Machining method of top-mounted ball valve body

Abstract

The invention discloses a machining method of a top-mounted ball valve body, and belongs to the technical field of valve machining. Performing primary subzero treatment; performing semi-finish turning on the flanges at the two ends and the flow channel; performing semi-finish turning on the middle flange; performing nondestructive testing, performing rough milling on a threaded bottom hole of the middle flange, performing secondary subzero treatment, milling a finish machining reference of the valve body, finishing the flanges at the two ends and the flow channel, finishing the middle flange, and milling the threaded bottom hole of the middle flange. Boring a pollution discharge hole, and carrying out three-coordinate detection; through the machining steps, it is guaranteed that the final machining size and error meet the requirements of design drawings.

Description

Technical Field

[0001] The present invention relates to the technical field of valve processing, and in particular to a processing method for a top-mounted ball valve body. Background Art

[0002] The usual processing technology of ultra-low temperature top-entry ball valve body consists of four steps: rough processing, cryogenic treatment, fine processing, and manual inspection. Step 1: Rough processing method is as follows Figure 1 As shown in the positioning and clamping, large-diameter valve bodies are processed by vertical lathes, while small-diameter valve bodies are processed by horizontal lathes. The valve body is long in shape, and the support is very poor when processed on a horizontal lathe. The non-rotating body has a large centrifugal force and the protruding end swings greatly, making it difficult to ensure the coaxiality and roundness tolerances. In addition, the clamping safety is poor, so large-diameter valve bodies are more suitable for processing on vertical lathes. The second step: the cryogenic treatment process is conventionally performed only once, and it is difficult to completely eliminate the processing stress and dimensional strain at ultra-low temperatures. The third step: the finishing process method is the same as the clamping and verification method used in the first roughing process. For finishing, although the process datum of roughing is used, the coaxiality, roundness and parallelism of the flanges at both ends of the roughing datum itself will seriously exceed the design requirements, and it cannot guarantee that the product will be processed in full compliance with the requirements of the design drawings. Summary of the Invention

[0003] In order to overcome the deficiencies of the prior art, the present invention aims to solve the technical problem of how to improve the existing processing technology, which results in the valve body after processing not being able to fully meet the requirements of the design drawings.

[0004] The technical solution adopted by the present invention to solve its technical problem is: The processing method of the top-mounted ball valve body is characterized by comprising the following steps: S1: Marking inspection: First, clamp the valve body blank on the CNC vertical lathe workbench. Calibrate the clamping position of the valve body blank by adjusting the clamping structure of the CNC vertical lathe workbench. Use the lifting coordinate position of the CNC column tool rod and refer to the reference position of the valve body blank to determine the machining allowances of the flanges at both ends and other related positions and mark them with marks. S2: Rough turning the flanges and flow channels at both ends. CNC vertical lathes are used to rough turn the end face, outer circle, back face, flow channel and seat hole of the flange at one end of the valve body blank. Turn around and rough turn the end face, outer circle, back face, flow channel and seat hole of the flange at the other end of the valve body blank. Each machining position meets the preset machining allowance and form and position tolerances. S3: Rough boring of the center flange datum and rough turning of the center flange. Clamp the valve body on a CNC boring machine, align the center flange machining position with reference to the valve body datum position, and machine the datum. Clamp the valve body with the machined datum on a CNC vertical lathe, calibrate the position, and machine the center flange end face, inner hole, and bottom hole. Ensure that each machining position meets the preset machining allowance and form and position tolerances. S4: First cryogenic treatment, the valve body is subjected to the first cryogenic treatment; S5: Semi-finish turning the flanges and flow channels at both ends. Clamp the valve body after the first cryogenic treatment on a CNC vertical lathe. Semi-finish turning the end face, outer circle, back face, flow channel and seat hole of the flange at one end of the valve body blank. Then, turn around and semi-finish turn the end face, outer circle, back face, flow channel and seat hole of the flange at the other end of the valve body. Each processing position reaches the preset processing allowance and form and position tolerance. S6: Semi-finish turning the center flange, clamping the valve body on the CNC vertical lathe, calibrating the position, and then machining the center flange end face, inner hole and bottom hole; S7: Non-destructive testing, non-destructive testing of the processing parts of the valve; S8: Rough milling of the threaded bottom hole of the center flange, clamping the valve body to the gantry milling machine, calibrating the position, calibrating the center flange end face, inner hole and bottom hole position, and rough milling of the threaded bottom hole; S9: Second cryogenic treatment, subjecting the processed valve body to a second cryogenic treatment; S10: Milling the valve body finishing benchmark, clamping the valve body to the four-axis gantry milling machine, calibrating the position, and then machining the valve body machining benchmark; S11: Finish the flanges and flow channels at both ends. Clamp the valve body onto a CNC vertical lathe. After calibrating the position, finish the end face, outer circle, back face, flow channel and seat hole of the flange at one end of the valve body. Turn around and finish the end face, outer circle, back face, flow channel and seat hole of the flange at the other end of the valve body. Each processing position reaches the preset surface roughness. S12: Finishing the middle flange, clamping the valve body on the CNC vertical lathe, calibrating the position, processing the middle flange end face, inner hole and bottom hole, and the processing position reaches the preset surface roughness; S13: Mill the threaded bottom hole of the center flange, clamp the valve body to the gantry milling machine, calibrate the position, calibrate the center flange end face, inner hole and bottom hole position, and finish mill the threaded bottom hole; S14: Boring drainage holes, the universal angle milling head of the gantry milling machine is used to process drainage holes; S15: Three-coordinate detection, three-coordinate detection of the design size accuracy, shape accuracy and position accuracy of the valve body.

