Large-span bridge steel truss welding device and process

Abstract

The invention relates to the technical field of bridge steel trusses, and discloses a large-span bridge steel truss welding device and technology.The large-span bridge steel truss welding device comprises a box body and a welding prefabricated part, the welding prefabricated part is composed of two diagonal rods and a vertical rod, and the welding prefabricated part is welded to the box body; an electric driving rail is arranged on the inner top face of the box body, a mechanical arm is arranged in the electric driving rail, a welding head is arranged at the bottom end of the mechanical arm, a welding prefabricated part of a triangular rod structure is limited through a limiting mechanism, the welding prefabricated part can be jacked up through a jacking mechanism, and after the welding prefabricated part is jacked up to a certain radian, the welding prefabricated part is automatically jacked up. The mechanical arm and the welding head in the box body can be used for conveniently and rapidly welding different faces of the welding position of the welded prefabricated part, each welding seam of the welding position can be welded, welding is uniform, welding of the welded prefabricated part is facilitated, and the problem that different faces of the welded prefabricated part of the bridge steel truss are inconvenient to weld is solved.

Description

Technical Field

[0001] The invention relates to the technical field of bridge steel trusses, and in particular to a welding device and process for a large-span bridge steel truss. Background Art

[0002] Bridge steel truss is a structural form commonly used in bridge construction. It is mainly made of steel and uses a truss structure (i.e. a frame structure of a triangle or other geometric shape composed of a series of rods) to support the bridge deck and other loads. The design of the steel truss gives the structure a high load-bearing capacity while being relatively light and able to effectively share forces in different directions. Due to its excellent mechanical properties, steel trusses are widely used in large-span bridges, railway bridges, highway bridges and other fields.

[0003] The welding of bridge steel trusses usually requires the pre-welding of several prefabricated parts (such as prefabricated parts of a triangular rod structure composed of two diagonal rods and a vertical rod), and then the prefabricated parts are welded to the upper chord and the lower chord on site by large-scale welding equipment. When welding the diagonal rods and the vertical rods, it is not convenient for manpower to move or flip the diagonal rods and the vertical rods as they are heavy and have a certain angle, which causes trouble for welding different surfaces of the welding point.

[0004] To this end, the present invention provides a long-span bridge steel truss welding device and process. Summary of the invention

[0005] In order to make up for the deficiencies of the prior art, at least one technical problem raised in the background technology is solved.

[0006] The present invention provides a welding device for a steel truss of a large-span bridge, comprising a box body and a welding prefabricated part, wherein the welding prefabricated part is composed of two diagonal rods and a vertical rod, and the welding prefabricated part is welded in the box body, and an electric drive track is arranged on the top surface of the box body, and a mechanical arm is arranged on the electric drive track, and a welding head is arranged on the bottom end of the mechanical arm, and the welding head is used to weld the welding prefabricated part, and a limiting mechanism is arranged in the box body, and the limiting mechanism is used to support the diagonal rods and the vertical rods, and a lifting mechanism is arranged on the inner bottom surface of the box body, and the lifting mechanism is used to lift the welding prefabricated part, and a heat recovery mechanism is arranged in the box body, and the heat recovery mechanism is used to recover the heat of welding exhaust gas and preheat and slowly cool the welding prefabricated part, and the side wall of the box body is also provided with a debris removal mechanism, and the debris removal mechanism is used to discharge welding waste.

[0007] Preferably, the limiting mechanism includes a main support frame and a secondary support frame arranged at the bottom of the box body, support frames are fixedly connected between the main support frame and the secondary support frame and the opposite surfaces of the box body, the front end surface of the box body is rotatably connected to a flip door through a hinge, and three guide frames are fixedly connected to the flip door, and several of the guide frames are arranged on the top of the main support frame and the secondary support frame, the inner wall of the box body is fixedly connected to a cylinder, and the output end of the cylinder is fixedly connected to a limiting block, the limiting block is arranged in a fit with the top side wall of the welding prefabricated part, the limiting mechanism can support the welding prefabricated part, and the limiting block can press against the welding prefabricated part to facilitate welding.

