A method for local machining and removal of hyperboloid deep weld defects

Abstract

The application discloses a kind of hyperboloid depth weld defect local processing removal method, first by weld defect position in the outer surface of workpiece draw out the horizontal and circumferential center line of to-be-welded groove, surface processing boundary reference line, then clamping alignment workpiece, first using row drill method to process arc-shaped groove, then using milling to process the slope of both sides of arc-shaped groove and remove twist drill left sharp corner, and grind the bottom of arc-shaped groove, then using layered processing in depth direction and layered visual inspection to the bottom of arc-shaped groove are carried out to check defect display, until clean, process arc-shaped groove into to-be-welded groove, then process the ladder slope of both ends of to-be-welded groove, finally grind each surface of to-be-welded groove, complete the local processing removal of weld defect, the method can remove the whole weld defect clean, high removal efficiency, while to-be-welded groove structure is simple, and the difficulty of machining is small.

Description

Technical Field

[0001] This invention belongs to the field of pressure vessel manufacturing technology, and specifically relates to a method for local processing and removal of defects in hyperboloid deep welds. Background Technology

[0002] Pressure vessels are key equipment in modern chemical process systems, widely used in petrochemicals, energy, military, and scientific research, and are core equipment that the country encourages to produce domestically. This type of equipment often operates in harsh environments such as high temperature, high pressure, low temperature, and corrosion. The quality of a single unit directly affects not only the safe operation of the entire process line but also the safety of the surrounding ecological environment and the lives and property of the people. Furthermore, with my country's "dual carbon" goals and the continuous improvement of its equipment manufacturing capabilities, higher requirements are being placed on the manufacturing capabilities and quality of pressure vessels.

[0003] A key piece of equipment in the reactor coolant system of a nuclear power plant is a vertical cylindrical high-temperature and high-pressure vessel manufactured by welding low-alloy steel forgings. Because the quality of its welds is crucial to the normal operation of the entire reactor process system, all main pressure-bearing welds must undergo non-destructive testing (VT, MT, RT, and UT) according to relevant standards and meet Level 1 requirements.

[0004] When a hyperboloid deep weld defect is detected, for example: after an embedded valve nozzle assembly is welded to a thick-walled spherical head and ground to the specifications in the drawings, non-destructive testing (NDT) is performed. The VT, MT, and RT results all meet the technical requirements and no recordable defects are found. However, the UT result reveals an unacceptable non-volume defect signal. This defect is 25mm long along the weld circumference, laterally close to the weld bevel of the spherical head, and 85.3mm deep from the outer surface. According to the procedure, this welding defect needs to be repaired, but the following technical difficulties exist:

[0005] (1) One of the key aspects of welding defect repair is ensuring the complete removal of the defect. However, since the welding defect between the valve nozzle assembly and the spherical head weld is a non-volume defect discovered by radiographic testing (UT), and no defect was found after multiple radiographic re-examinations at different angles, it is impossible to verify whether the defect has been completely removed by radiographic testing (RT) after trenching. Moreover, once trenching is completed, UT cannot verify whether the defect has been completely removed due to multi-interface reflection. If repair welding is carried out before the defect has been completely removed, it will inevitably lead to secondary or even multiple weld repairs. Therefore, the key to this welding defect repair is to successfully find and completely remove the defect during the defect removal process.

[0006] (2) The weld defect found during inspection was 85.3 mm deep from the outer surface of the weld. Although it was relatively shallow from the inner surface of the weld, the UT method could not accurately determine the location of the weld defect from the inner surface due to the influence of the inner wall weld overlay, which increased the difficulty of defect removal. At the same time, after removing and repairing from the inside, it was necessary to re-overlay the inner wall in a local area, which increased the number of procedures. Therefore, the depth of defect removal and repair welding was large. In addition, the defect was located in the weld between the valve nozzle assembly and the spherical head of the hyperboloid structure. Moreover, it was not technically permissible to use hot working methods such as carbon arc gouging to remove it. If conventional angle grinder grinding method was used to remove the hyperboloid weld defect, it would not only be inefficient but would also remove too much base material. Especially when the defect was deep, it would cause the repair weld to deviate significantly from the original weld area, affecting the in-service inspection of the equipment weld. Therefore, it is necessary to develop a machining method that can remove deep hyperboloid weld defects.

