A large-size titanium alloy rotating body forging method and forging die

Abstract

The present invention discloses a large-size titanium alloy rotary body forging method and forging die, and the large-size titanium alloy rotary body forging method includes: primary processing, flat die upsetting, pre-forging, pre-forging blank inner hole processing, and final forging. Primary processing can avoid bending during flat die upsetting, reduce the process rework rate, pre-forging makes the deformation dead zone of the upper and lower end faces of the workpiece realize small wavy deformation, with a deformation amount of about 10%-20%, and pre-forging blank inner hole processing further provides reverse flow space for the deformation of the blank in the deformation dead zone during the next final forging forming process, thereby improving the deformation dead zone during the forging process. The present invention also provides a large-size titanium alloy rotary body forging die, including a pre-forging die and a final forging die, and a wavy structure is designed at the deep groove of the cavity of the pre-forging upper die and the pre-forging lower die, which can make the deformation dead zone of the upper and lower end faces of the titanium alloy pre-forging blank obtained during the pre-forging process realize the first small wavy deformation, thereby solving the problem of deformation of the local blank during the forging forming process.

Description

Technical Field

[0001] The invention belongs to the field of plastic forming of titanium alloy materials, and particularly relates to a forging method and a forging die for a large-size titanium alloy rotating body. Background Art

[0002] The rotor forgings for large helicopter rotor systems are generally made of TB6 (Ti-10V-2Fe-3Al) titanium alloy, which has a low deformation temperature (nominal phase transition point 805℃) and high resistance. However, due to the large projected area of ​​the forging (above 0.75m2), large-sized bars (φ300-400mm) must be used on large-scale die forging equipment (above 400MN) to complete the forging in multiple steps, which makes the forming process more difficult. The conventional TB6 titanium alloy rotor forging forming process generally involves placing large-sized bars in a die and directly forming them through multiple steps (3 to 5 steps) of die forging. The developed forgings have large "deformation dead zones" on the upper and lower end faces. ， This process can easily lead to insufficient forging ratios (deformation ≤ 20%) from raw materials to forgings, resulting in poor uniformity and consistency in the forging's microstructure and mechanical properties. Specifically, these variations are manifested as follows: 1. The microstructure rating range at different locations is ≥ 2; 2. δ5 ≥ 10% and Ψ ≥ 40% for materials in high-deformation zones, while δ5 ≤ 8% and Ψ ≤ 30% for materials in low-deformation zones. This quality fluctuation, resulting from this conventional process, severely impacts the fatigue life of forgings, making it difficult to meet the development goals of lightweight, high-performance, and long-life advanced aircraft. Summary of the Invention

[0003] In view of this, the main purpose of the present invention is to provide a large-size titanium alloy rotating body forging method and forging die, which can solve the problem of large-area "deformation dead zone" on the upper and lower end faces of forgings in the prior art.

[0004] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0005] A method for forging a large-size titanium alloy rotating body, characterized by comprising the following steps:

[0006] Step 1: Pre-processing: Use a machine tool to mill the two ends of the initial bar material of the forging flat;

[0007] Step 2: Flat die upsetting: The initial bar is placed in a preheated flat die on a large hydraulic forging press and subjected to multiple upsetting processes until the total deformation of the bar in the height direction reaches 50%-60%, obtaining an upsetting blank.

[0008] Step 3: Pre-forging: placing the above-mentioned cake into a preheated pre-forging die on a large die forging hydraulic press and performing 1-2 passes of pre-forging to obtain a pre-forged billet;

[0009] Step 4: Processing the inner hole of the pre-forged billet, using cold working to process a through hole in the core of the pre-forged billet;

[0010] Step 5: final forging: placing the pre-forged blank obtained in step 4 in a preheated final forging die on a large die forging hydraulic press and performing final forging for 1-3 times to obtain a final forging blank.

[0011] Preferably, the method further comprises: thinning processing, performing cross-section thinning processing on the final forging blank obtained in step 5 by cold working;

[0012] Preferably, the method further comprises: heat treatment, performing solution treatment and aging treatment on the forging after thinning.

[0013] Preferably, during pretreatment, both end faces of the initial bar are milled flat so that the parallelism of the end faces is not greater than 0.5, and both end faces of the initial bar are rounded by R10-R30.

[0014] Preferably, during the flat die upsetting, pre-forging and final forging processes, the heating temperatures of the initial bar, pre-forging blank and final forging blank are all 750°C.

[0015] Preferably, before pre-forging, the pre-forging die is preheated at a temperature of 250-350°C.

