Electromagnetic induction heating device for hardfacing inner wall of nuclear power evaporator head

Abstract

The present application relates to a kind of electromagnetic induction heating device and method for nuclear power evaporator head inner wall surfacing, belong to nuclear power equipment manufacturing field.The device includes at least two identical spherical profiling induction heater and two end face profiling induction heater, and each heater is assembled and fixed on the outer wall of the head by bolt connector, and constitutes the overall heating frame that is closely combined with the shape of the head.Each heater includes profiling frame body, heat preservation layer, induction cable and temperature measuring element.The present application is also equipped with temperature control system, according to the feedback of each area temperature measuring element, independently, dynamically adjusts the power output of corresponding induction cable.The heating method integrates preheating, surfacing process heat preservation and postweld heat treatment steps, and can be synchronized with the head rotation surfacing.The present application solves the problem of low efficiency, uneven temperature, difficult to adapt to the surface of traditional flame heating, with good temperature uniformity, high heating efficiency, strong adaptability and process quality stability and other advantages.

Description

Technical Field

[0001] This invention relates to an electromagnetic induction heating device for welding the inner wall of a nuclear power plant evaporator head, belonging to the field of nuclear power equipment manufacturing, and is used to solve the problems of temperature uniformity and efficient temperature control during welding of the inner wall of a large nuclear power plant head. Background Technology

[0002] When performing internal wall cladding welding on the heads of components such as nuclear power plant evaporators and boiler pressure vessels, preheating before welding, heat preservation during welding, and hydrogen removal after welding are required. This is because the welding process causes localized heating of the material, generating stress and deformation, and heating can help reduce thermal stress during welding while improving the quality of the weld joint.

[0003] Current heating methods include traditional gas combustion flame heating. However, when welding the inner wall of the end cap, it needs to rotate continuously along the axial direction to ensure continuous welding. Flame heating methods have problems such as slow heating speed, uneven heating, inability to accurately control temperature, low thermal efficiency, and carbon emissions.

[0004] Patent No. 201710445805.0, entitled "Method for Electromagnetic Induction Heating of the Inner Wall of a Large Head for Welding," discloses a method for electromagnetic induction heating of the inner wall of a large head for welding. Its features include: installing insulation blankets by splicing two fan-shaped insulation blankets on the outer surface of the head and connecting them into a whole with ribbons; installing hinge fixing rings by installing two semi-circular hinge fixing rings on the head protrusion; installing hinge tension bolts by installing multiple bolts and adjusting nuts on the anti-deformation ring of the head; installing hinges by connecting one end of the hinge to the adjusting nut and installing a hinge latch on the other end, connecting the hinge latch to the fixing ring, and adjusting the adjusting nut to tighten the hinge; and laying induction cables, starting from the top of the head, wrapping the cable around the outer perimeter of the head and embedding it into the hinge for fixation, and connecting the upper and lower ends of the cable to a power source for heating. This method solves the problem of low heat conversion rates associated with natural gas heating and resistance heating, and is particularly suitable for heating the inner wall of large heads for welding.

[0005] This electromagnetic induction heating method for overlaying the inner wall of large heads cannot cover the entire structure with large curvature, deep cavity and end face. The heating effect on the end face is poor. Without a temperature closed-loop control system, it cannot achieve automatic control of interlayer temperature. Without a heating zone control system, it cannot independently control the power. The installation of the heating device requires more than 8 man-hours, resulting in low installation efficiency.

[0006] Existing evaporator heads are hemispherical structures with high curvature, requiring a corrosion-resistant alloy layer to be welded onto the inner wall. Both of these heating methods have the following drawbacks: 1. Low heating efficiency and high energy loss make it impossible to meet the requirements for efficient manufacturing of nuclear power equipment.

[0007]

[0008] Therefore, it can be seen that the preheating of the end cap, using traditional flame heating methods, requires 8-10 hours and consumes approximately 1500 m³ of fuel gas (3.95 yuan / m³). 3 The energy cost is approximately 5,925 yuan. The heating speed of electromagnetic induction heating is increased to 4-6 hours, consuming approximately 960 kWh of electricity (1 yuan / kWh). The energy cost is approximately 960 yuan, the heating efficiency is increased by 50%, and the energy cost is reduced by 84%.

[0009] 2. Uneven temperature distribution, with temperature differences of up to 100°C between the water inlet / outlet pipes and the end face of the end cap, leads to stress concentration in the weld overlay, making it prone to cracks and other defects, thus affecting the safe service life of the equipment.

[0010] 3. It cannot adapt to the curved shape of the head, resulting in a heating blind zone and making it difficult to guarantee the stability of the weld overlay quality.

