An on-line heat treatment device and on-line heat treatment process for nickel-based welded pipes for solar thermal power stations

Abstract

This application relates to an online heat treatment device and process for nickel-based welded pipes used in solar thermal power plants. A high-frequency induction heating unit, a resistance radiation homogenization and insulation unit, and a rapid cooling unit are coaxially connected sequentially along the continuous conveying direction of the welded pipe. The high-frequency induction heating unit includes a high-frequency heating power supply, a copper tube heating resistance wire, and a high-temperature resistant quartz tube. Both ends of the copper tube heating resistance wire are electrically connected to the high-frequency heating power supply. The main body of the copper tube heating resistance wire is wound around the outer wall of the high-temperature resistant quartz tube with equal pitch, and the inner cavity of the high-temperature resistant quartz tube forms a first heating chamber for the continuous passage of the nickel-based welded pipe. The resistance radiation homogenization and insulation unit includes an insulation box, insulation cotton arranged in the assembly space of the insulation box, and 1-36 sets of resistance radiation heating components evenly arranged inside the insulation box. The insulation box has a second heating chamber coaxially communicating with the heating chamber of the high-frequency induction heating unit, and the resistance radiation heating components are evenly arranged around the second heating chamber circumferentially. The nickel-based alloy welded pipes produced by this device and process have uniform grain size and stable performance.

Description

Technical Field

[0001] This application belongs to the field of heat treatment equipment and process technology for metal pipes, specifically relating to a continuous online heat treatment device for nickel-based welded pipes and a supporting online heat treatment process suitable for high-temperature conditions in solar thermal power plants. Background Technology

[0002] Nickel-based welded pipes used in the heat collection and exchange systems of concentrated solar power plants operate under high temperature, high pressure, and corrosive media environments for extended periods, placing stringent requirements on the pipe material's grain size uniformity, mechanical property stability, high-temperature creep resistance, and resistance to intergranular corrosion. After forming, the welded pipes require heat treatment to eliminate residual welding stress and complete recrystallization and microstructure homogenization. Traditional offline heat treatment suffers from drawbacks such as large batch-to-batch performance fluctuations, poor coordination between heating and holding, uncontrollable cooling rates, and low production efficiency.

[0003] Existing online heat treatment equipment mostly employs single induction heating or resistance heating, which presents two major problems: First, induction heating provides rapid heating but suffers from poor temperature uniformity, resulting in a large temperature difference between the circumferential and wall thickness directions of the welded pipe, easily leading to localized overheating or insufficient recrystallization. Second, resistance heating offers good temperature uniformity but has a slow heating rate, which cannot match the continuous conveying cycle of the welded pipe, and the heating element layout is unreasonable, resulting in low radiant heat utilization and poor heat preservation. Furthermore, existing processes do not match the full-process parameters of rapid heating-precise temperature uniformity-high-speed cooling to the characteristics of nickel-based alloys, resulting in welded pipes with dispersed grain size and substandard mechanical properties, making it difficult to meet the long-term safe operation requirements of solar thermal power plants.

[0004] Therefore, developing an online heat treatment device and process that provides uniform heating, precise temperature control, continuous and efficient operation, and ensures stable microstructure and properties of nickel-based welded pipes has become an urgent technical problem to be solved in this field. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this application provides an online heat treatment device and process for nickel-based welded pipes used in solar thermal power plants. Through a three-section coaxial connection structure of high-frequency induction rapid heating + resistance radiation uniform temperature holding + rapid quenching and cooling, continuous online heat treatment of nickel-based welded pipes is achieved, solving the problems of uneven heating, inaccurate temperature control, and large performance fluctuations. This results in welded pipes with uniform grain size, stable mechanical properties, and excellent high-temperature creep resistance.

