A method for repairing cracks in an inner ring support plate of an aero-engine aftercasing machining assembly

Abstract

A method for repairing cracks in the inner ring support plate of the aero-engine rear casing machining assembly, belonging to the field of aero-engine repair technology, includes the following steps: locating the crack in the inner ring support plate; manually grinding and removing the crack; repairing the ground weld; polishing and finishing the repaired weld; performing post-weld inspection on the repaired weld; performing post-weld aging heat treatment on the aero-engine rear casing machining assembly; performing fluorescent inspection on the aero-engine rear casing machining assembly; and performing dimensional inspection on the aero-engine rear casing machining assembly. This method for repairing cracks in the inner ring support plate of the aero-engine rear casing machining assembly avoids the complete scrapping of the aero-engine rear casing machining assembly through crack repair, effectively reducing the overhaul cost of the aero-engine, improving the overhaul capability of the aero-engine, and achieving high-quality restoration of the part's morphology and performance after repair, effectively meeting the assembly and use requirements of the aero-engine.

Description

Technical Field

[0001] This invention belongs to the field of aero-engine repair technology, and in particular relates to a method for repairing cracks in the inner ring support plate of the aero-engine rear casing machining assembly. Background Technology

[0002] As a major load-bearing component of an aero-engine, the rear casing primarily supports and secures the turbine rotor. The rear casing machining assembly is located within the rear casing and serves as its base. This assembly is a welded assembly consisting of an inner ring casing, an outer ring casing, and a support tube, with dozens of welds, making its structure complex.

[0003] Currently, when an aircraft engine reaches the end of its service life, it needs to be returned to the factory for major overhaul. During non-destructive testing, if many cracks are found in the inner ring support plate of the rear casing machining assembly, in the past, the entire rear casing machining assembly could only be scrapped. This not only increased the replacement rate of the rear casing machining assembly, but also greatly increased the overhaul cost of the aircraft engine. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a method for repairing cracks in the inner ring support plate of the aft casing machining assembly of an aero engine. By repairing the cracks, the entire aft casing machining assembly is spared from being scrapped, effectively reducing the overhaul cost of the aero engine and improving its overhaul capability. The repaired aft casing machining assembly achieves high-quality restoration of part morphology and performance, effectively meeting the assembly and use requirements of the aero engine.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for repairing cracks in the inner ring support plate of a rear casing machining assembly of an aero engine, comprising the following steps:

[0006] Step 1: Locate the crack in the inner ring support plate;

[0007] Step 2: Manually use pliers to repair and polish away the cracks;

[0008] Step 3: Repair the ground weld by welding;

[0009] Step 4: Polish and refine the repair weld;

[0010] Step 5: Conduct post-weld inspection of the repair weld;

[0011] Step Six: Perform post-weld aging heat treatment on the machined components of the rear casing;

[0012] Step 7: Perform fluorescence inspection on the machining components of the rear casing;

[0013] Step 8: Perform dimensional checks on the rear casing machining components.

[0014] In step one, visual inspection and penetrant testing are used to determine the location of the crack in the inner ring support plate and the size range of the crack.

[0015] In step two, the calibrated inner ring support plate crack is first removed by manual grinding. Grinding is performed along the crack direction, and the grinding width and depth should be based on the standard of completely removing the crack, while avoiding grinding beyond the range, until a weld is formed. Then, the bevel of the weld joint and the surface on both sides of the bevel are cleaned to remove the oxide layer, and the oxide layer removal range should not be less than 10mm. After that, the surface where the oxide layer has been removed is wiped clean, and finally, the ground area is subjected to fluorescent inspection to ensure that there are no crack residues.

[0016] In step three, the rear casing machining components are first rigidly fixed using welding fixtures. Then, the ground weld is repaired using manual argon arc welding. During repair welding, welding should begin from the middle of the weld and continue until both ends of the weld are finished. The welding duration should not exceed 1 minute. Welding can only continue after the weld has cooled to room temperature. The welding parameters are as follows: welding current 80A~140A, time interval 140ms~160ms, argon gas flow rate of welding torch 8L / min~12L / min, back shielding gas flow rate 6L / min~10L / min, welding wire diameter 0.8mm~1.6mm, welding wire type HGH4169, tungsten electrode diameter Ф2.0mm, and tungsten electrode type WCe20.

