A short-process manufacturing method of high-performance small-caliber TA18 titanium pipe

Abstract

The application discloses a short-process manufacturing method of high-performance small-caliber TA18 titanium pipe, and relates to the field of pipe manufacturing, in particular to the field of high-performance small-caliber TA18 titanium pipe manufacturing. The method comprises the following steps: firstly, polishing the outer surface of TA18 titanium alloy extruded pipe and boring the inner hole to obtain a rolled pipe blank; secondly, adopting a pilger high-speed rolling mill to cold roll the rolled pipe blank for not more than two passes, and vacuum annealing the pipe blank after each pass of cold rolling to obtain the high-performance small-caliber TA18 titanium pipe. The application realizes the combination of forging and rolling by synergistically controlling the deformation amount and deformation rate and other process parameter windows in the cold rolling process, so that the pipe blank organization is fully broken, and new fine grains are generated by dynamic recrystallization, the dynamic balance among alloy large deformation, cold work hardening and grain refinement is realized, the short-process preparation of the high-strength and high-plasticity small-caliber TA18 titanium alloy seamless pipe is realized, the surface quality is high, the yield is high, the manufacturing period is short, and the method is suitable for large-batch industrial production and manufacturing.

Description

Technical Field

[0001] This invention belongs to the field of titanium and titanium alloy processing technology, specifically relating to a short-process manufacturing method for high-performance small-diameter TA18 titanium pipes. Background Technology

[0002] With the rapid increase in domestic demand for advanced aircraft engine manufacturing, the use of TA18 (Ti-3Al-2.5V) titanium alloy high-performance small-diameter (Ф6mm~Ф18mm) seamless tubing, the preferred choice for high-pressure fuel piping systems in multiple engine models, has also increased significantly. TA18, a near-α type medium-strength titanium alloy that cannot be heat-treated for strengthening, typically meets the tensile strength requirement of not less than 620MPa in the GJB3423A standard. However, high-pressure fuel lines for aero-engines must meet the 900MPa strength requirement of AMS 4946 Standard Category I, which is comparable to the strength of the typical α+β type titanium alloy Ti-6Al-4V, and even superior in ductility. Currently, China is capable of mass-producing TA18 small-diameter tubing that meets AMS 4946 Standard Category I, but it suffers from outdated manufacturing methods, long production processes, low yield and product quality, and poor batch stability, resulting in high prices, long delivery cycles, and difficulties in widespread adoption.

[0003] The minimum diameter used in the production of high-quality TA18 pipes in China is Φ. 外 >32mm extruded tubes or forged bar mill tubes are used as rolling billets, and finished tubes are produced using the traditional process of "two-roll billet opening + multi-roll finishing rolling" in multiple passes. This method selects high-quality billets with sufficient deformation in the two-phase region. However, due to the limited deformation capacity of the rolling mill equipment, a large deformation amount (30%~40%) cannot be achieved in a single pass during finishing rolling. This results in 5~10 cumulative rolling passes being required when producing small-diameter tubes. The increase in passes leads to an increase in the accumulation of defects on the inner and outer surfaces of the titanium tube and a decrease in the pass rate of flaw detection. At the same time, the small deformation degree of single-pass finishing rolling (≤45%) is not conducive to grain refinement. The average size of recrystallized grains in the rolled finished tubes is basically maintained at grade 11~12.5 (about 4.7μm~7.5μm) of the GB / T 6394-2017 standard. Its room temperature mechanical properties are slightly higher than the lower limit of the Class I index of the AMS 4946 standard, and do not provide much room for performance control of the tubes.

[0004] The classic Hall-Petch relationship indicates that fine-grained strengthening is an effective method to achieve a combined improvement in strength and plasticity of high-performance metal tubes, while the grain size during cold working is usually determined by the degree of cold deformation. Existing two-roll mills generally employ an eccentric gear balancing method, which, due to factors such as poor dynamic balance and short working cone length, cannot improve the unit limit deformation capacity and process efficiency of the rolled metal. This leads to problems such as tube sticking or even cracking, and mill seizure when single-pass rolling deformation is large. The new Pilger high-speed mill introduces the concept of milling, employing a compensating counterweight and annular bore type, and a synchronous double-crank shaft balancing method that replaces the movable stand with a fixed stand. This greatly optimizes the rolling effect of forging and rolling combined, enabling the equipment to achieve nearly twice the maximum speed and deformation capacity of conventional mills, improving production efficiency and pointing to a new way to simplify the process.

