Steel pipe welding process

Abstract

The present invention discloses a steel pipe welding processing technology, the process steps of which are: first, an inner conical surface is rolled out at the end of the steel pipe by a round roller, and a connecting sleeve is turned into two tightening surfaces, and then the two steel pipes are pressed into the outside of the connecting sleeve by a press. Since the taper a2 of the tightening surface is greater than the inclination a1 of the inner conical surface, the inner conical surface expands outward again and firmly covers the tightening surface, and the three will not fall off easily. A filling area is formed between the outer conical surface on the steel pipe and the positioning platform. When the positioning platform generates resistance heat under the action of a high-frequency welding machine, its outer side is gradually melted to form a metal fluid. The metal fluid fills the filling area, and the end of the steel pipe is also melted, so that the three are connected into a whole. The welds at various positions are smooth and uniform, and no cracks will appear. The strength of the steel pipe after welding can be guaranteed. At the same time, the welding position is located on the outside of the connecting sleeve. The inner hole diameters of the steel pipe and the connecting sleeve are the same, which will not affect the flow of the fluid.

Description

Technical Field

[0001] The invention discloses a steel pipe welding process, belonging to the technical field of steel pipe processing. Background Art

[0002] Steel pipe is a hollow steel product whose length is much greater than its diameter or circumference. It is categorized by cross-sectional shape into round, square, rectangular, and special-shaped steel pipes; by material, it is categorized into carbon structural steel pipe, low-alloy structural steel pipe, alloy steel pipe, and composite steel pipe; and by application, it is categorized into pipes for transportation pipelines, engineering structures, thermal equipment, the petrochemical industry, machinery manufacturing, geological drilling, and high-pressure equipment.

[0003] Steel pipes are divided into seamless steel pipes and welded steel pipes based on the production process. Seamless steel pipes are manufactured with standard diameters and lengths, which limits their applicability. The length of the steel pipe cannot be adjusted according to actual needs. In practice, several seamless steel pipes are welded together to create a custom steel pipe for the project. Existing steel pipe welding methods mostly involve directly butting two steel pipes together, then manually welding them with welding rods. This method of welding not only makes it easy for the two steel pipes to misalign during fixation, resulting in an uneven weld, but also easily burns through the metal during welding, leading to weld marks and residual slag inside the metal pipe. These weld marks can affect the flow of fluid within the metal pipe. Summary of the Invention

[0004] The purpose of the present invention is to solve the problems in the prior art and to provide a steel pipe welding process.

[0005] The present invention achieves the above-mentioned purpose through the following technical solutions, a steel pipe welding process, comprising the following steps:

[0006] S1: Pickle one end of the two steel pipes to be welded, remove impurities and oxide layers on the surface with sandpaper, and then roll the inner wall of the end with a circular roller to form an inner conical surface with a taper of a1;

[0007] S2: Fix the steel pipe in S1 on a lathe, and use a turning tool to turn the outer circle of the steel pipe into an outer conical surface with a reverse taper of b, and retain a positioning flat surface with a thickness of 0.5-0.1mm at the end of the steel pipe;

[0008] S3: Turning the adapter sleeve, the adapter sleeve has two tightening surfaces with an inclination of a2, where a2>a1, and a positioning platform between the two tightening surfaces. The diameter of the positioning platform is larger than the maximum outer contour diameter of the steel pipe, and the inner diameter of the adapter sleeve is equal to that of the steel pipe;

[0009] S4: Insert one end of the two steel pipes to the outside of the tightening surface of the connecting sleeve through the pressure mechanism until the positioning plane contacts the side of the positioning platform, and a filling area is formed between the outer cone surface and the positioning platform;

[0010] S5: Place the connected steel pipe and the connecting sleeve into the coil of the high-frequency welding machine. The positioning platform is located within the coverage of the coil. When a high-frequency current is passed through the coil, the outer side of the positioning platform generates resistance heat and heats up to a hot-melt state. The metal fluid formed after the local hot melting of the positioning platform will fill the filler area, so that the steel pipe and the connecting sleeve are welded together.