[0017] The welding fixture includes a support base, an outer ring housing clamping mechanism, an outer ring housing positioning pin, an inner ring housing positioning ring, a lower inner ring housing clamping mechanism, an upper inner ring housing clamping mechanism, and an inner ring housing expansion and positioning mechanism; the support base is disc-shaped; the number of outer ring housing clamping mechanisms is several, and these mechanisms are evenly distributed along the circumference of the support base; the number of outer ring housing positioning pins is also several, and these pins are evenly distributed along the circumference of the support base. The inner ring housing is staggered with the outer ring housing positioning pins; the inner ring housing expansion and positioning mechanism is located at the center of the support base; there are several lower pressing mechanisms for the inner ring housing, and these mechanisms are located on the expansion and positioning blocks of the inner ring housing expansion and positioning mechanism; the inner ring housing positioning ring is coaxially arranged on the outside of the inner ring housing expansion and positioning mechanism, and the pressure plate of the lower pressing mechanism is located above the inner ring housing positioning ring; the upper pressing mechanism is located above the lower pressing mechanism.

[0018] In step four, the excess height of the repair weld is first removed by mechanical grinding. Then, the repair weld with the excess height removed is partially polished, requiring a smooth transition between the polished part and the unpolished base material until the surface finish meets the design requirements of the drawings.

[0019] In step five, ① Visual inspection: A 10x magnifying glass is used to visually inspect the polished and refined weld seam and its transition area with the base material. The surface must be free of cracks, incomplete fusion, incomplete penetration, and undercut defects. Surface porosity or inclusions are permitted on a 100mm weld seam, but the maximum size of any porosity or inclusion must not exceed 1mm, and the number of defects must not exceed two. The minimum distance between defects must be no less than 2mm. If the visual inspection requirements are not met, repair welding is permitted to eliminate the defects. ② Fluorescent inspection: A fluorescent inspection is performed on the polished and refined weld seam and its transition area with the base material. The surface must be free of cracks. Surface porosity or inclusions are permitted on a 100mm weld seam, but the maximum size of any porosity or inclusion must not exceed 1mm. Surface porosity and inclusions exceeding 1mm but less than 0.5mm are not counted, and the number of defects must not exceed two, with a minimum distance of 2mm between defects. If the fluorescent inspection requirements are not met, repair welding is allowed to eliminate the defects, but the same defect must not be repaired more than twice. ③ X-ray inspection: X-ray inspection is performed on the repaired welds after polishing and the transition area with the base material. The surface must be free of cracks and incomplete penetration defects. Surface porosity or inclusions are allowed on 100mm welds, but the maximum size of the porosity or inclusion must not exceed 1.3mm, and the number of defects must not exceed four, with a minimum distance of twice the maximum defect size. The total defect area must not exceed 12mm². 2 If the X-ray inspection requirements are not met, repair welding is allowed to eliminate the defect, but the number of repair welding operations for the same defect shall not exceed 2.

[0020] In step six, the rear casing machining assembly, after the weld repair and post-weld inspection, is sent into an aging heat treatment furnace to remove residual stress. The aging heat treatment parameters are as follows: first, hold at 700℃~750℃ for 6h~10h, then furnace cool to 600℃~650℃ at a rate of 50℃ / h±10℃ / h and hold for 6h~10h, and then air cool to room temperature.

[0021] In step seven, during the fluorescent inspection of the rear casing machining components, it is required that the surface of the weld repair weld be free of cracks and defects. Surface porosity or inclusions are allowed on welds with a diameter of 100 mm, but the maximum size of the porosity or inclusions must not exceed 1 mm. Surface porosity and inclusions smaller than 0.5 mm are not counted. The number of defects must not exceed two, and the minimum distance between defects must not be less than 2 mm. If the fluorescent inspection requirements are not met, it is allowed to repair the defects to eliminate them, but the number of repairs for the same defect must not exceed two.

[0022] In step eight, the inner diameter of the inner ring stop of the rear housing machining assembly is first measured. Then, the bearing housing is assembled into the inner ring housing of the rear housing machining assembly. After that, the end face runout and radial runout of the bearing housing are measured, and the measurement results are required to meet the design requirements of the drawings. If the measurement results do not meet the requirements, the stop of the inner ring of the housing is allowed to be machined to refine the inner diameter of the stop until the measurement results of the end face runout and radial runout of the bearing housing meet the requirements.

