On-site welding manufacturing method for the transition section and elbow of a steam turbine intermediate pressure cylinder

Abstract

A method for on-site welding and manufacturing of the intermediate-pressure cylinder transition section and elbow of a steam turbine belongs to the field of welding of dissimilar steel materials. It solves the problems of difficulty in on-site installation, welding and heat treatment, as well as the problem of difficulty in ensuring quality. Method: Install the lifting tooling, pre-treat the area to be welded and its vicinity, remove the internal sleeve of the valve, and seal the interior of the intermediate-pressure cylinder transition section; lift the elbow and assemble it to the designated position; cover both sides of the area to be welded with ceramic heating ropes and refractory insulation materials, and weld after preheating; perform base welding and filling welding; clean and cover the weld and its vicinity; perform heat treatment; grind the weld surface, and complete the work after the flaw detection and hardness inspection meet the requirements. The present invention solves the on-site welding and manufacturing work of the intermediate-pressure cylinder transition section and elbow weighing 8 tons and with a wall thickness of 140 mm under the conditions of a narrow on-site space, and obtains a welding joint whose various inspection indicators meet the requirements of the drawings. It ensures that the steam turbine unit of the power plant passes the supervision and inspection smoothly and starts to generate electricity smoothly according to the cycle nodes.

Description

Technical Field

[0001] The invention belongs to the field of welding of dissimilar steel materials, and in particular relates to a method for on-site welding and manufacturing a transition section and a bent pipe of an intermediate-pressure cylinder of a steam turbine. Background Art

[0002] In order to shorten the on-site installation period of the steam turbine and improve the installation accuracy and quality, the intermediate pressure cylinder rotor, partition sleeve and other internal sleeves are shipped to the power plant as a whole after the intermediate pressure cylinder is installed at the turbine manufacturer. If the welding and heat treatment of the outer elbow of the lower half of the intermediate pressure cylinder are completed at the manufacturer, the space size will exceed the transportation requirements, and the welding of the intermediate pressure cylinder transition section and the elbow must be completed at the installation site.

[0003] The intermediate-pressure cylinder transition section is made of ZG13Cr10Mo1W1VNbN (E911 for short), and the elbow is made of ZG13Cr9Mo2Co1VNbNB (CB2 for short). These two materials are new martensitic heat-resistant steels with an operating temperature exceeding 600°C. Due to the high concentration of alloying elements that increase hardenability, welding performance is poor, and the risk of cracking during on-site welding is high. Furthermore, the weld is 140mm thick, the elbow weighs 8 tons, and this weld will be made after all components, including the turbine valve casing, are fully installed and commissioned. On-site installation presents difficulties in lifting, assembly, and welding, making it difficult to ensure heat treatment quality, welding quality, and weld performance. With no prior experience in on-site welding and manufacturing for these products, the difficulties of on-site welding, heat treatment, and installation posed significant challenges to process planning and implementation.

[0004] Currently, only reports exist on the welding of E911 and CB2 steels, and no research has been conducted on the welding and heat treatment techniques between the two materials. While welding of the same material is relatively straightforward, both the selection of welding consumables and the development of heat treatment protocols are crucial for welding dissimilar steels. However, the choice of welding consumables and the choice of heat treatment processes can impact the safe and stable operation of steam turbine units. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for on-site welding and manufacturing of the transition section and elbow of the intermediate pressure cylinder of a steam turbine, thereby solving the problems of difficulty in on-site installation, welding and heat treatment and difficulty in ensuring quality.

[0006] A method for manufacturing a steam turbine intermediate pressure cylinder transition section and a bend by on-site welding is implemented by the following steps:

[0007] 1. Install the special lifting tooling on site, then pre-treat the area to be welded between the intermediate pressure cylinder transition section and the elbow and the surrounding 50mm range, then remove the assembled valve internal sleeve of the valve housing component connected to the elbow, and use thermal insulation refractory materials to seal the interior of the intermediate pressure cylinder transition section;

[0008] 2. Use on-site embedded parts, multiple hinges and the above-mentioned special lifting tooling to lift and assemble the elbow to the designated position, and adjust the assembly space position of the elbow to meet the welding and drawing design requirements;

[0009] 3. Use ceramic heating ropes and refractory insulation materials to cover both sides of the area to be welded, then use contact armored thermocouples to control the temperature, set the preheating temperature at 250-350℃, and use an infrared thermometer to measure the temperature before welding;

[0010] 4. During the above welding, 2 to 3 welders were employed to perform welding simultaneously. During the welding process, the interlayer temperature was controlled at 250 to 350°C. ER90S-G (92) welding wire was used for welding. Tungsten inert gas arc welding was used for single-sided welding and double-sided forming technology for base welding. The base thickness was 6 mm to 8 mm. Then, E9015-G (CB2) welding consumables were used for manual arc welding for filling welding.