[0011] 4. It relies on manual operation, has low temperature control accuracy, and is difficult to meet the high-precision manufacturing standards of nuclear power equipment. Summary of the Invention

[0012] To address the problems of low gas heating efficiency, poor processability, and uneven heating temperature in the pre-welding, heat preservation, and post-welding hydrogen removal heating processes of the inner wall of a nuclear power plant evaporator, this invention provides an electromagnetic induction heating device for welding the inner wall of a nuclear power plant evaporator head. The technical solution of this invention is as follows: An electromagnetic induction heating device for surfacing the inner wall of a nuclear power plant evaporator head includes a contour-following induction heater. The contour-following induction heater includes at least two spherical contour-following induction heaters and at least two end-face contour-following induction heaters with the same structure. The spherical contour-following induction heaters and the end-face contour-following induction heaters are assembled and fixed to the outer wall of the head through connectors, forming an integral heating frame that fits the shape of the head.

[0013] The spherical contour induction heater includes a first spherical contour induction heater (1) and a second spherical contour induction heater (2). The first spherical contour induction heater (1) and the second spherical contour induction heater (2) have the same structure, both including a spherical contour frame (10a), a spherical contour insulation layer (20a), a spherical induction cable (30a) and a spherical temperature measuring element (40a). The spherical contour frame (10a) has an arc surface structure adapted to the curvature of the outer wall of the spherical end cap. A spherical insulation layer (20a) is installed on the spherical contour frame (10a) and on the side closer to the end cap. A spherical temperature measuring element (40a) and a spherical induction cable (30a) are also installed on the spherical contour frame (10a). The spherical induction cable (30a) is used to pass in a medium-frequency induced current.

[0014] The end-face contouring induction heater includes a first end-face contouring induction heater (3) and a second end-face contouring induction heater (4). The first end-face contouring induction heater (3) and the second end-face contouring induction heater (4) have the same structure, both including an end-face contouring frame (10b), an end-face contouring insulation layer (20b), an end-face induction cable (30b), an end-face temperature measuring element (40b), and a fixing clamp (70). The end-face contouring frame (10b) has a structure adapted to the end face of the end cap. On the end-face contouring frame (10b) The end face conformal insulation layer (20b) is installed on the side near the end cap. The end face temperature measuring element (40b) and the end face induction cable (30b) are also installed on the end face conformal frame (10b). The end face induction cable (30b) is used to pass in medium frequency induction current. The fixing clamp (70) is installed at the bottom of the end face conformal frame (10b). The fixing clamp (70) is used to fix the first end face conformal induction heater (3) and the second end face conformal induction heater (4) on the end face of the end cap.

[0015] The connecting components include a first bolt, a second bolt, a third bolt, and a fourth bolt. The first spherical contour induction heater (1) and the second spherical contour induction heater (2) are detachably connected together by the first bolt. The first spherical contour induction heater (1) and the first end face contour induction heater (3) are detachably connected together by the second bolt (61). The second spherical contour induction heater (2) and the second end face contour induction heater (4) are detachably connected together by the third bolt. The fixing plates (70) on the first end face contour induction heater (3) and the second end face contour induction heater (4) are detachably connected to the end face of the end cap by the fourth bolt.

[0016] Both the spherical contour frame (10a) and the end face contour frame (10b) are assembled from multiple longitudinal and transverse arc-shaped high-temperature resistant insulating plates and connected by fasteners to form an arc-shaped structure that matches the curvature of the outer wall of the end cap.

[0017] It also includes a temperature control system, which is connected to the spherical temperature measuring element (40a), the end face temperature measuring element (40b), and the intermediate frequency power supply signal that supplies power to the spherical induction cable (30a) and the end face induction cable (30b), forming a closed-loop control circuit. Based on the temperature feedback data collected by each temperature measuring element, the system dynamically adjusts the first spherical contour induction heater (1) and the second spherical contour induction heater (2). The output power of the first end face contour induction heater (3) and the second end face contour induction heater (4).

[0018] The coiling density of the spherical induction cable (30a) on the spherical contour frame (10a) and the coiling density of the end face induction cable (30b) on the end face contour frame (10b) are matched and set according to the wall thickness distribution at the corresponding position of the end cap. The cable coiling density is set higher in the area with larger wall thickness than in the area with smaller wall thickness. The thickness of the area with larger wall thickness is 180-289mm, and the thickness of the area with smaller wall thickness is 96-180mm.

