Processing method of TA18 alloy pipe

Abstract

The invention discloses a processing method of a TA18 alloy pipe in the technical field of metal processing, which comprises the following steps: S1, carrying out two-roller cold rolling on a titanium alloy pipe blank; s2, the titanium alloy pipe subjected to two-roller cold rolling is subjected to degreasing treatment; s3, the titanium alloy pipe subjected to degreasing treatment is subjected to heat treatment and straightened; s4, the step S1, the step S2 and the step S3 are sequentially completed as a cold rolling cycle, the cold rolling cycle is repeated for multiple times, and machining of a titanium alloy pipe semi-finished product is completed; s5, the titanium alloy pipe semi-finished product is subjected to heat treatment and straightening; s6, the straightened titanium alloy pipe semi-finished product is subjected to three-roller cold rolling; s7, the titanium alloy pipe subjected to three-roller cold rolling is subjected to degreasing and acid pickling treatment; and S8, the titanium alloy pipe subjected to degreasing and acid pickling treatment is subjected to heat treatment and straightened again, the problem that the shrinkage strain ratio is too large due to rolling with the large machining deformation value is effectively solved, and the flattening performance of the titanium alloy pipe is greatly improved while the strict requirements for the mechanical property and the shrinkage strain ratio in the aerospace field are met.

Description

Technical Field

[0001] The present invention relates to the technical field of metal processing, and in particular to a processing method of a TA18 alloy tube. Background Art

[0002] TA18 alloy (Ti-3Al-2.5V), a near-alpha titanium alloy, has been widely used in aerospace, medicine, and other fields due to its excellent ductility, corrosion resistance, superior cold formability, and high fatigue strength. However, during the preparation of titanium alloy tubes, an increase in the shrinkage strain ratio parameter leads to a decrease in flattening performance, and even slight changes in this parameter can significantly affect the mechanical properties of the titanium tube. Therefore, the development process and processing technology of titanium alloy tubes that meet aerospace requirements in terms of flattening performance, mechanical properties, and shrinkage strain ratio parameters are extremely difficult.

[0003] Traditional rolling methods for reducing shrinkage strain ratios typically involve reducing the cold rolling ratio during the diameter reduction process. However, this approach has several drawbacks. First, the rolling process design is complex. Second, reducing the cold rolling ratio also causes changes in the mechanical properties of the rolled titanium alloy tube. Furthermore, excessively low cold rolling ratios can cause wrinkles in the titanium alloy tube during rolling, significantly reducing the quality of the tube's inner surface.

[0004] In view of the above situation, it is necessary to improve the processing method to produce titanium alloy tubes that meet the mechanical properties, shrinkage strain ratio and surface quality requirements of aerospace. Summary of the Invention

[0005] In order to overcome the deficiencies of the prior art, the technical problem to be solved by the present invention is to prepare a titanium alloy tube that simultaneously meets the mechanical properties, shrinkage strain ratio and surface quality requirements of aerospace by improving the processing method.

[0006] The technical solution adopted by the present invention to solve its technical problem is: A method for processing a TA18 alloy tube comprises the following steps: S1: titanium alloy tube blank is subjected to two-roll cold rolling; S2: Degreasing the titanium alloy tube after two-roll cold rolling; S3: heat treating and straightening the degreased titanium alloy tube; S4: completing step S1, step S2 and step S3 in sequence constitutes one cold rolling cycle, and repeating the cold rolling cycle multiple times to complete the processing of the titanium alloy tube semi-finished product; S5: heat treating and straightening the titanium alloy tube semi-finished product; S6: subjecting the straightened titanium alloy tube semi-finished product to three-roll cold rolling; S7: Degreasing and pickling the titanium alloy tube after three-roll cold rolling; S8: The titanium alloy tube after degreasing and pickling is heat treated and straightened again to complete the processing of the finished alloy tube.

[0007] Furthermore, before step S1, the titanium alloy tube blank is subjected to surface inspection, and titanium alloy tube blanks with burrs, pits and cracks on the surface are removed.

[0008] Furthermore, before step S1, the outer diameter dimensional tolerance of the titanium alloy tube blank is detected to be less than 0.1 mm, and the wall thickness dimensional tolerance is less than 0.3 mm.

[0009] Furthermore, in step S1, the two-roll cold rolling processing rate ranges from 0.5 to 0.7, and the processing deformation value ranges from 1.3 to 2.0.

[0010] Furthermore, in step S3, the heat treatment process includes: annealing at a temperature range of 650° C. to 800° C. for 0.5 h to 3.0 h.

[0011] Furthermore, in step S5, the straightness of the titanium alloy tube semi-finished product after straightening is less than 1 mm / m.

