A method for die forging forming of a high-strength high-toughness damage-tolerant titanium alloy cylindrical piece

Abstract

The application discloses a die forging forming method of a high-strength and high-toughness damage tolerance titanium alloy cylinder, which comprises the following steps: S1, heating raw materials; S2, primary forging; S3, surface treatment; S4, secondary forging; and S5, annealing. The method can reduce the weight of raw materials and the number of forging fires, thereby reducing the production cost, and meanwhile, can guarantee that the product has good performances and the stability of product quality is good.

Description

Technical Field

[0001] This invention relates to the field of metal forging technology, specifically to a method for die forging high-strength, high-toughness, damage-tolerant titanium alloy cylindrical parts. Background Technology

[0002] TC21 titanium alloy possesses a good balance of strength, plasticity, fracture toughness, and crack propagation rate, making it a promising titanium alloy for various applications. With the rapid development of the aerospace industry towards lightweight structures, the emergence of new alloy materials is undoubtedly a significant indicator of the development of advanced aircraft in my country. To accelerate the application of TC21 titanium alloy in the aerospace industry, it is necessary to expedite research into its related theories, develop mature processing techniques, and explore its performance potential to ensure it meets the performance requirements of the aerospace industry for structural materials.

[0003] The original forging shape of the shell forging has a large machining allowance on one side and a solid core structure, resulting in low utilization of forging materials. During forging, the free forging billet needs to be drawn in two heats, which results in low production efficiency and many surface defects. It also has the disadvantages of large product processing volume, long roughing time, and high processing cost. Therefore, it is necessary to optimize the forging processing method to improve the utilization of forging materials and improve billet quality, so as to achieve the goal of cost reduction and efficiency improvement. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a die forging method for high-strength, high-toughness, and damage-tolerant titanium alloy cylindrical parts.

[0005] A die forging method for a high-strength, high-toughness, damage-tolerant titanium alloy cylindrical part includes the following steps:

[0006] S1. Heating the raw materials:

[0007] Take the titanium alloy forging, cut it, and then heat it to (T). β -50)±10℃, then hold at that temperature for 70~120min; to obtain the heated forging; wherein, T β The β-phase transformation temperature of titanium alloy forgings;

[0008] S2, One-time forging:

[0009] The heated forging material is placed in a forging die for forging. The hammering rate is 30-45 times / min, the forging time is 30-45 seconds, and the impact energy is 700-900 tons. Then it is air-cooled to 25°C to obtain the initial forging.

[0010] S3. Surface treatment:

[0011] After shot blasting, grinding, and shot blasting again, the initial forging is held at 120–150°C for 10–20 minutes. Then, the initial forging is removed and coated with glass lubricant. After the glass lubricant dries, it is heated until the initial forging reaches a temperature of (T). β The temperature is set at -50)±10℃, and then held for 75~150min to obtain the pre-forged part;

[0012] S4, Secondary forging;

[0013] The pre-forged part is placed into the finished product mold for forging. During the forging process, the impact energy is 1100-1250 tons, and then it is air-cooled to 500-550°C. After the forging is completed, the final forging part is obtained.

[0014] S5, Annealing:

[0015] The final forging is first annealed at 880-930°C for 145-155 min, and then air-cooled to 300-450°C to obtain the final forging after one annealing.

[0016] The final forging after the first annealing is then subjected to a second annealing at 500-550°C for 235-245 minutes, and then air-cooled to 25°C to obtain the formed part.

[0017] Explanation: The above method can reduce the weight of raw materials and the number of forging processes, thereby reducing production costs while ensuring good product performance and stable product quality. By heating the raw materials, the β-phase transformation temperature of the titanium alloy forgings can be used to make the microstructure of the titanium alloy forgings in an easily machinable state. Through single forging and double forging, the strength and toughness of the titanium alloy forgings can be improved. Surface treatment can protect the surface of the titanium alloy and prevent oxidation and other phenomena. Annealing can further improve toughness and other properties.

[0018] Furthermore, the titanium alloy is TC21; T β The temperature ranges from 945 to 975℃.

[0019] Note: TC21 titanium alloy is a two-phase titanium alloy. The titanium alloy structure defined above has high strength and fracture toughness, and strong resistance to crack propagation, making it an ideal structure for parts that have been in long-term high-temperature service.

[0020] Furthermore, in S2, when the heated titanium alloy is placed in a forging die for forging, the placement time is 0.1 to 15 seconds.

[0021] Note: By setting the placement time as described above, we can prevent oxidation and cracking of the titanium alloy surface caused by excessive time, thus preventing ore mining.

