A method for manufacturing a TA15 titanium alloy die forging based on a cast blank

Abstract

The application discloses a TA15 titanium alloy die forging manufacturing method based on a casting blank and belongs to the technical field of titanium alloy processing. The method comprises the following steps: preparing an intermediate blank by adopting a vacuum centrifugal casting method; and after the intermediate blank is sequentially subjected to heating, forging and annealing treatment, a TA15 titanium alloy die forging is obtained. The application is characterized in that the advantages of a casting process and a forging process are complementary, a designed blank shape and size are obtained by adopting a casting blank preparation mode, and a forging is pressed into a final size through a few heating times and a large deformation forming mode on a die. Compared with a traditional forging forming scheme, the mode can effectively reduce a feeding weight, reduce forging heating times, and ensure that the performance of the forging meets the requirements. In addition, compared with a forging blank preparation mode, the adoption of the casting blank preparation mode can greatly reduce a feeding amount, improve a forging material utilization rate, and reduce a forging development cost.

Description

Technical Field

[0001] This invention belongs to the field of titanium alloy processing technology, specifically relating to a method for manufacturing TA15 titanium alloy die forgings based on cast blanks. Background Technology

[0002] The nominal composition of TA15 titanium alloy is Ti-6.5Al-2Zr-1Mo-1V. Its main strengthening mechanism is solid solution strengthening through the α-stabilizing element Al, while the addition of neutral element Zr and β-stabilizing elements Mo and V improves its processing properties. This alloy has an Al equivalent of 6.58% and a Mo equivalent of 2.46%, classifying it as a high-Al-equivalent near-α-type titanium alloy. Therefore, it possesses both the good heat resistance and weldability of α-type titanium alloys and the processing plasticity close to that of α-β-type titanium alloys. Its excellent comprehensive properties and mature machining processes make this alloy one of the main materials used in domestic aircraft structural components.

[0003] As the industry develops, the market demand for TA15 titanium alloy continues to increase, and the need for low-cost manufacturing is becoming increasingly prominent. In previous product development processes, it was found that the material utilization rate of some complex-shaped forgings was low. The ratio of the final forging weight to the raw material weight was even less than 60%, indicating that material loss was extremely high during the forging process. The main reason for this is that complex-shaped forgings require multiple heating processes to ensure that the final formed dimensions meet design requirements, and pre-form blanks of the required dimensions need to be produced. Currently, there are two main methods for pre-forming blanks: one is to pre-form blanks using a high-speed forging mill or free forging hammer, and the other is to use a set of pre-formed molds. Both methods have the same problem: not only are there many heating processes for forging, and each process results in material loss, but the shape and dimensional accuracy of the blanks achievable using presses or forging hammers is not high. This is the main reason for the low material utilization rate of complex forgings. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a method for manufacturing TA15 titanium alloy forgings based on cast blanks, so as to solve the technical problems of low material utilization, long development process and high manufacturing cost of TA15 titanium alloy forgings in the existing technology.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for manufacturing TA15 titanium alloy die forgings based on cast billets includes: preparing intermediate billets using vacuum centrifugal casting; and sequentially heating, forging, and annealing the intermediate billets to obtain TA15 titanium alloy die forgings.

[0006] Specifically, the method includes the following steps: Step 1: Prepare intermediate billet using vacuum centrifugal casting: In a vacuum environment, use electric arc melting of TA15 titanium alloy consumable electrode until a molten pool is formed, then start centrifugation to establish a stable centrifugal force field; then smoothly fill the mold cavity with molten metal, and continue centrifugation until the casting is completely solidified; then cool in a vacuum environment, remove the intermediate billet from the furnace and place it in the air to cool naturally.

[0007] Step 2, heating the intermediate billet: Place the intermediate billet obtained in Step 1 in an electric furnace, and start calculating the holding time after the temperature reaches the preset temperature.

[0008] Step 3, intermediate billet forging: The intermediate billet heated in step 2 is transferred to the forging equipment, and the forging parameters are set before forging; the temperature of the forging is monitored in real time during the forging process; and the forging is cooled naturally in the air after forging.