[0016] Preferably, before final forging, the final forging die is preheated at a temperature of 250-350°C.

[0017] The present invention provides a method for forging a large-sized titanium alloy rotary body, comprising: primary processing, flat die upsetting, pre-forging, pre-forging inner hole processing, and final forging. Primary processing can avoid bending during flat die upsetting, reducing the process rework rate; pre-forging enables the "deformation dead zone" of the upper and lower end faces of the workpiece to achieve small, wavy deformation, with a deformation amount of about 10%-20%, and provides a pre-forged blank for the final forging of the blank; the pre-forging inner hole processing further provides reverse flow space for the deformation of the blank in the "deformation dead zone" during the next final forging process. Through the present invention's method for forging a large-sized titanium alloy rotary body, the forging is uniformly deformed, the "deformation dead zone" during the forging process is improved, and a large-sized titanium alloy forging whose size meets the design requirements is obtained.

[0018] The present application also discloses a large-size titanium alloy rotating body forging die, including a pre-forging die and a final forging die. The pre-forging die includes: a pre-forging upper die and a pre-forging lower die. The shape of the cavity obtained after the pre-forging upper die and the pre-forging lower die are combined is consistent with the shape of the pre-forging blank.

[0019] The final forging die comprises a final forging upper die and a final forging lower die. The shape of the cavity obtained after the final forging upper die and the final forging lower die are combined is consistent with the shape of the final forging blank.

[0020] The pre-forging upper die and the pre-forging lower die both adopt an open die design. The closed gap L1 of the pre-forging upper die and the pre-forging lower die after closing should be 10-20 mm larger than the gap L2 of the final forging upper die and the final forging lower die after closing.

[0021] A pre-forging upper die wave structure is provided at the deep groove of the cavity of the pre-forging upper die, and a pre-forging lower die wave structure is provided at the deep groove of the cavity of the pre-forging lower die.

[0022] Preferably, the height difference L3 between the crest and trough of the wave structure of the pre-forging upper die is 40-60 mm, the height difference L4 between the crest and trough of the wave structure of the pre-forging lower die is 40-60 mm, the maximum diameter D1 of the pre-forging die cavity is 100-120 mm smaller than the maximum diameter D2 of the final forging die cavity, and the total groove depth h1 of the pre-forging die is 40-60 mm deeper than the total groove depth h2 of the final forging die.

[0023] The large-size titanium alloy rotary body forging die of the present invention has the following beneficial effects:

[0024] Both the upper and lower pre-forging dies utilize an open die design to prevent the titanium alloy billet from flowing out of the pre-forging die cavity, which would otherwise result in billet waste. A wave-like structure is designed in the deep grooves of the cavities of the upper and lower pre-forging dies. This allows the "deformation dead zones" on the upper and lower end surfaces of the titanium alloy billet obtained during the pre-forging process to achieve a wave-like initial small deformation of approximately 10%-20%. This provides a pre-forged billet for the final forging process, solving the problem of local billet deformation during the forging process. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 The figure is a flow chart of a method for forging a large-sized titanium alloy rotating body;

[0027] Figure 2 A schematic diagram of a method for forging a large-sized titanium alloy rotating body;

[0028] Figure 3 Schematic diagram of a large-sized titanium alloy rotor forged using a conventional forging method;

[0029] Figure 4 for Figure 3 Metallographic diagrams of the deformation dead zone and large deformation zone shown;

[0030] Figure 5Schematic diagram comparing the profile of the pre-forging billet and the profile of the final forging billet;

[0031] Figure 6 It is a schematic diagram of the structure of the pre-forging upper die and the pre-forging lower die;

[0032] Figure 7 This is a schematic diagram of the structure of a large-sized titanium alloy rotating body;

[0033] Figure 8 The low-magnification organization diagrams of different positions of a real object forged by the forming method provided in the embodiment are as follows;

[0034] Figure 9 The figures show the microstructures of various locations of a real object forged by the forming method provided in the embodiment.

[0035]

Main component symbol description

[0036] 1. Initial bar stock; 2. Flat die; 3. Upsetting blank; 4. Pre-forging upper die; 5. Pre-forging blank; 6. Pre-forging lower die; 7. Through hole; 8. Final forging upper die; 9. Final forging blank; 10. Final forging lower die; 11. Large deformation zone; 12. Deformation dead zone; 13. Wave structure of pre-forging upper die; 14. Wave structure of pre-forging lower die; 15. Hub; 16. Spoke; 17. Rim. DETAILED DESCRIPTION

[0037] The large-size titanium alloy rotating body forging method and forging die of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments of the present invention.

