Titanium alloy thin-walled hemisphere machining method

Abstract

The application discloses a titanium alloy thin-wall hemisphere machining method, which comprises the following steps: S1, preparing a square plate and a sphere; S2, opening a through hole and a through hole on the square plate; S3, cutting the sphere into two halves to obtain two hemispheres; S4, preparing two casings and fixing the two casings to two end faces of the square plate; S5, vertically placing a mold; S6, preparing a spherical titanium alloy powder; S7, injecting the titanium alloy powder into a filling cavity; S8, connecting one end of an air extraction pipe with the through hole; S9, placing the mold into a heating furnace for heating, and extracting air in the filling cavity by using an air extraction device; S10, placing the mold into a hot isostatic pressing furnace; S11, removing the casings by using a machining device, and cutting off a first connecting column; and S12, polishing by using a polishing device to obtain a titanium alloy thin-wall hemisphere; the method has the advantages that the size precision can be improved, the machining difficulty is reduced, and the production efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of titanium alloy processing technology, and in particular relates to a method for processing thin-walled titanium alloy hemispheres. Background Technology

[0002] Titanium alloys have a density that is only 60% that of steel, but their strength can reach the level of many alloy steels. In addition, titanium alloys have excellent corrosion resistance and heat resistance. In recent years, they have become an important structural metal and are widely used in aerospace, marine engineering, energy and chemical industry and automobile manufacturing.

[0003] To achieve firefighting in super high-rise buildings, the country is vigorously promoting the development of rotary-wing firefighting drones. However, the carrying capacity of these drones is limited. Therefore, reducing the weight of the fire tank will help the drones carry more fire extinguishing agent. Thus, titanium and titanium alloys are currently the best manufacturing materials for this type of fire tank.

[0004] Fire tanks are typically spherical or ellipsoidal thin-walled shell structures. The manufacturing of thin-walled spherical metal shell structures is more complex than that of other conventional structural components. In particular, due to the unique physical and chemical properties of titanium alloys, they have poor plasticity and high springback, resulting in poor processability. Conventional metal plastic processing methods are difficult to obtain titanium alloy thin-walled hemispheres with high dimensional accuracy.

[0005] For example, the method for hot isostatic pressing (HIP) forming of a titanium alloy gas cylinder hemisphere disclosed in application number CN201810898438.4 utilizes HIP technology to sinter and form titanium alloy powder, and employs an internal mold and an external sheath to achieve certain features of the formed part and reduce post-processing. In this technical solution, the internal mold, base plate, and sheath form a storage space for the powder. The prepared spherical titanium alloy powder is loaded into the space and compacted by mechanical vibration. The titanium alloy powder below the top is restricted by the internal mold, base plate, and sheath, and can form a regular hemisphere shape. However, the upper end of the sheath has an opening for connecting the suction pipe, where there is a lack of restriction on the titanium alloy powder. After mechanical vibration, only the titanium alloy powder at the top can be made planar (see [link]). Figure 1 The density at this point is poor, and the thickness of the top of the arc surface of the sintered titanium alloy thin-walled hemisphere differs from that of other parts of the arc surface. It needs to be further processed by mechanical finishing, but mechanical finishing is more difficult for the arc surface, so there is still room for improvement. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for processing thin-walled titanium alloy hemispheres. By optimizing the processing technology, the dimensional accuracy can be improved, the processing difficulty can be reduced, and the production efficiency can be increased at the same time.

[0007] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: a method for processing thin-walled titanium alloy hemispheres, comprising the following steps:

[0008] S1. Prepare a square plate and a sphere;

[0009] S2. A through hole is made on the end face of the square plate, the through hole passing through both end faces of the square plate. A through hole is made on one side of the square plate, the through hole being connected to the middle of the through hole.

[0010] S3. Cut the sphere in half to obtain two hemispheres. Fix the two hemispheres to the two end faces of the square plate, and make sure that the hemispheres are not offset from the perforations.

[0011] S4. Prepare two sleeves, each corresponding to one of the two hemispheres. Fix the two sleeves to the two end faces of the square plate to obtain the mold. The sleeves, the corresponding hemispheres, and the square plate work together to form a hemispherical filling cavity. The perforation is connected to the filling cavity.

[0012] S5. Place the mold vertically so that the sleeve and hemisphere are located on both sides of the square plate in the horizontal direction, and the through hole is located on the top of the square plate, with the through hole extending in the vertical direction.

[0013] S6. Prepare spherical titanium alloy powder;

[0014] S7. Titanium alloy powder is injected into the filling cavity through through holes and perforations, and mechanical vibration is used to keep the titanium alloy powder in the filling cavity, perforations and through holes dense.

