A method for repairing weld defects between tube sheet and nozzle of a steam generator

Abstract

The present invention discloses a method for repairing weld defects between a tube sheet and a nozzle of a steam heating generator. The tube sheet is made of low-alloy steel, and the nozzle is made of carbon steel. The method comprises the following steps: obtaining the positioning parameters of the defect area to be repaired; according to the positioning parameters, obtaining the distance parameter. When the distance parameter is greater than 5 mm, a non-heat-treatment welding process is adopted. When the distance parameter is less than or equal to 5 mm, a temper bead welding process is adopted; obtaining the corresponding repair process, and repairing the defect area to be repaired according to the repair process. The weld defect repair method of the present invention divides the defect area, and different repair processes are selected for different defect areas to be repaired, effectively avoiding the problem that the temperature on the nozzle side has exceeded the standard while the heating temperature of the tube sheet has not reached the required temperature that may occur in the welding heat treatment process.

Description

Technical Field

[0001] This invention relates to the field of weld defect repair, and more particularly to a method for repairing weld defects between the tube sheet and nozzle of a steam generator. Background Technology

[0002] During major overhauls of nuclear power plant units, it is necessary to inspect the welds between the tube sheet and nozzles installed on the thermal generator. One side of the weld is made of low-alloy steel (tube sheet), and the other side is made of carbon steel (nozzle). In applications, the low-alloy steel thickness of the tube sheet exceeds 100mm. If welding is used for repairs, high-temperature tempering heat treatment is required after welding to reduce residual stress in the weld joint and achieve acceptable microstructure and properties. Currently, existing technology achieves this by performing overall heat treatment on the thermal generator during manufacturing. This requires placing the entire thermal generator in a heat treatment furnace. However, thermal generators used in operating units cannot undergo overall tempering and require localized high-temperature tempering. During localized tempering, the temperature reaches 500–600℃. In practice, a problem arises where the tube sheet temperature has not yet reached the required localized heat treatment temperature, but the nozzle temperature has already exceeded the limit. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for repairing weld defects between the tube sheet and the nozzle of a steam generator.

[0004] The technical solution adopted by this invention to solve its technical problem is: providing a method for repairing weld defects between a tube sheet and a nozzle in a steam generator, wherein the tube sheet is made of low-alloy steel and the nozzle is made of carbon steel, and the method includes the following steps:

[0005] S1: Obtain the location parameters of the defect area to be repaired;

[0006] S2: Based on the positioning parameters, obtain the distance parameters. When the distance parameters are greater than 5mm, use a heat-free welding process. When the distance parameters are less than or equal to 5mm, use a tempering weld process.

[0007] S3: Obtain the corresponding repair process, and repair the defective area to be repaired according to the repair process.

[0008] Preferably, step S2 includes: when the distance parameter is less than or equal to 5 mm, obtaining the depth parameter; when the depth parameter is less than one-third of the nozzle wall thickness, using a local tempering weld process; and when the depth parameter is greater than or equal to one-third of the nozzle wall thickness, using an overall tempering weld process.

[0009] Preferably, when the depth parameter is less than one-third of the nozzle wall thickness, step S3 includes the following steps:

[0010] S31: Grind the defective area to be repaired and perform a first preheating treatment. After the preheating treatment, weld a first layer of tempered welding area onto the tube sheet. The first layer of tempered welding area is welded to the connection position between the tube sheet and the patch weld.

[0011] S32: The defective area to be repaired undergoes a first post-heat treatment, and after the first post-heat treatment is completed, the first layer of tempered welding area is polished.

[0012] S33: Perform surface flaw detection on the first layer tempered welding area to determine whether it meets the surface flaw detection requirements. If it does, proceed to step S34. If it does not meet the requirements, determine whether it needs to be repaired. If yes, repair the welding and then grind the first layer tempered welding area. If no, grind the first layer tempered welding area until the surface flaw detection requirements are met.

[0013] S34: Perform a second preheating treatment on the defective area to be repaired. After the preheating treatment, weld a first layer of non-tempered welding area on the nozzle. The first layer of non-tempered welding area is welded above the first tempered welding area and is connected to the patch weld.

[0014] S35: Grind the first non-tempered welded area and weld the second tempered welded area onto the tube sheet. The second tempered welded area is welded above the first tempered welded area and is connected to the periphery of the first non-tempered welded area.

[0015] S36: Grind the second tempered welding area. After grinding, use a non-tempered welding process to weld the filler layer until the filling requirements are met. The lower end face of the filler layer is connected to the first tempered welding area, and the inner side face is connected to the first non-tempered welding area.

[0016] S37: Welding reinforcement layer welding area, wherein the lower edge of the welding reinforcement layer welding area is welded to the first tempering welding area, and the upper edge is welded to the filler layer;

[0017] S38: Perform a second post-heat treatment on the defective area to be repaired, and grind the welding area of ​​the reinforcing layer after the second post-heat treatment is completed;

[0018] S39: Perform volumetric flaw detection on the defective area to be repaired to determine whether it meets the volumetric flaw detection requirements. If yes, the welding is completed. If no, determine whether re-welding is required. If yes, grind the defective area to be repaired after re-welding. If no, grind the defective area to be repaired until the volumetric flaw detection requirements are met.

