A method for manufacturing large-diameter, thin-walled TA31 titanium alloy seamless tubes

Abstract

This invention relates to the field of metal pipe manufacturing technology, and discloses a method for manufacturing large-diameter, thin-walled TA31 titanium alloy seamless pipes, comprising the following steps: mixing sponge titanium and an intermediate alloy and then melting to obtain a TA31 ingot; forging the ingot into a titanium billet and processing it into a bright rod; and detecting the β transformation temperature T of the bright rod. β Heat the light bar to T β A thick-walled tube blank is obtained by piercing once at 30-80 ℃; the thick-walled tube blank is then heated to T. β The thin-walled tube blank is obtained by extending and piercing at 20-50 °C. This invention combines a single β-region large-wall-thickness piercing with a single α-β two-phase region large-deformation extension piercing, which can produce tube blanks with superior microstructure and properties, providing good initial conditions for subsequent processing. It not only significantly improves product performance but also has high production efficiency and added value, resulting in good social and economic benefits.

Description

Technical Field

[0001] This invention relates to the field of metal pipe manufacturing technology, and in particular to a method for manufacturing large-diameter, thin-walled TA31 titanium alloy seamless pipes. Background Technology

[0002] With the increasing demand for high-performance materials in fields such as marine, aerospace, and new energy, titanium alloy tubes with excellent comprehensive properties have gradually become a research and development focus. Among them, TA31 titanium alloy material, due to its high strength, good toughness, and excellent corrosion resistance, shows good comprehensive performance potential and has broad application prospects in the field of high-end equipment.

[0003] Currently, the main manufacturing process for TA31 titanium alloy seamless tubes is a combination of extrusion or hot piercing billet forming and rolling. However, existing processes are mostly concentrated on small-diameter tubes below Φ100 mm. For large-diameter tubes, especially thin-walled tubes with high quality requirements, relevant manufacturing processes are still relatively lacking, making it difficult to meet the demand for large-specification, high-performance tubes in high-end fields.

[0004] Specifically, while the hot extrusion combined with rolling process has the advantages of high production efficiency and more uniform structure, it requires large equipment investment, strict temperature control, and is difficult to produce large-diameter thin-walled pipes. The hot piercing combined with rolling process can produce products with high dimensional accuracy and good surface quality, but it has more steps, relatively low yield, and limited production efficiency.

[0005] Therefore, the preparation of medium- and high-strength large-diameter seamless pipes, especially large-diameter thin-walled TA31 titanium alloy seamless pipes, still faces technical challenges such as limited preparation processes, difficult forming, low yield, and difficulty in balancing microstructure and mechanical properties. There is an urgent need to develop a new preparation process that can balance forming efficiency, microstructure uniformity, and mechanical properties in order to overcome the bottlenecks of existing technologies. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for manufacturing large-diameter, thin-walled TA31 titanium alloy seamless tubes.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for manufacturing large-diameter, thin-walled TA31 titanium alloy seamless tubing includes the following steps:

[0009] Step 1: After mixing sponge titanium and intermediate alloy, smelt to obtain TA31 ingot. Forge the ingot into titanium billet and process it into a bright rod. Measure the β transformation temperature T of the bright rod. β ;

[0010] Step 2: Heat the light bar to T β A thick-walled tube blank is obtained by piercing once at 30-80 ℃ (i.e., β-zone piercing).

[0011] Step 3: Heat the thick-walled tube blank to T β The thin-walled tube blank is prepared by extending the perforation (i.e., extending the perforation in the α-β two-phase region) at 20-50 ℃.

[0012] Step 4: After intermediate recrystallization heat treatment, the thin-walled tube blank is subjected to one cold rolling.

[0013] Step 5: After the first cold-rolled tube blank undergoes intermediate recrystallization heat treatment, it is then subjected to a second cold rolling.

[0014] Step 6: Vacuum heat treatment is performed on the tube blank after the second cold rolling to obtain the large-diameter thin-walled TA31 titanium alloy seamless tube.

