Pipe butt joint welding system and welding method

Abstract

The invention discloses a pipe butt joint welding system and method. The system comprises a first pipe fitting and a second pipe fitting which are in butt joint with each other. The butt joint end of the first pipe fitting is provided with a first groove, and the root of the first groove is provided with a protruding part. A second groove is formed in the butt joint end of the second pipe fitting, and a containing part is arranged at the root of the second groove; the protruding part is embedded into the containing part to form a mechanical interlocking structure which is used for achieving self-positioning when the first pipe fitting and the second pipe fitting are in butt joint. According to the invention, high-quality and high-efficiency one-time forming welding can be realized.

Description

Technical Field

[0001] This invention relates to a pipe butt joint welding system and welding method, belonging to the field of welding technology. Background Technology

[0002] Steel pipe butt joints are widely used in the manufacture of components such as petrochemicals, pressure vessels, and hydraulic cylinders. The quality of the root weld is the weakest link and the key to the performance of the entire welded structure. Its requirements include: full penetration, good back-side formation, no incomplete fusion, no undercut, and no burn-through defects.

[0003] Currently, V-shaped, X-shaped, and U-shaped beveling methods are commonly used, but they have the following problems: ① High assembly dependence, requiring extremely high precision in pipe assembly (misalignment, gap uniformity), otherwise uneven penetration is easily caused; ② Narrow process window, slight deviations in welding parameter control can easily lead to burn-through in thin-walled pipe welding, or incomplete penetration due to insufficient heat input in thick-walled pipe welding; ③ Uncontrollable back-side forming, without the use of backing, the inner surface of the weld is often rough, requiring post-processing, increasing manufacturing costs and cycle time; ④ High skill requirements for welders, especially when welding in difficult positions, quality stability is difficult to guarantee. Although techniques such as inner lining rings, ceramic backing, and root welding exist, they introduce additional equipment and material costs, increase assembly complexity and cleaning procedures, and have poor applicability to small-diameter steel pipes due to limited space.

[0004] Currently, for welding pipe butt joints, the main methods used are to add an inner lining ring or ceramic gasket on the back, or to employ root welding techniques to ensure the quality of the root weld. However, these methods are not suitable due to the limited internal space of small-diameter steel pipes. As a result, the quality of the weld root is often difficult to guarantee, and defects such as burn-through and incomplete penetration are prone to occur. Furthermore, warping and deformation can easily occur, affecting the straightness of the pipe butt joint.

[0005] Existing technologies related to the bevel structure and welding process of steel pipe butt joints include: The invention patent with publication number CN101758335A discloses an improved bevel for mechanically welded butt joints of dissimilar steel pipes. Both sides of the steel pipe bevel are equipped with bosses to control the proportion of deposited metal, thereby ensuring the nickel content at the weld root and solving the metallurgical compatibility problem when welding dissimilar steels. Because this technology uses bosses on both sides of the steel pipe bevel, mechanical interlocking cannot be formed during butt welding, thus requiring very high precision in the pipe joint connection.

[0006] The invention patent with publication number CN1695879A discloses an assembly method for using a positioning plug to ensure the gap at the root of a pipe butt joint. By spot welding an additional positioning plug inside the bevel to fix the gap, not only does it increase the material cost, but it also introduces additional steps of spot welding and plug removal, making the operation cumbersome and potentially affecting the base material.

[0007] Therefore, there is an urgent need in this field for a solution that can simplify the process and fundamentally improve the consistency of root weld quality, starting from the joint bevel itself. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a pipe butt joint welding system and method that achieves high-quality, high-efficiency one-time forming welding. To achieve the above objective, this invention employs the following technical solution: In a first aspect, the present invention provides a pipe butt joint welding system, comprising: a first pipe fitting and a second pipe fitting that are butted together; The first pipe fitting has a first bevel at the mating end, and a protrusion at the root of the first bevel. The second pipe fitting has a second bevel at the mating end, and a receiving portion is provided at the root of the second bevel; The protrusion is embedded in the receiving part to form a mechanical interlocking structure, which is used to realize the self-positioning of the first pipe and the second pipe when they are docked.