[0011] S6: Remove burrs and residues from the surface of the welded steel pipe and the connecting sleeve, and then grind them smooth.

[0012] Preferably, the high-frequency welding machine includes a high-frequency generator, a coil, a fixed plate, a swing rod and a push rod, the coil includes a fixed ring and a movable ring, both of which are semicircular structures, one end of the fixed ring is fixed on the fixed plate, the swing rod is fixedly connected to the movable ring, and both are rotatably connected to the fixed plate, and the push rod is slidably connected to one end of the swing rod.

[0013] Preferably, when the steel pipe and the connecting sleeve are welded, their center lines are in a vertical state.

[0014] Preferably, when the steel pipe and the connecting sleeve are welded, their center lines are in a horizontal state.

[0015] Preferably, when the steel pipe and the connecting sleeve are welded, the two rotate about their center lines at a rate of 6-10 revolutions / min.

[0016] Preferably, when the steel pipe and the connecting sleeve are welded, carbon dioxide gas is introduced into the outer side and the inner hole of the steel pipe.

[0017] Preferably, the length of the inner conical surface is 1 / 4-1 / 3 of the diameter of the steel pipe.

[0018] Preferably, in the rolling step S1, the steel pipe is fixed on a rotating fixture, and the length of the steel pipe exposed outside the rotating fixture is 2-3 times the length of the inner cone surface. When the steel pipe rotates with the rotating fixture, the circular roller gradually rolls and expands the hole from the inside and outside.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] When welding steel pipes, the positioning plane can ensure that the inner cone surface and the outer cone surface fit in place and form a tight structure, so that the welding area is located on the outside of the connecting sleeve, and there is no weld mark on the inside of the steel pipe, thereby avoiding affecting the flow of fluid inside the steel pipe. A high-frequency welding machine is used to weld the steel pipe and the connecting sleeve, so that the connecting sleeve and the steel pipe generate resistance heat. After heating to a hot-melt state, the generated metal fluid is used to fill the filler area. The three use the same material to ensure that they are connected into a whole after welding, which effectively enhances the welding strength of the steel pipe, especially for thin-walled steel pipe welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the welding of the steel pipe and the connecting sleeve in the present invention;

[0022] Figure 2 This is a schematic structural diagram of the connection between the steel pipe and the adapter sleeve in the present invention;

[0023] Figure 3 It is a partial cross-sectional view of the connection between the steel pipe and the adapter sleeve in the present invention;

[0024] Figure 4 Schematic diagram of the structure of the connection sleeve in the present invention;

[0025] Figure 5 Schematic diagram of the structure of the steel pipe in the present invention;

[0026] Figure 6 This is a schematic diagram of the welding of the steel pipe and the connecting sleeve in Example 2;

[0027] Figure numerals: 1, steel pipe; 2, coil; 3, connecting sleeve; 4, movable ring; 5, outer cone; 6, push rod; 7, swing rod; 8, fixed plate; 9, fixed ring; 10, packing area; 11, positioning platform; 12, tensioning surface; 13, positioning plane; 14, inner cone. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] Example 1

[0030] like Figure 1-Figure 5 As shown, a steel pipe welding process includes the following steps:

[0031] S1: Pickle one end of the two steel pipes 1 to be welded, and use sandpaper to remove impurities and oxide layers on the surface. Then, use a circular roller to roll the inner wall of the end to form an inner conical surface 14 with a taper of a1. The rolling step is to fix the steel pipe 1 on a rotating fixture. The length of the steel pipe exposed outside the rotating fixture is 2-3 times the length of the inner conical surface 14. When the steel pipe 1 rotates with the rotating fixture, the circular roller gradually rolls and expands the hole from the inside to the outside. The length of the inner conical surface 14 is 1 / 4-1 / 3 of the diameter of the steel pipe 1.