[0038] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0039] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0040] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can, for example, be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0041] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used herein to describe the spatial positional relationship of a device or feature to other devices or features as shown in the figures. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figures. For example, if the device in the drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0042] See Figures 1-9 The present invention provides a technical solution: a method for forging a large-size titanium alloy rotating body, comprising the following steps:

[0043] Step 1: Pre-processing: Use a machine tool to flatten the end faces of the initial forging bar 1. Flattening the end faces can effectively prevent bending of the bar during the next process and reduce the rework rate.

[0044] Step 2: Flat die upsetting: Place the initial bar 1 in a preheated universal flat die 2 on a large die forging hydraulic press and perform multiple upsetting processes to make the total deformation of the initial bar 1 in the height direction reach 50%-60%, to form an upsetting blank 3.

[0045] Step three, pre-forging, placing the upsetting cake blank 3 in a preheated pre-forging die on a large die forging hydraulic press for 1-2 passes of pre-forging to obtain a pre-forged blank 5, so that the "deformation dead zone" of the upper and lower end faces achieves a small wave-like deformation with a deformation amount of about 10%-20%, providing a pre-forged blank for the final forging of the blank.

[0046] Step 4: Processing the inner hole of the pre-forged billet. A through hole 7 is processed in the center of the pre-forged billet 5 by cold working. The diameter of the through hole is 50-80 mm, which further provides reverse flow space for the deformation of the billet in the "deformation dead zone" during the next final forging process.

[0047] Step 5, final forging, places the pre-forged billet 5 obtained in step 4 into a preheated final forging die on a large die forging hydraulic press for 1-2 passes of final forging, so that the pre-forged billets at different positions are uniformly deformed, and a large-sized titanium alloy rotating body forging with a size that meets the design requirements is obtained.

[0048] Step six, thinning processing, uses cold working to perform cross-sectional thinning processing on the final forging blank 9 obtained in step five, so as to maximize the hardenability of the material in the next solid solution heat treatment process of the forging without affecting the processing of the parts, and improve the material strength at different thickness positions of the forging; during the thinning processing, the burrs of the forging generated at the terminal will be removed.

[0049] Step seven: heat treatment, solution treatment and aging treatment are performed on the forgings after thinning.

[0050] In order to facilitate the use of flat die upsetting cakes, during pretreatment, the two end faces of the initial bar 1 are milled flat so that the parallelism of the two end faces is not greater than 0.5, and the two end faces of the initial bar 1 are rounded R10-R30.

[0051] During the flat die upsetting, pre-forging and final forging processes, the heating temperature of the initial bar 1, the pre-forging blank 5 and the final forging blank 9 is 750°C.

[0052] Before pre-forging, the pre-forging die is preheated at a temperature of 250-350°C.

[0053] Before final forging, the final forging die is preheated at a temperature of 250-350°C. The present invention provides a large-size titanium alloy rotary body forging die, comprising a pre-forging die and a final forging die, wherein the pre-forging die comprises: a pre-forging upper die 4 and a pre-forging lower die 6, wherein the shape of the cavity obtained after the pre-forging upper die 4 and the pre-forging lower die 5 are combined is consistent with the shape of the pre-forging blank 5;

[0054] The final forging die includes a final forging upper die 8 and a final forging lower die 10 . The shape of the cavity obtained after the final forging upper die 8 and the final forging lower die 10 are combined is consistent with the shape of the final forging blank 9 .

[0055] Both the pre-forging upper die 4 and the pre-forging lower die 6 adopt an open die design, without a bridge or hopper. This prevents the presence of the bridge and hopper from increasing the flow resistance of the billet during pre-forging. The closed gap L1 between the pre-forging upper die 4 and the pre-forging lower die 6 should be 10-20 mm larger than the closed gap L2 between the final forging upper die 8 and the final forging lower die 10. Increasing the closed gap between the pre-forging dies prevents the titanium alloy billet from flowing out of the pre-forging die cavity, which would otherwise result in billet waste.

[0056] A pre-forging upper die wave structure 13 is provided at the deep groove of the cavity of the pre-forging upper die 4, and a pre-forging lower die wave structure 14 is provided at the deep groove of the cavity of the pre-forging lower die 6. The height difference L3 between the wave crest and the wave trough of the pre-forging upper die wave structure 13 is 40-60mm, and the height difference L4 between the wave crest and the wave trough of the pre-forging lower die wave structure 14 is 40-60mm. The wave-like structure is designed at the deep groove of the cavity of the pre-forging upper die 4 and the pre-forging lower die 6, which can make the "deformation dead zone" of the upper and lower end faces of the titanium alloy pre-forging blank 5 obtained in the pre-forging process achieve a wave-like first small deformation, with a deformation amount of about 10%-20%, and provide a pre-forging blank for the final forging of the blank, solving the problem of deformation of the local blank during the forging process.

