A method for repairing defects of a mirror plate of a large hydroelectric generator set

Abstract

A mirror plate defect repairing method for a large hydroelectric generator set, comprising the following steps: S1. performing flaw detection on the original defect part of the mirror plate to determine the defect position; S2. cleaning the defect; S3. performing flaw detection inspection on the cleaned area; S4. performing welding repair by using laser cladding technology; S5. polishing the welding repaired part to be flat and performing dye penetrant inspection; S6. after no defect is found in the flaw detection, performing heat treatment on the cladding area by using laser to adjust the hardness of the cladding area; and S7. performing honing processing on the working surface of the mirror plate. Through the method, the parallelism and roughness quality of the mirror plate after the repairing and finishing can meet the industry standards, and the repaired mirror plate can meet the safe and stable operation requirements. The service life of the mirror plate is prolonged, and compared with directly replacing the mirror plate, the method has great advantages, the repairing period is shorter, the repairing cost is lower, and great economic benefits are brought to early power generation of the generator set.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of generator set mirror plate repair, and particularly relates to a large-scale hydroelectric generator set mirror plate defect repair method. BACKGROUND

[0002] After honing processing of a mirror plate of a certain unit of a hydroelectric power station, 13 original pore-like defects are found on the mirror surface of the mirror plate. After defect cleaning, the entire defect distribution area reaches 700mm*150mm, and the maximum pore reaches about 35mm*15mm*10mm. The welding carbon equivalent is an index for evaluating the welding performance of steel. Generally, if the carbon equivalent of a metal material is more than 0.6%, the material is extremely difficult to weld. The material of the mirror plate is 42CrMo, and the material composition is S: 0.0021, P: 0.010, C: 0.46, Cr: 1.08, Si: 0.25, Mn: 0.70 and Mo: 0.2. The welding carbon equivalent of the mirror plate reaches 0.83%, which is extremely difficult to weld. The mirror plate is the “heart” of the generator set. The mirror plate of the large-scale generator set is generally made of high-strength alloy steel with high carbon equivalent. At present, there is no precedent for welding repair of defects on the working surface of the large-scale hydroelectric generator set mirror plate with high welding carbon equivalent. Generally, the mirror plate with such pore-like defects is disposed of by scrapping. SUMMARY

[0003] The technical problem to be solved by the present application is to solve the problems in the above background, provide a large-scale hydroelectric generator set mirror plate defect repair method, and repair the defects on the working surface of the mirror plate by the method, thereby prolonging the service life of the mirror plate, having great advantages compared with directly replacing the mirror plate, having shorter repair period and lower repair cost, and bringing great economic benefits to early power generation of the unit.

[0004] In order to realize the above technical features, the purpose of the present application is realized as follows: a large-scale hydroelectric generator set mirror plate defect repair method, which comprises the following steps:

[0005] S1. performing flaw detection on the mirror plate to determine the defect position;

[0006] S2. cleaning the defects; using a straight grinder to grind the defects into a broken hole; wherein two adjacent defects are combined into one;

[0007] S3. performing flaw detection on the cleaned area, wherein if the flaw detection still has defects, the step in S2 is performed;

[0008] S4. performing welding repair by using laser cladding technology;

[0009] S5. grinding the welding repair part flat and performing dye penetrant testing; wherein if the flaw detection still has defects, the step in S2 is returned to perform.

[0010] S6. After the defect detection, the cladding area is heat treated by laser to adjust the hardness of the cladding area.

[0011] S7. The working surface of the mirror plate is honed.

[0012] Before S1, a scheme selection step is further included, and each scheme is experimented and detected; the schemes include traditional turning repair of the working surface of the mirror plate, argon arc welding repair of the working surface of the mirror plate, and laser cladding repair; wherein the working surface of the mirror plate repaired by the laser cladding technology is free of crack and pore defects, and the loss detection conforms to the relevant industry standards, and the shape size, parallelism and roughness after finishing meet the design drawing requirements.

[0013] Before S1, a pre-repair site preparation work is further included, which includes arranging the welding site, adjusting the height of the unit thrust head mirror plate, adjusting the position of the unit mirror plate welding test part, and ensuring the installation conditions of the laser welding equipment.