[0032] S2: Fix the steel pipe 1 in S1 on a lathe, and use a turning tool to turn the outer cone surface 5 of the outer circle of the steel pipe 1 with a reverse taper of b, and retain a positioning flat surface 13 with a thickness of 0.5-0.1 mm at the end of the steel pipe 1;

[0033] S3: Turning the adapter sleeve 3, the adapter sleeve 3 has two tightening surfaces 12 with an inclination of a2, where a2>a1, and a positioning platform 11 between the two tightening surfaces 12. The diameter of the positioning platform 11 is larger than the maximum outer diameter of the steel pipe 1, and the inner diameter of the adapter sleeve 3 is equal to that of the steel pipe 1;

[0034] S4: Insert one end of the two steel pipes 1 to the outside of the tightening surface 12 of the connecting sleeve 3 through the pressure mechanism until the positioning plane 13 contacts the side of the positioning platform 11, and a filling area 10 is formed between the outer conical surface 5 and the positioning platform 11;

[0035] S5: Put the connected steel pipe 1 and the connecting sleeve 3 into the coil 2 of the high-frequency welding machine. The high-frequency welding machine includes a high-frequency generator, a coil 2, a fixed plate 8, a swing rod 7 and a push rod 6. The coil 2 includes a fixed ring 9 and a movable ring 4, both of which are semicircular structures. One end of the fixed ring 9 is fixed on the fixed plate 8. The swing rod 7 is fixedly connected to the movable ring 4, and the two are rotatably connected to the fixed plate 8. The push rod 6 is slidably connected to one end of the swing rod 7. When the push rod 6 pulls the swing rod 7, the movable ring 4 rotates, and an opening is formed between the movable ring 4 and the fixed ring 9. The steel pipe 1 and the connecting sleeve 3 can be put in from the opening. The midlines of the two are horizontal, and the positioning platform 11 is within the coverage of the coil 2. Then the push rod 6 pushes the swing rod 7, so that the movable ring 4 and the fixed ring 9 are closed. When a high-frequency current is passed through the coil 2, the outer side of the positioning platform 11 generates resistance heat and heats up to a hot-melt state. The metal fluid formed after the local hot melting of the positioning platform 11 will fill the filling area 10, and the steel pipe 1 and the connecting sleeve 3 are rotated at 6-10 revolutions / min along their midlines under the action of the external power mechanism, and carbon dioxide gas is passed into the outer sides and inner holes of both. Then the two steel pipes 1 and the connecting sleeve 3 are welded together;

[0036] S6: Remove burrs and residues from the surfaces of the welded steel pipe 1 and the connecting sleeve 3, and then grind them smooth.

[0037] In this embodiment, when the steel pipe 1 and the connecting sleeve 3 are welded, the center lines of the two are in a horizontal state. In order to prevent the metal fluid formed by the resistance heat of the positioning platform 11 from dripping during welding, the steel pipe 1 and the connecting sleeve 3 are rotated in a directional manner so that the metal fluid flows sideways in the circumferential direction on the outside of the positioning platform 11 due to gravity, and is thus filled into the filling area 10 to ensure that the weld formed between the positioning platform 11 and the steel pipe 1 is uniform. At the same time, the carbon dioxide introduced can have a certain cooling effect on the metal fluid, which can reduce the burn-through and deformation during the welding of the thin-walled steel pipe 1, reduce the hydrogen content of the weld, and prevent the generation of cold cracks, thereby improving the welding strength of the steel pipe 1.

[0038] Example 2

[0039] like Figure 6 As shown, the difference between this embodiment and embodiment 1 is that when the steel pipe 1 and the connecting sleeve 3 are welded, the midline is in a vertical state. When the positioning platform 11 generates resistance heat and heats up to a hot melt state, the generated metal fluid flows downward and covers the filler area 10, so that the steel pipe 1 and the connecting sleeve 3 are more completely covered by the metal fluid, and the welding effect is better. However, during welding, the two steel pipes 1 and the connecting sleeve 3 need to be welded one by one, that is, after welding one steel pipe 1 and the connecting sleeve 3, they are flipped over and welded to the other steel pipe 1 and the connecting sleeve 3.