[0005] Titanium alloys have a close-packed hexagonal structure at room temperature, resulting in few slip systems that can participate in deformation, making them difficult-to-deform metals. TA18 alloy, in particular, exhibits high strength, high strain hardening rate, and significant springback during cold working, making it highly prone to cracking even with conventional cold rolling. Currently, research on the use of two-roll Pilger high-speed rolling mills for high-strength, high-ductility titanium alloy tubes is lacking. Therefore, even with advanced Pilger rolling mills, the primary challenge in promoting the use of Pilger high-speed rolling mills for high-strength, high-ductility titanium alloy tube production lies in how to leverage the advantages of these mills through optimized process parameters to prevent cracking during room temperature rolling with deformation amounts exceeding twice that of conventional mills.

[0006] Although invention patent CN117548520A specifies that the tube blank used should have a fine grain size of ≤5μm and a single-pass rolling deformation of ≥70%, the performance of the prepared TA18 titanium alloy finished tube remains at a medium-strength level with a tensile strength of 690MPa to 695MPa. Furthermore, obtaining finished tubes with an outer diameter of Φ10mm or larger still requires five "cold rolling / drawing" passes. The relevant process parameters in this patent are not applicable to the production of small-diameter 900MPa grade TA18 titanium alloy tubes. Authorized invention patent CN113441553B uses a two-roll medium-speed rolling method to prepare seamless steel tubes with an outer diameter of Φ28mm to Φ40mm. The advantage of this method lies in achieving high-precision control of the steel tube's dimensions and surface, rather than control over its microstructure and properties. It is difficult to use this method to guide the rolling of difficult-to-deform titanium alloys with a close-packed hexagonal structure.

[0007] In summary, there is currently no efficient and short-process technology in China for the mass production of high-quality small-diameter TA18 titanium alloy tubing for 900MPa-class aero-engines. Therefore, actively developing new processes for the production and processing of high-performance small-diameter TA18 titanium alloy tubing, while maintaining its excellent performance, to reduce production costs and improve efficiency, is of great significance and has broad application prospects for promoting the performance of domestically produced aero-engines and achieving complete import substitution. Summary of the Invention

[0008] The technical problem this invention aims to solve is to address the shortcomings of the prior art by providing a short-process manufacturing method for high-performance small-diameter TA18 titanium tubes. This method achieves a combination of forging and rolling by synergistically controlling process parameters such as deformation amount and deformation rate during cold rolling. This results in thorough fragmentation of the tube blank structure and the generation of dynamically recrystallized fine grains, achieving a dynamic balance between large alloy deformation, cold work hardening, and grain refinement. The resulting high-performance small-diameter TA18 titanium alloy tubes exhibit excellent strength-plasticity matching, high surface quality, high yield, and short manufacturing cycle, solving the problem of the lack of an efficient short-process method for manufacturing high-performance small-diameter TA18 titanium tubes in the prior art.

[0009] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a short-process manufacturing method for high-performance small-diameter TA18 titanium pipes, characterized in that the method includes the following steps:

[0010] Step 1: Polish the outer surface and bore the inner hole of the TA18 titanium alloy extruded tube to obtain the rolled tube blank;

[0011] Step 2: The rolled tube blank obtained in Step 1 is cold rolled in no more than 2 passes using a Pilger high-speed rolling mill, and the tube blank after each cold rolling pass is vacuum annealed to obtain high-performance small-diameter TA18 titanium tube. During the cold rolling process, the deformation rate of each pass is controlled at 60% to 70%, the rolling speed is 105 to 115 times / minute, and the feed rate is 0.8 mm / pass to 1.2 mm / pass.