[0057] The maximum diameter D1 of the pre-forging die cavity is 100-120mm smaller than the maximum diameter D2 of the final forging die cavity, and the total groove depth h1 of the pre-forging die is 40-60mm deeper than the total groove depth h2 of the final forging die. Through pre-forging and final forging, the bar is gradually forged into a rotating body with a larger diameter and a smaller height, and the problem of deformation dead zones in forgings during the forging process is solved.

[0058] Example

[0059] In order to make the purpose, technical solutions and advantages of the present invention clearer, the forging method will be described below in conjunction with embodiments.

[0060] Large-scale rotor forgings for large helicopter rotor systems have a large projected area, typically exceeding 0.75 m². These large-scale titanium alloy rotors are typically manufactured from large-gauge TB6 (Ti-10V-2Fe-3Al) titanium alloy bars (φ300-400 × 1000-1200 mm). The present invention will now be described in further detail, using the example of a large-scale titanium alloy rotor forging with outer dimensions of φ960 × 275 mm, weighing approximately 411 kg and made of TB6.

[0061] First, a TB6 titanium alloy initial bar with a size of φ350×1020mm was used. The end faces were milled flat using a machine tool to make the parallelism no greater than 0.5, and the corners of both end faces were rounded to R10-R30.

[0062] Then, following the flat die upsetting method of step two, a large hydraulic forging press was used to heat the titanium alloy bar from the previous pass according to the established process parameters using a universal flat die. The result was a round titanium alloy forging blank, Upset Blank 3, which was 440 mm in height and 56% of the initial bar height. Table 1 lists the forging process parameters for the flat die upsetting process.

[0063] Table 1 Process parameters of flat die upsetting cake

[0064]

[0065] Next, the preform was heated on a large hydraulic die forging press according to the process parameters shown in Table 2 and placed in a preheated (preheating temperature 250-350°C, preheating time ≥12 hours) preforging die for two passes to obtain a preforged billet 5 for a large-sized titanium alloy rotary forging. Table 2 lists the forging process parameters for this preforging process.

[0066] Table 2 Pre-forging process parameters

[0067]

[0068] Then, in combination with the overall hollow structural design of the large-sized titanium alloy rotating body component, a through hole 7 with a diameter of φ60 is processed in the center of the pre-forged billet 5 obtained above by cold working, and a chamfer R15 is set at the transition.

[0069] Next, the resulting pre-forged blank 5 containing an inner hole was heated on a large hydraulic die forging press according to the process parameters shown in Table 3. The blank was then placed in a preheated (preheating temperature 250-350°C, preheating time ≥12 hours) final forging die forging in two passes to obtain the final forged blank 9. Table 3 lists the forging parameters for the final forging process.

[0070] Table 3 Final forging process parameters

[0071]

[0072] Then, the cross-section of the forging obtained above is thinned by cold working to maximize the hardenability of the forging in the next solution heat treatment process without affecting the part processing; if burrs are generated at the end, the burrs should be removed.

[0073] Finally, the forgings after thinning are subjected to solution treatment and aging treatment according to the following heat treatment system:

[0074] a) Heat at 760±10℃ for 120min and then cool in water;

[0075] b) Heat at 513±5℃ for 500min, then remove from the furnace and air cool.

[0076] Figure 8 In order to forge the low-magnification organization diagram of different positions of the object by using the forming method provided in the embodiment, Figure 8 It can be seen that there are no defects such as bright lines, inclusions, and delamination in the low-magnification microstructure of the forging as a whole (a), the small deformation zone (b), and the large deformation zone (c). They all meet the level 2-3 requirements of the low-magnification microstructure of TB6 titanium alloy in the standard GJB 2744A-2019, and are qualified organizations. There is no difference in the low-magnification microstructure in different areas of the forging.

[0077] from Figure 9 It can be seen that the microstructures of the small deformation zone (ac) and the large deformation zone (df) of the forging are composed of aged β matrix and spherical primary α phase. All β original grain boundary α phases are completely broken, and there is no continuous, flat grain boundary α phase network and coarse grain boundary α structure. They all meet the level 2 requirements of the TB6 titanium alloy microstructure atlas in the standard GJB 2744A-2019, are qualified organizations, and the organization rating difference is 0.

