Composite forming method for deep cavity thin-walled titanium alloy structures

Abstract

A composite forming method for a deep-cavity thin-walled titanium alloy structure is disclosed. Based on the characteristics of the thin-walled deep-cavity structure, a deep-cavity thin-walled plate is formed separately by hot forming or electro-assisted forming. A nose cone is then machined by hot forming or cutting. The deep-cavity thin-walled plate and nose cone are then assembled and a mandrel is designed and machined based on the assembled structure. Finally, the three components are assembled into a single structure and then pressure-diffusion welded using a diffusion welding mold to obtain the thin-walled deep-cavity structure. This invention avoids material waste during the deep-cavity machining process. Furthermore, the weld surface is entirely located inside the deep-cavity thin-walled structure, and during service, the weld surface will not bear significant tensile loads. This helps prevent weld failure, fatigue, and fracture, thus promoting long-term service life.

Description

Technical Field

[0001] This invention relates to a technology in the field of aero-engine fan blade manufacturing, specifically a composite forming method for deep cavity thin-walled titanium alloy structures. Background Technology

[0002] Carbon fiber composite fan blades are lightweight and highly vibration-resistant, making them a mainstream choice for commercial aero engines. However, compared to metal blades, the leading edge of composite blades still has shortcomings in terms of impact and compressive strength. Therefore, by coating the leading edge of composite blades with titanium alloy reinforcing edges, the overall performance of the composite blades can be significantly improved. To accommodate the shape of the leading edge of composite fan blades, the titanium alloy reinforcing edges often have complex deep-cavity thin-walled structures. When directly machining deep-cavity thin-walled structures using cutting methods, the positional accuracy of slender cutting tools is difficult to control and unstable, resulting in low material utilization and high scrap rates. Therefore, there is an urgent need to find a suitable forming method for thin-walled deep-cavity titanium alloy structures. Summary of the Invention

[0003] This invention addresses the issue that existing prefabricated blade manufacturing technologies suffer from significant tensile loads on the welded surfaces, leading to defects such as incomplete welding and misalignment during diffusion welding. It proposes a composite forming method for deep-cavity thin-walled titanium alloy structures. This method avoids material waste during deep cavity machining, while ensuring the welded surfaces are entirely within the deep-cavity thin-walled structure. During service, the welded surfaces do not bear significant tensile loads, which helps prevent weld failure, fatigue, and fracture, thus promoting long-term service life.

[0004] This invention is achieved through the following technical solution:

[0005] This invention relates to a composite forming method for a deep-cavity thin-walled titanium alloy structure. Based on the characteristics of the thin-walled deep-cavity structure, a deep-cavity thin-walled plate is formed by thermoforming or electro-assisted forming, and a nose cone is processed by thermoforming or cutting. The deep-cavity thin-walled plate and the nose cone are then assembled and a core mold is obtained based on the assembled structure design and processing. After the three are assembled into an integral structure, they are pressure-diffusion welded using a diffusion welding mold to obtain the thin-walled deep-cavity structure.

[0006] The aforementioned thin-walled deep cavity structure features refer to: dividing the diffusion welding surface according to the geometric model of the thin-walled deep cavity structure, and then dividing the overall structure into two parts: a deep cavity thin-walled plate and a nose cone, with the contact part between the deep cavity thin-walled plate and the nose cone being defined as the diffusion welding surface.

[0007] The process of assembling the whole structure refers to: first, machining the contact surfaces of the deep cavity thin-walled plate and the nose cone to a mirror finish; then assembling the deep cavity thin-walled plate, the nose cone, and the core mold; using the core mold to support the inner cavity and ensure the accuracy of the inner side of the deep cavity; and finally placing the whole structure in a diffusion welding mold.

[0008] The inner cavity of the diffusion welding mold matches the outer shape of the deep cavity thin-walled plate to ensure the pressure applied to the surface to be welded during the pressure diffusion welding process and to control the accuracy of the outer shape of the deep cavity thin-walled plate.

