of the niobium plate is 1m / min - 10m / min.

5. The leveling method according to claim 1 or 2, wherein, The leveling machine includes an inlet roller and an outlet roller. In the first leveling, the pressure difference between the inlet roller and the outlet roller is 0.4-0.8 mm, and / or in the second leveling, the pressure difference between the inlet roller and the outlet roller is 0.3-0.6 mm.

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

7. The leveling method according to claim 1 or 2, wherein, The first leveling also includes the process of reversing the niobium plate back to the initial position of the first leveling.

8. The leveling method according to claim 1 or 2, wherein, The secondary leveling also includes reversing the primary leveling plate back to the initial position of the secondary leveling.

9. The leveling method according to claim 1 or 2, wherein, The leveling machine includes at least 9 rollers, with a spacing of 50mm-150mm between each roller.

10. The leveling method according to claim 1 or 2, wherein, The flatness of the primary calibration plate is ≤0.5mm; and / or the flatness of the secondary calibration plate is ≤0.3mm.

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