[0019] Preferably, when the depth parameter is greater than or equal to one-third of the nozzle wall thickness, step S3 includes the following steps:

[0020] S31: Grind the defective area to be repaired and perform surface flaw detection to determine whether the defective area to be repaired meets the surface flaw detection requirements. If yes, perform a third preheating treatment on the defective area to be repaired, and weld the first weld overlay layer after the third preheating treatment. If no, grind until the surface flaw detection requirements are met, perform a fourth preheating treatment and weld the first weld overlay layer. The first weld overlay layer is welded above the tube sheet.

[0021] S32: Perform a third post-heat treatment on the defective area to be repaired, and grind the first weld overlay layer after the third post-heat treatment is completed;

[0022] S33: After being placed for at least 48 hours, the first weld overlay layer is subjected to the surface flaw detection test to determine whether it meets the surface flaw detection requirements. If it does, step S33 is executed. If it does not, it is determined whether it needs to be repaired. If so, after repairing the weld, post-heat treatment is performed and the first weld overlay layer is polished. If not, post-heat treatment is performed and the first weld overlay layer is polished until the surface flaw detection requirements are met.

[0023] S34: Perform a fourth preheating treatment on the defect area to be repaired. After the fourth preheating treatment, deposit a second weld layer on top of the first weld layer and grind the second weld layer.

[0024] S35: Perform the fourth post-heat treatment and polish the defective area to be repaired;

[0025] S36: After placing for at least 48 hours, perform surface flaw detection and volumetric flaw detection on the defect area to be repaired, and determine whether the surface flaw detection and volumetric flaw detection meet the requirements. If they do, proceed to step S37. If they do not meet the requirements, determine whether welding repair is needed. If yes, perform post-heat treatment and grind the first weld overlay after welding repair. If no, perform post-heat treatment and grind the first weld overlay until the surface flaw detection and volumetric flaw detection requirements are met.

[0026] S37: Grind the weld seam of the first weld overlay layer and the second weld overlay layer, perform the surface flaw detection and determine whether the surface flaw detection meets the requirements. If yes, the welding is completed. If no, determine whether it needs to be repaired. If yes, the weld seam is repaired and ground. If no, grind the weld seam until the surface flaw detection requirements are met.

[0027] Preferably, the first layer of tempered weld bead area includes: a first tempered weld bead, a second tempered weld bead, a third tempered weld bead, and a fourth tempered weld bead; the first tempered weld bead is welded around the connection position between the tube sheet and the patch weld; the second tempered weld bead, the third tempered weld bead, and the fourth tempered weld bead are sequentially overlapped and welded.

[0028] Preferably, the first layer of non-tempered weld bead area includes: a first non-tempered weld bead, a second non-tempered weld bead, and a third non-tempered weld bead, which are sequentially overlapped around the first non-tempered weld bead, the second non-tempered weld bead, and the third non-tempered weld bead along the nozzle direction, wherein the inner side of the first layer of non-tempered weld bead overlaps the patch weld seam, and the lower end face overlaps the first layer of tempered weld bead.

[0029] Preferably, the second layer of tempered weld bead region includes: a fifth tempered weld bead, a sixth tempered weld bead, and a seventh tempered weld bead. The fifth tempered weld bead is welded around the connection position between the first layer of tempered weld bead region and the first layer of non-tempered weld bead region. The sixth tempered weld bead and the seventh tempered weld bead are sequentially overlapped along the outer periphery of the fifth tempered weld bead, wherein the sixth tempered weld bead overlaps the fifth tempered weld bead.

[0030] Preferably, the reinforcing layer welding area includes a ninth tempered weld bead and a tenth tempered weld bead, the ninth tempered weld bead overlapping the first tempered welding area and the second tempered welding area respectively, the tenth tempered weld bead being welded around the ninth tempered weld bead, and the tenth tempered weld bead being located on the second tempered welding area.

[0031] Preferably, step S34 includes: grinding the second weld overlay and then continuing to weld until the overall weld height is not less than 9mm.

[0032] Preferably, step S34 further includes: the horizontal distance between the lower edge of the second weld overlay and the lower edge of the first weld overlay is within 3-5 mm.

[0033] Preferably, step S37 includes: controlling the height of the weld overlay after grinding to within 5-6 mm.

[0034] Preferably, step S3 includes: obtaining the weld overlap amount and the weld grinding amount; the weld overlap amount is controlled at 40%-60%; the weld grinding amount is 1 / 3-1 / 2 of the weld height.

[0035] The technical solution of the present invention has the following beneficial effects: The weld defect repair method of the present invention divides the defect area and selects different repair processes for different defect areas to be repaired, which effectively avoids the problem that the tube sheet heating temperature may not reach the required temperature in the welding heat treatment process, while the nozzle side temperature has exceeded the standard. Attached Figure Description

[0036] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0037] Figure 1 This is a flowchart of a method for repairing weld defects between the tube sheet and nozzle of a steam generator, provided by an embodiment of the present invention.

