Rapid prototyping process for subsonic target projectile motor case

Abstract

The application discloses a kind of subsonic target projectile engine shell rapid forming process, and the shell is thin-walled rotary body cylinder structure.Process steps are as follows: split the shell into head, tail and middle section three independent components, respectively order blank and draw split processing diagram;Each component is respectively rough machining and reserved welding bevel;Head and middle section, tail and middle section are sequentially matched and welded, respectively after each welding, and stress relief treatment is carried out;Half-finishing is carried out to shell;Nondestructive testing is carried out to weld, and weld is executed according to GJB 1718A-2005 I level requirement;After detection is qualified, finishing and subsequent process are carried out.The application improves material utilization rate by segmented processing and combined welding, shortens manufacturing cycle, and effectively controls thin-walled deformation, and is suitable for the rapid manufacturing of target projectile engine shell.

Description

Technical Field

[0001] This invention relates to the field of aero-engine processing technology, specifically to a rapid prototyping process for the outer casing of a subsonic target missile engine. Background Technology

[0002] The subsonic target missile engine casing is the core load-bearing component of the target missile's propulsion system. Its structure is typically a thin-walled rotating cylindrical body, composed of three axially sections: a head (with internal grooves, ramps, and radius-of-freedom angles), a middle section (a straight cylinder with a uniform cross-section), and a tail section (with internal grooves, ramps, and radius-of-freedom angles). The total length can exceed 1800 mm, with a diameter of approximately 200 mm and a wall thickness of only about 1.6 mm. These parts have stringent requirements for dimensional accuracy, wall thickness uniformity, form and position tolerances, and mechanical properties; their machining quality directly affects the target missile's flight stability and service reliability.

[0003] Currently, the traditional manufacturing process for this type of engine casing mostly involves directly machining a single blank such as a forging or tube using subtractive processing methods like turning and boring. While this method ensures the integrity of the casing, it has revealed the following prominent problems in actual production: Firstly, the material utilization rate is low and the manufacturing cost is high. The overall processing requires the removal of a large amount of excess material from the large blank, especially for thin-walled long cylindrical structures, where the material removal rate often exceeds 60%, resulting in serious waste of raw materials. At the same time, the procurement cost of large-sized high-quality blanks and the subsequent large amount of cutting and machining costs keep the unit manufacturing cost high.

[0004] Secondly, the long processing cycle makes it difficult to meet the demand for rapid response. Due to the slender and thin-walled outer shell, the overall processing requires multiple clamping and layer-by-layer cutting, as well as multiple intermediate stress-relieving heat treatment processes. The processing time for a single piece can reach tens of hours, which cannot meet the urgent need for rapid delivery under the multi-variety, small-batch development mode of target projectile products.

[0005] Third, thin-walled deformation is difficult to control, resulting in a low yield. During the overall processing, as a large amount of material is removed, the residual stress inside the blank is gradually released, which can easily lead to warping, out-of-tolerance ellipticity, or instability in straightness of the cylinder. In particular, the head and tail sections with complex internal cavity structures have uneven stress distribution, and deformation problems are particularly prominent, making it difficult to guarantee the dimensional accuracy and geometric tolerances of the final product, and even causing batch scrap.

[0006] In recent years, additive manufacturing technologies such as selective laser sintering (SLS) and stereolithography (SLA) have shown some potential in the rapid prototyping of complex parts. However, their direct application to the mass production of large-size thin-walled cylinders is still limited by factors such as equipment forming area, forming efficiency and surface quality, and their economic efficiency and practicality are not yet mature.

[0007] Furthermore, in the field of welding repair, argon arc welding and laser cladding technologies have been widely applied to the repair of damage to components such as aero-engine bladed disks and casings. However, existing technologies mostly focus on welding local defects, and there is no mature solution that systematically integrates argon arc welding and laser cladding into the entire process of segmented manufacturing of engine casings. Especially for thin-walled structures with a wall thickness of only 1.6 mm, how to effectively control heat input, suppress welding deformation, and ensure that the mechanical properties of the circumferential weld consistently meet the stringent standards of GJB 1718A-2005 Class I welds during the combined welding process remains a technical challenge that urgently needs to be overcome.