[0015] Preferably, the intermediate alloy comprises Al, Nb, Zr and Mo; the smelting composition of TA31, by mass percentage, comprises: Al 5.5-6.5%, Nb 2.5-3.5%, Zr 1.5-2.5%, Mo 0.6-1.5%, with the balance being Ti.

[0016] Preferably, in step 2, the primary piercing is performed using a three-roll skew rolling mill with a compression ratio of 12-18% and a piercing diameter-to-thickness ratio of 5-10:1.

[0017] Preferably, in step 3, the piercing is performed using a three-roll skew rolling mill with a compression ratio of 10-15% and a maximum piercing diameter-to-thickness ratio of 30:1.

[0018] Preferably, the deformation amount of the first cold rolling is 15-35%, and the Q value is 1.1-1.7; the deformation amount of the second cold rolling is 10-30%, and the Q value is 1-1.5, where Q value is the ratio of axial elongation coefficient to radial compression coefficient during rolling.

[0019] Preferably, in steps 4 and 5, the intermediate recrystallization heat treatment is performed at a temperature of 800-950 ℃ for 2 hours, and the cooling method is air cooling.

[0020] Preferably, in step 6, the temperature of the vacuum heat treatment is 680-750 ℃, and the holding time is 0.5-4 h.

[0021] Preferably, the outer diameter of the large-diameter thin-walled TA31 titanium alloy seamless tube obtained in step 6 is Φ114-273 mm, the wall thickness is 3-14 mm, and the length is 3-6 m.

[0022] Preferably, in step 1, the β transition temperature T of the optical rod is determined using metallographic methods.β .

[0023] This invention combines a single β-region thick-walled piercing with a single α-β two-phase region large deformation extension piercing, which can produce tube blanks with superior microstructure and properties, providing good initial conditions for subsequent processing.

[0024] Secondly, this invention fully utilizes the allotropic transformation characteristic of titanium alloys. During a single large-wall-thickness piercing in the β region, the material exhibits excellent processing properties, facilitating large deformation forming and obtaining a stable tube blank structure. Subsequently, extended piercing is performed in the α-β two-phase region. By controlling the heating temperature, the microstructure after the first piercing does not undergo significant changes. Simultaneously, the large wall-reduction piercing effectively regulates the microstructure of the tube blank, thereby obtaining a tube blank with a more uniform microstructure and superior performance.

[0025] Furthermore, based on the above-mentioned piercing process, this invention combines two cold rolling processes and intermediate recrystallization heat treatment to achieve coordinated control between plastic deformation and microstructure recovery of the material, thereby gradually optimizing the microstructure and dimensional accuracy of the tube; finally, the microstructure and properties of the tube are adjusted through vacuum heat treatment of the finished product to achieve the ideal performance state.

[0026] Through the above process combination, the large-diameter thin-walled TA31 titanium alloy seamless tube obtained by the present invention has the characteristics of high strength, good toughness, excellent internal and external surface quality, and uniform structure; at the same time, the tube has good corrosion resistance and can meet the needs of marine engineering, shipbuilding and other fields for high-performance materials.

[0027] Furthermore, by employing a combined process of "hot piercing, extended piercing, and cold rolling," this invention avoids the traditional methods of drilling through holes and then piercing, as well as extrusion billet preparation. This not only improves the yield and production efficiency but also achieves a synergistic improvement in microstructure homogenization and mechanical property optimization, thus providing a feasible technical path for the efficient preparation of large-diameter thin-walled titanium alloy seamless tubes.

[0028] In summary, this invention not only significantly improves product performance but also has high production efficiency and added value, resulting in good social and economic benefits. Attached Figure Description

[0029] Figure 1 The image shows the microstructure of the tube blank after one piercing.

