Nuclear turbine blade damage repairing method

Abstract

The invention belongs to the technical field of nuclear turbine blade repairing, and particularly relates to a nuclear turbine blade damage repairing method which comprises the steps that firstly, a repairing material is selected; secondly, a tool clamp is used for clamping the damaged blade; 3, industrial CT flaw detection is conducted on the blade repairing area; 4, judging the type of the damaged area, and removing the damaged area of the blade; 5, a repairing method, a repairing path and a repairing strategy are selected, and damage repairing is conducted; 6, the repairing effect and the stress generation condition in the repairing process are judged, and the local deformation degree is determined; step 7, carrying out industrial CT secondary flaw detection on the blade repair area; and eighthly, the repaired blade is subjected to aftertreatment. According to the method, the damaged part of the blade can be rapidly and effectively repaired, so that the service performance of the blade is recovered, and the service life is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of nuclear power steam turbine blade repair, and in particular relates to a method for repairing nuclear power steam turbine blade damage. Background Art

[0002] Nuclear power steam turbines are important components of the power module of nuclear power units, and blades are key components that affect the thermal efficiency of nuclear power steam turbines. Nuclear power steam turbine blades are usually made of high-temperature alloys, which have good high-temperature mechanical properties, high-temperature oxidation corrosion resistance, and excellent fatigue resistance, creep resistance, and fracture resistance, thus ensuring the long-term stable operation of the blades. However, due to the complex and harsh internal working environment of nuclear power steam turbines, the blades are frequently subjected to wear, impact, high-temperature gas corrosion, and hot and cold fatigue, which are prone to defects such as pitting corrosion, local cracking and defects, which seriously affect the safe and stable operation of nuclear power steam turbines.

[0003] The blade repair of nuclear power steam turbines can significantly improve the operating efficiency and stability of nuclear power steam turbines, and can greatly reduce operating costs. It is a common technical path for key equipment protection. Usually, the blade repair of nuclear power steam turbines adopts surfacing technology, that is, surfacing repair materials on the damaged area, and then using mechanical processing to remove the excess repair material to complete the repair. However, due to the large heat input in the surfacing process, it will cause obvious deformation, coarse structure, rough surface and other problems. At the same time, due to the large number of alloying elements in high-temperature alloys and the large proportion of precipitated phases, thermal cracks are easily generated in welds and heat-affected zones, making repair difficult. On the other hand, in traditional repairs, the application of nondestructive testing technology before and after repair is seldom used, and it is difficult to ensure that blade defects are completely removed during the mechanical processing process, and to clarify the existence of defects after repair, resulting in doubts about the reliability of the blade after repair.

[0004] Therefore, it is urgent to form a new set of nuclear power turbine blade repair methods through the update and mutual combination of flaw detection, machining, repair technology and post-processing technology. Summary of the invention

[0005] The object of the present invention is to provide a method for repairing damaged nuclear power steam turbine blades, which method can quickly and effectively repair the damaged parts of the blades, thereby restoring their service performance and extending their service life.

[0006] The technical solution to achieve the purpose of the present invention is:

[0007] A method for repairing damaged nuclear power steam turbine blades, the method comprising:

[0008] Step 1: Select the repair material according to the material characteristics used in the manufacture of nuclear power steam turbine blades and the service environment requirements of nuclear power steam turbines;

[0009] Step 2: Use a fixture to clamp the damaged blade to achieve deformation restraint when the nuclear power steam turbine blade is subjected to force in multiple directions, so as to avoid obvious deformation of the blade during the force process;

[0010] Step 3: Use industrial CT to perform 3D flaw detection on the damaged nuclear power turbine blades, determine the damage location, type and geometric features, build a 3D digital model of the damaged blades, and form damage feature points of the 3D digital model;

[0011] Step 4: Combine the 3D digital model of the damaged area to determine the type of the damaged area, and determine the removal path, machining allowance and geometric dimensions of the area to be repaired after machining based on the geometric characteristics of the damaged area, and remove the damaged area of ​​the blade by mechanical machining;

[0012] Step 5: Select the repair method, repair path and repair strategy according to the geometric size characteristics of the area to be repaired to repair the damage; use preheating and continuous insulation process to control the internal stress formed during the repair process;

[0013] Step 6: By calibrating the dimensions of the blade damage repair area and the adjacent area, the repair effect of the repair method, repair path and repair strategy and the stress generated during the repair process are judged, and the local deformation degree of the blade before and after the repair is determined by measuring the relative position and angle data between the clamping point of the tooling fixture on the blade and the damage feature point of the three-dimensional digital model;

[0014] Step 7: Use industrial CT to perform 3D flaw detection on the repaired area of ​​the nuclear power turbine blade again to determine the defects in the repaired area of ​​the blade; if the damaged area has been repaired, proceed to step 8; if there are still unrepaired areas or new defects in the damaged area, it is necessary to start again from step 4;

[0015] Step 8: Post-process the repaired blades.

