Integral wind tunnel nozzle hot spinning forming method

Abstract

The invention discloses an integral wind tunnel nozzle hot spinning forming method which comprises the following steps: determining the structural size of a blank, and primarily processing to obtain a tubular spinning blank; designing a clamp and a spinning roller; a spinning pass and a spinning track are designed, specifically, a multi-pass spinning technology is utilized, and the spinning pass is designed according to the limit thinning rate and the material thinning rate; a spinning track is determined according to the spinning pass and the shape of a spinning finished product; spinning parameters are designed; the blank is subjected to multi-pass hot spinning machining through a centerless die; and stress relief annealing is conducted on the blank subjected to hot spinning machining, and a finished product is obtained. The temperature is controlled through heating in the spinning process, so that oxidation and grain coarsening are avoided, the ductility of the material is improved, and the precision is improved through multi-pass incremental forming.

Description

Technical Field

[0001] The present invention belongs to the technical field of wind tunnel nozzle forming, and particularly relates to a hot spinning forming method for an integral wind tunnel nozzle. Background Technique

[0002] Wind tunnel experiments play a crucial role in fields such as aerospace and automotive engineering, providing key means for research and design. One of the core components of a wind tunnel, the nozzle, directly affects the airflow characteristics, including the internal flow path shape and surface quality. Therefore, by deeply studying nozzle forming technology, an accurate internal structure can be manufactured, significantly improving the accuracy and reliability of experimental data.

[0003] The internal airflow uniformity and stability of the nozzle have an important impact on the experimental results. Through research on nozzle forming technology, a more reasonable internal flow path structure can be designed and manufactured, thereby improving the airflow distribution, reducing turbulence and disturbances, and further enhancing the quality of the wind tunnel experimental environment.

[0004] Traditional methods for manufacturing wind tunnel nozzles may be cumbersome, time-consuming, and costly. Currently, the forming methods for wind tunnel nozzles at home and abroad include numerical control machine tool processing, electrical discharge machining, laser cutting and welding, and additive manufacturing (3D printing), etc. However, each forming method has some limitations, such as problems like tool marks, assembly steps, poor internal finish, and poor barrel rigidity.

[0005] Spinning forming technology can reduce manufacturing costs and cycle times. However, since wind tunnel nozzles often use high-strength alloys or high-temperature resistant materials and have thick tube walls, their poor plasticity easily leads to cracking or difficult-to-precisely-control springback during the spinning process, resulting in non-uniform curvature and wall thickness. In particular, local thinning or wrinkling is likely to occur at the junction of the throat and the expansion section. Therefore, processing wind tunnel nozzles through spinning forming technology is a technical challenge. Summary of the Invention

[0006] In order to solve the problems of material waste and the integration of complex profiles in the overall forming of existing wind tunnel nozzles, the present invention provides a hot spinning forming method for an integral wind tunnel nozzle. By controlling the temperature during the spinning process to avoid oxidation and grain coarsening, improving the material ductility, and adopting multi-pass progressive forming to improve the accuracy, the present invention has the advantages of low cost-effectiveness, high material utilization rate, short manufacturing cycle, high processing accuracy, good surface quality, and no need for welding, providing reliable technical support for the manufacture of high-performance wind tunnel nozzles.

[0007] The object of the present invention is achieved through the following technical solutions:

[0008] A hot spinning forming method for an integral wind tunnel nozzle, comprising the following steps:

[0009] S1. Determine the structural dimensions of the blank and perform preliminary machining to obtain a tube-shaped spinning blank;

[0010] S2. Design the fixture and spinning wheels;

[0011] S3. Design the spinning passes and spinning trajectories:

[0012] S31. Utilize the multi-pass spinning technology to design the spinning passes according to the ultimate thinning rate and the material thinning rate;

[0013] S32. Determine the spinning trajectories according to the spinning passes and the shape of the spun finished part;

[0014] S4. Design the spinning parameters;

[0015] S5. Perform non-centering die multi-pass hot spinning on the blank;

[0016] S6. Perform stress relief annealing on the blank after hot spinning to obtain the finished part.