[0023] The beneficial effects of this invention are:

[0024] The present invention provides a method for repairing cracks in the inner ring support plate of the aero-engine rear casing machining assembly. By repairing the cracks, the entire rear casing machining assembly is prevented from being scrapped, effectively reducing the overhaul cost of the aero-engine and improving its overhaul capability. The repaired rear casing machining assembly achieves high-quality restoration of part morphology and performance, effectively meeting the assembly and use requirements of the aero-engine. Attached Figure Description

[0025] Figure 1 A schematic diagram of the machining components for the rear casing;

[0026] Figure 2 This is a schematic diagram showing the location of the crack in the inner ring support plate.

[0027] Figure 3 This is a top view of the welding fixture;

[0028] Figure 4 This is a cross-sectional front view of the welding fixture;

[0029] In the figure, 1—inner ring casing, 2—outer ring casing, 3—support tube, 4—inner ring support plate crack, 5—support base, 6—outer ring casing clamping mechanism, 7—outer ring casing positioning pin, 8—inner ring casing positioning ring, 9—inner ring casing lower clamping mechanism, 10—inner ring casing upper clamping mechanism, 11—inner ring casing expansion and positioning mechanism. Detailed Implementation

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

[0031] A method for repairing cracks in the inner ring support plate of a rear casing machining assembly of an aero engine includes the following steps:

[0032] Step 1: Locate the crack in the inner ring support plate;

[0033] Visual inspection and penetrant testing were used to determine the location and size range of the crack in the inner ring support plate; in this embodiment, as... Figure 1 As shown, the inner ring housing 1 of the rear housing machining assembly is circular, the outer ring housing 2 is octagonal, and the number of support tubes 3 is eight; as Figure 2 As shown, the inner ring support plate crack 4 is mostly found in areas with high original welding stress.

[0034] Step 2: Manually use pliers to repair and polish away the cracks;

[0035] First, the calibrated inner ring support plate crack is removed by manual grinding. Grinding is carried out along the crack direction, and the grinding width and depth should be based on the standard of completely removing the crack, and it is necessary to avoid grinding beyond the range until a weld is formed. Then, the surface of the bevel at the weld joint and both sides of the bevel is cleaned to remove the oxide layer, and the oxide layer removal range should not be less than 10mm. After that, the surface where the oxide layer has been removed is wiped clean, and finally the ground area is subjected to fluorescent inspection to ensure that there are no crack residues.

[0036] Step 3: Repair the ground weld by welding;

[0037] First, the rear casing machining components are rigidly fixed as a whole using welding fixtures. Then, the ground weld is repaired by manual argon arc welding. During the repair welding, welding should start from the middle of the weld and continue until both ends of the weld. The welding time should not exceed 1 minute. Welding can only continue after the weld has cooled to room temperature. The welding parameters are as follows: welding current 80A~140A, time interval 140ms~160ms, argon gas flow rate of welding torch 8L / min~12L / min, back shielding gas flow rate 6L / min~10L / min, welding wire diameter 0.8mm~1.6mm, welding wire type HGH4169, tungsten electrode diameter Ф2.0mm, tungsten electrode type WCe20.

[0038] Among them, such as Figure 3 , Figure 4As shown, the welding fixture includes a support base 5, an outer ring housing clamping mechanism 6, an outer ring housing positioning pin 7, an inner ring housing positioning ring 8, an inner ring housing lower clamping mechanism 9, an inner ring housing upper clamping mechanism 10, and an inner ring housing expansion and positioning mechanism 11; the support base 5 is disc-shaped; the number of outer ring housing clamping mechanisms 6 is several, and the number of outer ring housing clamping mechanisms 6 is evenly distributed along the circumference of the support base 5; the number of outer ring housing positioning pins 7 is several, and the number of outer ring housing positioning pins 7 is evenly distributed along the circumference of the support base 5, and the outer ring housing positioning pins... The inner ring housing positioning pins 7 and outer ring housing positioning pins 7 are staggered; the inner ring housing expansion and positioning mechanism 11 is located at the center of the support base 5; there are several inner ring housing lower pressing mechanisms 9, and several inner ring housing lower pressing mechanisms 9 are located on the expansion and positioning blocks of the inner ring housing expansion and positioning mechanism 11; the inner ring housing positioning ring 8 is coaxially arranged on the outside of the inner ring housing expansion and positioning mechanism 11, and the pressure plate of the inner ring housing lower pressing mechanism 9 is located above the inner ring housing positioning ring 8; the inner ring housing upper pressing mechanism 10 is located above the inner ring housing lower pressing mechanism 9;

