Method of welding a conduit to a u-clip

Abstract

The application provides a welding method of a conduit and a U-shaped clamping block, comprising the following steps: processing a U-shaped clamping block with a circular arc through slot and assembling the U-shaped clamping block with a conduit, assembling the assembly to a special back protection tool, ventilating the back protection tool before welding, adopting argon arc welding uniform distribution spot welding, completing welding through a sectional welding method, and removing the back protection tool after welding; wherein the back protection tool is provided with an air inlet pipe, an air outlet pipe, left and right protection gas cavities and a U-shaped section structure, the protection gas enters the left cavity through the air inlet pipe, passes through the circular arc through slot to the right cavity and is discharged. The method solves the core problem that the back of the weld is difficult to be protected when the U-shaped clamping block is welded with the conduit in the prior art, improves the weld forming effect, effectively reduces the defect occurrence rate of the penetration detection, and meets the requirements of the weld penetration detection and the gauge detection.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and more specifically, to a welding method for a conduit and a U-shaped clamping block. Background Technology

[0002] Argon arc welding, as a widely used welding method, is characterized by stable welding and a small heat-affected zone, making it suitable for welding materials such as stainless steel and alloy steel. The core measurement instrument grid assembly, as a major component of the pressurized water reactor internals, has a complex structure and requires high precision. The guide tube is a core component of the core measurement instrument grid assembly, requiring U-shaped clamping blocks to fix its position. The weld between the U-shaped clamping blocks and the guide tube needs to undergo penetrant testing (PT) and gauge testing, demanding high weld quality.

[0003] When using traditional argon arc welding to directly perform full penetration welding on the U-shaped clamping block and the conduit, the thin-walled conduit is prone to melting through due to its thin wall, and the weld deformation is also large. In addition, due to the special welding structure of the U-shaped clamping block and the conduit, it is difficult to achieve back protection (i.e., inert gas protection on the back of the weld during welding) during full penetration welding, often resulting in poor weld formation and defects easily appearing in PT testing.

[0004] Patent document CN107931793B discloses a back protection device and welding method for titanium alloy welding. The device includes a cold plate with grooves. A gas protection module is installed within the grooves. The gas protection module includes a first groove located in the upper middle portion and extending from one end to the other, a second groove located on the outer sides of the two sidewalls of the first groove, and multiple through holes connecting the first and second grooves. Both ends of the second groove are connected to venting connectors to allow the connection of back protection gas. This invention solves the problem in the prior art where venting through a copper pipe causes the venting copper pipe to be welded shut.

[0005] However, the disadvantage of patent document CN107931793B is that it is applicable to flat plate welding rather than pipe welding. Therefore, it designs a special gas protection module and venting connector, and does not set a gas guide groove on the U-shaped clamping block of the welded parts like this invention, thus saving processing costs. Summary of the Invention

[0006] In view of the deficiencies in the prior art, the purpose of this invention is to provide a welding method for a conduit and a U-shaped clamping block.

[0007] A welding method for a conduit and a U-shaped clamping block according to the present invention includes the following steps:

[0008] S1: Machining the conduit and U-shaped clamping block, the inner diameter of the U-shaped clamping block is adapted to the outer diameter of the conduit, and a circular arc through groove is machined on the U-shaped clamping block. The circular arc through groove is used for back protection of the weld between the conduit and the U-shaped clamping block.

[0009] S2: Fix the relative position of the U-shaped clamping block and the conduit after assembly;

[0010] S3: Install the assembled conduit and U-shaped clamping block onto the back protective fixture. The back protective fixture includes an air inlet pipe, an air outlet pipe, and a protective air cavity. The protective air cavity is connected to the arc-shaped through groove to allow the protective air to flow smoothly through the arc-shaped through groove.

[0011] S4: Introduce protective air into the back cover tooling through the air inlet pipe and continue for a preset time to expel air from the arc groove;

[0012] S5: Weld the conduit to the U-shaped clamping block;

[0013] S6: Remove the back protection fixture after welding is completed.

[0014] Preferably, the distance between the arc groove and the end of the U-shaped clamping block is 1-2 mm, corresponding to the thickness of the blunt edge of the U-shaped clamping block being 1-2 mm during welding.

[0015] Preferably, the protective gas cavity includes a first cavity and a second cavity that are independent of each other. The protective gas flows from the inlet pipe through the first cavity, the arc groove, and the second cavity in sequence, and then is discharged from the outlet pipe.

