A method for manufacturing a casing

Abstract

This invention relates to the field of aero-engine manufacturing technology, specifically to a method for manufacturing a casing. The method includes the following steps: machining a ring forging into a near-net-shape casing cylindrical part with welding bosses using a spin forming process; machining a boss part that matches the welding bosses; preheating the boss part located on the vibration side using a heating coil before welding, while simultaneously performing linear friction welding on the casing cylindrical part and the boss part; continuing heating with the heating coil after welding and holding the pressure for a preset time; performing post-weld heat treatment on the entire part after welding; and performing CNC machining after heat treatment to obtain the finished casing. The purpose of this casing manufacturing method is to solve the problems of large heat input, large deformation of thin-walled cylindrical parts, easy generation of welding defects, and difficulty in controlling weld quality in traditional casing manufacturing processes.

Description

Technical Field

[0001] This invention relates to the field of aero-engine manufacturing technology, and more specifically to a method for manufacturing a casing. Background Technology

[0002] The casing is one of the key structural components of an aero engine. Its structure and dimensions are complex, and a typical casing structure is as follows: Figure 1 As shown, a number of cylindrical bosses, rhomboid bosses, square bosses, etc. are distributed on the large-diameter thin-walled cylinder.

[0003] The casing is difficult to manufacture. Traditional casing manufacturing methods typically involve using an integral ring forging followed by machining. The various boss structures on the outside of the casing are mainly functional structures, and their dimensions are larger than the casing itself. The integral forging, including all the bosses, is quite large, resulting in extremely low material utilization and a long subsequent machining time.

[0004] Various boss structures on the outer side of the cylinder are also connected by mechanical means or by fusion welding. Mechanical connection will lead to problems such as complex structure, increased weight and low reliability; fusion welding of boss structures can only be achieved at the outer ring of the mating surface, and it is impossible to achieve 100% fusion of the mating surface. Fusion welding has a large heat input, thin-walled cylinder is prone to deformation, and defects such as porosity, slag inclusion and cracks are prone to occur at the weld, resulting in low bonding strength and even scrapping of the casing. It is risky and costly.

[0005] Therefore, the inventors provided a method for manufacturing the casing. Summary of the Invention

[0006] (1) Technical problems to be solved

[0007] This invention provides a method for manufacturing a casing, which solves the technical problems of large heat input, large deformation of thin-walled cylinder, easy generation of welding defects, and difficulty in controlling weld quality in traditional casing manufacturing processes.

[0008] (2) Technical solution

[0009] This invention provides a method for manufacturing a casing, comprising the following steps:

[0010] The ring forging is processed into a near-net-shape casing body part with welding bosses using a spin forming process;

[0011] Machining a boss part that matches the welding boss;

[0012] The boss part located on the vibration side is preheated by heating coil before welding. At the same time, the casing part and the boss part are linearly friction welded. After welding, the heating coil continues to heat and holds pressure for a preset time.

[0013] After welding, the entire part undergoes post-weld heat treatment.

[0014] After heat treatment, CNC machining is performed to obtain the finished casing.

[0015] Furthermore, the process of machining the ring forging into a near-net-shape casing body part with welding bosses using a spin forming process specifically includes the following steps:

[0016] A force is applied to the outer side of the ring forging by a spinning wheel, causing the middle region of the ring forging to be thinned.

[0017] The thinned ring forging is fixed on the mandrel using a segmented die, and a spinning wheel spins the ring forging inside the ring forging, so that the ring forging fills the groove of the segmented die under the action of extrusion pressure, forming a welding base.

[0018] Furthermore, the height of the welding boss is 1-2 mm.

[0019] Furthermore, the outline of the welding boss is larger than the outline of the boss part.

[0020] Furthermore, the single-sided allowance of the contour of the welding boss is 1-2 mm.

[0021] Furthermore, the process of machining a boss part that matches the welding boss specifically involves:

[0022] The welding surface of the boss part is consistent with the outer surface of the casing body part, and the remaining surfaces of the boss part are reserved with a preset allowance.

[0023] Furthermore, the preheating of the boss part located on the vibration side using a heating coil before welding specifically involves:

[0024] Before welding, the heating coil is placed at the position of the boss part near the friction surface. Before welding, the interface temperature is heated to 20-100°C below the material phase transformation point, and the welding boss is not heated.

