Manufacturing process of special-shaped hollow titanium alloy thin shell casting

Abstract

The present invention provides a manufacturing process for a special-shaped hollow titanium alloy thin shell casting, comprising: S1: computer modeling; S2: obtaining a product model; S3: module fixing; S4: sanding and slurrying; S5: roasting and forming; S6: pouring; S7: surface cleaning; S8: heat treatment; S9: welding; S10: annealing; the manufacturing process for the special-shaped hollow titanium alloy thin shell casting described in the present invention does not require a prefabricated core or separate preparation during the manufacturing process, thereby simplifying the casting process, improving the reliability of the casting quality and the production efficiency, and reducing the difficulty of shell making and shell cleaning operations.

Description

Technical Field

[0001] The invention relates to the technical field of investment casting, in particular to a manufacturing process of a special-shaped hollow titanium alloy thin shell casting. Background Art

[0002] Titanium alloy thin shell castings with special-shaped nearly closed cavities are common mechanical parts in the automotive and aviation industries. Their main function is to reduce weight or increase structural strength. The characteristics of this type of part are that the hollow inner cavity is a toroidal curved surface with a large cavity and a small mouth, and there is only a narrow opening on the end face of the connected double-arm outer flange. This toroidal nearly closed cavity cannot be properly painted or sanded during investment casting, and it is also difficult to clean the sand in the later stage. In the existing technology, investment casting of special-shaped closed or nearly closed cavity parts mostly adopts a split casting method. After the casting is completed separately, they are welded together to ensure the integrity of the cavity. However, the above method requires a lot of welding and grinding and finishing work, involves many processes, is difficult to weld, and generates large internal stress. It is easy to cause deformation and cracks in the casting of the welded assembly, and cannot meet product requirements. Another method is to use ceramic cores to form the mold channel in the entire inner cavity. Although this method meets the requirements of shell making, when the inner cavity is irregularly shaped, curved, too long, or almost closed, the casting may be unable to be cored out or the core may stick to the inner cavity after pouring, which increases casting costs and scrap rates.

[0003] The patent application with patent number CN112122545B, entitled "A method for preparing a reusable investment casting mold shell, a mold shell and a casting process", discloses that the investment mold is bonded to a base plate, and a rigid cylinder is placed on the outside of the investment mold, a refractory slurry is injected into the cavity between the rigid cylinder and the investment mold, the upper opening of the rigid cylinder is sealed with a top plate, and steam is used for autoclaving, and then roasted after autoclaving to obtain a finished investment casting mold shell. However, this method can only produce open mold shells, and cannot produce mold shells with special-shaped closed cavity structures. Summary of the Invention

[0004] In view of this, the present invention aims to propose a manufacturing process for special-shaped hollow thin shell castings to solve the problems of difficult and high cost in the prior art in manufacturing special-shaped hollow castings.

[0005] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0006] A manufacturing process for a special-shaped hollow titanium alloy thin shell casting, comprising:

[0007] S1: Computer modeling, establishing a three-dimensional model of the casting by computer according to the design parameters of the casting to be manufactured;

[0008] S2: Obtain a product model by using 3D printing to obtain a product model based on the three-dimensional model of the casting;

[0009] S3: Fix the mold assembly and bond the product model and the process hole sealing piece's melt mold assembly to the pouring system;

[0010] S4: Sanding and slurrying, applying slurry and sanding to the above-mentioned investment casting set from the inside to the outside;

[0011] S5: Firing and molding, firing the investment mold set at high temperature to obtain a finished shell with a certain strength;

[0012] S6: pouring, pouring the melted liquid titanium alloy into the mold shell, and after the liquid titanium alloy condenses, a cavity thin shell casting with a process hole and a process hole sealing piece can be obtained;

[0013] S7: Surface cleaning, shell cleaning and sand blasting of the titanium alloy casting after pouring;

[0014] S8: Heat treatment, heat treatment and strengthening of titanium alloy castings after shell cleaning and sandblasting;

[0015] S9: welding, welding the process hole sealing piece to the process hole of the titanium alloy casting;

[0016] S10: Annealing, stress relief annealing of titanium alloy castings.