[0009] Step four, annealing treatment; first, the forging obtained in step three is subjected to ordinary annealing, and then naturally cooled in air; then the forging is subjected to stress-relief annealing, and then naturally cooled in air.

[0010] The present invention also has the following technical features: Specifically, in step one, the vacuum level of the vacuum environment is ≤5Pa.

[0011] Specifically, in step one, the melting temperature is 1650–1750°C. Preferably, the melting temperature is 1700°C.

[0012] Specifically, in step one, the centrifugation speed is 80–120 r / min. Preferably, the centrifugation speed is 100 r / min.

[0013] Specifically, in step one, the filling time is 5 to 10 seconds.

[0014] Specifically, in step one, the temperature is cooled to 500–600°C in a vacuum environment.

[0015] Specifically, in step two, the heating temperature is 25–45°C below the β-phase transformation point of TA15 titanium alloy, and the holding coefficient is 0.5–0.7 min / mm. Preferably, the heating temperature is 35°C below the β-phase transformation point of TA15 titanium alloy, and the holding coefficient is 0.6 min / mm.

[0016] Specifically, in step three, the transfer time should be controlled within 30 seconds.

[0017] Specifically, in step three, the forging parameters are as follows: pressing rate is 2-5 mm / s, die preheating temperature is 250-350℃, and under-pressurization is no more than 1 mm. Preferably, the die preheating temperature is 300℃.

[0018] Specifically, in step three, the final forging temperature of the forging is greater than 850℃.

[0019] Specifically, in step four, the conditions for ordinary annealing are: annealing temperature of 780–820℃ and holding time of 2–3 hours; the conditions for stress-relief annealing are: annealing temperature of 550–620℃ and holding time of 2–3 hours. Preferably, the conditions for ordinary annealing are: annealing temperature of 850℃ and holding time of 2 hours; the conditions for stress-relief annealing are: annealing temperature of 580℃ and holding time of 2 hours.

[0020] Compared with the prior art, the present invention has the following technical effects: (I) This invention combines the advantages of casting and forging processes. It uses casting to prepare the designed billet shape and size, and then uses a low-heat, high-deformation forming method on a mold to press the forging into its final size. Compared with traditional forging methods, this method effectively reduces the amount of raw material, reduces the number of forging heats, and ensures that the forging's performance meets requirements. Furthermore, compared to forging, casting significantly reduces the amount of raw material, improves material utilization, and lowers the forging development cost.

[0021] (II) Simultaneously, this invention combines the advantages of casting and forging processes. Casting offers the advantages of manufacturing complex-shaped components, high material utilization, and low cost; forging refines grains through plastic deformation, resulting in a denser internal structure, improved overall material performance, and higher reliability of forgings. The combination of these two processes enables the product to possess the advantages of high material utilization, excellent overall performance, and low manufacturing cost. Furthermore, this invention can fully utilize recycled materials. In previous forging development, bars or slabs were commonly used for forging manufacturing. The development of bars or slabs, as well as the forging process itself, generates scrap, machining waste, burrs, and inspection residue. This method can fully utilize these residual materials in the casting and billet preparation stage, thereby further reducing development costs.

[0022] (III) This invention has the advantages of short process and high efficiency in manufacturing. Compared with casting, manufacturing complex-shaped forgings using bar stock requires more heating cycles and a longer cycle. Casting can not only reduce the forging cycle, but also significantly reduce the raw material preparation cycle, making it suitable for mass production and offering advantages of stable cycle time and high-efficiency manufacturing. The process of developing forgings using casting is simple, with a short manufacturing cycle, making it more suitable for mass production of forgings.

[0023] (IV) This invention makes the microstructure and properties of forgings more uniform. Casting involves designing a blank that conforms to the dimensions and shape of the forging, resulting in more consistent deformation in different parts during forging, which is more conducive to controlling the uniformity of the microstructure and properties of the forging. Forgings developed using casting not only meet the technical specifications in terms of mechanical properties and metallographic structure, but also exhibit better uniformity. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the cross-section of a TA15 titanium alloy forging. Figure 1 In the middle: the thin solid line is a schematic diagram of the cross-section of the forging.