[0022] Further, in S1, the titanium alloy forging is a shell forging; the diameter of the titanium alloy forging after cutting is 55-95% of that before cutting, and the height of the titanium alloy forging after cutting is 74-260% of that before cutting.

[0023] Note: The above-described processing of the shell forging can reduce the processing cost in the prior art.

[0024] Furthermore, in S1, the method for cutting the titanium alloy forging is as follows: reducing the thickness of the machining allowance of the titanium alloy forging, increasing the height of the upper punch of the titanium alloy forging, increasing the length of the lower punch, and hollowing out the hole.

[0025] Note: The above-mentioned cutting and processing methods can ensure the quality stability of titanium alloy for shell forgings, and compared with unprocessed shell forgings, their various properties are similar or even better.

[0026] Furthermore, in S3, the method for performing shot blasting, grinding, and shot blasting again on the initial forging is as follows:

[0027] The first shot blasting uses steel balls with a particle size of 2-2.5mm and a shot blasting speed of 60-70m / s; the grinding uses a force of 120-150 grit and a grinding pressure of 5-15N; the second shot blasting uses steel balls with a particle size of 0.5-1.5mm and a shot blasting speed of 30-50m / s.

[0028] Note: The above surface treatment method makes the surface of the initial forging smoother, and the two shot blasting processes can introduce residual compressive stress on the alloy surface, which can improve the fatigue strength and resistance to stress corrosion cracking of the material.

[0029] Furthermore, the thickness of the sprayed glass lubricant is 1-3 mm, and the glass lubricant used is a modified borosilicate glass lubricant.

[0030] Note: By setting the above-mentioned sprayed glass lubricant, the surface of the initial forging can be better protected, the service life of the forging can be extended, and the high temperature resistance of the forging can be improved.

[0031] Furthermore, the modified borosilicate glass lubricant is prepared through the following steps:

[0032] Borax, sodium silicate, magnesium oxide, and zinc oxide were placed in a ball mill jar at a mass ratio of 2-3:1-2:0.05:0.03 and milled at 200 r / min for 30-40 min. Then, the mixture was placed in a high-temperature furnace and melted at 1300-1400℃ for 2-4 h. The molten glass was then rapidly cooled, quenched in water, and ground to obtain glass powder.

[0033] Add 15-20% of a silane coupling agent by weight of the glass powder to the glass powder and stir continuously to obtain a mixture. Mix the mixture with polytetrafluoroethylene powder at a mass ratio of 10:1-2 and then dry it until the moisture content is less than 0.1% to obtain a modified borosilicate glass lubricant.

[0034] Note: The modified borosilicate glass lubricant obtained by the above method has good thermal and chemical stability, and can improve lubrication performance and adhesion to titanium alloy surfaces.

[0035] Furthermore, during the first annealing process, under normal pressure and nitrogen atmosphere, the final forging is first heated to 880-930°C at a heating rate of 5-7°C / min, then kept at a constant temperature for 145-155min, and then cooled to 300-450°C at a cooling rate of 8-10°C / min.

[0036] During the secondary annealing process, the final forging after the first annealing is first heated to 500-550°C at a heating rate of 8-10°C / min under a nitrogen atmosphere and a pressure of 0.22-0.30 MPa. Then, it is kept at a constant temperature for 235-245 min and then cooled to 25°C at a cooling rate of 4-6°C / min.

[0037] Explanation: The above method allows the internal stress generated during the forging process to be relieved through two annealing processes, preventing cracks or deformation in the material during subsequent processing. At the same time, it can refine the grains, thereby improving the microstructure and ductility of the metal, and thus improving the overall performance of the material.

[0038] Furthermore, during the isothermal resting process of the first annealing, a magnetic field with a strength of 20-50 Oe is applied, and the magnetic field strength decreases with the isothermal resting time at a rate of 0.1 Oe / min. When the isothermal resting is completed and the cooling begins, the magnetic field is turned off and nitrogen is introduced to a pressure of 0.18-0.20 MPa until the cooling is completed, and then the pressure is adjusted to atmospheric pressure.

[0039] During the isothermal resting process of the secondary annealing, a magnetic field with a strength of 20-50 Oe is applied. The magnetic field strength first increases and then decreases with the isothermal resting time. In the first 100 minutes of isothermal resting, the magnetic field strength increases at a rate of 0.15 Oe / min. In the subsequent isothermal resting time, the magnetic field strength decreases at a rate of 0.1 Oe / min. After the isothermal resting is completed, the magnetic field is turned off, the pressure is adjusted to normal pressure, and then the temperature is lowered.