[0005] Furthermore, in step S2, the unilateral reserved machining allowance size range of the machining position is not less than 4.00 mm, and the form and position tolerance is not greater than 0.10 mm.

[0006] Furthermore, in step S4, the position calibration method is: aligning the center flange end face to be perpendicular to the main shaft; aligning the center of the center flange hole size to be coaxial with the main shaft center; aligning the horizontal axis of the center of the two end flanges to be in the same horizontal plane with the center line of the main shaft.

[0007] Furthermore, in step S5, the unilateral reserved machining allowance size range of the machining position is not less than 2.00 mm, and the form and position tolerance is not greater than 0.10 mm.

[0008] Furthermore, in step S10, the method for calibrating the position is: using the gantry milling spindle to install a dial indicator, fine-adjusting the jack to level the parallelism of the flange end face and the workbench to no more than 0.02 mm, and then fixing it; using the gantry milling spindle to install a dial indicator, marking the horizontal direction of the outer circle of the flange at both ends, and determining that the axis of the valve body flow channel is parallel to the X-axis of the workbench, and the parallelism is no more than 0.02 mm.

[0009] Furthermore, in step S10, the method for processing the middle flange datum is: milling the end face and inner hole of the middle flange until the surface is polished, with a single-side processing amount of no more than 0.50 mm, as a dial indicator calibration datum for finishing the middle flange part; the method for processing the datum of the two end flanges is: installing a four-axis angular milling head, and processing the end faces and outer circles of the two end flanges respectively to obtain a 5.00 mm wide and deep annular table, which is used as a dial indicator calibration datum for processing the various parts of the two end flanges.

[0010] Furthermore, in step S11, the valve seat holes at both ends are respectively finished, and the surface roughness is no greater than 0.20 μm.

[0011] Furthermore, the first cryogenic treatment in step S4 is to immerse the austenitic stainless steel in liquid nitrogen to cool it to -196° C. and keep it warm for 1 to 3 hours.

[0012] Furthermore, the non-destructive testing method in step S7 is: performing PT color flaw detection on all processed surfaces.

[0013] Furthermore, in step S15, the coaxiality tolerance of the final sealing ring installation position at both ends of the valve body is no more than 0.02mm, the surface roughness range is 0.1μm~0.2μm, and the position tolerance of the center coordinate point of the inner hole of the flange in the valve body and the center axis of the flow channel of the flange at both ends is 0.03mm.