[0007] (3) The weld defect discovered during inspection is located near the bevel of the spherical head in the transverse direction of the weld and has a relatively large depth. At the same time, it is technically not permissible to excessively enlarge the weld width. In order to avoid the formation of a deep, narrow, and short groove to be repaired after the defect is removed, which would affect subsequent repair welding operations, the groove to be repaired should be an arc-shaped structure centered on the transverse and circumferential directions of the defect. Its bottom should have a width suitable for double-pass welding and a length suitable for staggered arc start and end. The two sides and two ends must have appropriate slopes and transition smoothly with the bottom using a rounded arc. The structure of this groove to be repaired is relatively complex and difficult to machine.

[0008] (4) Due to the complex structure and dimensions of the groove to be repaired, the machined area needs to be ground to eliminate non-smooth or partially non-compliant structures such as sharp corners and edges. At the same time, to avoid welding defects such as slag inclusions and incomplete fusion in the repair weld, each layer or each weld seam needs to be locally ground during the repair welding process. Therefore, it is necessary to develop a special depth grinding tool that is flexible in operation, can reach a certain depth, and has a customizable grinding head.

[0009] To overcome the aforementioned technical challenges, it is necessary to develop "a local processing and removal method for hyperboloid deep weld defects" based on the company's existing processing resources to ensure that hyperboloid deep weld defects can be successfully located and completely removed, while processing the defect removal area into a groove to be repaired that meets the requirements of the repair welding operation. Summary of the Invention

[0010] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for local processing and removal of defects in hyperboloid deep welds.

[0011] This invention mainly solves the problem of local processing and removal of deep weld defects on hyperboloids. It enables the successful location and complete removal of weld defects during the processing, and finally forms a groove to be repaired that meets the requirements of the repair welding operation, so as to ensure that deep weld defects on hyperboloids can be repaired successfully in one go.

[0012] To solve the technical problem, the technical solution of the present invention is: a method for local processing and removal of defects in hyperboloid deep welds, comprising the following steps:

[0013] Step 1: Mark the location of the weld defect on the workpiece, and draw the transverse and circumferential center lines of the groove to be repaired on the outer surface of the workpiece, as well as the surface processing boundary reference line. The groove to be repaired is a "U" shaped deep groove.

[0014] Step 2: Workpiece clamping and alignment;

[0015] Step 3: Use a multi-drill method to process the arc-shaped groove. The arc length and width of the arc-shaped groove are the same as the arc length and width of the bottom of the groove to be repaired. The arc length and width of the bottom of the groove to be repaired are greater than the arc length and width of the weld defect. The processing depth of the arc-shaped groove is 8~10mm above the depth of the weld defect.

[0016] Step 4: Mill the slope of both sides of the arc-shaped groove and remove any remaining sharp corners, while grinding the bottom of the arc-shaped groove 7;

[0017] Step 5: Use layered processing in the depth direction and layered visual inspection and liquid penetration to check the defects at the bottom of the arc-shaped groove until the weld defects are completely removed, and process the arc-shaped groove into a groove to be repaired.

[0018] Step 6: Machin the stepped slope at both ends of the groove to be repaired;

[0019] Step 7: Grind all surfaces of the groove to be repaired and perform visual and liquid penetration inspections on all surfaces of the groove to be repaired;

[0020] Step 8: Perform repair welding and non-destructive testing on the groove to be repaired.

[0021] Preferably, step 1 specifically involves: the bottom arc length of the groove to be repaired is the arc length of the weld defect plus a repair welding operation distance of 15~25mm at each end, the bottom width is the operation distance of double welding, and the slopes at both ends and sides of the groove to be repaired are 10~15° respectively; the transverse and circumferential center lines and surface processing boundary reference lines of the groove to be repaired are determined based on the bottom arc length, width, and slopes at both ends and sides of the groove.

[0022] Preferably, the bottom arc length of the groove to be repaired is the arc length of the weld defect plus a repair welding operation distance of 20mm at each end, and the slopes of the two ends and both sides of the groove to be repaired are 12°.

[0023] Preferably, step 2 specifically involves: clamping and aligning the workpiece, and using the rotation of the machine tool coordinate axes to make the center of the machine tool spindle coincide with the center of the valve connector assembly of the workpiece.

[0024] Preferably, step 3 specifically involves: using a boring and milling composite machine with a Φ16mm standard high-speed steel twist drill bit, and using a drilling method to drill arc-shaped grooves at both ends along the transverse centerline of the groove to be repaired and along the circumferential centerline at intervals less than 3 / 4 of the drill bit diameter, until the bottom arc length of the arc-shaped groove meets the specified bottom arc length dimension of the groove to be repaired.