[0012] The aforementioned short-process manufacturing method for high-performance small-diameter TA18 titanium tubes is characterized in that the outer diameter × wall thickness × length of the TA18 titanium alloy extruded tube in step one is (16mm~25mm) × (3mm~4.5mm) × (≥1500mm). This invention uses this specification of TA18 titanium alloy extruded tube as the rolling blank, which avoids the accumulation of rolling defects caused by using the same specification of rolled tube as the blank. This not only reduces rolling inheritance but also significantly improves the pass rate of flaw detection in the titanium tube products. Furthermore, the length of small-diameter titanium tube blanks prepared by machining TA18 titanium alloy bars is typically no more than 500mm, and as the length increases, the uniformity of the tube blank wall thickness decreases, leading to the inability to automatically feed the tube blank during rolling, reduced production efficiency, and also resulting in limited length and easy wall deviation in the finished titanium tubes, further reducing the yield. This invention effectively overcomes these problems by using TA18 titanium alloy extruded tubes as the rolling blank.

[0013] The above-mentioned short-process manufacturing method for high-performance small-diameter TA18 titanium tubes is characterized in that the microstructure of the TA18 titanium alloy extruded tube in step one is an equiaxed structure, a basket webbing structure, a Widmanstätten structure, or a bimodal structure.

[0014] The above-mentioned short-process manufacturing method for high-performance small-diameter TA18 titanium pipe is characterized in that the high-performance small-diameter TA18 titanium pipe in step two has a room temperature tensile strength of not less than 900 MPa and an elongation after fracture of not less than 12%.

[0015] As a difficult-to-deform alloy with a high strain hardening rate, TA18 can be cold-deformed by controlling the above-mentioned reasonable processing deformation speed and degree. This prevents insufficient grain breakage and failure to achieve fine grain strengthening when the deformation is too small, and also prevents cracking defects caused by dislocation pile-up when the deformation is too large or too fast, thus ensuring the smooth progress of the cold rolling process.

[0016] The above-mentioned short-process manufacturing method for high-performance small-diameter TA18 titanium pipe is characterized in that the average grain size of the recrystallized high-performance small-diameter TA18 titanium pipe in step two meets level 14 of GB / T 6394-2017 "Method for Determination of Average Grain Size of Metals".

[0017] The above-mentioned short-process manufacturing method for high-performance small-diameter TA18 titanium tubes is characterized in that the outer diameter of the high-performance small-diameter TA18 titanium tubes in step two is 6mm to 18mm.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] 1. This invention achieves a combination of forging and rolling by synergistically controlling process parameter windows such as deformation amount and deformation rate during cold rolling. This ensures that the metal in the deformed part flows fully and participates in the deformation. While the billet structure is fully broken, dynamic recrystallization of new fine grains is generated through rolling temperature rise. This achieves a dynamic balance between large deformation of the alloy, cold work hardening, and grain refinement, ensuring that the microstructure and mechanical properties of TA18 titanium pipe are uniform and consistent, improving the strength of TA18 titanium pipe, and obtaining high-performance small-diameter TA18 titanium alloy pipe with good strength and plasticity matching.

[0020] 2. By controlling the cold rolling process to no more than two passes, this invention effectively reduces the rolling and related degreasing, pickling, and annealing processes while ensuring the production of small-diameter TA18 titanium alloy tubes. This simplifies the conventional small-diameter titanium tube production process by more than half, significantly shortens the production cycle, and increases the tube yield by more than 30%, thus achieving a short-process preparation of high-strength, plastic, small-diameter TA18 titanium alloy seamless tubes.

[0021] 3. This invention uses small-sized extruded tube blanks with an outer diameter of less than 25mm as raw materials, and has low requirements for the initial microstructure properties of the selected extruded tube blanks. Equiaxed structure, basket webbing structure, Widmanstätten structure and bimorphic structure all meet the requirements for use, thus expanding the scope of application of the method of this invention.

[0022] 4. The small-diameter TA18 titanium tube prepared by this invention has good comprehensive properties with a tensile strength of not less than 900MPa and an elongation after fracture of not less than 12%. Its strength is increased by 300MPa, and its strength and plasticity reach the level of Ti-6Al-4V. It also has high surface quality, high yield, and short manufacturing cycle, making it suitable for mass industrial production processes.

