Repair method and repair system for sealing surface defects of nuclear reactor pressure vessel

Abstract

The invention provides a repairing method and a repairing system for sealing surface defects of a nuclear reactor pressure vessel, and belongs to the technical field of nuclear power maintenance. The repairing method comprises the following steps: performing defect detection on the sealing surface of the pressure vessel; performing polishing repair or welding repair by adopting a corresponding repair method according to the distribution mode, type and size of the defects, wherein the welding repair process and process parameters are determined according to the thickness of the residual anticorrosive coating at the bottom of the welding groove after the defects are removed, the finite element simulation welding temperature field and the welding effect evaluation on the test piece; and after welding, the welding repair part is ground, so that the welding repair area meets the requirements of flatness and roughness. The repairing efficiency is greatly improved, the repairing effect is guaranteed, the personnel radiation time is shortened, and the service life of the sealing surface of the pressure vessel is prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear power equipment repair, and provides a method and a system for repairing defects on a sealing surface of a nuclear reactor pressure vessel. Background Art

[0002] The nuclear reactor pressure vessel is an important equipment for the coolant pressure boundary barrier of the nuclear power primary circuit, and is characterized by high temperature, high pressure, and high radioactivity. To ensure that no radioactive material leaks during operation and pressure conditions, the sealing of the top cover and the pressure vessel cylinder is an important link in the installation and manufacturing of nuclear power reactor pressure vessels. The base material of the pressure vessel sealing flange is SA508-III low-carbon steel, and the sealing surface is austenitic stainless steel welded on SA508-III low-carbon steel, with a surface roughness of 0.8 and a flatness of 0.038 / 69.85. With the development of the nuclear power industry, the sealing surface of the pressure vessel is in contact with water for a long time, and defects such as local corrosion or pitting are inevitable. In order to ensure the performance requirements of the pressure vessel sealing surface, the defect needs to be repaired.

[0003] CN108838573BA discloses a method and system for composite repair welding of low alloy steel and stainless steel for nuclear power pressure vessels. The method aims to repair the excessive defects of the inner wall of the pressure vessel during the manufacturing process of the nuclear power pressure vessel by preheating, composite repair welding of low alloy steel and stainless steel, and post-weld heat treatment.

[0004] Nuclear power equipment is large-scale equipment, and its defects are repaired on-site, which has the problem of small repair space and radiation risk. And after actual investigation, the defects on the sealing surface of the nuclear reactor pressure vessel are diverse in form and size. During maintenance, it is impossible to meet the requirements of short maintenance period and less radiation exposure through a single surface additive manufacturing method. Summary of the invention

[0005] The purpose of the present invention is to propose a method and a system for repairing defects on the sealing surface of a nuclear reactor pressure vessel. According to the specific form and size of the defects on the sealing surface of the pressure vessel, a suitable repair method is adopted, which can not only meet the sealing requirements of the pressure vessel and extend the service life of the equipment, but also improve the repair efficiency. With the help of the repair system, the radiation exposure of personnel is reduced, and the method is suitable for repairing defects on the sealing surface of the nuclear reactor pressure vessel.

[0006] The present invention achieves the above technical objectives through the following technical means.

[0007] A method for repairing a sealing surface defect of a nuclear reactor pressure vessel comprises the following steps:

[0008] Step 1: Perform defect detection on the sealing surface of the pressure vessel, including detecting the distribution, type and size of the defects;

[0009] Step 2: Use corresponding repair methods to repair defects according to the distribution, type and size of defects;

[0010] Set the defect depth threshold for welding repair. When the defect depth is less than the defect depth threshold, polishing and grinding are used to repair the defect.

[0011] When the defect depth is greater than the defect depth threshold, welding is used to repair the defect; the welding repair process and process parameters are determined based on the thickness of the anti-corrosion layer remaining at the bottom of the welding groove after the defect is removed, the finite element simulation welding temperature field, and the welding effect evaluation on the test piece; after welding, the welding repair part is ground to make the welding repair area meet the requirements of flatness and roughness;

[0012] Step 3: After repair, use non-destructive testing technology to detect the welds in the repaired area, the flatness and roughness of the repaired area, and the sealing performance of the sealing surface after repair.

[0013] Furthermore, in step 1, the types of defects include scratches and pitting pits; the distribution of defects includes local distribution, discrete distribution and clustered distribution; the size of the defects includes the depth of the defects and the area of ​​the defect clustered distribution region.

[0014] Furthermore, in step 2, the defect depth threshold is 0.08 mm. When the defect depth is ≤ 0.08 mm, polishing is used to repair the defect; when the defect depth is greater than 0.08 mm, welding is used to repair the defect;

[0015] When repairing defects by welding, first machine the welding groove at the defect to remove the defect; when the thickness of the stainless steel anti-corrosion layer on the sealing surface - the depth of the welding groove ≥3mm, use manual welding repair; when the thickness of the stainless steel anti-corrosion layer on the sealing surface - the depth of the welding groove <3mm, use multi-layer and multi-pass tempering automatic welding repair; after welding repair, use mechanical grinding and manual polishing in turn to grind the weld surface smooth.