[0025] Preferably, step 4 specifically involves: using a boring and milling machine with a Φ42mm stepped twist drill bit to mill the bottom of the arc-shaped groove, sequentially completing the machining of the slopes on both sides of the arc-shaped groove and the sharp corners left by the Φ16mm standard high-speed steel twist drill bit, and then using an electric straight grinder with an extended carbide rotary file to grind the bottom of the arc-shaped groove and perform visual inspection and PT.

[0026] Preferably, step 5 specifically involves: while maintaining the arc length at the bottom of the arc-shaped groove, repeating steps 3 and 4 in layers with a processing amount of 1 mm in the depth direction each time, until visual inspection or PT reveals weld defects; then, while maintaining the arc length at the bottom of the arc-shaped groove, repeating steps 3 and 4 in layers with a processing amount of 2 mm in the depth direction each time, until visual inspection and PT confirm that the weld defects have been completely removed, thus processing the arc-shaped groove into a groove to be repaired.

[0027] Preferably, step 6 specifically involves: using a boring and milling machine with a Φ16mm standard high-speed steel twist drill bit, machining the stepped slope of both ends of the groove to be repaired along the circumferential centerline according to the step ratio of tanβ, and then using a boring and milling machine with a Φ42mm stepped twist drill bit to mill the stepped slope of both ends into a slope surface; the calculation formula for the step is: when the slope of both ends of the groove to be repaired is β, the step ratio is equal to tanβ.

[0028] Preferably, step 7 specifically involves: using an electric straight grinder with a clamped extended carbide rotary file to locally grind the surface of the groove 6 to be repaired so that it meets the shape and size requirements of the groove to be repaired.

[0029] Preferably, step 8 specifically involves: performing a weld repair on the groove to be repaired, and conducting a non-destructive inspection on the repaired weld according to the original weld requirements, thereby completing the repair of the hyperboloid depth weld defect between the valve nozzle assembly and the spherical head of the workpiece.

[0030] Compared with the prior art, the advantages of the present invention are as follows:

[0031] (1) This invention discloses a method for local processing and removal of deep weld defects on hyperboloids. First, the center lines of the groove to be repaired and the reference lines of the surface processing boundary are drawn on the outer surface of the workpiece according to the location of the weld defect. Then, the workpiece is clamped and aligned. First, the arc groove is processed by drilling. Then, the slope of the two sides of the arc groove is processed by milling and the sharp corners left by the twist drill are removed. Then, the bottom of the arc groove is ground. Then, the layered processing in the depth direction and the layered visual inspection or PT are used to check the defect display at the bottom of the arc groove until it is clean. The arc groove is processed into a groove to be repaired. Then, the stepped slope at both ends of the groove to be repaired is processed. Finally, the surfaces of the groove to be repaired are ground to complete the local processing and removal of weld defects. The method of this invention can clean the weld defects completely and has high removal efficiency. The groove to be repaired has a simple structure and is easy to machine.

[0032] (2) The boring and milling composite machine clamping Φ16mm standard high-speed steel twist drill bit of the present invention can realize the machining of arc grooves on hyperboloids by using the drilling method; the boring and milling composite machine clamping Φ42mm stepped twist drill bit of the present invention can complete the machining of the slope of both sides of the arc groove and the sharp corner left by the twist drill in one go by using the milling method;

[0033] (3) The present invention performs layered processing in the depth direction and combines layered visual inspection with liquid penetration inspection to check the display of defects at the bottom of the arc groove, which can successfully find weld defects and remove them cleanly, ensuring that the defects are completely removed at one time and improving the removal efficiency;

[0034] (4) The groove processed at the beginning of this invention is an arc-shaped groove. The groove after the defect is removed is a groove to be repaired. First, the arc-shaped groove is processed by a drilling method. The arc length and width of the arc-shaped groove are the same as the arc length and width of the bottom of the groove to be repaired. The processing depth of the arc-shaped groove is 8~10mm above the depth of the weld defect. Then, layered processing and layered visual processing are used in the depth direction. While removing the weld defect, fine adjustments are made according to the actual position of the weld defect, which can greatly improve the integrity of the weld defect removal.