[0015] S8. Connect one end of the suction pipe to the through hole and the other end of the suction pipe to the suction device.

[0016] S9. Place the mold filled with titanium alloy powder into a heating furnace for heating, and use an air extraction device to extract the air from the filling cavity. After completion, clamp the air extraction pipe and seal it.

[0017] S10. Place the mold in a hot isostatic pressing furnace and sinter the spherical titanium alloy powder under high temperature and high pressure. Under the action of the mold, two titanium alloy thin-walled hemispherical semi-finished products, a first connecting column located in the perforation and a second connecting column located in the through hole are formed.

[0018] S11. Remove the casing using machining equipment and cut the first connecting column to remove the two titanium alloy thin-walled hemispherical semi-finished products;

[0019] S12. Grind the end faces of the two titanium alloy thin-walled hemispheres using a grinding machine to obtain the titanium alloy thin-walled hemispheres.

[0020] Preferably, in step S6, the titanium alloy powder is made of Ti-6Al-4V and has a particle size range of 40±5μm.

[0021] Preferably, in step S9, the temperature of the heating furnace is 400-480℃, the heating time is 2-4 hours, and the vacuum degree of the filling cavity is less than 1.0×10⁻⁶. -3 Pa.

[0022] Preferably, in step S10, the hot isostatic pressing parameters are: temperature range of 1000-1100℃, holding time of 4h-6h, argon gas is introduced into the hot isostatic pressing furnace during the heating process, and the mold is pressed by argon gas with a pressing pressure of 150-300MPa.

[0023] Preferably, the heating rate is 8-12℃ / min.

[0024] Preferably, after the heat preservation time is over, the mold is cooled with the furnace at a rate of 8-12℃ / min, and the pressure is released and the gas is released after the temperature drops below 50℃.

[0025] Preferably, the sheath has an outwardly convex arc surface, an inwardly concave arc surface, and a bottom surface, with the perforation tangent to or intersecting with the inner edge of the bottom surface of the sheath.

[0026] Preferably, the square plate is welded and fixed to the hemisphere, and the square plate is welded and fixed to the sleeve.

[0027] Preferably, the square plate is fixed to the hemisphere and the sleeve by brazing.

[0028] Preferably, the square plate, sphere, and sleeve are all made of 304 stainless steel.

[0029] Compared with the prior art, the advantages of the present invention are as follows:

[0030] 1. By setting perforations and through holes on the square plate, with the perforations connected to the filling cavity and the exhaust pipe connected to the through holes, it is possible to avoid setting openings on the sleeve. The complete sleeve and hemisphere can fully and tightly contact the filled titanium alloy powder, ensuring the integrity of the arc surface of the titanium alloy thin-walled hemisphere obtained by sintering. That is, the thickness of the top of the arc surface of the titanium alloy thin-walled hemisphere is highly consistent with the thickness of other parts of the arc surface, and the dimensional accuracy is good.

[0031] 2. By setting perforations and through holes on the square plate, and placing the mold vertically, injecting titanium alloy powder and performing mechanical vibration, if there are gaps in the filling cavity, the titanium alloy powder in the perforations and through holes will fill the filling cavity. The injection process only needs to confirm whether the titanium alloy powder in the through holes is decreasing, and the operation is relatively simple.

[0032] 3. Conventional filling cavities are short and wide, with a relatively wide overall width in the transverse direction. The density between the injected titanium alloy powders is generally low. However, the mold in this solution is placed vertically, and the filling cavity is long and thin, with a relatively narrow overall width in the transverse direction. After injecting titanium alloy powder and mechanical vibration, the density between the titanium alloy powders is higher.

[0033] 4. This method for processing thin-walled titanium alloy hemispheres can produce two thin-walled titanium alloy hemispheres in one step, which is more efficient than the conventional hot isostatic pressing method for forming titanium alloy gas cylinder hemispheres.

[0034] 5. By cutting a sphere into two hemispheres and then fixing the two hemispheres to the two end faces of a square plate, the inner diameters of the two titanium alloy thin-walled hemispheres prepared are well consistent, which facilitates the later fabrication of high-precision spherical thin-walled shell structures.

[0035] 6. After sintering, the cladding is removed using machining equipment, and the first connecting post is cut off to take out the two titanium alloy thin-walled hemisphere semi-finished products. Although the first connecting post is cut off on the semi-finished product, the first connecting post is located on the flat part of the semi-finished product. It can be cut and ground flat. Compared with the treatment of the arc surface, the processing difficulty is low and the processing efficiency is high.