[0008] In summary, the existing manufacturing process for the outer casing of subsonic target missile engines has significant shortcomings in terms of efficiency, cost, and deformation control. There is an urgent need to develop a new rapid prototyping process that can balance product quality and manufacturing efficiency. Summary of the Invention

[0009] To overcome the shortcomings of existing processes, this invention provides a rapid prototyping process for the outer casing of a subsonic target missile engine.

[0010] The technical solution adopted in this invention is as follows: a rapid prototyping process for a subsonic target missile engine casing, wherein the engine casing is a thin-walled rotating cylindrical structure, comprising the following steps: Step 1, Drawing breakdown and blank preparation: Based on the engine housing assembly drawings, the engine housing is broken down into three independent parts: head, tail and middle section. Each part is broken down and processed, and welding allowance and beveling form are marked. The raw material blanks required for each part are ordered according to the dimensions of the breakdown drawings. Step 2, Segmented rough machining: According to the disassembly and machining drawings of each component, rough machining is performed on the head, middle section and tail section respectively, and the machining is performed to the predetermined welding allowance size. Welding bevels are reserved after rough machining of each component. Step 3, assembly and welding: The rough-machined head and middle section, and the tail and middle section are assembled separately, and the three are welded together in sequence to form a complete shell cylinder; after each welding is completed, post-weld stress relief treatment is performed. Step 4, Semi-finishing: Perform semi-finishing on the welded shell cylinder to allow for subsequent finishing. Step 5, Weld Inspection: Perform non-destructive testing on the welded area, including dye penetrant testing and ultrasonic testing. The weld quality shall be in accordance with the requirements for Class I welds in GJB 1718A-2005. Step 6, Subsequent Processing: After the weld inspection is qualified, fine processing, surface treatment and final inspection are carried out according to the original manufacturing process until the finished product is delivered.

[0011] Preferably, the welding process in step 3 adopts a combination of argon arc welding and laser cladding technology, specifically: the welding groove is cleaned before welding, argon arc welding is used for the root pass to ensure root penetration, and then laser cladding technology is used for the fill and cover welding.

[0012] Preferably, the laser cladding process parameters are: laser power 1.5-3.5kW, scanning speed 5-15mm / s, powder feeding rate 8-20g / min, and overlap rate 30%-50%.

[0013] Preferably, the post-weld stress relief treatment in step 3 adopts a vibration aging treatment method.

[0014] Preferably, the semi-finishing allowance in step 4 is 0.3 to 0.8 mm.

[0015] Preferably, the circumferential weld butt joint bevel used in step 3 is a V-shaped bevel or a U-shaped bevel.

[0016] Preferably, after the semi-finishing process described in step 4 is completed and before the finishing process in step 6, a stabilizing heat treatment process is also provided to release the processing stress.

[0017] Preferably, the material of the engine housing is 30CrMnSiA.

[0018] Preferably, the wall thickness of the engine housing is 1.6 mm.

[0019] Preferably, in step 1, forging blanks are used for the head and tail sections, and pipe blanks are used for the middle section.

[0020] The present invention has the following beneficial effects: 1. Improve material utilization: By splitting the overall shell into three independent parts—head, tail, and middle section—and ordering blanks for each part according to their actual dimensions, the waste of cutting off a large amount of excess material from the large blank during the overall processing is avoided, thus reducing raw material costs.

[0021] 2. Shorten manufacturing cycle: By adopting a segmented parallel processing method, the head, tail and middle sections can be roughed at the same time and then assembled by welding, which reduces the processing time of a single piece and can respond more quickly to the research and production needs of multiple varieties and small batches of target missile products.

[0022] 3. Effective control of thin-wall deformation: During segmented machining, the structure of each component is relatively simple and has good rigidity, making it easy to control machining stress; after rough machining and stress relief treatment, deformation at each stage can be effectively controlled. Compared with integral machining, this process is more conducive to ensuring the roundness, straightness, and other geometric tolerances of the final thin-walled shell.

[0023] 4. Ensuring weld quality: A welding method combining argon arc welding for the root pass and laser fusion for the cover pass is employed. Argon arc welding ensures root penetration, while laser fusion allows for precise control of welding heat input, resulting in a small heat-affected zone and low thermal distortion. Non-destructive testing confirms that the weld meets the mechanical and performance requirements of GJB1718A-2005 Class I welds.