[0012] Furthermore, the heat treatment process in step S5 includes: annealing at a temperature range of 550° C. to 700° C. for 0.5 h to 3.0 h.

[0013] Furthermore, in step S6, the processing rate of the titanium alloy tube after the three-roll cold rolling process is in the range of 0.3-0.5, and the processing deformation value is in the range of 1.0-2.0.

[0014] Furthermore, in step S8, the heat treatment process includes: annealing at a temperature within a range of 380° C. to 540° C. for 1.0 h to 3.0 h.

[0015] The beneficial effects of the present invention are: Through multiple cycles of alternating two-roll cold rolling and thermal heat treatment processes, not only a large deformation amount and a large processing rate of the alloy tube are achieved, but also a uniform refinement of the grains is achieved, which significantly improves the plasticity of the material, thereby greatly improving the subsequent flattening performance of the material. Moreover, the alternating rolling process makes the surface quality of the titanium tube excellent, and no additional surface finishing treatment is required, and it can directly enter the next process, thereby greatly reducing production costs. Subsequently, through heat treatment of the titanium alloy tube semi-finished product, it causes incomplete recrystallization, and the titanium alloy tube is reduced in diameter using three-roll cold rolling. The deformation non-uniformity caused by the size difference of different grains during the cold rolling process is used to form an uneven distribution of grain orientation. This microstructural change significantly reduces the shrinkage strain ratio of the titanium alloy finished tube, effectively solving the problem of the large shrinkage strain ratio caused by rolling with large processing deformation values. While meeting the strict requirements of the aerospace field for mechanical properties and shrinkage strain ratio, it greatly improves the flattening performance of the titanium alloy tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the process flow of the present invention; DETAILED DESCRIPTION

[0017] Example 1 The present invention will be further described below with reference to the accompanying drawings.

[0018] This application proposes a processing method for TA18 alloy tube, comprising the following steps: S1: The titanium alloy tube billet undergoes two-roll cold rolling. Before the cold rolling operation, the titanium alloy tube billet undergoes surface inspection and removes any burrs, pits, and cracks on the surface to ensure that the titanium alloy tube billet is free of burrs, pits, and cracks. The two-roll cold rolling process controls the cold rolling processing ratio within the range of 0.5-0.7 and the processing deformation value within the range of 1.3-2.0. Specifically, the parameters of the two-roll cold rolling mill are controlled to achieve the corresponding parameter data range. After cold rolling, the outer diameter dimension tolerance of the titanium alloy tube billet is less than 0.1mm, and the wall thickness dimension tolerance is less than 0.3mm, ensuring the preset processing accuracy.

[0019] S2: Degreasing the titanium alloy tube after two-roll cold rolling; the degreasing process adopts the existing degreasing process to perform degreasing and oil removal treatment to ensure that the surface of the titanium alloy tube after rolling is free of impurities such as oil stains.

[0020] S3: heat treating and straightening the titanium alloy tube after degreasing; the heat treatment process includes: annealing at a temperature of 650° C. to 800° C. for 0.5 h to 3.0 h to ensure uniform grain orientation of the titanium alloy tube.

[0021] S4: completing step S1, step S2 and step S3 in sequence is a cold rolling cycle, and the above cold rolling cycles are repeated multiple times to complete the processing of the titanium alloy tube semi-finished product; the two-roll cold rolling and thermal heat treatment process of alternating multiple cycles not only achieves a larger deformation and a larger processing rate of the alloy tube, but also achieves uniform grain refinement, significantly improves the plasticity of the material, and thus greatly improves the subsequent flattening performance of the material. Moreover, the alternating rolling process makes the surface quality of the titanium tube excellent, and no additional surface finishing treatment is required, and it can directly enter the next step, thereby greatly reducing the production cost.

[0022] S5: Heat treating and straightening the titanium alloy semi-finished tube. The subsequent heat treatment causes incomplete recrystallization of the titanium alloy semi-finished tube, minimizing the impact on subsequent processes. The straightened titanium alloy semi-finished tube has a straightness of less than 1 mm / m. The heat treatment process includes annealing at a temperature between 550°C and 700°C for 0.5 to 3.0 hours.

[0023] S6: The straightened titanium alloy semi-finished tube is subjected to three-roll cold rolling; wherein, the processing ratio of the titanium alloy tube after three-roll cold rolling ranges from 0.3-0.5, and the processing deformation value ranges from 1.0-2.0. Three-roll cold rolling reduces the diameter of the titanium alloy tube. It utilizes the deformation non-uniformity caused by the size differences of different grains during the cold rolling process to form an uneven distribution of grain orientation. This microstructural change significantly reduces the shrinkage strain ratio of the titanium alloy finished tube, effectively solving the problem of excessive shrinkage strain ratio caused by rolling with large processing deformation values. While meeting the strict requirements of the aerospace industry for mechanical properties and shrinkage strain ratio, it also significantly improves the flattening performance of the titanium alloy tube.

