A method for preparing a high-performance large-size TC11 pipe by hot extrusion

Abstract

This invention discloses a method for hot extrusion preparation of high-performance, large-size TC11 tubes. The TC11 tubes produced are from the α+β two-phase region and lack complete β-phase grain boundaries. The method comprises: 1. Forging a TC11 ingot, followed by multiple upsetting and drawing forging processes to obtain a TC11 round bar; 2. Machining the outer diameter and boring the inner hole to obtain a TC11 ring billet; 3. Hot extrusion and straightening after double-sheathing to obtain a TC11 tube blank; 4. Sawing and pickling after cutting; 5. Annealing heat treatment; 6. Machining the inner and outer diameters to obtain a high-performance, large-size TC11 tube. This invention utilizes multiple upsetting and drawing forging processes to obtain a billet with good uniformity in microstructure and mechanical properties. Combined with hot extrusion and vertical annealing processes, it yields a TC11 tube blank with uniform microstructure and excellent room-temperature and high-temperature mechanical properties, achieving the preparation of high-performance, large-size TC11 tubes suitable for extreme working conditions such as aerospace, deep-sea engineering, and energy and chemical industries.

Description

Technical Field

[0001] This invention belongs to the field of pipe manufacturing technology, specifically relating to a method for hot extrusion manufacturing of high-performance, large-size TC11 pipes. Background Technology

[0002] Titanium alloy tubes are used in critical components of equipment in industries such as aviation, aerospace, petroleum, and chemical engineering. With the increasing size of aerospace equipment and advancements in deep-sea energy exploration technologies in recent years, higher demands have been placed on the dimensions and mechanical properties of titanium alloy tubes. Existing titanium alloy tubes are manufactured using methods such as extrusion, skew rolling, and Pilger rolling. Among these, hot extrusion, primarily involving triaxial compressive stress deformation, yields tubes with good metal density, resulting in superior internal and external surface quality, microstructure, and properties. The hot extrusion process is lengthy and involves numerous parameters, such as the extrusion ratio and cladding design, billet heating temperature, and extrusion speed selection. Each parameter significantly impacts the microstructure and properties of the finished tube. Due to the high investment in equipment and the complexity of process control, there is currently very little research on the preparation of large-size titanium alloy tubes. Patent CN113857786A discloses a hot extrusion method for preparing Φ76 / Φ61.2×1520mm TC4 titanium alloy tubes, with a tensile strength of 1121~1158MPa, a yield strength of 1036~1057MPa, and an elongation of 20~23%. Patent CN104232993A discloses a hot extrusion method for preparing TC11 titanium alloy tubes with an outer diameter of Φ115mm, a wall thickness of 25mm, and a length of 1600mm, achieving a room temperature tensile strength of 1105MPa, a yield strength of 1002MPa, an elongation of 18.5%, and an impact strength AKU2 of 42.8J. The titanium alloy tubes prepared using these methods exhibit good mechanical properties, but the maximum outer diameter is only 115mm. Although CN 103316941A discloses a hot extrusion method for large-diameter titanium alloy tubes with an outer diameter of Φ172mm, an inner diameter of Φ134mm, and a length of 4000mm, the mechanical properties of the tubes are unknown.

[0003] Therefore, how to prepare large-size titanium alloy tubes with excellent microstructure, room temperature and high temperature mechanical properties, and an outer diameter of more than 140 mm through hot extrusion is a key issue of current concern. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a method for hot extrusion preparation of high-performance, large-size TC11 tubes, addressing the shortcomings of the prior art. This method effectively controls the uniformity of the internal structure of the TC11 tube by employing multiple upsetting and forging processes, encased hot extrusion, and vertical annealing. This results in a TC11 tube blank with uniform microstructure and excellent room-temperature and high-temperature mechanical properties, achieving the preparation of high-performance, large-size TC11 tubes and solving the problem of preparing TC11 tubes with both large size and high performance in the prior art.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is as follows: a method for hot extrusion preparation of high-performance large-size TC11 tubes, characterized in that the TC11 tube has an outer diameter of Φ140mm~180mm, a wall thickness of 21mm~36mm, and a length of more than 2500mm. The TC11 tube has a microstructure produced by processing in the α+β two-phase region, without complete β original grain boundaries. The room temperature strength of the TC11 tube reaches 1098MPa~1128MPa, the elongation after fracture is 17.5%~19%, the room temperature impact AU2 reaches 33.2J~40.1J, the strength at 500℃ reaches 781MPa~820MPa, and the creep rupture performance at 500℃ / 640MPa is greater than 35h. The method includes the following steps: Step 1: Forge the TC11 ingot into a billet, and then perform multiple upsetting and precision forging processes to obtain a TC11 round bar. Step 2: Perform external turning and internal boring on the TC11 round bar obtained in Step 1 to obtain a TC11 ring blank; Step 3: The TC11 ring billet obtained in Step 2 is subjected to double-sleeving treatment, then hot extrusion and straightening to obtain the TC11 tube billet. Step 4: After cutting the TC11 tube blank obtained in Step 3, perform pickling. Step 5: The TC11 tube blank after pickling in Step 4 is subjected to annealing heat treatment in a vertical electric furnace; Step 6: Perform internal and external circumferential machining on the TC11 tube blank after annealing heat treatment in Step 5 to obtain high-performance large-size TC11 tube.