[0017] Furthermore, the step S1 includes:

[0018] S11. Preset the blank as a tube-shaped blank according to the generatrix shape of the finished part, and determine the dimensions of the tube-shaped blank according to the structural dimensions of the spun finished part. The dimensions of the tube-shaped blank are calculated by the following formula:

[0019]

[0020]

[0021]

[0022] In the formula, is the blank diameter; is the maximum diameter of the spun finished part; is the blank thickness; is the blank length; is the maximum thickness of the spun finished part; is the length of the spun finished part;

[0023] S12. Obtain a tube-shaped spinning blank with an outer diameter of a thickness of and a length of through forging and heat treatment.

[0024] Furthermore, in the step S2, for the spinning part with only one end closed, the jaws adopt a circumferential split fixture, and the inner surface of the jaws is machined with grid-like textures.

[0025] Furthermore, the step S31 includes:

[0026] According to the wall thickness of the blank and the wall thickness t of the spun finished part, the ultimate thinning rate is calculated by the following formula :

[0027]

[0028] Determine the single-pass thinning rate according to the material properties, process parameters, and equipment capabilities , ; Through the pass thinning rate , calculate the required number of spinning passes N:

[0029]

[0030] Furthermore, determine the roller feed ratio in the step S4.

[0031] Furthermore, in the step S5, measure the temperature of the blank by a temperature measuring device, and through a heating device, make the blank reach the preset forming temperature T before the roller contacts the material; after starting spinning, control the temperature measuring device and the heating device to move axially together with the roller to keep the blank section in front of the roller in a preheating and heating process; during the spinning process, the temperature measuring device measures the temperature of the blank in real time, and the heating device adjusts the heating power according to the preset temperature and the measured temperature.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The present invention provides a method for hot spinning forming of an integral wind tunnel nozzle, which realizes the efficient and economical processing of the nozzle, has a high material utilization rate, almost no chips are generated, reduces the raw material cost; during the processing, the material undergoes plastic deformation, improves the strength and stiffness of the nozzle, and enhances its stability and fatigue resistance under high-speed air flow; the surface finish of the spun nozzle is good, reduces the subsequent processing procedures, and shortens the production cycle; at the same time, the present invention has low requirements for the operating environment, does not use cutting fluid, conforms to the concept of green manufacturing, and is an environmentally friendly processing method. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings used in the description of the embodiments of the present invention. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the content of the embodiments of the present invention and these drawings.

[0035] Figure 1 It is a schematic diagram of the blank in the embodiment of the present invention;

[0036] Figure 2This is the front view of the fixture in the embodiment of the present invention;

[0037] Figure 3 This is the schematic diagram of the jaw in the embodiment of the present invention;

[0038] Figure 4 This is the schematic diagram of the spinning wheel in the embodiment of the present invention;

[0039] Figure 5 This is the spinning trajectory diagram in the embodiment of the present invention;

[0040] Figure 6 This is the schematic diagram of the spinning operation in the embodiment of the present invention;

[0041] Figure 7 This is the schematic diagram of the finished product after spinning in the embodiment of the present invention;

[0042] Figure 8 This is the overall flowchart of the spinning forming method for an integral wind tunnel nozzle according to the embodiment of the present invention;

[0043] In the figure:

[0044] 1 - chuck; 2 - jaw; 3 - spinning wheel; 4 - blank; 5 - heating device. Specific implementation mode

[0045] The present invention will be described in detail below with reference to the accompanying drawings and specific implementation modes. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention.

[0046] The traditional nozzle manufacturing process requires multi-stage processing and assembly together to obtain a nozzle group. A large amount of cutting processing of materials will cause a large amount of material waste and poor airtightness, affecting the experimental results.