[0008] Preferably, the lifting mechanism includes a hydraulic cylinder and an electromagnet plate, the hydraulic cylinder is arranged on the inner bottom surface of the box body, a mounting seat is fixedly connected to the inner bottom surface of the box body, and the mounting seat is fixedly connected to the hydraulic cylinder, the hydraulic cylinder is inclined, and an electromagnet plate is rotatably arranged on the output end of the hydraulic cylinder, and the electromagnet plate is arranged between the main support frame and the auxiliary support frame. When the welding prefabricated part is lifted to a certain arc, the mechanical arm and welding head in the box body can conveniently weld different surfaces of the welding prefabricated part, and can weld each weld at the welding joint, so that the welding is more uniform, which is beneficial to the welding of the welding prefabricated part.

[0009] Preferably, the heat recovery mechanism includes an air pump 1 fixedly connected to the bottom surface of the box body, the input end of the air pump 1 is fixedly connected to the frame, and a filter is fixedly connected to the frame, the side wall of the box body is fixedly connected to a support plate, and the top surface of the support plate is fixedly connected to a heat exchanger, the top surface of the box body is fixedly connected to a pressure vessel, the input end of the air pump 1 is fixedly connected to the input end of the heat exchanger, the output end of the heat exchanger is fixedly connected to the pressure vessel, a one-way valve is installed in the pipeline between the heat exchanger and the pressure vessel, the inner top surface of the box body is fixedly connected to a shell, and an air pump 2 is installed in the shell, and the input end of the air pump 2 is connected to the pressure vessel A pipeline is fixedly connected between the two, and another one-way valve is installed in the pipeline. The second output end of the air pump is fixedly connected with a jet pipe, and the jet pipe is threadedly connected with a jet hood, and the jet hood faces the welding prefabricated part. An adjusting mechanism is arranged in the box body, and the adjusting mechanism is used to adjust the height of the jet hood. The exhaust gas can heat other gases. The heated gas is transported to the pressure vessel for temporary storage, and is pressurized by the second air pump and sent to the jet pipe and the jet hood, so as to spray the welding prefabricated part, thereby realizing the effects of preheating before welding and slow cooling after welding, and solving the problem of cracks in the welding part caused by excessive welding temperature.

[0010] Preferably, the adjustment mechanism includes a motor fixedly connected to the top surface of the box body, the output end of the motor passes through the box body to extend into the interior and is fixedly connected to a screw rod, a movable plate is threadedly connected to the screw rod, the jet pipe passes through the movable plate and is threadedly connected to the movable plate, the jet pipe is a hose, and the jet hood can move up and down to adapt to the height of the welding point after the welding prefabricated part is lifted up, so that the hot air is always sprayed on the welding point, thereby achieving a better slow cooling effect at the welding point.

[0011] Preferably, the debris discharge mechanism includes a triangular block fixedly connected to the top surface of the box body, the side of the box body is fixedly connected to a waste box, the hydraulic cylinder is buried in the triangular block, and the gas sprayed from the jet hood blows the welding waste slag on the triangular block to make it fall into the waste box for discharge, thereby avoiding the accumulation of too much welding waste slag.

[0012] Preferably, a limiting rod is fixedly connected to the inner top surface of the box body, and the limiting rod passes through the movable plate and is slidably connected to the movable plate, and the limiting rod is used to limit the lifting and lowering of the movable plate.

[0013] Preferably, the main support frame has a sealing plate integrally formed on one side close to the guide frame, and the sealing plate can limit the bottom of the welding prefabricated part. When the welding prefabricated part is lifted up, the sealing plate can support the bottom of the welding prefabricated part, thereby maintaining the stability of the welding prefabricated part.

[0014] Preferably, another triangular block is fixedly connected to the inner bottom surface of the waste box, and the side wall of the waste box is rotatably connected to a flip cover through a hinge.

[0015] A welding process for a long-span bridge steel truss according to the above-mentioned method comprises the following steps: Preferably, the air pump 2 is driven to allow the heating gas to enter the box for preheating, two diagonal rods and a vertical rod are placed in the box, and the mechanical arm is driven to drive the welding head to perform welding; Preferably, the hydraulic cylinder lifts up the bottom surface of the welding prefabricated part, and the mechanical arm moves on the electric drive track and carries the welding head to weld other surfaces of the welding prefabricated part; Preferably, the air pump is driven to absorb the welding waste gas and send it to the heat exchanger to heat other gases and then send it to the box again to slowly cool the welded prefabricated parts.