[0009] In the aforementioned pressure diffusion welding, all contact surfaces except the surfaces to be welded are sprayed with a welding resist to prevent them from being welded together under high temperature and pressure.

[0010] The aforementioned supporting cavity refers to: the core mold, which applies pressure to the nose cone and promotes the contact and welding of the nose cone with the surface to be welded on the deep cavity thin-walled plate.

[0011] Both the core mold and the diffusion welding mold are made of heat-resistant stainless steel or high-temperature alloy.

[0012] Technical effect

[0013] This invention, through a rationally designed diffusion welding surface, avoids misalignment and displacement of the surfaces to be welded during the diffusion welding pressure application process. The thin-walled deep cavity structure is divided into two components: a deep cavity thin-walled plate and a nose cone. Both components can be formed independently using a simple and efficient forming method. By rationally designing the diffusion welding surface, the thin-walled deep cavity plate completely encloses the nose cone, with the welding surface located inside the deep cavity thin-walled structure. Compared to existing technologies, this invention improves the overall integrity of the diffusion-welded thin-walled deep cavity titanium alloy structure. The mandrel not only provides support to the inner side of the deep cavity but also applies pressure to the surfaces to be welded, promoting metallurgical bonding between the two surfaces. This significantly improves the forming efficiency of the thin-walled deep cavity titanium alloy structure. During service, the welding surface will not bear large tensile loads, which helps avoid structural desoldering, fatigue, and fracture failures, thus promoting the long-term service of the diffusion-welded thin-walled deep cavity titanium alloy structure. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the thin-walled deep-cavity titanium alloy structure of the present invention;

[0015] Figure 2 This is a schematic diagram of the core mold structure of the present invention;

[0016] Figure 3 This is a schematic diagram of the pressure diffusion welding process of the present invention;

[0017] Figure 4 This is a schematic diagram illustrating the effects of an embodiment of the present invention;

[0018] In the figure: 1 Thin-walled deep cavity titanium alloy structure, 2 Thin-walled deep cavity plate, 3 Nose cone, 4 Core mold, 5 Diffusion welding upper mold, 6 Diffusion welding lower mold. Detailed Implementation

[0019] like Figure 1As shown, this embodiment relates to a composite forming method for a deep-cavity thin-walled titanium alloy structure, comprising:

[0020] S1: Based on the characteristics of the thin-walled deep-cavity titanium alloy structure 1, the deep-cavity thin-walled plate 2 and the nose cone 3 are pre-divided and processed into their respective shapes, specifically including:

[0021] S11: Divide the diffusion welding surface according to the geometric model of the thin-walled deep cavity structure 1, and then divide the overall structure into two parts: the deep cavity thin-walled plate 2 and the nose cone 3. The contact part between the deep cavity thin-walled plate 2 and the nose cone 3 is determined as the diffusion welding surface.

[0022] S12: The deep cavity thin-walled plate 2 is formed by thermoforming or electric-assisted forming, and the nose cone 3 is processed by thermoforming or cutting.

[0023] Step S2: The processed deep cavity thin-walled plate 2 and nose cone 3 are spliced ​​together, and then these two parts are diffused together to obtain the thin-walled deep cavity titanium alloy structure 1, specifically including:

[0024] S21: As Figure 2 As shown, the core mold 4 is designed and processed according to the structure of the deep cavity thin-walled plate 2 and the nose cone 3. The outer surface shape of the core mold 4 is consistent with the cavity structure formed by the deep cavity thin-walled plate 2 and the nose cone 3, and is used to support the inner cavity in the subsequent processing to ensure the accuracy of the inner side of the deep cavity.

[0025] S22: The contact surfaces of the deep cavity thin-walled plate 2 and the nose cone 3 are machined to a mirror finish using mechanical, chemical, and other treatment methods, and the surfaces to be welded are cleaned with anhydrous ethanol.