[0016] In the step 1, the selected repair material is a cobalt-based alloy powder mixed with a single or multiple particle reinforcement phase of TiN, TiC, WC, BN, and the particle size range is 10 to 180 μm.

[0017] In the step 2, the fixture clamping methods used include fixed position clamping and adjustable position clamping, the fixed clamping positions are 1 to 3, and the adjustable clamping positions are 3 to 8.

[0018] In the step three, constructing a three-dimensional digital model of the damaged blade includes: a complete three-dimensional digital model of the damaged blade, a three-dimensional digital model of a single or multiple damaged areas, and detecting the location and shape of damage on the blade.

[0019] In the steps 3 and 7, the industrial CT operating parameters used are: tube voltage 60-90 kV, tube current 70-85 μA, and scanning sampling time 80-120 min.

[0020] In the step 4, the types of damaged areas include: cracks, defects, and pitting corrosion.

[0021] In the step 4, the cracks are removed by means of round-bottom grooves, the depth of which is uniformly greater than 10% to 15% of the crack depth, the groove angle is ≥ 90°, the blade defects are initially prepared by surface grinding, and alcohol cleaning is used to remove dust and dirt when necessary to provide a clean surface for subsequent repairs, and the pitting is removed by means of an open cone.

[0022] In the step five, the laser cladding method is selected as the repair method, the tooling fixture for clamping the damaged blade is placed on the equipment platform, the area to be repaired is located using the feature points of the three-dimensional digital model, and the repair is performed using a manipulator to move the laser head.

[0023] In the step 5, the repair parameters are: laser power is 1500-3000w, scanning rate is 2-20mm / s, spot diameter is 2-6mm, powder feeding rate is 0.2-2r / min, and overlap rate is 20%-60%.

[0024] In the step nine, the post-processing includes: removing the excess on the surface of the repair area by sandblasting, mechanical processing, etc., and performing appearance contour processing and high-precision surface polishing on the repair area by mechanical processing to meet the surface contour accuracy requirements of nuclear power turbine blades; and performing internal stress relief treatment on the repair area by local or overall heat treatment so that its surface quality and performance meet the blade repair requirements before it is finally delivered for use.

[0025] The beneficial technical effects of the present invention are:

[0026] 1. In the aspect of selection of repair materials, the present invention adopts metal powder mixed with particle reinforcement phase and the application of composite material powder to enhance the comprehensive performance of the repaired part;

[0027] 2. The present invention adopts a tooling setting that combines fixed position clamping and adjustable position clamping to effectively fix deformation during the repair process and mechanical processing;

[0028] 3. The present invention uses industrial CT to identify defects and reversely generates a digital three-dimensional model of the part to be repaired, providing data reference for mechanical processing to remove defects and repair path planning. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of a nuclear power steam turbine blade clamping tooling according to an embodiment of the present invention;

[0030] Figure 2 A schematic diagram of mechanical processing of a damaged area of ​​a nuclear power steam turbine blade according to an embodiment of the present invention;

[0031] Figure 3 It is a schematic diagram of a nuclear power steam turbine blade after repair in an embodiment of the present invention.

[0032] In the figure: 1-nuclear power steam turbine blade, 2-tooling platform, 3-fixed position clamping, 4-adjustable position clamping, 5-visible crack area of ​​nuclear power steam turbine, 6-round bottom groove after removing cracks, 7-morphology after laser cladding. DETAILED DESCRIPTION

[0033] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0034] The present invention provides a method for repairing damaged nuclear power steam turbine blades, which specifically comprises the following steps:

[0035] Step 1: Select the repair material

[0036] The repair material is selected according to the material properties used in the manufacture of nuclear power turbine blades and the service environment requirements of the nuclear power turbine; the selected repair material is a cobalt-based alloy powder mixed with a single or multiple particle mixed reinforcement phase of TiN, TiC, WC, BN, and the particle size range is 10 to 180 μm.