[0014] Before S1, a laser cladding technology parameter adjustment step is further included; the test piece is welded on site, and the test welding effect is observed to improve the machine hand motion parameters and laser power parameters, wherein for the superficial layer defects at the fusion seam position, the defect position is polished and then detected again, and if the defect is eliminated, the laser cladding arc collection position is adjusted to be within the laser cladding area.

[0015] In S1, the oil stains, scales, burrs and other impurities in the mirror plate pores are cleaned and polished until the metal luster is exposed, and PT and UT coloring detection is performed, and the defect position is marked.

[0016] In S4, the laser power is 1.4-1.5kW, the spot diameter is 2mm, the argon protection is 10L / min, the powder feeding mode is pre-powder laying, the powder laying thickness is 0.4-0.6mm each time, the mechanical hand motion speed is 0.5m / min, the two welding bead lap width is 0.8-1.2mm, the mechanical hand motion mode during welding is concentric circle, and the mirror plate body temperature before repair is not less than 10℃.

[0017] In S4, for defects with large depth, a pin is used to fill the defect, and laser cladding repair is performed on the basis of the pin; the specific method is to drill a pin hole at the defect position, then process a corresponding pin, the pin and the pin hole are interference fit, the pin is extruded into the pin hole, and laser welding is performed on the basis of the pin.

[0018] In S4, during laser cladding repair, two copper plates are placed on both sides of the defect, and the arc starting point and the arc collecting point are controlled on the two copper plates during welding.

[0019] In S6, the cladding tissue hardness is HB230~HB260 after laser tempering.

[0020] In S7, the welded mirror plate is honed by a gantry grinder, including the following steps:

[0021] S71. Before the machine tool, first adjust the horizontal level of the machine tool and the equal height pad drum;

[0022] S72. After the thrust head mirror plate is hoisted to the machine tool, the concentricity and levelness of the thrust head mirror plate are adjusted, wherein the dial gauge is arranged on the thrust head step;

[0023] S73. When the maximum runout value of the dial gauge is large, and the maximum runout value of the outer mirror surface dial gauge is small, the residual heat generated by the mirror plate repair welding has not been dissipated, and the mirror plate is deformed by heating, at this time, the mirror surface is not polished, and the mirror plate temperature is waited to drop to room temperature;

[0024] S74. After the thrust head mirror plate is cooled, the outer mirror surface flatness is measured by the dial gauge, when the maximum runout value is less than 0.03mm, and the temperature of the repair welding area is not higher than 2℃ than the un-repaired area, honing processing is carried out.

[0025] The present application has the following beneficial effects:

[0026] 1. By using the method to repair the defects of the working surface of the large unit mirror plate, the repair of the large hydroelectric generator unit mirror plate becomes possible, the parallelism and roughness quality of the mirror plate after repair finishing can meet the industry standard, and the repaired mirror plate meets the safe and stable operation requirements. The service life of the mirror plate is prolonged, compared with directly replacing the mirror plate, which has great advantages, the repair period is shorter, the repair cost is lower, and great economic benefits are brought to the early production and power generation of the unit. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The repair flowchart of the application.

[0028] Figure 2 The hardness curve after cladding of the application.

[0029] Figure 3 The mirror plate defect position diagram.

[0030] Figure 4 The state diagram when the mirror plate is repaired by laser cladding.

[0031] Figure 5 The state diagram when the mirror plate is honed.

[0032] Figure 6 The state diagram when the equal height pad drum is adjusted horizontally.

[0033] Figure 7 The state diagram for measuring the levelness of the mirror plate of the present application.

[0034] Figure 8 The front and back comparison diagram for repairing the mirror plate by using the present application. DETAILED DESCRIPTION

[0035] Reference Figure 1 A mirror plate defect repairing method for large hydroelectric generator set, comprising the following steps:

[0036] S1. Carrying out flaw detection on the mirror plate to determine the defect position;

[0037] S2. Cleaning the defect; using a straight grinder to polish the defect into a broken hole; wherein two adjacent defects are combined into one;

[0038] S3. Carrying out flaw detection on the cleaned area, wherein if the flaw detection still has defects, the steps in S2 are executed;

[0039] S4. Carrying out welding repair by using laser cladding technology; wherein an alloy powder material with the same hardness and structure as the mirror plate is selected for laser cladding welding.