[0019] A heating method for overlay welding on the inner wall of a head using the aforementioned electromagnetic induction heating device includes the following steps: S1. Installation and fixing: The first spherical contour induction heater (1), the second spherical contour induction heater (2), the first end face contour induction heater (3) and the second end face contour induction heater (4) are respectively installed on the spherical area and end face area of ​​the outer wall of the head, and the connecting parts are used to complete the fixed connection between them and between them and the head. S2. Preheating before welding: Start all contour induction heaters, pass medium frequency induction current to each induction cable, set the target preheating temperature T1 through the temperature control system, and dynamically adjust the output power of each heater according to the real-time feedback of each temperature measuring element until the temperature of the weld overlay area on the inner wall of the head reaches and stabilizes at T1. S3. Synchronous Welding and Interpass Temperature Control: After preheating, the welding process on the inner wall of the head is initiated. During the welding process, the temperature is continuously monitored and the power is adjusted by the temperature control system to maintain the interpass temperature of the welding area within the preset process temperature range [T2]. min T2 max ]Inside; S4. Post-weld heat treatment: After all the welding is completed, the first spherical contour induction heater (1), the second spherical contour induction heater (2), the first end face contour induction heater (3) and the second end face contour induction heater (4) are controlled by the temperature control system to heat the entire end cap to the post-weld heat treatment temperature T3, and the end cap is kept at this temperature for a set time t. S5. Cooling and disassembly: After the heat treatment is completed, turn off all the contour induction heaters. After the end cap cools to a safe temperature, disassemble and remove the first spherical contour induction heater (1), the second spherical contour induction heater (2), the first end face contour induction heater (3), and the second end face contour induction heater (4).

[0020] In step S2, the preheating temperature T1 is 150℃~250℃; in step S3, the interpass temperature maintenance range [T2]... min T2 maxThe preheating temperature before welding is T1 ±20℃; in step S4, the post-weld heat treatment temperature T3 is 250℃~400℃, and the holding time t is 1~4 hours.

[0021] During the welding process in step S3, the end cap rotates around its axis, and all the contour induction heaters continue to work, so as to achieve synchronous heating and welding.

[0022] The advantages of this invention are: 1. By dividing the heating frame into multiple independent heating zones that precisely conform to the curvature of the end cap, and combining this with a closed-loop temperature control system to independently and dynamically adjust the power of each zone, the problem of uneven heating of large, irregularly shaped curved workpieces is effectively solved. This improves the metallurgical quality and bonding strength of the weld overlay, and reduces stress concentration and cracking tendency caused by temperature gradients.

[0023] 2. By adopting the principle of electromagnetic induction non-contact heating, energy is directly applied to the head body, resulting in low heat loss, improved energy utilization, shortened overall welding heating cycle of a single head, significantly improved production efficiency, and reduced energy consumption and carbon emissions.

[0024] 3. The modular, contour-following frame design, using multiple curved insulating plates spliced ​​together to form an arc surface adaptable to different curvatures, combined with detachable connectors (such as bolts), allows the device to be quickly and accurately installed on nuclear power plant evaporator heads of various specifications. This design significantly improves the equipment's versatility and operational flexibility, while reducing tooling manufacturing costs.

[0025] 4. By integrating multi-channel temperature sensors and an intelligent temperature control system, real-time monitoring and closed-loop feedback control of the temperature throughout the entire process of preheating, interpass insulation, and post-weld heat treatment are achieved, improving the temperature uniformity of the workpiece. This technical solution overcomes the randomness of manual temperature control, eliminates the variability of manual operation, and ensures the consistency of welding process parameters, thereby guaranteeing the stability and repeatability of weld overlay quality.

[0026] 5. The use of non-contact electromagnetic induction heating fundamentally eliminates the safety hazards of open flames and gas leaks that may exist with traditional flame heating. Simultaneously, temperature data throughout the entire process can be automatically recorded and stored, achieving complete traceability of process parameters and meeting the stringent quality control requirements of the nuclear power equipment manufacturing industry.

[0027] 6. This technical solution breaks the foreign technological monopoly in the field of high-end nuclear power head heating equipment, provides key technical support for the independent manufacturing of major nuclear power equipment, and is an important manifestation of the autonomy and technological progress of my country's nuclear power equipment industry chain. Attached Figure Description

[0028] Figure 1This is a schematic diagram of the main structure of the present invention.

[0029] Figure 2 This is a schematic diagram of the end cap structure of the present invention.

[0030] Figure 3 yes Figure 1 A schematic diagram of the structure of the first end face contour induction heater (second end face contour induction heater).

[0031] Figure 4 yes Figure 3 Another perspective structural diagram.

[0032] Figure 5 yes Figure 1 A schematic diagram of the structure of the first spherical contour induction heater (the second spherical contour induction heater).