[0006] The above-mentioned method for hot extrusion preparation of high-performance large-size TC11 tube is characterized in that the multiple upsetting and forging process in step one is as follows: first, upsetting and forging are performed at 135℃~155℃ above the β phase transformation point and 40℃~60℃ above the β phase transformation point, then upsetting and forging are performed at 30℃~50℃ below the β phase transformation point, chamfering the edges to octagonal shape, and then rolling forging is performed.

[0007] The above-mentioned method for hot extrusion preparation of high-performance large-size TC11 tube is characterized in that the double-coating treatment in step three involves double-coating the inner and outer walls and end faces of the TC11 ring blank with iron / copper sheet.

[0008] The above-mentioned method for hot extrusion preparation of high-performance large-size TC11 tube is characterized in that the extrusion ratio λ in step three is greater than 5.0.

[0009] The above-mentioned method for hot extrusion preparation of high-performance large-size TC11 tube is characterized in that the heating temperature of hot extrusion in step three is 40℃~60℃ below the β phase transformation point, the holding time is 160min~200min, and the extrusion needle and extrusion die are preheated.

[0010] The above-mentioned method for hot extrusion preparation of high-performance large-size TC11 tube is characterized in that the hot extrusion speed in step three is 20mm / s to 50mm / s, the straightening is residual heat straightening, and the curvature after straightening is not greater than 3mm / m.

[0011] The above-described method for hot extrusion preparation of high-performance, large-size TC11 tubes is characterized in that step five involves vertical annealing for heat treatment. Typically, a double annealing heat treatment process is used.

[0012] Compared with the prior art, the present invention has the following advantages: 1. This invention obtains a billet with good uniformity in microstructure and mechanical properties through multiple upsetting, drawing and precision forging processes, and optimizes the process. This provides raw materials with uniform and dense internal structure for subsequent hot extrusion, laying the foundation for obtaining high-performance, large-size TC11 tubes.

[0013] 2. This invention ensures the smooth progress of the hot extrusion process by strictly limiting the process parameters such as heating temperature, holding time, extrusion speed and extrusion ratio of the TC11 ring blank after encapsulation, thereby obtaining a TC11 tube blank with uniform microstructure and excellent mechanical properties at room temperature and high temperature, and realizing the preparation of high-performance large-size TC11 tubes.

[0014] 3. The present invention adopts vertical annealing heat treatment, which avoids the stress introduced into the pipe by horizontal annealing. While ensuring that the required microstructure and properties are obtained, it improves the uniformity of the microstructure and mechanical properties of TC11 pipe.

[0015] 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

[0016] Figure 1 This is a cross-sectional microstructure image of the TC11 tube prepared in Example 1 of the present invention.

[0017] Figure 2This is a cross-sectional microstructure image of the TC11 tube prepared in Example 2 of the present invention. Detailed Implementation