[0017] Step S1 also includes:

[0018] a. Design shell making and cleaning holes in the internal cavity of the 3D model;

[0019] b. Design the pouring system of titanium alloy castings;

[0020] In step S2, the 3D printing includes fused deposition modeling, stereolithography, selective laser sintering, and the like.

[0021] In step S3, the investment set is bonded to the gating system by wax welding.

[0022] In step S7, a mechanical rod is inserted into the casting through the shell cleaning hole to clean the mold shell dust inside the casting.

[0023] In step S9, after the process hole sealing piece is welded to the titanium alloy casting, the welding part needs to be polished and trimmed to make the surface roughness and size meet the design requirements.

[0024] The manufacturing process of the special-shaped hollow titanium alloy thin shell casting described in the present invention does not require prefabricated cores or separate preparation during the manufacturing process, which simplifies the casting process, improves the reliability of casting quality and production efficiency, and reduces the difficulty of shell making and shell cleaning operations.

[0025] Furthermore, in step S1, shell making holes, shell cleaning holes and flanges are provided on the three-dimensional model, the shell making holes are provided at a position of the zigzag curved surface cavity of the casting facing the flange end, the shell making holes are used for spraying refractory sand, the shell cleaning holes are provided on the left and right outer walls of the zigzag curved surface cavity, and the shell cleaning holes are used for removing mold shell ash.

[0026] The shell making hole facilitates sanding inside the model during the early shell making process, and the shell cleaning hole can both sand the inside of the model during the early shell making process and remove mold shell ash during shell removal.

[0027] Furthermore, the shell making hole includes a first shell making hole and a second shell making hole, the flange includes a first flange and a second flange, and the first shell making hole and the second shell making hole are symmetrical with respect to a center line of a horizontal line connecting the first flange and the second flange.

[0028] This structure facilitates uniform sandblasting into the circular curved cavity to avoid dead corners.

[0029] Furthermore, the shell cleaning holes include a first shell cleaning hole, a second shell cleaning hole, a third shell cleaning hole and a fourth shell cleaning hole. The first shell cleaning hole and the third shell cleaning hole are symmetrical with respect to the center line of the horizontal line connecting the first flange and the second flange, and the second shell cleaning hole and the fourth shell cleaning hole are symmetrical with respect to the center line of the horizontal line connecting the first flange and the second flange.

[0030] This structure makes sandblasting and shelling more convenient.

[0031] Furthermore, the third and fourth radial positions of the shell inner cavity can be visually observed through the first and third shell cleaning holes, and the first and second radial positions of the shell inner cavity can be visually observed through the second and fourth shell cleaning holes.

[0032] This structure enables the mechanical rod to clean any position of the shell cavity through the shell cleaning hole, which is convenient for removing mold shell ash when shelling.

[0033] Furthermore, in step S4, the investment mold group sands and grouts the surface layer, transition layer and back layer from the inside to the outside, and sands the inner cavity of the model through the shell making holes and shell cleaning holes. The surface layer and transition layer are set to five layers. After the sanding of the surface layer and transition layer is completed, the shell making holes and shell cleaning holes are sealed and then sanding and grouting are performed.

[0034] Due to the thin wall of the cavity, this sand spreading and grouting method can ensure that the thickness of the inner cavity shell meets the strength requirements while reducing material and labor input, and at the same time reduces the difficulty of sand cleaning in the later zigzag curved surface cavity.

[0035] Furthermore, in step S6, the titanium alloy casting is cast using a top pouring and shower pouring system.

[0036] On the one hand, this pouring method can enhance the density of the casting and reduce internal shrinkage cavities and porosity. On the other hand, it has good filling properties and can reduce the number of repair welding parts and the amount of repair welding on the casting. It is particularly suitable for complex thin shell parts.

[0037] Furthermore, in step S8, the titanium alloy casting and the process hole sealing piece are heat treated in the same furnace after being formed, the heat treatment temperature is 890° C. to 950° C., and the holding time is 1 hour to 2.5 hours.

[0038] The titanium alloy casting and the process hole sealing piece can significantly improve the strength of the titanium alloy through the above heat treatment.