[0040] Note: The above-mentioned conditions set during the constant temperature standing process can enhance the annealing effect and have a good improvement effect on the microstructure of the titanium alloy in this scheme, giving it high strength, high toughness and damage tolerance characteristics.

[0041] The beneficial effects of this invention are:

[0042] The method of this invention can reduce the weight of raw materials and the number of forging passes, thereby reducing production costs while ensuring good product performance and stable product quality. By heating the raw materials, the β-phase transformation temperature of the titanium alloy forgings can be utilized to bring the microstructure of the titanium alloy forgings into a machinable state. Single and double forging can improve the strength and toughness of the titanium alloy forgings. Surface treatment can protect the surface of the titanium alloy and prevent oxidation. Annealing can further improve toughness and other properties. TC21 titanium alloy is a two-phase titanium alloy, and its typical microstructure mainly includes four types: equiaxed structure, biphase structure, basketweave structure, and Widmanstätten structure. Among them, the basketweave structure is formed by the transformed α phase weaving into a basket-like structure. This structure has high strength and fracture toughness, and strong resistance to crack propagation, making it an ideal microstructure for parts that serve at high temperatures for extended periods. The surface treatment method makes the surface of the initial forging smoother, and the two shot blasting processes can introduce residual compressive stress on the alloy surface, which can improve the fatigue strength and resistance to stress corrosion cracking of the material. Attached Figure Description

[0043] Figure 1 These are comparison images of the cutting process before and after in Embodiment 1 of the present invention;

[0044] Figure 2 These are comparison images of the cutting process before and after in Embodiment 17 of the present invention;

[0045] Figure 3 These are comparison images of the cutting process before and after in Embodiment 18 of the present invention. Detailed Implementation

[0046] To further illustrate the methods and effects of this invention, the technical solution of this invention will be clearly and completely described below in conjunction with experiments.

[0047] Example 1: A die forging method for a high-strength, high-toughness, damage-tolerant titanium alloy cylindrical part, comprising the following steps:

[0048] S1. Heating the raw materials:

[0049] Titanium alloy forgings are cut and processed, then heated to 925℃ and held for 100 minutes to obtain heated forgings. The titanium alloy forgings are shell forgings with specifications of Φ85±1×215±1mm, weight of 5.51Kg, and quota of 5.63Kg. The diameter of the titanium alloy forgings after cutting is 70% of that before cutting, and the height of the titanium alloy forgings after cutting is 120% of that before cutting.

[0050] like Figure 1 As shown in S1, the method for cutting and processing the titanium alloy forging is as follows: reducing the thickness of the machining allowance of the titanium alloy forging, increasing the height of the upper punch of the titanium alloy forging, increasing the length of the lower punch and making a hole.

[0051] S2, One-time forging:

[0052] The heated forging material is placed in a forging die for forging. The hammering rate is 40 times / min, the forging time is 30s, and the impact energy is 800 tons. Then it is air-cooled to 25°C to obtain a preliminary forging. In S2, when the heated titanium alloy is placed in the forging die for forging, the placement time is 5s.

[0053] S3. Surface treatment:

[0054] After shot blasting, grinding, and shot blasting again, the initial forging is kept at 140°C for 15 minutes. Then, the initial forging is taken out and sprayed with glass lubricant. After the glass lubricant dries, it is heated to 925°C and then kept at that temperature for 100 minutes to obtain the pre-forging.

[0055] In S3, the method for performing shot blasting, grinding, and shot blasting again on the initial forging is as follows:

[0056] The first shot blasting uses steel balls with a particle size of 2.1 mm and a shot blasting speed of 65 m / s; the grinding uses a force of 130 grit and a grinding pressure of 10 N; the second shot blasting uses steel balls with a particle size of 1 mm and a shot blasting speed of 40 m / s.

[0057] The thickness of the sprayed glass lubricant is 2mm, and the glass lubricant used is a modified borosilicate glass lubricant.

[0058] The modified borosilicate glass lubricant is prepared through the following steps:

[0059] Borax, sodium silicate, magnesium oxide, and zinc oxide were placed in a ball mill jar with a mass ratio of 2.5:1.5:0.05:0.03 and milled at a rate of 200 r / min for 35 min. Then, the mixture was placed in a high-temperature furnace and melted at 1350℃ for 3 h. The molten glass was then rapidly cooled, quenched in water, and ground to obtain glass powder.

[0060] Add 18% of a silane coupling agent by weight of the glass powder to the glass powder and stir continuously to obtain a mixture. Mix the mixture with polytetrafluoroethylene powder at a mass ratio of 10:1.5 and then dry it until the moisture content is less than 0.1% to obtain a modified borosilicate glass lubricant.