[0025] Furthermore, the simultaneous linear friction welding of the casing body part and the boss part specifically involves:

[0026] The frequency of linear friction welding is 60-120Hz, the amplitude is 0.5-1mm, and the friction pressure per unit area is 10-50MPa.

[0027] Furthermore, the heating temperature of the post-weld heating coil is 20–100°C below the material phase transformation point.

[0028] Furthermore, the preset time is 20 to 100 seconds.

[0029] (3) Beneficial effects

[0030] In summary, this invention effectively improves material utilization, reduces material costs and subsequent machining costs through spin forming. Linear friction welding requires less heat input, thus minimizing welding deformation. Preheating the boss parts on the vibrating side with heating coils reduces frictional heat generation time, thereby reducing the height of the pre-fabricated welding bosses on the casing and facilitating the spin forming process. Ultimately, this enables the efficient, reliable, and low-cost manufacturing of thin-walled casings. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 A schematic diagram of a typical casing;

[0033] Figure 2 This is a schematic flowchart of a method for manufacturing a casing according to an embodiment of the present invention;

[0034] Figure 3 This is a schematic diagram of the external spin forming structure of a casing body part with a flange provided in an embodiment of the present invention;

[0035] Figure 4 This is a schematic diagram of the internal rotation structure of a casing cylinder part provided in an embodiment of the present invention;

[0036] Figure 5 This is a structural schematic diagram of a casing body part with a welding boss provided in an embodiment of the present invention;

[0037] Figure 6(a) is an axial view of a cylindrical boss provided in an embodiment of the present invention;

[0038] Figure 6(b) is a top view of a cylindrical boss provided in an embodiment of the present invention;

[0039] Figure 7(a) is an axial view of a rhomboid boss provided in an embodiment of the present invention;

[0040] Figure 7(b) is a top view of a rhomboid boss provided in an embodiment of the present invention;

[0041] Figure 8(a) is an axial view of a square boss provided in an embodiment of the present invention;

[0042] Figure 8(b) is a top view of a square boss provided in an embodiment of the present invention;

[0043] Figure 9This is a schematic diagram of an induction heating structure for a boss part provided in an embodiment of the present invention;

[0044] Figure 10 This is a schematic diagram of the structure of a formed casing provided in an embodiment of the present invention.

[0045] In the picture:

[0046] 1-Core mold; 2-Ring forging; 3-Roller; 4-Spinning part; 5-Support ring; 6-Segmentation mold; 7-Heating coil. Detailed Implementation

[0047] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present invention by way of example, but should not be used to limit the scope of the present invention, that is, the present invention is not limited to the described embodiments.

[0048] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0049] In the description of this invention, it should be understood that the terms "upper," "lower," "front," "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used to facilitate the description of this invention and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0050] Figure 2 This is a schematic flowchart of a method for manufacturing a casing according to an embodiment of the present invention, as shown below. Figure 2 As shown, the method may include the following steps:

[0051] S100. The ring forging is processed into a near-net-shape casing body part with welding bosses by spinning forming process.

[0052] Specifically, spin forming is a process for machining hollow rotating metal parts. It involves applying pressure to a rotating ring forging using tools such as spinning wheels, causing continuous, localized plastic deformation to form the part. The spin forming process begins by fixing the metal ring forging or a pre-made ring forging onto a mandrel in the spin forming equipment. The spindle drives the mandrel and the ring forging to rotate. Then, spinning wheels apply pressure to the ring forging at a specific trajectory and speed, causing continuous, point-by-point plastic deformation, thereby obtaining hollow rotating parts with various generatrice shapes.

[0053] Step S100 specifically includes the following steps:

[0054] S101. Apply force to the outer side of the ring forging by means of a spinning wheel to thin the middle area of ​​the ring forging.

[0055] S102. The thinned ring forging is fixed on the mandrel using a segmented die. A spinning wheel spins the ring forging inside the ring forging, so that the ring forging fills the groove of the segmented die under the action of extrusion pressure, forming a welding base.

[0056] Step S101: Using a ring-rolled part or a drawn straight cylinder as the blank (i.e., ring forging 2), the blank is fixed on the mandrel 1. A force is applied to the outside of the blank using a spinning wheel 3, thinning the middle area of ​​the blank. The ends of the blank are not spun or are only slightly thinned, ensuring sufficient allowance for machining the mounting edges. Finally, a spun part 4 is formed, thicker at both ends, thinner in the middle, and with increased overall height. Figure 3 As shown.

