Machining method of special-shaped thin-walled ball

Abstract

The invention relates to a method for machining a special-shaped thin-walled ball. The method is carried out according to the following process steps of solid solution aging, rough turning, rough milling, subzero treatment, finish milling, finish turning, grinding, polishing, linear cutting and inspection. In the grinding process, rough grinding, semi-fine grinding and fine grinding are sequentially carried out on a machine tool through a self-made grinding tool, the roundness of the spherical surface is improved, and the surface roughness is improved. The precision machining method for the spherical structure of the high-temperature alloy material meeting the requirements is effectively achieved, the process requirement is simple and clear, and the requirements for the machining precision and the surface roughness of the part can be reliably met.

Description

Technical Field

[0001] The present invention belongs to the technical field of manufacturing of liquid oxygen methane engines, and particularly relates to a processing method for a special-shaped thin-walled sphere. Background Art

[0002] As the core component of the ball valve of the liquid oxygen methane engine, the special-shaped thin-walled sphere plays an important role in regulating the flow rate and shutting down / starting up. Especially in a low-temperature environment, the sealing performance between the sphere and the valve seat is related to whether the valve works properly.

[0003] The high-temperature alloy material has high material hardness and poor machinability. During machining, it has characteristics such as large cutting force, high cutting temperature, and serious work hardening phenomenon. The cutting tool is easily worn and the quality is difficult to guarantee, which is one of the difficulties. Due to the surface roughness of the spherical surface of the special-shaped thin-walled sphere being Ra0.1 μm and the profile tolerance being 0.01 mm, the accuracy requirement is high, and it is difficult to meet the requirements by conventional machining, which is the second difficulty; in addition, it has characteristics such as large diameter, thin wall, and irregular shape, and the wall thickness at the thinnest part is only 5 mm, belonging to the interrupted machining of typical thin-walled parts. Interrupted cutting will also bring great difficulties to ensuring the profile tolerance and surface roughness of the spherical surface, which is the third difficulty. Summary of the Invention

[0004] In view of the above deficiencies of the prior art, the present invention provides a processing method for a special-shaped thin-walled sphere. Through solution treatment and secondary aging treatment, the material strength is improved. Through a special grinding tooling, the surface roughness of the spherical part is improved, and the processing procedures are few and the cost is low.

[0005] The above object of the present invention is mainly achieved by the following technical solutions:

[0006] A processing method for a special-shaped thin-walled sphere includes the following steps:

[0007] (1) Perform solution aging treatment on the blank material; the solution treatment parameters are as follows: the furnace loading temperature is 950 - 980 °C, the holding temperature is 950 - 980 °C, the holding time is 75 - 80 min, and the cooling method is air cooling;

[0008] The aging treatment parameters are as follows: the furnace loading temperature for the first-stage aging is 710 - 730 °C, the holding temperature is 710 - 730 °C, the holding time is 450 - 500 min, and the time to drop to the second-stage aging temperature is ≥ 120 min; the holding temperature for the second-stage aging is 610 - 630 °C; the holding time is 450 - 500 min, and the cooling method is air cooling;

[0009] (2) Rough turn and rough mill the blank obtained in step (1), process the blank into a spherical surface, and machine the left end plane, right end plane, through hole, plane structures of the upper surface and lower surface, cam and chuck on the spherical surface. The chuck is arranged on the cam plane to obtain a spherical part;

[0010] (3) Perform cryogenic treatment on the spherical part obtained in step (2);

[0011] (4) Finish milling the outer shape of the spherical part obtained in step (3), finish turning the spherical surface and the through hole 205;

[0012] (5) Grind and polish the spherical part obtained in step (4);

[0013] (6) Remove the reserved chuck on the spherical part obtained in step (5), machine the spline 202 to obtain the special-shaped thin-walled sphere;

[0014] For the special-shaped thin-walled sphere, the upper surface and the lower surface of the sphere are plane structures, cams are respectively arranged on the upper surface and the lower surface plane structures, splines are respectively arranged on the cams, the left end spherical surface is provided with a left end plane, the right end spherical surface is connected to the upper surface plane and the lower surface plane to form a right end plane, and the connection with the spherical surface is smoothly processed; a through hole is arranged on the sphere, and the through hole penetrates through the front end spherical surface and the rear end spherical surface.

