A method and system for local heat treatment of hot press tank welds

Abstract

The present application relates to the technical field of metal heat treatment, and particularly relates to a kind of local heat treatment methods of hot press tank weld, comprising the following steps: S1, tool preparation: prepare tank chain type flexible heat conduction tool, the tank chain type flexible heat conduction tool includes multiple chain molybdenum pieces, the chain molybdenum piece is articulated spliced by shaft, and V-shaped arch ridge is arranged on the side of weld towards the chain molybdenum piece;S2, tool in place fixation: the tank chain type flexible heat conduction tool is arranged in the weld position, so that V-shaped arch ridge is aligned with fillet weld sharp angle and is pressed tightly and is combined with base material, and the gap between tool and base material, tool articulation gap is filled with high-temperature fiber pad to reduce contact thermal resistance.The present application uses tank chain type flexible heat conduction tool as heat conduction transition piece, can be flexibly spliced and assembled according to the length of weld, and articulated structure cooperates with V-shaped arch ridge to be able to self-adapt and fit narrow space variable-curvature circumferential fillet weld, solve the problem that traditional rigid heat conduction bridge cannot adapt to narrow sharp angle weld.

Description

Technical Field

[0001] This invention relates to the field of metal heat treatment technology, and specifically to a method for local heat treatment of weld seams in autoclaves. Background Technology

[0002] Large autoclaves are crucial equipment for manufacturing aerospace composite components, and the weld connecting the crown cap and the clamp-tooth flange is a critical load-bearing weld. According to relevant standards and design requirements, this type of weld typically requires post-weld heat treatment (PWHT) after welding to reduce residual welding stress, improve weld microstructure, enhance the overall mechanical properties of the joint, and ensure the long-term safe operation of the equipment.

[0003] Currently, the main method for local heat treatment of welds in large pressure vessels is to directly attach resistance heating elements to the weld surface. The heating elements are evenly laid out within a specified width on both sides of the weld, and are supplemented with insulation cotton, a temperature control system, and thermocouples for closed-loop control to achieve the specified heating rate, holding temperature, and cooling rate, thereby completing the post-weld heat treatment.

[0004] For ordinary cylindrical circumferential seams, longitudinal seams, and nozzle welds, this method is mature, has high thermal efficiency, and precise temperature control, and is therefore widely used in the pressure vessel manufacturing industry. Furthermore, for areas with obstructions or requiring a certain amount of heat transfer, existing technologies also use rigid metal heat-conducting blocks or rigid heat-conducting bridges (such as copper blocks or steel heat-conducting bridges) as transition components to conduct the heat from the heating element to the weld seam where it cannot be directly attached.

[0005] However, rigid thermal bridges can only fit regular planes or large curvature transition surfaces, making it difficult to adapt to fillet welds with narrow angles, varying angles, or varying curvatures. At the connection between the crown end cap and the clamp-tooth flange of a large autoclave, the complex tooth structure of the clamp-tooth flange and the weld located in a narrow, enclosed space prevent the heating element from being directly attached to the weld area, making it difficult to implement existing local heat treatment methods.

[0006] Therefore, it is necessary to invent a method for local heat treatment of the weld seam of an autoclave to solve the above problems. Summary of the Invention

[0007] The purpose of this invention is to provide a method for local heat treatment of weld seams in autoclaves. By using a tank-chain type flexible heat-conducting tool, heat is conducted to the weld seam in a narrow, enclosed space, thereby achieving precise temperature control throughout the heat treatment process of the weld seam in the narrow space and improving the quality of post-weld heat treatment.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] A method for local heat treatment of weld seams in an autoclave is provided, comprising the following steps:

[0010] S1. Tooling preparation: Prepare a tank chain flexible heat conduction tooling, which includes multiple chain molybdenum sheets. The chain molybdenum sheets are hinged and spliced ​​by pin shafts, and the chain molybdenum sheets are provided with V-shaped arch ridges on the side facing the weld.