[0036] 7. The square plate design, when connected with the hemisphere and the sleeve, has its four corners extending outside the sleeve. It can be used with machine tools and positioning fixtures to keep the mold in a vertical position, making it highly versatile. Attached Figure Description

[0037] Figure 1 Schematic diagram of a thin-walled titanium alloy hemisphere Figure 1 ;

[0038] Figure 2 Schematic diagram of a thin-walled titanium alloy hemisphere Figure 2 ;

[0039] Figure 3 This is a schematic diagram of the mold structure in this invention;

[0040] Figure 4 This is a cross-sectional structural diagram of the mold in this invention.

[0041] In the diagram: 1. Square plate; 11. Perforation; 12. Through hole; 2. Hemisphere; 3. Sheath; 4. Evacuation pipe. Detailed Implementation

[0042] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0043] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not 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 the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0044] Example: Figures 2 to 4 As shown, a method for processing a thin-walled titanium alloy hemisphere includes the following steps:

[0045] S1. Prepare square plate 1 and sphere;

[0046] S2. A through hole 11 is made on the end face of the square plate 1, the through hole 11 passes through both end faces of the square plate 1, and a through hole 12 is made on one side of the square plate 1, the through hole 12 is connected to the middle of the through hole 11.

[0047] S3. Cut the sphere in half to obtain two hemispheres 2. Weld the two hemispheres 2 to the two end faces of the square plate 1, and stagger the hemispheres 2 from the perforation 11.

[0048] S4. Prepare two sleeves 3, which correspond one-to-one with two hemispheres 2. Weld the two sleeves 3 to the two end faces of the square plate 1 to obtain the mold. The sleeves 3, the corresponding hemispheres 2 and the square plate 1 cooperate to form a hemispherical filling cavity. The perforation 11 is connected to the filling cavity.

[0049] S5. The mold is placed vertically so that the sleeve 3 and the hemisphere 2 are located on both sides of the square plate 1 in the horizontal direction, and the through hole 12 is located on the upper part of the square plate 1, and the through hole 12 extends in the vertical direction.

[0050] S6. Prepare spherical titanium alloy powder. The titanium alloy powder material is Ti-6Al-4V, and the particle size range is 40±5μm.

[0051] S7. Titanium alloy powder is injected into the filling cavity through through hole 12 and through hole 11, and mechanical vibration is used to keep the titanium alloy powder in the filling cavity, through hole 11 and through hole 12 dense.

[0052] S8. Connect one end of the suction pipe 4 to the through hole 12, and connect the other end of the suction pipe 4 to the suction device.

[0053] S9. Place the mold filled with titanium alloy powder into a heating furnace for heating, and extract the air from the filling cavity using an air extraction device. After completion, clamp the air extraction pipe 4 and seal it.

[0054] S10. Place the mold into a hot isostatic pressing furnace and sinter the spherical titanium alloy powder under high temperature and high pressure. Under the action of the mold, two titanium alloy thin-walled hemispherical semi-finished products, a first connecting column located in the perforation 11 and a second connecting column located in the through hole 12 are formed.

[0055] S11. Use machining equipment to remove the sleeve 3 and cut the first connecting column to remove the two titanium alloy thin-walled hemispherical semi-finished products.

[0056] S12. Grind the end faces of the two titanium alloy thin-walled hemispherical semi-finished products using a grinding equipment to obtain titanium alloy thin-walled hemispherical 2.

[0057] In step S9, the temperature of the heating furnace is 400-480℃, preferably 440℃, the heating time is 2-4 hours, preferably 3 hours, and the vacuum degree of the filling cavity is less than 1.0×10⁻⁶. -3 Pa, preferably 0.8 × 10 -3 Pa.

[0058] In step S10, the hot isostatic pressing parameters are as follows: temperature range of 1000-1100℃, preferably 1100℃; holding time of 4h-6h, preferably 5h; heating rate of 8-12℃ / min, preferably 10℃ / min; argon gas is introduced into the hot isostatic pressing furnace during the heating process, and the mold is pressurized by the argon gas at a pressure of 150-300MPa, preferably 200MPa. After the holding time is completed, the mold is cooled with the furnace at a cooling rate of 8-12℃ / min, preferably 10℃ / min, and the pressure is released after the temperature drops below 50℃.

[0059] In this embodiment, the sheath has an outwardly convex arc surface, an inwardly concave arc surface, and a bottom surface. The perforation is tangent (internal) or intersects with the inner edge of the bottom surface of the sheath, ensuring that the titanium alloy powder is fully filled into the filling cavity.