[0057] Step S102: To provide a base for welding the casing mounting base, a segmented mold 6 is used to fix the blank onto the core mold 1, and a support ring 5 is fitted over the outside of the segmented mold 6 to prevent it from falling off during rotation; a spinning wheel 3 is used to spin-form the blank inside, causing the blank to fill the groove of the mold under extrusion pressure, thus forming a welding base, such as... Figure 4 As shown.

[0058] Following the above method, complete the rotating casing body, and create a small boss structure on the outer side of the casing that protrudes 1-2 mm above the outer cylindrical surface. The boss outline is larger than the final boss outline, with a 1-2 mm allowance on each side. The final completed casing body is as follows: Figure 5 As shown, the end faces of various small bosses on the spun parts of the casing are machined to facilitate subsequent linear friction welding.

[0059] S200: Machining boss parts that are compatible with the welding boss.

[0060] Specifically, the welding surface of the boss component is consistent with the outer surface of the casing body component, and the remaining surfaces of the boss component have a pre-set allowance. Through the special design of the welding surface of the boss component, the welding reliability between it and the casing body can be improved.

[0061] The welding surfaces of all types of boss parts are consistent with the outer cylinder of the cylinder, with a radius of R; the remaining surfaces are left with different allowances as needed.

[0062] The pre-welding structure of the cylindrical boss is shown in Figures 6(a) and 6(b). "A" is the outer contour surface, with a 1-2 mm allowance left according to the welding process; "B" end face has a 10-20 mm allowance left according to the welding clamping requirements.

[0063] The pre-welding structure of the rhomboid boss is shown in Figures 7(a) and 7(b). "C" is the outer contour surface, with a 1-2 mm allowance left according to the welding process; "D" end face has a 10-20 mm allowance left according to the welding clamping requirements.

[0064] The pre-welding structure of the square boss is shown in Figure 8(a) and Figure 8(b). "E" is the outer contour surface, with a 1-2 mm allowance left according to the welding process; "F" end face has a 10-20 mm allowance left according to the welding clamping requirements.

[0065] S300: The boss part located on the vibration side is preheated by heating coil before welding. At the same time, the casing part and the boss part are linearly friction welded. After welding, the heating coil continues to heat and hold pressure for a preset time.

[0066] Specifically, linear friction welding (LFW) is a novel solid-state joining method. During the welding process, one workpiece vibrates at high frequency. Under the action of upsetting force, this workpiece comes into contact with another workpiece and rubs against it, generating frictional heat. The interface temperature rises rapidly, and the metals on both sides of the interface soften and undergo plastic flow. Under the action of upsetting force, the metals are squeezed out of the interface, forming flash. When the temperature distribution and deformation of the welding zone reach a certain level, the other workpiece quickly stops vibrating. The two workpieces are aligned and upsetting pressure is applied. The metals on both sides of the interface are joined together through mutual diffusion and recrystallization, thus completing the entire welding process. The microstructure of the LFW joint is a forged microstructure, with fewer joint defects and reliable performance. It has good welding adaptability for titanium alloys and is an important joining and manufacturing technology for future aircraft and engine structures. This invention uses LFW to significantly improve the connection strength of various bosses; LFW requires less heat input, which can reduce welding deformation.

[0067] Different welding fixtures and induction heating coils of different shapes are used for welding different bosses on a linear friction welding machine. Due to the thin wall of the cylinder, a heating coil 7 is placed near the friction surface of the boss (taking a rhomboid boss as an example) before welding. Figure 9 As shown, when the interface temperature is heated to 20–100°C below the material's phase transformation point before welding, the boss on the cylinder side is not heated. During vibration and welding, the heating coil continues to be energized and heated. This continuous heating before and during welding ensures that the shortening of the boss structure during welding is greater than the shortening of the cylinder side. In other words, it minimizes the shortening of the cylinder side, preventing it from being welded through and ensuring structural rigidity and dimensional accuracy.