[0033] Figure 6 yes Figure 5 Another perspective structural diagram. Detailed Implementation

[0034] The present invention will be further described below with reference to specific embodiments, and the advantages and features of the present invention will become clearer as a result. However, these embodiments are merely exemplary and do not constitute any limitation on the scope of the present invention. Those skilled in the art should understand that modifications or substitutions can be made to the details and form of the technical solutions of the present invention without departing from the spirit and scope of the present invention, but all such modifications and substitutions fall within the protection scope of the present invention.

[0035] See Figures 1 to 6 This invention relates to an electromagnetic induction heating device for welding the inner wall of a nuclear power plant evaporator head, comprising a contour-following induction heater, wherein the contour-following induction heater includes at least two spherical contour-following induction heaters and at least two end-face contour-following induction heaters with identical structures; the spherical contour-following induction heaters and the end-face contour-following induction heaters are assembled and fixed to the outer wall of the head by connectors, together forming an integral heating frame that fits the shape of the head.

[0036] This invention uses multiple independent contour-following induction heaters, assembled into a unified frame that fits tightly with the shape of the end cap via connectors. This achieves comprehensive and uniform contact with irregular curved surfaces (especially hemispherical surfaces with high curvature), solving the problems of traditional heating methods that struggle to cover curved surfaces and have heating blind spots. As a result, the weld overlay area on the inner wall of the end cap achieves a highly uniform temperature field, effectively reducing the risk of welding stress and deformation caused by excessive local temperature differences, significantly improving the metallurgical quality of the weld overlay and the safe service life of the equipment.

[0037] The spherical and end-face contour induction heaters adopt a modular design and are quickly assembled and fixed using bolted detachable connectors. This allows for rapid and precise adaptation to nuclear power plant evaporator heads of different sizes and specifications, significantly reducing tooling preparation and changeover time. Modular assembly also facilitates transportation, installation, and maintenance, thereby improving the overall operational efficiency and economic benefits of nuclear power equipment manufacturing.

[0038] The spherical contour induction heater includes a first spherical contour induction heater 1 and a second spherical contour induction heater 2. The first spherical contour induction heater 1 and the second spherical contour induction heater 2 have the same structure, both including a spherical contour frame 10a, a spherical contour insulation layer 20a, a spherical induction cable 30a, and a spherical temperature measuring element 40a. The spherical contour frame 10a has an arc surface structure adapted to the curvature of the outer wall of the spherical end cap. The spherical contour frame 10a is installed on the spherical contour frame 10a, and the spherical temperature measuring element 40a and the spherical induction cable 30a are also installed on the spherical contour frame 10a. The spherical induction cable 30a is used to pass in a medium-frequency induced current.

[0039] The working principle of the spherical contour induction heater is based on the combination of electromagnetic induction heating and contour bonding. Its specific working process is as follows: 1. A medium-frequency alternating current is passed through the spherical induction cable 30a, generating a high-frequency alternating magnetic field around the cable. This magnetic field penetrates the spherical conformal insulation layer 20a and acts on the metal material of the spherical end cap, inducing eddy currents within it. As the eddy currents flow inside the metal, Joule heating is generated due to resistance, thus causing the end cap itself to heat up.

[0040] 2. The spherical contour frame 10a has an arc surface structure that perfectly matches the curvature of the outer wall of the spherical end cap, ensuring that the induction cable maintains a uniform and tight fit with the workpiece surface. This contour design makes the magnetic field distribution more uniform, laying the foundation for temperature field uniformity from a physical structure perspective.

[0041] 3. The spherical conformal insulation layer 20a installed close to the end cap can effectively prevent heat loss to the surrounding environment, concentrate the induced heat energy in the end cap body, significantly improve thermal efficiency, and help achieve rapid heating and stable insulation.

[0042] 4. The spherical temperature sensing element 40a monitors the temperature of the heating area in real time and transmits the signal to the temperature control system. The system dynamically adjusts the current in the input sensing cable based on the deviation between the set temperature and the measured temperature, thereby achieving closed-loop precise control of the heating power.

[0043] The spherical contour insulation layer 20a indicates that the contour insulation layer (insulation blanket) is installed on the spherical contour frame 10a; the spherical induction cable indicates that the induction cable is installed on the spherical contour frame 10a; and the spherical temperature measuring element 40a indicates that the temperature measuring element is installed on the spherical contour frame 10a. The names are based on the installation position.

[0044] The spherical contour frame has an arc surface structure that precisely matches the curvature of the outer wall of the end cap, and integrates an induction cable to ensure a tight and complete fit between the heating unit and the irregular curved surface of the workpiece. This contour design eliminates heating blind spots, allowing the induced magnetic field and eddy current heat to act uniformly on the spherical end cap, laying the physical foundation for achieving a highly uniform temperature field in the inner wall welding area and effectively ensuring welding quality.