[0014] The beneficial effects of the present invention are: The process goes through several processing stages, including rough machining, cryogenic treatment, semi-finishing, re-cryogenic treatment, milling finishing benchmark, and finishing stage. A robust processing method is proposed in the rough machining stage; it is verified that the blank has sufficient machining allowance; an initial machining benchmark is established, especially ensuring that the centers of the end flanges and the middle flange are in the same plane, and this plane is perpendicular to the middle flange; the surface tissue defect layer of the casting blank is eliminated; a certain amount of processing stress is released for subsequent cryogenic treatment; after the first cryogenic treatment, the martensitic transformation of the austenitic stainless steel is basically completed, and generally can meet the use requirements. However, ultra-low temperature working conditions have stricter requirements on sealing, especially for ultra-low temperature top-mounted ball valves that rely on medium pressure for sealing, so a second deep cryogenic treatment is added to the process to ensure the low-temperature stability of the installation position size of the sealing ring in the finished valve body; the setting of the semi-finishing stage is to retain a certain finishing allowance and to detect possible deep casting defects on the valve body processing surface in advance; the milling finishing datum stage uses the calibration datum required for the subsequent processing of the flange at both ends of the flange on the CNC gantry milling machine to ensure that the shape and position tolerances of the valve body meet the design requirements of the drawing; when using the dial indicator to calibrate the finishing end face datum and outer circle datum completed in the finishing process in the finishing stage, the indication error is controlled at ≤0.02mm, thereby ensuring that the shape and position tolerances of the valve body meet the design requirements of ≤0.025mm; ensuring that the final processing size and error meet the requirements of the design drawing. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a process flow chart of the present invention; Figure 2 This is a schematic diagram of the front view of the CNC vertical lathe clamping of the end flange of the present invention; Figure 3 This invention Figure 1 Schematic diagram of the middle AA section; Figure 4 This is a schematic diagram of the main view of the flange CNC vertical lathe clamping in the present invention; Figure 5 This is a left side schematic diagram of the flange CNC vertical lathe clamping in the present invention; Figure 6 It is a left side schematic diagram of the clamping of the CNC boring machine of the present invention; Figure 7 This is a top view schematic diagram of the clamping of the CNC boring machine of the present invention; Figure 8 This is a schematic diagram of the clamping main view of the gantry milling machine of the present invention; Figure 9 This is a schematic diagram of the left side view of the gantry milling machine clamping of the present invention; Figure 10 This is a schematic diagram of the valve body blank of the present invention; Figure 11 This is a schematic diagram of the valve body after processing of the present invention; Marked in the figure are, 1-valve body, 2-end flange, 3-middle flange, 4-first four claws, 5-first T-nut, 6-first adjustable support, 7-support plate, 8-first pressure plate, 9-first hexagonal nut, 10-back of middle flange, 12-first V-shaped iron, 13-second adjustable support, 14-second T-nut, 15-washer, 16-first jack, 17-first stud, 18-second hexagonal nut, 19-long pressure plate, 20-boring machine spindle, 22-third T-nut, 23-second stud, 24-second four claws, 26-second pressure plate, 27-steel pipe, 29-hexagonal bolt, 30-angle iron, 33-fourth T-nut, 34-third stud, 35-third hexagonal nut, 36-third pressure plate, 37-second jack, 38-second washers, 39-second V-shaped iron. DETAILED DESCRIPTION

[0016] The present invention will be further described below with reference to the accompanying drawings.

[0017] The embodiment of the present application provides a method for processing a top-mounted ball valve body, which is characterized by comprising the following steps: S1: Marking inspection, first clamp the valve body 1 blank on the CNC vertical lathe workbench, calibrate the clamping position of the valve body 1 blank by adjusting the clamping structure of the CNC vertical lathe workbench, use the lifting coordinate position of the CNC column tool rod, refer to the reference position of the valve body 1 blank, determine the machining allowances of the flanges 2 at both ends and other related positions, and mark them; specifically, Figure 1 As shown, either end flange 2 of the valve body 1 is seated on the CNC vertical lathe worktable. First, a four-jaw clamp is used to secure it. Four adjustable supports are installed between the CNC vertical lathe worktable and the end flange 2, pressing against the flange surface. Then, four sets of pressure plates and tie rods are installed on the back of the flange in the same position and tightened. The four-jaw, adjustable support, and pressure plate assemblies are adjusted one by one to calibrate the outer diameter and flow path dimensions of the end flange 2, as well as the neck dimensions, taking into account dimensional deviations and controlling the error within 2-3mm. The back of the end flange 2 is leveled to ensure parallelism, taking into account dimensional deviations and controlling the error within 2-3mm. Then, the four-jaw, adjustable support, and pressure plate assembly are tightened. Using the CNC column toolholder's lifting coordinate position, the vertical center position of the center flange 3 is determined by referring to the outer diameter and inner bore dimensions of the end face of the center flange 3. Using the outer diameter center position as a reference, sufficient machining allowance is determined vertically on the end and back faces of the end flanges 2, and marked. This is also done to confirm that sufficient machining allowance is present in other related dimensions and to mark them.