[0011] 5. During the welding process, the weld and the surrounding 6-30mm range are treated with saw blades for slag removal, and the rest of the parts are cleaned between layers with extended rod rotary files. After welding is completed, the weld and the surrounding 200-300mm range are covered with refractory insulation materials;

[0012] 6. Heat treatment:

[0013] The interior of the elbow cavity is filled with refractory insulation material, and then temperature-controlling thermocouples and temperature-measuring thermocouples are arranged. An induction cable is wrapped around the weld and the surrounding 200-300mm range for 10-15 turns, and then a medium-frequency induction heater is used for stress relief heat treatment. The stress relief heat treatment is to keep the temperature at 580-620℃ for 1 hour, then continue to raise the temperature to 715-725℃ and keep it at that temperature for 5-6 hours.

[0014] Auxiliary heaters are used to perform auxiliary heating on the 300-500mm range on both sides of the weld, and the auxiliary heating is kept at 600-620℃ for 5-6 hours;

[0015] 7. After the above heat treatment is completed, the weld surface is polished, and then flaw detection and hardness inspection are carried out. If all meet the requirements, the on-site welding of the turbine intermediate pressure cylinder transition section and the elbow is completed.

[0016] Furthermore, the pretreatment described in step 1 is as follows: the area to be welded and the surrounding 50mm range are polished and cleaned to remove oxide scale and oil stains, and a penetrant inspection is performed to eliminate defects that affect the welding quality.

[0017] Furthermore, the special lifting tooling described in step one includes a supporting bent plate, a lifting ring, a tightening bolt and a matching nut.

[0018] Furthermore, the thermal insulation refractory materials in steps one, three and five are all aluminum silicate felt.

[0019] Furthermore, the step 2 of satisfying the welding and drawing design requirements means that the assembly space position of the elbow must meet the welding and drawing design requirements of the welding position, installation angle, misalignment and welding assembly gap; wherein the welding assembly gap is 1 to 3 mm.

[0020] Furthermore, the welding parameters in step 4 are as follows:

[0021] Tungsten Inert Gas Welding:

[0022] Welding material model: ER90S-G(92), welding material diameter: Φ2.4

[0023] Welding current: 90-160A (Φ2.4), polarity: DC positive connection

[0024] Gas flow rate: 9-14 L / min (Ar ≥ 99.99%);

[0025] Manual arc welding:

[0026] Welding material grade: E9015-G (CB2), welding material diameter: Φ3.2 and Φ4.0

[0027] Welding current: 80-130A (Φ3.2) or 130-180A (Φ4.0)

[0028] Polarity: DC reverse.

[0029] Furthermore, the base welding described in step 4: use back argon tooling to complete the argon protection work on the back of the weld and ensure the forming effect; the ensuring of the forming effect means that after the base welding is completed, the welder checks the forming condition of the back of the weld. If defects and poorly formed areas are found, they should be immediately polished and then re-welded.

[0030] Furthermore, the covering requirement in step five is to keep the temperature at 80-100° C. for 2-3 hours.

[0031] Furthermore, the specific arrangement of the temperature-controlling thermocouple and the temperature-measuring thermocouple described in step 6 is as follows:

[0032] ① Arrangement of the weld and the surrounding 6-30mm range: one temperature-controlling thermocouple is placed at the 0 o'clock and 3 o'clock positions in the center of the weld, one temperature-measuring thermocouple is placed at the 0 o'clock and 6 o'clock positions 8-12mm away from the edges of the weld on both sides, and one temperature-measuring thermocouple is placed at the 6 o'clock and 9 o'clock positions in the center of the weld; both the temperature-controlling and temperature-measuring thermocouples are weldable armored thermocouples;

[0033] ② Arrange the area within 200-300mm on both sides of the weld: arrange 1-2 temperature-controlling thermocouples at the 0 o'clock position in this area, and arrange 1 temperature-measuring thermocouple at the 12 o'clock position.

[0034] Furthermore, during the heat treatment process described in step six, the exterior of the auxiliary heater is wrapped with a refractory insulation material; the medium frequency induction heater and the elbow are isolated with a refractory insulation material with an isolation thickness of 50 to 60 mm.

