Hollow shaft forging method

Abstract

The present application relates to a hollow shaft forging method. The method comprises: a blanking process: providing a blank; a pre-forging process: heating the blank to a temperature within a first predetermined temperature range and holding for a first predetermined period, and transferring the heated blank to a die subjected to a first preheating operation and performing one or more times of upsetting and drawing operation on the blank to obtain a pre-forging piece; and a finish-forging process: performing a 1-fire 2-step operation on the pre-forging piece to obtain a finish-forging piece, including heating the pre-forging piece to a temperature within a second predetermined temperature range and holding for a second predetermined period during 1-fire, and transferring the heated pre-forging piece to a die subjected to a second preheating operation and performing 2 steps, the 2 steps including a first step and a second step, the first step causing a first upper punch of the die to be pressed down to complete the forging of an external profile of the hollow shaft, and the second step causing a second upper punch of the die to be pressed down to complete the forging of an internal profile of the hollow shaft.

Description

Technical Field

[0001] This invention relates to the field of machining and manufacturing, and more specifically to a method for forging hollow shafts. Background Technology

[0002] In the mechanical field, hollow shafts are a very common type of component. For some large-sized hollow shafts (especially those with relatively complex configurations), their manufacturing places extremely stringent requirements on equipment and process control. For example, in high-bypass turbofan engines, as the bypass ratio of commercial engines increases, engine performance improves, and the demands for reliability and economy also rise. As the size and complexity of component configurations increase, the performance requirements for compressor disc components also increase. Therefore, the performance requirements for forgings also increase.

[0003] Currently, C250 steel is commonly used for fan shaft forgings in domestic narrow-body passenger aircraft engines and military aircraft. The main processes used are a combination of free forging and die forging, which form the large end and rod section of the fan shaft forging, respectively. The fan shaft of a commercial wide-body passenger aircraft engine has a trumpet-shaped hollow structure, with a total length of approximately 860 mm. The maximum outer diameter of the large end is approximately 430 mm, the minimum inner diameter of the small end is approximately 110 mm, and the overall wall thickness is approximately 10-50 mm. To reduce the weight of wide-body passenger aircraft engines, internationally advanced wide-body engines use titanium alloys, such as Ti-6Al-4V alloy, for their fan shafts. For wide-body passenger aircraft engines, using Ti-6Al-4V alloy instead of C250 alloy can reduce the weight of the fan shaft by approximately 50%.

[0004] However, for complex hollow shaft components, such as fan shafts, which are long, flared (with one end larger than the other), and have thick conical walls, die forging requires extremely strict control over equipment, forging temperature, and time. Furthermore, Ti-6Al-4V alloy has lower thermoplasticity than C250, and excessive deformation can lead to deep surface cracks. The die forging process places high demands on the heat preservation and lubrication of the billet. Titanium alloys have poorer plastic deformation than stainless steel and lower metal fluidity, which may cause uneven material deformation along the axial direction. Excessive deformation can lead to instability, while insufficient deformation may prevent recrystallization, resulting in poor or substandard performance. The complexity of the structure may also cause uneven deformation in different areas of the forging or the appearance of deformation dead zones in localized areas, leading to inconsistencies in mechanical properties and microstructure.

[0005] Therefore, there is a need in the art for shaft forging methods to improve deformation uniformity. Summary of the Invention

[0006] To address the aforementioned problems in the prior art, the present invention provides a method for forging hollow shaft components, comprising: a blanking step: providing a billet; a pre-forging step: heating the billet to a temperature within a first predetermined temperature range and holding it at that temperature for a first predetermined time period, and transferring the heated billet to a mold that has undergone a first preheating operation and performing one or more upsetting and drawing operations on the billet to obtain a pre-forged part; and a final forging step: performing a 1-heating, 2-step operation on the pre-forged part to obtain a final forged part, including heating the pre-forged part to a temperature within a second predetermined temperature range and holding it at that temperature for a second predetermined time period during the 1-heating operation, and transferring the heated pre-forged part to the mold that has undergone a second preheating operation and performing 2 steps, the 2 steps including a first step and a second step, wherein the first step causes the first upper punch of the mold to press down to complete the forging of the outer contour of the hollow shaft component, and the second step causes the second upper punch of the mold to press down to complete the forging of the inner contour of the hollow shaft component.