[0015] In step (2), the blank clamping method is one chuck and one center or double-spindle clamping. In the one chuck and one center method, one chuck means that one end of the blank is clamped by a chuck, and one center means that the other end of the blank is positioned by a center.

[0016] In step (2), the length of the chuck is 20 - 30 mm.

[0017] In step (3), the cryogenic treatment method is to keep warm in liquid nitrogen, the holding temperature is -196 ± 10 °C, the holding time is 120 - 125 min, and then cool to room temperature.

[0018] In step (4), finish turn the spherical surface to Φ118, leaving a margin of 0.05 ± 0.02 mm.

[0019] In step (4), the finish turning tool is a tool with R = 0.75 - 0.85, the spindle speed n = 250 - 350 r / min, the cutting amount is 0.13 - 0.17 mm, and the feed rate F = 0.02 - 0.04 mm / r.

[0020] In step (5), grind through the grinding tooling (1). The upper surface of the grinding tooling (1) is provided with a tooling chuck for spindle clamping, the lower end is cylindrical, and the lower surface is provided with an annular protrusion for grinding the spherical surface.

[0021] The grinding tooling (1) rotates around the Z-axis, and the spherical part rotates simultaneously. Rough grinding, semi-finish grinding, and finish grinding are carried out in sequence. The rotation speed of the grinding tooling during rough grinding is 40 - 45 r / min, the rotation speed of the spherical part is 20 - 25 r / min, and the abrasive grain size is W40 - W50; the rotation speed of the grinding tooling during semi-finish grinding is 35 - 40 r / min, the rotation speed of the part is 15 - 20 r / min, and the abrasive grain size is W10 - W20; the rotation speed of the grinding tooling during finish grinding is 30 - 35 r / min, the rotation speed of the part is 10 - 15 r / min, and the abrasive grain size is W5 - W7.

[0022] The height of the annular protrusion is 30 - 40 mm.

[0023] The surface roughness, position tolerance, and roundness of the special-shaped thin-walled ball obtained in step (6) are detected. If they do not meet the requirements, the operations described in steps (4) to (6) are repeated until the requirements are met.

[0024] The present invention has at least the following beneficial effects compared with the prior art:

[0025] (1) By optimizing the solution aging process parameters, the present invention improves the strength and machining performance of the spherical part, which is beneficial to the grinding process.

[0026] (2) The preferred grinding tooling in the embodiment of the present invention can perform rapid and precise machining on the ball valve core. It not only has fewer machining processes, lower machining costs, but also is more suitable for mass production, and is worthy of popularization and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the special-shaped thin-walled ball of the present invention;

[0028] Figure 2 It is a three-dimensional view of the special-shaped thin-walled ball of the present invention;

[0029] Figure 3 It is a schematic diagram of the grinding process in the processing method of the special-shaped thin-walled ball of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] The present invention will be further described in detail below with reference to the drawings and specific embodiments:

[0031] As Figure 1 and Figure 2As shown, for the special-shaped thin-walled sphere 2, the upper surface and the lower surface of the sphere are planar structures. Cam 201 is respectively provided on the planar structures of the upper surface and the lower surface. Spline 202 is respectively provided on cam 201. Left-end plane 203 is provided on the left-end spherical surface. The connection between the right-end spherical surface and the planar structures of the upper surface and the lower surface is right-end plane 204, and the connection with the spherical surface is smoothed; a through hole 205 is provided on the sphere, and the through hole 205 penetrates through the front-end spherical surface and the rear-end spherical surface.

[0032] A processing method for a special-shaped thin-walled sphere is carried out according to the following process steps: solution aging, rough turning, rough milling, cryogenic treatment, finish milling, finish turning, grinding, polishing, wire cutting, inspection; in the grinding process, according to the way of a vertical grinding machine, rough grinding, semi-finish grinding, and finish grinding are carried out in sequence by using a grinding tooling. The grinding equipment includes the designed grinding tooling, and the tooling material is cast iron.