[0011] S2. Fixture positioning and fixing: Arrange the tank chain type flexible heat-conducting fixture at the weld position, align the V-shaped arch ridge with the corner weld tip and press it tightly against the base material. Fill the gap between the fixture and the base material and the hinge gap of the fixture with high-temperature resistant fiber pads to reduce contact thermal resistance.

[0012] S3. Heating and insulation arrangement: Flexible resistance heating elements are laid on the outside of the tank chain type flexible heat-conducting tooling, and a high-temperature resistant insulation layer is wrapped around the flexible resistance heating elements.

[0013] S4. Temperature measurement and heat treatment operation: Multiple thermocouples are arranged in the center of the weld corner, weld toe and surrounding area. A zoned temperature control system is adopted, and the power of each heating zone is independently adjusted according to the thermocouple feedback signal to execute preset heat treatment processes such as heating, holding and cooling.

[0014] S5. Post-treatment removal: After heat treatment, wait for the workpiece to cool down to a safe temperature, then remove the insulation layer, flexible resistance heating element, and tank chain flexible heat conduction tooling.

[0015] As a preferred embodiment of a local heat treatment method for the weld of an autoclave, the weld is a circumferential fillet weld in the narrow space between the crown end cap and the clamping flange of a large autoclave.

[0016] As a preferred embodiment of a local heat treatment method for the weld seam of an autoclave, the tank chain-type flexible heat-conducting tooling is fixed to the workpiece by heat-resistant buckles and high-temperature metal wires; the high-temperature resistant fiber pad is an aluminum silicate fiber pad; and the high-temperature resistant insulation layer consists of at least two layers of insulation material.

[0017] As a preferred embodiment of a local heat treatment method for the weld seam of an autoclave, the aluminum silicate fiber pad has a thickness of 2-3 mm; the total thickness of the high-temperature insulation layer is not less than 50 mm; and the high-temperature metal wire is a Φ0.8~1.2 mm high-temperature iron wire.

[0018] As a preferred method for local heat treatment of the weld seam of an autoclave, in step S4, the temperature difference between the weld seam tip and the temperature measuring points on both sides is controlled to be ≤15℃ during the heat treatment process; after the heat treatment is completed, the tooling is removed after the overall temperature drops below 300℃.

[0019] As a preferred embodiment of a local heat treatment method for weld seams in an autoclave, the chain-type molybdenum sheet is a pure molybdenum sheet with a purity ≥99.95%; the pin shaft is made of TZM molybdenum alloy or nickel-based high-temperature alloy; the pure molybdenum sheet has a thickness of 4-6mm, a width of 40-80mm, a single section length of 30-50mm, and a relative hinge angle of ≥±15° for a single section of molybdenum sheet; the pin shaft diameter is 5-8mm; the included angle of the V-shaped arch rib is adapted to the bevel angle of the fillet weld, with an applicable angle range of 30°-120°, and the top of the V-shaped arch rib is provided with a radius of R1~R2mm.

[0020] A local heat treatment system for weld seams in an autoclave includes a tank-chain type flexible heat-conducting tooling, a flexible resistance heating device, a high-temperature insulation system, a multi-point temperature detection system, a zoned temperature control system, and a fixing and clamping mechanism.

[0021] The tank chain-type flexible heat-conducting tooling is installed between the toothed flange and the crown end cap, and fits tightly against the weld area;

[0022] The flexible resistance heating device is fixedly installed on the outside of the tank chain-type flexible heat-conducting tooling.

[0023] The high-temperature insulation system covers the entire heating area of ​​the flexible resistance heating device.

[0024] The multi-point temperature detection system includes multiple thermocouples, which are respectively arranged at the center of the weld corner, the weld toes on both sides of the weld, and the outer area of ​​the weld.

[0025] As a preferred embodiment of a local heat treatment system for weld seams in an autoclave, the zoned temperature control system is a zoned temperature control cabinet, which is used to receive temperature signals collected by thermocouples and independently adjust the output power of each heating zone.