[0040] S5. Polishing the welding repaired part flat and carrying out dye penetrant inspection; wherein if the flaw detection still has defects, the steps in S2 are returned to execute;

[0041] S6. After the flaw detection has no defects, carrying out heat treatment on the cladding area by using laser to adjust the hardness of the cladding area; the cladding area is subjected to hardness detection, and the difference between the actual hardness of the mirror plate base material and the hardness of the welding area is controlled within 20 HB.

[0042] S7. Carrying out honing processing on the working surface of the mirror plate; after the defect repairing treatment is completed, the mirror plate is subjected to fine grinding and honing, and after no defects are confirmed, the laser repairing equipment can be removed.

[0043] Before S1, a step of scheme selection is further included, and each scheme is subjected to experiment and detection; the schemes include traditional turning repair on the working surface of the mirror plate, argon arc welding repair on the working surface of the mirror plate, and laser cladding technology repair; wherein the working surface of the mirror plate repaired by using the laser cladding technology has no crack and pore defects, and the non-destructive flaw detection meets the relevant industry standards, and the shape size and parallelism and roughness after fine processing meet the design drawing requirements.

[0044] The mirror plate working surface adopts traditional turning experiment, each turning amount is 0.40mm, after turning, whether the pore-like defect is completely eliminated is observed, if not, continue to turn. After 5 times of turning, the mirror plate thickness is removed 1.99mm, but through observation, the mirror plate working surface defect is still not eliminated, some defects have the trend of expansion and new defects are added. It is analyzed that there are more pore-like defects in the mirror plate, the defect source is the mirror plate casting defect, it is difficult to completely remove the mirror plate defect by continuing turning, and at this time, if the mirror plate is continuously turned, the mirror plate thickness cannot guarantee the safe operation of the unit, which brings difficulty to the unit reloading.

[0045] The manual argon arc welding technology is used for repairing the mirror plate working surface defect, more than 40 times of welding experiment are carried out on the test piece, the welding conditions are changed by controlling the welding material, welding current and preheating temperature. The test result of each time appears cracks in different degrees, and the hardness of the welding area is greatly different from that of the base material, and the welding quality cannot be guaranteed.

[0046] The laser cladding technology is used for repairing test on the test piece of the same material, the result is shown in Figure 2 , which shows that the laser cladding technology has feasibility in repairing the mirror plate working surface defect.

[0047] The main equipment of the laser cladding experiment is the mechanical hand with the model FANUC Robot M-710iC / 70 produced by Fanuc Company, which is matched with the fiber laser with the model YLS-600-ECO produced by IPG Company, the maximum output power of the laser is 6000W, the adjustable range of the power is 10%-100%, and the cladding powder material is 42CrMo.

[0048] Before S1, it also includes the on-site preparation work before repairing, which includes arranging the welding site, adjusting the height of the unit thrust head mirror plate, adjusting the position of the unit mirror plate test welding part, and ensuring the installation conditions of the laser welding equipment.

[0049] Before S1, it also includes the step of adjusting the laser cladding technology parameters; the test piece is tested on site, the test welding effect is observed, the motion parameters of the machine hand and the laser power parameters are improved, and the superficial layer defects at the fusion seam position are polished and then re-inspected by flaw detection, if the defects are eliminated, the laser cladding arc collection position is adjusted to be in the laser cladding area.

[0050] In S1, referring to Figure 3 , the oil stains, scales, burrs and other impurities in the mirror plate pores are cleaned and polished smooth until the metal luster is exposed, PT and UT coloring flaw detection are used, and the defect position is marked.