[0016] Furthermore, in step 2, when the remaining anti-corrosion layer thickness at the bottom of the welding groove is ≥2.5 mm, manual welding repair is adopted, and the finite element simulation is used to simulate the welding temperature field to obtain the heat-affected zone depth as the deterioration zone thickness of each layer of welding, and the deterioration zone thickness should be less than the remaining anti-corrosion layer thickness at the bottom of the welding groove;

[0017] When the remaining anti-corrosion layer thickness at the bottom of the welding groove is less than 2.5mm, multi-layer and multi-pass tempering automatic welding repair is adopted;

[0018] The welding parameters of each layer of multi-layer multi-pass tempering automatic welding are obtained by finite element simulation of the welding temperature field to obtain the depth of the heat affected zone of each layer as the thickness of the deteriorated zone of each layer of welding, and the welding process parameters of each layer are determined based on the following formula until the deteriorated zone of the last layer after welding is higher than the surface of the original base material:

[0019] After the first layer of welding, the depth of the first layer of deteriorated zone = the depth of the first layer of welding heat affected zone;

[0020] After the second layer is welded, the height of the deteriorated zone is = the depth of the first layer deteriorated zone - (the depth of the second layer deteriorated zone - the thickness of the first layer);

[0021] After the third layer is welded, the height of the deteriorated zone is = the depth of the second layer deteriorated zone - (the depth of the third layer deteriorated zone - the thickness of the first layer - the thickness of the second layer);

[0022] …

[0023] After the nth layer of welding, the lifting height of the deteriorated zone = the depth of the deteriorated zone of the n-1th layer - (the depth of the deteriorated zone of the nth layer - the thickness of the first layer - the thickness of the second layer - ... - the thickness of the n-1th layer).

[0024] Further, in step 2, the depth of the welding groove is 1.5-2 times the depth of the defect, the cross section of the welding groove of the discretely distributed defects is an arc shape, and the cross section of the welding groove of the clustered distributed defects is a rectangular groove with an arc transition at the bottom corner;

[0025] Manual welding repair is argon arc welding repair or spot welding repair; the process parameters of argon arc welding are: welding current is 100~175A, arc voltage is 8~20V, heat input is 0.75~1.32KJ / mm, and shielding gas flow is 10~20L / min;

[0026] The process parameters of multi-layer multi-pass tempering automatic welding are: current I 峰 / I 基 180~200 / 90~120A, voltage 10~15V, pulse ratio t 基 / t 峰 200 / 200ms, welding speed V 焊 120~150mm / min, wire feeding speed V 丝 500~800mm / min;

[0027] The overlap rate of multi-layer multi-pass tempering automatic welding is 50-70%, the weld pass is greater than or equal to 3, the weld width of a single weld is less than or equal to 17mm, and the welding path is S-shaped; the number of layers of multi-layer multi-pass tempering automatic welding is greater than 3;

[0028] When mechanical polishing is used to the weld residual height of 0.1mm after welding repair, manual polishing is used to grind the weld surface smooth.

[0029] Furthermore, the number of layers of multi-layer multi-pass tempering automatic welding is four layers, and the process parameters of the first layer welding are: current I 峰 / I 基 The current is 180 / 98A, the voltage is 10~15V, and the pulse ratio is t 基 / t 峰 200 / 200ms, welding speed V 焊 120~150mm / min, wire feeding speed V 丝 800mm / min;

[0030] The process parameters for the second and third layer welding are: current I 峰 / I 基 200 / 109A, voltage 10~15V, pulse ratio t 基 / t 峰 200 / 200ms, welding speed V 焊 The wire feeding speed is 120 mm / min and the wire feeding speed V 丝 600mm / min;

[0031] The process parameters for the fourth layer welding are: current I 峰 / I 基 The current is 180 / 98A, the voltage is 10~15V, and the pulse ratio is t 基 / t 峰 200 / 200ms, welding speed V 焊 The wire feeding speed is 120 mm / min and the wire feeding speed V 丝 It is 700mm / min.

[0032] Furthermore, in step 2, when the defect depth is less than 0.05mm, manual polishing is used to repair the defect; when 0.05mm≤defect depth≤0.08mm, mechanical polishing is first used to repair the defect depth to 0.03-0.05mm, and then manual polishing is used to repair the defect; both mechanical polishing and manual polishing are circumferential polishing along the sealing surface of the O-ring groove.

[0033] Furthermore, when the low-carbon steel base material has been exposed at the bottom of the welding groove, the depth of the welding groove must be greater than or equal to the thickness of the stainless steel anti-corrosion layer + the thickness of one layer of the multi-layer multi-pass tempering automatic welding process.

[0034] The present invention also provides a repair system for a defect on a sealing surface of a nuclear reactor pressure vessel, which is used in the repair method for a defect on a sealing surface of a nuclear reactor pressure vessel, comprising a walking trolley, a mechanical arm mounted on the walking trolley, a working execution mechanism detachably mounted on the mechanical arm, and a remote control module; the working execution mechanism comprises a defect detection system, a grinding system, a welding repair system, and a nondestructive testing system;

[0035] The defect detection system is used to detect the defect position and defect depth on the sealing surface of the pressure vessel; the non-destructive testing system is used to detect the welding condition of the weld repaired after repair and the surface flatness and roughness after grinding; the grinding system is used to grind the defects to be ground and / or the welding repair sites; the welding repair system is used to weld the defects; the remote control module is used to control the operation of the walking trolley, the robotic arm and the working actuators on the robotic arm.