[0026] As a preferred embodiment of a local heat treatment system for the weld seam of an autoclave, the fixing and clamping mechanism includes heat-resistant buckles and high-temperature iron wires, which are used to press and fix the tank chain-type flexible heat-conducting tooling at the weld seam position of the workpiece.

[0027] The beneficial effects of this invention are as follows: This invention uses a tank chain-type flexible heat-conducting tooling as a heat-conducting transition component, which can be flexibly spliced ​​and assembled according to the weld length. The hinged structure combined with the V-shaped arch ridge can adaptively fit the circumferential fillet weld with varying curvature in narrow spaces, solving the problem that traditional rigid heat-conducting bridges cannot adapt to narrow sharp-corner welds. The tooling uses high-purity pure molybdenum sheets combined with pins that match thermal expansion, making it less prone to deformation and hydrogen embrittlement in high-temperature environments. The modular structure makes disassembly and maintenance convenient.

[0028] By using indirect heat conduction through tooling, the limitation that heating elements cannot be directly placed in the narrow, enclosed space of the weld between the autoclave crown and the clamp flange is overcome; in conjunction with aluminum silicate fiber pads, contact thermal resistance is eliminated, heat transfer efficiency is improved, and the weld can reach the heat treatment process temperature. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments of the present invention will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0030] Figure 1 This is a schematic diagram of a single molybdenum sheet structure as described in this invention.

[0031] In the picture:

[0032] 1. Chain-type molybdenum sheet. Detailed Implementation

[0033] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0034] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual images. They should not be construed as limiting the scope of this patent. To better illustrate the embodiments of the present invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0035] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "inner," and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present patent. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0036] In the description of this invention, unless otherwise explicitly specified and limited, the term "connection" or similar designation indicating a connection between components should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral part; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0037] Existing local heat treatment methods mainly have the following problems:

[0038] 1. Due to the obstruction of the toothed flange structure, the heating element cannot cover the weld and heat-affected zone, and the heating heat cannot be directly applied to the weld.

[0039] 2. If the heating element is placed in an adjacent installation area, the weld area will heat up slowly due to the long heat conduction distance and the large temperature gradient, making it difficult to reach the heat treatment temperature specified in the process.

[0040] 3. Uneven heating at different locations in the weld can easily lead to local underheating or overheating, resulting in inconsistent microstructure and properties, which affects the quality of weld heat treatment.

[0041] 4. Traditional single-point temperature measurement methods cannot accurately reflect the actual temperature of the weld in a narrow space, resulting in low temperature control accuracy and making it easy for the heat treatment process to deviate from the process requirements.

[0042] To address the above issues, refer to Figure 1 This invention provides a method for local heat treatment of weld seams in autoclaves, comprising the following steps:

[0043] S1. Tooling preparation: Prepare a tank chain type flexible heat conduction tooling, which includes multiple chain molybdenum sheets 1. The chain molybdenum sheets 1 are hinged and spliced ​​by pin shafts, and the chain molybdenum sheets 1 have a V-shaped arch ridge on the side facing the weld.

[0044] S2. Fixture positioning and fixing: Arrange the tank chain type flexible heat-conducting fixture at the weld position, align the V-shaped arch ridge with the corner weld tip and press it tightly against the base material. Fill the gap between the fixture and the base material and the hinge gap of the fixture with high-temperature resistant fiber pads to reduce contact thermal resistance.

[0045] S3. Heating and insulation arrangement: Flexible resistance heating elements are laid on the outside of the tank chain type flexible heat-conducting tooling, and a high-temperature resistant insulation layer is wrapped around the flexible resistance heating elements.

[0046] S4. Temperature measurement and heat treatment operation: Multiple thermocouples are arranged in the center of the weld corner, weld toe and surrounding area. A zoned temperature control system is adopted, and the power of each heating zone is independently adjusted according to the thermocouple feedback signal to execute preset heat treatment processes such as heating, holding and cooling.

[0047] S5. Post-treatment removal: After heat treatment, wait for the workpiece to cool down to a safe temperature, then remove the insulation layer, flexible resistance heating element, and tank chain flexible heat conduction tooling.