[0038] Figure 2 This is the defect patching diagram for area B provided in this embodiment of the invention;

[0039] Figure 3 This is a weld bead layout diagram of the first layer of tempering welding area provided in an embodiment of the present invention;

[0040] Figure 4 This is a grinding diagram of the weld bead in the first tempering welding area provided in an embodiment of the present invention;

[0041] Figure 5 This is a weld bead layout diagram of the first layer of non-tempering welding area provided in an embodiment of the present invention;

[0042] Figure 6 This is a grinding diagram of the first layer of non-tempered welding area provided in an embodiment of the present invention;

[0043] Figure 7 This is a diagram showing the arrangement of the second tempering welding area and the filler layer weld bead provided in an embodiment of the present invention;

[0044] Figure 8 This is a grinding diagram of the second tempering welding area and the filler layer weld bead provided in an embodiment of the present invention;

[0045] Figure 9 This is a schematic diagram of the tube sheet provided in an embodiment of the present invention;

[0046] Figure 10 This is a schematic diagram of the first weld overlay provided in an embodiment of the present invention;

[0047] Figure 11 This is a grinding diagram of the first weld layer provided in an embodiment of the present invention;

[0048] Figure 12 This is a welding diagram of the second weld overlay provided in an embodiment of the present invention;

[0049] Figure 13 This is a grinding diagram of the second weld layer provided in an embodiment of the present invention;

[0050] Figure 14 This is a grinding diagram of the butt weld seam provided in an embodiment of the present invention. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0052] Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0053] The components of the embodiments of the invention described and illustrated in the accompanying drawings can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0054] The terms used above are for ease of description only and should not be construed as limitations on this technical solution.

[0055] 0 as Figure 1 The diagram shown is a flowchart illustrating a method for repairing weld defects between the tube sheet and nozzle of a steam generator according to the present invention. This embodiment of the weld defect repair method is used to repair the weld between the nozzle 20 side and the tube sheet 10 side of a nuclear power plant steam generator to ensure the integrity of the pressure boundary of the nuclear power plant steam generator. Specifically, the weld defect repair method includes...

[0056] Next steps:

[0057] Step S1: Obtain the location parameters of the defect area to be repaired. Specifically, the operator uses their own measuring instruments to measure and obtain the location parameters of the defect area to be repaired, or obtains the location parameters from some process documents. The operator records the obtained location parameters. These location parameters include, but are not limited to, distance and depth parameters. It can be understood that all...

[0058] Any location information that describes the area of ​​defect to be repaired can be used as a location parameter. In this embodiment, the distance parameter 0 refers to the distance between the area of ​​defect to be repaired and the tube sheet 10; the depth parameter refers to the depth of the filler weld 100 in the area of ​​defect to be repaired.

[0059] Step S2: Based on the positioning parameters, obtain the distance parameters. When the distance parameters are greater than 5mm, use a heat-free welding process; when the distance parameters are less than or equal to 5mm, use tempering welding.

[0060] The welding process is described. Specifically, in this embodiment, the defect area to be repaired is divided into defect area A, defect area B, and defect area C; based on the obtained distance parameters, the defect area to be repaired is judged, and the judgment is made...

[0061] The method determines whether the defect area to be repaired is a defect in area A. If the distance parameter is greater than 5mm, the defect area to be repaired is an area A defect, and the welding process for area A defects is adopted, which is a heat-free welding process. If it is not an area A defect, further, based on the depth parameter, it is determined whether the defect area to be repaired is a defect in area B. If the depth parameter is less than one-third of the nozzle wall thickness, the defect area to be repaired is an area B defect, and the welding process for area B defects is adopted, which is a partial tempering weld process. If it is not an area B defect, the defect area to be repaired is an area C defect, and the welding process for area C defects is an overall tempering weld process. It can be understood that this embodiment divides the defect area to be repaired into three different defect areas for example to illustrate the method. Different division methods applied to the inventive concept of this embodiment by those skilled in the art are also within the protection scope of this embodiment.

[0062] Step S3: Obtain the corresponding repair process and repair the defective area to be repaired according to the repair process. Specifically, before repairing the defective area to be repaired, a heating fixture for preheating and post-heat treatment is first installed on the part to be repaired. In step S2, after judging the defective area to be repaired, the corresponding repair process is obtained according to the judged defective area. Different repair processes are used for different defective areas to be repaired.

[0063] In this embodiment, if the defective area to be repaired is area A, the area repair process adopted is to repair the entire area using a heat-free process.