[0078] Figure 3 The figure shows a schematic diagram of a large-sized titanium alloy rotating body forged by a conventional forging method, wherein the large deformation zone 11 is located at the edge and the deformation dead zone 12 is located at the core;

[0079] Figure 4 for Figure 3 The metallographic diagram of the deformation dead zone and large deformation zone is shown, where Figure 4 (b) is the metallographic image of the large deformation zone. It can be seen that the structure of the large deformation zone is relatively uniform, and the primary α phase is spheroidized. Figure 4 (a) is the metallographic image of the deformation dead zone. The primary α phase in the local position of the deformation dead zone is not fully spheroidized and is strip-shaped, with large differences.

[0080] By comparison, it is shown that the macrostructure of the forgings developed by the forming method of the present invention has no metallurgical defects, good streamlines, and consistent macrostructure uniformity in the large deformation zone and the small deformation zone; the microstructures at multiple positions of the forgings meet the standard requirements of the forgings and are highly uniform and consistent.

[0081] Table 4 shows the room temperature tensile strength, fracture toughness and other properties of the forged wheel hub 15, spoke 16 and rim 17 obtained in the above embodiment. All properties meet the requirements of relevant technical conditions. It can be seen that the material δ5 ≥ 12% and Ψ ≥ 55% at different positions of the forging developed by the forming method of this method are highly uniform.

[0082] Table 4 Properties of forgings at different positions

[0083]

[0084] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention.

Claims

1. A method for forging a large-size titanium alloy rotating body, characterized in that: The following steps are involved: Step 1: Pre-processing: using a machine tool to flatten the two end faces of the initial bar material (1) of the forging; Step 2: Flat die upsetting, placing the initial bar material (1) in a preheated flat die (2) on a large die forging hydraulic press and performing multiple upsetting processes, so that the total deformation of the initial bar material (1) in the height direction reaches 50%-60%, thereby obtaining an upsetting blank (3); Step 3: Pre-forging: placing the upset blank (3) in a preheated pre-forging die on a large die forging hydraulic press for 1-2 passes of pre-forging forming, so that the "deformation dead zone" of the upper and lower end faces realizes a small wave-like deformation, with a deformation amount of 10%-20%, and the height difference L3 between the wave crest and the wave trough of the pre-forging upper die wave structure (13) is 40-60 mm, and the height difference L4 between the wave crest and the wave trough of the pre-forging lower die wave structure (14) is 40-60 mm, thereby obtaining a pre-forged blank (5); Step 4: Processing the inner hole of the pre-forged billet, using a cold working method to process a through hole (7) in the center of the pre-forged billet (5), wherein the diameter of the through hole (7) is 50-80 mm, and the through hole (7) provides a reverse flow space for the deformation of the billet in the "deformation dead zone" during the next final forging process; Step 5, final forging, placing the pre-forged blank (5) obtained in step 4 in a preheated final forging die on a large die forging hydraulic press to perform final forging for 1-2 passes to obtain a final forging blank (9).

2. The method for forging a large-size titanium alloy rotating body according to claim 1, characterized in that: Also includes: Thinning processing, using cold working method to perform cross-section thinning processing on the final forging blank (9).

3. The method for forging a large-size titanium alloy rotating body according to claim 1, characterized in that: Also includes: Heat treatment, solution treatment and aging treatment of forgings after thinning.

4. The method for forging a large-size titanium alloy rotating body according to claim 1, characterized in that: During pretreatment, both end faces of the initial bar material (1) are milled flat so that the parallelism of the end faces is not greater than 0.5, and both end faces of the initial bar material (1) are rounded to R10-R30.

5. The method for forging a large-size titanium alloy rotating body according to claim 1, characterized in that: During the flat die upsetting, pre-forging and final forging processes, the heating temperature of the initial bar (1), the pre-forging billet (5) and the final forging billet (9) is 750°C.

6. The method for forging a large-size titanium alloy rotating body according to claim 1, characterized in that: Before pre-forging, the pre-forging die is preheated at a temperature of 250-350°C.

7. The method for forging a large-size titanium alloy rotating body according to claim 1, wherein: Before final forging, the final forging die is preheated at a temperature of 250-350°C.

8. The method for forging a large-size titanium alloy rotating body according to claim 1, wherein: The maximum diameter D1 of the pre-forging die cavity is 100-120 mm smaller than the maximum diameter D2 of the final forging die cavity, and the total groove depth h1 of the pre-forging die is 40-60 mm deeper than the total groove depth h2 of the final forging die.

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