[0007] In one or more embodiments of the present invention, the above-described hollow shaft forging method further includes performing one or more re-forging processes before the pre-forging process, each re-forging process heating the billet to a temperature within a third predetermined temperature range and holding it at that temperature for a third predetermined time period and performing one or more upsetting and drawing operations on the billet.

[0008] In one or more embodiments of the present invention, the above-described hollow shaft forging method further includes performing a heat treatment process after the final forging process, wherein the heat treatment process performs homogenization heat treatment and / or annealing heat treatment on the final forging.

[0009] In one or more embodiments of the present invention, the above-described hollow shaft forging method further includes machining the shaft after one or more of the pre-forging process, the final forging process, and the heat treatment process.

[0010] In one or more embodiments of the present invention, the hollow shaft is trumpet-shaped.

[0011] In one or more embodiments of the present invention, the hollow shaft is made of a lightweight material.

[0012] In a preferred embodiment of the present invention, the lightweight material is a Ti-6Al-4V alloy.

[0013] In one or more embodiments of the present invention, the first predetermined temperature range is 940-990°C, the first predetermined time period is 270-390 minutes, and the first preheating operation heats the mold to a temperature greater than or equal to 250°C.

[0014] In one or more embodiments of the present invention, the second predetermined temperature range is 940-990°C, the second predetermined time period is 270-390 minutes, and the second preheating operation heats the mold to a temperature greater than or equal to 300°C.

[0015] In one or more embodiments of the present invention, the third predetermined temperature range is 940-990°C, and the third predetermined time period is 280-400 minutes for cold materials or 140-260 minutes for hot materials.

[0016] In one or more embodiments of the present invention, the homogenization heat treatment heats the final forging to 940-990°C and holds it at that temperature for 60-66 minutes, and then water-cools it; the annealing heat treatment heats the final forging to 650-750°C and holds it at that temperature for 120-132 minutes, and then air-cools it.

[0017] In one or more embodiments of the present invention, the first upper punch presses down at a speed of 5-15 mm / s, while the second upper punch presses down at a speed of 5-10 mm / s.

[0018] In another aspect of the present invention, a hollow shaft forged using the above-described method is provided.

[0019] These and other features and aspects of the invention will become clearer from the following detailed description with reference to the accompanying drawings. Attached Figure Description

[0020] To gain a detailed understanding of the invention, a more specific description of the invention briefly summarized above can be derived with reference to the embodiments. Some embodiments are shown in the accompanying drawings, and to facilitate understanding, the same reference numerals have been used as much as possible to indicate common elements in the figures. However, it should be noted that the drawings merely illustrate typical embodiments of the invention and should therefore not be considered as limiting the scope of the invention, as the invention allows for other equivalent embodiments, as shown in the drawings:

[0021] Figure 1 A flowchart of an example hollow shaft forging method according to an embodiment of the present invention is shown.

[0022] Figure 2 A cross-sectional view of an example pre-forged part according to an embodiment of the present invention is shown.

[0023] Figure 3 A partial cross-sectional view of an example final forging according to an embodiment of the present invention is shown.

[0024] Figure 4 The distribution of mechanical properties of a shaft manufactured using a hollow shaft forging method according to an embodiment of the present invention is shown.

[0025] Figure 5 A high-magnification micrograph of the microstructure of a shaft manufactured using a hollow shaft forging method according to an embodiment of the present invention is shown.

[0026] Figure 6 The mechanical properties and microstructure of the body of a shaft manufactured using a hollow shaft forging method according to an embodiment of the present invention are shown in photographs at different locations.