[0061] S4, Secondary forging;

[0062] The pre-forged part is placed into a finished product mold for forging. During the forging process, the impact energy is 1200 tons, and then it is air-cooled to 525°C. After the forging is completed, the final forging part is obtained.

[0063] S5, Annealing:

[0064] The final forging is first annealed at 900°C for 150 minutes, and then air-cooled to 400°C to obtain the final forging after one annealing.

[0065] The final forging after the first annealing is then subjected to a second annealing at 510°C for 240 minutes, and then air-cooled to 25°C to obtain the formed part.

[0066] During the first annealing process, under normal pressure and nitrogen atmosphere, the final forging is first heated to 900°C at a heating rate of 6°C / min, then kept at a constant temperature for 150 min, and then cooled to 400°C at a cooling rate of 9°C / min.

[0067] During the secondary annealing process, the final forging after the first annealing is first heated to 510°C at a heating rate of 9°C / min under a nitrogen atmosphere and a pressure of 0.25 MPa. Then it is kept at a constant temperature for 240 min and then cooled to 25°C at a cooling rate of 5°C / min.

[0068] Example 2: This example differs from Example 1 in that the parameters for heating the raw material in S1 are different. A titanium alloy forging is cut and processed, then heated to 915°C and held for 70 minutes to obtain the heated forging. Wherein, T... βThe β-phase transformation temperature of the titanium alloy forging; the titanium alloy is TC21; the titanium alloy forging is a shell forging; the diameter of the titanium alloy forging after cutting is 55% of that before cutting, and the height of the titanium alloy forging after cutting is 260% of that before cutting.

[0069] Example 3: This example differs from Example 1 in that the parameters for heating the raw material in S1 are different. Titanium alloy forgings are cut and processed, then heated to 935°C and held for 120 minutes to obtain the heated forgings; wherein, T... β The β-phase transformation temperature of the titanium alloy forging; the titanium alloy is TC21; the titanium alloy forging is a shell forging; the diameter of the titanium alloy forging after cutting is 95% of that before cutting, and the height of the titanium alloy forging after cutting is 74% of that before cutting.

[0070] Example 4: This example differs from Example 1 in that the parameters of the forging in S2 are different. The heated forging material is placed in the forging die for forging, the hammering rate is 30 times / min, the forging time is 45s, and the impact energy is 700 tons; then it is air-cooled to 25°C; a preliminary forging is obtained; in S2, when the heated titanium alloy is placed in the forging die for forging, the placement time is 15s.

[0071] Example 5: This example differs from Example 1 in that the parameters of the forging in S2 are different. The heated forging material is placed in the forging die for forging, the hammering rate is 45 times / min, the forging time is 30s, and the impact energy is 900 tons; then it is air-cooled to 25°C; a preliminary forging is obtained; in S2, when the heated titanium alloy is placed in the forging die for forging, the placement time is 0.1s.

[0072] Example 6: This example differs from Example 1 in that the surface treatment parameters of S3 are different. After the initial forging is shot-blasted, polished, and shot-blasted again, the initial forging is kept at 120°C for 20 minutes. Then the initial forging is taken out and sprayed with glass lubricant. After the glass lubricant dries, it is heated to 925°C and then kept at that temperature for 75 minutes to obtain the pre-forging.

[0073] The method for shot blasting, grinding, and shot blasting the initial forging is as follows: the first shot blasting uses steel balls with a particle size of 2.5mm and a shot blasting speed of 70m / s; the grinding uses a force of 150 mesh and a grinding pressure of 15N; the second shot blasting uses steel balls with a particle size of 1.5mm and a shot blasting speed of 30m / s.

[0074] Example 7: This example differs from Example 1 in that the surface treatment parameters of S3 are different. After the initial forging is shot-blasted, polished, and shot-blasted again, the initial forging is held at 150°C for 10 minutes. Then the initial forging is taken out and sprayed with glass lubricant. After the glass lubricant dries, it is heated to 925°C and then held for 150 minutes to obtain the pre-forging.

[0075] The method for shot blasting, grinding, and shot blasting the initial forging is as follows: the first shot blasting uses steel balls with a particle size of 2mm and a shot blasting speed of 60m / s; the grinding uses a force of 120 mesh and a grinding pressure of 5N; the second shot blasting uses steel balls with a particle size of 0.5mm and a shot blasting speed of 50m / s.

[0076] Example 8: This example differs from Example 1 in that the preparation parameters of the modified borosilicate glass lubricant are different. Borax, sodium silicate, magnesium oxide, and zinc oxide are taken in a mass ratio of 3:1:0.05:0.03, placed in a ball mill jar, and ball-milled at a rate of 200 r / min for 40 min. Then, it is placed in a high-temperature furnace and melted at a temperature of 1300℃ for 4 h. The molten glass is then rapidly cooled, water-quenched, and ground to obtain glass powder.