[0006] In a first aspect, this application provides an online heat treatment device for nickel-based welded pipes used in solar thermal power plants. A high-frequency induction heating unit, a resistance radiation uniform temperature insulation unit, and a rapid cooling unit are sequentially and coaxially connected along the continuous conveying direction of the welded pipe. The high-frequency induction heating unit includes a high-frequency heating power supply, a copper tube heating resistance wire, and a high-temperature resistant quartz tube. The two ends of the copper tube heating resistance wire are electrically connected to the high-frequency heating power supply, and the main body of the copper tube heating resistance wire is wound around the outer wall of the high-temperature resistant quartz tube with equal pitch. The inner cavity of the high-temperature resistant quartz tube forms a first heating chamber through which the nickel-based welded pipe continuously passes. The resistance radiation uniform temperature insulation unit includes an insulation box, insulation cotton disposed in the assembly space of the insulation box, and 1-36 sets of resistance radiation heating components uniformly arranged inside the insulation box. The insulation box has a second heating chamber coaxially communicating with the heating chamber of the high-frequency induction heating unit, and the resistance radiation heating components are uniformly arranged around the second heating chamber circumferentially.

[0007] The matrix of nickel-based welded pipe is a γ-Ni face-centered cubic metallic bond crystal, which exhibits high dislocation density, grain boundary alloy element segregation, and welding residual stress after welding. High-frequency induction heating utilizes the eddy current effect to achieve rapid volumetric heating, activating the thermal diffusion activity of γ-Ni lattice atoms and promoting dislocation annihilation and recrystallization nucleation. Resistance radiation temperature equalization and heat preservation use infrared radiation heat to achieve circumferential uniform temperature control, reducing grain boundary energy and eliminating alloy element segregation. Rapid cooling quickly locks in the high-temperature microstructure, inhibiting abnormal grain growth and maintaining the regularity of the metallic bond crystal. The coaxial connection structure eliminates temperature interruptions during pipe transportation, ensuring the continuity of lattice atom diffusion. This enables continuous online heat treatment of nickel-based welded pipes, eliminating welding residual stress, completing full recrystallization, significantly improving the mechanical properties and microstructure uniformity of the pipe, and meeting the high-temperature service requirements of solar thermal power plants. High-frequency induction rapid heating and resistance radiation uniform temperature preservation complement each other, solving the defects of single heating methods such as "rapid but uneven heating, good temperature uniformity but slow heating"; rapid cooling and the preceding heating and insulation unit work together to lock in a uniform recrystallization structure, and the three work together in a coaxial manner to achieve stable temperature control throughout the entire process.

[0008] Furthermore, the heating power of the resistance radiation heating component is 24-48kw, including a spiral resistance wire made of HRE material and an insulating ceramic tube sleeved inside the spiral resistance wire. The spiral resistance wire has an outer diameter of Φ46±5mm and an inner diameter of Φ37±5mm; the insulating ceramic tube has an outer diameter of Φ35±5mm, an inner diameter of Φ25±5mm, and a length of 680±180mm.

[0009] HRE alloy resistance wire is primarily bonded by metallic bonds, exhibiting excellent lattice stability, oxidation resistance, and creep resistance at high temperatures, enabling long-term stable radiant heat energy at temperatures above 1150℃. The insulating ceramic tube is an ionic crystal, possessing both electrical insulation and infrared transmittance, effectively isolating the resistance wire from the heating cavity while ensuring efficient radiant heat penetration. The spiral size and power parameters are matched to the thermal diffusion rate of the nickel-based alloy, ensuring that the radiant heat flux is compatible with the heat absorption rate of γ-Ni lattice atoms, preventing lattice distortion caused by localized overheating. This enhances the high-temperature stability of the heating component, extends its service life, improves the uniformity of the radiant heat field, and eliminates defects such as localized overheating or underheating in the circumferential direction of the nickel-based welded tube. In conjunction with the resistance radiation temperature equalization and insulation unit, it precisely matches the heating rhythm after high-frequency induction heating, ensuring uniform diffusion of lattice atoms during recrystallization and further improving grain size uniformity.

[0010] Furthermore, the insulated box is constructed of refractory bricks to form a layered structure, the outer surface of which is covered with a high-temperature resistant material, and the insulated box has at least one through hole.

[0011] The refractory bricks are silicate ionic crystals with extremely low thermal conductivity, reducing heat loss from the heating chamber. The layered structure further enhances insulation, maintaining a stable temperature field. Through-holes allow for the installation of temperature probes and the flow of protective gas, blocking the oxidation reaction between nickel and oxygen atoms, preventing the formation of NiO oxides that could damage the integrity of the γ-Ni metallic crystal bonds, and preventing high-temperature oxidation and embrittlement of the pipe. The device improves insulation efficiency, reduces energy consumption, and ensures that the nickel-based welded pipe undergoes high-temperature heat treatment without oxidation or decarburization, maintaining the integrity of the matrix metallic bonds. In conjunction with the heating unit and heating components, a stable, uniform heating environment is created, ensuring that the recrystallization and solution treatment of the nickel-based alloy are completed in an oxygen-free atmosphere, improving the purity of the microstructure.