[0060] In this embodiment, the square plate is fixed to the hemisphere and the sleeve by brazing. The operating temperature is low, which can reduce the thermal impact on the base material, thereby reducing thermal stress and deformation, maintaining the mechanical properties and structural stability of the base material, with high connection strength and good stability, and good airtightness to avoid air leakage during the evacuation process.

[0061] In this embodiment, the square plate, the sphere, and the sleeve are all made of 304 stainless steel.

[0062] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the implementation of the present invention is not limited to the above-described manner. Any improvements made using the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A method for machining a thin-walled titanium alloy hemisphere, characterized in that... Includes the following steps: S1. Prepare a square plate and a sphere; S2. A through hole is made on the end face of the square plate, the through hole passing through both end faces of the square plate. A through hole is made on one side of the square plate, the through hole being connected to the middle of the through hole. S3. Cut the sphere in half to obtain two hemispheres. Fix the two hemispheres to the two end faces of the square plate, and make sure that the hemispheres are not offset from the perforations. S4. Prepare two sleeves, each corresponding to one of the two hemispheres. Fix the two sleeves to the two end faces of the square plate to obtain the mold. The sleeves, the corresponding hemispheres, and the square plate work together to form a hemispherical filling cavity. The perforation is connected to the filling cavity. S5. Place the mold vertically so that the sleeve and hemisphere are located on both sides of the square plate in the horizontal direction, and the through hole is located on the top of the square plate, with the through hole extending in the vertical direction. S6. Prepare spherical titanium alloy powder; S7. Titanium alloy powder is injected into the filling cavity through through holes and perforations, and mechanical vibration is used to keep the titanium alloy powder in the filling cavity, perforations and through holes dense. S8. Connect one end of the suction pipe to the through hole and the other end of the suction pipe to the suction device. S9. Place the mold filled with titanium alloy powder into a heating furnace for heating, and use an air extraction device to extract the air from the filling cavity. After completion, clamp the air extraction pipe and seal it. S10. Place the mold in a hot isostatic pressing furnace and sinter the spherical titanium alloy powder under high temperature and high pressure. Under the action of the mold, two titanium alloy thin-walled hemispherical semi-finished products, a first connecting column located in the perforation and a second connecting column located in the through hole are formed. S11. Remove the casing using machining equipment and cut the first connecting column to remove the two titanium alloy thin-walled hemispherical semi-finished products; S12. Grind the end faces of the two titanium alloy thin-walled hemispheres using a grinding machine to obtain the titanium alloy thin-walled hemispheres.

2. The method for processing a thin-walled titanium alloy hemisphere according to claim 1, characterized in that... In step S6, the titanium alloy powder is made of Ti-6Al-4V and has a particle size range of 40±5μm.

3. The method for processing a thin-walled titanium alloy hemisphere according to claim 1, characterized in that... In step S9, the temperature of the heating furnace is 400-480℃, the heating time is 2-4 hours, and the vacuum degree of the filling cavity is less than 1.0×10⁻⁶. -3 Pa.

4. The method for processing a thin-walled titanium alloy hemisphere according to claim 1, characterized in that... In step S10, the hot isostatic pressing parameters are: temperature range of 1000-1100℃, holding time of 4h-6h, argon gas is introduced into the hot isostatic pressing furnace during the heating process, and the mold is pressed by argon gas with a pressing pressure of 150-300MPa.

5. A method for processing a thin-walled titanium alloy hemisphere according to claim 4, characterized in that... The heating rate is 8-12℃ / min.

6. The method for processing a thin-walled titanium alloy hemisphere according to claim 4, characterized in that... After the heat preservation time is over, the mold is cooled with the furnace at a rate of 8-12℃ / min. After the temperature drops below 50℃, the pressure is released and the gas is released.

7. A method for processing a thin-walled titanium alloy hemisphere according to claim 1, characterized in that... The sheath has an outwardly convex arc surface, an inwardly concave arc surface, and a bottom surface, with the perforation tangent to or intersecting with the inner edge of the bottom surface of the sheath.

8. A method for processing a thin-walled titanium alloy hemisphere according to claim 1, characterized in that... The square plate is welded and fixed to the hemisphere, and the square plate is also fixed to the sleeve.

9. A method for processing a thin-walled titanium alloy hemisphere according to claim 8, characterized in that... The square plate is fixed to the hemisphere and to the sleeve by brazing.

10. A method for processing a thin-walled titanium alloy hemisphere according to claim 1, characterized in that... The square plate, sphere, and casing are all made of 304 stainless steel.

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