[0048] In step S2, the number of splicing sections can be calculated based on the actual length of the weld. Multiple chain molybdenum sheets 1 are hinged together by pins to assemble a tank chain flexible heat-conducting tooling that matches the length of the weld. The number of splicing sections n = L ÷ single section length (rounded down) is calculated based on the weld length L. The chain molybdenum sheets 1 are spliced ​​together by pins to form a tank chain flexible heat-conducting tooling of the required length.

[0049] The weld is a circumferential fillet weld in the narrow space between the crown of a large autoclave and the clamp flange.

[0050] The tank-chain type flexible heat-conducting tooling is pressed and fixed to the workpiece by heat-resistant buckles and high-temperature metal wires; the high-temperature resistant fiber pad is an aluminum silicate fiber pad; the high-temperature resistant insulation layer is composed of at least two layers of insulation material.

[0051] The aluminum silicate fiber pad has a thickness of 2-3 mm; the total thickness of the high-temperature insulation layer is not less than 50 mm; and the high-temperature metal wire is a Φ0.8~1.2 mm high-temperature iron wire.

[0052] In step S4, during the heat treatment process, the temperature difference between the weld tip and the temperature measuring points on both sides is controlled to be ≤15℃; after the heat treatment is completed, the tooling is removed only after the overall temperature drops below 300℃.

[0053] The chain-type molybdenum sheet 1 is a pure molybdenum sheet with a purity of ≥99.95%; the pin shaft is made of TZM molybdenum alloy or nickel-based high-temperature alloy; the pure molybdenum sheet has a thickness of 4-6mm, a width of 40-80mm, a single section length of 30-50mm, and a relative hinge angle of ≥±15° for a single section of molybdenum sheet; the pin shaft diameter is 5-8mm; the included angle of the V-shaped arch rib is adapted to the bevel angle of the fillet weld, and the applicable included angle range is 30°-120°, and the top of the V-shaped arch rib is provided with a radius of R1~R2mm.

[0054] The tooling is made of pure molybdenum sheets with a purity of ≥99.95%, and the pins are made of TZM molybdenum alloy or nickel-based high-temperature alloy. The thermal expansion is matched, and the hinge is not easy to jam at high temperatures. The pure molybdenum material does not deform or embrittle under long-term heat preservation at 600℃, and its high-temperature stability is better than that of rigid heat-conducting parts made of copper and steel. The modular splicing structure allows for individual replacement of damaged sections. The tooling can be disassembled and stored, and has a high reusability rate.

[0055] A local heat treatment system for weld seams in an autoclave includes a tank-chain type flexible heat-conducting tooling, a flexible resistance heating device, a high-temperature insulation system, a multi-point temperature detection system, a zoned temperature control system, and a fixing and clamping mechanism.

[0056] The tank chain-type flexible heat-conducting tooling is installed between the toothed flange and the crown end cap, and fits tightly against the weld area;

[0057] The flexible resistance heating device is fixedly installed on the outside of the tank chain-type flexible heat-conducting tooling.

[0058] The high-temperature insulation system covers the entire heating area of ​​the flexible resistance heating device.

[0059] The multi-point temperature detection system includes multiple thermocouples, which are respectively arranged at the center of the weld corner, the weld toes on both sides of the weld, and the outer area of ​​the weld.

[0060] At least four thermocouples are placed at one point at the center of the weld corner, one point at each of the weld toes on both sides, and one point on the periphery. Each temperature measuring point is connected to a zoned temperature control cabinet. After the heat treatment program is started, the temperature control system controls the heating power according to the preset process curve, realizing automatic control of the entire process of heating, holding, and cooling. When the local temperature deviates from the set value, the output power of the corresponding heating zone is automatically adjusted to keep the temperature measuring points of the weld within the allowable temperature difference range (relying on the excellent thermal conductivity of molybdenum to balance the weld temperature difference, the temperature difference between the corner and the sides can be controlled within ≤15℃).