[0016] Preferably, a flow stabilizing mesh is provided at the connection between the air intake pipe and the first cavity, the flow stabilizing mesh being used to stabilize the flow of protective air into the first cavity.

[0017] Preferably, in step S4, the preset time is greater than 15 seconds, the protective gas is argon with a purity of not less than 99.999%, and the protective gas flow rate is 10-15 L / min.

[0018] Preferably, in step S2, the relative position of the U-shaped clamping block and the conduit is fixed by spot welding. The spot welding is uniform spot welding, and there are welds on both sides of the conduit in the transverse direction. There are no less than 3 spot welding positions on each side of the weld.

[0019] Spot welding is performed using argon arc welding with ER308L welding material, a diameter of 1.2mm, a spot welding current of 50-60A, a voltage of 10-13V, and a shielding gas flow rate of 9-12L / min.

[0020] Preferably, in step S5, a segmented symmetrical welding process is used for full penetration welding, including:

[0021] S5.1: Perform root pass welding, which is done in three sections. First, weld the two ends of the weld, then weld the middle of the weld. When welding, start the arc from both ends of weld 5 and weld towards the middle. The welds on both sides of the lateral side of the conduit are welded symmetrically.

[0022] S5.2: Perform the second layer of welding, which is done in two symmetrical sections, starting from both ends of the weld and welding towards the middle.

[0023] Preferably, the interpass temperature of the root pass welding and the second layer welding is ≤70℃, and the molten pool is biased towards the U-shaped clamping block side during welding to reduce the heat of the conduit.

[0024] Preferably, the root pass welding in step S5.1 adopts argon arc welding and a single-sided welding double-sided forming welding process. The root pass welding and the second layer welding in S5.2 use the same welding material, welding material diameter and welding speed. The welding current of the root pass welding is less than the welding current of the second layer welding, and the welding voltage range of the root pass welding is lower than the welding voltage range of the second layer welding.

[0025] Preferably, the width of the U-shaped groove and the width of the U-shaped clamping block are matched with a tolerance of ±0.1mm, the bottom surface of the U-shaped clamping block is in contact with the bottom surface of the U-shaped groove, the two sides of the U-shaped clamping block are in contact with the two inner tooling surfaces of the U-shaped groove, and the two end faces of the U-shaped clamping block parallel to the axial direction of the conduit are in contact with the two end faces of the U-shaped groove along the axial direction.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. This invention achieves effective protection of the back side of the weld by adding an arc groove structure to the U-shaped clamping block and matching it with a special back protection tool (including a protective air cavity, an air inlet pipe, and an air outlet pipe structure), thereby optimizing the weld formation quality from the source.

[0028] 2. This invention employs a segmented welding method to perform full-penetration welding of the U-shaped clamping block and the conduit, which can precisely control the welding heat input, reduce the heat received by the thin-walled conduit, and prevent the conduit from melting through. At the same time, it balances welding deformation through symmetrical welding and other methods to ensure the precision requirements of the welded components.

[0029] 3. This invention achieves full penetration welding of the U-shaped clamping block and the conduit in one go, resulting in high welding efficiency and good weld strength. Attached Figure Description

[0030] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0031] Figure 1 This is a schematic diagram illustrating the U-shaped clamping block bevel, which is the main feature of this invention.

[0032] Figure 2 This is a top view of the assembly structure of the catheter and the U-shaped clamping block, which is the main feature of this invention.

[0033] Figure 2A for Figure 2 Sectional view of the C-section;

[0034] Figure 3 This is a bottom view of the back protection tooling structure, which is the main feature of this invention.

[0035] Figure 3A for Figure 3 Sectional view of EE section;

[0036] Figure 3B for Figure 3 Sectional view of section DD;

[0037] Figure 4 This is a front view of the assembly structure of the conduit, U-shaped clamping block, and back protection tooling, which are the main components of this invention.