[0027] It is anticipated that elements in one embodiment of the invention may be advantageously adapted to other embodiments without further description. Detailed Implementation

[0028] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the invention; however, those skilled in the art should understand that the invention can be practiced without some or all of these specific details, and therefore the invention is not limited to the specific embodiments disclosed below. Furthermore, well-known processes or procedures have not been specifically described to avoid unnecessarily obscuring the invention.

[0029] Furthermore, it is understood that the various embodiments shown in the accompanying drawings are illustrative and the drawings are not necessarily drawn to scale.

[0030] This invention uses specific terms to describe embodiments of the invention. For example, "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic related to at least one embodiment of the invention. Therefore, it should be emphasized and noted that "an embodiment," "one embodiment," or "an alternative embodiment" mentioned twice or more in different places in this specification do not necessarily refer to the same embodiment. Furthermore, certain features, structures, or characteristics in one or more embodiments of the invention can be appropriately combined.

[0031] In this document, unless otherwise stated, the technical or scientific terms used in the claims and description should be understood in the ordinary sense by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" indicate that the elements or objects preceding "comprising" encompass the elements or objects listed following "comprising" or "including" and their equivalents, and do not exclude other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, nor are they limited to direct or indirect connections. Furthermore, the use of terms such as "about" or "approximately" herein indicates a range within ±10% of the nominal value.

[0032] Exemplary embodiments of the present invention will now be described in more detail with reference to the accompanying drawings.

[0033] One or more embodiments of the present invention relate to a method for forging hollow shafts. (See reference...) Figure 1 An exemplary hollow shaft forging method 100 may include a blanking process 110 for providing a billet. The hollow shaft forging method 100 may further include a pre-forging process 130 for heating the billet to a temperature within a first predetermined temperature range and holding it at that temperature for a first predetermined period of time, and transferring the heated billet to a die that has undergone a first preheating operation and performing one or more upsetting and drawing operations on the billet to obtain a pre-forged part. The hollow shaft forging method 100 may further include a final forging process 140 for performing a one-heat, two-step operation on the pre-forged part to obtain a final forged part. The final forging process 140 may include heating the pre-forging to a temperature within a second predetermined temperature range and holding it at that temperature for a second predetermined period during one forging cycle, and transferring the heated pre-forging to a die that has undergone a second preheating operation and performing two steps, the two steps including a first step and a second step, wherein the first step causes the first upper punch of the die to press down to complete the forging of the outer contour of the hollow shaft, and the second step causes the second upper punch of the die to press down to complete the forging of the inner contour of the hollow shaft.

[0034] The one-fire, two-step final forging process of this invention reduces the deformation instability zone and deformation dead zone, improving the deformation uniformity of all areas of the forging. Furthermore, compared to the existing one-fire, one-forging process, the one-fire, two-step process reduces dry firing. In addition, the one-fire, two-step process also reduces the amount of material used.

[0035] Taking the manufacturing of aero-engine fan shafts as an example, the larger open end of the fan shaft deforms more, while the smaller closed end deforms less. If the number of firing passes is too few, it will be difficult to guarantee the amount of deformation at the larger open end, or the deformation will be uneven. If the number of firing passes is too many, the smaller closed end is prone to forming a clear crystalline structure after dry firing. Using a one-fire, two-step operation allows the larger open end to obtain sufficient deformation, while the smaller closed end does not undergo multiple dry firings. That is, by ensuring that the smaller closed end is dry fired only once, sufficient and uniform deformation can be achieved at the larger open end. In addition, using a one-fire, two-step operation can save approximately 100 kg of material per fan shaft.

[0036] The hollow shaft of the present invention can be made of lightweight materials (e.g., those suitable for aircraft use). These lightweight materials may include titanium alloys, aluminum alloys, and / or carbon fiber composites, such as Ti-6Al-4V alloy.