[0036] Furthermore, the nondestructive testing system includes a surface flatness testing device and a surface roughness testing device.

[0037] Furthermore, the grinding system includes a grinding mechanism and a grinding state monitoring and control system, and the grinding mechanism is provided with a position adjustment device; the grinding state monitoring and control system controls the position adjustment device to move the grinding mechanism to the processing site according to the defects to be ground and / or the welding repair site, and monitors and controls the working parameters of the grinding mechanism according to the grinding requirements.

[0038] Furthermore, the defect detection system is an image recognition-based defect detection system or a laser scanning device.

[0039] Furthermore, the remote control module includes a remote control terminal and a camera, a communication module and a controller integrated on the walking vehicle;

[0040] The camera is used to monitor the working status of the robot arm, defect detection system, grinding system, welding repair system and non-destructive testing system in real time;

[0041] The controller is used to collect the following information in real time: the working status and working results of the remote defect detection system, grinding system, welding repair system and non-destructive testing system, the positioning information of the trolley, and the working status of the robotic arm; and to control the work of the trolley, robotic arm, defect detection system, grinding system, welding repair system and non-destructive testing system according to the control instructions of the remote control end;

[0042] The communication module is used to transmit the information collected by the controller to the remote control terminal; and transmit the control instructions of the remote control terminal to the controller.

[0043] The advantages of the present invention compared with the prior art are:

[0044] The method for repairing defects on the sealing surface of a nuclear reactor pressure vessel of the present invention determines a reasonable welding repair process for defects with a depth exceeding a defect depth threshold according to the range of the heat affected zone of welding, the distribution of the hardened structure after welding, and the remaining thickness of the anti-corrosion layer, so that the hardness value of the heat affected zone can be lower than 350HV, thereby avoiding the influence of the hardened layer of the heat affected zone of welding repair on the mechanical properties of the sealing surface; for defects with a depth not exceeding the defect depth threshold, polishing and grinding are used for repair, which greatly improves the repair efficiency; and according to the distribution, type and size of the surface defects of the sealing surface, a suitable repair method is used to repair the defects, which can not only complete the repair on site, but also shorten the repair period, reduce the radiation time of personnel, and extend the service life of the sealing surface of the pressure vessel.

[0045] The nuclear reactor pressure vessel sealing surface defect repair system of the present invention integrates a grinding system, a welding repair system and a nondestructive testing system on a traveling trolley, automatically detects defect positions and defect depths, and realizes automatic defect repair through remote control. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a flow chart of the method for repairing the sealing surface defects of a nuclear reactor pressure vessel of the present invention;

[0047] Figure 2 Schematic diagram of the effect of the number of surfacing layers on the tempering effect;

[0048] Figure 3 This is a schematic diagram of the hardness change at the corners of the welds of the first, second and third layers of multi-layer multi-pass tempering welding;

[0049] Figure 4 This is a simulation diagram of the heat affected zone of a mild steel weld using finite element simulation;

[0050] Figure 5 It is the weld excess height curve, fusion zone and deterioration zone curve of the single-pass welding experimental welding process;

[0051] Figure 6 This is a block diagram of the repair system for sealing surface defects of a nuclear reactor pressure vessel.

[0052] Figure 2 Among them, (a) is the first layer deterioration zone, (b) is the second layer tempering zone, (c) is the second layer deterioration zone, (d) is the third layer tempering zone, and (f) is the third layer deterioration zone; Figure 5 In the figure, HAZ is the heat affected zone of welding and HF is the weld leg size. DETAILED DESCRIPTION

[0053] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used in the specification of the application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0054] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0055] The technical solution of the present invention is clearly and completely described below in conjunction with the accompanying drawings and specific embodiments.

[0056] See also Figure 1 This embodiment provides a method for repairing a sealing surface defect of a nuclear reactor pressure vessel, comprising the following steps:

[0057] Step 1: Perform defect detection on the sealing surface of the pressure vessel, including detecting the distribution mode, defect type and size of the defects;

[0058] Step 2: Use corresponding repair methods to repair defects according to the distribution, type and size of defects;

[0059] Set the defect depth threshold for welding repair. When the defect depth is less than the defect depth threshold, polishing and grinding are used to repair the defect. When the defect depth is greater than or equal to the defect depth threshold, welding is used to repair the defect.

[0060] The welding repair process and process parameters are determined based on the thickness of the anti-corrosion layer remaining at the bottom of the welding groove after the defect is removed, the finite element simulation of the welding temperature field, and the evaluation of the welding effect on the test piece;

[0061] After welding, the weld repaired part is ground to make the weld repaired area meet the requirements of flatness and roughness;

[0062] Step 3: After repair, use non-destructive testing technology to detect the welds in the repaired area, the flatness and roughness of the repaired area, and the sealing performance of the sealing surface after repair.