[0009] In conjunction with the first aspect, optionally, the protrusion and the receiving portion are in a transitional fit.

[0010] In conjunction with the first aspect, optionally, the protrusion is a boss extending radially outward from the root of the first bevel along the first pipe fitting, wherein the axial length L of the boss is 5-10 mm and the radial thickness t is 3-5 mm.

[0011] In conjunction with the first aspect, optionally, the receiving portion is a groove that is recessed radially inward from the root of the second bevel along the second pipe fitting, wherein the axial length L of the groove is 5-10 mm and the radial thickness t is 3-5 mm.

[0012] In conjunction with the first aspect, optionally, the connection between the protrusion and the first bevel is provided with a first blunt edge, and the connection between the receiving portion and the second bevel is provided with a second blunt edge; When the protrusion and the receiving portion are fitted together, a gapless connection is formed between the first blunt edge and the second blunt edge.

[0013] In a second aspect, the present invention provides a welding method for welding a pipe butt joint welding system as described in the first aspect, comprising: The protrusion of the first pipe fitting is embedded into the receiving part of the second pipe fitting, and the connection between the first pipe fitting and the second pipe fitting is achieved by using a mechanical interlocking structure. The joint is welded using preset welding parameters.

[0014] In conjunction with the second aspect, optionally, the preset welding parameters include welding parameters for the root pass welding, which include: welding current of 200-220A, welding voltage of 21-22V, and welding speed of 6-7mm / s.

[0015] In conjunction with the second aspect, optionally, the preset welding parameters include welding parameters for filler and cover welding, which include: welding current of 260-280A, welding voltage of 26-28V, and welding speed of 6-7mm / s.

[0016] In conjunction with the second aspect, optionally, the welded joint includes: The first and second pipe fittings, which have been joined together, are rotated at a constant speed around their common axis using a flipping machine to ensure that the welding operation is always in a flat welding position.

[0017] In conjunction with the second aspect, optionally, after welding is completed, the root quality of the weld is subjected to non-destructive testing.

[0018] Compared with the prior art, the beneficial effects achieved by the pipe butt joint welding system and welding method provided in the embodiments of the present invention include: The present invention provides a pipe butt joint welding system comprising: a first pipe fitting and a second pipe fitting that are butt-jointed; the first pipe fitting has a first bevel at the butt end, and a protrusion at the root of the first bevel; the second pipe fitting has a second bevel at the butt end, and a receiving portion at the root of the second bevel; the protrusion is embedded in the receiving portion to form a mechanical interlocking structure; the present invention enables the first pipe fitting and the second pipe fitting to have a self-positioning function when butt-jointed, which can reduce the dependence on high-precision tooling fixtures and operator experience, effectively avoid misalignment problems, and improve assembly efficiency and accuracy; The welding method provided by this invention utilizes preset welding parameters to weld the butt joint. This invention, through a mechanical interlocking structure, provides reliable support for the molten pool while working in conjunction with optimized welding parameters to ensure full penetration of the root weld and good back-side formation. It solves the defects such as incomplete penetration and burn-through that are prone to occur in traditional methods, making the weld quality independent of the welder's personal skills. This invention achieves high-quality, high-efficiency one-time forming welding through the synergistic effect of a mechanical interlocking structure and optimized welding parameters. This invention eliminates the need for additional auxiliary components such as inner lining rings, ceramic gaskets, or positioning plugs, thus saving the corresponding installation, tack fixing, and cleaning processes. This not only simplifies the assembly and welding process and reduces material and labor costs, but also makes this invention particularly suitable for small-diameter steel pipe docking scenarios with limited internal space. This invention is applicable to pipe fittings made of various materials such as carbon steel and stainless steel. By achieving high-quality one-time forming welding, it significantly reduces the rework rate and scrap rate. Although the initial cost of beveling increases slightly, the overall manufacturing cost is greatly reduced, resulting in outstanding economic benefits and application value. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a pipe butt joint welding system provided in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the structure of the first pipe fitting in a pipe butt joint welding system provided in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the structure of the second pipe fitting in a pipe butt joint welding system provided in Embodiment 1 of the present invention.