[0051] In S4, specifically, referring to Figure 4, laser power 1.5kW; spot diameter 2mm; argon protection 10L / min; considering the weldability of the mirror plate base material, the pre-positioned powder feeding mode is adopted to obtain a thinner powder feeding thickness, reduce the probability of defects in the cladding area, and the powder feeding thickness is about 0.5mm each time; the mechanical hand movement speed is 0.5m / min; the two-weld overlapping width is about 1mm; the movement mode of the mechanical hand during welding is concentric circle, which reduces the probability of defects at the arc receiving position during welding; before repair, it is confirmed that the workshop temperature cannot be too low, and the temperature of the mirror plate body is not lower than 10℃.

[0052] In S4, for defects with large depth, a pin is used to fill the defect, and laser cladding repair is performed on the basis of the pin; the specific method is to drill a pin hole at the defect position, then process a corresponding pin, the pin and the pin hole are in interference fit, the pin is hammered into place using a hammer, and laser welding is performed on the basis of the pin.

[0053] To verify the feasibility of the method, a ∅5mm pin hole is drilled on the test piece on site, then a ∅5.2mm pin is processed, ensuring that the pin and the pin hole are in interference fit, the pin is hammered into place using a hammer, and laser welding is performed on the basis of the pin. After welding, PT detection is performed, and no defects are found. The test piece is extruded from the side using a 20T pressure, and after extrusion, PT detection is performed on the surface of the cladding area, and it is found that no cracks appear in the cladding area.

[0054] In S4, during laser cladding repair, two copper plates are placed on both sides of the defect, and the arc starting point and the arc receiving point are controlled on the two copper plates during welding. Improve the welding quality and prevent new defects on the mirror plate at the arc starting point and the arc receiving point.

[0055] In S6, the hardness of the cladding structure is HB230~HB260 after laser tempering.

[0056] In S7, referring to Figure 5 , a gantry grinding machine is used to hone the welded mirror plate, including the following steps:

[0057] S71. Referring to Figure 6 , before loading the machine, first adjust the level of the equal-height cushion cylinder; install and fix the equal-height cushion cylinder to the workbench of the machine, and grind the upper end face of the equal-height cushion cylinder through the machine to make the upper surface of the equal-height cushion cylinder consistent in height.

[0058] S72. Referring to Figure 7 , after the thrust head mirror plate is hung on the machine, adjust the concentricity and levelness of the thrust head mirror plate, the magnetic seat of the dial gauge is adsorbed on the work head of the machine, and the dial gauge is abutted on the outer circular step of the thrust head.

[0059] S73. When the maximum runout value of the dial gauge is large, and the maximum runout value of the outer mirror surface dial gauge is small, the residual heat generated by the repair welding of the mirror plate has not dissipated, causing the mirror plate to be deformed by heat. At this time, the mirror surface is not polished, and the mirror plate is allowed to cool to room temperature.

[0060] S74. After the thrust head mirror plate is cooled, the outer mirror surface flatness is measured using a dial gauge. When the maximum runout value is less than 0.03 mm, and the temperature of the repair welding area is not higher than 2℃ than the un-repaired area, honing processing is performed.

[0061] Through the use of this method to test repair the defects of the working surface of the mirror plate of a large unit, the parallelism and roughness of the repaired mirror plate can meet the industry standards. The repaired mirror plate meets the requirements of safe and stable operation, prolongs the service life of the mirror plate, and has great advantages compared to directly replacing the mirror plate. The repair period is shorter, the repair cost is lower, and the early production of the unit brings great economic benefits.

[0062] Figure 8 Fig. a is the state before repair, and Fig. b is the state after repair.

[0063] Economic benefit explanation and calculation basis: The repair cost of the mirror plate using laser cladding is about 595,000 yuan. The cost of purchasing a new mirror plate (blank cost 1.7 million yuan, processing cost 1.3 million yuan) is about 3 million yuan. The additional profit is 170+130-59.5-240.5 million yuan. In addition, the new mirror plate has a procurement cycle of 6 months and a processing period of 1 month. The old mirror plate repair period is considered to be 1 month, which can save 6 months of construction period. A 700 MW large unit of a power plant can avoid a direct power generation loss of 70 million kWh x 24 hours x 30 days x 0.25 yuan / kWh = 126 million yuan by considering early power generation for 1 month.