[0063] In this embodiment, in step 1, the types of defects include scratches and pitting pits; the distribution modes of defects include local distribution, discrete distribution and clustered distribution; the size of the defect includes the depth of the defect and the area of ​​the defect clustered distribution area, the depth of the defect includes the depth of the scratch and the depth of the pitting pit, the area of ​​the defect clustered distribution area includes the area of ​​the scratch clustered distribution area and the area of ​​the pitting pit clustered distribution area, and the size of the defect is measured by a micrometer.

[0064] In this embodiment, in step 2, for scratches or pitting pits with a depth of less than 0.05 mm, P400 or finer sandpaper is used to manually polish and repair along the circumferential polishing direction of the O-ring groove sealing surface; after the defect is repaired, the depth is less than 0.06 mm, the edge slope is not greater than 1 / 100, the edge slope should be as small as possible, and the surface roughness must meet the requirement of not greater than Ra0.8.

[0065] In this embodiment, in step 2, for scratches or pitting pits with a depth of 0.05mm≤≤0.08mm, mechanical grinding is first used to grind the defect to a depth of 0.03-0.05mm, and then manual polishing is used to repair the defect to make it smooth; after the defect is repaired, the maximum depth of each 300mm area is <0.10mm, the edge slope is not greater than 1 / 100, and the surface roughness must meet the requirement of not greater than Ra0.8.

[0066] In this embodiment, in step 2, the scratches or pitting pits with a depth greater than 0.08 mm are repaired by welding using ER308L welding wire with a diameter of 1.0 mm;

[0067] When repairing defects by welding, firstly process the welding groove at the defect to remove the defect. The depth of the welding groove is 1.5-2 times of the defect depth. The cross section of the welding groove of discretely distributed defects is an arc shape; the cross section of the welding groove of clustered defects is a rectangular groove with an arc transition at the bottom corner;

[0068] When the thickness of the stainless steel anti-corrosion layer on the sealing surface - the depth of the welding groove is ≥3mm, manual argon arc welding or spot welding is used for repair; if argon arc welding is used, the process parameters of argon arc welding are: welding current is 100~175A, arc voltage is 8~20V, heat input is 0.75~1.32KJ / mm, and shielding gas flow is 10~20L / min;

[0069] When the thickness of the stainless steel anti-corrosion layer on the sealing surface minus the depth of the welding groove is less than 3mm, multi-layer multi-pass tempering automatic welding repair is adopted. The process parameters of multi-layer multi-pass tempering automatic welding are: current I 峰 / I 基 180~200 / 90~120A, voltage 10~15V, pulse ratio t 基 / t 峰200 / 200ms, welding speed V 焊 120~150mm / min, wire feeding speed V 丝 500~800mm / min;

[0070] The overlap rate of multi-layer multi-pass tempering automatic welding is 50-70%, the weld pass is greater than or equal to 3, the weld width of a single weld is less than or equal to 17mm, and the welding path is S-shaped; the number of layers of multi-layer multi-pass tempering automatic welding is greater than 3 layers.

[0071] When mechanical polishing is used to the weld height of 0.1mm after welding repair, the weld surface is polished and leveled by manual polishing; for defects with clustered distribution, the weld surface area after welding repair shall not exceed 100in 2 After repair welding, the repair welding range and nearby areas should meet the following requirements: the flatness should be less than 0.038mm / 70mm, the overall flatness of the area should be less than 0.1mm, and the surface roughness should not exceed Ra0.8.

[0072] Through the analysis of HAZ microstructures at different depths along the same path of surfacing one layer, two layers, and three layers, the relationship between the microstructure transformation of the heat-affected zone and the number of surfacing layers was obtained. As shown in Figure 2, the first layer of deterioration zone (a) within the black outline generated by the first layer of surfacing is gradually tempered from the bottom to the top under the action of the subsequent heat cycle of each layer of surfacing. After the first layer is welded, due to the tempering effect between passes and the overlap of the weld passes, except for the last weld, only about 1 / 4 of the black outline of the previous weld remains. After the second layer is welded, the second layer of deterioration zone (c) within the black outline formed after the first layer is only 1 / 4 of the outline of the head and tail, and the middle part disappears completely. After the second layer is welded, the second layer of tempering area (b) is formed. The black outline formed is the same as the first layer, but the position is closer to the fusion line. The situation after the third layer welding is the same as that after the second layer welding, the third layer tempering area (d) is formed, and 1 / 4 of the contour line of the head and tail of the second layer remains. The black contour line in the middle of the second layer becomes smaller, and the newly formed black contour line of the third layer is closer to the fusion line, leaving only a tiny third layer deterioration zone (f), that is, the deterioration zone within the black contour line continues to move upward with the increase of the number of surfacing layers, and finally the black contour line completely moves out of the heat affected zone of the parent material. Black contour lines can still be seen at the head and tail of the weld. Analysis shows that on the one hand, due to the increase in the thickness of the surfacing layer, the effect of the weld heat on the head and tail is reduced; on the other hand, due to the interlayer overlap rate, the head and tail of the weld are far away from the center of the heat source of the subsequent weld, and the tempering effect is limited, which eventually leads to the black contour deterioration zone at the end and tail remaining. It is worth noting that with the same welding process parameters, the deterioration zone after the third layer welding still falls on the low-alloy steel parent material side of the fusion line, so at least one layer of surfacing is required to achieve complete correction of the parent material deterioration zone structure.