[0064] In this embodiment, if the defect area to be repaired is a defect in area B, the repair process specifically includes the following steps:

[0065] S31: Grind the defective area to be repaired and perform a first preheating treatment. After the preheating treatment, weld the first layer of tempered weld area 30 onto the tube sheet 20. The first layer of tempered weld area 30 is welded to the connection position between the tube sheet 20 and the patch weld 100. Specifically, grind the defective area to be repaired until a smooth transition is achieved. After grinding to a smooth transition, turn on the heating fixture and perform a first preheating treatment on the defective area to be repaired. During the preheating process, the preheating temperature is not lower than 175℃. After the preheating treatment is completed, start welding the first layer of tempered weld area 30. The first layer of tempered weld area 30 is welded above the tube sheet 10. The first layer of tempered weld area 30 may include a first tempered weld pass 103, a second tempered weld pass 104, a third tempered weld pass 101, and a fourth tempered weld pass 102. A first tempered weld bead 103 is welded at the connection between the tube sheet and the patch weld 100, surrounding the periphery of the patch weld 100. After the first tempered weld bead 103 is welded, a second tempered weld bead 104, a third tempered weld bead 101, and a fourth tempered weld bead 102 are welded sequentially according to the weld overlap. The second tempered weld bead 104 surrounds the first tempered weld bead 103, the third tempered weld bead 101 surrounds the second tempered weld bead 104, and the fourth tempered weld bead 102 surrounds the third tempered weld bead 101. The opposite side of the tube sheet 10 and the nozzle 20 is the upper side of the tube sheet 10.

[0066] Furthermore, in another embodiment, the number of weld passes in the first layer tempering welding area 30 can be set to three-pass welding or other applicable field welding pass numbers, depending on the welding situation.

[0067] S32: The defective area to be repaired undergoes a first post-heat treatment. After the first post-heat treatment is completed, the first tempered weld area 30 is ground. Specifically, during the first post-heat treatment, the temperature is maintained at 250℃-300℃ for 4 hours. After the first post-heat treatment is completed, the first tempered weld area 30 is ground until a smooth transition is achieved. During the grinding process, grinding is performed sequentially starting from the first tempered weld bead 103.

[0068] Furthermore, in another embodiment, grinding can also be performed sequentially starting from the fourth tempered weld bead 102.

[0069] S33: Perform surface flaw detection on the first layer tempered welding area 30 to determine whether it meets the surface flaw detection requirements. If it does, proceed to step S34. If it does not meet the requirements, determine whether it needs to be repaired. If it does, repair the welding and then grind the first layer tempered welding area 30. If not, grind the first layer tempered welding area 30 until it meets the surface flaw detection requirements. Specifically, for the first layer of tempered welding area 30, surface flaw detection is performed. The part to be repaired must first be cooled to room temperature. The cooling temperature can be monitored intermittently using some temperature measuring instruments. After cooling to room temperature, surface flaw detection is performed on the polished surface. The results are used to determine whether the flaw detection requirements are met. If they are met, step S34 is executed. If they are not met, the reasons for not meeting the surface flaw detection requirements are analyzed based on the flaw detection report. If re-welding is required, the areas that do not meet the requirements are re-welded according to the flaw detection report. After welding, the surface is polished again. After polishing, the surface flaw detection is performed again until the surface flaw detection requirements are met. If only polishing is required, the areas that do not meet the requirements are polished according to the surface flaw detection report until the surface flaw detection requirements are met.

[0070] S34: Perform a second preheating treatment on the defective area to be repaired. After the preheating treatment, weld a first non-tempered welding area 40 onto the nozzle 10. The first non-tempered welding area 40 is welded above the first tempered welding area 30 and is connected to the patch weld 100. Specifically, after the flaw detection of the first tempered welding area 30 meets the requirements, open the heating fixture and perform a second preheating treatment on the defective area to be repaired. After the second preheating treatment is completed, weld the first non-tempered welding area 40. The first non-tempered welding area 40 is welded above the first tempered welding area 30 and is connected to the patch weld 100. The first non-tempered weld area 40 may include a first non-tempered weld bead 107, a second non-tempered weld bead 105, and a third non-tempered weld bead 106. The first non-tempered weld bead 107 is along the direction of the nozzle 20 and abuts against the first tempered weld area 30, and is welded around the periphery of the patch weld 100. The second non-tempered weld bead 105 and the third non-tempered weld bead 106 are welded sequentially along the direction of the nozzle 20 according to the weld bead overlap, and the second non-tempered weld bead 105 and the third non-tempered weld bead 106 are also welded around the periphery of the patch weld 100.

[0071] Furthermore, in some other embodiments, the number of weld passes in the first non-tempered welding area 40 can be set to four passes or other applicable field welding passes depending on the welding situation.

[0072] S35: Grind the first non-tempered weld area 40 and weld the second tempered weld area 50 onto the tube sheet 20. The second tempered weld area 50 is welded above the first tempered weld area 30 and is connected to the outer periphery of the first non-tempered weld area. Specifically, after welding the first non-tempered weld area 40, grind it until it is smooth. During the grinding process, grinding is performed sequentially starting from the first non-tempered weld pass 107. After grinding the first non-tempered weld area 40, welding the second tempered weld area 50 begins. The second tempered weld area 50 is welded above the first tempered weld area 30 and is connected to the outer periphery of the first non-tempered weld area. The second tempered welding area 50 may include a fifth tempered weld bead 111, a sixth tempered weld bead 110, and a seventh tempered weld bead 109. The lower end face of the fifth tempered weld bead 111 overlaps with the first tempered welding area 30, and the inner side face of the fifth tempered weld bead 111 overlaps with the first non-tempered welding area 40. The fifth tempered weld bead 111 is welded around the filler weld 100. According to the overlap amount, the sixth tempered weld bead 110 and the seventh tempered weld bead 109 extend outward in sequence to weld around the fifth tempered weld bead 111.