[0012] Furthermore, the insulation box is provided with a plurality of wedge-shaped focusing through holes evenly distributed along the circumference. The cross-sectional area of ​​the wedge-shaped focusing through holes gradually decreases from the outside to the inside along the radiation direction, and its central axis is deflected at an angle of 5°-25° with the radial direction of the welded pipe, pointing towards the lower side wall area of ​​the welded pipe; the resistance radiation heating component is installed at the outer large-diameter end of the wedge-shaped focusing through hole.

[0013] The wedge-shaped structure, relying on geometric focusing effect, directionally concentrates infrared radiant heat onto the welded pipe wall; a deflection angle of 5°-25° compensates for the temperature difference due to gravity during continuous pipe transport, ensuring uniform heating at all points along the circumference of the pipe; directional radiant heat enhances the synchronous diffusion of γ-Ni lattice atoms, eliminating circumferential grain boundary energy differences and preventing localized grain coarsening. The circumferential temperature difference of the welded pipe is ≤10℃, significantly improving grain uniformity and eliminating circumferential microstructure differences. In conjunction with the coaxial heating structure and radiant heating components, it greatly improves the utilization rate of radiant heat, solves the problem of uneven circumferential heating during continuous pipe transport, and achieves simultaneous recrystallization throughout the entire circumference.

[0014] Furthermore, the resistance radiation heating assembly is a radially layered composite heating structure, including an outer fast-response resistance wire near the outer wall of the welded pipe and an inner penetrating infrared radiation tube disposed on the outermost layer of the furnace; the outer fast-response resistance wire is made of Fe-Cr-Al alloy; the inner penetrating infrared radiation tube is a high-purity quartz tube with built-in resistance wire.

[0015] The Fe-Cr-Al alloy, being a metallic-bonded crystal, exhibits a rapid surface thermal response rate, enabling quick heating of the welded pipe's outer wall and activating the diffusion of surface γ-Ni atoms. The high-purity quartz tube, a covalent-bonded crystal, possesses strong infrared radiation penetration, allowing direct heating of the welded pipe's central wall region. This achieves synchronous heating of the outer wall and the center of the wall, eliminating the temperature gradient along the thickness of the nickel-based welded pipe and preventing microstructure delamination caused by asynchronous recrystallization of the inner and outer layers. The welded pipe exhibits completely uniform microstructure along its wall thickness, with no difference in grain size between the inner and outer layers, significantly improving its high-temperature creep resistance and mechanical property stability. In conjunction with the resistor component parameters and wedge-shaped focusing structure, radial layered heating matches the thermal conductivity of the nickel-based alloy, achieving rapid surface heating combined with synchronous penetrating heating of the core, maximizing the solid solution strengthening effect.

[0016] Furthermore, the Fe-Cr-Al alloy material has a surface heat load ≥15W / cm², and the high-purity quartz tube emits a peak wavelength of 4-8μm.

[0017] The 4-8μm infrared wavelength resonates highly with the vibrational frequency of the γ-Ni lattice, significantly improving the heat absorption efficiency of lattice atoms and accelerating dislocation annihilation and the solid solution of alloying elements. A surface heat load ≥15W / cm² ensures a rapid heating rate without disrupting radiative heat uniformity, preventing grain boundary cracking caused by thermal shock. Resonant heating allows alloying elements such as Cr, Mo, and Nb to fully dissolve into the γ-Ni matrix, strengthening metallic bonding. More complete alloying element solid solution significantly improves the tensile strength and yield strength of nickel-based welded pipes.

[0018] Furthermore, both the outer fast-response resistance wire and the inner penetrating infrared radiation tube adopt an axial variable pitch winding structure; in the first 1 / 4-1 / 3 length region corresponding to the entrance of the second heating chamber, the resistance wire winding pitch is 1.2-1.5 times the standard pitch, forming a low power density transition zone; in the middle 1 / 3 length region, the standard pitch is used, forming the main heating zone; in the last 1 / 4-1 / 3 length region, the pitch is increased again, forming a temperature fine-tuning zone.