[0025] Figure 2 This is a schematic diagram of TA15 titanium alloy forgings and castings. Figure 2 In the middle: the thin solid line is a schematic diagram of the cross-section of the forging, and the thick solid line is a schematic diagram of the casting billet.

[0026] Figure 3 The low-magnification microstructure of the TA15 titanium alloy forging.

[0027] Figure 4 The microstructure of TA15 titanium alloy forgings.

[0028] The specific content of the present invention will be further explained in detail below with reference to the embodiments.

[0029] Specific implementation methods It should be noted that, unless otherwise specified, the raw materials and equipment mentioned in this invention are all known in the art.

[0030] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0031] Example 1 This embodiment provides a TA15 titanium alloy forging, such as Figure 1 and Figure 2 As shown, its structure is similar to a T-beam. The forging has an outer dimension of 200×50×27 (mm), and the rib thickness is a uniform 2mm. It is a load-bearing component on the inner side of a thin plate forging. To ensure the reliability of the component, high requirements are placed on the streamline direction, strength, and toughness. The material selected is a TA15 titanium alloy die forging. The forging has a uniform 3mm allowance on one side and a draft angle of 5°.

[0032] Example 2 This embodiment provides a design method for a TA15 titanium alloy forging as described in Embodiment 1. The method includes the following steps: Step 1, Forging Design: Design the forging according to its shape and dimensions. Select the crossbar as the parting surface. The forging should maintain a conformal design, with uniform allowance. The intersection of the horizontal and vertical sections should have an R10 angle, and the remaining sections should have an R1 angle. The single-sided allowance and tolerance accuracy requirements should conform to the forging design specifications.

[0033] Step two, intermediate billet design: Using numerical simulation technology, intermediate billets are designed based on the shape and size of the forging. Based on the characteristics of typical parts, Deform numerical simulation software is used to simulate the stress-strain conditions, filling conditions, and temperature field during the forging process. The designed billet dimensions should meet the requirements of single-fire forging and deformation of at least 30% in different parts of the forging process. When designing the intermediate billet, a furnace test sample should be included to detect the phase transformation point T. β Once the intermediate billet design is complete, casting can begin. The specific casting method will depend on the actual conditions of the product.

[0034] Example 3 This embodiment provides a method for manufacturing TA15 titanium alloy forgings based on cast billets, used to manufacture the TA15 titanium alloy forgings of Example 1. The method includes the following steps: Step 1: Prepare intermediate billets using vacuum centrifugal casting: Evacuate the vacuum solidification furnace to a high vacuum state of ≤5Pa, use an electric arc to heat the TA15 consumable electrode, and form a molten metal pool after the TA15 consumable electrode melts. The melting temperature is controlled at 1700℃. After the molten pool is formed, start the centrifuge and rotate it to 100r / min to establish a stable centrifugal force field. Use the bottom injection method, with the molten metal temperature not lower than 1700℃, and smoothly fill the mold cavity, completely filling it in 5-10 seconds. After filling, continue to maintain a centrifugal speed of 100r / min until the casting is completely solidified, then stop the centrifugal rotation. Then, slowly cool it in a vacuum environment until the temperature drops below 600℃, remove the intermediate billet from the furnace, and allow it to cool naturally to room temperature in air.

[0035] In this embodiment, the weight of the intermediate billet is 0.74 kg / piece, and its phase transformation point is tested. The measured phase transformation point temperature is 995℃.

[0036] Step 2, heating the intermediate billet: Place the intermediate billet obtained in Step 1 in an electric furnace (the heating accuracy of the electric furnace used must be controlled within ±10℃). When the temperature reaches 960℃ (i.e. 35℃ below the β phase transformation point), start calculating the holding time, which is 60min.

[0037] As a specific embodiment, the holding time is calculated using the following formula: t1 = η1 × δmax; where: t1 represents the holding time in minutes; δmax is the effective cross-sectional thickness of the billet in mm; and η1 is the heating coefficient, which is 0.6 min / mm. In this embodiment, since the typical part has a small cross-sectional thickness, the holding time is directly set to 60 minutes.