[0026] S23: Assemble the deep cavity thin-walled plate 2, nose cone 3 and core mold 4 to form an integral structure, and place the integral structure between the upper mold 5 and the lower mold 6 of a diffusion welding mold.

[0027] S24: Place the diffusion welding mold into the vacuum diffusion furnace and evacuate the furnace to a vacuum level of 5×10⁻⁶. -5 Pa, apply a pressure of 5MPa to the top and bottom of the mold, heat to 900℃ at a rate of 10℃ / min, and hold at 900℃ for 1 hour to perform diffusion welding.

[0028] like Figure 2 As shown. During the diffusion welding process, the upper diffusion welding mold 5 and the lower diffusion welding mold 6, in addition to providing support, also shape the overall structure, ensuring the shape accuracy of the outer side of the deep-cavity thin-walled titanium alloy structure 1. After diffusion welding, the target thin-walled deep-cavity structure 1 is obtained.

[0029] Except for the surfaces to be welded, all other contact surfaces should be coated with solder resist. In particular, the contact surfaces between the core mold 4 and the thin-walled deep cavity plate 2 and the nose cone 3, as well as the contact surfaces between the thin-walled deep cavity plate 2 and the diffusion welding upper mold 5 and the diffusion welding lower mold 6.

[0030] In addition to providing basic support for the inner cavity, the core mold 4 should have a length along the depth direction of the inner cavity that is greater than the length of the thin-walled plate 2 of the deep cavity. This allows the core mold 4 to apply a pressure perpendicular to the surface to be welded when the vacuum diffusion furnace applies vertical pressure to the upper mold 5 and the lower mold 6 after the mold is closed, thus promoting the formation of a reliable metallurgical joint on the surface to be welded.

[0031] Furthermore, to facilitate the placement of the core mold 4 in the thin-walled deep cavity plate 2 before diffusion welding and the removal of the core mold 4 from the deep cavity structure 1 after diffusion welding, the core mold 4 should be made into a block mold, with each block connected by an interlocking structure.

[0032] Through specific practical experiments, dimensional accuracy scanning was performed on the thin-walled deep-cavity titanium alloy structure 1 manufactured using the aforementioned diffusion welding process. The results showed good dimensional accuracy, with only a small negative deviation, ranging from 0 to -0.05 mm, occurring at the open end where there were no strict assembly requirements. Considering the usage characteristics of the thin-walled deep-cavity titanium alloy structure 1, these small negative tolerances are acceptable. Mechanical property testing was conducted on samples of the welded joints of the thin-walled deep-cavity titanium alloy structure 1 manufactured using the aforementioned diffusion welding process. The tensile strength of the material after diffusion welding was 802 MPa, a decrease of only 9.5% compared to the original material's tensile strength of 887 MPa.

[0033] Compared with existing technologies, this method improves the overall integrity of thin-walled deep-cavity titanium alloy structures after diffusion welding and improves the forming accuracy of thin-walled deep-cavity titanium alloy structures, with only a small amount of negative deviation in areas without strict assembly requirements.

[0034] The above-described specific implementations can be partially adjusted by those skilled in the art in different ways without departing from the principles and purpose of the present invention. The scope of protection of the present invention is defined by the claims and is not limited to the above-described specific implementations. All implementation schemes within the scope of the claims are bound by the present invention.

