Postweld heat treatment method for thick-wall branch pipe angle welding

Abstract

The invention belongs to the technical field of branch pipe welding, and particularly provides a postweld heat treatment method for thick-wall branch pipe angle welding. The invention aims to solve the problem of poor quality of the welded branch pipe caused by non-uniform temperature of the inner wall and the outer wall of the pipeline subjected to post-weld heat treatment of the existing branch pipe. The invention discloses a postweld heat treatment method for angle welding of a thick-wall branch pipe. The postweld heat treatment method comprises the following steps: wrapping heating sheets on local welding parts of a welded main pipe and a welded branch pipe; the outer sides and the inner sides of the heating pieces are wrapped with heat preservation layers respectively, and the heat preservation layers are made to be tightly attached to the outer side walls and the inner side walls of the branch pipes respectively; the inner supporting tool is installed in the main pipe and the branch pipe so as to fix the heat preservation layer on the inner side; a temperature thermocouple is arranged at the edge of the corner seam of the branch pipe, and a temperature control thermocouple is installed at the center of the corner seam of the branch pipe; and the heating piece is controlled to heat the local part of the branch pipe. According to the post-weld heat treatment method for the branch pipe, the internal and external temperatures of the branch pipe are uniform, the temperature loss of the internal and external branch pipes is reduced, and the quality of the post-weld branch pipe is effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of branch pipe welding, and specifically provides a post-weld heat treatment method for thick-wall branch pipe corner welding. Background Art

[0002] The thick-walled corner welds of nuclear power plants are mainly distributed on the manhole structure of the container cylinder or pipeline. In some medium pipelines or containers, the medium itself is corrosive, which will cause corrosion to the corner welds of the branch pipes. Or due to the flow of medium inside the equipment, stress corrosion will occur to the corner welds of the branch pipes during long-term operation. In severe cases, cracks may occur, affecting the stable operation of the nuclear power unit.

[0003] In addition to carbon steel and low alloy steel, the parent material of the corner weld of thick branch pipes in nuclear power plants may also use some medium alloy steel and high alloy steel. Regardless of maintenance, installation, or nuclear power and thermal power industries, these materials have welding heat treatment requirements. The welds of these materials usually have problems such as high joint hardness, low toughness, and reduced mechanical properties such as creep resistance. Therefore, it is necessary to reduce the hardness of the weld and heat-affected zone through post-weld heat treatment to achieve the purpose of improving the performance of the welded joint and reducing the residual stress of the weld. For example, the main pipe manhole structure of the nuclear power turbine steam and drain system has a branch pipe size of φ1400mm×15mm, or a branch pipe size of φ406mm×30mm. The material of the corner weld of the manhole structure branch pipe is 12Cr2Mo1R+Z15. During the welding process, the preheating temperature is required to be no less than 250℃, the constant temperature of the post-weld heat treatment is required to be 735℃±15℃, the constant temperature time is no less than 1.5h, and the heating and cooling rate is no higher than 244℃ / h, so as to improve the performance of the welded joint.

[0004] During the production process, existing manufacturers usually use electric heating furnaces to perform post-weld heat treatment on large-diameter and thick-walled pipe butt joints or branch pipe joints. This heating method can heat the weld evenly and achieve good heat treatment results. However, it is limited by the size of the heating furnace and can only heat prefabricated parts. It is less applicable during on-site inspection and maintenance, and the heat treatment cost is expensive.

[0005] In the existing on-site inspection / maintenance process, the post-weld heat treatment method for large-diameter and thick-walled pipe butt joints or branch pipe joints is usually to use a crawler-type heating plate to heat the local area for local heat treatment. During the on-site heat treatment process, the heat source is usually arranged on the outer wall of the pipe, and the heat is transferred from the outer wall of the pipe to the inner wall by heat conduction, but there is still a certain temperature difference between the inner and outer walls, which will cause the heat treatment to fail to achieve the desired effect. Therefore, in order to ensure the performance of the entire welded joint, it is necessary to reduce the temperature difference between the inner and outer walls as much as possible. As the wall thickness of the pipe increases, the corresponding temperature difference between the inner and outer walls will also increase, and the equivalent thickness of the branch pipe weld is much larger than that of the butt weld. The temperature difference between the inner and outer walls of the branch pipe weld with the same pipe thickness is much larger than that of the butt weld.