[0016] The beneficial effects of the present invention are as follows: the large-span bridge steel truss welding device and process described in the present invention can limit the welding prefabricated parts of the triangular rod structure through a limiting mechanism, and can jack up the welding prefabricated parts through a lifting mechanism. When the welding prefabricated parts are jacked up to a certain arc, the mechanical arm and welding head in the box can conveniently weld different surfaces of the welding prefabricated parts at the welding point, and can weld each weld seam at the welding point, so that the welding is more uniform, thereby facilitating the welding of the welding prefabricated parts.

[0017] The large-span bridge steel truss welding device and process described in the present invention can collect exhaust gas generated by welding through a heat recovery mechanism, and realize heat exchange between gas and gas through a heat exchanger. The hot gas can preheat and slowly cool the box body, thereby avoiding cracks in the weld caused by excessive welding temperature.

[0018] The large-span bridge steel truss welding device and process described in the present invention can adjust the height of the jet hood through an adjusting mechanism to adapt to the height of the welding point after the welding prefabricated parts are lifted up, so that hot air is always sprayed on the welding point, thereby achieving a better slow cooling effect at the welding point.

[0019] The large-span bridge steel truss welding device and process described in the present invention can blow the welding waste slag in the box through the ejected gas through the impurity discharge mechanism, so that it falls into the waste box for discharge, thereby avoiding the accumulation of a large amount of welding waste slag in the box. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The structure of the present invention is schematically shown in FIG. Figure 1 ; Figure 2 The structure of the present invention is schematically shown in FIG. Figure 2 ; Figure 3 is a partial cross-sectional view of the front view of the present invention; Figure 4 The present invention Figure 3 The enlarged view of point A in the middle; Figure 5 is a side partial cross-sectional view of the present invention; Figure 6 It is a schematic diagram of the structure of the limiting mechanism of the present invention; Figure 7 It is a schematic diagram of the limit block structure of the present invention.

[0021] Description of reference numerals: 1. Box body; 2. Welded prefabricated parts; 21. Diagonal rods; 22. Vertical rods; 3. Electric drive rails; 4. Robotic arms; 5. Limiting mechanism; 51. Main support frame; 52. Auxiliary support frame; 53. Cylinder; 54. Limiting block; 6. Lifting mechanism; 61. Hydraulic cylinder; 62. Electromagnetic iron plate; 7. Heat recovery mechanism; 71. Air pump 1; 72. Frame; 73. Heat exchanger; 74. One-way valve; 75. Pressure vessel; 76. Air pump 2; 77. Jet pipe; 78. Jet hood; 8. Adjusting mechanism; 81. Motor; 82. Screw rod; 83. Movable plate; 9. Debris removal mechanism; 91. Triangular block; 92. Waste box; 10. Shell; 11. Guide frame. DETAILED DESCRIPTION

[0022] The subject matter described herein will now be discussed with reference to example embodiments. It should be understood that the discussion of these embodiments is only to enable those skilled in the art to better understand and implement the subject matter described herein, and the functions and arrangements of the elements discussed may be changed without departing from the scope of protection of the contents of this specification. Each example may omit, replace or add various processes or components as needed. In addition, the features described relative to some examples may also be combined in other examples. Example

[0023] like Figures 1 to 7 As shown, a large-span bridge steel truss welding device according to an embodiment of the present invention is shown in FIG. Figure 1 , Figure 3 , Figure 6 , including a box body 1 and a welding prefabricated part 2, the welding prefabricated part 2 is composed of two diagonal rods 21 and a vertical rod 22, the welding prefabricated part 2 is welded in the box body 1, an electric drive track 3 is arranged on the top surface of the box body 1, and a mechanical arm 4 is arranged in the electric drive track 3, a welding head is arranged at the bottom end of the mechanical arm 4, and the welding head is used to weld the welding prefabricated part 2, a limiting mechanism 5 is arranged in the box body 1, the limiting mechanism 5 is used to support the diagonal rods 21 and the vertical rods 22, a lifting mechanism 6 is arranged on the inner bottom surface of the box body 1, the lifting mechanism 6 is used to lift the welding prefabricated part 2, a heat recovery mechanism 7 is arranged in the box body 1, the heat recovery mechanism 7 is used to recover the heat of welding exhaust gas and preheat and slowly cool the welding prefabricated part 2, and a debris removal mechanism 9 is also arranged on the side wall of the box body 1, and the debris removal mechanism 9 is used to discharge welding waste.