[0045] This spherical, contoured insulation layer directly faces the heated working surface, effectively blocking heat loss through radiation and convection, concentrating the induced heat energy within the head body. This design significantly improves thermal efficiency, reduces energy loss, and achieves energy conservation and consumption reduction while enabling rapid heating and stable insulation.

[0046] The spherical temperature sensing element and spherical induction cable are integrated and mounted together on the contoured frame. This integrated design allows the temperature sensing signal to reflect the actual state of the corresponding heating area in real time and accurately, providing direct and reliable feedback for the closed-loop temperature control system. Combined with the induction cable for introducing medium-frequency current, precise control of each independent spherical heating area is achieved, ensuring the controllability and process consistency of the entire heating process.

[0047] The end-face contouring induction heater includes a first end-face contouring induction heater 3 and a second end-face contouring induction heater 4. The first end-face contouring induction heater 3 and the second end-face contouring induction heater 4 have the same structure, each including an end-face contouring frame 10b, an end-face contouring insulation layer 20b, an end-face induction cable 30b, an end-face temperature measuring element 40b, and a fixing clamp 70. The end-face contouring frame 10b has a structure adapted to the end face of the end cap. The end-face contouring insulation layer 20b is installed on the end-face contouring frame 10b, and the end-face temperature measuring element 40b and the end-face induction cable 30b are also installed on the end-face contouring frame 10b. The end-face induction cable 30b is used to carry a medium-frequency induction current. The fixing clamp 70 is installed at the bottom of the end-face contouring frame 10b, and the fixing clamp 70 is used to fix the first end-face contouring induction heater 3 and the second end-face contouring induction heater 4 on the end face of the end cap.

[0048] The working principle of the end-face contour induction heater is as follows: 1. First, the entire end-face contour induction heater is installed on the end face of the head by fixing the clamp 70 and connecting parts, ensuring that the end-face contour frame 10b and all its functional components are stably and tightly fitted with the end face of the head. This is the physical basis for subsequent efficient induction heat transfer.

[0049] 2. A medium-frequency induced current is passed through the end-face induction cable 30b, generating an alternating magnetic field around it. This magnetic field penetrates the end-face conformal insulation layer 20b and acts on the metal in the end-face region of the head, inducing eddy currents. As the eddy currents flow inside the metal, they generate Joule heating due to resistance, thereby causing the end-face of the head to heat up.

[0050] 3. The end-face conformal insulation layer 20b located between the frame body and the end cap effectively blocks the loss of heat to the outside (especially along the axial direction of the end cap), confining the induced heat energy to the end body of the end cap to the maximum extent, significantly improving heating efficiency and helping to maintain temperature stability.

[0051] 4. The end-face temperature sensing element 40b collects the temperature signal of the end-face heating area in real time and transmits it to the temperature control system. The system compares this signal with the set temperature and dynamically adjusts the current supplied to the induction cable, thereby achieving precise and independent temperature control of the end-face heating area.

[0052] The term "end-face conformal insulation layer 20b" indicates that the conformal insulation layer (insulation blanket) is installed on the end-face conformal frame 10b; "end-face induction cable" indicates that the induction cable is installed on the end-face conformal frame 10b; and "end-face temperature measuring element 40a" indicates that the temperature measuring element is installed on the end-face conformal frame 10b. These names are based on the installation location.

[0053] The end-face conformal frame has a structure that precisely matches the end face of the head and integrates an induction cable, ensuring that the heating unit can completely cover the end face area of ​​the head. This targeted design solves the problem of uniform heating of this key feature at the end (often the bevel, flange, and other connection parts), providing a uniform temperature base for subsequent welding, which is crucial for ensuring the integrity of the overall structure of the head and the sealing of the interface.

[0054] An end-face conformal insulation layer is provided on the side of the end-face conformal frame body near the end cap. This layer is in close contact with the workpiece end face, effectively preventing heat loss in the axial direction and efficiently confining the induced eddy current heat inside the end cap body. This design significantly improves the thermal efficiency of the end face area, ensuring that the end face and spherical area can reach and maintain the process temperature simultaneously, achieving coordinated control of the overall temperature field.

[0055] By integrating the end-face temperature sensing element and induction cable into the frame, independent, real-time temperature monitoring of the end-face heating area is achieved. Simultaneously, the unique fixing clamp design (connected to the end face of the end cap via bolts) provides a robust and stable mechanical fixation for the end-face heater. This not only ensures the accuracy of end-face temperature control but also guarantees the reliability of the heater installation under conditions where the workpiece may rotate or vibrate, thus improving the safety and process stability of the entire heating process.