[0023] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0024] Figure 1 The image shows the transverse microstructure (OM) of the TA18 titanium alloy extruded tube with a specification of Ф25mm×4.5mm selected for Example 1 of this invention.

[0025] Figure 2 EBSD image of the transverse microstructure of a TA18 titanium tube with dimensions of Ф18mm×1.5mm prepared in Example 1 of this invention.

[0026] Figure 3 The image shows the transverse microstructure (OM) of the TA18 titanium alloy extruded tube with dimensions of Ф25mm×4.5mm selected for Example 2 of this invention.

[0027] Figure 4 EBSD image of the transverse microstructure of a TA18 titanium tube with dimensions of Ф10mm×1.2mm prepared in Example 2 of this invention.

[0028] Figure 5 The image shows the transverse microstructure (OM) of the TA18 titanium alloy extruded tube blank with dimensions of Ф20mm×5mm selected in Example 3 of this invention.

[0029] Figure 6 The image shows the transverse microstructure of the TA18 titanium tube with dimensions of Ф8mm×1mm prepared in Example 3 of this invention.

[0030] Figure 7 The image shows the transverse microstructure (OM) of the TA18 titanium alloy extruded tube blank with dimensions of Ф16mm×3mm selected in Example 4 of this invention.

[0031] Figure 8 EBSD image of the transverse microstructure of the TA18 titanium tube with dimensions of Ф6mm×0.5mm prepared in Example 4 of this invention. Detailed Implementation

[0032] Example 1

[0033] This embodiment includes the following steps:

[0034] Step 1: Select TA18 titanium alloy extruded tubes with an outer diameter × wall thickness × length of Ф25mm × 4.5mm × 2200mm that meet the chemical composition requirements of GB / T 3620.1-2016 "Titanium and Titanium Alloy Grades and Chemical Composition". Polish the outer surface of the TA18 titanium alloy extruded tubes and bore the inner hole to a size of Ф24.5mm × 3.9mm to obtain the rolled tube blank.

[0035] Step 2: The rolled tube blank obtained in Step 1 is cold rolled in one pass using a KPW25 rolling mill to a specification of outer diameter × wall thickness of Ф18mm × 1.5mm. During the cold rolling process, the deformation rate per pass is controlled at 69%, the rolling speed is 105 times / minute, and the feed rate is 0.8mm / pass. Then, the cold-rolled tube is degreased and pickled in sequence, and then vacuum heat treated at 590℃ / 1h to obtain TA18 titanium tube.

[0036] Testing showed that the TA18 titanium tubing prepared in this embodiment has a room temperature tensile strength Rm = 953 MPa and a yield strength Rp. 0.2 =799MPa, elongation after fracture A =16.5%.

[0037] Figure 1 The OM image shows the transverse microstructure of the TA18 titanium alloy extruded tube with a specification of Ф25mm×4.5mm selected in this embodiment. Figure 1 It can be seen that the TA18 titanium alloy extruded tube has a dual-state structure.

[0038] Figure 2 EBSD image of the transverse microstructure of the TA18 titanium tube with dimensions of Ф18mm × 1.5mm prepared in this embodiment. Figure 2 It can be seen that the average grain size of the TA18 titanium pipe is less than 2.8 μm, which meets the grade 14 standard of GB / T 6394-2017 "Method for Determination of Average Grain Size of Metals".

[0039] Example 2

[0040] This embodiment includes the following steps:

[0041] Step 1: Select TA18 titanium alloy extruded tubes with an outer diameter × wall thickness × length of Ф25mm × 4.5mm × 1800mm that meet the chemical composition requirements of GB / T 3620.1-2016 "Titanium and Titanium Alloy Grades and Chemical Composition". Polish the outer surface of the TA18 titanium alloy extruded tubes and bore the inner hole to a size of Ф24.5mm × 3.75mm to obtain the rolled tube blank.