[0006] In response to the above problems, many scholars have done a lot of work. One way is to adjust the heat treatment temperature field distribution by controlling the heating range, insulation range, temperature rise and fall speed, temperature control temperature and ambient temperature to reduce the temperature difference between the inner and outer walls. This method is simple to implement but requires too much manpower cost and takes too long. Another way is to heat the inner wall of the pipeline, and heat the inner and outer walls at the same time to achieve the effect of reducing the temperature difference between the inner and outer walls. However, since nuclear power requires that the power voltage in the closed space cannot exceed 12V, this solution is difficult to implement. In view of the above reasons, controlling the temperature difference between the inner and outer walls has become an urgent problem to be solved in the on-site installation or maintenance of branch pipe welds. Summary of the invention

[0007] One object of the present invention is to solve the problem that the existing post-weld heat treatment method for large-sized and thick-walled branch pipes has high heat treatment cost and a large temperature difference between the inner and outer walls of the pipe, resulting in poor heat treatment effect.

[0008] To achieve the above object, the present invention provides a post-weld heat treatment method for thick-walled branch pipe fillet welding, comprising:

[0009] Wrap the local welding part of the pipeline with heating sheet;

[0010] Wrap the outer side of the welding part with a thermal insulation layer, and make the outer thermal insulation layer close to the outer side wall of the welding part;

[0011] Wrapping the inner wall of the welding part with a thermal insulation layer, and installing an inner support fixture in the pipe to fix the inner thermal insulation layer;

[0012] Install temperature measuring thermocouples and temperature controlling thermocouples at welding corner seams;

[0013] The heating plate is controlled to heat a local part of the pipeline.

[0014] Furthermore, the step of wrapping the local welding part of the pipeline with the heating plate also includes: making the heating plate into a shawl-type heating plate, and the heating plate is configured as a crawler-type heating plate.

[0015] Furthermore, the step of controlling the heating plate to heat the local part of the pipeline includes: controlling the heating plate to start heating, and raising the temperature of the temperature-controlled thermocouple to 750±15°C, and setting the heating rate to not more than 244°C / h; controlling the temperature-controlled thermocouple to maintain a constant temperature for at least 1.5h;

[0016] The heating plate is controlled to stop heating, and the temperature-controlling thermocouple is controlled to cool the pipe welding part at a rate of 136° C. / h until the temperature of the pipe welding part is reduced to 150° C.; the pipe is placed in the air to cool to room temperature.

[0017] Furthermore, the step of installing a temperature measuring thermocouple and a temperature controlling thermocouple at the welding corner seam also includes: the temperature measuring thermocouple is set at 20 mm from the edge of the weld; the temperature measuring thermocouple and the temperature controlling thermocouple are overall set to be evenly arranged around the branch pipe.

[0018] Furthermore, the diameter of the branch pipe is set to 406 mm, and the length is set to 30 mm; the diameter of the main pipe is set to 1400 mm, and the length is set to 15 mm; and / or, the thickness of the outer insulation layer is set to 300 mm; the thickness of the inner insulation layer is set to 250 mm.

[0019] Furthermore, the inner support tooling includes a chassis, a support rod and a balance rod, one end of the support rod is installed on the support rod, and the balance rod can pass through the other end of the support rod and be slidably connected to the support rod; the chassis is used to abut against the insulation layer on the inner side of the main pipe, and the balance rod is used to abut against the branch pipe opening.

[0020] Furthermore, a protruding structure is provided on the chassis, the protruding structure matches the inner wall structure of the branch pipe, and the protruding structure is used to press the insulation layer at the inner wall of the branch pipe against the inner wall of the branch pipe.

[0021] Furthermore, the inner support tooling also includes a stop block, which is arranged on one end of the support rod away from the chassis, and the stop block is used to prevent the balance rod from falling off from one end of the support rod.