[0073] Furthermore, in another embodiment, the number of weld passes in the second tempering welding area 50 can be set to four passes or other applicable field welding passes depending on the welding situation.

[0074] Furthermore, in some other embodiments, the grinding of the first non-tempered weld area 40 may also begin sequentially from the third non-tempered weld pass 106.

[0075] S36: The filler layer 108 is welded using a non-tempered weld process until the filling requirements are met. The lower end face of the filler layer 108 is in contact with the first tempered weld area 30, and the inner side face is in contact with the first non-tempered weld area 40, and then ground. Specifically, after welding the second tempered weld area 50, the filler layer 108 is welded using a non-tempered weld process. Specifically, the lower end face of the filler layer 108 abuts against the second tempered weld area 50, and the inner side face abuts against the filler weld 100. After the filler layer 108 is welded to meet the filling requirements, the second tempered weld area 50 and the filler layer 108 are ground to a smooth transition.

[0076] S37: Welding reinforcement layer welding area, the lower edge of the reinforcement layer welding area is welded to the first tempered welding area 30, and the upper edge is welded to the filler layer 108. Specifically, after grinding, the reinforcement layer welding area is welded at the abutment position of the first tempered welding area 30 and the second tempered welding area 50. The reinforcement layer welding area may include a ninth tempered weld bead 113 and a tenth tempered weld bead 112. The ninth tempered weld bead 113 is wrapped around and overlapped at the position where the upper edge of the first tempered welding area 30 abuts the lower edge of the second tempered welding area 50, and the tenth tempered weld bead 112 is wrapped around and overlapped above the ninth tempered weld bead 113 along the nozzle 20 direction.

[0077] Furthermore, in some other embodiments, the welding area of ​​the reinforcing layer may be arranged with three welds or other weld passes applicable to the field welding conditions, depending on the welding situation.

[0078] S38: Perform a second post-heat treatment on the defective area to be repaired, and grind the welding area of ​​the reinforcing layer after the second post-heat treatment is completed. Specifically, after the welding of the reinforcing layer welding area is completed, open the heating fixture, perform post-heat treatment on the defective area to be repaired, and after the second post-heat treatment is completed, grind the defective area to be repaired until a smooth transition is achieved.

[0079] S39: Perform volumetric flaw detection on the defective area to be repaired to determine whether it meets the volumetric flaw detection requirements. If yes, welding is completed; if no, determine whether re-welding is required. If yes, re-weld and then grind the defective area to be repaired; if no, grind the defective area to be repaired until the volumetric flaw detection requirements are met. Specifically, after the second post-heat treatment, the part to be repaired is cooled to room temperature. After cooling to room temperature, volumetric flaw detection is performed on the area to be repaired. If it meets the requirements, welding is completed; if not, analyze the reasons for not meeting the surface flaw detection report based on the flaw detection report. If re-welding is required, re-weld the areas that do not meet the requirements according to the flaw detection report. After welding, perform post-heat treatment and cool to room temperature for grinding. After grinding, perform surface flaw detection again until the surface flaw detection requirements are met. If only grinding is required, grind the areas that do not meet the requirements according to the surface flaw detection report until the surface flaw detection requirements are met.

[0080] In this embodiment, if the defect area to be repaired is a C-zone defect, the repair process specifically includes the following steps:

[0081] S31: Grind the defective area to be repaired and perform surface flaw detection to determine whether the defective area to be repaired meets the surface flaw detection requirements. If yes, perform a third preheating treatment on the defective area to be repaired, and then weld the first weld overlay layer 114 after the third preheating treatment. If not, grind until the surface flaw detection requirements are met, perform preheating treatment, and then weld the first weld overlay layer 114. The first weld overlay layer 114 is welded above the tube sheet 20. Specifically, grind the area to be repaired until the surface of the defective area to be repaired is smoothly transitioned, and then clean the ground surface. After cleaning, use an air gun or other blowing equipment to blow the ground surface. After cleaning, turn on the heating fixture and perform preheating treatment on the defective area to be repaired. After the third preheating treatment is completed, start welding the first tempered welding area 30. The first tempered welding area 30 may include a first tempered weld bead 103, a second tempered weld bead 104, a third tempered weld bead 101, and a fourth tempered weld bead 102. The first tempered weld bead 103 and... The patch weld 100 is overlapped and welded around the periphery of the patch weld 100. After the first tempered weld 103 is welded, the second tempered weld 104, the third tempered weld 101, and the fourth tempered weld 102 are welded in sequence according to the overlap amount. The second tempered weld 104 surrounds the first tempered weld 103, the third tempered weld 101 surrounds the second tempered weld 104, and the fourth tempered weld 102 surrounds the third tempered weld 101. The first tempered weld 103 is welded at the connection position between the tube sheet 10 and the weld.