[0024] 5. Good process applicability: This process route is not only suitable for the rapid manufacturing of subsonic target missile engine shells, but can also be extended to the segmented forming of other similar thin-walled rotating shell parts, and has good versatility and reference value. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the disassembled structure of the subsonic target missile engine casing in an embodiment of the present invention.

[0026] Figure 2 This is an enlarged schematic diagram of point A in an embodiment of the present invention.

[0027] Figure 3 This is a process flow diagram of an embodiment of the present invention.

[0028] Figure 4 This is a schematic diagram of the overall structure of the subsonic target missile engine casing in an embodiment of the present invention.

[0029] In the diagram: 1-Head; 2-Middle section; 3-Tail; 4-Weld location. Detailed Implementation

[0030] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0031] This embodiment uses the outer casing of a certain type of subsonic target missile engine as an example. The casing is a thin-walled rotating cylindrical structure with a total length of approximately 1830 mm, a diameter of approximately 200 mm, a wall thickness of 1.6 mm, and is made of 30CrMnSiA material. Its overall molding process is as follows... Figure 3 As shown.

[0032] I. Drawing Breakdown and Blank Preparation like Figure 1 and Figure 2 As shown, based on the engine housing assembly drawings, the engine housing is disassembled into three independent components: head section 1, tail section 3, and intermediate section 2. Separate machining drawings are created for each component, indicating the welding allowances and beveling methods. Simultaneously, based on the dimensions of the disassembled drawings, the necessary raw material blanks for head section 1, tail section 3, and intermediate section 2 are ordered. Forged blanks are used for head section 1 and tail section 3 due to their complex structures, including internal grooves, ramps, and radius angles; tubular blanks are used for intermediate section 2, which has a uniform cross-section straight cylinder structure.

[0033] By disassembling the overall shell into three independent components and ordering blanks for each, the waste of cutting off large amounts of excess material from the large blank during overall processing is avoided, effectively improving material utilization and reducing raw material costs. In this embodiment, compared to the overall processing solution, material utilization is increased by approximately 25%. After each blank arrives, it needs to undergo incoming inspection, including chemical composition retesting, mechanical property sampling, and surface quality inspection, to confirm that the material grade, specifications, and surface quality meet the drawings and process requirements.

[0034] II. Segmented rough machining and pre-heat treatment Based on the component breakdown drawings, the head section 1, middle section 2, and tail section 3 are rough-machined separately. During rough machining, each component is machined to the predetermined welding allowance dimensions, and welding bevels are pre-drilled at the welding ends of each component. V-shaped or U-shaped bevels are used. During rough machining, the dimensional consistency of the inner holes and outer circles of each component must be controlled to ensure the docking accuracy during subsequent assembly.

[0035] After rough machining, each component undergoes preliminary heat treatment to eliminate internal stresses generated during forging and rough machining, improve the material's machinability, and provide a stable microstructure for subsequent semi-finish machining processes. The heat treatment regime is performed according to the 30CrMnSiA material standard. After heat treatment, the hardness of each component is tested to confirm that the heat treatment effect meets the process requirements.

[0036] After preliminary heat treatment, the head 1, middle section 2, and tail 3 are semi-finished. Semi-finishing further approximates the final dimensions and ensures the coaxiality and perpendicularity of the welded ends of each component. During segmented machining, the relatively simple structure and good rigidity of each component make it easier to control machining stress, which helps reduce deformation during thin-walled machining. Simultaneously, roughing and semi-finishing operations can be performed concurrently on the head 1, middle section 2, and tail 3, shortening the machining time per piece. After semi-finishing, the dimensions of each component are inspected to confirm that the machining dimensions meet the requirements of the sectional machining drawing.

[0037] III. Assembly and Welding Forming like Figure 3 As shown, the semi-finished head 1 is assembled with the middle section 2, and the tail 3 is assembled with the middle section 2. During assembly, the coaxiality and uniformity of the gap between the mating surfaces must be ensured, and fixtures are used to fix them to ensure assembly accuracy. After assembly, the head 1 and the middle section 2 are connected by welding for the first time. Before welding, the weld bevel is cleaned to remove oil, scale, and other impurities.