[0022] Furthermore, a through hole is provided at the center of the chassis, and the through hole is used for installing the support rod.

[0023] Furthermore, the support rod is provided with threads, the through hole is configured as a threaded hole, and the threads on the support rod are matched and tightened with the threaded hole to fix the support rod and the chassis together.

[0024] Furthermore, the chassis surface is configured to be square or circular.

[0025] Furthermore, the chassis is integrally formed; or, the chassis is divided into two sub-chassis, and the two sub-chassis are fixedly connected together by means of hinges.

[0026] Furthermore, the internal support tooling also includes two sliders, which are arranged on the balance rod and slide relative to the balance rod; the two sliders are respectively abutted against the two ends of the branch pipe opening to fix the balance rod of the internal support tooling and the branch pipe.

[0027] Furthermore, both ends of the balance bar are provided with limiting parts extending in the guiding direction of the support rod, and the limiting parts are used to limit the maximum moving distance of the slider to prevent the slider from sliding off the end of the balance bar.

[0028] Furthermore, the step of installing the inner support tooling in the pipeline includes: placing the chassis through the pipeline opening of the main pipe to a position corresponding to the welding of the branch pipe opening; passing the support rod through the pipeline opening of the branch pipe and installing it in cooperation with the through hole of the chassis; passing the balance rod through the support rod, and adjusting the height of the balance rod so that the chassis body fits tightly with the inner insulation layer of the main pipe, the raised structure on the chassis abuts against the inner wall of the branch pipe, and the balance rod abuts against the branch pipe opening; passing the stop block through the end of the support rod to fasten the balance rod to the support rod.

[0029] Based on the foregoing description, those skilled in the art will understand that, in the aforementioned technical solution of the present invention, by heating the inner and outer walls of the pipeline at the same time and adding an inner support tooling inside the inner wall, the insulation layer of the inner wall can be in close contact with the inner wall of the pipeline, thereby effectively reducing the temperature difference between the inner and outer walls of the pipeline, and making the heated branch pipe corner weld heated evenly, so as to eliminate welding residues and stress, improve the structure and performance of the welded joint, improve the quality of heat treatment of the pipeline, reduce the number of rework times of pipeline welding, and effectively improve the welding efficiency of the overall branch pipe welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solution of the present invention, some embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood by those skilled in the art that the same reference numerals indicate the same or similar components or parts in different drawings; the drawings of the present invention are not necessarily drawn to scale.

[0031] In the attached figure:

[0032] Figure 1 is a cross-sectional view of a heat treatment structure of a branch pipe after welding in some embodiments of the present invention;

[0033] Figure 2is a cross-sectional view of a heat treatment structure of a branch pipe after welding in other embodiments of the present invention;

[0034] Figure 3 yes Figure 2 Structural schematic diagram of the middle inner support tooling;

[0035] Figure 4 It is the temperature curve during the heat treatment process of the branch pipe after welding.

[0036] Description of reference numerals:

[0037] 1. Main pipe; 2. Branch pipe; 3. Weld; 4. Heating plate; 5. Outer insulation layer; 6. Inner insulation layer; 7. Temperature measuring thermocouple; 8. Temperature controlling thermocouple; 9. Inner support tooling; 91. Chassis; 911. Raised structure; 92. Support rod; 93. Balance rod; 94. Stop block; 95. Slider; 96. Fasteners. DETAILED DESCRIPTION

[0038] It should be understood by those skilled in the art that the embodiments described below are only some embodiments of the present invention, rather than all embodiments of the present invention, and these embodiments are intended to explain the technical principles of the present invention, rather than to limit the protection scope of the present invention. Based on the embodiments provided by the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should still fall within the protection scope of the present invention.