[0056] The connecting components include a first bolt, a second bolt, a third bolt, and a fourth bolt. The first spherical contour induction heater 1 and the second spherical contour induction heater 2 are detachably connected together by the first bolt; the first spherical contour induction heater 1 and the first end face contour induction heater 3 are detachably connected together by the second bolt; the second spherical contour induction heater 2 and the second end face contour induction heater 4 are detachably connected together by the third bolt; and the fixing clamps 70 on the first end face contour induction heater 3 and the second end face contour induction heater 4 are detachably connected to the end face of the end cap by the fourth bolt.

[0057] For heads of different specifications, tooling can be quickly adapted and assembled simply by adjusting or replacing the corresponding modules, which significantly shortens production preparation time and greatly improves the equipment's adaptability to different workpieces and the flexibility of the production line.

[0058] The first bolt connects the two spherical heaters, the second and third bolts connect the spherical heaters to the end-face heaters, and the fourth bolt fixes the end-face heaters to the workpiece, forming a stable and rigid frame. This design not only ensures the structural stability and safety of the entire heating device under conditions of head rotation or vibration, but more importantly, it ensures a tight and uniform fit between each contoured heater and the outer wall of the complex curved head through reliable mechanical constraints. This is the fundamental prerequisite for achieving efficient and uniform induction heating.

[0059] Both the spherical contouring frame 10a and the end-face contouring frame 10b are assembled from multiple longitudinal and transverse arc-shaped high-temperature resistant insulating plates, connected by fasteners to form an arc-shaped structure that matches the curvature of the outer wall of the end cap. This modular arc-shaped high-temperature resistant insulating plate assembly structure achieves high-precision, low-cost contouring of the complex curved surface of the end cap, and fundamentally ensures the long-term insulation reliability and structural stability of the induction heating device under high-temperature and strong electromagnetic field environments.

[0060] It also includes a temperature control system, which is connected to the spherical temperature measuring element 40a, the end face temperature measuring element 40b, and the intermediate frequency power supply signal that powers the spherical induction cable 30a and the end face induction cable 30b, forming a closed-loop control circuit. Based on the temperature feedback data collected by each temperature measuring element, the system dynamically adjusts the output power of the first spherical contour induction heater 1, the second spherical contour induction heater 2, the first end face contour induction heater 3, and the second end face contour induction heater 4. This structure enables precise and independent closed-loop control of multiple independent heating areas on the spherical and end faces of the end cap. By dynamically adjusting the power output of each area through real-time temperature feedback, it ensures the temperature uniformity and process stability of the entire complex curved workpiece during preheating, heat preservation, and heat treatment, effectively improving the reliability and consistency of the welding quality.

[0061] The winding density of the spherical induction cable 30a on the spherical contour frame 10a and the winding density of the end face induction cable 30b on the end face contour frame 10b are matched and set according to the wall thickness distribution at the corresponding position of the end cap. The thickness of the thicker wall area is 180-289mm, and the thickness of the thinner wall area is 96-180mm. By establishing a positive correlation between the winding density of the induction cable and the local wall thickness of the end cap, the difference in heat capacity between different thickness areas is intelligently compensated. This proactively optimizes the spatial distribution of the induction magnetic field and eddy currents at the source, achieving a high degree of uniformity in the heating temperature field of the entire complex irregular curved surface workpiece and overcoming the industry problem of local overheating or underheating caused by uneven wall thickness.

[0062] The present invention also relates to a heating method for overlay welding on the inner wall of a head using the aforementioned electromagnetic induction heating device, comprising the following steps: S1. Installation and Fixing: The first spherical contour induction heater 1, the second spherical contour induction heater 2, the first end face contour induction heater 3, and the second end face contour induction heater 4 are respectively installed on the spherical and end face regions of the outer wall of the head, and the connecting parts are used to complete the fixed connection between them and between them and the head; the contour induction heaters are assembled and fixed to the head through detachable connecting parts, realizing the modularity of the device. This allows the tooling to be quickly and accurately adapted to heads of different specifications, significantly reducing production preparation and tooling changeover time, and greatly improving the equipment's versatility and operational flexibility.

[0063] S2. Preheating before welding: Start all contour induction heaters, supply medium-frequency induction current to each induction cable, set the target preheating temperature T1 through the temperature control system, and dynamically adjust the output power of each heater based on real-time feedback from each temperature measuring element until the temperature of the weld overlay area on the inner wall of the head reaches and stabilizes at T1 uniformly. The temperature control system independently and dynamically adjusts the power of each heater based on real-time feedback from the temperature measuring elements in each area. This closed-loop control ensures that the weld overlay area on the inner wall of the head can quickly and uniformly reach and stabilize at the target preheating temperature, providing a stable and reliable thermal starting point for subsequent weld overlay, thus guaranteeing welding quality from the source. In step S2, the preheating temperature T1 is 150℃~250℃. In step S3, the interpass temperature maintenance range [T2min, T2max] is the preheating temperature T1 ±20℃. In step S4, the post-weld heat treatment temperature T3 is 250℃~400℃, and the holding time t is 1~4 hours.