[0038] The welding process employs a combination of argon arc welding and laser cladding. First, argon arc welding is used for the root pass to ensure complete penetration; then, laser cladding is used for the fill and cover passes. The laser cladding process parameters are: laser power 1.5–3.5 kW, scanning speed 5–15 mm / s, powder feed rate 8–20 g / min, and overlap rate 30%–50%. In this embodiment, the laser cladding process parameters are: laser power 2.5 kW, scanning speed 10 mm / s, powder feed rate 12 g / min, and overlap rate 40%.

[0039] Argon arc welding for the root pass ensures weld penetration, while laser cladding for the filler and cover passes enables precise control of welding heat input, resulting in a small heat-affected zone and low thermal distortion. For thin-walled structures with a wall thickness of 1.6 mm, this combination effectively controls welding heat input and suppresses welding deformation.

[0040] After the first welding is completed, post-weld stress relief treatment is performed using a vibration aging device. Vibration aging treatment uses resonance to superimpose residual stress and alternating stress within the workpiece, causing plastic deformation after reaching the material's yield limit, thereby reducing and homogenizing welding residual stress. Compared to traditional thermal aging, vibration aging treatment is low-cost, highly efficient, and environmentally friendly. In this embodiment, the vibration aging treatment time is approximately 30 minutes.

[0041] After stress relief treatment, the welded assembly undergoes semi-finish machining to correct any minor deformations that may occur during welding and stress relief, ensuring assembly accuracy when subsequently docking with the tail section 3. After semi-finish machining, the tail section 3 is assembled with the intermediate section 2 using the same welding process for a second welding connection, forming a complete shell. After the second welding, a vibration aging device is used again for post-weld stress relief treatment to eliminate residual welding stress generated by the second circumferential weld.

[0042] IV. Weld Inspection After both welding operations and stress relief treatments are completed, non-destructive testing (NDT) is performed on the two circumferential welds at position 4. NDT includes two methods: dye penetrant testing and ultrasonic testing. DDT is used to check for surface defects such as cracks and porosity; ultrasonic testing is used to check for internal defects such as incomplete fusion and slag inclusions. The weld quality meets the requirements for Class I welds in GJB 1718A-2005. Only after passing the inspection can the next process begin.

[0043] Setting weld inspection after post-weld stress relief treatment and before finishing allows for timely detection of weld defects and subsequent repair welding, avoiding waste of time and materials in later finishing processes. In this embodiment, the inspection results of both circumferential welds meet the requirements of Class I welds in GJB 1718A-2005.

[0044] V. Finishing and Welding of Accessories After the weld inspection is qualified, finish turning is performed on the shell cylinder. During finish turning, the final dimensional accuracy must be strictly controlled to ensure that the form and position tolerances such as roundness and straightness of the shell cylinder meet the design requirements.

[0045] After the finish turning is completed, finish milling is performed on the shell cylinder to machine the structural features such as the end faces of the head 1 and the tail 3, as well as various grooves and hole systems, so as to ensure that the dimensional and positional accuracy of each part meets the requirements of the final assembly drawing.

[0046] After the finish milling is completed, the third welding is performed on various accessories (such as brackets, supports, nozzles, etc.) on the shell cylinder. All accessory welding is carried out by argon tungsten-arc welding. After welding, local dye penetrant inspection is performed on the accessory welds to confirm that there are no defects on the weld surfaces.

[0047] After the accessory welding is completed, the benchwork procedure is carried out to remove burrs and sharp edges at various parts, and trim the weld reinforcement to make the surface of the shell cylinder transition smoothly. After the benchwork is completed, a hydraulic test is carried out according to the technical requirements to verify the sealing performance and pressure bearing capacity of the shell cylinder. The hydraulic test pressure and pressure holding time are implemented according to the requirements of the design drawing. The test is qualified if there is no leakage and no visible deformation on the shell surface during the test.

[0048] After the hydraulic test is qualified, surface treatment is performed on the shell cylinder, including sandblasting cleaning, coating protective layers, etc., to meet the anti-corrosion requirements of the use environment. After the surface treatment is completed, marking is performed at the specified position according to the drawing requirements to identify information such as product number and specification.