[0018] S2: Rough-turn the flanges 2 and flow channels at both ends, and use CNC vertical lathe to rough-turn the end face, outer circle, back face, flow channel and seat hole of the flange 2 at either end of the valve body 1 blank in turn, and then turn around to rough-turn the end face, outer circle, back face, flow channel and seat hole of the flange 2 at the other end of the valve body 1 blank; each processing position reaches the preset processing allowance and form and position tolerance; and the process requires that all dimensions to be processed have a single-side processing allowance ≥4mm, if the allowance is insufficient, it can be exposed to light; the form and position tolerance ≤0.10mm; first adjust the first four jaws 4 of the vertical lathe to the appropriate position according to the outer diameter size of the flanges 2 at both ends, and then hoist the end flange 2 of one end of the valve body 1 to sit on the step surface of the first four jaws 4, and properly tighten the first four jaws 4 to clamp the outer circle of the flange end. Install four first adjustable supports 6 on the bottom surface of the flange between two adjacent first four claws 4, install the first pressure plate 8 on the back side of the flange (above the first adjustable support 6), install the first T-nut 5 in the T-slot in the same direction of the workbench, pass the stud through the first pressure plate 8 and screw it into the T-slot, put on the first hexagonal nut 9 on the upper end of the stud and tighten it appropriately. The rough turning process requires marking and aligning the blank. The first four jaws (4), first adjustable support (6), and first hexagonal nut (9) are individually adjusted. The outer diameter and flow path dimensions of the two flanges (2) are rounded, as are the neck dimensions, taking into account dimensional deviations and limiting the error to within 2-3mm. The back faces (P) of the flanges (E and F) are leveled parallel to each other, taking into account dimensional deviations and limiting the error to within 2-3mm. The first four jaws (4), first adjustable support (6), and first hexagonal nut (9) are then tightened. Using the CNC column toolholder's vertical coordinate position, referencing the inner bore dimensions of the center flange (3), the end faces and back faces of the two flanges (2) are vertically verified to ensure sufficient machining allowances, with markings applied. Other relevant dimensions are also verified and marked. The flange end faces, outer diameter, and valve seat hole dimensions are then machined to meet the design drawing requirements. The other flange (2) is then machined using the same installation and precision check methods.

[0019] S3: Roughly bore the middle flange 3 datum and rough-turn the middle flange 3, clamp the valve body 1 on the CNC boring machine, and align the processing position of the middle flange 3 of the valve body 1 with reference to the valve body 1 datum position and process the datum; clamp the valve body 1 with the processed datum on the CNC vertical lathe, calibrate the position, and process the end face, inner hole and bottom hole of the middle flange 3; make each processing position reach the preset processing allowance and form and position tolerance; place two first V-shaped irons 12 of equal height on the workbench, and the center lines of the two first V-shaped irons 12 of equal height are as close to perpendicular as possible to the spindle 20 of the CNC boring machine; hoist the valve body 1, and place the flanges 2 at both ends of the valve body 1 in the V-grooves of the first V-shaped iron 12; install an adjustable support at the lower part of the outer circle of the middle flange 3; install the first washer 15 and the first jack 16 at the bottom of the valve body 1; the long pressure plate 19 passes through the flow channel of the valve body 1, and the two ends are supported by the first Connect and tighten the two T-nuts 14, the first stud 17, and the second hexagonal nut 18; adjust the position of the first V-shaped iron 12 of equal height until the horizontal distance from the outer circle of the flanges 2 at both ends to the end of the main shaft is equal, with an error of ≤0.10mm, to ensure that the center axis of the flow channel of the valve body 1 is perpendicular to the main shaft 20 of the boring machine; adjust the height of the adjustable support and the first jack 16 in the vertical direction until the distance from the uppermost and lowermost ends of the end face of the middle flange 3 to the end face of the main shaft is equal, with an error of ≤1.5mm, so as to ensure that the end face of the middle flange 3 is perpendicular to the main shaft, and then tighten the second hexagonal nut 18; move the workbench horizontally, and determine the horizontal center point coordinates of the valve body 1 according to the horizontal dimensions of the outer circle and inner hole of the middle flange 3; during rough processing, the dimensions of the end face and inner hole of the middle flange 3 meet the requirements of the design drawings, and rotate 180° to process the back of the middle flange 3 to see the light.

[0020] Then, place the back of the middle flange 3 on the vertical lathe workbench, clamp the outer circle of the back of the middle flange 3 with the second four jaws 24, and use the pull rod and the second pressure plate 26 at both ends of the flange to press the flow channel; install the homemade angle iron 30 tooling on both sides of the outer circle of the short side of the valve body 1 to tighten the outer circle of the flange; level the end face of the middle flange 3, calibrate the size of the inner hole of the end of the middle flange 3, and process the end face, inner hole and bottom of the middle flange 3, and the size meets the design requirements of the drawing. The specific operation steps are: first adjust the second four jaws 24 of the vertical lathe to the appropriate position according to the size of the outer diameter of the back side of the flange 3 in the blank, then hoist the back side of the flange 3 in the valve body 1 to the step surface of the second four jaws 24, properly tighten the second four jaws 24 to clamp the outer circle of the flange end, install the second pressure plate 26 at the two flange flow channel openings, place the third T-nut 22 in the T-slot corresponding to the direction of the second pressure plate 26 on the rotary table of the vertical lathe, and then screw in the four second studs 23, and then place the two steel pipes 27 on the second studs 23 at the outer end, and the second studs 23 pass through the steel pipe 2 7 and the corresponding through-holes on the second pressure plate 26, insert a hexagonal nut over the second stud 23; install the homemade angle iron 30 tooling on both sides of the outer circle of the short side of the valve body 1, and tighten it with T-slot bolts and hexagonal nuts; install a dial indicator on the column tool bar or tool table of the CNC vertical lathe, and adjust the second four jaws 24 to level the end face of the center flange 3 and calibrate the inner hole size; then tighten the two hexagonal nuts near the flange end to press the valve body 1, adjust the hexagonal bolts 29 to tighten the outer circle of the flange, and machine the end face, inner hole, and bottom hole of the center flange 3 to meet the rough machining design requirements of the center flange 3. The clamping and alignment methods for semi-finishing and rough machining are the same, and the machining dimensions are completed according to the semi-finishing design requirements.