[0018] Example 1 This embodiment includes the following steps: Step 1: A TC11 ingot with a diameter of Φ620mm (chemical composition: Ti-6.5Al-3.5Mo-1.8Zr-0.3Si, β-phase transformation temperature: 1005℃) is forged into a blank, followed by multiple upsetting and precision forging processes. The specific process for blank forging and multiple upsetting and precision forging is as follows: First, the TC11 ingot is heated to 1140℃~1160℃ and held for 4.2 hours before being removed from the furnace and subjected to two upsetting and two drawing processes. The deformation amount of a single upsetting process is... The ratio is 47%, the drawing-to-forging ratio is 1.69, then it is heated to 1045℃~1065℃ and held for 3.6h before being taken out of the furnace for two upsetting and two drawing. Then it is heated to 955℃~975℃ and held for 3.7h before being taken out of the furnace for three upsetting and three drawing in reverse direction. After being taken back to the furnace and held for 1.6h, it is upsetting and two drawing, chamfered to octagonal, then heated to 950℃±10℃ and held for 3.5h before being taken out of the furnace, drawn out and rolled into a round bar with a diameter of 360mm. Step 2: Perform external turning and internal boring on the TC11 round bar obtained in Step 1 to obtain a TC11 ring blank with an outer diameter of Φ347mm and an inner diameter of Φ110mm. Step 3: The inner and outer walls and end faces of the TC11 ring billet obtained in Step 2 are double-wrapped with iron / copper sheets. The iron sheet thickness is 0.8mm and the copper sheet thickness is 2.0mm. Then, it is placed in a box-type resistance furnace and heated at 945℃~965℃. The furnace is then filled at the desired temperature and held for 180 minutes. The extrusion needle and extrusion die are preheated at 350℃±10℃. The billet is then sent to the ingot loading machine by a robotic arm and loaded into the extrusion cylinder. Hot extrusion is started at a speed of 20mm / s~50mm / s with an extrusion ratio of λ=5.1. After hot extrusion, the billet is straightened using residual heat, and the curvature after straightening is no more than 3mm / m, thus obtaining the TC11 tube billet. Step 4: After cutting the TC11 tube blank obtained in Step 3, remove the copper and iron scale by pickling. During the pickling process, carefully observe the surface of the tube blank to prevent over-pickling. Step 5: The TC11 tube blank after pickling in Step 4 is hoisted and drilled, and then subjected to annealing heat treatment at 950℃±10℃ / air cooling and 530℃±10℃ / air cooling in a vertical resistance furnace. Step 6: Machin the inner and outer diameters and length of the TC11 tube blank after annealing heat treatment in Step 5 to obtain a TC11 tube with an outer diameter of Φ175mm, a wall thickness of 36mm, and a length of 2560mm.

[0019] The TC11 tubes prepared in this embodiment were subjected to microstructural and mechanical property testing. The microstructures of the head, middle, and tail sections were analyzed as follows: Figure 1 As shown, the microstructures of both groups of samples were generated from processing in the α+β two-phase region, without complete original β grain boundaries. The mechanical properties of the two groups of samples are shown in Table 1 below.

[0020] Table 1

[0021] Example 2 This embodiment includes the following steps: Step 1: A TC11 ingot with a diameter of Φ620mm (chemical composition: Ti-6.5Al-3.5Mo-1.8Zr-0.3Si, β-phase transformation temperature: 1005℃) is forged into a blank, followed by multiple upsetting and precision forging processes. The specific process for blank forging and multiple upsetting and precision forging is as follows: First, the TC11 ingot is heated to 1140℃~1160℃ and held for 4.5 hours before being removed from the furnace and subjected to two upsetting and two drawing processes. The deformation amount of a single upsetting process is... The forging ratio is 48%, the drawing ratio is 1.73, then it is heated to 1045℃~1065℃ and held for 3.8h before being taken out of the furnace for two upsetting and two drawing. Then it is heated to 955℃~975℃ and held for 3.6h before being taken out of the furnace for three upsetting and three drawing in reverse direction. After being taken back to the furnace and held for 1.7h, it is upsetting and two drawing, chamfered to octagonal, then heated to 950℃±10℃ and held for 3.7h before being taken out of the furnace, drawn out and rolled into a round bar with a diameter of 280mm. Step 2: Perform external turning and internal boring on the TC11 round bar obtained in Step 1 to obtain a TC11 ring blank with an outer diameter of Φ267mm and an inner diameter of Φ115mm. Step 3: The inner and outer walls and end faces of the TC11 ring billet obtained in Step 2 are double-wrapped with iron / copper sheets. The iron sheet thickness is 0.8mm and the copper sheet thickness is 1.0mm. Then, it is placed in a box-type resistance furnace and heated at 945℃~965℃. The furnace is then heated to the desired temperature and held for 160 minutes. The extrusion needle and extrusion die are preheated at 350℃±10℃. The billet is then sent to the ingot loading machine by a robotic arm and loaded into the extrusion cylinder. Hot extrusion is started at a speed of 20mm / s~50mm / s with an extrusion ratio of λ=5.7. After hot extrusion, the billet is straightened using residual heat, and the curvature after straightening is no more than 3mm / m, thus obtaining the TC11 tube billet. Step 4: After cutting the TC11 tube blank obtained in Step 3, remove the copper and iron scale by pickling. During the pickling process, carefully observe the surface of the tube blank to prevent over-pickling. Step 5: The TC11 tube blank after pickling in Step 4 is hoisted and drilled, and then subjected to annealing heat treatment at 950℃±10℃ / air cooling and 530℃±10℃ / air cooling in a vertical resistance furnace. Step 6: Machin the inner and outer diameters and length of the TC11 tube blank after annealing heat treatment in Step 5 to obtain a TC11 tube with an outer diameter of Φ144mm, a wall thickness of 21mm, and a length of 2500mm.