[0073] Figure 3 The microhardness test results of the weld corners of the first, second and third layers of the multi-layer multi-pass welding tempering welding of the present invention are shown. The microhardness of the heat affected zone after welding continues to decrease with the increase of the number of surfacing layers; since the thermal cycles experienced at the two ends of the weld are weaker than those in the middle of the weld, the microhardness value changes greatly; but after the third layer of welding, the microhardness of the heat affected zone of the base material is lower than 350HV, so that the hardness requirement of less than 350 HV required by standards and regulations is met in terms of microhardness characterization.

[0074] The specific process parameters of the repair welding of the present invention are based on the method of simulating the welding temperature field by finite element simulation to evaluate the range of the heat affected zone of welding, so as to finally determine the final process parameters of the welding repair.

[0075] Specifically, the process of finite element simulation of welding temperature field is as follows:

[0076] Step 1: Establish a finite element model, including defining the unit type, inputting the material thermophysical properties, creating a geometric solid model, setting the mesh unit size and performing mesh division, and generating a finite element model; the material thermophysical properties include specific heat capacity, thermal conductivity, elastic modulus and yield stress, etc. These parameters will change with temperature. During welding, the weldment is locally heated to a very high temperature, and the temperature of the entire weldment changes dramatically; the thermophysical property data of the material to be welded at high temperature is obtained by experiments and linear interpolation methods; the model is divided by the volume sweeping mesh division method, and the minimum unit size is 2mm×2mm×2 mm;

[0077] Step 2, apply load and solve, including defining analysis type, setting welding parameters, setting boundary conditions, and solving operations; during the simulation process, the Gaussian distribution function is used to calculate the heat source distribution function of the temperature field; during the load loading process, the unit life and death technology is used to first "kill" all welds, and then "activate" and apply temperature layer by layer; using ANSYS software, the dynamic numerical simulation of the welding temperature field is performed according to the above finite element model, and the corresponding temperature field simulation results can be obtained.

[0078] Figure 4 This is a simulation diagram of the heat affected zone of a low carbon steel weld using finite element simulation in the present invention.

[0079] In this embodiment, when welding to repair defects, the welding groove is first processed at the defect to remove the defect. When the thickness of the remaining anti-corrosion layer at the bottom of the welding groove is ≥2.5mm, manual welding is used for repair. The finite element simulation is used to simulate the welding temperature field to obtain the depth of the heat-affected zone as the thickness of the deteriorated zone of each layer of welding. The thickness of the deteriorated zone should be less than the thickness of the remaining anti-corrosion layer at the bottom of the welding groove.

[0080] When the remaining anti-corrosion layer thickness at the bottom of the welding groove is less than 2.5mm, multi-layer and multi-pass tempering automatic welding repair is adopted;

[0081] The welding parameters of each layer of multi-layer multi-pass tempering automatic welding are obtained by finite element simulation of the welding temperature field to obtain the depth of the heat affected zone of each layer as the thickness of the deteriorated zone of each layer of welding, and the welding process parameters of each layer are determined based on the following formula until the deteriorated zone of the last layer after welding is higher than the surface of the original base material:

[0082] After the first layer of welding, the depth of the first layer of deteriorated zone = the depth of the first layer of welding heat affected zone;

[0083] After the second layer is welded, the height of the deteriorated zone is = the depth of the first layer deteriorated zone - (the depth of the second layer deteriorated zone - the thickness of the first layer);

[0084] After the third layer is welded, the height of the deteriorated zone is = the depth of the second layer deteriorated zone - (the depth of the third layer deteriorated zone - the thickness of the first layer - the thickness of the second layer);

[0085] …

[0086] After the nth layer of welding, the lifting height of the deteriorated zone = the depth of the deteriorated zone of the n-1th layer - (the depth of the deteriorated zone of the nth layer - the thickness of the first layer - the thickness of the second layer - ... - the thickness of the n-1th layer).

[0087] Table 1 shows the welding process parameters of the single-pass welding experiment; Figure 6 The weld excess height curve, fusion zone and degradation zone curves for the single-pass welding test welding process. Determine the welding process parameters for each layer of multi-layer multi-pass tempering automatic welding, including the following steps:

[0088] First, the weld reinforcement, fusion zone and deterioration zone of the welding process parameters in Table 1 were measured, such as Figure 5 As shown, parameter d4#800, i.e. current I 峰 / I 基 The current is 180 / 98A, the voltage is 10~15V, and the pulse ratio is t 基 / t 峰 200 / 200ms, welding speed V 焊 120~150mm / min, wire feeding speed V 丝 The heat affected zone (HAZ) of 800mm / min is the shallowest, that is, the deterioration zone within the black outline is the shallowest. When this parameter is used to weld the first layer, the deterioration zone on the parent material side is the smallest, and the depth of the deterioration zone from the parent material plane is 2.46mm. Therefore, the d4#800 parameter is determined as the first layer welding parameter of the tempering weld, and the subsequent tempering weld process test is carried out with a 60% overlap rate;