[0039] Furthermore, in the step S9, the heat-treated process hole sealing piece is polished and cleaned, and the process hole sealing piece and the process hole are welded by TIG welding.

[0040] Grinding and cleaning the process hole sealing piece can remove impurities on its surface, reduce its surface roughness, and facilitate welding operations.

[0041] Furthermore, a WS-400 argon arc welding machine is used, with a cerium tungsten electrode and an argon purity greater than 99.99%. Ventilation is required for a specified time before welding. During welding, both the front and back sides are protected by argon with a support cover. The diameter of the tungsten electrode is Φ3mm, the welding current is 50A~85A, and the argon flow rate is 16~20L / min.

[0042] The welding method in this application is simple to operate, has a fast welding speed, a small heat-affected zone, and small deformation of the workpiece during welding, which facilitates full-position automated welding. The weld is dense, the shape is beautiful, and the welding quality is excellent, and it is especially suitable for thin plate welding.

[0043] Furthermore, in the step S10, the titanium alloy casting is annealed in the same furnace after welding, the annealing temperature is 550-650° C., and the holding time is 1-2.5 hours.

[0044] Annealing of titanium alloy castings can reduce the residual stress generated during the casting and welding process, avoid deformation of the castings, and also enhance the corrosion resistance of the castings.

[0045] Compared with the prior art, the manufacturing process of the special-shaped hollow titanium alloy thin shell casting described in the present invention has the following advantages:

[0046] 1) Its manufacturing process is simple, achieving integrated molding of castings, effectively ensuring the contour of the closed circular arc cavity, improving the stability and reliability of casting production quality, and at the same time improving the efficiency of casting manufacturing;

[0047] 2) This manufacturing process reduces the difficulty of shell making and shell cleaning operations, ensuring the shell making quality and shell cleaning effect of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a schematic structural diagram of a casting mold shell according to an embodiment of the present invention from a first perspective;

[0049] Figure 2 This is a schematic structural diagram of the casting mold shell from a second perspective according to an embodiment of the present invention.

[0050] Description of reference numerals:

[0051] 1. Shell making hole; 11. First shell making hole; 12. Second shell making hole; 2. Shell cleaning hole; 21. First shell cleaning hole; 22. Second shell cleaning hole; 23. Third shell cleaning hole; 24. Fourth shell cleaning hole; 3. Flange; 31. First flange; 32. Second flange; 41. First position; 42. Second position; 43. Third position; 44. Fourth position; 100. Curved surface cavity. DETAILED DESCRIPTION

[0052] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0053] Example 1

[0054] like Figures 1-2 As shown, a manufacturing process of a special-shaped hollow titanium alloy thin shell casting includes:

[0055] S1: Computer modeling, establishing a three-dimensional model of the casting by computer according to the design parameters of the casting to be manufactured;

[0056] S2: Obtain a product model by using 3D printing to obtain a product model based on the three-dimensional model of the casting;

[0057] S3: Fix the mold assembly and bond the product model and the process hole sealing piece's melt mold assembly to the pouring system;

[0058] S4: Sanding and slurrying, applying slurry and sanding to the above-mentioned investment casting set from the inside to the outside;

[0059] S5: Firing and molding, firing the investment mold set at high temperature to obtain a finished shell with a certain strength;

[0060] S6: pouring, pouring the melted liquid titanium alloy into the mold shell, and after the liquid titanium alloy condenses, a cavity thin shell casting with a process hole and a process hole sealing piece can be obtained;

[0061] S7: Surface cleaning, shell cleaning and sand blasting of the titanium alloy casting after pouring;

[0062] S8: Heat treatment, heat treatment and strengthening of titanium alloy castings after shell cleaning and sandblasting;

[0063] S9: welding, welding the process hole sealing piece to the process hole of the titanium alloy casting;

[0064] S10: Annealing, stress relief annealing of titanium alloy castings.

[0065] Step S1 also includes:

[0066] a. Design shell making hole 1 and shell cleaning hole 2 in the internal cavity of the 3D model;

[0067] b. Design the pouring system of titanium alloy castings;

[0068] In step S2, the 3D printing includes fused deposition modeling, stereolithography, selective laser sintering, and the like.