[0021] The clamping and alignment methods for finishing and roughing are the same. However, after machining the end face, inner hole, and bottom hole of the intermediate flange 3, an electric telescopic finishing device needs to be installed on the column tool holder to finish the inner hole wall of the sealing ring installation position in the valve body 1 to meet the design requirement of a surface roughness value of less than 0.2μm.

[0022] S4: First cryogenic treatment: The valve body 1 undergoes the first cryogenic treatment. This treatment involves immersing the austenitic stainless steel in liquid nitrogen and cooling it to -196°C for 1-3 hours (depending on the valve body 1's wall thickness) to induce martensitic transformation. This effectively eliminates the problem of low-temperature deformation and ensures the structural and dimensional stability of the valve body 1 during subsequent processing. After this first cryogenic treatment, the martensitic transformation of the austenitic stainless steel is essentially complete, generally meeting service requirements.

[0023] S5: Semi-finish turning the flanges 2 and flow channels at both ends. Clamp the valve body 1 after the first cryogenic treatment onto a CNC vertical lathe. Semi-finish turning the end face, outer circle, back face, flow channel, and seat hole of the flange 2 at either end of the valve body 1 blank. Then, semi-finish turning the end face, outer circle, back face, flow channel, and seat hole of the flange 2 at the other end of the valve body 1. Each machining position reaches the preset machining allowance and form and position tolerances. The semi-finishing process of the flanges 2 at both ends is clamped in the same manner as the rough machining process, with slight differences in verification. The difference is that only the end runout of the end face of the flange 2 and the circular runout tolerance of the outer circle need to be verified using a dial indicator to ≤0.02mm. After tightening, re-verification is conducted. The semi-finishing process can then be carried out to meet the requirements of the design drawings.

[0024] S6: Semi-finish turning the center flange 3, clamp the valve body 1 on the CNC vertical lathe, calibrate the position, and then process the end face, inner hole and bottom hole of the center flange 3; the back of the center flange 3 is placed on the vertical lathe workbench. The specific clamping method and steps are the same as those for rough turning the center flange 3; level the end face of the center flange 3, calibrate the size of the inner hole of the center flange 3, and process the end face, inner hole and bottom hole of the center flange 3 so that the processing dimensions of the valve body 1 meet the requirements of the design drawings.

[0025] S7: Nondestructive testing (NDT) is performed on the machined parts of the valve. The semi-finishing process is to perform PT NDT while retaining a certain finishing allowance to detect possible deep casting defects on the machined surface of the valve body 1 in advance. This prevents the finished product from being scrapped due to defects that cannot be repaired.

[0026] S8: Rough milling of the threaded bottom hole of center flange 3. Clamp valve body 1 onto the gantry milling machine. After calibrating the position, calibrate the end face, inner hole, and bottom hole of center flange 3, and rough mill the threaded bottom hole. The added rough milling process of the threaded bottom hole of center flange 3 is to retain the smallest possible finishing allowance and reduce the machining deformation caused by thermal stress during the machining of austenitic stainless steel. Austenitic stainless steel often overheats and deforms during actual production and processing, affecting the accuracy of the machining dimensions.

[0027] S9: Second cryogenic treatment: The processed valve body 1 undergoes a second cryogenic treatment. After this initial cryogenic treatment, the martensitic transformation of the austenitic stainless steel is essentially complete, generally meeting service requirements. However, cryogenic operating conditions place stricter demands on sealing, especially for cryogenic top-entry ball valves that rely on medium pressure for sealing. Therefore, a second cryogenic treatment is added to ensure low-temperature stability of the sealing ring's installation position within the finished valve body 1.

[0028] Before finishing, use a dial indicator to check the finished end face datum and outer circle datum, and control the indication error to ≤0.02mm, so as to ensure that the shape and position tolerance of the valve body 1 meets the design requirement of ≤0.025mm.

[0029] S10: Mill the valve body 1 finishing datum, clamp the valve body 1 to the four-axis gantry milling machine, calibrate the position, and then process the valve body 1 processing datum; in order to utilize the equipment accuracy of the CNC gantry milling machine and the processing performance of the universal angle head, install, check, and align in one go, and process the calibration datum required for the subsequent processing of the two end flanges 2 and the middle flange 3 at one go, ensuring that the shape and position tolerance of the valve body 1 after completion is ≤0.025mm as the drawing design requirements, and fully meet the principle of complete unification of the design datum, process datum, and processing datum. Set a 5mm wide and deep annular table as the end face datum and outer circle datum of the two end flanges 2 to provide a calibration space position for the side head of the dial indicator.