[0035] The present invention uses a stepped drilling method with Φ16mm standard high-speed steel twist drill bits on both ends of the arc-shaped groove, which can improve the efficiency of milling the slope at both ends of the groove with stepped twist drill bits; the electric straight grinder used in the present invention is equipped with a custom-made extended carbide rotary file that can meet the grinding requirements of each surface of the groove to be repaired and welded on the hyperboloid and during the repair welding process. Attached Figure Description

[0036] Figure 1 A flowchart of a method for localized machining and removal of defects in hyperboloid deep welds according to the present invention;

[0037] Figure 2 A schematic diagram of the structure of the workpiece of the present invention;

[0038] Figure 3 A schematic diagram of the main cross-sectional structure of the groove to be repaired in this invention;

[0039] Figure 4 A top view of a partial structural diagram of the groove to be repaired in this invention.

[0040] Explanation of reference numerals in the attached figures:

[0041] 1. Spherical head; 2. Valve nozzle assembly; 3. Weld between valve nozzle assembly and spherical head; 4. Stainless steel overlay on inner wall; 5. Weld defect; 6. Groove to be repaired; 7. Arc-shaped groove.

[0042] 1-1 Boundary of the spherical head; 2-1 Boundary of the valve nozzle assembly;

[0043] 6-1. Circumferential center line of the groove to be repaired; 6-2. Transverse center line of the groove to be repaired; 6-3. Surface processing boundary reference line. Detailed Implementation

[0044] The specific implementation of the present invention is described below with reference to embodiments:

[0045] It should be noted that the structures, proportions, sizes, etc. shown in this specification are only used to complement the content disclosed in the specification for those skilled in the art to understand and read, and are not intended to limit the conditions under which the present invention can be implemented. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0046] The boring and milling composite machine tool, as a composite machining equipment suitable for milling, drilling, tapping and other machining operations on the end face and side of the workpiece, has the advantages of high machining accuracy, high machining efficiency, simple workpiece clamping and wide applicability; while the portable electric straight grinder, as a manual grinding tool, has the advantages of flexible operation, excellent machining accessibility and customizable grinding heads. Therefore, the combination method of using a boring and milling composite machine with a drilling machine and a portable electric straight grinder for grinding is selected to locally remove deep weld defects on hyperboloid surfaces.

[0047] Example 1

[0048] like Figure 1 As shown, this invention discloses a method for localized processing and removal of defects in hyperboloid deep welds, comprising the following steps:

[0049] Step 1: Mark the location of weld defect 5 on the workpiece, and draw the transverse and circumferential center lines of the groove 6 to be repaired on the outer surface of the workpiece, as well as the surface processing boundary reference line. The groove 6 to be repaired is a "U" shaped deep groove.

[0050] Step 2: Workpiece clamping and alignment;

[0051] Step 3: Use a multi-drill method to process the arc-shaped groove 7. The arc length and width of the arc-shaped groove 7 are the same as the arc length and width of the bottom of the groove 6 to be repaired. The arc length and width of the bottom of the groove 6 to be repaired are greater than the arc length and width of the weld defect 5. The processing depth of the arc-shaped groove 7 is 8~10mm above the depth of the weld defect 5.

[0052] Step 4: Mill the slope of both sides of the arc-shaped groove 7 and remove any remaining sharp corners, and at the same time grind the bottom of the arc-shaped groove 7;

[0053] Step 5: Use layered processing in the depth direction and layered visual inspection and liquid penetration to check the bottom defects of the arc groove 7 until the weld defect 5 is completely removed, and process the arc groove 7 into a groove 6 to be repaired.

[0054] Step 6: Machin the stepped slope at both ends of the groove 6 to be repaired;

[0055] Step 7: Grind all surfaces of the groove 6 to be repaired and perform visual and liquid penetration inspection on all surfaces of the groove 6 to be repaired.

[0056] Step 8: Perform welding and non-destructive testing on the groove 6 to be repaired.

[0057] Example 2

[0058] like Figure 4 As shown, preferably, step 1 specifically involves: the bottom arc length of the groove 6 to be repaired is the arc length of the weld defect 5 plus a repair welding operation distance of 15~25mm at each end; the bottom width is the operation distance of double welding; and the slopes at both ends and sides of the groove 6 to be repaired are 10~15° respectively. The transverse and circumferential center lines and surface processing boundary reference lines of the groove 6 to be repaired are determined based on the bottom arc length, width, and slopes at both ends and sides of the groove 6 to be repaired.