[0035] Furthermore, in step six, the heating rate below 580°C is ≤60°C / h, and within the insulation temperature range of 600°C, the heating rate is ≤40°C / h, and the cooling rate is ≤60°C / h. When cooling to below 150°C, the power can be turned off and air-cooled to room temperature, and the medium-frequency induction heater, auxiliary heater and refractory insulation material can be removed.

[0036] Furthermore, the auxiliary heater in step six is ​​a track heater or a rope heater; the number of the auxiliary heaters is determined according to actual conditions.

[0037] Furthermore, the flaw detection and hardness inspection described in step seven: according to the NB / T47013 standard, magnetic particle inspection, ultrasonic inspection, and acceptance level I are respectively performed, and then the hardness inspection is performed on the weld and the surrounding 6-30mm range. Four circumferentially symmetrical positions are inspected, and the average value of three points is taken at each position. The hardness is required to be 190-270HB.

[0038] Advantages of the present invention:

[0039] 1. The present invention utilizes specialized on-site installation and lifting tooling, employing hinged lifting for elbows. Pre-embedded components and multiple hinges are used to control the position of the suspended elbow, ensuring assembly clearance and three-dimensional positioning, enabling on-site installation. Tungsten inert gas arc welding (TIG) is used for root welding and electrode fill welding, with controlled welding parameters to complete the welding process. A medium-frequency induction heater, combined with an effective internal wall filling method and heat treatment regime, ensures weld quality after heat treatment. The resulting weld structure meets the spatial positioning requirements for subsequent component installation, and the weld quality meets performance and flaw detection requirements.

[0040] 2. The present invention adopts a special lifting tool to better ensure the assembly gap, assembly space position and angle of the elbow, ensuring that the subsequent drawing requirements are met.

[0041] 3. In the present invention, for the case of wall thickness of 140mm, a saw blade is used for slag removal, and the remaining parts are cleaned between layers by using an extended rod rotary file. Then, refractory insulation materials are used to cover the weld and the surrounding 6-30mm range to avoid welding inclusions, better ensure welding quality, and improve the service life of the weld joint.

[0042] 4. This invention solved the on-site welding problem of the transition section and elbow of the intermediate pressure cylinder, which weighed 8 tons and had a wall thickness of 140 mm, in the confined space. The weld joint achieved a weld that met all inspection specifications required by the drawings. This ensured that the power plant's steam turbine units passed inspection and started generating electricity smoothly according to the cycle schedule, creating economic benefits for society.

[0043] The invention is suitable for on-site welding and manufacturing of the transition section and the elbow of the intermediate pressure cylinder of the steam turbine. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 Schematic diagram of the elbow welding structure in the embodiment;

[0045] Figure 2 This is a construction site assembly completion diagram in the embodiment;

[0046] Figure 3 This is a construction drawing of argon tungsten arc welding base welding at the construction site in the embodiment;

[0047] Figure 4 This is a construction drawing of manual arc welding filling welding at the construction site in the embodiment;

[0048] Figure 5 This is a construction drawing of heat treatment at the construction site in the embodiment. DETAILED DESCRIPTION

[0049] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

[0050] Specific embodiment 1: This embodiment is a method for on-site welding and manufacturing of a steam turbine intermediate pressure cylinder transition section and a bend pipe, which is implemented by the following steps:

[0051] 1. Install the special lifting tooling on site, then pre-treat the area to be welded between the intermediate pressure cylinder transition section and the elbow and the surrounding 50mm range, then remove the assembled valve internal sleeve of the valve housing component connected to the elbow, and use thermal insulation refractory materials to seal the interior of the intermediate pressure cylinder transition section;

[0052] 2. Use on-site embedded parts, multiple hinges and the above-mentioned special lifting tooling to lift and assemble the elbow to the designated position, and adjust the assembly space position of the elbow to meet the welding and drawing design requirements;

[0053] 3. Use ceramic heating ropes and refractory insulation materials to cover both sides of the area to be welded, then use contact armored thermocouples to control the temperature, set the preheating temperature at 250-350℃, and use an infrared thermometer to measure the temperature before welding;

[0054] 4. During the above welding, 2 to 3 welders were employed to perform welding simultaneously. During the welding process, the interlayer temperature was controlled at 250 to 350°C. ER90S-G (92) welding wire was used for welding. Tungsten inert gas arc welding was used for single-sided welding and double-sided forming technology for base welding. The base thickness was 6 mm to 8 mm. Then, E9015-G (CB2) welding consumables were used for manual arc welding for filling welding.