[0037] Step 2: Use a fixture to clamp the damaged blade

[0038] Use fixtures to clamp the damaged blades to achieve deformation restraint when the nuclear power turbine blades are subjected to forces in multiple directions, thereby avoiding obvious deformation of the blades during the force-bearing process; the fixture clamping methods used include fixed position clamping and adjustable position clamping, with 1 to 3 fixed clamping positions and 3 to 8 adjustable clamping positions.

[0039] Step 3: Perform industrial CT inspection on the blade repair area

[0040] Industrial CT is used to perform three-dimensional flaw detection on damaged nuclear power turbine blades to determine the damage location, type and geometric characteristics (length, depth, size, etc.), build a three-dimensional digital model of the damaged blade (a complete three-dimensional digital model of the damaged blade, a three-dimensional digital model of a single or multiple damaged areas, detect the location of damage on the blade and the damage morphology), and form the damage feature points of the three-dimensional digital model.

[0041] Step 4: Determine the type of damaged area and remove the damaged area on the leaf

[0042] Combined with the three-dimensional digital model of the damaged area, the type of damaged area (cracks, defects, pitting) is determined, and the removal path, machining allowance and geometric dimensions of the area to be repaired after machining are determined according to the geometric characteristics of the damaged area. The damaged area of ​​the blade is removed by mechanical processing; cracks are removed by round-bottom grooves, the depth of which is uniformly greater than 10% to 15% of the crack depth, and the groove angle is ≥90°. Blade defects are initially prepared by surface grinding. If necessary, alcohol cleaning is used to remove dust and dirt to provide a clean plane for subsequent repair. Pitting is removed by open cones.

[0043] Step 5: Select the repair method, repair path and repair strategy to repair the damage

[0044] According to the geometric size characteristics of the area to be repaired, the repair method, repair path and repair strategy are selected in the chamfer, depth, length and width directions to carry out damage repair, avoid the formation of defects such as cracks and holes during the repair process, and form a dense repair layer; the repair method can select the laser cladding method, place the tooling fixture for clamping the damaged blade on the equipment platform, use the feature points of the three-dimensional digital model to locate the area to be repaired, and use the manipulator to move the laser head to carry out the repair. The repair parameters are: laser power of 1500~3000w, scanning rate of 2~20mm / s, spot diameter of 2~6mm, powder feeding amount of 0.2~2r / min, and overlap rate of 20%~60%; preheating and continuous insulation process are used to control the internal stress formed during the repair process.

[0045] Step 6: Determine the repair effect and the stress generated during the repair process, and determine the degree of local deformation

[0046] By calibrating the dimensions of the blade damage repair area and the adjacent area, the repair effect of the repair method, repair path and repair strategy and the stress generated during the repair process are judged. The local deformation degree of the blade before and after the repair is determined by measuring the relative position and angle data between the clamping point of the tooling fixture on the blade and the damage feature point of the three-dimensional digital model.

[0047] Step 7: Perform secondary flaw detection on the blade repair area using industrial CT

[0048] Use industrial CT to perform three-dimensional flaw detection on the repaired area of ​​the nuclear power turbine blade again, strengthen the process parameters of industrial CT, obtain higher resolution detection results, and judge the defects in the repaired area of ​​the blade. The operating parameters of the industrial CT used are: tube voltage 60-90kV, tube current 70-85μA, and scanning sampling time 80-120min; if the damaged area has been repaired intact, proceed to step nine; if there are still unrepaired areas or new defects in the damaged area, it is necessary to start again from step four;

[0049] Step 8: Post-processing the repaired blades

[0050] Sandblasting, mechanical processing and other methods are used to remove the excess on the surface of the repair area, and mechanical processing is used to perform appearance contour processing and high-precision surface polishing on the repair area to meet the surface contour accuracy requirements of nuclear power turbine blades; local or overall heat treatment is used to relieve internal stress in the repair area so that its surface quality and performance meet the blade repair requirements before it is finally delivered for use.