[0024] Specifically, the electric drive track 3 is composed of an electric drive unit, a track, a transmission device, etc., which can expand the working range of the robot arm 4, limit the welding prefabricated part 2 of the triangular rod structure through the limiting mechanism 5, and then lift the welding prefabricated part 2 by the lifting mechanism 6. When the welding prefabricated part 2 is lifted to a certain arc, the robot arm 4 and the welding head in the box body 1 can conveniently weld different surfaces of the welding part 2 at the welding point, and can weld each weld at the welding point to make the welding more uniform, which is beneficial to the welding of the welding prefabricated part 2. The heat recovery mechanism 7 can recover the welding exhaust gas and perform heat exchange, preheat and slowly cool the welding prefabricated part 2 in the box body 1, so as to avoid cracks in the welding point caused by excessive welding temperature.

[0025] Please pay attention to Figure 3 , Figure 5 , Figure 6 , Figure 7The limiting mechanism 5 includes a main support frame 51 and a secondary support frame 52 arranged at the bottom of the box body 1. Support frames are fixedly connected between the main support frame 51 and the secondary support frame 52 and the opposite surfaces of the box body 1. The front end surface of the box body 1 is rotatably connected with a flip door through a hinge, and three guide frames 11 are fixedly connected to the flip door. Several guide frames 11 are arranged on the top of the main support frame 51 and the secondary support frame 52. A cylinder 53 is fixedly connected to the inner wall of the box body 1, and the output end of the cylinder 53 is fixedly connected to a limiting block 54. The limiting block 54 is arranged in contact with the top side wall of the welded prefabricated part 2. The main support frame 51 is integrally formed with a sealing plate on one side close to the guide frame 11.

[0026] Specifically, the main support frame 51 and the auxiliary support frame 52 can support the welding prefabricated part 2, the limit block 54 can press against the welding prefabricated part 2, and the sealing plate can limit the bottom of the welding prefabricated part 2. When the welding prefabricated part 2 is lifted up, the sealing plate can support the bottom of the welding prefabricated part 2, thereby maintaining the stability of the welding prefabricated part 2.

[0027] Please pay attention to Figure 3 , Figure 5 The lifting mechanism 6 includes a hydraulic cylinder 61 and an electromagnetic plate 62. The hydraulic cylinder 61 is arranged on the inner bottom surface of the box body 1. A mounting seat is fixedly connected to the inner bottom surface of the box body 1, and the mounting seat is fixedly connected to the hydraulic cylinder 61. The hydraulic cylinder 61 is arranged tilted, and an electromagnetic plate 62 is rotatably arranged on the output end of the hydraulic cylinder 61. The electromagnetic plate 62 is arranged between the main support frame 51 and the auxiliary support frame 52.

[0028] Specifically, the hydraulic cylinder 61 drives the electromagnet plate 62 to lift the welding prefabricated part 2. The electromagnet plate 62 can contact the bottom surfaces of the diagonal rod 21 and the vertical rod 22. The electromagnet plate 62 can adsorb and support the welding prefabricated part 2, which is beneficial to the stability of the welding prefabricated part 2 when it is lifted up. When the welding prefabricated part 2 is lifted up to a certain arc, the mechanical arm 4 and the welding head in the box body 1 can conveniently weld different surfaces of the welding prefabricated part 2 at the welding point, and can weld each weld at the welding point to make the welding more uniform, thereby facilitating the welding of the welding prefabricated part 2.

[0029] Please pay attention to Figure 3 , Figure 4 , Figure 5The heat recovery mechanism 7 includes an air pump 71 fixedly connected to the bottom surface of the box body 1, the input end of the air pump 71 is fixedly connected to the frame body 72, and the filter screen is fixedly connected to the frame body 72, the side wall of the box body 1 is fixedly connected to a support plate, and the top surface of the support plate is fixedly connected to a heat exchanger 73, and the top surface of the box body 1 is fixedly connected to a pressure container 75, the input end of the air pump 71 is fixedly connected to the input end of the heat exchanger 73, the output end of the heat exchanger 73 is fixedly connected to the pressure container 75, and the pipe between the heat exchanger 73 and the pressure container 75 is fixedly connected to the pressure container 75. A one-way valve 74 is installed on the channel, a shell 10 is fixedly connected to the inner top surface of the box body 1, and an air pump 76 is installed in the shell body 10, a pipeline is fixedly connected between the input end of the air pump 76 and the pressure vessel 75, and another one-way valve 74 is installed on the pipeline, an injection pipe 77 is fixedly connected to the output end of the air pump 76, and the injection pipe 77 is threadedly connected to the injection hood 78, and the injection hood 78 faces the welding prefabricated part 2, and an adjusting mechanism 8 is arranged in the box body 1, and the adjusting mechanism 8 is used to adjust the height of the injection hood 78.