[0030] Figure 2 This is a microstructure diagram of the tube after two cold rolling processes. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0032] A method for manufacturing large-diameter, thin-walled TA31 titanium alloy seamless tubing includes the following steps:

[0033] Step 1: After mixing sponge titanium and intermediate alloy, smelt to obtain TA31 ingot. Forge the ingot into titanium billet and process it into a bright rod. Measure the β transformation temperature T of the bright rod. β ;

[0034] Step 2: Heat the light bar to T β A thick-walled tube blank is obtained by piercing once at 30-80 ℃.

[0035] Step 3: Heat the thick-walled tube blank to T β The tube blank is produced by stretching and piercing at 20-50 ℃.

[0036] Step 4: After intermediate recrystallization heat treatment, the thin-walled tube blank is subjected to one cold rolling.

[0037] Step 5: After the first cold-rolled tube blank undergoes intermediate recrystallization heat treatment, it is then subjected to a second cold rolling.

[0038] Step 6: Vacuum heat treatment is performed on the tube blank after the second cold rolling to obtain the large-diameter thin-walled TA31 titanium alloy seamless tube.

[0039] In a preferred embodiment of the present invention, the intermediate alloy comprises Al, Nb, Zr and Mo; the smelting composition of TA31, by mass percentage, comprises: Al 5.5-6.5%, Nb 2.5-3.5%, Zr 1.5-2.5%, Mo 0.6-1.5%, with the balance being Ti.

[0040] In a preferred embodiment of the present invention, step 1, the fabrication process of the light rod includes:

[0041] The ingot is heated in an electric resistance furnace at a temperature of 1050-1120 ℃. The heating temperature of the electric furnace is monitored by thermocouples and temperature measuring guns to ensure uniform heating of the billet.

[0042] A 2000 T high-speed forging machine is used to perform three-stage forging and three-stage pulling of the ingot, with the direction of each forging and pulling reversed, and the forging ratio is 1.5-2;

[0043] The billet after upsetting is milled and ground to remove surface defects;

[0044] The processed blank is sawn;

[0045] The billet is heated in an electric resistance furnace at a temperature of 1000-1080 ℃. The heating temperature of the electric furnace is monitored by thermocouples and temperature measuring guns to ensure uniform heating of the billet.

[0046] The billet was initially deformed using a 2000-ton high-speed forging mill, with a total deformation of 40-70%.

[0047] The billet is heated in an electric resistance furnace at a temperature of 950-1020 ℃. The heating temperature of the electric furnace is monitored by thermocouples and temperature measuring guns to ensure uniform heating of the billet.

[0048] The deformed bar was forged using an electro-hydraulic hammer.

[0049] The bristles are sawn and cut into smaller pieces;

[0050] The bark is peeled to obtain a smooth bar for perforation.

[0051] In a preferred embodiment of the present invention, in step 2, the light rod is heated by a resistance furnace, and the heating temperature of the furnace is monitored by a thermocouple and a temperature measuring gun to ensure that the light rod is heated evenly.

[0052] In a preferred embodiment of the present invention, in step 2, the primary piercing is performed using a three-roll skew rolling mill with a compression ratio of 12-18% and a piercing diameter-to-thickness ratio of 5-10:1.

[0053] As a preferred embodiment of the present invention, before the first piercing in step 2, the three-roll skew rolling mill is adjusted as follows: the rolling line coincides with or is 2-3 mm lower than the piercing center line; the horizontal projection of the roll center line is parallel to the rolling line; and the inclination angle of the rolls relative to the piercing center line is equal.

[0054] In a preferred embodiment of the present invention, the mandrel material used in the first piercing in step 2 is H13, the mandrel extends 50-85 mm beyond the compression belt of the roll, the mandrel cooling water pressure is controlled at 0.3-0.7 MPa, and the rolling speed is 0.35-0.6 m / s.

[0055] In a preferred embodiment of the present invention, in step 3, the piercing is performed using a three-roll skew rolling mill, with the piercing rolls and piercing mandrel replaced, the compression ratio being 10-15%, and the maximum piercing diameter-to-thickness ratio being 30:1.

[0056] In a preferred embodiment of the present invention, both the first and second cold rolling processes are carried out using a two-roll tube rolling mill, and rolls and mandrels that match the specifications of the tube blank are selected.