[0051] Example 1

[0052] The material of nuclear power steam turbine blades is precipitation hardening martensitic stainless steel. The damage is a visually visible crack near the blade head. The nuclear power steam turbine blades are repaired using laser cladding technology, including the following steps:

[0053] Step 1: According to the material characteristics used in the manufacture of nuclear power steam turbine blades and the service environment requirements of nuclear power steam turbines, the grade and type of materials required for repair are selected to repair the cracked area of ​​the blades and improve the overall high-temperature corrosion resistance, wear resistance and high-temperature strength of the blades. The selected material is NiCoCr alloy powder mixed with WC strengthening phase particles, with a particle size range of 40 to 180 μm;

[0054] Step 2: Use the fixture to clamp the damaged blades by designing the fixture, and implement deformation restraint on the nuclear power steam turbine blades. In order to avoid obvious deformation of the blades during the force process, the fixture clamping methods used are divided into two forms: fixed position clamping 3 and adjustable position clamping 4. There are two fixed position clamps 3, which are fixed at the root and the middle of the blade respectively, and there are four adjustable position clamps 4, which are fixed at the upper and middle part of the blade and the head of the blade respectively. The fixed position clamps 3 and the adjustable position clamps 4 are installed on the fixture platform 2, as shown in FIG. Figure 1 As shown;

[0055] Step 3: Use industrial CT to perform 3D flaw detection on the damaged nuclear power turbine blade, determine the crack location and geometric features, build a 3D digital model of the damaged blade (the overall 3D digital model of the damaged blade, the 3D digital model of the crack near the blade head), and form the 3D digital model damage feature points. The operating parameters of the industrial CT are tube voltage 70-90 kV, tube current 75-85 μA, and scanning sampling time 80 min.

[0056] Step 4: Combined with the 3D digital model of the damaged area, determine the removal path, machining allowance and geometric dimensions of the area to be repaired after machining. Remove the damaged area of ​​the blade by mechanical machining, and use round-bottom grooves to remove cracks. The depth is uniformly greater than 10% to 15% of the crack depth, and the groove angle is ≥90°. Figure 2 As shown;

[0057] Step 5: Use local preheating and continuous insulation process to control the internal stress formed during the repair process. The local preheating temperature is 150-350℃, and the continuous insulation temperature is 200-300℃. According to the geometric size characteristics of the area to be repaired, select the laser cladding method, place the fixture for clamping the damaged blade on the equipment platform, use the three-dimensional digital model feature points to locate the area to be repaired, and use the manipulator to move the laser head to perform the repair; the repair parameters are: laser power of 1500-3000w, scanning rate of 2-20mm / s, spot diameter of 2-6mm, powder feeding rate of 0.2-2r / min, and overlap rate of 20%-60%; through the selection of repair process parameters, avoid the formation of defects such as cracks and holes during the repair process, and form a dense repair layer; the repair strategy is to start the repair from the middle of the bottom round bottom, and perform the repair in the shape of a "U" until a laser cladding residual height of 1-2mm is formed, such as Figure 3 As shown;

[0058] Step 6: By calibrating the dimensions of the blade damage repair area and the adjacent area, the repair effect of the repair method, repair path and repair strategy and the stress generated during the repair process are judged, and the local deformation degree of the blade before and after the repair is determined by measuring the relative position and angle data between the clamping point of the tooling fixture on the blade and the damage feature point of the three-dimensional digital model;

[0059] Step 7: Perform secondary flaw detection on the repaired area of ​​the blade using industrial CT. The damaged area has been repaired intact, and you can proceed to step 9. Use industrial CT to perform a three-dimensional scan of the repaired area of ​​the nuclear power steam turbine blade again, strengthen the process parameters of industrial CT, obtain higher-resolution detection results, and determine the existence of defects in the repaired area of ​​the blade. The tube voltage is 78-85kV, the tube current is 76-83μA, and the scanning sampling time is 100min.

[0060] Step 8: Post-process the repaired blades, use mechanical processing to remove the excess on the surface of the repaired area, and use local heat treatment to further remove the internal stress of the repaired area. The heat treatment temperature is 150-250°C, and then the repaired area is polished with high precision to meet the surface profile accuracy requirements of nuclear power turbine blades, and finally the repaired nuclear power turbine blades are delivered and installed again.

[0061] The present invention is described in detail above with reference to the accompanying drawings and embodiments, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of ordinary technicians in the field without departing from the purpose of the present invention. The contents not described in detail in the present invention can adopt the existing technology.