[0030] Specifically, the welding waste gas is absorbed by the air pump 71 and transported to the heat exchanger 73. The heat exchanger 73 is an air-to-air heat exchanger that can heat other gases. The waste gas is transported to the filter device through a pipeline for filtration, which is not shown in the figure. The heated gas is transported to the pressure vessel 75 for temporary storage. The pipelines on both sides of the pressure vessel 75 are provided with a one-way valve 74, which can ensure that the flow direction of the heated gas is only from the pressure vessel 75 to the inside of the box body 1, and is pressurized by the air pump 2 76 and sent to the injection pipe 77 and the injection hood 78, which can spray the welding prefabricated part 2. Hot gas is sprayed before welding for preheating. Continuous spraying after welding can slow down the cooling rate, thereby achieving the effect of preheating before welding and slow cooling after welding, and solving the problem of cracks in the weld caused by excessive welding temperature.

[0031] Please pay attention to Figure 3 , Figure 5 The adjustment mechanism 8 includes a motor 81 fixedly connected to the top surface of the box body 1, the output end of the motor 81 penetrates the box body 1 and extends to the inside and is fixedly connected to a screw rod 82, a movable plate 83 is threadedly connected to the screw rod 82, the jet pipe 77 penetrates the movable plate 83 and is threadedly connected to the movable plate 83, the jet pipe 77 is a hose, and a limit rod is fixedly connected to the inner top surface of the box body 1, and the limit rod penetrates the movable plate 83 and is slidably connected to the movable plate 83.

[0032] Specifically, the drive motor 81 drives the screw rod 82 to rotate, thereby driving the movable plate 83 and the jet hood 78 to move up and down to adapt to the height of the welding point after the welding prefabricated part 2 is lifted up, so that the hot air is always sprayed on the welding point, thereby achieving a better slow cooling effect at the welding point.

[0033] Please pay attention to Figure 2 , Figure 5The debris removal mechanism 9 includes a triangular block 91 fixedly connected to the top surface of the box body 1, a waste box 92 is fixedly connected to the side of the box body 1, the hydraulic cylinder 61 is buried in the triangular block 91, another triangular block 91 is fixedly connected to the bottom surface of the waste box 92, and the side wall of the waste box 92 is rotatably connected to a flip cover through a hinge.

[0034] Specifically, the gas ejected from the jet hood 78 blows the welding waste slag on the triangular block 91, causing it to fall into the waste box 92 for discharge, thereby avoiding the accumulation of a large amount of welding waste slag.

[0035] A welding process for a long-span bridge steel truss according to the above-mentioned method comprises the following steps: S1: driving the air pump 2 76 to allow the heating gas to enter the box 1 for preheating, placing two diagonal rods 21 and a vertical rod 22 in the box 1, and driving the robot arm 4 to drive the welding head to weld; S2: The hydraulic cylinder 61 lifts up the bottom surface of the welding prefabricated part 2, and the robot arm 4 moves on the electric drive track 3 and carries the welding head to weld the other surfaces of the welding prefabricated part 2; S3: driving the air pump 71 to absorb the welding waste gas and send it to the heat exchanger 73 to heat other gases and then send it to the box 1 again to slowly cool the welding prefabricated part 2.

