A method for assembling and welding a variable cross-section square tube

Abstract

This invention discloses a method for assembling and welding variable cross-section square tubes, comprising: marking bending lines on laser-cut steel plate workpieces, and bending them to 90° along the bending lines using a bending machine and a conical die; pairing the bent steel plates together, placing them on copper pads supported by jacks for leveling and spot welding; feeding the workpieces, jacks, and copper pads into an openable T-shaped assembly device, hydraulically closing it, and clamping it with bolts and jacks; welding using a submerged arc welding machine, and inspecting the weld appearance and weld reinforcement; and grinding the weld by moving a grinding wheel along a track driven by a motor. This method constrains the area around the weld during the welding process, reducing welding twisting and deformation of large-size variable cross-section square tubes, and improving assembly and welding efficiency and finished product consistency.

Description

Technical Field

[0001] This invention relates to the field of steel structure processing and fabrication technology, and more specifically, to a method for welding variable cross-section square tubes. Background Technology

[0002] Variable cross-section square tubes are also known as reducing square tubes. Current processing technology for reducing square tubes is mainly based on the principle of metal plastic forming, resulting in processing methods such as diameter reduction or diameter expansion pressing. Diameter reduction or expansion pressing typically uses axial pressure to change the diameter of the tube within a mold, making it suitable for small cross-section tubes with wall thicknesses of 0.5mm to 2mm. When the square tube has a thicker wall, higher material strength, or larger cross-sectional dimensions, the processing difficulty using this type of pressing method increases significantly.

[0003] For large-sized variable cross-section square tubes with a cross-sectional dimension greater than 150mm, forming is typically achieved through steel plate bending, assembly, and welding. However, uneven heating and cooling during the welding process can easily cause various deformations: long welds may cause overall component twisting or angular deformation, longitudinal shrinkage may cause bending and deflection, and transverse shrinkage may cause cross-sectional twisting or misalignment. These deformations affect the dimensional accuracy and structural stability of the finished product and increase the workload of subsequent straightening and grinding, hindering stable and efficient production.

[0004] Therefore, it is necessary to develop a welding process for large-size variable cross-section square tubes, which can stably position and clamp the workpiece during the assembly and welding stage, and continuously connect bending, assembly and welding, and post-weld grinding to reduce welding deformation and improve production efficiency. Summary of the Invention

[0005] In view of the problems existing in the prior art, the purpose of the present invention is to provide a welding process for variable cross-section square tubes, so as to solve the problems that large-size variable cross-section square tubes are prone to twisting, angular deformation, bending and deflection, cross-sectional distortion or misalignment when welded, and the low efficiency of positioning, welding and grinding connection during the welding process.

[0006] The present invention adopts the following technical solution:

[0007] A method for assembling and welding a variable cross-section square tube includes the following steps:

[0008] S1. Bending: Mark the bending line on the steel plate workpiece obtained by laser cutting, use a bending machine to align the conical mold with the bending line, and bend the steel plate workpiece along the bending line to 90° to obtain a bent steel plate.

[0009] S2. Pairing and pre-fixing: Pair the bent steel plates in pairs and place them on copper pads. The copper pads are supported by jacks. After adjusting the level of both ends by the jacks, spot weld the paired bent steel plates for pre-fixing.

[0010] S3. Assembly and clamping: With the assembly device in the open state, the pre-fixed bent steel plate, along with the jack and copper pad, is sent into the assembly device; the assembly device is closed by hydraulic action, the bolts are tightened, and the upper surface of the square tube is made to fit against the upper surface of the assembly device by the jack, thereby clamping and fixing the bent steel plate.

[0011] S4. Welding: While keeping the steel plate clamped, use a submerged arc welding machine to weld the seam of the bent steel plate; after welding, check the appearance of the weld and the weld reinforcement.

[0012] S5. Grinding: The grinding wheel is driven by a motor to rotate and move along the track to grind the weld evenly, resulting in a variable cross-section square tube.

[0013] Furthermore, lasers are used to cut the steel plate workpiece and to mark the bending lines at the required bending locations.

[0014] Furthermore, the variable cross-section square tube is a variable cross-section square tube with a cross-sectional dimension greater than 150mm.

[0015] Furthermore, copper pads are placed at both ends of the pre-fixed bent steel plates, and the height of the two ends is adjusted by jacks to keep the paired bent steel plates horizontal.

[0016] Furthermore, the assembly device is a T-shaped structure welded from steel plates and can be opened or closed under hydraulic pressure. When the assembly device is opened, a pre-fixed bent steel plate is fed in. After being fed in, the assembly device is closed and bolts and jacks are used to tighten the bent steel plate.

[0017] Furthermore, the opening and closing of the assembly device is driven by a hydraulic mechanism that includes hydraulic rods and a rotating shaft.

[0018] Furthermore, the bent steel plate is kept clamped during the welding process to constrain the area around the weld.

