A method for full penetration welding of thick weld seams in flanges

Abstract

This invention relates to a method for achieving full penetration of a thick weld seam on a flange. The flange contains a welded cylinder, and an anti-corrosion layer is welded to the top surfaces of both the flange and the cylinder. First, the flange is machined to form sequentially connected first, third, and second welding spaces. Within the first welding space, a first weld seam adapted to the first inclined surface is welded. Then, the cylinder is inserted into the flange, and second to fifth weld seams are sequentially welded between the first weld seam and the cylinder. Welding then takes place in the third and second welding spaces. Finally, the anti-corrosion layer is welded onto the flange and the cylinder. This invention uses the first weld seam as a transition layer, ensuring that the cylinder does not overheat, the flange's mechanical and machinability properties are maintained, and the entire weld seam within the first welding space is fully penetrated, thus avoiding defects such as slag inclusions, incomplete penetration, and cracks in the weld seam within the first welding space.

Description

Technical Field

[0001] This invention relates to the field of welding, and more particularly to the field of thick weld seam technology, specifically to a method for full penetration welding of thick weld seams based on flanges. Background Technology

[0002] A weld is a joint formed by melting and connecting the welding rod and the metal at the joint using the high temperature of a welding heat source. After the weld metal cools, the two workpieces are joined into a whole. Depending on the shape of the weld metal and the relative positions of the workpieces, welds are classified as butt welds, fillet welds, plug welds, and riveting welds. Butt welds are commonly used for splicing plates and structural steel; fillet welds are commonly used for lap joints; plug welds and riveting welds are less common and are only considered to reduce the lap length of the workpieces.

[0003] When welding large seams between a stainless steel cylinder and carbon steel, the existing technology directly welds the stainless steel cylinder and the carbon steel Q345R flange base from bottom to top. This easily causes the migration of carbon elements in the carbon steel Q345R flange base, that is, the carbon elements penetrate from the flange base into the stainless steel cylinder, reducing the corrosion resistance of the stainless steel cylinder. In addition, due to the small space at the bottom of the weld, defects such as slag inclusion, incomplete penetration, and cracks are easily generated in the weld. It can also cause the stainless steel cylinder to overheat, and the final result is coarsening of the grains, uneven stress distribution, large deformation of the flange, and reduced flange strength, thereby reducing the flange's mechanical properties and machinability. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for full penetration welding of thick weld seams on flanges, ensuring the corrosion resistance of stainless steel cylinders, guaranteeing welding space at the bottom weld seam, preventing overheating of the stainless steel cylinders, and ensuring the mechanical and machinability properties of the flange.

[0005] This invention is achieved through the following technical solution: a method for full penetration welding of a thick weld seam based on a flange, wherein a cylindrical body is welded inside the flange, comprising the following steps:

[0006] S01. The flange blank is processed to form a spacer ring on the inner circumferential surface of the flange. Starting from the spacer ring, a first inclined surface extending towards the upper end face of the flange and a second inclined surface extending towards the lower end face of the flange are cut. The first inclined surface includes a third inclined surface extending to the upper end face of the flange and a first arc surface connecting the third inclined surface and the spacer ring. The center of the first arc surface is located in the inner ring of the flange.

[0007] S02. A first welding space connected to the upper end face of the flange, a second welding space connected to the lower end face of the flange, and a third welding space located between the spacer ring and the cylinder are formed in the inner ring of the cylinder and the flange. The third welding space is connected to the first welding space and the second welding space.

[0008] S03. In the first welding space, a first weld bead is welded on the first inclined surface, the outer surface of which is adapted to the first inclined surface. Then the cylinder is inserted into the flange. A second weld bead, a third weld bead, a fourth weld bead, and a fifth weld bead are welded sequentially on the first weld bead and between the cylinder and the first weld bead, the second weld bead, a third weld bead, a fourth weld bead, and a fifth weld bead that are connected sequentially along the extension direction of the first inclined surface. The fifth weld bead extends onto the upper end face of the flange.

[0009] S04. In the third welding space, the sixth weld connecting the cylinder and the flange is welded; in the second welding space, the seventh weld connecting the cylinder and the flange is welded, the seventh weld being triangular in shape.

[0010] This invention divides the weld into three welding spaces by setting a spacer ring, thereby ensuring that the weld is divided into whole and orderly welds. At the same time, the setting of the third welding space avoids interference fit between the flange and the cylinder. Furthermore, the setting of three welding spaces enhances the welding strength between the flange and the cylinder, preventing issues such as pitting and overheating.

[0011] By setting up three welding spaces, the stainless steel cylinder and the carbon steel flange are isolated, preventing carbon elements in the carbon steel from penetrating into the cylinder. The first weld serves as a transition layer, while the second, third, fourth, and fifth welds are the surface layers for welding. This ensures that the cylinder does not overheat, the mechanical and machinability properties of the flange are guaranteed, and the entire weld in the first welding space is fully penetrated, thus avoiding defects such as slag inclusions, incomplete penetration, and cracks in the weld within the first welding space.