[0038] Figure label:

[0039] Detailed Implementation

[0040] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0041] Example 1:

[0042] Taking the welding of the conduit 1 and U-shaped clamping block 2 of the pressurized water reactor core measurement instrument grid assembly as an example, the materials of both the conduit 1 and the U-shaped clamping block 2 are Z2CN1910+N2. The specifications of the conduit 1 are φ16xφ13mm, the thickness of the blunt edge 22 of the U-shaped clamping block 2 is 1.5mm, and the R value of the arc groove 3 is 5mm. The welding process of the conduit 1 and the U-shaped clamping block 2 is as follows:

[0043] S1: Machining the conduit 1 and the U-shaped clamping block 2, the inner diameter of the U-shaped clamping block 2 is adapted to the outer diameter of the conduit 1, and machining an arc-shaped through groove 3 on the U-shaped clamping block 2 (see appendix for details). Figure 1 The arc-shaped through groove 3 is used to protect the back side of the weld 5 between the guide tube 1 and the U-shaped clamping block 2. Its cross-section is designed as an arc rather than a square, which reduces the flow resistance of the shielding gas, improves flow efficiency, and facilitates uniform gas distribution compared to other shapes of through grooves. In addition to allowing shielding gas to pass through, it further optimizes the back side protection effect of the weld. The arc-shaped through groove 3 is positioned 1-2 mm from the end 21 of the U-shaped clamping block 2; in this embodiment, it is set to 1.5 mm. The end 21 refers to the end of the U-shaped clamping block 2 in the opening direction. The thickness of the blunt edge 22 during welding is 1-2 mm; in this embodiment, 1.5 mm is used to achieve single-sided welding with double-sided forming during argon arc welding (see position 51 for single-sided welding with double-sided forming). Figure 2AIf the blunt edge 22 is too thick, it will not be possible to achieve full penetration. The blunt edge 22 is located between the end 21 and the arc-shaped through groove 3. Figure 1 In the middle, the vertical direction is the width direction of the U-shaped clamping block 2, and the horizontal direction is the height direction of the U-shaped clamping block 2.

[0044] S2: Assemble the U-shaped clamping block 2 with the guide tube 1 (see appendix for details). Figure 2 After assembly, the relative positions of the two parts can be fixed by spot welding, and the subsequent weld points will be fused into weld 5. This spot welding is a uniformly distributed spot welding, with weld 5 on each of the transverse sides of the conduit 1, and no fewer than 3 spot welding positions on each side of weld 5. "Transverse" refers to the direction perpendicular to the axial direction of the conduit 1 (i.e.,...). Figure 2 (Up and down direction). The spot welding parameters are as follows: argon arc welding, welding material is ER308L, welding material diameter is 1.2mm, spot welding current is 50-60A, voltage is 10-13V, shielding gas is argon (purity not less than 99.999%), flow rate is 9~12L / min.

[0045] S3: Install the U-shaped clamping block 2 with the conduit 1 installed onto the back protection fixture 4 (see attached document for details). Figure 3 (See attached document for details after assembly of the back cover tool 4) Figure 4 The protective gas fixture 4 includes an air inlet pipe 41, an air outlet pipe 42, and a protective gas cavity 43. The protective gas cavity 43 is connected to an arc-shaped through groove 3 to allow the protective gas to flow smoothly through the arc-shaped through groove 3. The protective gas cavity 43 may include a first cavity 431 and a second cavity 432 that are independent of each other. The first cavity 431 and the second cavity 432 are each surrounded by a cavity wall 45. A U-shaped groove is provided between the corresponding cavity walls of the first cavity 431 and the second cavity 432 to accommodate a U-shaped clamping block 2. Figure 3 The left and right directions in the middle are the axial directions of the U-shaped groove.

[0046] The orientation relationship between the back-mounted tool 4 and the U-shaped clamping block 2 during assembly has been established. Figure 4 As shown in the figure, Figure 3B The DD section shows that the width of the U-shaped groove and the width of the U-shaped clamping block 2 are matched with a tolerance of ±0.1mm. The bottom surface of the U-shaped clamping block 2 is in contact with the bottom surface of the U-shaped groove. The two sides of the U-shaped clamping block 2 are in contact with the two inner tooling surfaces of the U-shaped groove. The two end faces of the U-shaped clamping block 2 parallel to the axial direction of the guide tube 1 are in contact with the two end faces of the axial direction of the U-shaped groove. This can ensure the assembly accuracy of the U-shaped clamping block 2 and the U-shaped groove and avoid air leakage.

[0047] A flow stabilizing mesh 6 (such as a copper mesh) is provided at the connection between the air inlet pipe 41 and the first cavity 431. The flow stabilizing mesh 6 is used to stabilize the flow of protective gas into the first cavity 431. The protective gas flows from the air inlet pipe 41 through the first cavity 431, the arc-shaped through groove 3, and the second cavity 432 in sequence, and then exits from the air outlet pipe 42, thus achieving protection of the back side of the weld 5. The reason for adopting this gas path design is that the arc-shaped through groove 3 is relatively small. If the air inlet pipe 41 is directly connected to the arc-shaped through groove 3, the protection will be insufficient when the airflow is small, and the gas pressure will easily affect the formation of the weld 5 when the airflow is large. However, the first cavity 431 and the second cavity 432, together with the flow stabilizing mesh 6, can stabilize the airflow when the airflow is large, so that the protective gas passes smoothly through the arc-shaped through groove 3, ensuring effective back protection.