[0059] Preferably, the bottom arc length of the groove 6 to be repaired is the arc length of the weld defect 5 plus the repair welding operation distance of 20mm at each end, and the slopes of the two ends and both sides of the groove 6 to be repaired are 12°.

[0060] The surface arc length after the weld defect 5 is removed is determined by comprehensively considering the root arc length, bottom fillet, slope of both ends, and diameter of the center circle of weld defect 5.

[0061] like Figure 2 , 3 As shown, the pressure vessel workpiece includes a spherical head, a valve nozzle assembly 2, a weld 3 between the valve nozzle assembly and the spherical head, and a stainless steel overlay layer 4 on the inner wall. The weld defect 5 is a defect in the weld formed when the valve nozzle assembly 2 is welded to the spherical head 1.

[0062] Example 3

[0063] Preferably, step 2 specifically involves: clamping and aligning the workpiece, and using the rotation of the machine tool coordinate axes to make the center of the machine tool spindle coincide with the center of the valve connector assembly 2 of the workpiece.

[0064] Preferably, step 3 specifically involves: using a boring and milling composite machine with a Φ16mm standard high-speed steel twist drill bit, and using a drilling method to drill arc-shaped grooves 7 at both ends along the transverse centerline of the groove 6 to be repaired and along the circumferential centerline at intervals less than 3 / 4 of the drill bit diameter, until the bottom arc length of the arc-shaped groove 7 meets the specified bottom arc length dimension of the groove 6 to be repaired.

[0065] Example 4

[0066] Preferably, step 4 specifically involves: using a boring and milling machine with a Φ42mm stepped twist drill bit to mill the bottom of the arc-shaped groove 7, sequentially completing the machining of the slope of both sides of the arc-shaped groove 7 and the sharp corner left by the Φ16mm standard high-speed steel twist drill bit, and then using an electric straight grinder with an extended carbide rotary file to grind the bottom of the arc-shaped groove 7 and perform visual inspection and PT.

[0067] Preferably, step 5 specifically involves: while maintaining the bottom arc length of the arc-shaped groove 7, repeating steps 3 and 4 in layers with a processing amount of 1mm in the depth direction each time, until visual inspection or PT reveals weld defect 5; then, while maintaining the bottom arc length of the arc-shaped groove 7, repeating steps 3 and 4 in layers with a processing amount of 2mm in the depth direction each time, until visual inspection and PT confirm that weld defect 5 has been completely removed, thus processing the arc-shaped groove 7 into a groove 6 to be repaired.

[0068] Example 5

[0069] Preferably, step 6 specifically involves: using a boring and milling machine with a Φ16mm standard high-speed steel twist drill bit, machining the stepped slope of both ends of the groove 6 to be repaired along the circumferential centerline according to the step ratio of tanβ; and then using a boring and milling machine with a Φ42mm stepped twist drill bit to mill the stepped slope of both ends into a slope surface; the calculation formula for the step is: when the slope of both ends of the groove 6 to be repaired is β, the step ratio is equal to tanβ.

[0070] Preferably, step 7 specifically involves: using an electric straight grinder with a clamped extended carbide rotary file to locally grind the surface of the groove 6 to be repaired so that it meets the shape and size requirements of the groove 6 to be repaired.

[0071] Preferably, step 8 specifically involves: performing a weld repair on the groove 6 to be repaired, and conducting a non-destructive inspection on the repaired weld according to the original weld requirements, thereby completing the repair of the hyperboloid depth weld defect between the valve nozzle assembly and the spherical head of the workpiece.

[0072] Example 6

[0073] (1) such as Figure 3 As shown, mark the location of weld defect 5 on the workpiece, and draw the transverse and circumferential center lines of the groove 6 to be repaired, as well as the surface machining boundary reference line; the depth of weld defect 5 is 85.3 mm;

[0074] like Figure 4 As shown, on the workpiece surface corresponding to weld defect 5, mark the circumferential center line 6-1 of the groove to be repaired, the transverse center line 6-2 of the groove to be repaired, and the surface processing boundary reference line 6-3. Among them, the spherical head boundary 1-1 is the side boundary of the spherical head 1 near the valve nozzle assembly 2, and the valve nozzle assembly boundary 2-1 is the side boundary of the valve nozzle assembly 2 near the spherical head 1.