[0061] At least four thermocouples are arranged at the center of the weld corner, the weld toes on both sides, and the periphery to collect the true weld temperature at multiple points. This is different from the drawback of traditional single-point temperature measurement, which cannot reflect the true temperature inside the slit. The zoned temperature control cabinet independently adjusts the power of each heating zone, which can control the temperature difference between the weld corner and the temperature measurement points on both sides to ≤15℃. Compared with the 40-60℃ temperature difference at the corner of the traditional rigid heat-conducting bridge, this significantly reduces the temperature gradient, basically eliminates the low temperature zone at the corner, avoids local underheating and overheating of the weld, and ensures that the overall temperature field of the weld is uniform and stable.

[0062] The zoned temperature control system is a zoned temperature control cabinet, which is used to receive temperature signals collected by thermocouples and independently adjust the output power of each heating zone.

[0063] The fixing and clamping mechanism includes heat-resistant buckles and high-temperature iron wire, which are used to press and fix the tank chain-type flexible heat-conducting tooling at the weld position of the workpiece.

[0064] Tooling quantification parameters;

[0065] The key structural parameters of the pure molybdenum tank-type flexible heat-conducting tooling are as follows (these parameters can be adjusted within the range according to the weld specifications during implementation; recommended values ​​are marked in parentheses):

[0066]

[0067] Compared to traditional rigid thermal bridges, a practical comparison of the temperature difference at sharp corners was conducted:

[0068] Under the same working condition of holding at 600℃ for 2 hours, for the same narrow-angle fillet weld specimen, the traditional rigid thermal bridge (copper / steel rigid bridge) and the pure molybdenum tank chain flexible thermal conductive tooling of the present invention were compared. The results are shown in the table below (the data in the table are engineering verification demonstration values, and the actual test data should prevail during implementation):

[0069]

[0070] Example 1;

[0071] Taking the weld connecting the crown cap and the clamp-tooth flange of a large autoclave as an example, the weld is a narrow-angled, variable-curvature circumferential fillet weld. The heat treatment process involves heating to 600℃, holding for 2 hours, and then slowly cooling. The specific implementation steps are as follows.

[0072] (1) Tooling preparation and inspection. Select the specifications of molybdenum sheet according to the weld curvature and bevel angle (thickness 4~6mm, width 40~80mm, single section length 30~50mm, V-shaped arch rib fitting angle 30°~120°); before use, check the molybdenum sheet and pin (TZM molybdenum alloy or nickel-based high temperature alloy, diameter 5~8mm) section by section to see if they are intact, and clean the oil and oxide scale on the contact surface between the workpiece and the tooling.

[0073] (2) Splicing of heat-conducting fixtures. Calculate the number of splicing sections n = L ÷ single section length (rounded down) according to the weld length L. Then, splice the molybdenum sheets into a tank chain type flexible heat-conducting fixture of the required length by hinged pin shafts.

[0074] (3) Alignment and Fixing. Align the V-shaped arch of the tooling with the sharp corner of the small-angle fillet weld and press it against the base material, with the two wings fitting against both sides of the weld; use heat-resistant clips and Φ0.8~1.2mm high-temperature iron wire (or stainless steel wire) to fix it in sections, so that the tooling and the weld area are in full contact and the contact thermal resistance is reduced. Fill the hinge gap and the gap between the tooling and the base material with a 2~3mm thick aluminum silicate fiber pad to eliminate the thermal resistance of the air gap.

[0075] (4) Heating and insulation arrangement. Flexible resistance heating elements are laid out completely on the outside of the tooling and evenly arranged along the weld seam; ceramic fiber blankets, aluminum silicate insulation cotton, etc. are wrapped around the outside of the heating zone in sequence, with no less than 2 insulation layers and a total thickness of no less than 50mm, forming a closed insulation layer.