[0039] It should be noted that in the description of the present invention, the terms "center", "upper", "lower", "top", "bottom", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings, which are only for the convenience of description, and do not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0040] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0041] Refer to the following Figures 1 to 4The heat treatment structure of the branch pipe after welding in some embodiments of the present invention is described in detail. Figure 1 is a cross-sectional view of a heat treatment structure of a branch pipe after welding in some embodiments of the present invention;

[0042] Figure 2 is a cross-sectional view of a heat treatment structure of a branch pipe after welding in other embodiments of the present invention; Figure 3 yes Figure 2 Structural schematic diagram of the middle inner support tooling; Figure 4 It is the temperature curve during the heat treatment process of the branch pipe after welding.

[0043] It should be noted that, for the convenience of description and to enable those skilled in the art to quickly understand the technical solution of the present invention, the following text only describes the technical features that are strongly related (directly or indirectly related) to the technical problem and / or technical concept to be solved by the present invention, and will not describe the technical features that are weakly related to the technical problem and / or technical concept to be solved by the invention. Since the technical features with a weaker degree of correlation belong to the common knowledge in the field, even if the present invention does not describe the features with a weaker degree of correlation, it will not lead to insufficient disclosure of the present invention.

[0044] In some embodiments of the present invention, a post-weld heat treatment method for thick-walled branch pipe corner welding is provided, and the heat treatment method is used to heat treat the main pipe 1 and branch pipe 2 after welding. The diameter of the branch pipe 2 of the present invention is set to 406mm, and the length is set to 30mm. The diameter of the main pipe 1 is set to 1400mm, and the length is set to 15mm. The material of the corner weld of the manhole structure branch pipe is 12Cr2Mo1R+Z15. The hardness of the corner weld of the branch pipe is relatively high, and there are local longitudinal cracks at the weld 3. Therefore, the preheating temperature of the welding process and the heat treatment temperature and the heating / cooling rate in the post-welding process are relatively strict. Specifically, the preheating temperature during welding is set to not less than 250°C, and the local post-weld treatment is required after the welding is completed. The post-weld treatment method can be used for grinding and eliminating crack defects during inspection / repair, and then used for welding repair.

[0045] according to Figure 1 and Figure 2 It can be understood from the cross-sectional view of the branch pipe after welding that the present invention provides a post-weld heat treatment method for a branch pipe, comprising:

[0046] Step S110, installing a temperature measuring thermocouple and a temperature controlling thermocouple at the welding corner seam. The temperature measuring thermocouple 7 is arranged at the edge of the corner seam of the branch pipe 2, and the temperature controlling thermocouple 8 is installed at the center of the corner seam of the branch pipe 2. Among them, the temperature measuring thermocouple 7 is arranged 20 mm from the edge of the weld 3. The temperature measuring thermocouple 7 and the temperature controlling thermocouple 8 are generally arranged to be evenly arranged around the branch pipe 2 in the circumferential direction, so that the temperature detection result of the temperature measuring thermocouple 7 for the weld 3 is more accurate.

[0047] In this embodiment, the temperature control thermocouple 8 is set to one, and the temperature measuring thermocouple 7 is set to multiple, so as to avoid that a single temperature measuring thermocouple 7 only detects the local temperature, the detection result is accidental, and the temperature detection result around the corner seam is inaccurate. Preferably, the temperature measuring thermocouple 7 is set to two. And the two temperature measuring thermocouples 7 are distributed on both sides of the branch pipe.

[0048] Generally, before step S110, the method further includes: cleaning the surfaces of the main pipe 1 and the branch pipe 2. Measuring the dimensions of the main pipe 1 and the branch pipe 2, including the length and diameter.

[0049] Step S120, wrapping the local welding part of the pipeline with the heating plate 4. After the heating plate 4 is made into a shawl-type heating plate 4, it is wrapped on the surface of the main pipe 1 and the branch pipe 2.

[0050] The heating plate 4 is configured as a track-type heating plate.

[0051] Step S130, wrap the outer side of the welding part with an insulation layer, and make the outer insulation layer 5 close to the outer wall of the welding part. According to the determined size of the main pipe 1 and the branch pipe 2, the insulation layer is cut into a structure that matches the circumference of the weld 3. The insulation layer is respectively wrapped around the outer wall of the pipeline, and the outer insulation layer is fixed with a material with a certain ductility such as iron wire or steel wire. Among them, the thickness of the outer insulation layer is set to 300mm. The thickness of the inner insulation layer is set to 250mm.