[0055] 5. During the welding process, the weld and the surrounding 6-30mm range are treated with saw blades for slag removal, and the rest of the parts are cleaned between layers with extended rod rotary files. After welding is completed, the weld and the surrounding 200-300mm range are covered with refractory insulation materials;

[0056] 6. Heat treatment:

[0057] The interior of the elbow cavity is filled with refractory insulation material, and then temperature-controlling thermocouples and temperature-measuring thermocouples are arranged. An induction cable is wrapped around the weld and the surrounding 200-300mm range for 10-15 turns, and then a medium-frequency induction heater is used for stress relief heat treatment. The stress relief heat treatment is to keep the temperature at 580-620℃ for 1 hour, then continue to raise the temperature to 715-725℃ and keep it at that temperature for 5-6 hours.

[0058] Auxiliary heaters are used to perform auxiliary heating on the 300-500mm range on both sides of the weld, and the auxiliary heating is kept at 600-620℃ for 5-6 hours;

[0059] 7. After the above heat treatment is completed, the weld surface is polished, and then flaw detection and hardness inspection are carried out. If all meet the requirements, the on-site welding of the turbine intermediate pressure cylinder transition section and the elbow is completed.

[0060] The function of the special lifting tooling described in step 1 of this embodiment is to ensure that the elbow weighing 8 tons and with a wall thickness of 140 mm is smoothly lifted to the installation position, and the spatial position and angle can be adjusted, and it plays a supporting and anti-deformation role in the early stage of welding.

[0061] The purpose of dismantling the assembled valve inner sleeve of the valve shell component connected to the elbow in step 1 of this embodiment is to ensure that the welder can smoothly enter the elbow to check the root forming quality after welding. Therefore, before the elbow is lifted and assembled, the assembled valve inner sleeve of the valve shell component connected to the elbow should be dismantled to ensure that the welder can smoothly enter the elbow later.

[0062] The on-site embedded parts in step 2 of this embodiment refer to embedded parts at the installation site, which are embedded at the beginning of the construction of the thermal power plant.

[0063] In step three of this embodiment, ceramic heating ropes and refractory insulation materials are used to cover the area to be welded and the surrounding 50mm range to ensure uniform preheating.

[0064] In step 4 of this embodiment, 2 to 3 welders are used to weld simultaneously because the diameter of the bent pipe is relatively large.

[0065] Specific embodiment 2: This embodiment differs from Specific embodiment 1 in that the pretreatment described in step 1 includes polishing and cleaning the area to be welded and the surrounding 50mm area to remove scale and oil, and performing penetrant testing to eliminate defects that affect weld quality. Other steps and parameters are the same as those in Specific embodiment 1.

[0066] Specific embodiment 3: This embodiment differs from specific embodiment 1 in that the lifting tooling described in step 1 includes a support bent plate, a lifting ring, a tightening bolt, and a matching nut. The other steps and parameters are the same as those in specific embodiment 1.

[0067] Specific embodiment 4: This embodiment differs from specific embodiment 1 in that the thermal insulation refractory materials in steps 1, 3, and 5 are all aluminum silicate felt. Other steps and parameters are the same as those in specific embodiment 1.

[0068] Specific Embodiment 5: This embodiment differs from Specific Embodiment 1 in that, in step 2, "meeting welding and drawing design requirements" means that the elbow's assembly space must meet the welding and drawing design requirements for welding position, installation angle, offset, and welding assembly clearance; the welding assembly clearance is 1 to 3 mm. Other steps and parameters are the same as in Specific Embodiment 1.

[0069] Specific embodiment 6: This embodiment differs from specific embodiment 1 in that the welding parameters in step 4 are as follows:

[0070] Tungsten Inert Gas Welding:

[0071] Welding material model: ER90S-G(92), welding material diameter: Φ2.4

[0072] Welding current: 90-160A (Φ2.4), polarity: DC positive connection

[0073] Gas flow rate: 9-14 L / min (Ar ≥ 99.99%);

[0074] Manual arc welding:

[0075] Welding material grade: E9015-G (CB2), welding material diameter: Φ3.2 and Φ4.0

[0076] Welding current: 80-130A (Φ3.2) or 130-180A (Φ4.0)

[0077] Polarity: DC reverse connection. Other steps and parameters are the same as those in the first embodiment.