[0082] S32: Perform a third post-heat treatment on the defective area to be repaired, and then grind the first weld overlay layer 114 after the third post-heat treatment is completed. Specifically, after the first weld overlay layer 114 is welded, open the heating fixture to perform a third post-heat treatment, and then grind the first weld overlay layer 114 until it is smoothly transitioned after the third post-heat treatment is completed. Understandably, during the grinding process, grinding can begin from any end of the first weld overlay layer 114.

[0083] S33: After being placed for at least 48 hours, the first weld overlay layer 114 is subjected to surface flaw detection to determine whether it meets the surface flaw detection requirements. If it does, proceed to step S33. If it does not, determine whether re-welding is required. If so, perform post-heat treatment and grind the first weld overlay layer after re-welding. If not, perform post-heat treatment and grind the first weld overlay layer until the surface flaw detection requirements are met. Specifically, after grinding the first weld overlay layer 114, it is placed for at least 48 hours. After placement, the first weld overlay layer 114 is subjected to surface flaw detection to determine whether the flaw detection result meets the flaw detection requirements. If it does, welding of the second weld overlay layer 115 begins. If it does not, the specific tooling is reopened for post-heat treatment. After post-heat treatment, grinding continues, and after being placed for at least 48 hours, surface flaw detection is performed until the flaw detection requirements are met.

[0084] S34: Perform a fourth preheating treatment on the defect area to be repaired. After the fourth preheating treatment, deposit a second weld overlay 115 on top of the first weld overlay 114 and grind the second weld overlay. Specifically, during the welding process, the horizontal distance between the lower edge of the second weld overlay 115 and the lower edge of the first weld overlay 114 should be maintained within 3-5 mm.

[0085] S35: Perform the fourth post-heat treatment and grind the defective area to be repaired. Specifically, after the welding is completed, open the heating fixture and perform the fourth post-heat treatment. After the fourth post-heat treatment, grind the second weld overlay layer 115. During the grinding process, grinding can start from any end of the second weld overlay layer 115. The overall weld overlay height of the first weld overlay layer 114 and the second weld overlay layer 115 after grinding should not be less than 9mm. During the grinding process, it is necessary to measure the height of the first weld overlay layer 114, the second weld overlay layer 115 and the overall weld overlay multiple times to avoid the height being less than 9mm due to excessive grinding.

[0086] S36: After placing for at least 48 hours, perform surface flaw detection and volumetric flaw detection on the defective area to be repaired, and determine whether the surface flaw detection and volumetric flaw detection meet the requirements. If they do, proceed to step S37. If they do not meet the requirements, determine whether welding repair is needed. If yes, perform post-heat treatment and grind the first weld overlay after welding repair. If no, perform post-heat treatment and grind the first weld overlay until the surface flaw detection and volumetric flaw detection requirements are met. Specifically, after placement, surface flaw detection and volumetric flaw detection are performed on the defective area to be repaired to determine whether the surface flaw detection and volumetric flaw detection meet the requirements. If they do, step S37 is executed. If they do not meet the requirements, the reasons for not meeting the surface flaw detection report are analyzed. If welding is required, the area that does not meet the requirements is re-welded according to the flaw detection report. After welding, post-heat treatment is performed, and the area is cooled to room temperature for grinding. After grinding, surface flaw detection is performed again until the surface flaw detection requirements are met. If only grinding is required, post-heat treatment is performed, and the area is cooled to room temperature. Then, the area that does not meet the requirements is ground according to the surface flaw detection report until the surface flaw detection requirements are met.

[0087] S37: Grind the weld seams of the first weld overlay layer 114 and the second weld overlay layer 115, perform surface flaw detection, and determine whether the surface flaw detection meets the requirements. If yes, the welding is complete; if no, determine whether re-welding is needed. If yes, re-weld the weld seam and grind it; if no, grind the weld seam until the surface flaw detection requirements are met. Specifically, grind the weld seams of the first weld overlay layer 114 and the second weld overlay layer 115. During the grinding process, the height of the weld seam needs to be measured multiple times to ensure that the height of the ground weld seam is within 5-6mm. Understandably, measuring the height of the weld seam multiple times during the grinding process is to avoid over-grinding that fails to meet the height requirements of the weld seam.

[0088] In this embodiment, step S3 includes obtaining the weld bead overlap amount and the weld bead grinding amount. The weld bead overlap amount refers to the overlap or overlap between adjacent weld beads or weld beads that need to overlap during the welding process. The weld bead grinding amount refers to the controlled amount of grinding treatment performed on the weld surface with burrs during or after the welding process. Among them, the weld bead overlap amount is calculated by computer finite element model based on the tempering temperature field. The overlap amount is increased from 30% to 70%. The tempering area of ​​the subsequent weld bead gradually acts on the coarse grain area of ​​the previous weld bead. It is verified that the overlap amount is most reasonable within the tempering temperature coverage range of 40%-60%. The weld bead grinding amount is controlled at 1 / 3-1 / 2 of the weld bead height.

[0089] In this embodiment, the temperature of the first preheating treatment, the second preheating treatment, and the third preheating treatment is maintained at 175°C. Understandably, if a second preheating treatment is required, the temperature must still be maintained at 175°C.