[0038] Step 3, Intermediate Billet Forging: The intermediate billet heated in Step 2 is quickly transferred to the forging equipment (a hydraulic press is used in this embodiment). The transfer time must be controlled within 30 seconds. The forging parameters are set as follows: press pressing speed is 2-5 mm / s, die preheating temperature is 300℃, and under-pressurization is ≤1 mm. During the forging process, the temperature of the forging is monitored continuously. The final forging temperature of the forging is greater than 850℃, and the forging is allowed to cool naturally to room temperature in air after forging.

[0039] Step four, annealing: Considering the control of machining deformation, a combination of ordinary annealing and stress-relieving annealing is adopted. First, the forging obtained in step three is held at 850℃ for 2 hours, then air-cooled to room temperature; then, the forging is held at 580℃ for 2 hours, and then air-cooled to room temperature. The final forging weight is approximately 0.68 kg.

[0040] In this embodiment, the forgings obtained in step four are subjected to physical and chemical tests. The tests include low-magnification microstructure, microstructure, room temperature tensile properties and impact properties in the longitudinal, transverse and height directions. The measured data in this embodiment are shown in Table 1.

[0041] Table 1. Measured data from Example 3

Claims

1. A method for manufacturing TA15 titanium alloy forgings based on cast billets, characterized in that, The method includes: preparing an intermediate billet using a vacuum centrifugal casting method; and subjecting the intermediate billet to sequential heating, forging, and annealing treatments to obtain a TA15 titanium alloy die forging.

2. The method for manufacturing TA15 titanium alloy forgings based on cast billets as described in claim 1, characterized in that, The method includes the following steps: Step 1: Prepare intermediate billet using vacuum centrifugal casting: In a vacuum environment, use electric arc melting of TA15 titanium alloy consumable electrode until a molten pool is formed, then start centrifugation to establish a stable centrifugal force field; then smoothly fill the mold cavity with molten metal, and continue centrifugation until the casting is completely solidified; then cool in a vacuum environment, remove the intermediate billet from the furnace and place it in the air to cool naturally; Step 2, heating the intermediate billet: Place the intermediate billet obtained in Step 1 in an electric furnace, and start calculating the holding time after the temperature reaches the preset temperature. Step 3, intermediate billet forging: The intermediate billet heated in Step 2 is transferred to the forging equipment, and the forging parameters are set before forging; the temperature of the forging is monitored in real time during the forging process; and the forging is cooled naturally in the air after forging. Step four, annealing treatment; first, the forging obtained in step three is subjected to ordinary annealing, and then naturally cooled in air; then the forging is subjected to stress-relief annealing, and then naturally cooled in air.

3. The method for manufacturing TA15 titanium alloy forgings based on cast billets as described in claim 2, characterized in that, In step one, the vacuum level of the vacuum environment is ≤5Pa.

4. The method for manufacturing TA15 titanium alloy forgings based on cast billets as described in claim 2, characterized in that, In step one, the melting temperature is 1650–1750℃.

5. The method for manufacturing TA15 titanium alloy forgings based on cast billets as described in claim 2, characterized in that, In step one, the centrifugation speed is 80-120 r / min.

6. The method for manufacturing TA15 titanium alloy forgings based on cast billets as described in claim 2, characterized in that, In step one, the filling time is 5 to 10 seconds.

7. The method for manufacturing TA15 titanium alloy forgings based on cast billets as described in claim 2, characterized in that, In step one, the temperature is cooled to 500–600°C in a vacuum environment.

8. The method for manufacturing TA15 titanium alloy forgings based on cast billets as described in claim 2, characterized in that, In step two, the heating temperature is 25–45°C below the β phase transformation point of TA15 titanium alloy, and the heat preservation coefficient is 0.5–0.7 min / mm.

9. The method for manufacturing TA15 titanium alloy forgings based on cast billets as described in claim 2, characterized in that, In step three, the forging parameters are as follows: pressing rate is 2-5 mm / s, die preheating temperature is 250-350℃, and under-pressurization is no more than 1 mm.

10. The method for manufacturing TA15 titanium alloy forgings based on cast billets as described in claim 2, characterized in that, In step four, the conditions for ordinary annealing are: annealing temperature of 780-820℃ and holding time of 2-3h; the conditions for stress-relief annealing are: annealing temperature of 550-620℃ and holding time of 2-3h.

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