[0052] The thermal insulation layer can be made of polyurethane material or mineral wool materials such as glass wool and aluminum silicate wool.

[0053] Step S140, wrapping the inner wall of the welding part with a thermal insulation layer, and installing the inner support tooling 9 in the main pipe 1 and the branch pipe 2 to fix the inner thermal insulation layer.

[0054] like Figure 3 As shown, the inner support tool 9 includes a chassis 91, a support rod 92 and a balance rod 93. One end of the support rod 92 is mounted on the support rod 92, and the balance rod 93 can pass through the other end of the support rod 92 and be slidably connected with the support rod 92. The body of the chassis 91 abuts against the insulation layer inside the main pipe 1 to make the insulation layer inside the main pipe 1 tightly attached to the inner wall of the main pipe 1. The balance rod 93 is used to abut against the outlet of the branch pipe 2.

[0055] The chassis 91 is provided with a protruding structure 911, which matches the inner wall structure of the branch pipe 2 and is used to press the insulation layer at the inner wall of the branch pipe 2 against the inner wall of the branch pipe 2. Specifically, the upper surface of the protruding structure 911 is circular.

[0056] A through hole is provided at the center of the chassis 91, and the through hole is used to install the support rod 92. Specifically, the support rod 92 is provided with threads, and the through hole is configured as a threaded hole. The threads on the support rod 92 are tightened with the threaded hole to fix the support rod 92 and the chassis 91 together.

[0057] The chassis 91 is integrally formed by injection molding.

[0058] The chassis 91 is divided into two sub-disks, and the two sub-disks are fixedly connected together by a fastener 96. Specifically, the connection of the two sub-disks is connected together in a hinged manner.

[0059] The surface of the bottom plate 91 is set to be square or circular. Preferably, a circular bottom plate 91 is used in this embodiment. In addition, the diameter of the circular bottom plate is larger than the diameter of the branch pipe 2, and the diameter of the circular bottom plate is smaller than the diameter of the main pipe 1.

[0060] The chassis 91 can be made of a material with a certain hardness and poor thermoplasticity. Specifically, the chassis 91 can be made of a metal or alloy material.

[0061] The inner support tooling 9 further includes a stop block 94 , which is disposed on one end of the support rod 92 away from the chassis 91 , and is used to prevent the balance rod 93 from falling off from one end of the support rod 92 .

[0062] The stop block 94 may be configured as a nut.

[0063] The inner support fixture 9 further includes a slider 95, which is disposed on the balance bar 93 and can slide relative to the balance bar 93. Two sliders 95 are provided, and the two sliders 95 abut against both ends of the branch pipe 2 along the diameter direction to fix the balance bar 93 of the inner support fixture 9 to the branch pipe 2.

[0064] Both ends of the balance bar 93 are provided with limiting parts extending in the guiding direction of the support rod 92 , and the limiting parts are used to limit the maximum moving distance of the slider 95 to prevent the slider 95 from sliding off the end of the balance bar 93 .

[0065] Step S140 also includes:

[0066] Step S141, placing the chassis 91 through the pipe opening of the main pipe 1 to a position corresponding to the welding position of the branch pipe 2.

[0067] Step S142 , passing the support rod 92 through the pipe opening of the branch pipe 2 and fitting it with the through hole of the chassis 91 .

[0068] Step S143, pass the balance rod 93 through the support rod 92, adjust the height of the balance rod 93, make the chassis 91 body fit tightly with the inner insulation layer of the main pipe 1, the raised structure 911 on the chassis 91 abuts against the inner wall of the branch pipe 2, and make the balance rod 93 abut against the opening of the branch pipe 2.

[0069] Step S144, passing the stopper block 94 through the end of the support rod 92 to fasten the balance rod 93 to the support rod 92. Step S130 also includes: moving the two sliders 95 to a position abutting against the pipe opening of the branch pipe 2 to fix the inner support fixture 9 relative to the branch pipe 2 to prevent the support rod 92 of the inner support fixture 9 from shaking in the branch pipe 2 due to external force.