[0012] By setting up the first arc surface and the second welding space, the distance between the flange and the cylinder is increased, thereby ensuring the welding space for the bottom weld in the first welding space, which facilitates the insertion of the welding wire and the welding process.

[0013] Preferably, the distance between the spacer ring and the upper end face of the flange is 5-6 times the distance between the spacer ring and the lower end face of the flange.

[0014] The height of the second weld, the third weld, and the fourth weld gradually decreases.

[0015] In this preferred embodiment, due to the inclined setting of the first inclined surface, in order to ensure the welding strength at the bottom of the first inclined surface, it is necessary to increase the length of the second weld, and so on, so that the height of the second weld, the third weld and the fourth weld gradually decreases.

[0016] Preferably, the upper end face of the flange is also welded with an anti-corrosion layer that is welded to the upper end face of the cylinder, and the method further includes the following steps: in step S01, a groove communicating with the inner ring of the flange is opened on the upper end face of the flange, and the fifth weld extends into the groove.

[0017] S05. Deepen the groove to match half the height of the anti-corrosion layer. While deepening the groove, cut off part of the fifth weld and process the first chamfer on the upper end face of the cylinder to connect with the inner surface of the cylinder. Then, put the anti-corrosion layer into the groove so that one end of the anti-corrosion layer is flush with the inner circumferential surface of the cylinder. At this time, the second chamfer on the anti-corrosion layer is symmetrically set with the first chamfer. There is a gap between the other end of the anti-corrosion layer and the groove wall.

[0018] S06. Weld the eighth weld in the first chamfer and the second chamfer, and weld the tenth weld in the gap connecting the groove wall and the other end face of the anti-corrosion layer.

[0019] S07. Continue cutting the upper end face of the flange so that the upper end face of the flange is coplanar with the bottom of the groove. At the same time, cut the tenth weld into the ninth weld.

[0020] The gap design facilitates the welding of the groove and the anti-corrosion layer. The first and second chamfers also facilitate the welding of the flange and the anti-corrosion layer.

[0021] Preferably, the tenth weld has a rectangular cross-section, and the ninth weld has a triangular cross-section with its two sides welded to the bottom of the groove and the other end face of the anti-corrosion layer, respectively.

[0022] This preferred solution avoids stress concentration and deformation by setting up triangular welds.

[0023] Preferably, the welds in the first welding space and the second welding space are welded using, but not limited to, A102 welding rods with a diameter of 3.2-4 mm.

[0024] The beneficial effects of the present invention are as follows: by setting the spacer ring, the weld is divided into three welding spaces, thereby ensuring that the weld is divided into whole and orderly welds. At the same time, the setting of the third welding space avoids interference fit between the flange and the cylinder. Furthermore, the setting of the three welding spaces enhances the welding strength between the flange and the cylinder and avoids pitting, overheating, and other problems.

[0025] By setting up three welding spaces, the stainless steel cylinder and the carbon steel flange are isolated, preventing carbon elements in the carbon steel from penetrating into the cylinder. The first weld serves as a transition layer, while the second, third, fourth, and fifth welds are the surface layers for welding. This ensures that the cylinder does not overheat, the mechanical and machinability properties of the flange are guaranteed, and the entire weld in the first welding space is fully penetrated, thus avoiding defects such as slag inclusions, incomplete penetration, and cracks in the weld within the first welding space.

[0026] By setting up the first arc surface and the second welding space, the distance between the flange and the cylinder is increased, thereby ensuring the welding space for the bottom weld in the first welding space, which facilitates the insertion of the welding wire and the welding process. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the flange section during step S01;

[0028] Figure 2 This is a schematic diagram of a partial cross-section of the flange after the first weld seam is welded.

[0029] Figure 3 This is a schematic diagram of the structure when the cylinder is inserted into the flange.

[0030] Figure 4 This is a schematic diagram of the structure after the second to fifth welds have been completed;

[0031] Figure 5 This is a schematic diagram of the structure after the sixth and seventh welds have been completed.

[0032] Figure 6 This is a schematic diagram of the structure after the groove has been deepened;

[0033] Figure 7 A schematic diagram of the structure after the eighth and tenth welds have been completed;

[0034] Figure 8 This is a schematic diagram of the structure after welding is completed;

[0035] As shown in the figure:

[0036] 1. First weld, 2. Second weld, 3. Third weld, 4. Fourth weld, 5. Fifth weld, 6. Flange, 7. Cylinder, 8. Anti-corrosion layer, 9. Spacer ring, 10. Groove, 11. Third inclined surface, 12. First arc surface, 13. Second inclined surface, 14. First welding space, 15. Second welding space, 16. Third welding space, 17. Sixth weld, 18. Seventh weld, 19. Eighth weld, 20. Tenth weld, 21. Ninth weld. Detailed Implementation

[0037] To clearly illustrate the technical features of this solution, the following detailed implementation method will be used to explain the solution.