[0030] S11: Finish the flanges 2 and flow channels at both ends, clamp the valve body 1 onto the CNC vertical lathe, calibrate the position, and then finish the end face, outer circle, back face, flow channel and seat hole of the flange 2 at either end of the valve body 1. Then turn around and finish the end face, outer circle, back face, flow channel and seat hole of the flange 2 at the other end of the valve body 1. Each processing position reaches the preset surface roughness. After the dimensions of the end faces, outer circles, back faces, flow channel holes and valve seat holes of the flanges 2 at both ends are finished to meet the requirements of the design drawings, an electric telescopic finishing device needs to be installed on the column tool table to finish the inner hole wall of the installation position of the sealing ring in the valve body 1 to meet the design requirement of a surface roughness value of ≤0.2μm.

[0031] S12: Finishing the middle flange 3, clamping the valve body 1 on the CNC vertical lathe, calibrating the position, and processing the end face, inner hole and bottom hole of the middle flange 3. The processing position reaches the preset surface roughness. Before the finishing process, use the dial indicator to check the finishing end face reference and outer circle reference, and control the indication error to ≤0.02mm, so as to ensure that the shape and position tolerance of the valve body 1 meet the design requirement of ≤0.025mm. The finishing requirement in the process is to use the high-end processing performance of the electric telescopic finishing equipment to improve the roughness value of the processed surface without affecting the dimensional tolerance of the valve body 1, so as to meet the surface roughness value of the inner wall of the installation position of the sealing ring in the finished valve body 1 ≤0.2μm, thereby ensuring the sealing performance between the valve body 1 and the valve seat support ring under ultra-low temperature conditions.

[0032] S13: Mill the threaded bottom hole of the center flange 3, clamp the valve body 1 to the gantry milling machine, calibrate the position, calibrate the end face, inner hole and bottom hole position of the center flange 3, and fine-mill the threaded bottom hole.

[0033] S14: Boring drainage holes, the universal angle milling head of the gantry milling machine is used to process drainage holes.

[0034] S15: Three-coordinate testing: Three-coordinate testing of the design dimensional accuracy, shape accuracy, and position accuracy of the valve body 1. This can verify the correctness of the process and that the dimensional tolerance and form and position tolerance of the product processing meet the requirements of the drawing.

[0035] In step S8, step S11, step S12 and step S13, the specific operations are: place two second V-shaped irons 39 of equal height on the CNC gantry milling workbench, with the central axes of the two second V-shaped irons 39 of equal height parallel to the X-axis direction of the CNC gantry milling workbench, hoist the valve body 1, and place the flanges 2 at both ends of the valve body 1 in the V-grooves of the second V-shaped irons 39; install the second washer 3815 and the second jack 37 on the back of the flanges on both sides of the short side of the middle flange 3; install pressure plates on the outer circular tops of the end flanges 2 at both ends; place four fourth T-nuts 33 in the T-slots of the workbench at corresponding positions; screw the four third studs 34 into the four fourth T-nuts 33 respectively, and pass them through the through holes of the pressure plate, and then screw the four third hexagonal nuts 35 into the upper parts of the third studs 34 respectively. Adjust the position of the second V-shaped iron 39 at equal height until the horizontal direction connecting the outer circles of the two end flanges 2 at equal height is parallel to the X-axis movement direction of the CNC gantry milling worktable, with a parallelism error of ≤0.10mm, to ensure that the center axis of the flow channel of the valve body 1 is consistent with the X-axis movement direction; install a dial indicator on the spindle column, adjust the second jacks 37 on both sides until the end face of the middle flange 3 is parallel to the CNC gantry milling worktable, with a parallelism error of ≤0.05mm, and then tighten the third hexagonal nut 35, use a dial indicator or spindle to install an edge finder, determine the center coordinate of the inner hole of the middle flange 3, and complete the rough machining, fine machining and thread milling processes; determine the center coordinate of the inner hole size in the same way to complete the finishing processes of the middle flange 3 and the two end flanges 2. By utilizing the processing precision of CNC gantry milling equipment, the valve body 1 is installed, checked, and aligned in one go, and the calibration datum required for the subsequent processing of the flanges 2 at both ends and the middle flange 3 is processed at one time, ensuring that the shape and position tolerance of the valve body 1 is ≤0.025mm as required by the drawing design, and fully meeting the principle of complete unification of design datum, process datum, and processing datum.