[0077] A silane coupling agent of 15% by weight of the glass powder is added to the glass powder and stirred continuously to obtain a mixture. The mixture is then mixed with polytetrafluoroethylene powder at a mass ratio of 10:1 and dried until the moisture content is less than 0.1% to obtain a modified borosilicate glass lubricant.

[0078] Example 9: This example differs from Example 1 in that the preparation parameters of the modified borosilicate glass lubricant are different. Borax, sodium silicate, magnesium oxide, and zinc oxide are taken in a mass ratio of 2:2:0.05:0.03, placed in a ball mill jar, and ball-milled at a rate of 200 r / min for 30 min. Then, it is placed in a high-temperature furnace and melted at a temperature of 1400℃ for 2 h. The molten glass is then rapidly cooled, water-quenched, and ground to obtain glass powder.

[0079] Add 20% of the mass of the glass powder to the glass powder and stir continuously to obtain a mixture. Mix the mixture with polytetrafluoroethylene powder at a mass ratio of 10:2 and then dry it until the moisture content is less than 0.1% to obtain a modified borosilicate glass lubricant.

[0080] Example 10: The difference between this example and Example 1 is that the parameters of the S4 secondary forging are different. The pre-forged part is placed into the finished product mold for forging. During the forging process, the impact energy is 1100 tons, and then it is air-cooled to 500°C. After the forging is completed, the final forging part is obtained.

[0081] Example 11: This example differs from Example 1 in that the parameters of the S4 secondary forging are different. The pre-forged part is placed into the finished product mold for forging. During the forging process, the impact energy is 1250 tons and then air-cooled to 550°C. After the forging is completed, the final forging part is obtained.

[0082] Example 12: This example differs from Example 1 in that the S5 annealing parameters are different. The final forging is first annealed at 880°C for 155 minutes, and then air-cooled to 300°C to obtain the final forging after one annealing. The final forging after one annealing is then annealed again at 550°C for 235 minutes, and then air-cooled to 25°C to obtain the formed part.

[0083] During the first annealing process, under normal pressure and nitrogen atmosphere, the final forging is first heated to 880°C at a heating rate of 5°C / min, then kept at a constant temperature for 155 min, and then cooled to 450°C at a cooling rate of 10°C / min.

[0084] During the secondary annealing process, the final forging after the first annealing is first heated to 550°C at a heating rate of 8°C / min under a nitrogen atmosphere and a pressure of 0.22 MPa. Then it is kept at a constant temperature for 245 min and then cooled to 25°C at a cooling rate of 4°C / min.

[0085] Example 13: This example differs from Example 1 in that the S5 annealing parameters are different. The final forging is first annealed at 930°C for 145 minutes, and then air-cooled to 450°C to obtain the final forging after one annealing. The final forging after one annealing is then annealed again at 550°C for 235 minutes, and then air-cooled to 25°C to obtain the formed part.

[0086] During the first annealing process, under normal pressure and nitrogen atmosphere, the final forging is first heated to 930°C at a heating rate of 7°C / min, then kept at a constant temperature for 145 minutes, and then cooled to 300°C at a cooling rate of 8°C / min.

[0087] During the secondary annealing process, the final forging after the first annealing is first heated to 500°C at a heating rate of 10°C / min under a nitrogen atmosphere and a pressure of 0.30 MPa. Then it is kept at a constant temperature for 235 min and then cooled to 25°C at a cooling rate of 6°C / min.

[0088] Example 14: This example differs from Example 1 in that, during the isothermal resting process of the first annealing, a magnetic field with a strength of 40 Oe is applied, and the magnetic field strength decreases with the isothermal resting time at a rate of 0.1 Oe / min. When the isothermal resting is completed and cooling begins, the magnetic field is turned off and nitrogen is introduced until the pressure reaches 0.19 MPa. After cooling is completed, the pressure is adjusted to atmospheric pressure.

[0089] During the isothermal resting process of the secondary annealing, a magnetic field with a strength of 45 Oe is applied. The magnetic field strength first increases and then decreases with the isothermal resting time. In the first 100 minutes of isothermal resting, the magnetic field strength increases at a rate of 0.15 Oe / min. In the subsequent isothermal resting time, the magnetic field strength decreases at a rate of 0.1 Oe / min. After the isothermal resting is completed, the magnetic field is turned off, the pressure is adjusted to normal pressure, and then the temperature is lowered.