[0089] After the first layer is welded, the second layer is welded using the above process parameters. First, ABAQUS is used to analyze the temperature field of single-pass welding for parameter d2#600. The results are as follows: Figure 5As shown in the figure, the depth of the deterioration zone of parameter d2#600 is 3.08mm, and the lifting height of the deterioration zone is 0.44mm, which is calculated as: 2.46mm- (3.08mm-1.06mm), which is smaller than the effective tempering range of 5.6mm given by the temperature field analysis of parameter d2#600. Therefore, the height of the lifted deterioration zone can be effectively and completely tempered to achieve microstructure control;

[0090] Similarly, the subsequent layers are calculated. Finally, through simulation and basic test parameter calculation, it is determined that the number of layers for multi-layer multi-pass tempering automatic welding is four layers. The process parameters for the first layer welding are: current I 峰 / I 基 The current is 180 / 98A, the voltage is 10~15V, and the pulse ratio is t 基 / t 峰 200 / 200ms, welding speed V 焊 120~150mm / min, wire feeding speed V 丝 800mm / min;

[0091] The process parameters for the second and third layer welding are: current I 峰 / I 基 200 / 109A, voltage 10~15V, pulse ratio t 基 / t 峰 200 / 200ms, welding speed V 焊 The wire feeding speed is 120 mm / min and the wire feeding speed V 丝 600mm / min;

[0092] The process parameters for the fourth layer welding are: current I 峰 / I 基 The current is 180 / 98A, the voltage is 10~15V, and the pulse ratio is t 基 / t 峰 200 / 200ms, welding speed V 焊 The wire feeding speed is 120 mm / min and the wire feeding speed V 丝 It is 700mm / min.

[0093] Table 1 Welding process parameters of single-pass welding experiment

[0094] After welding on a low-carbon steel test piece using this welding process, the microhardness of each area of ​​the weld obtained was less than 350HV. This room temperature tempering welding solves the technical problem of the difficulty in heat treatment of easily quenched low-carbon alloy steel after welding under nuclear power irradiation conditions, and can achieve room temperature tempering welding repair of the sealing surface.

[0095] When the low-carbon steel base material has been exposed at the bottom of the welding groove, it is necessary to consider whether the Cr content of the welding repair layer meets the effective anti-corrosion requirements. The Cr content of one layer of surfacing using the parameters described in Table 2 is calculated based on the area method dilution rate, and the Cr content of the first layer of surfacing is less than 12wt.%. Therefore, when the process parameters of the present invention are used for multi-layer multi-pass tempering automatic welding repair, the first layer of surfacing cannot be used as the effective surfacing layer thickness. In this embodiment, when the low-carbon steel base material has been exposed at the bottom of the welding groove, the depth of the welding groove must be greater than or equal to the thickness of the stainless steel anti-corrosion layer + the thickness of one layer of surfacing in the multi-layer tempering automatic welding process.

[0096] Table 2 Relationship between dilution rate, Cr content and process parameters

[0097] See also Figure 6 , this embodiment also provides a repair system for a sealing surface defect of a nuclear reactor pressure vessel, comprising a walking trolley, a mechanical arm mounted on the walking trolley, a working execution mechanism detachably mounted on the mechanical arm, and a remote control module; the working execution mechanism comprises a defect detection system, a grinding system, a welding repair system and a nondestructive testing system;

[0098] When performing a process such as defect detection, grinding, welding repair and non-destructive testing, the corresponding work actuator is assembled on the robotic arm and carried out by the traveling trolley; the remote control module controls the operation of the traveling trolley, the robotic arm and the work actuator on the robotic arm.

[0099] In this embodiment, the nondestructive testing system includes a surface flatness detection device and a surface roughness detection device, which are used to detect the welding condition of the weld repaired by welding and the surface flatness and roughness after grinding; the surface flatness detection device and the surface roughness detection device can adopt detection devices such as flatness meter, laser scanner, surface roughness meter, etc.

[0100] In this embodiment, the grinding system includes a grinding mechanism and a grinding state monitoring and control system, and the grinding mechanism is provided with a position adjustment device; the grinding state monitoring and control system controls the position adjustment device to move the grinding mechanism to the processing site according to the defect to be ground and / or the welding repair site, and monitors and controls the working parameters of the grinding mechanism according to the grinding requirements; the work of the grinding system includes grinding repair of shallow defects, welding groove processing during welding repair of deep defects, and flattening of welding points after welding repair; the grinding mechanism is a grinding head or a milling cutter processing device; the grinding mechanism is equipped with a detection device for the grinding process, such as a high-precision hard-wired probe, a contact roughness meter and a pressure sensor.

[0101] In this embodiment, the welding repair system is used to perform welding repair on defects; the welding repair system may use an argon arc welding device, and the welding gun of the argon arc welding device may be detachably mounted on a robotic arm to perform welding repair on a specific defect location.