[0019] Furthermore, the track is set along the extension direction of the weld, and while the motor drives the grinding wheel to rotate, the grinding wheel moves along the track.

[0020] Furthermore, the processing method is carried out in three stages in sequence: steel plate bending, square tube assembly and welding, and finished product grinding.

[0021] Beneficial effects

[0022] 1. Significantly reduces welding deformation. During the welding process, bolts and jacks, along with the assembly device and copper pads, firmly clamp the bent steel plate, keeping the area around the weld under constraint during welding. This reduces the twisting and deformation caused by shrinkage in the heat-affected zone, which helps improve the dimensional accuracy and structural stability of the finished product.

[0023] 2. Improve assembly and welding efficiency. The T-shaped assembly device opens and closes under hydraulic pressure and works with jacks, copper pads, and bolts to achieve rapid positioning, clamping, and welding of bent steel plates. After welding, a grinding wheel that moves along the track is used for grinding, reducing the time for workpiece handling and reclamping.

[0024] 3. It has good adaptability. Bending, assembly welding and finished product grinding form interconnected processing links. With adjustable jacks, copper pads and conical molds, it can be used to process square tubes of different sizes or steel plate components with similar right angle bending. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the bending line of a steel plate workpiece according to an embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of a steel plate workpiece being bent according to an embodiment of the present invention;

[0027] Figure 3 This is a left view of a steel plate workpiece being bent according to an embodiment of the present invention;

[0028] Figure 4 This is a schematic diagram of a steel plate workpiece and a copper pad assembled according to an embodiment of the present invention;

[0029] Figure 5 This is a schematic diagram of a bent steel plate being pushed into the assembly device according to an embodiment of the present invention;

[0030] Figure 6 This is a schematic diagram of the assembly device when it is opened according to an embodiment of the present invention;

[0031] Figure 7 This is a schematic diagram of the assembly device after it is closed according to an embodiment of the present invention;

[0032] Figure 8 This is a front view of a submerged arc welding machine according to an embodiment of the present invention;

[0033] Figure 9 This is a top view of a submerged arc welding machine according to an embodiment of the present invention;

[0034] Figure 10 This is a schematic diagram of the polishing process according to an embodiment of the present invention.

[0035] Reference numerals: 1. Conical mold; 2. Bending machine; 3. Workpiece; 4. Assembly device; 5. Hydraulic rod; 6. Shaft; 7. Bolt; 8. Jack; 9. Submerged arc welding machine; 10. Copper pad; 11. Grinding wheel; 12. Motor; 13. Track. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0037] As shown in the figure, this embodiment provides a method for welding a variable cross-section square tube, including the following steps:

[0038] Step S1: Steel plate cutting and bending

[0039] This invention relates to large-size variable cross-section square tubes formed by welding, and is particularly suitable for reducing square tubes with a cross-section greater than 150mm. First, the steel plate is laser-cut according to the shape of the variable cross-section square tube to obtain a steel plate workpiece 3 with a cross-sectional dimension that changes along the length direction; then, bending lines 31 are marked by laser at the locations where bending is required.

[0040] The steel plate workpiece 3 is placed on the bending machine 2, and the conical die 1 is aligned with the bending line on the steel plate workpiece 3. The bending machine 2 is started, and the steel plate workpiece 3 is bent to 90° along the bending line to obtain a bent steel plate for subsequent pairing. The above blanking and bending operations are performed sequentially on each steel plate workpiece 3 in the same batch.

[0041] Step S2: Pairing, leveling, and pre-fixing

[0042] After bending, the bent steel plates are paired up in pairs, forming the bent steel plate workpieces. The paired bent steel plates are placed on copper pads 10, which are supported by jacks 8. The height of both ends is adjusted by the jacks 8 to ensure that the ends of the paired workpieces are level. After the position adjustment is completed, the two bent steel plates are pre-fixed by spot welding to maintain their paired state during the feeding into the assembly device 4.

[0043] Step S3: Feed into the assembly device and clamp and position.

[0044] The assembly device 4 is a T-shaped structure welded from steel plates and can be opened or closed under hydraulic pressure. The opening and closing structure of the assembly device 4 includes a hydraulic rod 5 and a rotating shaft 6. The assembly device 4 is kept in the open state before the workpiece is fed in.

[0045] like Figure 9 The pre-fixed bent steel plate, along with jack 8 and copper pad 10, is pushed into assembly device 4. After the workpiece is in place, assembly device 4 is closed by hydraulic action, and bolts 7 are tightened to horizontally secure the bent steel plate. At the same time, jack 8 is operated to lift the workpiece with copper pad 10 until the upper surface of the square tube is in close contact with the upper surface of assembly device 4, thereby firmly fixing the bent steel plate.

[0046] The assembly device 4 has multiple fastening positions along the length of the workpiece, thereby forming multi-point constraints in the extension direction of the long weld. Through the cooperation of bolts 7, jacks 8, copper washers 10 and assembly device 4, the area around the weld is kept in a constrained state during subsequent welding.