[0090] Example 15: The difference between this example and Example 14 is that the processing parameters for the first annealing and the second annealing constant temperature standing are different. During the constant temperature standing process of the first annealing, a magnetic field with a strength of 50 Oe is applied, and the magnetic field strength decreases with the constant temperature standing time at a rate of 0.1 Oe / min. When the constant temperature standing is completed and the cooling begins, the magnetic field is turned off and nitrogen is introduced until the pressure is 0.20 MPa. After the cooling is completed, the pressure is adjusted to atmospheric pressure.

[0091] During the isothermal resting process of the secondary annealing, a magnetic field with a strength of 20 Oe is applied. The magnetic field strength first increases and then decreases with the isothermal resting time. In the first 100 minutes of isothermal resting, the magnetic field strength increases at a rate of 0.15 Oe / min. In the subsequent isothermal resting time, the magnetic field strength decreases at a rate of 0.1 Oe / min. After the isothermal resting is completed, the magnetic field is turned off, the pressure is adjusted to normal pressure, and then the temperature is lowered.

[0092] Example 16: The difference between this example and Example 14 is that the processing parameters for the first annealing and the second annealing constant temperature standing are different. During the constant temperature standing process of the first annealing, a magnetic field with a strength of 20 Oe is applied, and the magnetic field strength decreases with the constant temperature standing time at a rate of 0.1 Oe / min. When the constant temperature standing is completed and the cooling begins, the magnetic field is turned off and nitrogen is introduced until the pressure is 0.18 MPa. After the cooling is completed, the pressure is adjusted to atmospheric pressure.

[0093] During the isothermal resting process of the secondary annealing, a magnetic field with a strength of 50 Oe is applied. The magnetic field strength first increases and then decreases with the isothermal resting time. In the first 100 minutes of isothermal resting, the magnetic field strength increases at a rate of 0.15 Oe / min. In the subsequent isothermal resting time, the magnetic field strength decreases at a rate of 0.1 Oe / min. After the isothermal resting is completed, the magnetic field is turned off, the pressure is adjusted to normal pressure, and then the temperature is lowered.

[0094] Example 17: This example differs from Example 1 in that the shape of the shell forging is different, such as... Figure 2 As shown, the specific method for cutting titanium alloy forgings described in S1 is as follows: Machining allowance: The single-sided machining allowance of the outer diameter of the forging is adjusted from 3.0mm to 1.0mm; the single-sided machining allowance of the inner diameter is adjusted from 11.0mm to 2.0mm; the single-sided machining allowance in the height direction remains unchanged; Forging shape: The height of the upper punch of the original forging is adjusted from 41mm to 120mm, and a 35mm punch is added to the lower die, thereby reducing the material used in the core of the forging; Forging blank before cutting: Φ90×295, quota: 8.6Kg; Forging blank after cutting: Φ85×220, quota: 5.7Kg; Material reduction ≈ 2.9Kg; Rough machining: The original solid core of the forging is ≈144mm, and the optimized forging with the middle skin is ≈30mm. When rough machining the hole, the machining time can be greatly reduced; at the same time, the machining allowance of the outer / inner diameter of the forging is reduced, which also reduces the rough machining time to a certain extent.

[0095] Example 18: This example differs from Example 1 in that the shape of the shell forging is different, such as... Figure 3 As shown, the specific method for cutting titanium alloy forgings described in S1 is as follows: Machining allowance: The single-sided machining allowance of the outer diameter of the forging is adjusted from 3.0mm to 1.0mm; the single-sided machining allowance of the inner diameter of the forging is adjusted from 10.0mm to 2.0mm; Forging shape: The height of the upper punch of the original forging is adjusted from 24mm to 101mm, and a 35mm punch is added to the lower die, thereby reducing the material used in the core of the forging; Forging blank before cutting: Φ154×130, quota: 11.3Kg; Forging blank before and after cutting: Φ85×335, quota: 8.6Kg; Material reduction ≈ 2.7Kg;

[0096] Forging cycles: The original forging scheme required two forging cycles to lengthen the free forging billet, with a single-piece operation time of ≈6 minutes. After optimization, the free forging billet only needs one forging cycle, with a single-piece operation time of ≈1.5 minutes. The number of forging cycles is reduced and the operation time is shortened. Rough machining: The original forging core was solid ≈227mm, while the optimized forging with the skin in the middle is ≈111mm. When rough machining the hole, the machining time can be greatly reduced.

[0097] Experimental example: Multiple performance tests were conducted on the samples obtained from Examples 1 to 16, and the test results are as follows:

[0098] 1. Investigate the effects of different treatment methods on the properties of molded parts;

[0099] Comparative Example 1: Unlike Example 1, no cutting was performed; the forging was carried out directly.