[0070] Step S150, controlling the heating plate 4 to heat a part of the pipeline.

[0071] Wherein, step S150 also includes: step S151, controlling the heating plate 4 to start heating, and raising the temperature of the temperature-controlling thermocouple 8 to 750±15°C, and setting the heating rate to not exceed 244°C / h.

[0072] In other embodiments of the present invention, the heating rate is set to 6250 / ξ℃ / h, where ξ is the equivalent thickness of the welded joint. In this embodiment, ξ is set to be greater than 25 mm, so the heating rate is set to not exceed 244℃ / h.

[0073] In some embodiments of the present invention, the thermal power of the motor may be calculated based on the temperature required for heating.

[0074] Specifically, the electric power can be calculated according to the following formula:

[0075] First, the heat Q required for the heat treatment heating process is calculated according to the formula Q=KWC(T-T0), K is the heat loss coefficient, W is the mass of the heated pipe section, C is the specific heat capacity, T is the heat treatment heating temperature, and T0 is the initial temperature. Among them, the heat loss coefficient K can be verified by multiple tests. The mass W of the heated pipe section is calculated / weighed by the operator before the heat treatment. The specific heat capacity C can be obtained according to the nameplate of the pipeline or by consulting the data. The initial temperature T0 is the temperature detected by the temperature measuring thermocouple 7 before the start of the heat treatment, and then the average of all detected temperatures is taken as the initial temperature. The heat treatment heating temperature T is the temperature detected by the temperature measuring thermocouple 7 during or after the heat treatment, and then the average of all detected temperatures is taken to obtain the heat treatment heating temperature. Then the electric power P required for heating is calculated according to the formula P=Q / t. t is the heating time. Finally, the heating plate is controlled to start heating according to the calculated power.

[0076] Step S152, controlling the temperature-controlling thermocouple 8 to maintain a constant temperature for at least 1.5 hours.

[0077] Step S153, controlling the heating plate 4 to stop heating, and controlling the temperature-controlling thermocouple 8 to cool down the pipe welding part at a rate of 136°C / h until the temperature of the pipe welding part drops to 150°C.

[0078] Step S154, placing the pipe in air to cool to room temperature.

[0079] In this embodiment, the heating and cooling process of the pipeline heat treatment process is as follows: Figure 4 shown.

[0080] In other embodiments of the present invention, the heat treatment method further includes, after the heat treatment is completed, performing a quality inspection on the weld 3. The quality inspection indicators include: magnetic particle inspection, phased array inspection, metallographic inspection and hardness inspection, etc. The above inspection indicators are used to determine whether the weld 3 meets the acceptance requirements. If so, the heat treatment process is completed. If not, the weld 3 can be heat treated again to meet the acceptance requirements.

[0081] It can be understood by those skilled in the art that the present invention heats the inner and outer walls of the pipeline at the same time and adds an inner support tooling 9 inside the inner wall so that the insulation layer of the inner wall can be in close contact with the inner wall of the pipeline, effectively reducing the temperature difference between the inner and outer walls of the pipeline, and making the heated branch pipe corner weld heated evenly, so as to eliminate welding residues and stress, improve the structure and performance of the welded joint, improve the quality of heat treatment of the pipeline, reduce the number of rework times of pipeline welding, and effectively improve the welding efficiency of the overall branch pipe welding.

[0082] So far, the technical solution of the present invention has been described in combination with the above multiple embodiments, but it is easy for those skilled in the art to understand that the protection scope of the present invention is not limited to these specific embodiments. Without departing from the technical principles of the present invention, those skilled in the art can split and combine the technical solutions in the above embodiments, and can also make equivalent changes or replacements to the relevant technical features. Any changes, equivalent replacements, improvements, etc. made within the technical concept and / or technical principles of the present invention will fall within the protection scope of the present invention.