[0078] Specific Embodiment 7: This embodiment differs from Specific Embodiment 1 in that, in step 4, the backing welding process uses an argon backing tool to protect the back of the weld with argon gas and ensure a good shaping effect. This "guaranteed shaping effect" means that after the backing welding is completed, the welder inspects the backing of the weld. Any defects or poorly formed areas are immediately polished and repaired. Other steps and parameters are the same as in Specific Embodiment 1.

[0079] Specific embodiment 8: This embodiment differs from specific embodiment 1 in that the covering requirement in step 5 is to keep the temperature at 80-100° C. for 2-3 hours. The other steps and parameters are the same as those in specific embodiment 1.

[0080] The purpose of covering in this embodiment is to ensure that the weld and the surrounding 6 to 30 mm range are kept warm and cooled slowly, so that the microstructure of the weld area is completely transformed.

[0081] Specific embodiment 9: This embodiment differs from specific embodiment 1 in that the specific arrangement of the temperature-controlling thermocouple and the temperature-measuring thermocouple in step 6 is as follows:

[0082] ① Arrangement of the weld and the surrounding 6-30mm range: one temperature-controlling thermocouple is placed at the 0 o'clock and 3 o'clock positions in the center of the weld, one temperature-measuring thermocouple is placed at the 0 o'clock and 6 o'clock positions 8-12mm away from the edges of the weld on both sides, and one temperature-measuring thermocouple is placed at the 6 o'clock and 9 o'clock positions in the center of the weld; both the temperature-controlling and temperature-measuring thermocouples are weldable armored thermocouples;

[0083] ② Arrange the area within 200-300mm on both sides of the weld: arrange 1-2 temperature-controlling thermocouples at the 0 o'clock position in this area, and arrange 1 temperature-measuring thermocouple at the 12 o'clock position.

[0084] Specific Embodiment 11: This embodiment differs from Specific Embodiment 1 in that, during the heat treatment process described in step 6, the auxiliary heater is wrapped with refractory insulation material; and the medium-frequency induction heater and the elbow are insulated with refractory insulation material with a thickness of 50-60 mm. Other steps and parameters are the same as those in Specific Embodiment 1.

[0085] The purpose of wrapping and isolating in this embodiment is to protect the air-cooling induction cable, avoid heating of the auxiliary heater air-cooling cable, and avoid damage to the air-cooling cable.

[0086] Specific embodiment 12: This embodiment differs from specific embodiment 1 in that, in step 6, the heating rate below 580°C is ≤60°C / h; within the holding temperature range from 600°C to 40°C / h, the heating rate is ≤40°C / h, and the cooling rate is ≤60°C / h. When cooling to below 150°C, the power can be turned off and air-cooled to room temperature, and the medium-frequency induction heater, auxiliary heater, and refractory insulation material are removed. Other steps and parameters are the same as those in specific embodiment 1.

[0087] Specific embodiment 13: This embodiment differs from specific embodiment 1 in that the auxiliary heater in step 6 is a track heater or a rope heater; the number of auxiliary heaters is determined according to actual conditions. The other steps and parameters are the same as those in specific embodiment 1.

[0088] Specific Embodiment 14: This embodiment differs from Specific Embodiment 1 in that the flaw detection and hardness test described in Step 7 are performed according to NB / T47013 standard, performing magnetic particle inspection and ultrasonic inspection, with acceptance level I. A hardness test is then performed on the weld and the surrounding area within 6 to 30 mm. Three points are tested at each location, averaging the required hardness of 190 to 270 HB. Other steps and parameters are the same as those in Specific Embodiment 1.

[0089] The beneficial effects of the present invention are verified by the following examples:

[0090] Example:

[0091] A method for manufacturing a steam turbine intermediate pressure cylinder transition section and a bend by on-site welding is implemented by the following steps:

[0092] 1. Install the special lifting tooling on site, then pre-treat the area to be welded between the intermediate pressure cylinder transition section and the elbow and the surrounding 50mm range, then remove the assembled valve internal sleeve of the valve housing component connected to the elbow, and use thermal insulation refractory materials to seal the interior of the intermediate pressure cylinder transition section;

[0093] 2. Use on-site embedded parts, multiple hinges and the above-mentioned special lifting tooling to lift and assemble the elbow to the designated position, and adjust the assembly space position of the elbow to meet the welding and drawing design requirements;

[0094] 3. Use ceramic heating ropes and refractory insulation materials to cover both sides of the area to be welded, and then use 4 contact armored thermocouples to control the temperature. Set the preheating temperature to 300℃, and use an infrared thermometer to measure the temperature before welding;

[0095] 4. During the above welding, 2 to 3 welders were employed to perform welding simultaneously. The interlayer temperature was controlled at 250-320°C during the welding process. ER90S-G (92) welding wire was used for welding. Tungsten inert gas arc welding was used for single-sided welding and double-sided forming technology for base welding. The base thickness was 7 mm. Then, E9015-G (CB2) welding consumables were used for manual arc welding for filling welding.