[0102] In this embodiment, the defect detection system is used to detect the defect position and defect depth on the sealing surface of the pressure vessel; the defect detection system can adopt a defect detection system based on image recognition, and determine the position, size and depth of pitting pits with the help of the pit position, contour and grayscale on the image of the sealing surface of the pressure vessel; the defect detection system can also use a laser scanning device to scan the sealing surface of the pressure vessel, and then draw a three-dimensional image of the sealing surface of the pressure vessel based on the scanning results, so as to obtain the position, size and depth of the pitting pits.

[0103] In this embodiment, the remote control module includes a remote control terminal and a camera, a communication module and a controller integrated on the walking vehicle;

[0104] The camera is used to monitor the working status of the robot arm, defect detection system, grinding system, welding repair system and non-destructive testing system in real time;

[0105] The controller is used to collect the following information in real time: the working status and working results of the remote defect detection system, grinding system, welding repair system and non-destructive testing system, the positioning information of the trolley, and the working status of the robotic arm; and to control the work of the trolley, robotic arm, defect detection system, grinding system, welding repair system and non-destructive testing system according to the control instructions of the remote control end;

[0106] The communication module is used to transmit the information collected by the controller to the remote control terminal; and transmit the control instructions of the remote control terminal to the controller.

[0107] The embodiments are preferred implementations of the present invention, but the present invention is not limited to the above-mentioned implementations. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essential content of the present invention belong to the protection scope of the present invention.

Claims

1. A method for repairing a sealing surface defect of a nuclear reactor pressure vessel, characterized in that: The following steps are involved: Step 1: Perform defect detection on the sealing surface of the pressure vessel, including detecting the distribution, type and size of the defects; Step 2: Use corresponding repair methods to repair defects according to the distribution, type and size of defects; Set the defect depth threshold for welding repair. When the defect depth is less than the defect depth threshold, polishing and grinding are used to repair the defect. When the defect depth is greater than the defect depth threshold, welding is used to repair the defect; the welding repair process and process parameters are determined based on the thickness of the anti-corrosion layer remaining at the bottom of the welding groove after the defect is removed, the finite element simulation welding temperature field, and the welding effect evaluation on the test piece; after welding, the welding repair part is ground to make the welding repair area meet the requirements of flatness and roughness; Step 3: After repair, use non-destructive testing technology to detect the welds in the repaired area, the flatness and roughness of the repaired area, and the sealing performance of the sealing surface after repair.

2. The method for repairing a sealing surface defect of a nuclear reactor pressure vessel according to claim 1, characterized in that: In step 1, defect types include scratches and pitting pits; defect distribution modes include local distribution, discrete distribution and clustered distribution; defect size includes defect depth and area of ​​defect clustered distribution region.

3. The method for repairing a sealing surface defect of a nuclear reactor pressure vessel according to claim 2, characterized in that: The defect depth threshold is 0.08mm. When the defect depth is ≤0.08mm, polishing and grinding are used to repair the defect. When the defect depth is greater than 0.08mm, welding is used to repair the defect. When repairing defects by welding, first machine the welding groove at the defect to remove the defect; when the thickness of the stainless steel anti-corrosion layer on the sealing surface - the depth of the welding groove ≥3mm, use manual welding repair; when the thickness of the stainless steel anti-corrosion layer on the sealing surface - the depth of the welding groove <3mm, use multi-layer and multi-pass tempering automatic welding repair; after welding repair, use mechanical grinding and manual polishing in turn to grind the weld surface smooth.

4. The method for repairing a sealing surface defect of a nuclear reactor pressure vessel according to claim 3, characterized in that: In step 2, when the remaining anti-corrosion layer thickness at the bottom of the welding groove is ≥2.5mm, manual welding repair is adopted, and the finite element simulation is used to simulate the welding temperature field to obtain the heat-affected zone depth as the deterioration zone thickness of each layer of welding. The deterioration zone thickness should be less than the remaining anti-corrosion layer thickness at the bottom of the welding groove; When the remaining anti-corrosion layer thickness at the bottom of the welding groove is less than 2.5mm, multi-layer and multi-pass tempering automatic welding repair is adopted; The welding parameters of each layer of multi-layer multi-pass tempering automatic welding are obtained by finite element simulation of the welding temperature field to obtain the depth of the heat affected zone of each layer as the thickness of the deteriorated zone of each layer of welding, and the welding process parameters of each layer are determined based on the following formula until the deteriorated zone of the last layer after welding is higher than the surface of the original base material: After the first layer of welding, the depth of the first layer of deteriorated zone = the depth of the first layer of welding heat affected zone; After the second layer is welded, the height of the deteriorated zone is = the depth of the first layer deteriorated zone - (the depth of the second layer deteriorated zone - the thickness of the first layer); After the third layer is welded, the height of the deteriorated zone is = the depth of the second layer deteriorated zone - (the depth of the third layer deteriorated zone - the thickness of the first layer - the thickness of the second layer); …… After the nth layer of welding, the lifting height of the deteriorated zone = the depth of the deteriorated zone of the n-1th layer - (the depth of the deteriorated zone of the nth layer - the thickness of the first layer - the thickness of the second layer - ... - the thickness of the n-1th layer).