Claims

1. A method for repairing damaged nuclear power turbine blades, characterized in that: The method comprises: Step 1: Select the repair material according to the material characteristics used in the manufacture of nuclear power steam turbine blades and the service environment requirements of nuclear power steam turbines; Step 2: Use a fixture to clamp the damaged blade to achieve deformation restraint when the nuclear power steam turbine blade is subjected to force in multiple directions, and avoid obvious deformation of the blade during the force process; Step 3: Use industrial CT to perform 3D flaw detection on the damaged nuclear power turbine blades, determine the damage location, type and geometric features, build a 3D digital model of the damaged blades, and form damage feature points of the 3D digital model; Step 4: Combine the 3D digital model of the damaged area to determine the type of the damaged area, and determine the removal path, machining allowance and geometric dimensions of the area to be repaired after machining based on the geometric characteristics of the damaged area, and remove the damaged area of ​​the blade by mechanical machining; Step 5: Select the repair method, repair path and repair strategy according to the geometric size characteristics of the area to be repaired to repair the damage; use preheating and continuous insulation process to control the internal stress formed during the repair process; Step 6: By calibrating the dimensions of the blade damage repair area and the adjacent area, the repair effect of the repair method, repair path and repair strategy and the stress generated during the repair process are judged, and the local deformation degree of the blade before and after the repair is determined by measuring the relative position and angle data between the clamping point of the tooling fixture on the blade and the damage feature point of the three-dimensional digital model; Step 7: Use industrial CT to perform 3D flaw detection on the repaired area of ​​the nuclear power turbine blade again to determine the defects in the repaired area of ​​the blade; if the damaged area has been repaired, proceed to step 8; if there are still unrepaired areas or new defects in the damaged area, it is necessary to start again from step 4; Step 8: Post-process the repaired blades.

2. A method for repairing damaged nuclear power turbine blades according to claim 1, characterized in that: In the step 1, the selected repair material is a cobalt-based alloy powder mixed with a single or multiple particle reinforcement phase of TiN, TiC, WC, BN, and the particle size range is 10 to 180 μm.

3. A method for repairing damaged nuclear power turbine blades according to claim 1, characterized in that: In the step 2, the fixture clamping methods used include fixed position clamping and adjustable position clamping, the fixed clamping positions are 1 to 3, and the adjustable clamping positions are 3 to 8.

4. A method for repairing damaged nuclear power steam turbine blades according to claim 1, characterized in that: In the step three, constructing a three-dimensional digital model of the damaged blade includes: a complete three-dimensional digital model of the damaged blade, a three-dimensional digital model of a single or multiple damaged areas, and detecting the location and shape of damage on the blade.

5. A method for repairing damaged nuclear power steam turbine blades according to claim 1, characterized in that: In the steps 3 and 7, the industrial CT operating parameters used are: tube voltage 60-90 kV, tube current 70-85 μA, and scanning sampling time 80-120 min.

6. A method for repairing damaged nuclear power steam turbine blades according to claim 1, characterized in that: In the step 4, the types of damaged areas include: cracks, defects, and pitting corrosion.

7. A method for repairing damaged nuclear power steam turbine blades according to claim 6, characterized in that: In the step 4, the cracks are removed by means of round-bottom grooves, the depth of which is uniformly greater than 10% to 15% of the crack depth, the groove angle is ≥ 90°, the blade defects are initially prepared by surface grinding, and alcohol cleaning is used to remove dust and dirt when necessary to provide a clean surface for subsequent repairs, and the pitting is removed by means of an open cone.

8. A method for repairing damaged nuclear power steam turbine blades according to claim 1, characterized in that: In the step five, the laser cladding method is selected as the repair method, the tooling fixture for clamping the damaged blade is placed on the equipment platform, the area to be repaired is located using the feature points of the three-dimensional digital model, and the repair is performed using a manipulator to move the laser head.

9. A method for repairing damaged nuclear power steam turbine blades according to claim 8, characterized in that: In the step 5, the repair parameters are: laser power is 1500-3000w, scanning rate is 2-20mm / s, spot diameter is 2-6mm, powder feeding rate is 0.2-2r / min, and overlap rate is 20%-60%.

10. A method for repairing damaged nuclear power steam turbine blades according to claim 1, characterized in that: In the step nine, the post-processing includes: removing the excess on the surface of the repair area by sandblasting, mechanical processing, etc., and performing appearance contour processing and high-precision surface polishing on the repair area by mechanical processing to meet the surface contour accuracy requirements of nuclear power turbine blades; and performing internal stress relief treatment on the repair area by local or overall heat treatment so that its surface quality and performance meet the blade repair requirements before it is finally delivered for use.

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