[0096] 5. During the welding process, the weld and the surrounding 6-30mm range are treated with saw blades for slag removal, and the rest of the parts are cleaned between layers with extended rod rotary files. After welding is completed, the weld and the surrounding 200-300mm range are covered with refractory insulation materials;

[0097] 6. Heat treatment:

[0098] The interior of the elbow cavity is filled with refractory insulation material, and then temperature-controlling thermocouples and temperature-measuring thermocouples are arranged. An induction cable is wrapped around the weld and the surrounding 200-300mm range for 10-15 turns, and then a medium-frequency induction heater is used for stress relief heat treatment. The stress relief heat treatment is to keep the temperature at 580-620℃ for 1 hour, and then continue to raise the temperature to 720℃ and keep it at that temperature for 5-6 hours.

[0099] Auxiliary heaters are used to perform auxiliary heating on the 300-500mm range on both sides of the weld, and the auxiliary heating is kept at 600-620℃ for 5-6 hours;

[0100] 7. After the above heat treatment is completed, the weld surface is polished, and then flaw detection and hardness inspection are carried out. If all meet the requirements, the on-site welding of the turbine intermediate pressure cylinder transition section and the elbow is completed.

[0101] The purpose of the special lifting tooling described in step 1 of this embodiment is to ensure that the elbow weighing 8 tons and with a wall thickness of 140 mm is smoothly lifted to the installation position, and the spatial position and angle can be adjusted, and it plays a supporting and anti-deformation role in the early stage of welding.

[0102] The purpose of dismantling the assembled valve inner sleeve of the valve housing component connected to the elbow in step 1 of this embodiment is to ensure that the welder can smoothly enter the elbow to check the root forming quality after welding. Therefore, before the elbow is lifted and assembled, the assembled valve inner sleeve of the valve housing component connected to the elbow should be dismantled to ensure that the welder can smoothly enter the elbow later.

[0103] The on-site embedded parts in step 2 of this embodiment refer to embedded parts at the installation site, which are embedded at the beginning of the construction of the thermal power plant.

[0104] In step three of this embodiment, ceramic heating ropes and refractory insulation materials are used to cover the area to be welded and the surrounding 50mm range to ensure uniform preheating.

[0105] In step 4 of this embodiment, 2 to 3 welders are used to weld simultaneously because the diameter of the bent pipe is relatively large.

[0106] The pretreatment described in step 1 of this embodiment includes: grinding and cleaning the area to be welded and the surrounding 50mm area to remove oxide scale and oil stains, and performing penetrant testing to eliminate defects that affect welding quality;

[0107] The special lifting tooling described in step 1 includes supporting bent plates, lifting rings, tightening bolts and matching nuts; two pairs of supporting bent plates are made of Q235A material, four lifting rings with a load-bearing capacity greater than 8 tons, a pair of tightening bolts and matching nuts are selected, and the special lifting tooling is installed on the elbow.

[0108] The thermal insulation refractory materials in steps 1, 3 and 5 are all aluminum silicate felt;

[0109] Meeting the welding and drawing design requirements in step 2 means that the assembly space position of the elbow must meet the welding and drawing design requirements of the welding position, installation angle, misalignment and welding assembly gap; the welding assembly gap is 1.5 to 2.5 mm;

[0110] The welding parameters described in step 4 are as follows:

[0111] Tungsten Inert Gas Welding:

[0112] Welding material model: ER90S-G(92), welding material diameter: Φ2.4

[0113] Welding current: 90-160A (Φ2.4), polarity: DC positive connection

[0114] Gas flow rate: 9-14 L / min (Ar ≥ 99.99%);

[0115] Manual arc welding:

[0116] Welding material grade: E9015-G (CB2), welding material diameter: Φ3.2 and Φ4.0

[0117] Welding current: 80-130A (Φ3.2) or 130-180A (Φ4.0)

[0118] Polarity: DC reverse polarity;

[0119] The base welding described in step 4: use back argon tooling to complete the argon protection work on the back of the weld and ensure the forming effect; the said ensuring the forming effect means that after the base welding is completed, the welder checks the forming condition of the back of the weld and finds a poorly formed area with a length of about 5 mm. After grinding, it is repaired according to the above welding process.