[0090] In this embodiment, after the first, second, third, and fourth post-heat treatments, the post-heat temperature is maintained at 250℃-300℃ for 4 hours. Understandably, if a second post-heat treatment is required, the post-heat temperature must still be maintained at 250℃-300℃ for 4 hours.

[0091] In this embodiment, the first weld overlay 114 is welded vertically upward along the circumference, with the lower side starting the arc and the upper side ending the arc. The diameter of the first weld overlay 114 is 18-22 mm larger than the outer diameter of the carbon steel nozzle 20.

[0092] In this embodiment, the second weld overlay 115 is welded in a circumferential upward manner with the lower side starting and the upper side ending the arc. The weld overlay diameter of the second weld overlay 115 is 8-12 mm larger than the outer diameter of the carbon steel nozzle 20.

[0093] In this embodiment, the heating fixture used for preheating and post-heating is installed before welding repair of the defect. Specifically, the heating fixture may include an upper clamping member and a lower clamping member, both of which are disc-shaped and have cavities. When clamping the workpiece to be welded, the upper clamping member is located on the upper surface of the workpiece, and the lower clamping member is located on the lower surface. The workpiece to be repaired is enclosed inside the heating fixture through the cavities of the upper and lower clamping members. A radial through hole for the nozzle 20 to extend outward is provided at the junction of the upper and lower clamping members. Furthermore, a heating device is provided inside the cavity of the heating fixture. After the heating fixture is installed on the workpiece to be repaired, the heating device can act on the workpiece. When heat treatment is required, the heating device can be turned on to heat the workpiece, and the heating device can be turned off after heating is completed.

[0094] Understandably, in this embodiment, the welding electrical parameters and filler metal dimensions need to be controlled during the welding process. Specifically, when welding the first layer on the low-alloy tube sheet side 10 or the carbon steel nozzle side 20, the welding current needs to be controlled at 80-85 amps, the voltage at 24-26 V, and the filler metal diameter should be 2.5 mm. When welding the second and subsequent layers, the current should be controlled at 95-120 amps, the voltage at 24-28 V, and the filler metal diameter should be 3.2 mm. Furthermore, the welding heat input needs to be calculated using the calculation process in Formula 1:

[0095] Q(KJ / mm)=[U(V)×I(A)×0.001] / v(mm / s)Formula 1

[0096] Where U(V) is the welding voltage, I(A) is the welding current, and v(mm / s) is the welding speed.

[0097] It is understood that the above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and do not limit the scope of protection of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A method for repairing weld defects between a tube sheet and a nozzle in a steam generator, wherein the tube sheet is made of low-alloy steel and the nozzle is made of carbon steel, characterized in that... The method includes the following steps: S1: Obtain the positioning parameters of the defect area to be repaired, including distance parameters and depth parameters; S2: Adopt the corresponding repair process according to the positioning parameters; When the distance parameter is less than or equal to 5mm, the repair process is selected according to the depth parameter; when the depth parameter is less than one-third of the nozzle wall thickness, a local tempering weld process is adopted; when the depth parameter is greater than or equal to one-third of the nozzle wall thickness, an overall tempering weld process is adopted. When the distance parameter is greater than 5mm, a heat-free welding process is used; S3: Repair the defective area to be repaired according to the repair process; Wherein, the distance parameter is the distance between the defective area to be repaired and the tube sheet, and the depth parameter is the depth of the filler weld in the defective area to be repaired.

2. The weld defect repair method according to claim 1, characterized in that, When the depth parameter is less than one-third of the nozzle wall thickness, step S3 includes the following steps: S31: Grind the defective area to be repaired and perform a first preheating treatment. After the preheating treatment, weld a first layer of tempered welding area onto the tube sheet. The first layer of tempered welding area is welded to the connection position between the tube sheet and the patch weld. S32: The defective area to be repaired undergoes a first post-heat treatment, and after the first post-heat treatment is completed, the first layer of tempered welding area is polished. S33: Perform surface flaw detection on the first layer tempered welding area to determine whether it meets the surface flaw detection requirements. If it does, proceed to step S34. If it does not meet the requirements, determine whether it needs to be repaired. If yes, repair the welding and then grind the first layer tempered welding area. If no, grind the first layer tempered welding area until the surface flaw detection requirements are met. S34: Perform a second preheating treatment on the defective area to be repaired. After the preheating treatment, weld a first layer of non-tempered welding area on the nozzle. The first layer of non-tempered welding area is welded above the first tempered welding area and is connected to the patch weld. S35: Grind the first non-tempered welded area and weld the second tempered welded area onto the tube sheet. The second tempered welded area is welded above the first tempered welded area and is connected to the periphery of the first non-tempered welded area. S36: Grind the second layer of tempered welding area. After grinding, use non-tempered welding process to weld the filler layer until the filling requirements are met. The lower end face of the filler layer is connected to the first layer of tempered welding area, and the inner side face is connected to the first layer of non-tempered welding area. S37: Welding reinforcement layer welding area, the lower edge of the welding reinforcement layer welding area is welded to the second tempering welding area, and the upper edge is welded to the filler layer; S38: Perform a second post-heat treatment on the defective area to be repaired, and grind the welding area of ​​the reinforcing layer after the second post-heat treatment is completed; S39: Perform volumetric flaw detection on the defective area to be repaired to determine whether it meets the volumetric flaw detection requirements. If yes, the welding is completed. If no, determine whether re-welding is required. If yes, grind the defective area to be repaired after re-welding. If no, grind the defective area to be repaired until the volumetric flaw detection requirements are met.