[0039] In this embodiment, there are sixteen outer ring casing clamping mechanisms 6 and eight outer ring casing positioning pins 7. The lower mounting edge of the outer ring casing 2 of the rear casing processing assembly is positioned by the outer ring casing positioning pins 7 and is simultaneously clamped and fixed to the upper surface of the support base 5 by the pressure plate of the outer ring casing clamping mechanism 6. The lower mounting edge of the inner ring casing 1 of the rear casing processing assembly is positioned by the inner ring casing positioning ring 8. The four expansion positioning blocks of the inner ring casing expansion positioning mechanism 11 simultaneously expand and fix the inner ring casing 1 in the radial direction, while the inner ring casing on the expansion positioning blocks is pressed down. The clamping plate of the clamping mechanism 9 clamps and fixes the lower mounting edge of the inner ring housing 1 to the upper surface of the inner ring housing positioning ring 8; the annular clamping plate of the clamping mechanism 10 on the inner ring housing is located above the inner ring housing 1, and eight long bolts are provided between the annular clamping plate and the inner ring housing positioning ring 8. Eight hook-shaped clamping bolts are evenly arranged along the circumferential direction on the annular clamping plate, and the mounting edge of the inner ring housing 1 is clamped to the lower surface of the annular clamping plate by the hook-shaped clamping bolts; after the rear housing processing assembly is rigidly fixed and clamped in the welding fixture, the welding deformation of the rear housing processing assembly can be effectively controlled;

[0040] Step 4: Polish and refine the repair weld;

[0041] First, the excess height of the repair weld is removed by mechanical grinding. Then, the repair weld with the excess height removed is partially polished, requiring a smooth transition between the polished part and the unpolished base material until the surface finish meets the design requirements of the drawings.

[0042] Step 5: Conduct post-weld inspection of the repair weld;

[0043] ① Visual inspection: The repaired weld and its junction with the base material after polishing and finishing are visually inspected using a 10x magnifying glass. The surface must be free of cracks, incomplete fusion, incomplete penetration, and undercut defects. Surface porosity or inclusions are allowed on 100mm welds, but the maximum size of porosity or inclusions must not exceed 1mm, and the number of defects must not exceed 2. The minimum distance between defects must not be less than 2mm. If the visual inspection requirements are not met, repair welding is allowed to eliminate the defects.

[0044] ② Fluorescent Inspection: Fluorescent inspection shall be carried out on the repaired weld and the transition area between the weld and the base material after polishing and finishing. The surface shall be free of cracks and defects. Surface porosity or inclusions are allowed on 100mm welds, but the maximum size of the porosity or inclusion shall not exceed 1mm. Surface porosity and inclusions smaller than 0.5mm shall not be counted. The number of defects shall not exceed 2, and the minimum distance between defects shall not be less than 2mm. If the fluorescent inspection requirements are not met, the defects may be repaired by welding to eliminate the defects, but the number of repairs for the same defect shall not exceed 2.

[0045] ③ X-ray inspection: X-ray inspection shall be performed on the repaired weld seams and the transition areas with the base material after polishing and finishing. The surface must be free of cracks and incomplete penetration defects. Surface porosity or inclusions are permitted on 100mm weld seams, but the maximum size of any porosity or inclusion must not exceed 1.3mm, and the number of defects must not exceed 4. The minimum distance between defects must be no less than twice the maximum size of the defect, and the total defect area must not exceed 12mm². 2 If the X-ray inspection requirements are not met, welding repair is permitted to eliminate the defect, but the same defect must not be repaired more than twice.

[0046] Step Six: Perform post-weld aging heat treatment on the machined components of the rear casing;

[0047] After the weld repair and inspection are completed, the rear casing machining assembly is sent into an aging heat treatment furnace to remove residual stress. The aging heat treatment parameters are as follows: first, hold at 700℃~750℃ for 6h~10h, then furnace cool to 600℃~650℃ at a rate of 50℃ / h±10℃ / h and hold for 6h~10h, and then air cool to room temperature.

[0048] In this embodiment, the temperature is first kept at 720℃±10℃ for 8 hours, then furnace cooled to 620℃±10℃ at a rate of 50℃ / h±10℃ / h and kept at that temperature for 8 hours, and then air cooled to room temperature.