[0033] Further, the part is driven to rotate by the spindle in the X direction of the machine tool, and the grinding tooling 1 is driven to rotate by the spindle in the Z direction of the machine tool, and the spindle in the Z direction passes through the center of the part of the sphere, and grinding is carried out through a certain pressure and mechanical movement.

[0034] A processing method for a special-shaped thin-walled sphere includes the following steps:

[0035] (1) Perform solution aging treatment on the blank material;

[0036] (2) Rough turn and rough mill the blank material obtained in step (1), process the blank material into a spherical surface, and process left-end plane 203, right-end plane 204, through hole 205, the planar structures of the upper surface and the lower surface, cam 201, and a chuck on the spherical surface. The chuck is arranged on the planar surface of cam 201 to obtain a spherical surface part;

[0037] Leave a margin of 1 mm on the spherical surface;

[0038] (3) Perform cryogenic treatment on the spherical surface part obtained in step (2);

[0039] (4) Finish mill the outer shape of the spherical surface part obtained in step (3), finish turn the spherical surface and through hole 205, improve the surface roughness, and leave a margin of 0.05 mm;

[0040] (5) Grind and polish the spherical surface part obtained in step (4) to further improve the surface quality of the spherical surface;

[0041] (6) Remove the chuck of the spherical surface part obtained in step (5) by wire cutting, and process spline 202 and the platform of the right-end spherical surface to obtain a special-shaped thin-walled sphere.

[0042] In step (1), the solution treatment parameters are as follows: the furnace loading temperature is 965 ± 15 °C, the holding temperature is 965 ± 15 °C, the holding time is 75 - 80 min, and then it is cooled to room temperature in air.

[0043] In step (1), the aging treatment parameters are as follows: for the first-stage aging, the furnace loading temperature is 720 ± 10 °C, the holding temperature is 720 ± 10 °C, the holding time is 450 - 500 min, the time to reduce to the second-stage aging temperature: ≥ 120 min; for the second-stage aging, the holding temperature is 620 ± 10 °C; the holding time is 450 - 500 min; and then it is cooled to room temperature in air. Solution aging treatment can make the material have better mechanical properties and tissue uniformity, improve the machining accuracy and surface integrity, and reduce the tool wear during the machining process.

[0044] In step (2), when machining the spherical surface, the clamping method is one-clamp-one-center or double-spindle clamping method to ensure the stability of finish machining. Among them, one-clamp-one-center means clamping one end of the part through the chuck and positioning the other end with the center; considering that there is no available chuck during the actual machining of the spherical part, chucks with a length of 20 - 30 mm are respectively left at both ends of the cam 201, and finally the chucks are cut off by wire cutting.

[0045] In step (3), the cryogenic treatment method is to hold in liquid nitrogen, the holding temperature is -196 ± 10 °C, the holding time is 120 - 125 min, and then it is cooled to room temperature.

[0046] In step (4), the spherical surface is finish-turned to Φ118 by one-clamp-one-center or double-spindle clamping method, with a margin of 0.05 ± 0.02 mm reserved. During the actual turning process, due to the space limitation of the cam 201 parts at both ends of the spherical valve core, a tool with R = 0.8 ± 0.05 is selected, the spindle speed n = 300 ± 50 r / min, the cutting amount is 0.15 ± 0.02 mm, and the feed rate F = 0.03 ± 0.01 mm / r. A smaller cutting force can be obtained, and a better state will be obtained for the easily deformable parts to ensure the machining requirements of the spherical surface size and its surface profile.

[0047] Design the grinding tooling 1 according to the machining form of the vertical grinding machine, as Figure 3As shown in the figure, a tool chuck 101 is provided on the upper surface of the grinding tooling 1 for spindle clamping. The lower end is cylindrical, and an annular protrusion 102 is provided on the lower surface. The height of the annular protrusion 102 is 30 - 40 mm, which is used for grinding the spherical surface. The opening diameter of the grinding tooling 1 is the same as the spherical surface of the GH4169 special-shaped thin-walled ball 2, and it can cover the entire spherical surface. The grinding tooling 1 rotates around the Z-axis at an angular velocity ω. At the same time, the machined ball part rotates at an angular velocity ω1. The grinding sequence is as follows: rough grinding (tooling rotation speed 40 - 45 r / min, part rotation speed 20 - 25 r / min, abrasive grain size W40 - W50), semi-finish grinding (tooling rotation speed 35 - 40 r / min, part rotation speed 15 - 20 r / min, abrasive grain size W10 - W20), finish grinding (tooling rotation speed 30 - 35 r / min, part rotation speed 10 - 15 r / min, abrasive grain size W5 - W7).