[0048] S4: Introduce protective gas into the back cover fixture 4 through the air inlet pipe 41 for a preset time, which is greater than 15 seconds, to completely remove air from the arc-shaped groove 3. The protective gas is argon with a purity of not less than 99.999%, and the flow rate is 10-15 L / min to ensure adequate back cover protection.

[0049] S5: Argon arc welding is used to weld the conduit 1 to the U-shaped clamping block 2. The welding method is a segmented symmetrical welding process to achieve full penetration welding. The specific steps are as follows:

[0050] S5.1: Root pass welding: Welding is performed in three sections. First, weld the two ends of weld 5, then weld the middle section of weld 5. During welding, start the arc from both ends of weld 5 and weld towards the middle to avoid defects such as arc craters and undercuts that occur at the end of the arc. This step uses a single-sided welding with double-sided forming process. Furthermore, the welds 5 on both sides of the conduit 1 in the transverse direction are welded symmetrically to balance welding deformation. The transverse direction refers to... Figure 2A The welding process should be carried out in the vertical direction. During welding, the interpass temperature should be controlled to ≤70℃. Excessive temperature can easily cause the thin-walled conduit 1 to melt through. During welding, the molten pool should be biased towards the U-shaped clamping block 2 side. Specifically, the tungsten electrode of the welding torch should be offset towards the base material on the U-shaped clamping block 2 side, directing the molten iron towards the base material on the U-shaped clamping block 2 side, as far away as possible from the base material on the conduit 1 side. This reduces the heat received by the conduit 1, ensuring that the U-shaped clamping block 2 is fully penetrated without melting through the conduit 1. The root pass welding parameters are: argon arc welding, ER308L welding material, welding material diameter 1.2mm, current 55A, voltage 10-12V, welding speed 7-8cm / min, shielding gas argon (purity not less than 99.999%), flow rate 9-12L / min, and interpass temperature ≤70℃.

[0051] S5.2: Second layer welding: Weld symmetrically in two sections, starting the arc from both ends of weld 5 and welding towards the middle to avoid arc termination defects appearing at the ends of weld 5; at the same time, control the interpass temperature ≤70℃, and continue the operation of the molten pool biased towards the U-shaped clamping block 2 during welding to reduce the heat of the guide tube 1 and avoid burn-through. The parameters for the second layer welding are: argon arc welding, welding material is ER308L, welding material diameter is 1.2mm, current is 60A, voltage is 11-13V, welding speed is 7~8cm / min, shielding gas is argon (purity not less than 99.999%), flow rate is 9~12L / min, and interpass temperature ≤70℃.

[0052] The root pass welding in S5.1 and the second layer welding in S5.2 use the same specifications of welding materials, welding material diameter and welding speed, and the welding current of the root pass welding is less than the welding current of the second layer welding, and the welding voltage range of the root pass welding is lower than the welding voltage range of the second layer welding.

[0053] S6: After welding is completed, remove the back protection fixture 4.

[0054] Through the above welding method, the back side of the weld 5 is effectively protected by the cooperation of the arc groove 3 and the back protection fixture 4, and the single-sided welding with double-sided forming is successfully achieved. The weld 5 is well formed. After liquid penetration test (PT) and gauge inspection, the weld 5 is qualified. The weld 5 between the U-shaped clamping block 2 and the guide tube 1 is firm and reliable, which can meet the product welding requirements.

[0055] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application 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, they should not be construed as limitations on this application.