[0019] The variable pitch structure gradient controls power density, with low power in the transition zone to avoid thermal shock from sudden temperature rise after high-frequency heating, preventing cracks in the γ-Ni lattice due to stress abrupt changes. Standard power in the main heating zone ensures uniform temperature, eliminating grain boundary segregation and promoting recrystallization growth. Low power in the fine-tuning zone stabilizes the temperature, preventing abnormal grain growth during cooling. Gradient temperature control aligns with the atomic diffusion kinetics of nickel-based alloys, slowly releasing residual stress. The welded pipe exhibits uniform temperature along its entire axial length, preventing thermal stress cracking and improving grain size control.

[0020] Secondly, this application provides an online heat treatment process for nickel-based welded pipes used in solar thermal power plants. It includes the following continuously implemented online steps: S1 Continuous conveying and atmosphere pre-replacement: The nickel-based welded pipe to be treated is pulled through each processing unit sequentially at a set uniform speed, while a protective gas is introduced into the heating chamber to replace the air inside and prevent high-temperature oxidation of the nickel-based welded pipe; S2 High-frequency induction rapid heating: The high-frequency heating temperature is set to 1000-1100℃, and the nickel-based welded pipe to be treated is pulled through the high-frequency induction heating unit to rapidly complete recrystallization, resulting in a recrystallized nickel-based welded pipe; S3 Resistance radiation homogenization and heat preservation: The radiation heating temperature is set to 1120-1150℃, and the recrystallized nickel-based welded pipe is continuously pulled through the resistance radiation homogenization and heat preservation unit to eliminate structural stress and homogenize grain size, resulting in a heat-preserved nickel-based welded pipe; S4 Rapid quenching and cooling: The heat-preserved nickel-based welded pipe is continuously pulled through a rapid cooling unit, and rapid quenching and cooling are achieved through water cooling, controlling the cooling rate at 150-200℃ / s to lock in a uniform microstructure.

[0021] Furthermore, the continuous conveying speed of the welded pipe in S1 is 0.2~5.0m / min, and the control accuracy of the conveying speed is within ±0.1m / min.

[0022] The beneficial effects of this application are: Three-section coaxial connection, continuous and efficient: high-frequency induction, resistance radiation and rapid cooling units are coaxially connected, which is suitable for continuous conveying of welded pipes and realizes online integrated heat treatment, improving production efficiency by more than 3 times compared with offline process. Precise and uniform heating, stable structure: high-frequency induction rapid heating ensures cycle time, and the circumferential uniform arrangement of resistance radiation + wedge-shaped focusing structure eliminates the temperature difference between the circumference and wall thickness of the welded pipe, resulting in uniform grain size. Parameters are controllable and adjustable, and performance meets standards: Variable pitch heating structure and precise cooling rate control ensure that the nickel-based welded pipe eliminates welding stress, and the mechanical properties such as tensile strength, yield strength and elongation fluctuate little, meeting the high-temperature service requirements of solar thermal power plants. Durable and energy-efficient structure: Layered insulated box + infrared radiation heating improves heat utilization; HRE and Fe-Cr-Al alloy resistance wires are high temperature resistant and have a long service life, reducing equipment maintenance costs. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the high-frequency heating section; Figure 2 This is a schematic diagram of the resistance radiation heating part; Figure 3 Comparative Example 2-1 shows the metallographic structure after heat treatment using conventional heat treatment processes; Figure 4 Therefore, the invention device process embodiment 2-1 heat treatment metallographic structure. Detailed Implementation

[0024] To further aid in understanding the technical solution of this invention, several specific implementation examples are provided below to describe the technical solution of this invention in more detail. All of these described embodiments are only some embodiments of this invention, and not all of them. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments; and the reaction devices, monomer compounds, etc. involved in the following embodiments are all commercially available.

[0025] The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0026] Examples of embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions. The embodiments described with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0027] Example and Comparative Examples: Raw Material / Equipment Parameters The welded pipe to be processed: Inconel 625 nickel-based welded pipe for solar thermal power plants, with an outer diameter of Φ89mm and a wall thickness of 4mm; High-frequency heating power supply: 120kW power, 20-50kHz frequency; Resistance radiation heating components: HRE spiral resistance wire, Fe-Cr-Al fast response resistance wire, high-purity quartz infrared radiation tube; Protective gas: 99.99% pure argon; Cooling system: Closed-loop water-cooled unit, water temperature 25±2℃.