Claims

1. A method for repairing a mirror plate defect of a large hydroelectric generator set, characterized by, It comprises the following steps: S1. Defect position is determined by flaw detection on the mirror plate; S2. Defects are cleaned; defects are polished into a groove by a straight grinder; wherein, two adjacent defects are combined into one; S3. The cleaned area is inspected by flaw detection; wherein, if the flaw detection still has defects, the steps in S2 are executed; S4. Laser cladding technology is used for welding repair; S5. The welding repaired part is polished flat, and color flaw detection is performed; wherein, if the flaw detection still has defects, the steps in S2 are returned to execute; S6. After the flaw detection has no defects, the cladding area is heat treated by laser to adjust the hardness of the cladding area; S7. The working surface of the mirror plate is honed; In S1, the oil stains, scales, burrs and other impurities in the pores of the mirror plate are cleaned and polished smooth until the metal luster is exposed, PT and UT color flaw detection is performed, and the defect position is marked; In S4, the laser power is 1.4~1.5kW, the spot diameter is 2mm, the argon protection is 10L / min, the powder feeding mode is pre-powder laying, the powder laying thickness is 0.4~0.6mm each time, the mechanical hand movement speed is 0.5m / min, the two welding bead overlapping width is 0.8~1.2mm, the movement mode of the mechanical hand during welding is concentric circle, the mirror plate body temperature before repair is not lower than 10℃; the cladding powder material is 42CrMo; For defects with large depth, a pin is used to fill the defect, and laser cladding repair is performed on the basis of the pin; the specific method is to drill a pin hole at the defect position, then process a corresponding pin, the pin and the pin hole are in interference fit, the pin is extruded into the pin hole, and laser welding is performed on the basis of the pin; When laser cladding repair is performed, two copper plates are placed on both sides of the defect, and the arc starting point and the arc ending point are controlled on the two copper plates during welding; In S6, the cladding organization hardness is HB230~HB260 after laser tempering; In S7, the honing of the mirror plate is performed by using a gantry grinder, comprising the following steps: S71. Before the machine is put on, the machine is first adjusted to be level with the equal height pad cylinder; S72. After the thrust head mirror plate is hung on the machine, the concentricity and levelness of the thrust head mirror plate are adjusted, wherein the dial indicator is set on the thrust head step; S73. When the maximum runout value of the dial indicator is large, and the maximum runout value of the dial indicator on the outside mirror surface is small, the residual heat generated by the repair welding of the mirror plate has not been dissipated, causing the mirror plate to be deformed by heat, at this time, the mirror surface is not polished, and the mirror plate temperature is waited to drop to room temperature; S74. After the thrust head mirror plate is cooled, the outer mirror surface flatness is measured by using the dial indicator, when the maximum runout value is less than 0.03mm, and the temperature of the repair welding area is not higher than 2℃ than the un-repaired area, the grinding processing is performed.

2. A method for repairing a mirror plate defect of a large hydroelectric generator set according to claim 1, characterized in that, Before S1, a step of scheme selection is further included, and experiments and detections are performed on each scheme; the schemes include traditional turning repair on the mirror plate working surface, argon arc welding repair on the mirror plate working surface, and laser cladding technology repair; wherein the mirror plate working surface repaired by the laser cladding technology has no crack and pore defects, and the non-destructive detection conforms to the relevant industry standards, and the shape size, parallelism and roughness after finishing meet the requirements of the design drawings.

3. The method for repairing the mirror plate defect of a large hydroelectric generator set according to claim 1, characterized in that, Before S1, a step of on-site preparation before repair is further included, which includes arranging the welding site, adjusting the height of the unit thrust head mirror plate, adjusting the position of the unit mirror plate welding test part, and ensuring the installation conditions of the laser welding equipment.

4. The method for repairing the mirror plate defect of a large hydroelectric generator set according to claim 1, characterized in that, Before S1, a step of adjusting the laser cladding technology parameters is further included; the test piece is welded on site, and the machine hand motion parameters and laser power parameters are improved by observing the welding effect, wherein for the superficial layer defects at the fusion seam position, the defect position is polished and then re-inspected, and if the defect is eliminated, the laser cladding arc collection position is adjusted to be in the laser cladding area.

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