[0036] In summary, the present invention proposes a method for machining a top-mounted ball valve body, comprising seven steps: rough machining, cryogenic treatment, semi-finishing, further cryogenic treatment, milling of the finishing datum, finishing, and three-dimensional coordinate inspection. CNC vertical lathe machining is employed, with initial clamping followed by adjustment and verification of the valve body 1's position. After tightening the valve body 1, the datum is checked and verified before machining begins. The goal is to ensure that the dimensional and form tolerances of the flanges 2 after machining meet the design requirements of the rough machining drawing. The holding time is appropriately extended based on the wall thickness of the valve body 1 to ensure a thorough martensitic transformation, thereby ensuring the structural and dimensional stability of the valve body 1 material during subsequent machining. The semi-finishing step allows for PT non-destructive testing (NDT) while retaining a certain finishing allowance, thereby detecting potential deep casting defects on the machined surface of the valve body 1 in advance. This prevents the finished product from being scrapped due to defects that cannot be repaired. The additional step of rough milling the threaded bottom hole of the middle flange 3 is intended to minimize finishing allowance and reduce machining deformation caused by thermal stress in austenitic stainless steel during machining. Because austenitic stainless steel often overheats and deforms during actual production, affecting dimensional accuracy, the fourth step involves cryogenic treatment: After this initial cryogenic treatment, the martensitic transformation of the austenitic stainless steel is essentially complete, generally meeting service requirements. However, cryogenic conditions place stringent sealing requirements, particularly for cryogenic top-entry ball valves that rely on medium pressure for sealing. Therefore, a second cryogenic treatment is added to ensure low-temperature stability of the sealing ring's installed position and dimensions within the finished valve body 1. To leverage the precision of the CNC gantry milling center and the processing capabilities of the universal angle head, installation, calibration, and alignment are performed in one go. The calibration datums required for subsequent machining of the end flanges 2 and the center flange 3 are also machined in one go. This ensures that the finished valve body 1 meets the design drawing design requirements for shape and position tolerances of ≤0.025mm, fully complying with the principle of complete uniformity of design, process, and machining datums. Before finishing, a dial indicator is used to calibrate the end face and outer diameter datums, maintaining an indication error of 0.02mm or less. This ensures that the shape and position tolerances of the valve body 1 meet the design requirement of 0.025mm or less. The finishing requirement during this process is to utilize high-end machining capabilities to improve the roughness of the machined surface without affecting the dimensional tolerances of the valve body 1, ensuring a surface roughness of 0.2μm or less on the inner wall where the sealing ring is installed in the finished valve body 1. This ensures sealing performance between the valve body 1 and the valve seat support ring even at ultra-low temperatures. Finally, the correctness of the process is verified, and the dimensional and geometric tolerances of the product meet the drawing requirements.

Claims

1. The processing method of the top-mounted ball valve body is characterized in that: The following steps are included: S1: Marking inspection: first clamp the valve body (1) blank on the CNC vertical lathe workbench, calibrate the clamping position of the valve body (1) blank by adjusting the clamping structure of the CNC vertical lathe workbench, use the lifting coordinate position of the CNC column tool rod, refer to the reference position of the valve body (1) blank, determine the machining allowances of the flanges (2) at both ends and other related positions, and mark them; S2: Rough turning the flanges (2) and flow channels at both ends, sequentially rough turning the end face, outer circle, back face, flow channel and seat hole of the flange (2) at one end of the valve body (1) blank by CNC vertical turning, and then rough turning the end face, outer circle, back face, flow channel and seat hole of the flange (2) at the other end of the valve body (1) blank by turning around; each processing position reaches the preset processing allowance and form and position tolerance; S3: Rough boring of the middle flange (3) datum and rough turning of the middle flange (3), clamping the valve body (1) on a CNC boring machine, aligning the processing position of the middle flange (3) of the valve body (1) with reference to the datum position of the valve body (1) and processing the datum; clamping the valve body (1) with the processed datum on a CNC vertical lathe, calibrating the position, and processing the end face, inner hole and bottom hole of the middle flange (3); making each processing position reach the preset processing allowance and form and position tolerance; S4: First cryogenic treatment, performing the first cryogenic treatment on the valve body (1); S5: semi-finish turning the flanges (2) and flow channels at both ends, clamping the valve body (1) after the first cryogenic treatment on a CNC vertical lathe, semi-finish turning the end face, outer circle, back face, flow channel and seat hole of the flange (2) at either end of the valve body (1) blank, and then semi-finish turning the end face, outer circle, back face, flow channel and seat hole of the flange (2) at the other end of the valve body (1); each processing position reaches the preset processing allowance and form and position tolerance; S6: Semi-finish turning the center flange (3), clamping the valve body (1) on the CNC vertical lathe, calibrating the position, and then machining the end face, inner hole and bottom hole of the center flange (3); S7: Non-destructive testing, non-destructive testing of the processing parts of the valve; S8: Rough milling of the threaded bottom hole of the middle flange, clamping the valve body (1) to the gantry milling machine, calibrating the position, calibrating the end face, inner hole and bottom hole position of the middle flange (3), and rough milling of the threaded bottom hole; S9: a second cryogenic treatment, wherein the processed valve body (1) is subjected to a second cryogenic treatment; S10: Milling the valve body for fine machining, clamping the valve body (1) to the four-axis gantry milling machine, calibrating the position, and machining the valve body (1) for machining; S11: Finish the flanges and flow channels at both ends, clamp the valve body (1) on a CNC vertical lathe, calibrate the position, and then finish the end face, outer circle, back face, flow channel and seat hole of the flange (2) at either end of the valve body (1). Then, turn around and finish the end face, outer circle, back face, flow channel and seat hole of the flange (2) at the other end of the valve body (1); each processing position reaches the preset surface roughness; S12: Finishing the middle flange, clamping the valve body (1) on a CNC vertical lathe, calibrating the position, and processing the end face, inner hole and bottom hole of the middle flange (3), so that the processing position reaches the preset surface roughness; S13: Milling the threaded bottom hole of the center flange, clamping the valve body (1) to the gantry milling machine, calibrating the position, calibrating the end face, inner hole and bottom hole position of the center flange (3), and fine milling the threaded bottom hole; S14: Boring drainage holes, the universal angle milling head of the gantry milling machine is used to process drainage holes; S15: Three-coordinate detection, three-coordinate detection of the design size accuracy, shape accuracy and position accuracy of the valve body (1).