[0075] (2) The workpiece is clamped and aligned, and the rotation of the machine tool coordinate axis is used to make the center of the machine tool spindle coincide with the center of the valve connector assembly 2;

[0076] (3) Using a boring and milling composite machine with a Φ16mm standard high-speed steel twist drill bit, a drilling method is used to drill 76mm deep holes at both ends along the transverse center line of the groove 6 to be repaired and along the circumferential center line at intervals of less than 12mm (3 / 4 of the drill bit diameter) until the bottom arc length of the arc groove 7 meets the specified dimensions.

[0077] like Figure 4 As shown, the arc length of the weld defect is less than the arc length of the bottom of the arc groove 7, and the width of the weld defect is less than the width of the bottom of the arc groove 7. After the defect is removed, the arc length at the root is the arc length of the bottom of the arc groove 7, and the arc length of the surface after the defect is removed is the arc length of the groove 6 to be repaired.

[0078] (4) The bottom of the 76mm hole is machined by using a boring and milling composite machine with a Φ42mm stepped twist drill bit. The slope of both sides of the arc groove 7 and the sharp corner left by the twist drill are processed in one go, so as to facilitate visual inspection and PT of the bottom of the arc groove 7;

[0079] The bottom of the arc-shaped groove 7 was ground using a portable electric straight grinder with a custom-made extended carbide rotary file, and then visually inspected and tested using a physical test (PT) to observe the defect display.

[0080] (5) Repeat steps (3) and (4) in layers with a machining amount of 1mm in each depth direction (always maintaining the arc length of the bottom of the arc groove 7) until visual inspection or PT finds the defect; then repeat steps (3) and (4) in layers with a machining amount of 2mm in each depth direction (always maintaining the arc length of the bottom of the arc groove 7) until visual inspection and PT confirm that the weld defect 5 has been removed, and process the arc groove 7 into a groove 6 to be repaired, such as Figure 4 As shown, the arc length of the defect removal surface is the same as the arc length of the groove to be repaired by welding.

[0081] (6) Using a boring and milling composite machine with a Φ16mm standard high-speed steel twist drill bit, the stepped slope of both ends is machined along the circumferential center line of the groove in a step of about 1×5mm. Then, using a boring and milling composite machine with a Φ42mm stepped twist drill bit, the stepped slope of both ends is milled into a slope surface.

[0082] Step calculation method: The slope of both ends of the groove 6 to be repaired is β, and the step ratio is approximately equal to tanβ. When β=12°, the step ratio is tan(12°). Therefore, a step of 1×5mm is selected. At this time, the processing efficiency is relatively high and no pit will be formed.

[0083] (7) Use a portable electric straight grinder to mount a custom-made extended carbide rotary file to locally grind the surface of the groove 6 to be repaired so that it meets the shape and size requirements of the groove 6 to be repaired;

[0084] (8) Weld the groove 6 to be repaired according to the welding process requirements, and conduct non-destructive testing on the weld after repair according to the original weld requirements. The result was that the inspection was qualified at once, and the repair of the double-curved depth weld defect between the valve nozzle assembly 2 and the spherical head 1 was successfully completed.

[0085] A comparison of existing methods with the method of this invention is shown in Table 1:

[0086] Table 1 Comparison between existing methods and the method of this invention

[0087] Using conventional grinding methods to remove defects in hyperboloid welds not only fails to create arc-shaped grooves but also easily leads to excessive damage to the base material and is inefficient. Especially when the defects are deep, the repair weld will deviate significantly from the original weld area, affecting the in-service inspection of the equipment welds. Although air carbon arc gouging can remove deep defects in hyperboloid welds, it is prohibited because it causes carburization on the surface of the groove to be repaired, which reduces the weldability of the material.

[0088] This invention solves the problem of local processing and removal of defects in hyperboloid deep welds, and ultimately forms an arc-shaped groove for subsequent repair welding. It has been proven that this invention not only successfully found and removed the defects in the hyperboloid deep welds between the valve nozzle assembly 2 and the spherical end cap 1, but also facilitated the repair welding operation by forming an arc-shaped groove for repair welding, resulting in a successful repair welding on the first attempt.