[0057] In a preferred embodiment of the present invention, before the first and second cold rolling processes, the inner hole of the tube blank is bored, and the two ends are cut flat and deburred; during rolling, grease is applied to the joints at both ends of the tube, and lubricating oil is injected into the inner hole of the tube blank.

[0058] In a preferred embodiment of the present invention, the rolling temperature of the first and second cold rolling is room temperature, and the feed amount per pass is 1.5-3 mm.

[0059] In a preferred embodiment of the present invention, the deformation amount of the first cold rolling is 15-35%, and the Q value is 1.1-1.7; the deformation amount of the second cold rolling is 10-30%, and the Q value is 1-1.5, where Q value is the ratio of axial elongation coefficient to radial compression coefficient during rolling.

[0060] In a preferred embodiment of the present invention, in steps 4 and 5, the intermediate recrystallization heat treatment is performed at a temperature of 800-950 °C for 2 hours, and the cooling method is air cooling.

[0061] In a preferred embodiment of the present invention, in step 6, the temperature of the vacuum heat treatment is 680-750 ℃, and the holding time is 0.5-4 h.

[0062] In a preferred embodiment of the present invention, in step 6, the finished product is annealed in a vacuum heat treatment furnace.

[0063] In a preferred embodiment of the present invention, step 6, the vacuum heat treatment of the finished product further includes the following process parameters: the vacuum working pressure is not greater than 6 × 10⁻⁶. -2 Pa, heat preservation time is 0.5-4 h, pipe is cooled with the furnace to 300-350 ℃ and then removed from the furnace hood, cooled with the furnace for 5-10 h after removal from the furnace hood, and the furnace temperature is less than 100 ℃.

[0064] As a preferred embodiment of the present invention, the outer diameter of the large-diameter thin-walled TA31 titanium alloy seamless tube obtained in step 6 is Φ114-273 mm, the wall thickness is 3-14 mm, and the length is 3-6 m.

[0065] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0066] Example 1: Sponge titanium and intermediate alloys Al, Nb, Zr and Mo were mixed and smelted to obtain TA31 ingots; the elements were as follows by mass percentage: Al 6.0%, Nb 3.0%, Zr 2.0%, Mo 1.0%, and the balance was Ti.

[0067] The ingot is forged into a titanium billet and then machined into a bright rod; the bright rod is then subjected to a β transformation temperature T. βTesting.

[0068] The preparation process of the bright rod is as follows: the ingot is heated in a resistance furnace to a temperature of 1080 ℃; a 2000 T high-speed forging machine is used for three-stage forging and three-stage drawing, with a forging ratio of 1.8; the billet is milled and ground, and then sawn; it is reheated to 1040 ℃ for preliminary deformation, with a total deformation of 55%; it is then reheated to 980 ℃ and forged into a blank using an electro-hydraulic hammer; the blank is sawn and peeled to obtain the bright rod.

[0069] Heat the light rod to T β The tube blank is pierced once at 50 ℃ using a three-roll skew rolling mill with a compression ratio of 15% and a piercing diameter-to-thickness ratio of 8:1 to obtain a thick-walled tube blank.

[0070] The thick-walled tube blank is heated to T. β The tube blank is produced by extending and piercing at 30 ℃ using a three-roll skew rolling mill, with the extension rolls and extension mandrel replaced, the compression ratio is 12%, and the piercing diameter-to-thickness ratio is 25:1.

[0071] The thin-walled tube blank was subjected to intermediate recrystallization heat treatment at a temperature of 880 ℃ for 2 h, followed by air cooling; then it was subjected to a cold rolling process.

[0072] The tube blank after one cold rolling is subjected to intermediate recrystallization heat treatment at 900 ℃ for 2 hours, followed by air cooling; then a second cold rolling is performed. The deformation of the first cold rolling is 25%, with a Q value of 1.4; the deformation of the second cold rolling is 20%, with a Q value of 1.2.