[0024] S7: Degreasing and pickling the titanium alloy tube after three-roll cold rolling; the final degreasing and pickling treatment ensures that the surface of the titanium alloy tube is free of oil, dirt and impurities.

[0025] S8: After degreasing and pickling, the titanium alloy tube is heat treated and straightened again to complete the processing of the finished alloy tube. The heat treatment process includes: annealing at a temperature of 380℃-540℃ for 1.0h-3.0h to ensure that the grain orientation distribution of the final titanium alloy tube is uniform.

[0026] In this embodiment, the specific operations are: The rolling method for processing a titanium alloy tube blank with an outer diameter × wall thickness = 44 mm × 7.5 mm into a TA18 alloy tube with an outer diameter × wall thickness = 14 mm × 1 mm is as follows: A 44 mm × 7.5 mm titanium alloy tube billet was subjected to alternating cycles of two-roll cold rolling, surface finishing, and annealing. Three cold rolling cycles were performed: 44 mm × 7.5 mm → 32 mm × 4.5 mm → 22 mm × 2.4 mm → 16 mm × 1.4 mm. The first cold rolling cycle had a processing ratio of 0.55 and a processing deformation of 1.47. The second cold rolling cycle had a processing ratio of 0.62 and a processing deformation of 1.49. The third cold rolling cycle had a processing ratio of 0.57 and a processing deformation of 1.53. A 16 mm × 1. mm titanium alloy semi-finished tube was annealed at 600°C for 1 hour. The 16 mm × 1.4 mm titanium alloy semi-finished tube was cold rolled to 14 mm × 1 mm using a three-roll cold rolling mill. The cold rolling cycle had a cold rolling load of 0.36 and a processing deformation of 2.29. A 14 mm × 1 mm TA18 titanium alloy tube was stress-relief annealed at 400°C for 1 hour. The final product, a 14mm x 1mm TA18 titanium alloy tube, has a smooth surface without scratches, pits, wrinkles, or other defects. The flattening performance is qualified, and when the pressure plate spacing reaches 12mm, there are no cracks, cracks, or stretch marks on the titanium tube surface.

[0027] Example 2 The rolling method for processing a titanium alloy tube blank with an outer diameter × wall thickness = 32 mm × 6 mm into a TA18 alloy tube with an outer diameter × wall thickness = 10 mm × 0.8 mm is as follows: A 32mm×6mm titanium alloy tube billet was subjected to alternating cycles of two-roll cold rolling, surface finishing, and annealing. Three cold rolling cycles were performed: 32mm×6mm→22mm×3.5mm→16mm×2mm→12mm×1.2mm. The first cold rolling cycle had a processing ratio of 0.58 and a processing deformation of 1.33. The second cold rolling cycle had a processing ratio of 0.57 and a processing deformation of 1.57. The third cold rolling cycle had a processing ratio of 0.54 and a processing deformation of 1.60. A 12mm×1.2mm titanium alloy semi-finished tube was annealed at 580°C for 1 hour. The 12mm×1.2mm titanium alloy semi-finished tube was cold rolled to 10mm×0.8mm using a three-roll cold rolling mill. The cold rolling cycle had a cold rolling load of 0.43 and a processing deformation of 2. A 10mm×0.8mm TA18 titanium alloy tube was stress-relief annealed at 400°C for 1 hour. The final product, a 10mm x 0.8mm TA18 titanium alloy tube, has a smooth surface free of scratches, pits, wrinkles, and other defects. The flattening performance is acceptable, and when the platen spacing is 8.7mm, there are no cracks, splits, or stretch marks on the titanium tube surface.

[0028] Comparative Example 1 Compared to the specific operation process in Example 1, the annealing temperature in step S3 was adjusted to 750°C and maintained for 1 hour. This resulted in a 14 mm × 1 mm TA18 titanium alloy tube with a smooth surface free of scratches, pits, wrinkles, and other defects. However, the flattening performance was unsatisfactory, with cracks appearing at the 12 o'clock position on the inner surface of the titanium tube when the platen spacing reached 12.5 mm.