[0089] The working principle of this invention is as follows:

[0090] like Figures 1-4As shown, this invention discloses a method for localized processing and removal of deep hyperboloid weld defects. First, the transverse and circumferential center lines of the groove to be repaired and the surface processing boundary reference lines are drawn on the outer surface of the workpiece based on the location of the weld defect. Then, the workpiece is clamped and aligned. The arc-shaped groove is first processed using a multi-drill method. Next, the slopes on both sides of the arc-shaped groove are machined by milling, and the sharp corners left by the twist drill are removed. The bottom of the arc-shaped groove is then ground. Next, layered processing in the depth direction and layered visual inspection or physical inspection (PT) are used to check the bottom of the arc-shaped groove for defect display until it is completely removed, thus processing the arc-shaped groove into the groove to be repaired. Then, the stepped slopes at both ends of the groove to be repaired are processed. Finally, all surfaces of the groove to be repaired are ground, completing the localized processing and removal of the weld defect. This method can completely remove the weld defect, has high removal efficiency, and the groove to be repaired is a "U"-shaped deep groove with a simple structure and low machining difficulty.

[0091] The pressure vessel industry typically uses air carbon arc gouging and / or grinding to locally remove weld defects. However, for the local removal of deep hyperboloid weld defects, conventional grinding methods not only fail to create arc-shaped grooves, leading to excessive damage to the base material, but are also inefficient. Air carbon arc gouging causes carburization on the surface of the groove to be repaired, which easily leads to cold cracking during subsequent repair welding, resulting in unqualified weld repairs. Therefore, this invention develops a method for locally processing and removing deep hyperboloid weld defects. This method not only avoids excessive damage to the base material and carburization on the surface of the groove to be repaired, but also has relatively high efficiency. Furthermore, it successfully locates and completely removes the weld defect, and the shape and size of the resulting groove to be repaired meet the requirements of the repair operation, ensuring that such weld defects are repaired successfully on the first attempt.

[0092] The present invention uses a boring and milling composite machine with a Φ16mm standard high-speed steel twist drill bit to achieve the machining of arc-shaped grooves on hyperboloids by employing a multi-drilling method; the present invention uses a boring and milling composite machine with a Φ42mm stepped twist drill bit to complete the machining of the slopes on both sides of the arc-shaped groove and the sharp corners left by the twist drill in one pass by employing a milling method.

[0093] This invention employs layered processing in the depth direction, combined with layered visual inspection and liquid penetration inspection to reveal defects at the bottom of the arc-shaped groove. This enables the successful identification and removal of weld defects, ensuring that defects are completely removed in one go and improving removal efficiency.

[0094] The groove initially processed in this invention is an arc-shaped groove. After the defect is removed, the groove becomes a groove to be repaired by welding. The arc-shaped groove is first processed using a drilling method. The arc length and width of the arc-shaped groove are the same as the bottom arc length and width of the groove to be repaired by welding. The processing depth of the arc-shaped groove is 8-10mm above the depth of the weld defect. Then, layered processing and layered visual processing are used in the depth direction. While removing the weld defect, fine adjustments are made according to the actual position of the weld defect, which can greatly improve the integrity of the weld defect removal.

[0095] The present invention uses a stepped drilling method with Φ16mm standard high-speed steel twist drill bits on both ends of the arc-shaped groove, which can improve the efficiency of milling the slope at both ends of the groove with stepped twist drill bits; the electric straight grinder used in the present invention is equipped with a custom-made extended carbide rotary file that can meet the grinding requirements of each surface of the groove to be repaired and welded on the hyperboloid and during the repair welding process.

[0096] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

[0097] Many other changes and modifications can be made without departing from the concept and scope of this invention. It should be understood that this invention is not limited to the specific embodiments, and the scope of this invention is defined by the appended claims.