[0120] In the practical operation of step 4, two welders cooperate in the base welding, and two welders perform the filler welding at the same time;

[0121] The covering requirement in step 5 is to keep warm at 95-100℃ for 2h;

[0122] The specific arrangement of the temperature-controlling thermocouple and the temperature-measuring thermocouple described in step 6 is as follows:

[0123] ① Arrangement of the weld and the surrounding 6-30mm range: one temperature-controlling thermocouple is placed at the 0 o'clock and 3 o'clock positions in the center of the weld, one temperature-measuring thermocouple is placed at the 0 o'clock and 6 o'clock positions 8-12mm away from the edges of the weld on both sides, and one temperature-measuring thermocouple is placed at the 6 o'clock and 9 o'clock positions in the center of the weld; both the temperature-controlling and temperature-measuring thermocouples are weldable armored thermocouples;

[0124] ② Arrange the area within 200-300mm on both sides of the weld: arrange 1-2 temperature-controlling thermocouples at the 0 o'clock position in this area, and arrange 1 temperature-measuring thermocouple at the 12 o'clock position.

[0125] During the heat treatment process described in step 6, the exterior of the auxiliary heater is wrapped with refractory insulation material; the medium frequency induction heater and the elbow are isolated with refractory insulation material with an isolation thickness of 50 to 60 mm;

[0126] In step 6, the heating rate below 580°C is ≤60°C / h, and within the range of 600°C to 720°C, the heating rate is 40°C / h and the cooling rate is 40°C / h. When cooling to below 100°C, the power can be turned off and air-cooled to room temperature. The medium-frequency induction heater, auxiliary heater and refractory insulation material are removed;

[0127] The auxiliary heater in step 6 is a track heater or a rope heater; the number of the auxiliary heaters is 2, the total length is 30 meters, and the power is 30KW;

[0128] The flaw detection and hardness inspection described in step seven: According to the NB / T47013 standard, magnetic particle inspection, ultrasonic inspection and acceptance level I are carried out respectively. Then the hardness of the weld and the surrounding 6-30mm range is checked. Four circumferentially symmetrical positions are tested, and the average value of three points is taken at each position. The hardness is required to be 200-230HB. All inspections are in compliance with the requirements of the drawings, which solves the problems of difficult on-site installation, welding and heat treatment and difficult quality assurance.

[0129] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for manufacturing on-site welding of the transition section and elbow of a steam turbine intermediate pressure cylinder, characterized in that It is implemented as follows:

1. Install the special lifting tooling on site, then pre-treat the area to be welded between the intermediate pressure cylinder transition section and the elbow and the surrounding 50mm range, then remove the assembled valve internal sleeve of the valve housing component connected to the elbow, and use thermal insulation refractory materials to seal the interior of the intermediate pressure cylinder transition section; 2. Use on-site embedded parts, multiple hinges and the above-mentioned special lifting tooling to lift and assemble the elbow to the designated position, and adjust the assembly space position of the elbow to meet the welding and drawing design requirements; 3. Use ceramic heating ropes and refractory insulation materials to cover both sides of the area to be welded, then use contact armored thermocouples to control the temperature, set the preheating temperature at 250~350℃, and use an infrared thermometer to measure the temperature before welding; 4. During the above welding, 2 to 3 welders were used to perform welding simultaneously. The interlayer temperature was controlled at 250 to 350°C during the welding process. ER90S-G (92) welding wire was used for welding. Tungsten inert gas arc welding method was used for single-sided welding and double-sided forming technology for base welding. The base thickness was 6 mm to 8 mm. Then, E9015-G (CB2) welding material was used for manual arc welding for filling welding.