[0100] Comparative Example 2: Unlike Example 1, no grinding or shot blasting was performed; only one shot blasting was performed.

[0101] Comparative Example 3: The difference from Example 1 is that a commercially available borosilicate glass lubricant was used.

[0102] Comparative Example 4: The difference from Example 1 is that the heating rate and cooling rate of the first annealing and the second annealing are the same, both being 9°C / min.

[0103] First, 100 shell forgings were produced according to the methods of Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 respectively. Then, the pass rate of the finished products obtained by each method was statistically analyzed. The results showed that the surface of Example 1 was relatively normal and no cracks were found. Correspondingly, some shell forgings of Comparative Example 2 and Comparative Example 3 had cracks.

[0104] II. A comparison of the performance tests conducted on Examples 1, 2, 3, 14, and Comparative Examples 1 to 4 is shown in Table 1.

[0105] Table 1. Performance test results of finished products obtained by forging under different treatment methods.

[0106]

[0107] Combination Figure 1 As can be seen from Table 1, comparing Example 1 and Comparative Example 1, it can be seen that the performance of the finished product in Example 1 is quite similar to that of Comparative Example 1. Compared with Comparative Example 1, Example 1 reduced the processing allowance, but its various performance characteristics did not decrease. In other words, compared with Comparative Example 1, the processing method of Example 1 can reduce production costs.

[0108] Comparing Example 1 and Comparative Example 2, it can be seen that, compared to Comparative Example 2 which did not involve grinding and secondary shot blasting, Example 1, with its secondary shot blasting and other treatments, improves surface properties and fatigue resistance. Surface properties are mainly reflected in surface defects such as cracks, inclusions, folds, and pits.

[0109] Comparing Example 1 and Comparative Example 3, it can be found that the glass lubricant prepared by the method in Example 1 is more preferred. It can better protect the titanium alloy and prevent oxidation from affecting the strength and toughness of the alloy, thereby improving the corresponding mechanical properties. Although the glass lubricant in Comparative Example 3 can play a protective role, its stability is slightly worse than that of the glass lubricant in Example 1.

[0110] Comparing Example 1 with Comparative Example 4, it can be seen that the different settings in Example 1 can further improve the various properties of titanium alloy. Specifically, the two annealing processes in Example 1 alleviate the internal stress generated during the forging process, preventing cracks or deformation in the material during subsequent processing. At the same time, it can refine the grains, thereby improving the microstructure and ductility of the metal, thus improving the overall performance of the material.

[0111] Comparing Examples 1, 2 and 3, it can be found that the components of Example 1 are more preferred.

[0112] Comparing Example 1 and Example 14, it can be found that Example 14 has a better microstructure and smaller crystal size, which helps to improve its elongation at break.

[0113] 2. Investigate the effects of different parameters on;

[0114] Comparisons were made between Examples 1 and Examples 4-13, as shown in Table 2;

[0115] Table 2 Performance test results of forged products under different parameter settings

[0116] parameter Tensile strength (MPa) Yield strength MPa Example 1 1350 1180 Example 4 1320 1146 Example 5 1322 1154 Example 6 1331 1137 Example 7 1335 1158 Example 8 1327 1167 Example 9 1325 1165 Example 10 1311 1147 Example 11 1326 1149 Example 12 1315 1170 Example 13 1314 1165

[0117] As can be seen from Table 2, comparing Examples 1, 4, and 5, it can be found that the parameters for the first forging in Example 1 are more preferred. This may be because the surface treatment during the first forging process can protect the titanium alloy surface, prevent oxidation, and thus improve the strength and toughness of the titanium alloy forging. Comparing Examples 1, 6, and 7, it can be found that the surface treatment parameters for Example 1 are more preferred. Comparing Examples 1, 8, and 9, it can be seen that the preparation parameters for the modified borosilicate glass lubricant in Example 1 are more preferred. This may be because the modified borosilicate glass lubricant obtained under the parameters of Example 1 has better anti-oxidation properties, resulting in better quality of the finished product obtained in Example 1. Comparing Examples 1, 10, and 11, it can be seen that the setting of the secondary forging parameters in Example 1 is more preferred, as the internal structure of the finished product is more uniform under these parameters. Comparing Examples 1, 12, and 13, it can be found that the annealing parameters of Example 1 are more preferred.