[0037] In the hollow shaft forging method 100 of the present invention, the temperature value or temperature range to which the forging should be raised, and the required holding time, can be determined according to the size of the shaft to be forged. For example, the first predetermined temperature range during the pre-forging process 130 can be 940-990°C, the first predetermined holding time can be 270-390 minutes, and the first preheating operation can heat the die to a temperature greater than or equal to 250°C. Furthermore, the second predetermined temperature range during the final forging process 140 can be 940-990°C, the second predetermined holding time can be 270-390 minutes, and the second preheating operation can heat the die to a temperature greater than or equal to 300°C. In addition, the transfer time for transferring the billet and / or pre-forging to the die can be less than or equal to 60 seconds, for example, less than 45 seconds.

[0038] In a single-pass, two-step operation, the first upper punch of the die can be pressed down at a speed of 5-15 mm / s in the first step, while the second upper punch of the die can be pressed down at a speed of 5-10 mm / s in the second step. During this period, the lower die (also known as the base) can remain stationary.

[0039] Return to reference Figure 1 The hollow shaft forging method 100 may optionally include a reforging process (also known as a billet preparation process) 120. The reforging process 120 may be performed before the preforging process 130, and one or more such processes may be performed. Each reforging process 120 heats the billet to a temperature within a third predetermined temperature range and holds it at that temperature for a third predetermined time period, and performs one or more upsetting and drawing operations on the billet. In this document, the billet after reforging may be referred to as a rough billet. Similarly, the temperature value or temperature range to which the forging should be raised, and the required holding time, can be determined according to the size of the shaft to be forged. In the example, the third predetermined temperature range may be 940–990°C. Furthermore, in the example using cold material, the third predetermined holding time may be 280–400 minutes. In the example using hot material, the third predetermined holding time may be 140–260 minutes.

[0040] The re-forging process can provide pre-formed blanks, promote the uniformity of forging deformation, and enable the forgings to have better dimensional accuracy and surface flatness during the deformation process, so that the deformation is more in line with the predetermined model.

[0041] Furthermore, the hollow shaft forging method 100 may optionally include a heat treatment step 150. The heat treatment step 150 may be performed after the final forging step 140. The heat treatment step 150 may include homogenization heat treatment and / or annealing heat treatment. In one example, homogenization heat treatment may involve heating the final forging to 940–990°C and holding it at that temperature for 60–66 minutes, followed by water cooling. In one example, annealing heat treatment may involve heating the final forging to 650–750°C and holding it at that temperature for 120–132 minutes, followed by air cooling.

[0042] The heat treatment process can eliminate forging stress and improve the mechanical properties of the material as well as the uniformity of its property distribution.

[0043] Furthermore, the shaft can be machined after each step of the present invention (e.g., one or more of blanking step 110, pre-forging step 130, final forging step 140, and heat treatment step 150) to ensure that the shaft blank / forging meets the final part design and usage requirements. For example, after pre-forging step 130, positioning holes can be machined. In embodiments, machining can be roughing or finishing, and includes, but is not limited to, operations such as chamfering, milling, drilling, threading, boring, cutting, and grinding.

[0044] This invention can further ensure the deformation uniformity of the forging body through numerical simulation optimization. For large-size hollow shafts, a suitable preform can be one of the keys to ensuring successful shaft forging. The requirements for the volume distribution of shaft material during the forging process should aim at complete cavity filling, absence of flow defects, and uniform deformation in all parts. By determining the correspondence between the final forging cavity and the shape and size of the billet, the optimal combination of billet shape and size can be designed, further ensuring the deformation uniformity of the forging, as well as product performance and flaw detection level.

[0045] Exemplary embodiments

[0046] The following section uses the forging process of an aero-engine fan shaft as an example to illustrate in detail the performance of the shaft forged according to the method of the present invention.

[0047] (1) Blanking: Provide Ti-6Al-4V alloy bars with a diameter of 330mm as billets. The specific chemical composition includes: 6.58% Al, 4.4% V, 0.19% Fe, 0.022% C, 0.22% O, B<0.001%, Y<0.001%, H<0.002%, and Ti balance.

[0048] (2) Forging: Two forging passes are performed. In each forging pass, the billet bar is heated to 950±10℃ and held at that temperature, and then subjected to multiple upsetting and drawing operations. The diameter of the resulting cylindrical billet is 330±10mm.