[0028] Example of an online heat treatment device for nickel-based welded pipes used in solar thermal power plants Device Example 1-1 The structure defined by claims 1-2 is adopted: High-frequency induction heating unit: copper tube heating resistance wire wound with equal pitch into a high-temperature resistant quartz tube, the inner diameter of the first heating chamber is Φ95mm; Resistance radiation uniform temperature insulation unit: The insulation box is a layered structure of refractory bricks, with 12 sets of resistance radiation heating components built in, each with a power of 36kW; the spiral resistance wire has an outer diameter of Φ46mm and an inner diameter of Φ37mm; the insulating ceramic tube has an outer diameter of Φ35mm, an inner diameter of Φ25mm, and a length of 680mm; standard pitch. Rapid cooling unit: coaxial water cooling jacket, with a 3mm gap between the inner wall and the welded pipe.

[0029] Device Examples 1-2 Based on Example 1-1, a wedge-shaped focusing through hole is added, with the through hole deflected at a radial angle of 15° from the welded pipe, and 12 holes are evenly distributed circumferentially.

[0030] Device Examples 1-3 Based on Examples 1-2, a radially layered composite heating structure is adopted: an outer layer of Fe-Cr-Al fast-response resistance wire and an inner layer of high-purity quartz infrared radiation tube with a peak emission wavelength of 6μm.

[0031] Device Examples 1-4 Based on Examples 1-3, axial variable pitch winding is adopted: the pitch of the first 1 / 3 region is 1.2 times the standard pitch, the middle 1 / 3 is the standard pitch, and the last 1 / 3 is 1.2 times the standard pitch.

[0032] Device Examples 1-5 The number of resistance radiation heating components was adjusted to 24 sets, with a power of 24kW per set, and the rest were the same as in Examples 1-4.

[0033] Device Examples 1-6 The number of resistance radiation heating components was adjusted to 36 sets, with a power of 48kW per set, and the rest were the same as in Examples 1-4.

[0034] Device Examples 1-7 The deflection angle of the wedge-shaped focusing through-hole is adjusted to 5°, and the rest is the same as in Examples 1-4.

[0035] Device Examples 1-8 The deflection angle of the wedge-shaped focusing through-hole is adjusted to 25°, and the rest is the same as in Examples 1-4.

[0036] Comparative Example 1-1 It adopts a single high-frequency induction heating and a non-resistive radiation temperature equalization and heat preservation unit, and the rest is the same as in Example 1-1.

[0037] Comparative Examples 1-2 It adopts a single resistance radiation heating method and has no high-frequency induction heating unit. The rest is the same as in Example 1-1.

[0038] Online heat treatment process examples Using the above-described apparatus in Examples 1-1 to 1-8 and Comparative Examples 1-1 to 1-2, and with corresponding heat treatment processes, the process parameters are as follows: Process Example 2-1 (corresponding to Device Example 1-1) S1: Conveying speed 1.0 m / min, argon protection; S2: High-frequency heating temperature 1050℃; S3: Radiant heating temperature 1130℃; S4: Cooling rate 180℃ / s.

[0039] Process Example 2-2 (corresponding to Device Example 1-2) The process parameters are the same as in Example 2-1.

[0040] Process Examples 2-3 (corresponding to Device Examples 1-3) The process parameters are the same as in Example 2-1.

[0041] Process Examples 2-4 (corresponding to Device Examples 1-4) The process parameters are the same as in Example 2-1.

[0042] Process Examples 2-5 (corresponding to Device Examples 1-4) The conveying speed is 2.0 m / min, and the other parameters are the same as in Example 2-1.

[0043] Process Examples 2-6 (corresponding to Device Examples 1-4) The conveying speed is 0.5 m / min, and the other parameters are the same as in Example 2-1.

[0044] Process Examples 2-7 (corresponding to Device Examples 1-4) The high-frequency heating temperature is 1000℃, the radiation heating temperature is 1120℃, and the other parameters are the same as in Example 2-1.

[0045] Process Examples 2-8 (corresponding to Device Examples 1-4) The high-frequency heating temperature is 1100℃, the radiation heating temperature is 1150℃, and the other parameters are the same as in Example 2-1.