[0020] In the picture: 1. First pipe fitting; 11. Protrusion; 12. First blunt edge; 2. Second fitting; 21. Receiving portion; 22. Second blunt edge; 3. Apply the root weld. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0022] Example 1

[0023] like Figure 3 As shown, this embodiment provides a pipe butt joint welding system, including: a first pipe fitting 1 and a second pipe fitting 2 that are butt-jointed.

[0024] In this embodiment, the outer diameter of the first pipe fitting 1 and the inner diameter of the second pipe fitting 2 are ΦD and Φd respectively.

[0025] like Figure 1 and Figure 3 As shown, the first pipe fitting 1 has a first bevel at the connecting end, a protrusion 11 at the root of the first bevel, and a first blunt edge 12 at the connection between the protrusion 11 and the first bevel.

[0026] like Figure 2 and Figure 3 As shown, the second pipe fitting 2 has a second bevel at the connecting end, a receiving part 21 at the root of the second bevel, and a second blunt edge 22 at the connection between the receiving part 21 and the second bevel.

[0027] The bevel types for the first and second bevels can be selected from V-shaped, U-shaped, etc., depending on the wall thickness and ease of processing.

[0028] like Figure 1 and Figure 2 As shown, in this embodiment, the first bevel and the second bevel are V-shaped, and the angle of the bevel surface is α.

[0029] like Figure 1 As shown, the protrusion 11 is a boss that extends radially outward from the root of the first bevel along the first pipe fitting 1. The axial length of the boss is L, and the radial thickness is t. Therefore, the outer diameter of the boss is Φd+2t. The first blunt edge 12 is provided at the connection between the boss and the first bevel. The radial thickness of the first blunt edge 12 is m.

[0030] In this embodiment, the axial length L of the boss is 5-10mm, the radial thickness t is 3-5mm, and the radial thickness m of the first blunt edge 12 is 1-2mm.

[0031] like Figure 2 As shown, the receiving portion 21 is a groove that is recessed radially inward from the root of the second bevel along the second pipe fitting 2. The axial length of the groove is L, and the radial thickness is t. Therefore, the inner diameter of the groove is Φd+2t. The second blunt edge 22 is provided at the connection between the boss and the second bevel. The radial thickness of the second blunt edge 22 is m.

[0032] In this embodiment, the axial length L of the groove is 5-10 mm, the radial thickness t is 3-5 mm, and the radial thickness m of the second blunt edge 22 is 1-2 mm.

[0033] like Figure 3 As shown, the protrusion 11 is embedded in the receiving part 21 to form a mechanical interlocking structure, which is used to realize the self-positioning of the first pipe fitting 1 and the second pipe fitting 2 during docking. When the protrusion 11 and the receiving part 21 are fitted together, a gapless docking is formed between the first blunt edge 12 and the second blunt edge 22.

[0034] In this embodiment, the protrusion 11 and the receiving portion 21 are in a transition fit.

[0035] This embodiment is applicable to pipe fittings made of various materials such as carbon steel and stainless steel. By achieving high-quality one-time forming welding, it significantly reduces the rework rate and scrap rate. Although the initial cost of beveling increases slightly, the overall manufacturing cost is greatly reduced, resulting in outstanding economic benefits and application value.

[0036] This embodiment provides a mechanical interlocking structure formed by the protrusion embedded in the receiving part, which supports the molten pool and enables the first and second pipe fittings to have a self-positioning function when docking. This reduces the reliance on high-precision tooling fixtures and operator experience, effectively avoids misalignment problems, and improves assembly efficiency and accuracy.

[0037] Example 2

[0038] This embodiment provides a welding method for the pipe butt joint welding system described in Embodiment 1, including: The protrusion 11 of the first pipe fitting 1 is embedded into the receiving part 21 of the second pipe fitting 2, and the connection between the first pipe fitting 1 and the second pipe fitting 2 is achieved by using a mechanical interlocking structure. The joint is welded using preset welding parameters.