[0064] S3. Synchronous Welding and Interpass Temperature Control: After preheating, the welding process on the inner wall of the head is initiated. During the welding process, the temperature is continuously monitored and the power is adjusted by the temperature control system to maintain the interpass temperature of the welding area within the preset process temperature range [T2]. min T2 max During the welding process, the heating power is continuously monitored and dynamically adjusted to maintain the interpass temperature within a strict process range. Especially during the rotary welding of the head, this real-time control ensures that the welding thermal cycle is always in optimal condition, effectively controlling welding stress and deformation, and guaranteeing the stability of the welding process and the uniformity of weld quality. In step S3, during the welding process, the head rotates around its axis, and all the contour-following induction heaters operate continuously, achieving synchronization between heating and welding. This achieves continuous, uniform, and dynamic heat preservation of large heads under continuous rotary welding conditions. Through the strict synchronization of the heaters and welding actions, the welding thermal cycle is always kept within the optimal temperature range, effectively controlling welding stress and deformation, and significantly improving the thermal stability of the welding process and the consistency of weld quality.

[0065] S4. Post-weld heat treatment: After all the welding is completed, the first spherical contour induction heater 1, the second spherical contour induction heater 2, the first end face contour induction heater 3 and the second end face contour induction heater 4 are controlled by the temperature control system to heat the entire end cap to the post-weld heat treatment temperature T3, and the end cap is held at this temperature for a set time t. The integrated process not only saves process changeover time and improves overall efficiency, but also ensures precise control of heat treatment temperature and time, which is crucial for eliminating welding residual stress and completing hydrogen removal treatment, thus improving the reliability and consistency of process results. S5. Cooling and Disassembly: After heat treatment, turn off all contouring induction heaters. After the end cap has cooled to a safe temperature, disassemble and remove the first spherical contouring induction heater 1, the second spherical contouring induction heater 2, the first end face contouring induction heater 3, and the second end face contouring induction heater 4. This avoids potential equipment damage or personal injury that may result from high-temperature disassembly. Simultaneously, the modular disassembly method facilitates cleaning, inspection, and maintenance of the heaters, ensuring a long service life and good reusability of the equipment.

[0066] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An electromagnetic induction heating device for welding the inner wall of a nuclear power plant evaporator head, characterized in that, The device includes a contour-following induction heater, which comprises at least two spherical contour-following induction heaters and at least two end-face contour-following induction heaters with identical structures. The spherical contour-following induction heaters and the end-face contour-following induction heaters are assembled and fixed to the outer wall of the head through connectors, forming an integral heating frame that fits the shape of the head.

2. The electromagnetic induction heating device for welding the inner wall of a nuclear power plant evaporator head according to claim 1, characterized in that, The spherical contour induction heater includes a first spherical contour induction heater (1) and a second spherical contour induction heater (2). The first spherical contour induction heater (1) and the second spherical contour induction heater (2) have the same structure, both including a spherical contour frame (10a), a spherical contour insulation layer (20a), a spherical induction cable (30a) and a spherical temperature measuring element (40a). The spherical contour frame (10a) has an arc surface structure adapted to the curvature of the outer wall of the spherical end cap. A spherical insulation layer (20a) is installed on the spherical contour frame (10a) and on the side closer to the end cap. A spherical temperature measuring element (40a) and a spherical induction cable (30a) are also installed on the spherical contour frame (10a). The spherical induction cable (30a) is used to pass in a medium-frequency induced current.

3. The electromagnetic induction heating device for welding the inner wall of a nuclear power plant evaporator head according to claim 2, characterized in that, The end-face contouring induction heater includes a first end-face contouring induction heater (3) and a second end-face contouring induction heater (4). The first end-face contouring induction heater (3) and the second end-face contouring induction heater (4) have the same structure, both including an end-face contouring frame (10b), an end-face contouring insulation layer (20b), an end-face induction cable (30b), an end-face temperature measuring element (40b), and a fixing clamp (70). The end-face contouring frame (10b) has a structure adapted to the end face of the end cap. On the end-face contouring frame (10b) The end face conformal insulation layer (20b) is installed on the side near the end cap. The end face temperature measuring element (40b) and the end face induction cable (30b) are also installed on the end face conformal frame (10b). The end face induction cable (30b) is used to pass in medium frequency induction current. The fixing clamp (70) is installed at the bottom of the end face conformal frame (10b). The fixing clamp (70) is used to fix the first end face conformal induction heater (3) and the second end face conformal induction heater (4) on the end face of the end cap.