[0047] This embodiment is a hot spinning forming method for an integral wind tunnel nozzle, including the following steps:

[0048] S1. Determine the structural dimensions of the blank and perform preliminary processing to obtain a tubular spinning blank:

[0049] S11. Determine the dimensions of the blank according to the dimensional structure and machining allowance of the finished product:

[0050] Preset the blank as a tubular blank according to the bus shape of the finished product, and determine the dimensions of the tubular blank according to the structural dimensions of the finished product after spinning. The dimensions of the tubular blank are calculated by the following formula:

[0051]

[0052]

[0053]

[0054] In the formula, is the blank diameter; is the maximum diameter of the spun finished part; is the blank thickness; is the blank length; is the maximum thickness of the spun finished part; is the length of the spun finished part;

[0055] S12. Rough machining to obtain a tubular spinning blank:

[0056] Through forging and heat treatment, a tubular spinning blank with an outer diameter of , a thickness of , and a length of is obtained, as shown in Figure 1 .

[0057] S2. Design the fixture and spinning wheel:

[0058] S21. Determine the fixture structure according to the outer dimensions of the tubular spinning blank:

[0059] For a spinning part with only one end closed, the jaw 2 is clamped in the straight section area where spinning is not performed. The length of the jaw 2 is generally less than the length of the straight section at the clamping position. The jaw 2 mostly uses a circumferential split fixture. In this embodiment, the jaw 2 is divided into 5 petals circumferentially, as shown in Figure 2 ; To prevent the blank 4 from moving during spinning, the inner surface of the jaw 2 is machined into a grid-like texture to increase the friction between the jaw 2 and the blank 4 during spinning and prevent the blank 4 from moving. At the same time, the jaw should be made of a high-temperature resistant material to prevent deformation due to heating. The jaw is shown in Figure 3 .

[0060] S22. The spinning wheel 3 should have sufficient stiffness, hardness, heat resistance, and good surface quality. In this embodiment, the spinning wheel 3 is made of high-quality high-speed steel. For necking spinning, to prevent interference between the spinning wheel 3 and the blank 4, the diameter of the spinning wheel 3 is 500 mm, and the shape of the spinning wheel 3 is set as shown in Figure 4 , and the fillet radius of the spinning wheel 3 is set to 20 mm.

[0061] S3. Design of spinning passes and spinning trajectories:

[0062] S31. Using multi-pass spinning technology, design the spinning passes according to the limit thinning rate and material thinning rate:

[0063] According to the wall thickness of the blank and the wall thickness t of the spun finished part, the limit thinning rate is calculated through the following formula:

[0064]

[0065] Determine the single-pass thinning rate according to the material properties, process parameters, and equipment capabilities , , and through the pass thinning rate , calculate the required spinning passes N through the following formula:

[0066]

[0067] S32. Determine the spinning trajectory according to the spinning passes and the shape of the spun finished part. As Figure 5 shown, it is used during spinning, combining forward spinning and reverse spinning. The dotted part is the spinning trajectory. Allocate forward spinning or reverse spinning for each pass according to the thickness of the mouth part. Reverse spinning can thicken the mouth part of the blank.

[0068] S4. Spinning parameter design:

[0069] During the spinning operation, the size of the spinning wheel feed ratio has an obvious influence on the spinning deformation, and its influence varies with the type of material and should be determined according to the specific situation. The feed ratio for tube-shaped part spinning can be selected within the range of 0.3 mm / r to 2.5 mm / r. When not considering the surface roughness of the workpiece and only requiring a large reduction in diameter, a higher feed ratio can be used, which can be selected within 0.5 mm / r to 3 mm / r.