[0069] In step S3, the investment set is bonded to the gating system by wax welding.

[0070] In step S7, a mechanical rod is inserted into the casting through the shell cleaning hole 2 to clean the shell dust inside the casting.

[0071] In step S9, after the process hole sealing piece is welded to the titanium alloy casting, the welding part needs to be polished and trimmed to make the surface roughness and size meet the design requirements.

[0072] The manufacturing process of the special-shaped hollow titanium alloy thin shell casting described in the present invention provides a shell making hole 1 and a shell cleaning hole 2 on the model, which is convenient for sanding the inside of the model during the early shell making and for removing the mold shell ash during shell removal. The top pouring and rain-type casting system is adopted, which can reduce internal shrinkage cavities and shrinkage, and at the same time reduce the number of repair welding parts and the amount of repair welding of the casting, thereby improving the quality and efficiency of casting.

[0073] This manufacturing process does not require prefabricated cores or separate preparation during the manufacturing process, which simplifies the casting process, improves the reliability of casting quality and production efficiency, and reduces the difficulty of shell making and shell cleaning operations.

[0074] As a preferred example of the present invention, in step S1, a shell making hole 1, a shell cleaning hole 2 and a flange 3 are provided on the three-dimensional model, the shell making hole 1 is provided at a position where the zigzag curved surface cavity 100 of the casting is opposite to the end of the flange 3, the shell making hole 1 is used for spraying refractory sand, the shell cleaning hole 2 is provided on the left and right outer walls of the zigzag curved surface cavity 100, and the shell cleaning hole 2 is used to remove mold shell ash.

[0075] Specifically, the shell making hole 1 is a circular hole with a diameter of 25 mm>D>20 mm, and the shell cleaning hole 2 is an elliptical hole with a major axis of 35 mm>X>30 mm and a minor axis of 25 mm>Y>20 mm.

[0076] The shell making hole 1 is convenient for sanding the inside of the model during the early shell making process, and the shell cleaning hole 2 can both sand the inside of the model during the shell making process and remove the mold ash during the shell removal process.

[0077] As a preferred example of the present invention, the shell making hole 1 includes a first shell making hole 11 and a second shell making hole 12, and the flange 3 includes a first flange 31 and a second flange 32. The first shell making hole 11 and the second shell making hole 12 are symmetrical relative to the center line of the horizontal connecting line of the first flange 31 and the second flange 32.

[0078] Specifically, this structure facilitates uniform sandblasting into the meander-shaped curved cavity 100 to avoid dead corners.

[0079] As a preferred example of the present invention, the shell cleaning hole 2 includes a first shell cleaning hole 21, a second shell cleaning hole 22, a third shell cleaning hole 23 and a fourth shell cleaning hole 24. The first shell cleaning hole 21 and the third shell cleaning hole 23 are symmetrical with respect to the center line of the horizontal line connecting the first flange 31 and the second flange 32, and the second shell cleaning hole 22 and the fourth shell cleaning hole 24 are symmetrical with respect to the center line of the horizontal line connecting the first flange 31 and the second flange 32.

[0080] Specifically, this structure makes sandblasting and shelling operations more convenient.

[0081] As a preferred example of the present invention, the radial third position 43 and the radial fourth position 44 of the shell inner cavity can be visually observed through the first shell cleaning hole 21 and the third shell cleaning hole 23, and the radial first position 41 and the radial second position 42 of the shell inner cavity can be visually observed through the second shell cleaning hole 22 and the fourth shell cleaning hole 24.

[0082] Specifically, this structure enables the mechanical rod to clean any position of the shell cavity through the shell cleaning hole 2, which is convenient for removing mold shell dust when removing the shell.

[0083] As a preferred example of the present invention, in step S4, the investment mold group sands and grouts the surface layer, transition layer and back layer from the inside to the outside, and sands the inner cavity of the model through the shell making hole 1 and the shell cleaning hole 2. The surface layer and transition layer are set to five layers. After the sanding of the surface layer and transition layer is completed, the shell making hole 1 and the shell cleaning hole 2 are sealed and then sanding and grouting are carried out.