[0039] In this embodiment, a mixed gas shielded welding is used. Specifically, the welding shielding gas is a mixture of 80% Ar and 20% CO2.

[0040] In this embodiment, to ensure the performance of the weld, the performance of the welding material is matched with that of the steel pipe, and the diameter of the welding wire is φ1.2mm.

[0041] The preset welding parameters include those for the root pass and those for the fill and cover passes. The root pass is performed first, resulting in the following: Figure 3 The root weld 3 shown is followed by filling and capping welds.

[0042] During the root pass welding, fill pass welding, and cover pass welding, the first pipe fitting 1 and the second pipe fitting 2, which have been joined together, are rotated at a constant speed around their common axis using a turning machine, so that the welding operation is always in the flat welding position.

[0043] It should be noted that during uniform rotation, the first pipe 1 and the second pipe 2 remain relatively stationary and do not produce any displacement in any direction.

[0044] In this embodiment, the welding parameters for the root pass welding include: welding current of 200-220A, welding voltage of 21-22V, and welding speed of 6-7mm / s.

[0045] In this embodiment, the welding parameters for filling and capping welding include: welding current of 260-280A, welding voltage of 26-28V, and welding speed of 6-7mm / s.

[0046] As a further improvement, after welding is completed, the root quality of the weld is subjected to non-destructive testing.

[0047] This embodiment provides welding parameters for the root pass, fill pass, and cap pass, offering clear and reliable process guidance for on-site operations. This makes the embodiment easy to master and standardize, ensuring high-quality welded joints can be obtained under various production conditions.

[0048] The welding method provided in this embodiment does not require additional auxiliary components such as inner lining rings, ceramic gaskets, or positioning plugs, eliminating the corresponding installation, tack fixing, and cleaning procedures. This not only simplifies the assembly and welding process and reduces material and labor costs, but also makes this embodiment particularly suitable for small-diameter steel pipe docking scenarios with limited internal space.

[0049] This embodiment, through the synergistic effect of a mechanical interlocking structure and optimized welding parameters, ensures full penetration of the root weld and good back-side formation; it solves the defects such as incomplete penetration and burn-through that are prone to occur in traditional methods, making the weld quality independent of the welder's personal skills.

[0050] This embodiment achieves high-quality, high-efficiency one-time forming welding through the synergistic effect of a mechanical interlocking structure and optimized welding parameters.

[0051] Example 3

[0052] This embodiment uses a Q355 steel pipe as an example to illustrate the pipe butt joint welding system provided in Embodiment 1 and the welding method provided in Embodiment 2.

[0053] In this embodiment, the outer diameter φD of the first pipe fitting and the inner diameter φd of the second pipe fitting are 150mm and 110mm respectively.

[0054] The specific implementation steps of this embodiment are as follows.

[0055] Step 1: Process the first and second pipe fittings.

[0056] The first and second bevels are V-shaped, with an angle α of 30° on the bevel face.

[0057] In the beveling process of the first pipe fitting, a boss extending radially outward from the root of the first bevel is machined. The axial length of the boss is L=5mm, the radial thickness is t=3mm, the outer diameter of the boss is φ(d+2t)=116mm, and a first blunt edge with a radial thickness of m=1mm is machined.

[0058] In the beveling process of the second pipe fitting, a groove is machined at the root of the second bevel, which is recessed radially inward along the second pipe fitting. The axial length of the groove is L=5mm, the radial thickness is t=3mm, the inner diameter of the groove is φ(d+2t)=116mm, and a second blunt edge with a radial thickness of m=1mm is machined.

[0059] To ensure the self-positioning effect of the first and second pipe fittings, the boss of the first pipe fitting and the groove of the second pipe fitting are transition fits with a tolerance of H7 / js6. Specifically, the maximum inner diameter of the groove of the second pipe fitting is 116.035mm and the minimum inner diameter is 116.000mm; the maximum outer diameter of the boss of the first pipe fitting is 116.011mm and the minimum outer diameter is 115.989mm.