2. The method for processing a top-mounted ball valve body according to claim 1, characterized in that: In step S2, the unilateral reserved machining allowance size range of the machining position is not less than 4.00 mm, and the form and position tolerance is not greater than 0.10 mm.

3. The method for processing a top-mounted ball valve body according to claim 1, characterized in that: In step S4, the position calibration method is as follows: aligning the end face of the center flange (3) to be perpendicular to the main shaft; aligning the center of the hole size of the center flange (3) to be coaxial with the center of the main shaft; aligning the horizontal axis of the center of the two end flanges (2) to be in the same horizontal plane with the center line of the main shaft.

4. The method for processing a top-mounted ball valve body according to claim 1, characterized in that: In step S5, the unilateral reserved machining allowance size range of the machining position is not less than 2.00 mm, and the form and position tolerance is not greater than 0.10 mm.

5. The method for processing a top-mounted ball valve body according to claim 1, characterized in that: In step S10, the method for calibrating the position is: using the gantry milling spindle to install a dial indicator, fine-adjusting the jack to level the end face of the middle flange (3) to the workbench to ensure that the parallelism is not greater than 0.02 mm, and then fixing it; using the gantry milling spindle to install a dial indicator, marking the horizontal direction of the outer circle of the flanges (2) at both ends, and confirming that the flow channel axis of the valve body (1) is parallel to the X-axis of the workbench, and the parallelism is not greater than 0.02 mm.

6. The method for processing a top-mounted ball valve body according to claim 1, characterized in that: In step S10, the method for machining the middle flange (3) is: milling the end face and inner hole of the middle flange (3) until the surface is polished, with a single-side machining amount of no more than 0.50 mm, as a dial indicator calibration reference for fine machining of the middle flange (3); the method for machining the end flanges (2) is: installing a four-axis angular milling head, machining the end faces and outer circles of the end flanges (2) respectively, and obtaining a 5.00 mm wide and deep annular table, as a dial indicator calibration reference for machining various parts of the end flanges (2).

7. The method for processing a top-mounted ball valve body according to claim 1, characterized in that: In step S11 , the valve seat holes at both ends are respectively finished, and the surface roughness is no greater than 0.20 μm.

8. The method for processing a top-mounted ball valve body according to claim 1, characterized in that: The first cryogenic treatment in step S4 is to immerse the austenitic stainless steel in liquid nitrogen to cool it to -196°C and keep it at this temperature for 1 to 3 hours.

9. The method for processing a top-mounted ball valve body according to claim 1, characterized in that: The non-destructive testing method in step S7 is: performing PT color flaw detection on all processed surfaces.

10. The method for processing a top-mounted ball valve body according to claim 1, characterized in that: In step S15, the coaxiality tolerance of the final installation position of the sealing rings at both ends of the valve body (1) is no more than 0.02mm, the surface roughness range is 0.1μm to 0.2μm, and the position tolerance of the center coordinate point of the inner hole of the flange (3) in the valve body (1) and the center axis of the flow channel of the flanges (2) at both ends is 0.03mm.

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