[0036] How it works Two diagonal rods 21 and a vertical rod 22 are placed in the three guide frames 11, and they are dropped onto the main support frame 51 and the auxiliary support frame 52. The main support frame 51 and the auxiliary support frame 52 can support the welding prefabricated part 2, and then the cylinder 53 is driven to drive the limit block 54 to press the diagonal rod 21 and the vertical rod 22 tightly, and then the electric drive track 3 and the mechanical arm 4 are operated, and the mechanical arm 4 carries the welding head to weld. After welding the top surface, the hydraulic cylinder 61 is driven to drive the electromagnetic plate 62 to lift the welding prefabricated part 2. The electromagnetic plate 62 can also adsorb and support the welding prefabricated part 2, which is beneficial to the stability of the welding prefabricated part 2 when it is lifted. When the welding prefabricated part 2 is lifted to a certain arc, the mechanical arm 4 and the welding head in the box body 1 can conveniently weld different surfaces of the welding part 2 at the welding point, and can weld each weld at the welding point, so that the welding is more uniform, which is beneficial to the welding of the welding prefabricated part 2; During the welding process, welding waste gas is generated, and the air pump 71 is driven to absorb the welding waste gas through the air pump 71 and transport it to the heat exchanger 73. The heat exchanger 73 is a gas-gas heat exchanger that can heat other gases. The waste gas is transported to the filter device through a pipeline for filtration, which is not shown in the figure. The heated gas is transported to the pressure vessel 75 for temporary storage. The pipelines on both sides of the pressure vessel 75 are provided with a one-way valve 74, which can ensure that the flow direction of the heated gas is only the pressure vessel 75 to the inside of the box 1, and is pressurized by the air pump 2 76 to the injection pipe 77 and the injection hood 78, which can spray the welding prefabricated part 2, thereby achieving the effects of preheating before welding and slow cooling after welding, and solving the problem of cracks in the welding part caused by excessive welding temperature. When the welding prefabricated part 2 is lifted up, the driving motor 81 drives the screw rod 82 to rotate, thereby driving the movable plate 83 and the injection hood 78 to move up and down to adapt to the height of the welding part after the welding prefabricated part 2 is lifted up, so that the hot gas is always sprayed on the welding part, so as to achieve a better slow cooling effect at the welding part; The gas ejected from the jet hood 78 blows the welding waste slag on the triangular block 91, causing it to fall into the waste box 92 for discharge, thereby avoiding the accumulation of too much welding waste slag and facilitating the cleanliness of the interior of the box body 1.

[0037] The welding of the welded prefabricated part 2 adopts the submerged arc welding process. This welding method is suitable for large-section structures and can provide deep penetration welds and high welding efficiency. It is usually used to connect most steel components of the truss. After the welded prefabricated part 2 is welded, it is transported to the site for welding with the upper chord and the lower chord. The welding process adopts gas shielded welding, using gas protection such as argon or carbon dioxide to prevent metal oxidation during welding. This welding process is suitable for large-scale, high-quality welding requirements.

[0038] An example of the present specific implementation mode is described above, but the present embodiment is not limited to the above-mentioned specific implementation mode, which is merely illustrative and not restrictive. A person skilled in the art may make many forms inspired by the present embodiment, all of which are protected by the present embodiment.

Claims

1. A welding device for a long-span bridge steel truss, characterized in that: The invention comprises a box body (1) and a welding prefabricated part (2), wherein the welding prefabricated part (2) is composed of two diagonal rods (21) and a vertical rod (22), the welding prefabricated part (2) is welded in the box body (1), an electric drive track (3) is arranged on the top surface of the box body (1), and a mechanical arm (4) is arranged in the electric drive track (3), a welding head is arranged at the bottom end of the mechanical arm (4), and the welding head is used to weld the welding prefabricated part (2), and a limiting mechanism (5) is arranged in the box body (1). The limiting mechanism (5) is used to support the diagonal rods (21) and the vertical rods (22); the inner bottom surface of the box body (1) is provided with a lifting mechanism (6); the lifting mechanism (6) is used to lift the welding prefabricated part (2); a heat recovery mechanism (7) is provided in the box body (1); the heat recovery mechanism (7) is used to recover the heat of welding waste gas and preheat and slowly cool the welding prefabricated part (2); the side wall of the box body (1) is also provided with a debris discharge mechanism (9); the debris discharge mechanism (9) is used to discharge welding waste.

2. The long-span bridge steel truss welding device according to claim 1 is characterized in that: The limiting mechanism (5) comprises a main support frame (51) and a secondary support frame (52) arranged at the bottom of the box body (1); the main support frame (51) and the secondary support frame (52) are both fixedly connected to the opposite surfaces of the box body (1); the front end surface of the box body (1) is rotatably connected to a flip door through a hinge, and three guide frames (11) are fixedly connected to the flip door; a plurality of the guide frames (11) are arranged on the top of the main support frame (51) and the secondary support frame (52); the inner wall of the box body (1) is fixedly connected to a cylinder (53), and the output end of the cylinder (53) is fixedly connected to a limiting block (54); the limiting block (54) is arranged to fit the top side wall of the welded prefabricated part (2).