[0060] Step 2: Insert the boss of the first pipe fitting into the groove of the second pipe fitting, and use the mechanical interlocking structure to connect the first pipe fitting and the second pipe fitting.

[0061] After docking, there is no gap between the first and second pipe fittings at the blunt edge.

[0062] Step 3: Using gas shielded welding with preset welding parameters, weld the butt joint.

[0063] Specifically, ER50-6 welding wire with a diameter of φ1.2mm is selected. The welding shielding gas is a mixture of 80% Ar and 20% CO2.

[0064] To ensure weld quality, the welding position is flat welding. During the welding process, a turning machine is used to drive the first and second pipe fittings, which have been joined together, to rotate at a constant speed around their common axis.

[0065] The welding parameters for the root pass include: welding current of 200-220A, welding voltage of 21-22V, and welding speed of 6-7mm / s.

[0066] The welding parameters for filler and cover welding include: welding current of 260-280A, welding voltage of 26-28V, and welding speed of 6-7mm / s.

[0067] After welding, the quality of the weld was inspected using ultrasound and endoscopy. No defects such as incomplete penetration or burn-through were found at the root of the weld, and the back of the weld was well formed.

[0068] This embodiment demonstrates that high-quality, high-efficiency one-step welding can be achieved through the synergistic effect of a mechanical interlocking structure and optimized welding parameters.

[0069] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A pipe butt joint welding system, characterized in that, include: The first fitting (1) and the second fitting (2) are connected to each other; The first pipe fitting (1) has a first bevel at the joint end, and a protrusion (11) is provided at the root of the first bevel. The second pipe fitting (2) has a second bevel at the joint end, and a receiving part (21) is provided at the root of the second bevel. The protrusion (11) is embedded in the receiving part (21) to form a mechanical interlock structure, which is used to realize the self-positioning of the first pipe (1) and the second pipe (2) when they are docked.

2. The pipe butt joint welding system according to claim 1, characterized in that, The protrusion (11) and the receiving part (21) are in a transition fit.

3. The pipe butt joint welding system according to claim 1, characterized in that, The protrusion (11) is a boss that extends radially outward from the root of the first bevel along the first pipe fitting (1). The axial length L of the boss is 5-10 mm and the radial thickness t is 3-5 mm.

4. The pipe butt joint welding system according to claim 1, characterized in that, The receiving portion (21) is a groove that is recessed radially inward from the root of the second bevel along the second pipe (2), and the axial length L of the groove is 5-10mm and the radial thickness t is 3-5mm.

5. The pipe butt joint welding system according to claim 1, characterized in that, The protrusion (11) is provided with a first blunt edge (12) at the connection between it and the first bevel, and the receiving part (21) is provided with a second blunt edge (22) at the connection between it and the second bevel. When the protrusion (11) and the receiving portion (21) are fitted together, a gapless connection is formed between the first blunt edge (12) and the second blunt edge (22).

6. A welding method for welding a pipe butt joint welding system as described in any one of claims 1-5, characterized in that, include: The protrusion (11) of the first pipe fitting (1) is embedded into the receiving part (21) of the second pipe fitting (2), and the first pipe fitting (1) and the second pipe fitting (2) are connected by a mechanical interlocking structure. The joint is welded using preset welding parameters.

7. The welding method according to claim 6, characterized in that, The preset welding parameters include the welding parameters for the root pass welding, which include: welding current of 200-220A, welding voltage of 21-22V, and welding speed of 6-7mm / s.

8. The welding method according to claim 6, characterized in that, The preset welding parameters include welding parameters for filler and cover welding, which include: welding current of 260-280A, welding voltage of 26-28V, and welding speed of 6-7mm / s.

9. The welding method according to claim 6, characterized in that, The welded joint includes: The first pipe fitting (1) and the second pipe fitting (2) that have been docked by using a flipping machine are rotated at a constant speed around their common axis so that the welding operation is always in the flat welding position.

10. The welding method according to claim 6, characterized in that, After welding is completed, the root quality of the weld is subjected to non-destructive testing.

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