4. The electromagnetic induction heating device for welding the inner wall of a nuclear power plant evaporator head according to claim 3, characterized in that, The connecting components include a first bolt, a second bolt, a third bolt, and a fourth bolt. The first spherical contour induction heater (1) and the second spherical contour induction heater (2) are detachably connected together by the first bolt. The first spherical contour induction heater (1) and the first end face contour induction heater (3) are detachably connected together by the second bolt. The second spherical contour induction heater (2) and the second end face contour induction heater (4) are detachably connected together by the third bolt. The fixing plates (70) on the first end face contour induction heater (3) and the second end face contour induction heater (4) are detachably connected to the end face of the end cap by the fourth bolt.

5. The electromagnetic induction heating device for welding the inner wall of a nuclear power plant evaporator head according to claim 3 or 4, characterized in that, Both the spherical contour frame (10a) and the end face contour frame (10b) are assembled from multiple longitudinal and transverse arc-shaped high-temperature resistant insulating plates and connected by fasteners to form an arc-shaped structure that matches the curvature of the outer wall of the end cap.

6. The electromagnetic induction heating device for welding the inner wall of a nuclear power plant evaporator head according to claim 3, characterized in that, It also includes a temperature control system, which is connected to the spherical temperature measuring element (40a), the end face temperature measuring element (40b), and the intermediate frequency power supply signal that supplies power to the spherical induction cable (30a) and the end face induction cable (30b), forming a closed-loop control circuit; based on the temperature feedback data collected by each temperature measuring element, the first spherical contour induction heater (1) and the second spherical contour induction heater (2) are dynamically adjusted. The output power of the first end face contour induction heater (3) and the second end face contour induction heater (4).

7. The electromagnetic induction heating device for welding the inner wall of a nuclear power plant evaporator head according to claim 6, characterized in that, The coiling density of the spherical induction cable (30a) on the spherical contour frame (10a) and the coiling density of the end face induction cable (30b) on the end face contour frame (10b) are matched and set according to the wall thickness distribution at the corresponding position of the end cap. The cable coiling density is set higher in the area with larger wall thickness than in the area with smaller wall thickness. The thickness of the area with larger wall thickness is 180-289mm, and the thickness of the area with smaller wall thickness is 96-180mm.

8. A heating method for overlay welding of the inner wall of a head using the electromagnetic induction heating device as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Installation and fixing: The first spherical contour induction heater (1), the second spherical contour induction heater (2), the first end face contour induction heater (3) and the second end face contour induction heater (4) are respectively installed on the spherical area and end face area of ​​the outer wall of the head, and the connecting parts are used to complete the fixed connection between them and between them and the head. S2. Preheating before welding: Start all contour induction heaters, pass medium frequency induction current to each induction cable, set the target preheating temperature T1 through the temperature control system, and dynamically adjust the output power of each heater according to the real-time feedback of each temperature measuring element until the temperature of the weld overlay area on the inner wall of the head reaches and stabilizes at T1. S3. Synchronous Welding and Interpass Temperature Control: After preheating, the welding process on the inner wall of the head is initiated. During the welding process, the temperature is continuously monitored and the power is adjusted by the temperature control system to maintain the interpass temperature of the welding area within the preset process temperature range [T2]. min T2 max ]Inside; S4. Post-weld heat treatment: After all the welding is completed, the first spherical contour induction heater (1), the second spherical contour induction heater (2), the first end face contour induction heater (3) and the second end face contour induction heater (4) are controlled by the temperature control system to heat the entire end cap to the post-weld heat treatment temperature T3, and the end cap is kept at this temperature for a set time t. S5. Cooling and disassembly: After the heat treatment is completed, turn off all the contour induction heaters. After the end cap cools to a safe temperature, disassemble and remove the first spherical contour induction heater (1), the second spherical contour induction heater (2), the first end face contour induction heater (3), and the second end face contour induction heater (4).

9. The heating method according to claim 8, characterized in that, In step S2, the preheating temperature T1 is 150℃~250℃; in step S3, the interpass temperature maintenance range [T2]... min T2 max The preheating temperature before welding is T1 ±20℃; In step S4, the post-weld heat treatment temperature T3 is 250℃~400℃, and the holding time t is 1~4 hours.

10. The heating method according to claim 8 or 9, characterized in that, During the welding process in step S3, the end cap rotates around its axis, and all the contour induction heaters continue to work, so as to achieve synchronous heating and welding.

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