[0084] Specifically, the surface layer is close to the surface of the model, and its molding sand is relatively fine, which is convenient for replicating the texture of the mold shell. The back layer is far away from the surface of the model, and its molding sand is relatively coarse, has good air permeability and high strength, providing support for the mold shell. There is a transition layer between the surface layer and the back layer, which plays a connecting and supporting role.

[0085] Due to the thin wall of the cavity, this sand spreading and grouting method can ensure that the thickness of the inner cavity shell meets the strength requirements while reducing material and labor input, and at the same time reduces the difficulty of sand cleaning in the later zigzag curved surface cavity.

[0086] As a preferred example of the present invention, in step S6, the titanium alloy casting adopts a top pouring and shower pouring system.

[0087] Specifically, this pouring method can enhance the density of the casting and reduce internal shrinkage cavities and porosity on the one hand, and on the other hand, it has good filling properties and can reduce the number of repair welding parts and the amount of repair welding on the casting, which is particularly suitable for complex thin shell parts.

[0088] As a preferred example of the present invention, in step S8, the titanium alloy casting and the process hole sealing piece are heat treated in the same furnace after being formed, the heat treatment temperature is 890°C to 950°C, and the holding time is 1h to 2.5h.

[0089] Specifically, the titanium alloy casting and the process hole sealing piece can significantly improve the strength of the titanium alloy through the above-mentioned heat treatment.

[0090] As a preferred example of the present invention, in step S9, the heat-treated process hole sealing piece is polished and cleaned, and the process hole sealing piece and the process hole are welded by TIG welding.

[0091] Specifically, grinding and cleaning the process hole sealing piece can remove impurities on its surface, reduce its surface roughness, and facilitate welding operations.

[0092] As a preferred example of the present invention, a WS-400 argon arc welding machine is used, with a cerium tungsten electrode and an argon purity greater than 99.99%. Ventilation is required for a specified time before welding. During welding, both the front and back sides are protected by argon with a support cover. The diameter of the tungsten electrode is Φ3mm, the welding current is 50A~85A, and the argon flow rate is 16~20L / min.

[0093] Specifically, the welding method in this application is simple to operate, has a fast welding speed, a small heat-affected zone, and small deformation of the workpiece during welding, which facilitates full-position automated welding. The welds are dense, the shape is beautiful, and the welding quality is excellent, making it particularly suitable for thin plate welding.

[0094] As a preferred example of the present invention, in step S10, the titanium alloy casting is annealed in the same furnace after welding, the annealing temperature is 550-650° C., and the holding time is 1-2.5 hours.

[0095] Specifically, annealing of titanium alloy castings can reduce the residual stress generated during the casting and welding process, avoid deformation of the castings, and also enhance the corrosion resistance of the castings.

[0096] In summary, the manufacturing process of the special-shaped cavity titanium alloy thin shell casting described in the present invention has a simple manufacturing process, realizes the integrated molding of the casting, effectively ensures the contour of the closed circular arc cavity, improves the stability and reliability of the casting production quality, and at the same time improves the efficiency of casting manufacturing. In addition, this manufacturing process reduces the operational difficulty of shell making and shell cleaning, and ensures the shell making quality and shell cleaning effect of the product.

[0097] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the scope defined by the claims.