[0056] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for welding a conduit to a U-shaped clamping block, characterized in that, Includes the following steps: S1: Process the conduit (1) and the U-shaped clamping block (2). The inner diameter of the U-shaped clamping block (2) is adapted to the outer diameter of the conduit (1). A circular arc through groove (3) is processed on the U-shaped clamping block (2). The circular arc through groove (3) is used for back protection of the weld (5) between the conduit (1) and the U-shaped clamping block (2). S2: After assembling the U-shaped clamping block (2) and the conduit (1), fix their relative positions; S3: Install the assembled conduit (1) and U-shaped clamping block (2) onto the back protection fixture (4). The back protection fixture (4) includes an air inlet pipe (41), an air outlet pipe (42), and a protective gas cavity (43). The protective gas cavity (43) is connected to the arc-shaped through groove (3) to allow the protective gas to flow smoothly through the arc-shaped through groove (3). S4: Introduce protective gas into the back protective fixture (4) through the air inlet pipe (41) and continue for a preset time to remove the air in the arc groove (3); S5: Weld the conduit (1) to the U-shaped clamping block (2); S6: Remove the back protection fixture (4) after welding is completed.

2. The welding method of the conduit and the U-shaped clamping block according to claim 1, characterized in that, The distance between the arc groove (3) and the end (21) of the U-shaped clamping block (2) is 1-2 mm, corresponding to the thickness of the blunt edge (22) of the U-shaped clamping block (2) during welding, which is 1-2 mm.

3. The welding method of the conduit and the U-shaped clamping block according to claim 1, characterized in that, The protective gas cavity (43) includes a first cavity (431) and a second cavity (432) that are independent of each other. The protective gas flows from the inlet pipe (41) through the first cavity (431), the arc groove (3), and the second cavity (432) in sequence, and then is discharged from the outlet pipe (42).

4. The welding method of the conduit and the U-shaped clamping block according to claim 3, characterized in that, A flow stabilizing net (6) is provided at the connection between the air inlet pipe (41) and the first cavity (431). The flow stabilizing net (6) is used to stabilize the flow of protective air into the first cavity (431).

5. The welding method of the conduit and the U-shaped clamping block according to claim 1, characterized in that, In step S4, the preset time is greater than 15 seconds, the protective gas is argon with a purity of not less than 99.999%, and the protective gas flow rate is 10-15 L / min.

6. The welding method of the conduit and the U-shaped clamping block according to claim 1, characterized in that, In step S2, the relative positions of the U-shaped clamping block (2) and the conduit (1) are fixed by spot welding. The spot welding is uniform spot welding. There are welds (5) on both sides of the conduit (1) in the transverse direction. There are no less than 3 spot welding positions on each side of the weld (5). Spot welding is performed using argon arc welding with ER308L welding material, a diameter of 1.2mm, a spot welding current of 50-60A, a voltage of 10-13V, and a shielding gas flow rate of 9-12L / min.

7. The welding method of the conduit and the U-shaped clamping block according to claim 1, characterized in that, In step S5, a segmented symmetrical welding process is used for full penetration welding, including: S5.1: Perform root pass welding in three sections. First, weld the two ends of the weld (5), then weld the middle part of the weld (5). When welding, start the arc from the two ends of the weld (5) and weld towards the middle. The welds (5) on both sides of the conduit (1) are welded symmetrically. S5.2: Perform the second layer of welding: Weld symmetrically in two sections, starting from both ends of the weld (5) and welding towards the middle.

8. The welding method of the conduit and the U-shaped clamping block according to claim 7, characterized in that, The interpass temperature of the root pass welding and the second layer welding is ≤70℃. During welding, the molten pool is biased towards the U-shaped clamping block (2) side, thereby reducing the heat of the conduit (1).

9. The welding method of the conduit and the U-shaped clamping block according to claim 7, characterized in that, The root pass welding in step S5.1 uses argon arc welding and a single-sided welding double-sided forming welding process; The root pass welding and the second layer welding in S5.2 use the same welding material, welding material diameter and welding speed, and the welding current of the root pass welding is less than the welding current of the second layer welding, and the welding voltage range of the root pass welding is lower than the welding voltage range of the second layer welding.

10. The welding method of the conduit and the U-shaped clamping block according to claim 3, characterized in that, The first cavity (431) and the second cavity (432) are each surrounded by a cavity wall (45). A U-shaped groove is provided between the corresponding cavity walls (45) of the first cavity (431) and the second cavity (432) to accommodate a U-shaped clamping block (2). The width of the U-shaped groove and the width of the U-shaped clamping block (2) are matched with a tolerance of ±0.1mm. The bottom surface of the U-shaped clamping block (2) is in contact with the bottom surface of the U-shaped groove. The two sides of the U-shaped clamping block (2) are in contact with the two inner tooling surfaces of the U-shaped groove. The two ends of the U-shaped clamping block (2) parallel to the axial direction of the conduit (1) are in contact with the two axial ends of the U-shaped groove.

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