Claims

1. A method for localized machining and removal of defects in hyperboloid deep welds, characterized in that, Includes the following steps: Step 1: Mark the location of the weld defect (5) on the workpiece, and draw the transverse and circumferential center lines of the groove (6) to be repaired on the outer surface of the workpiece, as well as the surface processing boundary reference line. The groove (6) to be repaired is a "U" shaped deep groove. The bottom arc length of the groove (6) to be repaired is the arc length of the weld defect (5) + the repair welding operation distance of 15~25mm at each end. The bottom width is the operation distance of double welding. The slopes of the two ends and the two sides of the groove (6) to be repaired are 10~15° respectively. The transverse and circumferential center lines and the surface processing boundary reference line of the groove (6) to be repaired are determined according to the bottom arc length, width and the slopes of the two ends and the two sides of the groove (6) to be repaired. Step 2: Workpiece clamping and alignment. The workpiece is clamped and aligned, and the rotation of the machine tool coordinate axis is used to make the center of the machine tool spindle coincide with the center of the valve connector assembly (2) of the workpiece. Step 3: Use a drilling method to process the arc-shaped groove (7). The arc length and width of the arc-shaped groove (7) are the same as the arc length and width of the bottom of the groove (6) to be repaired. The arc length and width of the bottom of the groove (6) to be repaired are greater than the arc length and width of the weld defect (5). The processing depth of the arc-shaped groove (7) is 8~10mm above the depth of the weld defect (5). Step 4: Mill the slope of both sides of the arc-shaped groove (7) and remove any remaining sharp corners, and at the same time grind the bottom of the arc-shaped groove (7); Step 5: Use layered processing in the depth direction and layered visual and liquid penetration inspection to check the bottom defects of the arc groove (7) until the weld defect (5) is completely removed and the arc groove (7) is processed into a groove to be repaired (6); while always maintaining the arc length of the bottom of the arc groove (7), repeat steps 3 and 4 in layers with a processing amount of 1 mm in the depth direction each time until the weld defect (5) is found by visual inspection or PT; then, while always maintaining the arc length of the bottom of the arc groove (7), repeat steps 3 and 4 in layers with a processing amount of 2 mm in the depth direction each time until the weld defect (5) is completely removed by visual inspection and PT and the arc groove (7) is processed into a groove to be repaired (6). Step 6: Machining the stepped slope at both ends of the groove (6) to be repaired; Step 7: Grind all surfaces of the groove (6) to be repaired and perform visual and liquid penetration inspection on all surfaces of the groove (6) to be repaired; Step 8: Perform welding and non-destructive testing on the groove (6) to be repaired.

2. The method for localized processing and removal of defects in hyperboloid deep welds according to claim 1, characterized in that: The bottom arc length of the groove (6) to be repaired is the arc length of the weld defect (5) plus the repair welding operation distance of 20mm at each end. The slopes of the two ends and both sides of the groove (6) to be repaired are 12°.

3. The method for localized processing and removal of defects in hyperboloid deep welds according to claim 1, characterized in that, Step 3 specifically involves: using a boring and milling composite machine to mount a Φ16mm standard high-speed steel twist drill bit, and using a row drilling method to drill arc-shaped grooves (7) at both ends along the transverse centerline of the groove to be repaired (6) and along the circumferential centerline at a spacing less than 3 / 4 of the drill bit diameter, until the bottom arc length of the arc-shaped groove (7) meets the specified bottom arc length dimension of the groove to be repaired (6).

4. The method for localized processing and removal of defects in hyperboloid deep welds according to claim 3, characterized in that, Step 4 specifically involves: using a boring and milling composite machine to clamp a Φ42mm stepped twist drill bit to mill the bottom of the arc-shaped groove (7), sequentially completing the machining of the slope of the two sides of the arc-shaped groove (7) and the sharp corner left by the Φ16mm standard high-speed steel twist drill bit, and then using an electric straight grinder to clamp an extended carbide rotary file to grind the bottom of the arc-shaped groove (7) and perform visual inspection and PT.

5. The method for localized processing and removal of defects in hyperboloid deep welds according to claim 1, characterized in that, Step 6 specifically involves: using a boring and milling machine with a Φ16mm standard high-speed steel twist drill bit, machining the stepped slope of both ends of the groove (6) to be repaired along the circumferential center line according to the step ratio of tanβ, and then using a boring and milling machine with a Φ42mm stepped twist drill bit to mill the stepped slope of both ends into a slope surface; the calculation formula for the step is: when the slope of both ends of the groove (6) to be repaired is β, the step ratio is equal to tanβ.

6. The method for localized processing and removal of defects in hyperboloid deep welds according to claim 1, characterized in that, Step 7 specifically involves using an electric straight grinder to mount an extended carbide rotary file to locally grind the surface of the groove (6) to be repaired so that it meets the shape and size requirements of the groove (6) to be repaired.

7. The method for localized processing and removal of defects in hyperboloid deep welds according to claim 1, characterized in that, Step 8 specifically involves: performing a weld on the groove (6) to be repaired, and conducting a non-destructive inspection on the weld after the repair is completed according to the original weld requirements, thus completing the repair of the hyperboloid depth weld defect between the valve connector assembly and the spherical head of the workpiece.

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