Claims

1. A post-weld heat treatment method for thick-walled branch pipe fillet welding, characterized in that: include: Install temperature measuring thermocouples and temperature controlling thermocouples at the welding corners; Wrap the local welding part of the pipeline with heating sheet; Wrap the outer side of the welding part with a thermal insulation layer, and make the outer thermal insulation layer close to the outer wall of the welding part; Wrapping the inner wall of the welding part with a thermal insulation layer, and installing an inner support fixture in the pipe to fix the inner thermal insulation layer; The heating plate is controlled to heat a local part of the pipeline.

2. The post-weld heat treatment method for thick-walled branch pipe fillet welding according to claim 1, characterized in that: The step of installing a temperature measuring thermocouple and a temperature controlling thermocouple at the welding corner seam also includes: The temperature measuring thermocouple is arranged at 20 mm from the edge of the weld; The temperature measuring thermocouple and the temperature controlling thermocouple are generally arranged uniformly around the branch pipe.

3. The post-weld heat treatment method for thick-walled branch pipe fillet welding according to claim 1, characterized in that: The step of wrapping the local welding part of the pipeline with the heating plate also includes: The heating plate is made into a shawl-type heating plate, and the heating plate is configured as a track-type heating plate.

4. The post-weld heat treatment method for thick-walled branch pipe fillet welding according to claim 1, characterized in that: The step of controlling the heating plate to heat a part of the pipeline comprises: Control the heating plate to start heating, and raise the temperature of the temperature-controlled thermocouple to 750±15°C, with the heating rate set to no more than 244°C / h; Controlling the temperature-controlling thermocouple to maintain a constant temperature for at least 1.5 hours; Control the heating plate to stop heating, and control the temperature-control thermocouple to cool the pipe welding part at a rate of 136° C. / h until the temperature of the pipe welding part drops to 150° C.; The tube was left in air to cool to room temperature.

5. The post-weld heat treatment method for thick-walled branch pipe fillet welding according to claim 1, characterized in that: The branch pipe has a diameter of 406 mm and a length of 30 mm; the main pipe has a diameter of 1400 mm and a length of 15 mm; and / or, The thickness of the outer insulation layer is set to 300mm; the thickness of the inner insulation layer is set to 250mm.

6. The post-weld heat treatment method for thick-walled branch pipe fillet welding according to claim 1, characterized in that: The inner support tooling comprises a chassis, a support rod and a balance rod, one end of the support rod is mounted on the support rod, and the balance rod can pass through the other end of the support rod and be slidably connected to the support rod; The bottom plate is used to abut against the heat preservation layer inside the main pipe, and the balance rod is used to abut against the branch pipe opening.

7. The post-weld heat treatment method for thick-walled branch pipe fillet welding according to claim 6, characterized in that: The chassis is provided with a protruding structure, the protruding structure matches the inner wall structure of the branch pipe, and the protruding structure is used to press the heat preservation layer at the inner wall of the branch pipe against the inner wall of the branch pipe.

8. The post-weld heat treatment method for thick-walled branch pipe fillet welding according to claim 7, characterized in that: The inner support tooling also includes a stop block, which is arranged on one end of the support rod away from the chassis, and the stop block is used to prevent the balance rod from falling off from one end of the support rod.

9. The post-weld heat treatment method for thick-walled branch pipe fillet welding according to claim 6, characterized in that: A through hole is provided at the center of the chassis, and the through hole is used for installing the support rod.

10. The post-weld heat treatment method for thick-walled branch pipe fillet welding according to claim 8, characterized in that: The step of installing the inner support tooling in the pipeline includes: Place the chassis through the pipe opening of the main pipe to a position corresponding to the welding of the branch pipe opening; Pass the support rod through the pipe opening of the branch pipe and install it in cooperation with the through hole of the chassis; Pass the balance bar through the support bar, and adjust the height of the balance bar so that the chassis body is closely fitted with the inner insulation layer of the main pipe, the raised structure on the chassis is in contact with the inner wall of the branch pipe, and the balance bar is in contact with the branch pipe opening; The stop block is passed through the end of the support rod to firmly connect the balance rod to the support rod.

Images