[0038] See attached document Figure 1-8 This invention discloses a method for full penetration welding of thick weld seams based on flanges, wherein a cylindrical body 7 is welded inside the flange 6, and an anti-corrosion layer 8, which is welded to the upper end face of the flange 6 and the cylindrical body 7, is welded to the upper end face of the flange 6. The method includes the following steps:

[0039] S01. The flange 6 blank is processed to form a spacer ring 9 on the inner circumferential surface of the flange 6. The spacer ring 9 is cut into a first inclined surface extending to the upper end face of the flange 6 and a second inclined surface 13 extending to the lower end face of the flange 6. The first inclined surface includes a third inclined surface 11 extending to the upper end face of the flange 6 and a first arc surface 12 connecting the third inclined surface 11 and the spacer ring 9. The center of the first arc surface 12 is located in the inner ring of the flange 6. A groove 10 communicating with the inner ring of the flange 6 is opened on the upper end face of the flange 6.

[0040] S02. Using the spacer ring 9 as a dividing ring, a first welding space 14 connected to the bottom of the groove 10, a second welding space 15 connected to the lower end face of the flange 6, and a third welding space 16 located between the spacer ring 9 and the cylinder 7 are formed in the inner ring of the cylinder 7 and the flange 6. The third welding space 16 connects the first welding space 14 and the second welding space 15. The first inclined surface is located in the first welding space 14, the second inclined surface 13 is located in the second welding space 15, and the height of the third welding space 16 is the height of the spacer ring 9.

[0041] S03. Then, within the first welding space 14, a first weld 1, adapted to the first inclined surface, is welded on the first inclined surface. The welding method is shielded metal arc welding (SMAW). The thickness of the first weld 1 is 3-4 mm, the welding current is 110-160 A, the welding voltage is 24-26 V, the welding speed is 10-16 cm / min, the welding temperature is ≤150℃, the electrode composition is A302, and the electrode diameter is φ4.0 mm. Then, hydrogen removal heat treatment is performed at a holding temperature of 200-300℃ for ≥0.5 h. Next, stress relief heat treatment is performed in the furnace at a temperature of 600℃ for 2.5 h. After the tube sheet is removed from the furnace, it is slowly cooled to room temperature, and the weld surface is ground. Finally, non-destructive testing is performed.

[0042] Next, the second weld 2, the third weld 3, the fourth weld 4, and the fifth weld 5, which are connected sequentially along the extension direction of the first inclined surface, are welded between the first weld 1 and the cylinder 7. The fifth weld 5 extends into the groove 10. Then, a hydrogen removal heat treatment is performed, and the cylinder is put into the furnace for stress relief. After being taken out of the furnace, the cylinder is slowly cooled to room temperature. Then, the surface of the weld layer is ground and non-destructive testing is performed.

[0043] S04. In the third welding space 16, the sixth weld 17 connecting the cylinder 7 and the flange 6 is welded; in the second welding space 15, the seventh weld 18 connecting the cylinder 7 and the flange 6 is welded, the seventh weld 18 being triangular in shape.

[0044] S05. Deepen the groove 10 so that the depth of the groove 10 matches half the height of the anti-corrosion layer 8. While deepening the groove 10, cut off part of the fifth weld 5 and process the first chamfer connected to the inner surface of the cylinder 7 on the upper end face of the cylinder 7. Then, put the anti-corrosion layer 8 into the groove 10 so that one end of the anti-corrosion layer 8 is flush with the inner circumferential surface of the cylinder 7. At this time, the second chamfer opened on the anti-corrosion layer 8 is symmetrically set with the first chamfer. There is a gap between the other end of the anti-corrosion layer 8 and the groove wall of the groove 10.

[0045] S06. Weld the eighth weld 19 within the first and second chamfers, and weld the tenth weld 20 connecting the groove wall of the groove 10 and the other end face of the anti-corrosion layer 8 within the gap. The cross-section of the tenth weld 20 is rectangular.

[0046] S07. Continue cutting the upper end face of flange 6 so that the upper end face of flange 6 is set in the same plane as the bottom of groove 10. At the same time, cut the tenth weld 20 into the ninth weld 21. The cross-section of the ninth weld 21 is a triangle with two sides welded to the bottom of groove 10 and the other end face of anti-corrosion layer 8, respectively.

[0047] The distance between the spacer ring 9 and the upper end face of the flange 6 is 5-6 times the distance between the spacer ring 9 and the lower end face of the flange 6.