Claims

1. A composite forming method for a deep-cavity thin-walled titanium alloy structure, characterized in that, Based on the characteristics of the deep cavity thin-walled structure, the deep cavity thin-walled plate is formed by thermoforming or electric assisted forming, and the nasal cone is processed by thermoforming or cutting. The deep cavity thin-walled plate and the nasal cone are then assembled and a core mold is designed and processed based on the assembled structure. After the three are assembled into an integral structure, the deep cavity thin-walled structure is obtained by pressure diffusion welding using a diffusion welding mold. The aforementioned deep cavity thin-walled structure features refer to: dividing the diffusion welding surface according to the geometric model of the deep cavity thin-walled structure, and then dividing the overall structure into two parts: a deep cavity thin-walled plate and a nose cone, with the contact part between the deep cavity thin-walled plate and the nose cone being defined as the diffusion welding surface; The assembly to form an integral structure refers to: first, machining the contact surfaces of the deep cavity thin-walled plate and the nose cone to a mirror finish, then assembling the deep cavity thin-walled plate, the nose cone, and the core mold, using the core mold to support the inner cavity and ensure the accuracy of the inner side of the deep cavity, and finally placing the integral structure in a diffusion welding mold; The inner cavity of the diffusion welding mold matches the outer shape of the deep cavity thin-walled plate to ensure the pressure applied to the surface to be welded during the pressure diffusion welding process and to control the accuracy of the outer shape of the deep cavity thin-walled plate. In the aforementioned pressure diffusion welding, except for the surface to be welded, all other contact surfaces are sprayed with a welding resist to prevent them from being welded together under high temperature and pressure. The aforementioned supporting cavity refers to the core mold applying pressure to the nose cone and promoting contact and welding between the nose cone and the surface to be welded on the deep cavity thin-walled plate.

2. The composite forming method for deep-cavity thin-walled titanium alloy structures according to claim 1, characterized in that, specifically... include: S1: Based on the characteristics of the deep cavity thin-walled titanium alloy structure, the deep cavity thin-walled plate and the nose cone are pre-separated and processed separately, specifically including: S11: Divide the diffusion welding surface according to the geometric model of the deep cavity thin wall structure, and then divide the overall structure into two parts: the deep cavity thin wall plate and the nose cone (3). The contact part between the deep cavity thin wall plate and the nose cone is determined as the diffusion welding surface. S12: The deep cavity thin-walled plate is formed by thermoforming or electric-assisted forming, and the nose cone is processed by thermoforming or cutting. Step S2: The processed deep cavity thin-walled plate and the nose cone are spliced ​​together, and then these two parts are diffused together to obtain a deep cavity thin-walled titanium alloy structure, specifically including: S21: Design and process the core mold according to the structure after the deep cavity thin-walled plate and the nose cone are assembled. The outer surface shape of the core mold is consistent with the cavity structure formed by the deep cavity thin-walled plate and the nose cone. It is used to support the inner cavity in the subsequent processing to ensure the accuracy of the inner side of the deep cavity. S22: Machin the contact surface of the deep cavity thin-walled plate and the nose cone to a mirror finish, and clean the surface to be welded with anhydrous ethanol; S23: Assemble the deep cavity thin-walled plate, nose cone and core mold to form an integral structure, and place the integral structure between the upper and lower molds of a diffusion welding mold; S24: Place the diffusion welding mold into a vacuum diffusion furnace, evacuate the furnace, apply pressure to the mold from top to bottom, raise the temperature to 900°C at a rate of 10°C / min, and hold at 900°C for 1 hour to perform diffusion welding.

3. The composite forming method for deep-cavity thin-walled titanium alloy structures according to claim 1, characterized in that, Solder resist is sprayed between the contact surfaces of the core mold and the deep cavity thin-walled plate and the nose cone, as well as between the contact surfaces of the deep cavity thin-walled plate and the diffusion welding upper mold and the diffusion welding lower mold.

4. The composite forming method for deep-cavity thin-walled titanium alloy structures according to claim 1, characterized in that, The length of the core mold along the depth direction of the inner cavity should be greater than the length of the thin-walled plate of the deep cavity, so that when the vacuum diffusion furnace applies vertical pressure to the upper and lower molds after the mold is closed, the core mold applies a pressure perpendicular to the surface to be welded, promoting the formation of a reliable metallurgical joint on the surface to be welded.

5. The composite forming method for deep-cavity thin-walled titanium alloy structures according to claim 1, characterized in that, The core mold is a modular mold, and the modules are connected by a fitting structure.

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