[0049] Step 7: Perform fluorescence inspection on the machining components of the rear casing;

[0050] During the fluorescent inspection of the rear casing machining components, the surface of the weld seam must be free of cracks and defects. Surface porosity or inclusions are allowed on weld seams up to 100mm in diameter, but the maximum size of the porosity or inclusion must not exceed 1mm. Surface porosity and inclusions smaller than 0.5mm are not counted. The number of defects must not exceed two, and the minimum distance between defects must not be less than 2mm. If the fluorescent inspection requirements are not met, the defects may be repaired by welding to eliminate them, but the number of times the same defect is repaired must not exceed two.

[0051] Step 8: Perform dimensional checks on the rear casing machining components;

[0052] First, measure the inner diameter of the inner ring stop of the rear housing machining assembly. Then, assemble the bearing housing into the inner ring housing of the rear housing machining assembly. After that, measure the end face runout and radial runout of the bearing housing. The measurement results must meet the design requirements of the drawings. If the measurement results do not meet the requirements, it is permissible to machine the stop of the inner ring of the housing to refine the inner diameter of the stop until the measurement results of the end face runout and radial runout of the bearing housing meet the requirements.

[0053] In this embodiment, the correction process for the end face runout and radial runout of the bearing housing is as follows: Based on the initial measured values ​​of the end face runout and radial runout of the bearing housing, the inner ring stop is machined to refine the inner diameter. Then, the locating pin on the bearing housing is removed to release the positioning between the bearing housing and the inner ring housing. The end face runout and radial runout of the bearing housing are then finely adjusted. Afterward, the positioning relationship between the bearing housing and the inner ring housing is repositioned. The locating hole is then drilled and reamed using a combined reaming method. Finally, the locating pin is reinstalled in the drilled and reamed locating hole. After the above correction process, the end face runout and radial runout of the bearing housing are measured again, and the measurement results all meet the requirements.

[0054] The solutions in the embodiments are not intended to limit the scope of protection of the present invention. All equivalent implementations or modifications that do not depart from the present invention are included in the scope of protection of the present invention.

Claims

1. A method for repairing cracks in the inner ring support plate of a rear casing machining assembly of an aero engine, characterized in that, Includes the following steps: Step 1: Locate the crack in the inner ring support plate; Step Two: Manual Grinding to Remove Cracks; First, use manual grinding to remove the calibrated cracks in the inner ring support plate. Grind along the crack direction, ensuring the width and depth of grinding are sufficient to completely remove the crack, and avoid grinding beyond the designated area, until a weld is formed; then clean the bevel and the surface on both sides of the weld joint to remove the oxide layer, ensuring the oxide layer removal area is no less than 10mm; wipe the cleaned surface to remove the oxide layer, and finally perform a fluorescent inspection on the ground area to ensure no crack residue remains; Step 3: Repair the ground weld; First, use welding fixtures to rigidly fix the rear casing machining components as a whole, then use manual argon arc welding to repair the ground weld; When repairing the weld, it is required to start welding from the middle of the weld and continue welding until both ends of the weld, and the welding time should not exceed 1 minute. Welding can only continue after the weld has cooled to room temperature; The welding fixture includes a support base, an outer ring casing clamping mechanism, an outer ring casing positioning pin, an inner ring casing positioning ring, an inner ring casing lower clamping mechanism, an inner ring casing upper clamping mechanism, and an inner ring casing expansion and positioning mechanism; The support base is disc-shaped; There are several outer ring casing clamping mechanisms, and several outer ring casings The clamping mechanism is evenly distributed along the circumference of the support base; the outer ring housing has a number of locating pins, which are evenly distributed along the circumference of the support base and are staggered; the inner ring housing expansion and positioning mechanism is located at the center of the support base; the inner ring housing has a number of lower clamping mechanisms, which are located on the expansion and positioning blocks of the inner ring housing expansion and positioning mechanism; the inner ring housing positioning ring is coaxially arranged on the outside of the inner ring housing expansion and positioning mechanism, and the pressure plate of the lower clamping mechanism is located above the inner ring housing positioning ring; the upper clamping mechanism is located above the lower clamping mechanism. Step 4: Polish and refine the repair weld; Step 5: Conduct post-weld inspection of the repair weld; Step Six: Perform post-weld aging heat treatment on the rear casing machining components; After the post-weld inspection of the repair welds, the entire rear casing machining components are sent into an aging heat treatment furnace to perform heat treatment to remove residual stress; The aging heat treatment parameters are: first, hold at 700℃~750℃ for 6h~10h, then furnace cool to 600℃~650℃ at a rate of 50℃ / h±10℃ / h and hold for 6h~10h, and then air cool to room temperature; Step 7: Perform fluorescent inspection on the rear casing machining components; during the fluorescent inspection of the rear casing machining components, the surface of the repair weld must be free of cracks and defects. Surface porosity or inclusions are allowed on welds up to 100mm in diameter, but the maximum size of the porosity or inclusion must not exceed 1mm, and surface porosity and inclusions smaller than 0.5mm are not counted. The number of defects must not exceed two, and the minimum distance between defects must not be less than 2mm. If the fluorescent inspection requirements are not met, repair welding is allowed to eliminate the defects, but the number of repair welding operations for the same defect must not exceed two. Step 8: Perform dimensional checks on the rear casing machining assembly; first, measure the inner diameter of the inner ring stop of the rear casing machining assembly, then assemble the bearing housing into the inner ring housing of the rear casing machining assembly, and then measure the end face runout and radial runout of the bearing housing. The measurement results must meet the design requirements of the drawings; if the measurement results do not meet the requirements, it is permissible to machine the stop of the inner ring of the housing to refine the inner diameter of the stop until the measurement results of the end face runout and radial runout of the bearing housing meet the requirements.