[0049] (3) Pre-forging: The billet is heated to 950±10℃ and held for 270-390 minutes. Simultaneously, the die is heated to ≥250℃. Within a transfer time of ≤60 seconds, the heated billet is transferred to the heated die, and multiple upsetting and drawing operations are performed. The resulting pre-forged part has a large end diameter of 330±5mm and a small end diameter of 160±3mm, for example... Figure 2 As shown.

[0050] (4) Final forging: The pre-forging is heated to 950±10℃ and held for 270-390 minutes. Simultaneously, the die is heated to ≥300℃. Within a transfer time of ≤60 seconds, the heated pre-forging is transferred to the heated die, and the first and second steps are executed. The upper punch in the first step has a downward pressing speed of 10 mm / s, and the upper punch in the second step has a downward pressing speed of 7 mm / s. The resulting final forging is, for example... Figure 3 As shown (already machined).

[0051] (5) Heat treatment: including homogenization heat treatment and annealing heat treatment. In the homogenization heat treatment, the forging is heated to 960±10℃ and held for 60-66 minutes, and then water-cooled. In the annealing heat treatment, the forging is heated to 700±6℃ and held for 120-132 minutes, and then air-cooled.

[0052] The inventors conducted performance tests on the obtained fan shaft. From the fan shaft forging body, the inventors took 4 circumferential (also known as chordal) specimens, 3 radial specimens, and 6 axial specimens from different positions, for a total of 13 specimens. These specimens underwent mechanical property tests at room temperature and high temperature (300℃). The average values ​​and standard deviations are shown in Table 1 below.

[0053] Table 1: Mechanical Properties of Shaft Components

[0054] Test temperature Tensile strength MPa Yield MPa extend% Shrinkage % Measured mean ± standard deviation room temperature 1021±15 930±15 15±1 36±2 Reference value room temperature 900-1160 ≥830 ≥9 ≥25 Measured mean ± standard deviation 300℃ 704±18 578±13 17±2 51±2 Reference value 300℃ ≥650 ≥530 ≥9 ≥35

[0055] in addition, Figure 4 The small figure (a) shows the tensile strength (also known as tensile strength) and yield strength of the 13 specimens at room temperature. Figure 4 In small figure (b), the tensile strength and yield strength of the 13 specimens at 300°C are shown. Considering the sampling location, from... Figure 4 The distribution of mechanical properties within the shaft component can be observed. Figure 5 A high-magnification micrograph (×500) of the obtained shaft component is shown. Figure 6 The mechanical properties and microstructure of the obtained shaft body at different locations are shown in photographs (×100x).

[0056] From Table 1 and Figure 4 -6 It can be seen that the hollow shaft obtained by the forging method of the present invention can achieve the design requirements while having a low standard deviation and good stability in terms of bulk mechanical properties and microstructure.

[0057] The inventors also conducted flaw detection tests on the obtained shaft components. Specifically, water immersion flaw detection was performed on 10 inspection surfaces of the fan shaft forging using a large-size forging water immersion zone flaw detection method. The results showed that the noise level was at most Φ0.8-10dB, and no recording or display signals were found during the inspection process, therefore the inspection was qualified. This indicates that the obtained forging is defect-free within the inspection range and has a high degree of uniformity in its microstructure.

[0058] It should be noted that, in order to simplify the description of this application and thus aid in the understanding of one or more embodiments, the foregoing description of the embodiments of this application sometimes combines multiple features into a single embodiment, drawing, or description thereof. However, this disclosure method does not imply that the subject matter of this application requires more features than those mentioned in the claims. In fact, the features of an embodiment may be fewer than all the features of a single embodiment disclosed above.