[0042] Step 2: Using a KPW25 rolling mill, the rolled tube blank obtained in Step 1 is cold-rolled in one pass to a specification of outer diameter × wall thickness of Ф16mm × 2.2mm. During the cold rolling process, the deformation rate per pass is controlled at 61%, the rolling speed is 110 times / minute, and the feed rate is 1.2mm / pass. Then, the cold-rolled tube is subjected to degreasing and pickling treatments, followed by vacuum heat treatment at 640℃ / 1h. Using a KPW25 rolling mill, the heat-treated tube is cold-rolled in one pass to a specification of outer diameter × wall thickness of Ф10mm × 1.2mm. During the cold rolling process, the deformation rate per pass is controlled at 68%, the rolling speed is 105 times / minute, and the feed rate is 1.2mm / pass. Then, the cold-rolled tube is subjected to degreasing and pickling treatments, followed by vacuum heat treatment at 600℃ / 1h to obtain TA18 titanium tube.

[0043] Testing revealed that the TA18 titanium tubing prepared in this embodiment has a room temperature tensile strength Rm = 997 MPa and a yield strength Rp. 0.2 =905MPa, elongation after fracture A =15%.

[0044] Figure 3 The OM image shows the transverse microstructure of the TA18 titanium alloy extruded tube with a specification of Ф25mm×4.5mm selected in this embodiment. Figure 3 It can be seen that the TA18 titanium alloy extruded tube has Widmanstätten structure.

[0045] Figure 4 EBSD image of the transverse microstructure of a TA18 titanium tube with dimensions of Ф10mm × 1.2mm prepared in this embodiment. Figure 4 It can be seen that the average grain size of the TA18 titanium pipe is less than 2.8 μm, which meets the grade 14 standard of GB / T 6394-2017 "Method for Determination of Average Grain Size of Metals".

[0046] Example 3

[0047] This embodiment includes the following steps:

[0048] Step 1: Select TA18 titanium alloy extruded tubes with an outer diameter × wall thickness × length of Ф20mm × 5mm × 2000mm that meet the chemical composition requirements of GB / T 3620.1-2016 "Titanium and Titanium Alloy Grades and Chemical Composition". Polish the outer surface of the TA18 titanium alloy extruded tubes and bore the inner hole to a size of Ф19.5mm × 4.5mm to obtain the rolled tube blank.

[0049] Step 2: Using a KPW25 rolling mill, the rolled tube blank obtained in Step 1 is cold-rolled in one pass to a specification of outer diameter × wall thickness of Ф12.5mm × 2.3mm. During the cold rolling process, the deformation rate per pass is controlled at 65%, the rolling speed is 110 times / minute, and the feed rate is 1.0mm / pass. Then, the cold-rolled tube is subjected to degreasing, pickling, and vacuum heat treatment at 620℃ / 1h. Using a KPW18 rolling mill, the heat-treated tube is cold-rolled in one pass to a specification of outer diameter × wall thickness of Ф8mm × 1mm. During the cold rolling process, the deformation rate per pass is controlled at 70%, the rolling speed is 110 times / minute, and the feed rate is 0.8mm / pass. Then, the cold-rolled tube is subjected to degreasing, pickling, and vacuum heat treatment at 600℃ / 1h to obtain TA18 titanium tube.

[0050] Testing revealed that the TA18 titanium tubing prepared in this embodiment has a room temperature tensile strength Rm = 1017 MPa and a yield strength Rp. 0.2 =911MPa, elongation after fracture A =13%.

[0051] Figure 5 The image shows the transverse microstructure (OM) of the TA18 titanium alloy extruded tube with dimensions of Ф20mm×5mm selected in this embodiment. Figure 5 It can be seen that the TA18 titanium alloy extruded tube has an equiaxed structure.

[0052] Figure 6 The EBSD image shows the transverse microstructure of a TA18 titanium tube with dimensions of Ф8mm × 1mm prepared in this embodiment. Figure 6 It can be seen that the average grain size of the TA18 titanium pipe is less than 2.8 μm, which meets the grade 14 standard of GB / T 6394-2017 "Method for Determination of Average Grain Size of Metals".

[0053] Example 4

[0054] This embodiment includes the following steps:

[0055] Step 1: Select TA18 titanium alloy extruded tubes with an outer diameter × wall thickness × length of Ф16mm × 3mm × 1500mm that meet the chemical composition requirements of GB / T 3620.1-2016 "Titanium and Titanium Alloy Grades and Chemical Composition". Polish the outer surface of the TA18 titanium alloy extruded tubes and bore the inner hole to a size of Ф15.5mm × 2.45mm to obtain the rolled tube blank.