Claims

1. A manufacturing process for special-shaped hollow titanium alloy thin shell castings, characterized in that: include: S1: Computer modeling, establishing a three-dimensional model of the casting by computer according to the design parameters of the casting to be manufactured; S2: Obtain a product model by using 3D printing to obtain a product model based on the three-dimensional model of the casting; S3: Fix the mold assembly and bond the product model and the process hole sealing piece's melt mold assembly to the pouring system; S4: Sanding and slurrying, applying slurry and sanding to the above-mentioned investment casting set from the inside to the outside; S5: Firing and molding, firing the investment mold set at high temperature to obtain a finished shell with a certain strength; S6: pouring, pouring the melted liquid titanium alloy into the mold shell, and after the liquid titanium alloy condenses, a cavity thin shell casting with a process hole and a process hole sealing piece can be obtained; S7: Surface cleaning, shell cleaning and sand blasting of the titanium alloy casting after pouring; S8: Heat treatment, heat treatment and strengthening of titanium alloy castings after shell cleaning and sandblasting; S9: welding, welding the process hole sealing piece to the process hole of the titanium alloy casting; S10: Annealing, stress relief annealing of the titanium alloy casting; in the step S1, a shell making hole (1), a shell cleaning hole (2) and a flange (3) are provided on the three-dimensional model, the shell making hole (1) is provided at a position where the zigzag curved surface cavity (100) of the casting is opposite to the flange end, the shell making hole (1) is used for spraying refractory sand, the shell cleaning hole (2) is provided on the left and right outer walls of the zigzag curved surface cavity (100), and the shell cleaning hole (2) is used for removing mold shell ash; the flange (3) includes a first flange (31) and a second flange (32); the shell cleaning hole (2) includes a first shell cleaning hole (21), a second shell cleaning hole (22), a third shell cleaning hole (23) and a fourth shell cleaning hole (24), the first shell cleaning hole (21) and the third shell cleaning hole (23) are relative to the first flange ( The second shell cleaning hole (22) and the fourth shell cleaning hole (24) are symmetrical with respect to the center line of the horizontal line connecting the first flange (31) and the second flange (32); the second shell cleaning hole (22) and the fourth shell cleaning hole (24) are symmetrical with respect to the center line of the horizontal line connecting the first flange (31) and the second flange (32); the radial third position (43) and the radial fourth position (44) of the shell inner cavity can be visually observed through the first shell cleaning hole (21) and the third shell cleaning hole (23); the radial first position (41) and the radial second position (42) of the shell inner cavity can be visually observed through the second shell cleaning hole (22) and the fourth shell cleaning hole (24); the radial first position (41) and the radial second position (42) are located in the middle position of the upper side wall of the zigzag curved surface cavity, and the radial third position (43) and the radial fourth position (44) are located in the middle position of the lower side wall of the zigzag curved surface cavity.

2. The manufacturing process of a special-shaped hollow titanium alloy thin shell casting according to claim 1 is characterized in that: The shell making hole (1) comprises a first shell making hole (11) and a second shell making hole (12), wherein the first shell making hole (11) and the second shell making hole (12) are symmetrical relative to a center line of a horizontal line connecting the first flange (31) and the second flange (32).

3. The manufacturing process of a special-shaped hollow titanium alloy thin shell casting according to claim 1, characterized in that: In step S4, the investment mold group performs sanding and grouting on the surface layer, transition layer and back layer from the inside to the outside, and sanding the inner cavity of the model through the shell making hole (1) and the shell cleaning hole (2). The surface layer and transition layer are set to five layers. After the sanding of the surface layer and transition layer is completed, the shell making hole (1) and the shell cleaning hole (2) are sealed and then sanding and grouting are performed.

4. The manufacturing process of a special-shaped hollow titanium alloy thin shell casting according to claim 1 is characterized in that: In the step S8, the titanium alloy casting and the process hole sealing piece are heat treated in the same furnace after being formed, the heat treatment temperature is 890° C. to 950° C., and the holding time is 1 hour to 2.5 hours.

5. The manufacturing process of a special-shaped hollow titanium alloy thin shell casting according to claim 1, characterized in that: In the step S9, the heat-treated process hole sealing piece is polished and cleaned, and the process hole sealing piece and the process hole are welded by TIG welding.

6. The manufacturing process of a special-shaped hollow titanium alloy thin shell casting according to claim 5, characterized in that: A WS-400 argon arc welding machine with a cerium tungsten electrode and argon purity greater than 99.99% is used. Ventilation is required before welding. During welding, both the front and back sides are protected by argon with a support cover. The diameter of the tungsten electrode is Φ3mm, the welding current is 50A~85A, and the argon flow rate is 16~20L / min.

7. The manufacturing process of a special-shaped hollow titanium alloy thin shell casting according to claim 1, characterized in that: In the step S10, the titanium alloy casting is subjected to stress relief annealing in the same furnace after welding, the annealing temperature is 550-650° C., and the holding time is 1-2.5 hours.

Images