[0047] Step S4: Submerged arc welding and weld inspection

[0048] like Figure 10 As shown, after clamping and positioning, the submerged arc welding machine 9 is used to weld along the weld seam of the bent steel plate without releasing the clamping. During the welding process, the bent steel plate is continuously constrained by the assembly device 4, bolts 7, and jacks 8 to reduce twisting, angular deformation, bending deflection, cross-sectional distortion, or misalignment caused by uneven heating and cooling. After welding, the appearance of the weld and the weld reinforcement are inspected.

[0049] Step S5: Weld grinding

[0050] After welding is completed and inspected, the weld is ground with a grinding wheel 11. The motor 12 drives the grinding wheel 11 to rotate at high speed, and the grinding wheel 11 moves along the track 13. The track 13 is arranged along the extension direction of the weld, so that the grinding wheel 11 can move continuously along the weld to ensure that the weld is ground evenly.

[0051] Assembly welding process

[0052] This processing method proceeds in the following sequence: steel plate blanking and bending, pairing, leveling and pre-fixing, feeding into the assembly device and clamping and positioning, submerged arc welding and weld inspection, and weld grinding. Utilizing the opening and closing of the assembly device 4, along with the cooperation of the jack 8, copper pad 10, and bolts 7, positioning and clamping can be completed after the workpiece is fed in, and post-weld track-type grinding is performed, thus forming the assembly and welding process for the variable cross-section square tube.

Claims

1. A method for assembling and welding a variable cross-section square tube, characterized in that: Includes the following steps: S1. Mark the bending line on the steel plate workpiece (3) obtained by laser cutting, use the bending machine (2) to align the conical mold (1) with the bending line, and bend the steel plate workpiece (3) along the bending line to 90° to obtain a bent steel plate. S2. Pair the bent steel plates in pairs and place them on the copper pad (10). The copper pad (10) is supported by the jack (8). After adjusting the two ends to be horizontal by the jack (8), spot weld the paired bent steel plates to pre-fix them. S3. Put the assembly device (4) in the open state, send the pre-fixed bent steel plate together with the jack (8) and the copper pad (10) into the assembly device (4), close the assembly device (4) by hydraulic action, tighten the bolt (7), and use the jack (8) to make the upper surface of the square tube fit against the upper surface of the assembly device (4) to clamp the bent steel plate. S4. While keeping the plate clamped, use a submerged arc welding machine (9) to weld the weld seam of the bent steel plate, and check the appearance of the weld seam and the weld reinforcement after welding. S5. The grinding wheel (11) is driven to rotate by the motor (12) and the grinding wheel (11) moves along the track (13) to grind the weld seam and obtain a variable cross-section square tube.

2. The assembly welding method for a variable cross-section square tube according to claim 1, characterized in that: In step S1, the steel plate workpiece (3) is cut using a laser, and the bending line is marked at the position where bending is required using a laser.

3. The assembly welding method for a variable cross-section square tube according to claim 1, characterized in that: The variable cross-section square tube is a variable cross-section square tube with a cross-sectional dimension greater than 150mm.

4. The assembly welding method for a variable cross-section square tube according to claim 1, characterized in that: In step S2, the copper pad (10) is placed at both ends of the pre-fixed bent steel plate, and the height of both ends is adjusted by the jack (8) to keep the paired bent steel plates horizontal.

5. The assembly welding method for a variable cross-section square tube according to claim 1, characterized in that: The assembly device (4) is a T-shaped structure welded from steel plates. Before the pre-fixed bent steel plate is fed in, the assembly device (4) remains open. After the pre-fixed bent steel plate is fed in, the assembly device (4) closes.

6. The assembly welding method for a variable cross-section square tube according to claim 5, characterized in that: The opening and closing of the assembly device (4) is driven by a hydraulic mechanism including a hydraulic rod (5) and a rotating shaft (6).

7. The assembly welding method for a variable cross-section square tube according to claim 1, characterized in that: In step S3, the bent steel plate is fastened by the bolt (7), and the copper pad (10) is lifted by the jack (8) so that the upper surface of the square tube is in close contact with the upper surface of the assembly device (4).

8. The assembly welding method for a variable cross-section square tube according to claim 1, characterized in that: During the welding process in step S4, the clamping state formed in step S3 is maintained to constrain the area around the weld.

9. The assembly welding method for a variable cross-section square tube according to claim 1, characterized in that: In step S5, the track (13) is set along the extension direction of the weld, and the motor (12) drives the grinding wheel (11) to rotate while the grinding wheel (11) moves along the track (13).

10. The assembly welding method for a variable cross-section square tube according to claim 1, characterized in that: Step S1 constitutes the steel plate bending stage, steps S2 to S4 constitute the square tube assembly and welding stage, and step S5 constitutes the finished product grinding stage.

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