[0056] Step 2: Using a KPW18 rolling mill, the rolled tube blank obtained in Step 1 is cold-rolled in one pass to a specification of outer diameter × wall thickness of Ф9mm × 1.8mm. During the cold rolling process, the deformation rate per pass is controlled at 70%, the rolling speed is 110 times / minute, and the feed rate is 0.8mm / pass. Then, the cold-rolled tube is subjected to degreasing and pickling treatments, followed by vacuum heat treatment at 620℃ / 1h. Using a KPW18 rolling mill, the heat-treated tube is cold-rolled in one pass to a specification of outer diameter × wall thickness of Ф6mm × 0.5mm. During the cold rolling process, the deformation rate per pass is controlled at 70%, the rolling speed is 105 times / minute, and the feed rate is 0.8mm / pass. Then, the cold-rolled tube is subjected to degreasing and pickling treatments, followed by vacuum heat treatment at 600℃ / 1h to obtain TA18 titanium tube.

[0057] Testing revealed that the TA18 titanium tubing prepared in this embodiment has a room temperature tensile strength Rm = 929 MPa and a yield strength Rp. 0.2 =832MPa, elongation after fracture A =15.5%.

[0058] Figure 7 The OM image shows the transverse microstructure of the TA18 titanium alloy extruded tube with a specification of Ф16mm×3mm selected in this embodiment. Figure 7 It can be seen that the TA18 titanium alloy extruded tube has Widmanstätten structure.

[0059] Figure 8 The image shows the transverse microstructure EBSD of a TA18 titanium tube with dimensions of Ф6mm × 0.5mm prepared in this embodiment. Figure 8 It can be seen that the average grain size of the TA18 titanium pipe is less than 2.8 μm, which meets the grade 14 standard of GB / T 6394-2017 "Method for Determination of Average Grain Size of Metals".

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A short-process manufacturing method for high-performance small-diameter TA18 titanium pipes, characterized in that, The method includes the following steps: Step 1: Polish the outer surface and bore the inner hole of the TA18 titanium alloy extruded tube to obtain the rolled tube blank; Step 2: The rolled tube blank obtained in Step 1 is cold rolled in no more than 2 passes using a Pilger high-speed rolling mill, and the tube blank after each cold rolling pass is vacuum annealed to obtain high-performance small-diameter TA18 titanium tube. During the cold rolling process, the deformation rate of each pass is controlled at 60% to 70%, the rolling speed is 105 to 115 times / minute, and the feed rate is 0.8 mm / pass to 1.2 mm / pass.

2. The short-process manufacturing method for high-performance small-diameter TA18 titanium pipe according to claim 1, characterized in that, The specifications of the TA18 titanium alloy extruded tube mentioned in step one are outer diameter × wall thickness × length of (16mm~25mm) × (3mm~4.5mm) × (≥1500mm).

3. The short-process manufacturing method for high-performance small-diameter TA18 titanium pipe according to claim 1, characterized in that, The microstructure of the TA18 titanium alloy extruded tube described in step one is equiaxed, basket webbing, Widmanstätten, or bimodal.

4. The short-process manufacturing method for high-performance small-diameter TA18 titanium tubing according to claim 1, characterized in that, The high-performance small-diameter TA18 titanium pipe described in step two has a room temperature tensile strength of not less than 900 MPa and an elongation after fracture of not less than 12%.

5. The short-process manufacturing method for high-performance small-diameter TA18 titanium tubing according to claim 1, characterized in that, The average grain size of the recrystallized high-performance small-diameter TA18 titanium pipe described in step two meets the 14th grade of GB / T 6394-2017 "Method for Determination of Average Grain Size of Metals".

6. The short-process manufacturing method for high-performance small-diameter TA18 titanium pipe according to claim 1, characterized in that, The high-performance small-diameter TA18 titanium tube mentioned in step two has an outer diameter of 6mm to 18mm.

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