[0048] The heights of the second weld 2, the third weld 3, and the fourth weld 4 gradually decrease. The welding method for the second weld 2 is shielded metal arc welding (SMAW), with a weld thickness of 3-4 mm, a welding current of 110-160 A, a welding voltage of 24-26 V, a welding speed of 10-16 cm / min, a welding temperature of ≤150℃, and an electrode composition of A102 with a diameter of φ4.0 mm.

[0049] The welding method for the third weld 3, the fourth weld 4, and the fifth weld 5 is shielded metal arc welding (SMAW). The thickness of the weld layer is 3-4 mm, the welding current is 110-160 A, the welding voltage is 24-26 V, the welding speed is 10-16 cm / min, the welding temperature is ≤150℃, the electrode composition is A102, and the electrode diameter is φ4.0 mm.

[0050] Of course, the above description is not limited to the examples above. Technical features not described in this invention can be implemented by or using existing technology, and will not be repeated here. The above embodiments and drawings are only used to illustrate the technical solutions of this invention and are not intended to limit this invention. This invention has been described in detail with reference to preferred embodiments. Those skilled in the art should understand that any changes, modifications, additions or substitutions made by those skilled in the art within the scope of this invention do not depart from the spirit of this invention and should also fall within the scope of protection of the claims of this invention.

Claims

1. A method for full penetration welding of large thickness welds based on a flange (6) to which a cylindrical shell (7) is welded, characterized in that, The method comprises the following steps: S01, machining the flange (6) blank to form a spacing ring (9) on the inner circumferential surface of the flange (6), cutting a first inclined surface extending to the upper end surface of the flange (6) from the spacing ring (9), and a second inclined surface (13) extending to the lower end surface of the flange (6), the first inclined surface comprising a third inclined surface (11) extending to the upper end surface of the flange (6), and a first arc surface (12) connecting the third inclined surface (11) and the spacing ring (9), the center of the first arc surface (12) being located on the inner circle of the flange (6), a groove (10) is formed on the upper end surface of the flange (6) and communicates with the inner circle of the flange (6), S02, forming a first welding space (14) connected with the upper end surface of the flange (6), a second welding space (15) connected with the lower end surface of the flange (6), and a third welding space (16) between the spacing ring (9) and the cylinder (7) on the inner circle of the flange (6) and the cylinder (7), S03, welding a first weld (1) with an outer surface matched with the first inclined surface in the first welding space (14), then inserting the cylinder (7) into the flange (6), and sequentially welding a second weld (2), a third weld (3), a fourth weld (4), and a fifth weld (5) connected in the extension direction of the first inclined surface between the first weld (1) and the cylinder (7), the fifth weld (5) extending into the groove (10), S04, welding a sixth weld (17) connecting the cylinder (7) and the flange (6) in the third welding space (16), and welding a seventh weld (18) connecting the cylinder (7) and the flange (6) in the second welding space (15), the seventh weld (18) being in a triangular shape, S05, deepening the depth of the groove (10) to match the depth of the groove (10) with half the height of the corrosion-resistant layer (8), cutting part of the fifth weld (5) while deepening the depth of the groove (10), machining a first chamfer connected with the inner surface of the cylinder (7) on the upper end surface of the cylinder (7), then placing the corrosion-resistant layer (8) into the groove (10) so that one end of the corrosion-resistant layer (8) is flush with the inner circumferential surface of the cylinder (7), at this time, a second chamfer formed on the corrosion-resistant layer (8) is symmetrically arranged with the first chamfer, and a gap exists between the other end of the corrosion-resistant layer (8) and the groove wall of the groove (10), S06, welding an eighth weld (19) in the first chamfer and the second chamfer, and welding a tenth weld (20) connecting the groove wall of the groove (10) and the other end surface of the corrosion-resistant layer (8) in the gap, S07, continuing to cut the upper end surface of the flange (6) so that the upper end surface of the flange (6) is coplanar with the groove bottom of the groove (10), and cutting the tenth weld (20) into a ninth weld (21).

2. The flange-based, large-thickness weld full-penetration method of claim 1, wherein: The distance between the spacing ring (9) and the upper end surface of the flange (6) is 5-6 times the distance between the spacing ring (9) and the lower end surface of the flange (6).

3. The flange-based, full-penetration weld of large thickness method of claim 1, wherein: The heights of the second weld (2), the third weld (3), and the fourth weld (4) gradually decrease.

4. The flange-based, large-thickness weld full-penetration method of claim 1, wherein: The cross section of the tenth weld (20) is rectangular, and the cross section of the ninth weld (21) is triangular, with two sides welded to the groove bottom and the other end face of the anticorrosive layer (8) respectively.

5. The flange-based, large-thickness weld full-penetration method of claim 1, wherein: The welds in the first welding space (14) and the second welding space (15) are welded by using A102 welding rods with a diameter of 3.2-4 mm.

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