Claims

1. A die forging method for a high-strength, high-toughness, damage-tolerant titanium alloy cylindrical part, characterized in that, Includes the following steps: S1. Heating the raw materials: Take the titanium alloy forging, cut it, and then heat it to (T). β -50)±10℃, then hold at that temperature for 70~120min; to obtain the heated forging; wherein, T β The β-phase transformation temperature of titanium alloy forgings; S2, One-time forging: The heated forging material is placed in a forging die for forging. The hammering rate is 30-45 times / min, the forging time is 30-45 seconds, and the impact energy is 700-900 tons. Then it is air-cooled to 25°C to obtain the initial forging. S3. Surface treatment: After shot blasting, grinding, and shot blasting again, the initial forging is held at 120–150°C for 10–20 minutes. Then, the initial forging is removed and coated with glass lubricant. After the glass lubricant dries, it is heated until the initial forging reaches a temperature of (T). β The temperature is set at -50)±10℃, and then held for 75~150min to obtain the pre-forged part; S4, Secondary forging; The pre-forged part is placed into the finished product mold for forging. During the forging process, the impact energy is 1100-1250 tons, and then it is air-cooled to 500-550°C. After the forging is completed, the final forging part is obtained. S5, Annealing: The final forging is first annealed at 880-930°C for 145-155 minutes, and then air-cooled to 300-450°C to obtain the final forging after one annealing. The final forging after the first annealing is then subjected to a second annealing at 500-550°C for 235-245 minutes, and then air-cooled to 25°C to obtain the formed part. During the first annealing process, under normal pressure and a nitrogen atmosphere, the final forging is first heated to 880–930°C at a heating rate of 5–7°C / min, then held at that temperature for 145–155 min, and then cooled to 300–450°C at a cooling rate of 8–10°C / min. Simultaneously, a magnetic field with a strength of 20–50 Oe is applied, and the magnetic field strength decreases with the holding time at a rate of 0.1 Oe / min. After the holding time is complete and cooling begins, the magnetic field is turned off, and nitrogen is introduced to a pressure of 0.18–0.20 MPa until cooling is complete, at which point the pressure is adjusted to normal pressure. During the second annealing process, the pressure is first set at 0.22–… Under a nitrogen atmosphere at 0.30 MPa, the final forging after the first annealing is heated to 500–550°C at a heating rate of 8–10°C / min, then held at a constant temperature for 235–245 min, and then cooled to 25°C at a cooling rate of 4–6°C / min. Simultaneously, a magnetic field with a strength of 20–50 Oe is applied, and the magnetic field strength first increases and then decreases with the holding time. During the first 100 min of holding, the magnetic field strength increases at a rate of 0.15 Oe / min, and during the subsequent holding time, the magnetic field strength decreases at a rate of 0.1 Oe / min. After the holding time is completed, the magnetic field is turned off, the pressure is adjusted to atmospheric pressure, and then the temperature is lowered.

2. The die forging method for a high-strength, high-toughness, damage-tolerant titanium alloy cylindrical part as described in claim 1, characterized in that, The titanium alloy is TC21; T β The temperature ranges from 945 to 975℃.

3. The die forging method for a high-strength, high-toughness, damage-tolerant titanium alloy cylindrical part as described in claim 1, characterized in that, In S2, when the heated titanium alloy is placed in a forging die for forging, the placement time is 0.1 to 15 seconds.

4. The die forging method for a high-strength, high-toughness, damage-tolerant titanium alloy cylindrical part as described in claim 1, characterized in that, In S1, the titanium alloy forging is a shell forging; the diameter of the titanium alloy forging after cutting is 55-95% of that before cutting, and the height of the titanium alloy forging after cutting is 74-260% of that before cutting.

5. The die forging method for a high-strength, high-toughness, damage-tolerant titanium alloy cylindrical part as described in claim 4, characterized in that, In S1, the method for cutting and processing the titanium alloy forging is as follows: reducing the thickness of the machining allowance of the titanium alloy forging, increasing the height of the upper punch of the titanium alloy forging, increasing the length of the lower punch, and hollowing out the hole.

6. The die forging method for a high-strength, high-toughness, damage-tolerant titanium alloy cylindrical part as described in claim 1, characterized in that, In S3, the method for performing shot blasting, grinding, and shot blasting again on the initial forging is as follows: The first shot blasting uses steel balls with a particle size of 2-2.5 mm and a shot blasting speed of 60-70 m / s; the grinding uses a force of 120-150 grit and a grinding pressure of 5-15 N; the second shot blasting uses steel balls with a particle size of 0.5-1.5 mm and a shot blasting speed of 30-50 m / s.

7. The die forging method for a high-strength, high-toughness, damage-tolerant titanium alloy cylindrical part as described in claim 1, characterized in that, The thickness of the sprayed glass lubricant is 1-3 mm, and the glass lubricant used is a modified borosilicate glass lubricant.

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