[0040] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0041] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A steel pipe welding process, characterized in that: The following steps are involved: S1: pickling one end of the two steel pipes (1) to be welded, removing impurities and oxide layers on the surface with sandpaper, and then rolling the inner wall of the end with a circular roller to form an inner conical surface (14) with a taper of a1; S2: Fix the steel pipe (1) in S1 on a lathe, and use a turning tool to turn the outer circle of the steel pipe (1) into an outer conical surface (5) with a reverse taper of b, and retain a positioning plane (13) with a thickness of 0.5-0.1 mm at the end of the steel pipe (1); S3: turning a connecting sleeve (3), wherein the connecting sleeve (3) has two tightening surfaces (12) with an inclination of a2, wherein a2>a1, a positioning platform (11) is provided between the two tightening surfaces (12), the diameter of the positioning platform (11) is larger than the maximum outer diameter of the steel pipe (1), and the inner diameters of the connecting sleeve (3) and the steel pipe (1) are equal; S4: inserting one end of the two steel pipes (1) into the outer side of the tightening surface (12) of the connecting sleeve (3) through the pressure mechanism until the positioning plane (13) contacts the side of the positioning platform (11), and a filling area (10) is formed between the outer conical surface (5) and the positioning platform (11); S5: The connected steel pipe (1) and the connecting sleeve (3) are placed into the coil (2) of the high-frequency welding machine, and the positioning platform (11) is located within the coverage of the coil (2). When a high-frequency current is passed through the coil (2), the outer side of the positioning platform (11) generates resistance heat and heats up to a hot-melt state. The metal fluid formed after the local hot melting of the positioning platform (11) fills the filling area (10), so that the steel pipe (1) and the connecting sleeve (3) are welded together; S6: Remove burrs and residues from the surfaces of the welded steel pipe (1) and the connecting sleeve (3), and then grind them smooth.

2. A steel pipe welding process according to claim 1, characterized in that: The high-frequency welding machine comprises a high-frequency generator, a coil (2), a fixed plate (8), a swing rod (7) and a push rod (6); the coil (2) comprises a fixed ring (9) and a movable ring (4), both of which are semicircular structures; one end of the fixed ring (9) is fixed on the fixed plate (8); the swing rod (7) is fixedly connected to the movable ring (4), and both are rotatably connected to the fixed plate (8); and the push rod (6) is slidably connected to one end of the swing rod (7).

3. A steel pipe welding process according to claim 1, characterized in that: When the steel pipe (1) and the connecting sleeve (3) are welded, their center lines are in a vertical state.

4. A steel pipe welding process according to claim 1, characterized in that: When the steel pipe (1) and the connecting sleeve (3) are welded, their center lines are in a horizontal state.

5. A steel pipe welding process according to claim 4, characterized in that: When the steel pipe (1) and the connecting sleeve (3) are welded, the two rotate about their center lines at a rate of 6-10 revolutions / min.

6. A steel pipe welding process according to claim 3 or 4, characterized in that: When the steel pipe (1) and the connecting sleeve (3) are welded, carbon dioxide gas is introduced into the outer sides and the inner holes thereof.

7. The steel pipe welding process according to claim 1, characterized in that: The length of the inner conical surface (14) is 1 / 4-1 / 3 of the diameter of the steel pipe (1).

8. The steel pipe welding process according to claim 1, characterized in that: The rolling step in step S1 is to fix the steel pipe (1) on the rotating fixture, and the length of the steel pipe (1) exposed outside the rotating fixture is 2-3 times the length of the inner conical surface (14). When the steel pipe (1) rotates with the rotating fixture, the circular roller gradually rolls and expands the hole from the inside and outside.

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