[0029] Comparative Example 2 Compared with the specific operation process in Example 2, the difference is that the processing rate and processing deformation value in the three cold rolling cycles are adjusted. Specifically, the processing rate of the first cold rolling cycle is 0.58, the processing deformation value is 1.33, the processing rate of the second cold rolling cycle is 0.45, the processing deformation value is 0.84, and the processing rate of the third cold rolling cycle is 0.64, and the processing deformation value is 2.22. After the second cold rolling cycle is completed, scratches, wrinkles and other defects have appeared on the inner surface. Subsequently, a 10mm×0.8mm TA18 titanium alloy tube was obtained, which had defects such as scratches and wrinkles on the inner surface and failed the flattening performance test.

[0030] By comparing Example 1 with Comparative Example 1, it can be concluded that the annealing temperature in step S3 can be within a reasonable range, which can ensure that the flattening performance of the final titanium alloy tube is good; by comparing Example 2 with Comparative Example 2, it can be concluded that setting the processing rate and deformation amount within a reasonable range during rolling can ensure good surface quality and good flattening performance of the titanium alloy tube.

[0031] In summary, the present invention proposes a processing method for TA18 alloy tubes, which first adopts alternating cold rolling and annealing processes to prepare titanium alloy tube semi-finished products with uniform structure. In the cold rolling process, the large deformation and high processing rate rolling technology is used, which not only achieves uniform grain refinement, significantly improves the plasticity of the material, and thus greatly improves the subsequent flattening performance of the material, but also the application of high processing rate rolling technology makes the surface quality of the titanium tube excellent, without the need for additional surface finishing treatment, it can directly enter the next step, thereby greatly reducing production costs. Finally, by adjusting the near-final annealing temperature of the titanium alloy tube semi-finished product, it causes incomplete recrystallization, and uses a three-roll cold rolling mill for diameter reduction. The deformation non-uniformity caused by the size difference of different grains during the cold rolling process is used to form an uneven distribution of grain orientation. This microstructural change significantly reduces the shrinkage strain ratio of the titanium alloy finished tube, effectively solves the problem of the large shrinkage strain ratio caused by high processing rate rolling, and while meeting the strict requirements of the aerospace field for mechanical properties and shrinkage strain ratio, it greatly improves the flattening performance of the titanium alloy tube.

Claims

1. A method for processing a TA18 alloy tube, characterized in that: The following steps are included: S1: titanium alloy tube blank is subjected to two-roll cold rolling; S2: Degreasing the titanium alloy tube after two-roll cold rolling; S3: heat treating and straightening the degreased titanium alloy tube; S4: completing step S1, step S2 and step S3 in sequence constitutes a cold rolling cycle, and repeating the above cold rolling cycles multiple times to complete the processing of the titanium alloy tube semi-finished product; S5: heat treating and straightening the titanium alloy tube semi-finished product; S6: subjecting the straightened titanium alloy tube semi-finished product to three-roll cold rolling; S7: Degreasing and pickling the titanium alloy tube after three-roll cold rolling; S8: The titanium alloy tube after degreasing and pickling is heat treated and straightened again to complete the processing of the finished alloy tube.

2. The processing method of a TA18 alloy tube according to claim 1, characterized in that: Before step S1, the titanium alloy tube blank is subjected to surface inspection, and titanium alloy tube blanks with burrs, pits and cracks on the surface are removed.

3. The processing method of a TA18 alloy tube according to claim 1, characterized in that: Before step S1, the outer diameter tolerance of the titanium alloy tube blank is detected to be less than 0.1 mm, and the wall thickness tolerance is less than 0.3 mm.

4. The method for processing a TA18 alloy tube according to claim 1, characterized in that: In step S1, the two-roll cold rolling processing rate range is 0.5-0.7, and the processing deformation value range is 1.3-2.

0.

5. The processing method of a TA18 alloy tube according to claim 1, characterized in that: In step S3, the heat treatment process includes: annealing at a temperature range of 650° C. to 800° C. for 0.5 h to 3.0 h.

6. The method for processing a TA18 alloy tube according to claim 1, characterized in that: In step S5, the straightness of the titanium alloy tube semi-finished product after straightening is less than 1 mm / m.

7. The method for processing a TA18 alloy tube according to claim 1, characterized in that: The heat treatment process in step S5 includes: annealing at a temperature range of 550° C. to 700° C. for 0.5 h to 3.0 h.

8. The method for processing a TA18 alloy tube according to claim 1, characterized in that: In step S6, the processing rate of the titanium alloy tube after the three-roll cold rolling process is in the range of 0.3-0.5, and the processing deformation value is in the range of 1.0-2.

0.

9. The method for processing a TA18 alloy tube according to claim 1, characterized in that: In step S8, the heat treatment process includes: annealing at a temperature within a range of 380° C. to 540° C. for 1.0 h to 3.0 h.

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