[0059] In the detailed description of these embodiments, for the sake of brevity, this specification cannot provide a detailed description of all features of the actual embodiments. It should be understood that in the actual implementation of any embodiment, various specific decisions are often made to achieve the developer's specific goals and to meet system-related or business-related constraints, and these decisions may change from one embodiment to another. Furthermore, it is understood that although the efforts made in this development process may be complex and lengthy, for those skilled in the art related to the disclosure of this invention, some design, manufacturing, or production modifications based on the technical content disclosed in this invention are merely conventional technical means and should not be construed as insufficient content of this invention.

[0060] Although this application has been described with reference to specific embodiments, those skilled in the art should recognize that the above embodiments are merely illustrative and not restrictive. Various equivalent changes or substitutions can be made without departing from the spirit of this application. Therefore, any changes or modifications to the above embodiments within the essential spirit of this application will fall within the scope of the claims of this application.

Claims

1. A method for forging hollow shaft components, characterized in that, The process includes the following steps: Blanking process (110): Providing blanks; Pre-forging process (130): The billet is heated to a temperature within a first predetermined temperature range and held at that temperature for a first predetermined period of time. The heated billet is then transferred to a mold that has undergone a first preheating operation and one or more upsetting and drawing operations are performed on the billet to obtain a pre-forged part. as well as Final forging process (140): Performing a 1-heat, 2-step operation on the pre-forging part to obtain the final forging part, including heating the pre-forging part to a temperature within a second predetermined temperature range and holding it at that temperature for a second predetermined period during the 1-heat process, and transferring the heated pre-forging part to the die after a second preheating operation and performing 2 steps, the 2 steps including a first step and a second step, wherein the first step causes the first upper punch of the die to press down to complete the forging of the outer contour of the hollow shaft part, and the second step causes the second upper punch of the die to press down to complete the forging of the inner contour of the hollow shaft part. The hollow shaft is trumpet-shaped, and the 1-fire 2-step operation allows the large open end to obtain sufficient deformation, while the small closed end is not subjected to multiple dry firings.

2. The hollow shaft forging method according to claim 1, characterized in that, Further, it includes performing one or more reforging processes (120) before the preforging process (130), each reforging process (120) heating the billet to a temperature within a third predetermined temperature range and holding it at that temperature for a third predetermined period of time and performing one or more upsetting and drawing operations on the billet.

3. The hollow shaft forging method according to claim 1, characterized in that, The process further includes performing a heat treatment process (150) after the final forging process (140), wherein the heat treatment process (150) performs homogenization heat treatment and / or annealing heat treatment on the final forging.

4. The hollow shaft forging method according to claim 3, characterized in that, The process further includes machining the shaft after one or more of the pre-forging process (130), the final forging process (140), and the heat treatment process (150).

5. The hollow shaft forging method according to claim 1, characterized in that, The hollow shaft is made of lightweight material.

6. The hollow shaft forging method according to claim 5, characterized in that, The lightweight material is a Ti-6Al-4V alloy.

7. The hollow shaft forging method according to claim 1, characterized in that, The first predetermined temperature range is 940-990℃, the first predetermined time period is 270-390 minutes, and the first preheating operation heats the mold to a temperature greater than or equal to 250℃.

8. The hollow shaft forging method according to claim 1, characterized in that, The second predetermined temperature range is 940-990℃, the second predetermined time period is 270-390 minutes, and the second preheating operation heats the mold to a temperature greater than or equal to 300℃.

9. The hollow shaft forging method according to claim 2, characterized in that, The third predetermined temperature range is 940-990℃, and the third predetermined time period is 280-400 minutes for cold materials or 140-260 minutes for hot materials.

10. The hollow shaft forging method according to claim 3, characterized in that, The homogenization heat treatment heats the final forging to 940-990°C and holds it for 60-66 minutes, then water-cools it; the annealing heat treatment heats the final forging to 650-750°C and holds it for 120-132 minutes, then air-cools it.

11. The method for forging hollow shafts according to claim 1, characterized in that, The first upper punch presses down at a speed of 5-15 mm / s, while the second upper punch presses down at a speed of 5-10 mm / s.

12. A hollow shaft forged using any one of claims 1-11.

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