3. The long-span bridge steel truss welding device according to claim 2 is characterized in that: The lifting mechanism (6) comprises a hydraulic cylinder (61) and an electromagnet plate (62); the hydraulic cylinder (61) is arranged on the inner bottom surface of the box body (1); a mounting seat is fixedly connected to the inner bottom surface of the box body (1), and the mounting seat is fixedly connected to the hydraulic cylinder (61); the hydraulic cylinder (61) is arranged tilted; an electromagnet plate (62) is rotatably arranged at the output end of the hydraulic cylinder (61); and the electromagnet plate (62) is arranged between the main support frame (51) and the auxiliary support frame (52).

4. The long-span bridge steel truss welding device according to claim 1 is characterized in that: The heat recovery mechanism (7) comprises an air pump (71) fixedly connected to the bottom surface of the box body (1); the input end of the air pump (71) is fixedly connected to the frame body (72), and a filter screen is fixedly connected to the frame body (72); the side wall of the box body (1) is fixedly connected to a support plate, and the top surface of the support plate is fixedly connected to a heat exchanger (73); the top surface of the box body (1) is fixedly connected to a pressure container (75); the input end of the air pump (71) is fixedly connected to the input end of the heat exchanger (73), the output end of the heat exchanger (73) is fixedly connected to the pressure container (75), and a pipeline between the heat exchanger (73) and the pressure container (75) is installed. A one-way valve (74) is provided. The inner top surface of the box body (1) is fixedly connected to a shell (10), and an air pump (76) is installed in the shell body (10). A pipeline is fixedly connected between the input end of the air pump (76) and the pressure container (75), and another one-way valve (74) is installed in the pipeline. An air jet pipe (77) is fixedly connected to the output end of the air pump (76). The air jet pipe (77) is threadedly connected to an air jet cover (78). The air jet cover (78) faces the welding prefabricated part (2). An adjustment mechanism (8) is provided in the box body (1), and the adjustment mechanism (8) is used to adjust the height of the air jet cover (78).

5. The long-span bridge steel truss welding device according to claim 4 is characterized in that: The regulating mechanism (8) comprises a motor (81) fixedly connected to the top surface of the box body (1); an output end of the motor (81) passes through the box body (1) and extends into the interior and is fixedly connected to a screw rod (82); a movable plate (83) is threadedly connected to the screw rod (82); the jet pipe (77) passes through the movable plate (83) and is threadedly connected to the movable plate (83); the jet pipe (77) is a hose.

6. The long-span bridge steel truss welding device according to claim 3 is characterized in that: The debris removal mechanism (9) comprises a triangular block (91) fixedly connected to the top surface of the box body (1); a waste box (92) is fixedly connected to the side of the box body (1); and the hydraulic cylinder (61) is buried in the triangular block (91).

7. The long-span bridge steel truss welding device according to claim 5 is characterized in that: The inner top surface of the box body (1) is fixedly connected to a limiting rod, and the limiting rod passes through the movable plate (83) and is slidably connected to the movable plate (83).

8. The long-span bridge steel truss welding device according to claim 2 is characterized in that: A sealing plate is integrally formed on one side of the main support frame (51) close to the guide frame (11).

9. The long-span bridge steel truss welding device according to claim 6, characterized in that: Another triangular block (91) is fixedly connected to the inner bottom surface of the waste box (92), and a flip cover is rotatably connected to the side wall of the waste box (92) via a hinge.

10. A welding process for a long-span bridge steel truss according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1: driving the second air pump (76) to allow the heating gas to enter the box (1) for preheating, placing two diagonal rods (21) and a vertical rod (22) in the box (1), and driving the mechanical arm (4) to drive the welding head to perform welding; S2: The hydraulic cylinder (61) lifts up the bottom surface of the welding prefabricated part (2), and the mechanical arm (4) moves on the electric drive track (3) and carries the welding head to weld the other surfaces of the welding prefabricated part (2); S3: driving the air pump 1 (71) to absorb the welding waste gas and send it to the heat exchanger (73) to heat other gases and then send them to the box (1) again to slowly cool the welded prefabricated part (2).

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