[0048] Example 1

[0049] A processing method for GH4169 special-shaped thin-walled balls includes the following steps:

[0050] (1) Solution treatment and aging treatment

[0051] Solution treatment: The blank is subjected to solution treatment using an ordinary resistance furnace; the furnace loading temperature is 965 °C, the loading method is loose, and it can be placed on a tray; the holding temperature is 965 °C, the holding time is 75 min, and the cooling method is air cooling.

[0052] Aging treatment: Aging treatment is carried out using an air resistance furnace. Loading method: Loosely placed on a tray or the furnace bottom plate; the first-stage aging furnace loading temperature is 720 °C, the holding temperature is 720 °C, the holding time is 480 min, and the time to drop to the second-stage aging temperature is 120 min; the second-stage aging holding temperature: 620 °C; the holding time: 480 min; the cooling method: Air-cooled to room temperature.

[0053] (2) Rough turning

[0054] When machining the spherical surface, double-spindle clamping is adopted to ensure the stability of finish machining. Clamps with a length of 25 mm are left at both ends of the cam 201. A margin of 1 mm is reserved on the spherical surface.

[0055] (3) Rough milling to machine the front and rear end faces.

[0056] (4) Cryogenic treatment

[0057] Loading method: Loose; when using a liquid nitrogen tank, the parts must be kept below the liquid level; the holding temperature is -196 °C, the holding time is 120 min; the cooling medium: Air; the cooling method: Air-cooled to room temperature. The function of cryogenic treatment: Increase the hardness of the material, improve the dimensional accuracy and stability of the workpiece, reduce the residual stress inside the part, and reduce the deformation during the machining process.

[0058] (5) Finish milling chuck and cam 201.

[0059] (6) Finish turning

[0060] Adopt the double-spindle clamping method to finish turning the spherical surface to Φ118, leaving a margin of 0.05 mm. Select a carbide tool with R = 0.8, the spindle speed n = 300 r / min, the cutting amount is 0.15 mm, and the feed rate F = 0.03 mm / r.

[0061] (7) Grinding

[0062] The grinding tooling rotates around the Z-axis at an angular velocity ω. At the same time, the spherical part to be processed rotates at an angular velocity ω1. The grinding sequence is as follows: rough grinding (tooling speed 40 r / min, part speed 20 r / min, abrasive grain size W40), semi-finish grinding (tooling speed 35 r / min, part speed 15 r / min, abrasive grain size W10), finish grinding (tooling speed 30 r / min, part speed 10 r / min, abrasive grain size W5).

[0063] (8) Polish the spherical surface to further improve the surface quality of the spherical surface.

[0064] (9) Wire cutting

[0065] Use wire cutting to remove the chuck, machine the spline 202 and the right-end spherical surface.

[0066] (10) Inspection

[0067] Use metrology and testing equipment to inspect the roundness, position and surface roughness of the ball according to the drawing requirements. The surface roughness is better than Ra0.1 um, and the profile tolerance is better than 0.01 mm.

[0068] The above is only the best specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention.

[0069] The content not detailed in the specification of the present invention belongs to the well-known technology of those skilled in the art.