[0022] The TC11 tubes prepared in this embodiment were subjected to microstructural and mechanical property testing. The microstructures of the head, middle, and tail sections were analyzed as follows: Figure 2 As shown, the microstructures of both groups of samples were generated from processing in the α+β two-phase region, without complete original β grain boundaries. The mechanical properties of the two groups of samples are shown in Table 2 below.

[0023] Table 2

[0024] 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 method for hot extrusion preparation of high-performance, large-size TC11 tubes, characterized in that, The TC11 tube has an outer diameter of Φ140mm~180mm, a wall thickness of 21mm~36mm, and a length of over 2500mm. The TC11 tube has a microstructure produced by processing in the α+β two-phase region, without complete β original grain boundaries. The room temperature strength of the TC11 tube reaches 1098MPa~1128MPa, the elongation after fracture is 17.5%~19%, the room temperature impact AU2 reaches 33.2J~40.1J, the strength at 500℃ reaches 781MPa~820MPa, and the creep rupture performance at 500℃ / 640MPa is greater than 35h. The method includes the following steps: Step 1: Forge the TC11 ingot into a billet, and then perform multiple upsetting and precision forging processes to obtain a TC11 round bar. Step 2: Perform external turning and internal boring on the TC11 round bar obtained in Step 1 to obtain a TC11 ring blank; Step 3: The TC11 ring billet obtained in Step 2 is subjected to double-sleeving treatment, then hot extrusion and straightening to obtain the TC11 tube billet. Step 4: After cutting the TC11 tube blank obtained in Step 3, perform pickling. Step 5: The TC11 tube blank after pickling in Step 4 is subjected to annealing heat treatment in a vertical electric furnace; Step 6: Perform internal and external circumferential machining on the TC11 tube blank after annealing heat treatment in Step 5 to obtain high-performance large-size TC11 tube.

2. The method for hot extrusion preparation of high-performance large-size TC11 tubes according to claim 1, characterized in that, The process of multiple upsetting and fine forging described in step one is as follows: first, upsetting and forging are carried out at temperatures of 135℃~155℃ above the β phase transformation point and 40℃~60℃ above the β phase transformation point, then upsetting and forging are carried out at temperatures of 30℃~50℃ below the β phase transformation point, with chamfered edges, and then rounding forging is carried out.

3. The method for hot extrusion preparation of high-performance large-size TC11 tubes according to claim 1, characterized in that, The double-wrapping process described in step three involves applying iron / copper double wrapping to the inner and outer walls and end faces of the TC11 ring blank.

4. The method for hot extrusion preparation of high-performance large-size TC11 tubes according to claim 1, characterized in that, The extrusion ratio λ in step three is greater than 5.

0.

5. The method for hot extrusion preparation of high-performance large-size TC11 tubes according to claim 1, characterized in that, The heating temperature for hot extrusion in step three is 40°C to 60°C below the β phase transformation point, and the holding time is 160 min to 200 min. The extrusion needle and extrusion die are also preheated.

6. The method for hot extrusion preparation of high-performance large-size TC11 tubes according to claim 1, characterized in that, The hot extrusion speed in step three is 20mm / s to 50mm / s, the straightening is residual heat straightening, and the curvature after straightening is no more than 3mm / m.

7. The method for hot extrusion preparation of high-performance large-size TC11 tubes according to claim 1, characterized in that, In step five, vertical annealing is used for annealing heat treatment.

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