[0076] (5) Multi-point temperature measurement and zoned temperature control. At least four thermocouples are arranged at one point at the center of the weld corner, one point at each of the weld toes on both sides, and one point on the periphery. Each temperature measurement point is connected to a zoned temperature control cabinet. After the heat treatment program is started, the temperature control system controls the heating power according to the preset process curve to achieve automatic control of the entire process of heating, holding and cooling. When the local temperature deviates from the set value, the output power of the corresponding heating zone is automatically adjusted so that the temperature measurement points of the weld are always kept within the allowable temperature difference range (relying on the excellent thermal conductivity of molybdenum to balance the temperature difference of the weld, the temperature difference between the corner and the sides can be controlled within ≤15℃).

[0077] (6) Dismantling and Storage. After heat treatment, the temperature is slowly reduced according to the process. When the overall temperature drops below 300℃, the insulation, heaters and tooling are removed layer by layer. After cleaning, the materials are gently placed and stored. Throughout the process, the molybdenum material is strictly prohibited from being exposed to high-temperature air, from being dismantled and struck at high temperatures, and from being excessively bent.

[0078] (7) Quality Inspection. The weld was subjected to hardness testing, non-destructive testing (PT), and related performance verification. The results of this embodiment show that the weld structure is uniform, the residual stress is effectively reduced, and all properties meet the design and specification requirements, verifying that this method can achieve stable and reliable local heat treatment of the weld under the special narrow space conditions of a large autoclave.

[0079] This invention uses a tank-chain type flexible heat-conducting tooling as a heat-conducting transition component, which can be flexibly spliced ​​and assembled according to the weld length. The hinged structure, combined with the V-shaped arch ridge, can adaptively fit the circumferential fillet weld with varying curvature in narrow spaces, solving the problem that traditional rigid heat-conducting bridges cannot adapt to narrow, sharp-corner welds. The tooling uses high-purity pure molybdenum sheets with matching pins for thermal expansion, making it less prone to deformation and hydrogen embrittlement in high-temperature environments. The modular structure makes disassembly and maintenance convenient.

[0080] By using indirect heat conduction through tooling, the limitation that heating elements cannot be directly placed in the narrow, enclosed space of the weld between the autoclave crown and the clamp flange is overcome; in conjunction with aluminum silicate fiber pads, contact thermal resistance is eliminated, heat transfer efficiency is improved, and the weld can reach the heat treatment process temperature.

[0081] By using multi-point thermocouples to collect the real temperature of the weld at multiple locations and using zoned temperature control cabinets to independently adjust the power of each heating zone, the temperature difference between the weld tip and the temperature measurement points on both sides can be controlled within ≤15℃, effectively eliminating the low temperature zone at the tip, reducing the temperature gradient of the weld, avoiding local overheating or underheating of the weld, and ensuring a uniform and stable heat treatment temperature field.

[0082] The entire process requires no modification to the equipment itself and can be implemented directly on-site. The entire heat treatment process is automatically controlled in a closed loop. The tooling must be cooled to 300℃ before it can be removed, ensuring safe and controllable operation. It effectively improves the quality of post-weld heat treatment of critical welds, reduces residual welding stress, and enhances the manufacturing quality and service reliability of large autoclaves. It can also be extended to the local heat treatment of similar special welds on other pressure vessels.

[0083] It should be stated that the above-described specific embodiments are merely preferred embodiments of the present invention and the technical principles employed. Those skilled in the art should understand that various modifications, equivalent substitutions, and variations can be made to the present invention. However, such variations, as long as they do not depart from the spirit of the present invention, should be within the scope of protection of the present invention. Furthermore, some terminology used in this specification and claims is not limiting, but merely for ease of description.