5. The method for repairing a sealing surface defect of a nuclear reactor pressure vessel according to claim 3, characterized in that: In step 2, the depth of the welding groove is 1.5-2 times the depth of the defect, the cross section of the welding groove of the discretely distributed defects is an arc shape, and the cross section of the welding groove of the clustered distributed defects is a rectangular groove with an arc transition at the bottom corner; Manual welding repair is argon arc welding repair or spot welding repair; the process parameters of argon arc welding are: welding current is 100~175A, arc voltage is 8~20V, heat input is 0.75~1.32KJ / mm, and shielding gas flow is 10~20L / min; The process parameters of multi-layer multi-pass tempering automatic welding are: current I 峰 / I 基 180~200 / 90~120A, voltage 10~15V, pulse ratio t 基 / t 峰 200 / 200ms, welding speed V 焊 120~150mm / min, wire feeding speed V 丝 500~800mm / min; The overlap rate of multi-layer multi-pass tempering automatic welding is 50-70%, the weld pass is greater than or equal to 3, the weld width of a single weld is less than or equal to 17mm, and the welding path is S-shaped; the number of layers of multi-layer multi-pass tempering automatic welding is greater than 3; When mechanical polishing is used to the weld residual height of 0.1mm after welding repair, manual polishing is used to grind the weld surface smooth.

6. The method for repairing a sealing surface defect of a nuclear reactor pressure vessel according to claim 5, characterized in that: The number of layers for multi-layer multi-pass tempering automatic welding is four, and the process parameters for the first layer welding are: current I 峰 / I 基 The current is 180 / 98A, the voltage is 10~15V, and the pulse ratio is t 基 / t 峰 200 / 200ms, welding speed V 焊 120~150mm / min, wire feeding speed V 丝 800mm / min; The process parameters for the second and third layer welding are: current I 峰 / I 基 200 / 109A, voltage 10~15V, pulse ratio t 基 / t 峰 200 / 200ms, welding speed V 焊 The wire feeding speed is 120 mm / min and the wire feeding speed V 丝 600mm / min; The process parameters for the fourth layer welding are: current I 峰 / I 基 The current is 180 / 98A, the voltage is 10~15V, and the pulse ratio is t 基 / t 峰 200 / 200ms, welding speed V 焊 The wire feeding speed is 120 mm / min and the wire feeding speed V 丝 It is 700mm / min.

7. The method for repairing a sealing surface defect of a nuclear reactor pressure vessel according to claim 3, characterized in that: When the defect depth is less than 0.05mm, manual polishing is used to repair the defect; when the defect depth is 0.05mm≤defect depth≤0.08mm, mechanical polishing is first used to repair the defect depth to 0.03-0.05mm, and then manual polishing is used to repair the defect; both mechanical polishing and manual polishing are circumferential polishing along the sealing surface of the O-ring groove.

8. The method for repairing a sealing surface defect of a nuclear reactor pressure vessel according to claim 3, characterized in that: When the low-carbon steel base material is exposed at the bottom of the welding groove, the depth of the welding groove must be greater than or equal to the thickness of the stainless steel anti-corrosion layer + the thickness of one layer of the multi-layer multi-pass tempering automatic welding process.

9. A system for repairing sealing surface defects of a nuclear reactor pressure vessel, characterized in that: A method for repairing a sealing surface defect of a nuclear reactor pressure vessel as claimed in any one of claims 1 to 8, comprising a walking trolley, a mechanical arm mounted on the walking trolley, a working actuator detachably mounted on the mechanical arm, and a remote control module; the working actuator comprises a defect detection system, a grinding system, a welding repair system and a nondestructive testing system; The defect detection system is used to detect the defect position and defect depth on the sealing surface of the pressure vessel; the non-destructive testing system is used to detect the welding condition of the weld repaired after repair and the surface flatness and roughness after grinding; the grinding system is used to grind the defects to be ground and / or the welding repair sites; the welding repair system is used to weld the defects; the remote control module is used to control the operation of the walking trolley, the robotic arm and the working actuators on the robotic arm.

10. The nuclear reactor pressure vessel sealing surface defect repair system according to claim 9, characterized in that: The nondestructive testing system includes a surface flatness testing device and a surface roughness testing device; The grinding system includes a grinding mechanism and a grinding state monitoring and control system. The grinding mechanism is provided with a position adjustment device. The grinding state monitoring and control system controls the position adjustment device to move the grinding mechanism to the processing location according to the defect to be ground and / or the welding repair location, and monitors and controls the working parameters of the grinding mechanism according to the grinding requirements. The defect detection system is an image recognition-based defect detection system or a laser scanning device; The remote control module includes a remote control terminal and a camera, a communication module and a controller integrated on the walking trolley; The camera is used to monitor the working status of the robot arm, defect detection system, grinding system, welding repair system and non-destructive testing system in real time; The controller is used to collect the following information in real time: the working status and results of the remote defect detection system, grinding system, welding repair system and non-destructive testing system, the positioning information of the walking trolley, and the working status of the robotic arm; Control the operation of the traveling trolley, robotic arm, defect detection system, grinding system, welding repair system and non-destructive testing system according to the control instructions of the remote control terminal; The communication module is used to transmit the information collected by the controller to the remote control terminal; and transmit the control instructions of the remote control terminal to the controller.

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