[0073] Vacuum heat treatment was performed on the tube blank after two cold rolling processes at a temperature of 720 ℃ for 2 h to obtain large-diameter thin-walled TA31 titanium alloy seamless tubes.

[0074] The final pipe has an outer diameter of Φ168 mm, a wall thickness of 8 mm, and a length of 4 m.

[0075] Example 2: Sponge titanium and intermediate alloys Al, Nb, Zr and Mo were mixed and smelted to obtain TA31 ingots; the elements by mass percentage were: Al 5.8%, Nb 2.8%, Zr 1.8%, Mo 0.8%, and the balance was Ti.

[0076] The ingot was forged into a titanium billet and machined into a bright rod, and the β transformation temperature T of the bright rod was measured. β .

[0077] Heat the light rod to T β The tube blank is produced by piercing once at 40 ℃ with a compression ratio of 13% and a piercing diameter-to-thickness ratio of 6:1.

[0078] Heat the thick-walled tube blank to T. β The tube blank is produced by extending and piercing at 25 ℃ with a compression ratio of 11% and a piercing diameter-to-thickness ratio of 20:1.

[0079] The thin-walled tube blank was subjected to intermediate recrystallization heat treatment at 820 ℃ for 2 h, followed by air cooling; then it was subjected to a cold rolling process.

[0080] The tube blank after one cold rolling is subjected to intermediate recrystallization heat treatment at 850 ℃ for 2 h, followed by air cooling; then a second cold rolling is performed. The deformation of the first cold rolling is 20%, with a Q value of 1.2; the deformation of the second cold rolling is 15%, with a Q value of 1.1.

[0081] The tube blank after two cold rolling processes was subjected to vacuum heat treatment at 700 ℃ for 1 h.

[0082] The final pipe has an outer diameter of Φ114 mm, a wall thickness of 5 mm, and a length of 3 m.

[0083] Example 3: TA31 ingots were prepared by mixing sponge titanium with intermediate alloys Al, Nb, Zr and Mo and then smelting them; the mass percentages of each element were: Al 6.3%, Nb 3.2%, Zr 2.3%, Mo 1.3%, and the balance was Ti.

[0084] The ingot was forged into a titanium billet and machined into a bright rod, and the β transformation temperature T of the bright rod was measured. β .

[0085] Heat the light rod to T β The tube blank is produced by piercing once at 70 ℃ with a compression ratio of 18% and a piercing diameter-to-thickness ratio of 10:1.

[0086] Heat the thick-walled tube blank to T β The tube blank is produced by extending and piercing at 45 ℃ with a compression ratio of 15% and a piercing diameter-to-thickness ratio of 30:1.

[0087] The thin-walled tube blank was subjected to intermediate recrystallization heat treatment at 940 ℃ for 2 h, followed by air cooling; then it was subjected to one cold rolling.

[0088] The tube blank after one cold rolling was subjected to intermediate recrystallization heat treatment at 920 ℃ for 2 h, followed by air cooling; then a second cold rolling was performed. The deformation of the first cold rolling was 35%, with a Q value of 1.7; the deformation of the second cold rolling was 30%, with a Q value of 1.5.

[0089] The tube blank after the second cold rolling was subjected to vacuum heat treatment at 740 ℃ for 4 h.

[0090] The final pipe has an outer diameter of Φ273 mm, a wall thickness of 14 mm, and a length of 6 m.

[0091] To further illustrate the influence of different processes in this invention on material properties and microstructure, the mechanical properties and microstructure after each key process were tested, and the results are shown in Table 1:

[0092] Table 1

[0093]

[0094] As shown in Table 1, during the first piercing stage, the tensile strength of the material is 883 MPa, the yield strength is 836 MPa, the elongation is 10.5%, and the microstructure is mainly Widmanstätten structure.