[0070] S5. Carry out multi-pass hot spinning processing of the blank without a mandrel:

[0071] Install the blank and the required devices on the machine tool, as Figure 6 shown;

[0072] According to the spinning passes, spinning trajectory, and spinning wheel feed ratio designed in the previous steps, set the spinning program and start the machine tool;

[0073] Measure the temperature of the blank through the temperature measuring device, and through the heating device, make the blank reach the predetermined forming temperature T (the temperature of the plastic zone of the processed material) before the spinning wheel contacts the material, improving the ductility of the material. The range of the predetermined forming temperature T is in the interval of 700°C to 800°C; when the temperature reaches, start spinning, control the temperature measuring device and the heating device to move axially together with the spinning wheel to keep the material in front of the spinning wheel in a preheating and heating process, enabling the deformation process to proceed smoothly; during the spinning process, the temperature measuring device measures the temperature of the blank in real time, and the heating device adjusts the heating power according to the preset temperature and the measured temperature to ensure that the forming temperature range meets the requirements.

[0074] S6. Stress relief heat treatment: Carry out stress relief annealing on the blank processed by hot spinning to balance the material properties and dimensional stability, and finally obtain a finished part of a special-shaped part with a large length-diameter ratio and a complex curved generatrix.

[0075] During the spinning operation, continuously heating and rolling the blank will generate internal stress within the material. To prevent the spun parts from deforming due to internal stress in the later stage, stress relief heat treatment is required. The stress relief heat treatment process needs to be formulated according to the material type and the performance requirements of the final product to eliminate internal stress, ensure the dimensional stability of the product, and make the service performance meet the design requirements. In this embodiment, the heat treatment temperature of the blank is 500°C to 550°C, the holding time is 3.5 h, and it is cooled in the furnace to below 400°C and then air-cooled. Finally, a finished product of the large wind tunnel nozzle is obtained as Figure 7 shown.

[0076] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for hot spinning of an integral wind tunnel nozzle, characterized in that: The following steps are involved: S1, determine the blank structure size, and perform preliminary processing to obtain a tubular spinning blank; S2, design the fixture and the rotary wheel; S3. Design of spinning passes and spinning trajectory: S31. Using multi-pass spinning technology, design the spinning passes according to the limit thinning rate and material thinning rate; S32. Determine the spinning trajectory according to the spinning passes and the shape of the finished spinning part; S4, spinning parameter design; S5, performing a centerless hot spinning process on the blank in multiple passes; S6. Perform stress relief annealing on the blank after hot spinning to obtain a finished product.

2. A method for hot spinning of an integral wind tunnel nozzle as claimed in claim 1, characterized in that: The step S1 comprises: S11. The blank is preset as a tubular blank according to the generatrix shape of the finished part, and the size of the tubular blank is determined according to the structural dimensions of the finished part after spinning. The size of the tubular blank is calculated by the following formula: ； ； ； In the formula, is the billet diameter; Maximum diameter of the finished spinning part; is the blank thickness; is the billet length; The maximum thickness of the finished spinning part; is the length of the finished spinning part; S12. After forging and heat treatment, the outer diameter is , thickness is , length is Tubular spinning blank.

3. The method for hot spinning of an integral wind tunnel nozzle according to claim 1, characterized in that: In step S2, for the spun part with only one end closed, the clamp adopts a circumferentially split clamp, and the inner surface of the clamp is processed with a grid-like texture.

4. The method for hot spinning of an integral wind tunnel nozzle according to claim 1, characterized in that: The step S31 comprises: According to the wall thickness of the blank The limit thinning rate is calculated by the following formula: : ； Determine the single pass thinning rate based on material properties, process parameters, and equipment capabilities , ;Thinning rate through the pass , calculate the required spinning passes N: 。 5. The method for hot spinning of an integral wind tunnel nozzle according to claim 1, characterized in that: In step S4, the rotary wheel feed ratio is determined.

6. The method for hot spinning forming of an integral wind tunnel nozzle according to claim 1, characterized in that: In step S5, the temperature of the blank is measured by a temperature measuring device, and the blank is made to reach a preset forming temperature T before the rotating wheel contacts the material by a heating device; after the spinning starts, the temperature measuring device and the heating device are controlled to move axially together with the rotating wheel to keep the blank section in front of the rotating wheel in the preheating and heating process; during the spinning process, the temperature measuring device measures the blank temperature in real time, and the heating device adjusts the heating power according to the preset temperature and the measured temperature.

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