[0046] Process Examples 2-9 (corresponding to Device Examples 1-5) The process parameters are the same as in Example 2-1.

[0047] Process Examples 2-10 (corresponding to Device Examples 1-6) The process parameters are the same as in Example 2-1.

[0048] Process Examples 2-11 (corresponding to Device Examples 1-7) The process parameters are the same as in Example 2-1.

[0049] Process Examples 2-12 (corresponding to Device Examples 1-8) The process parameters are the same as in Example 2-1.

[0050] Process Comparison Example 2-1 (corresponding to Equipment Comparison Example 1-1) Only high-frequency induction heating at 1050℃, air cooling, cooling rate 20℃ / s, the rest is the same as in Example 2-1.

[0051] Process Comparison Example 2-2 (corresponding to Equipment Comparison Example 1-2) Only resistance radiation heating is used at 1130℃, and water cooling rate is 80℃ / s. The rest is the same as in Example 2-1.

[0052] Performance testing According to national standards, heat-treated nickel-based welded pipes are tested to verify their microstructure and mechanical properties. The test items and reference standards are as follows: Grain size: GB / T6394-2017 Method for determination of average grain size of metals; Mechanical properties at room temperature: GB / T228.1-2010 Metallic materials, tensile test, room temperature test method (tensile strength Rm, yield strength Rp0.2, elongation after fracture A); Brinell hardness: GB / T231.1-2018 Metallic materials Brinell hardness test; Grain size uniformity: Six points around the welded pipe and the inner and outer layers of the wall thickness were tested to calculate the grain size range.

[0053] Test results (Table 1) Table 1

[0054] Analysis of the reasons for performance differences The device structure affects the implementation of examples 2-4, which use a wedge-shaped focusing + layered composite + variable pitch heating structure. The radiant heat is precisely focused on the welded pipe, resulting in uniform temperature in the circumferential direction and wall thickness, with a grain size difference of only 0.5 grade, and optimal mechanical properties. In contrast, the single heating method in the comparison example has large temperature fluctuations, dispersed grain size, and a significant decrease in performance.

[0055] Process parameters affect the performance of Examples 2-1 to 2-4, which are matched with 1050℃ high-frequency heating + 1130℃ uniform holding + 180℃ / s rapid cooling, resulting in full recrystallization and homogenization of the nickel-based alloy; Examples 2-7 to 2-8 have slightly worse performance, with insufficient cooling rate, coarse grains, residual stress not eliminated, and mechanical properties not meeting the standards.

[0056] The conveying speed affects the performance of Examples 2-5 and 2-6. When the speed is within the range of 0.2-5.0 m / min, the heat preservation time is sufficient and the performance is stable. If the speed exceeds the range, the heating / heat preservation will be insufficient and the uniformity of the grain size will decrease.

[0057] Analysis of test results The nickel-based welded tubes produced by the device and process described in this application have uniform grain size and excellent mechanical properties, and all indicators meet the requirements for use in solar thermal power plants. Examples 2-4 are the optimal solutions, with the device structure and process parameters fully matching the scope defined in the claims, and exhibiting the best organizational and performance stability; The comparative example shows a significant performance degradation due to the lack of core structure / parameters, demonstrating the inventiveness and practicality of the technical solution presented in this application.

[0058] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. An online heat treatment device for nickel-based welded pipes used in solar thermal power plants, characterized in that, Along the continuous conveying direction of the welded pipe, a high-frequency induction heating unit, a resistance radiation temperature equalization and heat preservation unit, and a rapid cooling unit are connected coaxially in sequence. The high-frequency induction heating unit includes a high-frequency heating power supply, a copper tube heating resistance wire, and a high-temperature resistant quartz tube; the two ends of the copper tube heating resistance wire are electrically connected to the high-frequency heating power supply, the main body of the copper tube heating resistance wire is wound around the outer wall of the high-temperature resistant quartz tube with equal pitch, and the inner cavity of the high-temperature resistant quartz tube forms a first heating chamber for the continuous passage of nickel-based welded pipes. The resistive radiation uniform temperature insulation unit includes an insulation box, insulation cotton set in the assembly margin space of the insulation box, and 1-36 sets of resistive radiation heating components evenly arranged inside the insulation box. The heat preservation box has a second heating chamber that is coaxially connected to the heating chamber of the high-frequency induction heating unit, and the resistance radiation heating components are uniformly arranged around the second heating chamber in the circumference.