Claims

1. A method for local heat treatment of weld seams in an autoclave, characterized in that: Includes the following steps: S1. Tooling preparation: Prepare a tank chain flexible heat conduction tooling, which includes multiple chain molybdenum sheets (1). The chain molybdenum sheets (1) are spliced ​​together by pin shafts, and the chain molybdenum sheets (1) have V-shaped arch ridges facing the weld seam. S2. Fixture positioning and fixing: Arrange the tank chain type flexible heat-conducting fixture at the weld position, align the V-shaped arch ridge with the corner weld tip and press it tightly against the base material. Fill the gap between the fixture and the base material and the hinge gap of the fixture with high-temperature resistant fiber pads to reduce contact thermal resistance. S3. Heating and insulation arrangement: Flexible resistance heating elements are laid on the outside of the tank chain type flexible heat-conducting tooling, and a high-temperature resistant insulation layer is wrapped around the flexible resistance heating elements. S4. Temperature measurement and heat treatment operation: Multiple thermocouples are arranged in the center of the weld corner, weld toe and surrounding area. A zoned temperature control system is adopted, and the power of each heating zone is independently adjusted according to the thermocouple feedback signal to execute preset heat treatment processes such as heating, holding and cooling. S5. Post-treatment removal: After heat treatment, wait for the workpiece to cool down to a safe temperature, then remove the insulation layer, flexible resistance heating element, and tank chain flexible heat conduction tooling.

2. The method for local heat treatment of the weld seam of an autoclave according to claim 1, characterized in that: The weld is a circumferential fillet weld in the narrow space between the crown of a large autoclave and the clamp flange.

3. The method for local heat treatment of the weld seam of an autoclave according to claim 1, characterized in that: The tank-chain type flexible heat-conducting tooling is pressed and fixed to the workpiece by heat-resistant buckles and high-temperature metal wires; the high-temperature resistant fiber pad is an aluminum silicate fiber pad; the high-temperature resistant insulation layer is composed of at least two layers of insulation material.

4. The method for local heat treatment of the weld seam of an autoclave according to claim 3, characterized in that: The aluminum silicate fiber pad has a thickness of 2-3 mm; the total thickness of the high-temperature insulation layer is not less than 50 mm; and the high-temperature metal wire is a Φ0.8~1.2 mm high-temperature iron wire.

5. The method for local heat treatment of the weld seam of an autoclave according to claim 1, characterized in that: In step S4, during the heat treatment process, the temperature difference between the weld tip and the temperature measuring points on both sides is controlled to be ≤15℃; after the heat treatment is completed, the tooling is removed only after the overall temperature drops below 300℃.

6. The method for local heat treatment of the weld seam of an autoclave according to claim 1, characterized in that: The chain-type molybdenum sheet (1) is a pure molybdenum sheet with a purity of ≥99.95%; the pin shaft is made of TZM molybdenum alloy or nickel-based high-temperature alloy; the pure molybdenum sheet has a thickness of 4-6mm, a width of 40-80mm, a single section length of 30-50mm, and a relative hinge angle of ≥±15° for a single section of molybdenum sheet; the pin shaft has a diameter of 5-8mm; the included angle of the V-shaped arch rib is adapted to the bevel angle of the fillet weld, and the applicable included angle range is 30°-120°, and the top of the V-shaped arch rib is provided with a radius of R1~R2mm.

7. A local heat treatment system for weld seams in an autoclave, characterized in that: It includes a tank-chain type flexible heat-conducting tooling, a flexible resistance heating device, a high-temperature resistant insulation system, a multi-point temperature detection system, a zoned temperature control system, and a fixed clamping mechanism. The tank chain-type flexible heat-conducting tooling is installed between the toothed flange and the crown end cap, and fits tightly against the weld area; The flexible resistance heating device is fixedly installed on the outside of the tank chain-type flexible heat-conducting tooling. The high-temperature insulation system covers the entire heating area of ​​the flexible resistance heating device. The multi-point temperature detection system includes multiple thermocouples, which are respectively arranged at the center of the weld corner, the weld toes on both sides of the weld, and the outer area of ​​the weld.

8. A local heat treatment system for autoclave welds according to claim 7, characterized in that: The zoned temperature control system is a zoned temperature control cabinet, which is used to receive temperature signals collected by thermocouples and independently adjust the output power of each heating zone.

9. A local heat treatment system for autoclave welds according to claim 7, characterized in that: The fixing and clamping mechanism includes heat-resistant buckles and high-temperature iron wire, which are used to press and fix the tank chain-type flexible heat-conducting tooling at the weld position of the workpiece.

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