[0068] Meanwhile, because the casing has a thin-walled structure, the welded surface bosses are relatively small, generally less than 300mm. 2Therefore, the selection of welding parameters should follow the principle of matching with small heat input to ensure the structural dimensions of the cylinder during welding. For the casing welding parameters, the frequency should be 60–120 Hz, the amplitude 0.5–1 mm, the friction pressure per unit area 10–50 MPa, and the total shrinkage after welding controlled within 0.5–2 mm. After the welding vibration stops, the welding pressure should be maintained for 20–100 seconds, while the coil continues to heat. When the temperature is controlled at 20–100°C below the phase transition point, the sequential combination welding process of linear friction welding followed by diffusion welding is achieved through heating and pressurization.

[0069] The advantages of this combined welding process are: (1) The total shrinkage is small, which can greatly reduce the shrinkage during the welding process on the cylinder side; (2) After the initial friction of linear friction welding, the near-field atoms on both sides of the friction interface can be fully activated, reducing the atomic diffusion activation energy; (3) During the process of stopping vibration and continuing heating and pressurization, the atoms on both sides of the friction interface activated by the friction welding process can quickly cross the interface and continue to diffuse with each other, ensuring that the joint achieves a reliable connection.

[0070] Cylindrical bosses are linearly friction-welded using annular induction heating coils, while square bosses are linearly friction-welded using square induction heating coils. The final welded casing body is as follows: Figure 10 As shown.

[0071] S400. After welding, the entire part undergoes post-weld heat treatment.

[0072] Specifically, the welded casing is installed on a heat treatment fixture and subjected to vacuum heat treatment and post-weld annealing according to the material stress relief annealing regime. This process eliminates welding stress and corrects the deformation of the casing caused by welding stress.

[0073] S500, after heat treatment, is CNC machined to obtain the finished casing.

[0074] Specifically, after heat treatment, the final casing model is CNC machined on a CNC machining equipment.

[0075] It should be noted that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. The present invention is not limited to the specific steps and structures described above and shown in the figures. Furthermore, for the sake of brevity, detailed descriptions of known methods and techniques are omitted here.

[0076] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art without departing from the scope of the invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of this application should be included within the scope of the claims of this application.

Claims

1. A method for manufacturing a casing, characterized in that, The method includes the following steps: The ring forging is processed into a near-net-shape casing body part with welding bosses using a spin forming process; Machining a boss part that matches the welding boss; The boss part located on the vibration side is preheated by heating coil before welding. At the same time, the casing part and the boss part are linearly friction welded. After welding, the heating coil continues to heat and hold pressure for a preset time to perform diffusion welding. After welding, the entire part undergoes post-weld heat treatment. After heat treatment, the casing is CNC machined to obtain the finished product; The process of machining the ring forging into a near-net-shape casing body part with welding bosses using a spin forming process specifically includes the following steps: A force is applied to the outer side of the ring forging by a spinning wheel, causing the middle region of the ring forging to be thinned. The thinned ring forging is fixed on the mandrel using a segmented die, and a spinning wheel spins the ring forging inside the ring forging, so that the ring forging fills the groove of the segmented die under the action of extrusion pressure, forming a welding base. The method of preheating the boss part located on the vibration side using a heating coil before welding is specifically as follows: Before welding, the heating coil is placed at the position of the boss part near the friction surface. Before welding, the interface temperature is heated to 20-100°C below the material phase transformation point, and the welding boss is not heated.

2. The method for manufacturing the casing according to claim 1, characterized in that, The height of the welding boss is 1-2 mm.

3. The method for manufacturing the casing according to claim 1, characterized in that, The outline of the welding boss is larger than the outline of the boss part.

4. The method for manufacturing the casing according to claim 3, characterized in that, The allowance on one side of the contour of the welding boss is 1-2 mm.

5. The method for manufacturing the casing according to claim 1, characterized in that, The specific steps involved in machining the boss part that matches the welding boss are as follows: The welding surface of the boss part is consistent with the outer surface of the casing body part, and the remaining surfaces of the boss part are reserved with a preset allowance.

6. The method for manufacturing the casing according to claim 1, characterized in that, The simultaneous linear friction welding of the casing body part and the boss part specifically involves: The frequency of linear friction welding is 60-120Hz, the amplitude is 0.5-1mm, and the friction pressure per unit area is 10-50MPa.

7. The method for manufacturing the casing according to claim 1, characterized in that, The heating temperature of the heating coil after welding is 20 to 100°C below the phase transformation point of the material.

8. The method for manufacturing the casing according to claim 1, characterized in that, The preset time is 20 to 100 seconds.

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