5. During the welding process, the weld and the surrounding 6~30mm range are treated with saw blades for slag removal, and the rest of the parts are cleaned between layers with extended rod rotary files. After welding is completed, the weld and the surrounding 200~300mm range are covered with refractory insulation materials; 6. Heat treatment: The interior of the elbow cavity is filled with refractory insulation material, and then temperature-controlling and temperature-measuring thermocouples are arranged. An induction cable is wrapped around the weld and the surrounding 200-300mm range for 10-15 turns. Then, a medium-frequency induction heater is used for stress relief heat treatment. The stress relief heat treatment is to keep the temperature at 580-620℃ for 1 hour, then continue to raise the temperature to 715-725℃ and keep it at that temperature for 5-6 hours. Auxiliary heaters are used to perform auxiliary heating on the 300-500mm range on both sides of the weld, and the auxiliary heating is kept at 600-620℃ for 5-6 hours; 7. After the above heat treatment is completed, the weld surface is polished, and then flaw detection and hardness inspection are carried out. If all meet the requirements, the on-site welding of the turbine intermediate pressure cylinder transition section and the elbow is completed; The special lifting tooling in step 1 includes a support bent plate, lifting rings, tightening bolts and matching nuts; The welding parameters described in step 4 are as follows: Tungsten Inert Gas Welding: Welding material model: ER90S-G (92), welding material diameter: Φ2.4 Welding current: 90-160A, polarity: DC positive connection Gas flow rate: 9~14L / min, Ar≥99.99%; Manual arc welding: Welding material grade: E9015-G (CB2), welding material diameter: Φ3.2 and Φ4.0 Welding current: 80-130A or 130-180A Polarity: DC reverse polarity; The specific arrangement of the temperature-controlling thermocouple and the temperature-measuring thermocouple described in step 6 is as follows: ① Arrangement of the weld and the surrounding 6~30mm range: one temperature-controlling thermocouple is placed at the 0 o'clock and 3 o'clock positions in the center of the weld, one temperature-measuring thermocouple is placed at the 0 o'clock and 6 o'clock positions 8~12mm away from the edges of the weld on both sides, and one temperature-measuring thermocouple is placed at the 6 o'clock and 9 o'clock positions in the center of the weld; both the temperature-controlling and temperature-measuring thermocouples are weldable armored thermocouples; ② Arrange the area within 200~300mm on both sides of the weld: arrange 1~2 temperature-controlling thermocouples at the 0 o'clock position in this area, and arrange 1 temperature-measuring thermocouple at the 12 o'clock position.

2. A method for manufacturing a steam turbine intermediate pressure cylinder transition section and a bend by on-site welding according to claim 1, characterized in that Pretreatment as described in step 1: Grind and clean the area to be welded and the surrounding 50mm range to remove oxide scale and oil stains, and perform penetrant testing to eliminate defects that affect welding quality.

3. The method for manufacturing the on-site welding of the intermediate pressure cylinder transition section and the elbow of a steam turbine according to claim 1, characterized in that The thermal insulation refractory materials described in steps 1, 3 and 5 are all aluminum silicate felt.

4. The method for manufacturing the on-site welding of the intermediate pressure cylinder transition section and the elbow of a steam turbine according to claim 1, characterized in that Meeting the welding and drawing design requirements as mentioned in step 2 means that the assembly space position of the elbow must meet the welding and drawing design requirements of the welding position, installation angle, misalignment and welding assembly clearance; The welding assembly gap is 1~3mm.

5. The method for manufacturing the on-site welding of the intermediate pressure cylinder transition section and the elbow of a steam turbine according to claim 1, characterized in that The backing welding described in step 4: use back argon tooling to complete the argon protection work on the back of the weld and ensure the forming effect; the said ensuring the forming effect means that after the backing welding is completed, the welder checks the forming condition of the back of the weld. If defects and poorly formed areas are found, they should be immediately polished and then repaired by welding.

6. The method for manufacturing the on-site welding of the intermediate pressure cylinder transition section and the elbow of a steam turbine according to claim 1, characterized in that During the heat treatment process described in step 6, the exterior of the auxiliary heater is wrapped with refractory insulation material; the medium frequency induction heater and the elbow are isolated with refractory insulation material with an isolation thickness of 50 to 60 mm.

7. The method for manufacturing the on-site welding of the intermediate pressure cylinder transition section and the elbow of a steam turbine according to claim 1, characterized in that In step 6, the heating rate below 580℃ is ≤60℃ / h, and within the insulation temperature range of 600℃, the heating rate is ≤40℃ / h, and the cooling rate is ≤60℃ / h. When the temperature is cooled to below 150℃, the power can be turned off and air-cooled to room temperature, and the medium-frequency induction heater, auxiliary heater and refractory insulation materials can be removed.

8. The method for manufacturing the on-site welding of the intermediate pressure cylinder transition section and the elbow of a steam turbine according to claim 1, characterized in that The flaw detection and hardness test described in step 7: According to the NB / T47013 standard, magnetic particle inspection, ultrasonic inspection and acceptance level I are carried out respectively. Then the hardness of the weld and the surrounding 6~30mm range is checked. Four circumferentially symmetrical positions are tested, and the average value of three points is taken at each position. The required hardness is 190~270HB.

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