Claims

1. A processing method for a special-shaped thin-walled sphere, characterized in that: It includes the following steps: (1) Perform solution aging treatment on the blank. The solution treatment parameters are as follows: the furnace loading temperature is 950 - 980°C, the holding temperature is 950 - 980°C, the holding time is 75 - 80 min, and the cooling method is air cooling; The aging treatment parameters are as follows: for the first-stage aging, the furnace loading temperature is 710 - 730°C, the holding temperature is 710 - 730°C, the holding time is 450 - 500 min, and the time to reduce to the second-stage aging temperature is ≥120 min; for the second-stage aging, the holding temperature is 610 - 630°C, the holding time is 450 - 500 min, and the cooling method is air cooling; (2) Rough turn and rough mill the blank obtained in step (1), process the blank into a spherical surface, and machine a left end plane (203), a right end plane (204), a through hole (205), planar structures on the upper and lower surfaces, a cam (201) and a chuck on the spherical surface, and the chuck is arranged on the plane of the cam (201) to obtain a spherical part; (3) Perform cryogenic treatment on the spherical part obtained in step (2); (4) Finish milling the outer shape of the spherical part obtained in step (3), and finish turning the spherical surface and the through hole (205); (5) Grind and polish the spherical part obtained in step (4); (6) Remove the reserved chuck of the spherical part obtained in step (5), and machine a spline (202) to obtain the special-shaped thin-walled sphere (2); For the special-shaped thin-walled sphere, the upper and lower surfaces of the sphere are planar structures, cams (201) are respectively arranged on the upper and lower surface planar structures, splines (202) are respectively arranged on the cams (201), a left end plane (203) is arranged on the left end spherical surface, the connection between the right end spherical surface and the upper and lower surface planes is the right end plane (204), and the connection with the spherical surface is smoothly processed; a through hole (205) is arranged on the sphere, and the through hole (205) penetrates through the front-end spherical surface and the rear-end spherical surface.

2. The processing method of a special-shaped thin-walled sphere according to claim 1, wherein: In step (2), the blank clamping method is one chuck and one center or double-spindle clamping. In the one chuck and one center method, one chuck is that one end of the blank is clamped by a chuck, and one center is that the other end of the blank is positioned by a center.

3. The processing method of a special-shaped thin-walled sphere according to claim 1, characterized in that: In step (2), the length of the chuck is 20 - 30 mm.

4. The processing method of a special-shaped thin-walled sphere according to claim 1, characterized in that: In step (3), the cryogenic treatment method is to hold in liquid nitrogen, the holding temperature is -196 ± 10°C, the holding time is 120 - 125 min, and then cool to room temperature.

5. The processing method of a special-shaped thin-walled sphere according to claim 1, characterized in that: In step (4), finish turning the spherical surface to Φ118, with a reserved margin of 0.05 ± 0.02 mm.

6. The processing method of a special-shaped thin-walled sphere according to claim 1, characterized in that: In step (4), the finish turning tool is a tool with R = 0.75 - 0.85, the spindle speed n = 250 - 350 r / min, the cutting amount is 0.13 - 0.17 mm, and the feed rate F = 0.02 - 0.04 mm / r.

7. The processing method of a special-shaped thin-walled sphere according to claim 1, characterized in that: In step (5), grinding is performed through a grinding tooling (1). The upper surface of the grinding tooling (1) is provided with a tooling chuck (101) for spindle clamping, the lower end is cylindrical, and the lower surface is provided with an annular protrusion (102) for grinding the spherical surface.

8. The processing method of a special-shaped thin-walled sphere according to claim 7, characterized in that: The grinding tooling (1) rotates around the Z-axis, and the spherical part rotates simultaneously. Rough grinding, semi-finishing grinding, and finishing grinding are carried out in sequence. During rough grinding, the rotational speed of the grinding tooling (1) is 40 - 45 r / min, the rotational speed of the spherical part is 20 - 25 r / min, and the abrasive grain size is W40 - W50; during semi-finishing grinding, the rotational speed of the grinding tooling (1) is 35 - 40 r / min, the rotational speed of the part is 15 - 20 r / min, and the abrasive grain size is W10 - W20; during finishing grinding, the rotational speed of the grinding tooling (1) is 30 - 35 r / min, the rotational speed of the part is 10 - 15 r / min, and the abrasive grain size is W5 - W7.

9. The processing method of a special-shaped thin-walled sphere according to claim 7, characterized in that: The height of the annular protrusion (102) is 30 - 40 mm.

10. The processing method of a special-shaped thin-walled sphere according to claim 1, characterized in that: The surface roughness, position accuracy, and roundness of the special-shaped thin-walled sphere (2) obtained in step (6) are detected. If the requirements are not met, the operations described in steps (4) to (6) are repeated until the requirements are met.

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