[0095] During the extended perforation stage, when perforation is performed in the α-β two-phase region, the tensile strength of the material increases to 919 MPa, the yield strength is 842 MPa, the elongation increases to 13.5%, and the microstructure transforms into basketweave structure; while when perforation is performed above Tβ, the tensile strength of the material is 896 MPa, the yield strength is 824 MPa, the elongation is 11.5%, and the microstructure is still dominated by Widmanstätten structure.

[0096] In the subsequent cold rolling process, after one cold rolling, the tensile strength of the material increased to 957 MPa, the yield strength was 896 MPa, the elongation was 14.0%, and the microstructure showed a bimodal structure; after two cold rollings, the tensile strength of the material further increased to 973 MPa, the yield strength was 917 MPa, the elongation reached 16.5%, and the microstructure transformed into a mixed structure of equiaxed and β-transformed structures.

[0097] In summary, combining β-region perforation with α-β two-phase region extension perforation, along with subsequent cold rolling processes, can effectively improve the microstructure and enhance the mechanical properties of materials.

[0098] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for manufacturing large-diameter, thin-walled TA31 titanium alloy seamless tubing, characterized in that, Includes the following steps: Step 1: After mixing sponge titanium and intermediate alloy, smelt to obtain TA31 ingot. Forge the ingot into titanium billet and process it into a bright rod. Measure the β transformation temperature T of the bright rod. β ; Step 2: Heat the light bar to T β A thick-walled tube blank is obtained by piercing once at 30-80 ℃. Step 3: Heat the thick-walled tube blank to T β The tube blank is produced by stretching and piercing at 20-50 ℃. Step 4: After intermediate recrystallization heat treatment, the thin-walled tube blank is subjected to one cold rolling process; Step 5: After the first cold-rolled tube blank undergoes intermediate recrystallization heat treatment, it is then subjected to a second cold rolling. Step 6: Vacuum heat treatment is performed on the tube blank after the second cold rolling to obtain the large-diameter thin-walled TA31 titanium alloy seamless tube.

2. The method for manufacturing a large-diameter, thin-walled TA31 titanium alloy seamless tube according to claim 1, characterized in that, The intermediate alloy comprises Al, Nb, Zr and Mo; the smelting composition of TA31, by mass percentage, comprises: Al 5.5-6.5%, Nb 2.5-3.5%, Zr 1.5-2.5%, Mo 0.6-1.5%, with the balance being Ti.

3. The method for manufacturing a large-diameter, thin-walled TA31 titanium alloy seamless tube according to claim 1, characterized in that, In step 2, the first piercing is carried out using a three-roll skew rolling mill with a compression ratio of 12-18% and a piercing diameter-to-thickness ratio of 5-10:

1.

4. The method for manufacturing a large-diameter, thin-walled TA31 titanium alloy seamless tube according to claim 1, characterized in that, In step 3, the piercing is carried out using a three-roll skew rolling mill with a compression ratio of 10-15% and a maximum piercing diameter-to-thickness ratio of 30:

1.

5. The method for manufacturing a large-diameter, thin-walled TA31 titanium alloy seamless tube according to claim 1, characterized in that, The deformation amount of the first cold rolling is 15-35%, and the Q value is 1.1-1.7; the deformation amount of the second cold rolling is 10-30%, and the Q value is 1-1.

5.

6. The method for manufacturing a large-diameter, thin-walled TA31 titanium alloy seamless tube according to claim 1, characterized in that, In steps 4 and 5, the intermediate recrystallization heat treatment is performed at a temperature of 800-950 ℃ for 2 h, and the cooling method is air cooling.

7. The method for manufacturing a large-diameter, thin-walled TA31 titanium alloy seamless tube according to claim 1, characterized in that, In step 6, the vacuum heat treatment temperature is 680-750 ℃, and the holding time is 0.5-4 h.

8. A method for manufacturing a large-diameter, thin-walled TA31 titanium alloy seamless tube according to any one of claims 1-7, characterized in that, The outer diameter of the large-diameter thin-walled TA31 titanium alloy seamless tube obtained in step 6 is Φ114-273 mm, the wall thickness is 3-14 mm, and the length is 3-6 m.

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