3. The weld defect repair method according to claim 1, characterized in that, When the depth parameter is greater than or equal to one-third of the nozzle wall thickness, step S3 includes the following steps: S31: Grind the defective area to be repaired and perform surface flaw detection to determine whether the defective area to be repaired meets the surface flaw detection requirements. If yes, perform a third preheating treatment on the defective area to be repaired, and weld the first weld overlay layer after the third preheating treatment. If no, grind until the surface flaw detection requirements are met, perform a fourth preheating treatment and weld the first weld overlay layer. The first weld overlay layer is welded above the tube sheet. S32: Perform a third post-heat treatment on the defective area to be repaired, and grind the first weld overlay layer after the third post-heat treatment is completed; S33: After being placed for at least 48 hours, the first weld overlay layer is subjected to the surface flaw detection test to determine whether it meets the surface flaw detection requirements. If it does, step S33 is executed. If it does not, it is determined whether it needs to be repaired. If so, after repairing the weld, post-heat treatment is performed and the first weld overlay layer is polished. If not, post-heat treatment is performed and the first weld overlay layer is polished until the surface flaw detection requirements are met. S34: Perform a fourth preheating treatment on the defect area to be repaired. After the fourth preheating treatment, deposit a second weld layer on top of the first weld layer and grind the second weld layer. S35: Perform the fourth post-heat treatment and polish the defective area to be repaired; S36: After placing for at least 48 hours, perform surface flaw detection and volumetric flaw detection on the defect area to be repaired, and determine whether the surface flaw detection and volumetric flaw detection meet the requirements. If they do, proceed to step S37. If they do not meet the requirements, determine whether welding repair is needed. If yes, perform post-heat treatment and grind the first weld overlay after welding repair. If no, perform post-heat treatment and grind the first weld overlay until the surface flaw detection and volumetric flaw detection requirements are met. S37: Grind the weld seam of the first weld overlay layer and the second weld overlay layer, perform the surface flaw detection and determine whether the surface flaw detection meets the requirements. If yes, the welding is completed. If no, determine whether it needs to be repaired. If yes, the weld seam is repaired and ground. If no, grind the weld seam until the surface flaw detection requirements are met.

4. The weld defect repair method according to claim 2, characterized in that, The first tempered welding area includes: a first tempered weld bead, a second tempered weld bead, a third tempered weld bead, and a fourth tempered weld bead; the first tempered weld bead is welded around the connection position between the tube sheet and the patch weld; the second tempered weld bead, the third tempered weld bead, and the fourth tempered weld bead are sequentially overlapped and welded.

5. The weld defect repair method according to claim 2, characterized in that, The first layer of non-tempered welding area includes: a first non-tempered weld bead, a second non-tempered weld bead, and a third non-tempered weld bead, which are sequentially overlapped around the nozzle direction. The inner side of the first layer of non-tempered weld bead overlaps the patch weld seam, and the lower end face overlaps the first layer of tempered welding area.

6. The weld defect repair method according to claim 2, characterized in that, The second tempered welding area includes a fifth tempered weld bead, a sixth tempered weld bead, and a seventh tempered weld bead. The fifth tempered weld bead is welded around the connection between the first tempered welding area and the first non-tempered welding area. The sixth tempered weld bead and the seventh tempered weld bead are sequentially overlapped along the outer periphery of the fifth tempered weld bead, wherein the sixth tempered weld bead overlaps the fifth tempered weld bead.

7. The weld defect repair method according to claim 2, characterized in that, The reinforcing layer welding area includes a ninth tempered weld bead and a tenth tempered weld bead. The ninth tempered weld bead overlaps with the first tempered welding area and the second tempered welding area, respectively. The tenth tempered weld bead is welded around the ninth tempered weld bead and is located on the second tempered welding area.

8. The weld defect repair method according to claim 3, characterized in that, Step S34 includes: grinding the second weld overlay and then continuing to weld until the overall weld height is not less than 9mm.

9. The weld defect repair method according to claim 3, characterized in that, Step S34 further includes: the horizontal distance between the lower edge of the second weld overlay and the lower edge of the first weld overlay is within 3-5 mm.

10. The weld defect repair method according to claim 3, characterized in that, Step S37 includes: controlling the height of the weld seam after grinding to within 5-6mm.

11. The weld defect repair method according to claim 1, characterized in that, Step S3 includes: obtaining the weld overlap amount and weld grinding amount; the weld overlap amount is controlled between 40% and 60%; The amount of grinding required for the weld bead is 1 / 3 to 1 / 2 of the weld bead height.

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