2. The online heat treatment device for nickel-based welded pipes used in solar thermal power plants according to claim 1, characterized in that, The resistance radiation heating component has a heating power of 24-48kw and includes a spiral resistance wire made of HRE material and an insulating ceramic tube inside the spiral resistance wire. The spiral resistance wire has an outer diameter of Φ46±5mm and an inner diameter of Φ37±5mm; the insulating ceramic tube has an outer diameter of Φ35±5mm, an inner diameter of Φ25±5mm, and a length of 680±180mm.

3. The online heat treatment device for nickel-based welded pipes used in solar thermal power plants according to claim 1, characterized in that, The insulated box is constructed of refractory bricks to form a layered structure, and the outer surface of the layered structure is covered with high-temperature resistant material. The insulated box has at least one through hole.

4. The online heat treatment device for nickel-based welded pipes used in solar thermal power plants according to claim 1, characterized in that, The insulation box has multiple wedge-shaped focusing through holes evenly distributed circumferentially. The cross-sectional area of ​​the wedge-shaped focusing through holes gradually decreases from the outside to the inside along the radiation direction, and its central axis is deflected at an angle of 5°-25° with the radial direction of the welded pipe, pointing towards the lower side wall area of ​​the welded pipe. The resistance radiation heating component is installed at the large-diameter end of the outer side of the wedge-shaped focusing through hole.

5. The online heat treatment device for nickel-based welded pipes used in solar thermal power plants according to claim 2, characterized in that, The resistance radiation heating assembly is a radially layered composite heating structure, including an outer fast-response resistance wire near the outer wall of the welded pipe and an inner penetrating infrared radiation tube disposed on the outermost layer of the furnace; the outer fast-response resistance wire is made of Fe-Cr-Al alloy; the inner penetrating infrared radiation tube is a high-purity quartz tube with built-in resistance wire.

6. The online heat treatment device for nickel-based welded pipes used in solar thermal power plants according to claim 5, characterized in that, The Fe-Cr-Al alloy material has a surface heat load ≥15W / cm², and the high-purity quartz tube emits a peak wavelength of 4-8μm.

7. The online heat treatment device for nickel-based welded pipes used in solar thermal power plants according to claim 3, characterized in that, Both the outer fast-response resistance wire and the inner penetrating infrared radiation tube adopt an axial variable pitch winding structure. In the first 1 / 4 to 1 / 3 of the length region corresponding to the entrance of the second heating chamber, the resistance wire winding pitch is 1.2 to 1.5 times the standard pitch, forming a low power density transition zone. In the middle 1 / 3 of the length region, the standard pitch is used, forming the main heating zone. In the last 1 / 4 to 1 / 3 of the length region, the pitch is increased again, forming a temperature fine-tuning zone.

8. An online heat treatment process using the online heat treatment apparatus for nickel-based welded pipes for solar thermal power plants according to any one of claims 1-7, characterized in that, This includes the following steps implemented continuously online: S1 Continuous Conveying and Atmosphere Pre-replacement: The nickel-based welded pipe to be processed is pulled through each processing unit sequentially at a set uniform speed; S2 High-Frequency Induction Rapid Heating: Set the high-frequency heating temperature to 1000-1100℃, and pull the nickel-based welded pipe to be processed through the high-frequency induction heating unit to obtain a recrystallized nickel-based welded pipe. S3 resistance radiation uniform temperature insulation: The radiation heating temperature is set to 1120-1150℃, and the continuously drawn recrystallized nickel-based welded pipe is heat-insulated through the resistance radiation uniform temperature insulation unit. S4 Rapid Quenching and Cooling: The heat-insulated nickel-based welded pipe is continuously pulled through the rapid cooling unit, and rapid quenching and cooling is achieved by water cooling, with the cooling rate controlled at 150-200℃ / s.

9. The online heat treatment process of the online heat treatment device for nickel-based welded pipes for solar thermal power plants according to claim 8, characterized in that, The continuous conveying speed of the welded pipe in S1 is 0.2~5.0m / min, and the control accuracy of the conveying speed is within ±0.1m / min.

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