[0049] VI. Finished Product Inspection and Warehousing After the marking is completed, a comprehensive inspection of the finished product is carried out, including appearance inspection, dimension re-inspection, form and position tolerance detection and surface quality inspection. After all inspection indicators are qualified, the product is cleaned, packaged and the warehousing procedures are completed.

[0050] Verified by trial production, the engine shell processed by this process is as Figure 4 shown, the weld quality meets the requirements of Class I welds specified in GJB 1718A-2005, the roundness of the shell is not more than 0.8mm, the straightness is not more than 0.5mm, and the mechanical performance indicators such as tensile strength and elongation all meet the design requirements. The manufacturing cycle is shortened by about 40% compared with the integral machining scheme, and the material utilization rate is increased by about 25%. This process route is not only applicable to the rapid manufacturing of subsonic target missile engine shells, but also can be popularized and applied to the segmented forming of other similar thin-walled revolving body shell parts.

[0051] Obviously, the above-described embodiments of the present invention are merely examples for illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other obvious changes or modifications derived from the essential spirit of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A rapid prototyping process for a subsonic target missile engine casing, wherein the engine casing is a thin-walled rotating cylindrical structure, characterized in that... Includes the following steps: Step 1, Drawing breakdown and blank preparation: Based on the engine housing assembly drawings, the engine housing is broken down into three independent parts: head, tail and middle section. Each part is broken down and processed, and welding allowance and beveling form are marked. The raw material blanks required for each part are ordered according to the dimensions of the breakdown drawings. Step 2, Segmented rough machining: According to the disassembly and machining drawings of each component, rough machining is performed on the head, middle section and tail section respectively, and the machining is performed to the predetermined welding allowance size. Welding bevels are reserved after rough machining of each component. Step 3, assembly and welding: The rough-machined head and middle section, and the tail and middle section are assembled separately, and the three are welded together in sequence to form a complete shell cylinder; after each welding is completed, post-weld stress relief treatment is performed. Step 4, Semi-finishing: Perform semi-finishing on the welded shell cylinder to allow for subsequent finishing. Step 5, Weld Inspection: Perform non-destructive testing on the welded area, including dye penetrant testing and ultrasonic testing. The weld quality shall be in accordance with the requirements for Class I welds in GJB 1718A-2005. Step 6, Subsequent Processing: After the weld inspection is qualified, fine processing, surface treatment and final inspection are carried out according to the original manufacturing process until the finished product is delivered.

2. The rapid prototyping process for the subsonic target missile engine casing according to claim 1, characterized in that, The welding process described in step 3 uses a combination of argon arc welding and laser cladding technology. Specifically, the welding groove is cleaned before welding, argon arc welding is used for the root pass to ensure root penetration, and then laser cladding technology is used for the fill and cover welding.

3. The rapid prototyping process for the subsonic target missile engine casing according to claim 2, characterized in that, The laser cladding process parameters are: laser power 1.5-3.5kW, scanning speed 5-15mm / s, powder feeding rate 8-20g / min, and overlap rate 30%-50%.

4. The rapid prototyping process for the subsonic target missile engine casing according to claim 1, characterized in that, The post-weld stress relief treatment described in step 3 adopts a vibration aging treatment method.

5. The rapid prototyping process for the subsonic target missile engine casing according to claim 1, characterized in that, The semi-finishing allowance in step 4 is 0.3 to 0.8 mm.

6. The rapid prototyping process for the subsonic target missile engine casing according to claim 1, characterized in that, The circumferential weld butt joint bevel used in step 3 is either a V-shaped bevel or a U-shaped bevel.

7. The rapid prototyping process for the subsonic target missile engine casing according to claim 1, characterized in that, After the semi-finishing process described in step 4 is completed and before the finishing process in step 6, a stabilizing heat treatment process is set up to release the processing stress.

8. The rapid prototyping process for the subsonic target missile engine casing according to claim 1, characterized in that, The engine casing is made of 30CrMnSiA material.

9. The rapid prototyping process for the subsonic target missile engine casing according to claim 1, characterized in that, The wall thickness of the engine casing is 1.6 mm.

10. The rapid prototyping process for the subsonic target missile engine casing according to claim 1, characterized in that, In step 1, forging blanks are used for the head and tail sections, and pipe blanks are used for the middle section.

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