2. The method for repairing cracks in the inner ring support plate of the aero-engine rear casing machining assembly according to claim 1, characterized in that: In step one, visual inspection and penetrant testing are used to determine the location of the crack in the inner ring support plate and the size range of the crack.

3. The method for repairing cracks in the inner ring support plate of the aero-engine rear casing machining assembly according to claim 1, characterized in that: In step three, the welding parameters are as follows: welding current is 80A to 140A, time interval is 140ms to 160ms, argon gas flow rate of welding torch is 8L / min to 12L / min, back shielding gas flow rate is 6L / min to 10L / min, welding wire diameter is 0.8mm to 1.6mm, welding wire type is HGH4169, tungsten electrode diameter is Ф2.0mm, and tungsten electrode type is WCe20.

4. The method for repairing cracks in the inner ring support plate of the aero-engine rear casing machining assembly according to claim 1, characterized in that: In step four, the excess height of the repair weld is first removed by mechanical grinding. Then, the repair weld with the excess height removed is partially polished, requiring a smooth transition between the polished part and the unpolished base material until the surface finish meets the design requirements of the drawings.

5. The method for repairing cracks in the inner ring support plate of the aero-engine rear casing machining assembly according to claim 1, characterized in that: In step five, ① Visual inspection: A 10x magnifying glass is used to visually inspect the polished and refined weld seam and its transition area with the base material. The surface must be free of cracks, incomplete fusion, incomplete penetration, and undercut defects. Surface porosity or inclusions are permitted on a 100mm weld seam, but the maximum size of any porosity or inclusion must not exceed 1mm, and the number of defects must not exceed two. The minimum distance between defects must be no less than 2mm. If the visual inspection requirements are not met, repair welding is permitted to eliminate the defects. ② Fluorescent inspection: A fluorescent inspection is performed on the polished and refined weld seam and its transition area with the base material. The surface must be free of cracks. Surface porosity or inclusions are permitted on a 100mm weld seam, but the maximum size of any porosity or inclusion must not exceed 1mm. Surface porosity and inclusions exceeding 1mm but less than 0.5mm are not counted, and the number of defects must not exceed two, with a minimum distance of 2mm between defects. If the fluorescent inspection requirements are not met, repair welding is allowed to eliminate the defects, but the same defect must not be repaired more than twice. ③ X-ray inspection: X-ray inspection is performed on the repaired welds after polishing and the transition area with the base material. The surface must be free of cracks and incomplete penetration defects. Surface porosity or inclusions are allowed on 100mm welds, but the maximum size of the porosity or inclusion must not exceed 1.3mm, and the number of defects must not exceed four, with a minimum distance of twice the maximum defect size. The total defect area must not exceed 12mm². 2 ; If the X-ray inspection requirements are not met, repair welding is permitted to eliminate the defect, but the number of repair welding operations for the same defect shall not exceed 2.

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