Mig welding method for single-layer thin-walled aluminum profile dome of railway vehicle

Abstract

This invention discloses a MIG welding method for a single-layer thin-walled aluminum profile dome of a rail vehicle, comprising: preparing a flat top plate assembly: assembling a first flat top profile and two second flat top profiles on both sides on the front support surface of a fixture and welding the seams; assembling the flat top plate assembly with the side beam profiles: inverting the flat top plate assembly and the side beam profiles on the reverse support surface of the dome of the fixture, and applying upward and downward pressure along the Z-axis to make them fit against the fixture; welding the back curved beams: welding the back curved beams one by one onto the assembled flat top plate assembly and the side beam profiles; welding the flat top plate assembly with the side beam profiles: inverting and fixing the prepared flat top plate assembly to the front support surface of the dome of the fixture, and welding the seams between the flat top plate assembly and the side beam profiles; machining the whole assembly; assembling and welding the first and second end plates; adjustment, grinding, and flaw detection. This invention greatly reduces welding deformation, reduces manual adjustment costs, and improves production efficiency.

Description

Technical Field

[0001] This invention belongs to the field of rail vehicle technology and relates to a method for welding a single-layer thin-walled aluminum profile dome for rail vehicles using MIG (Metal Inert Gas Welding). Background Technology

[0002] As a crucial component of rail transit vehicles, the dome structure is currently primarily manufactured in China's subway and high-speed rail systems using a double-layer structural profile combined with friction stir welding. With the rapid development of the domestic market, the requirements for lightweight and environmentally friendly rail transit vehicles are becoming increasingly stringent. Emerging domestic vehicle designs are gradually switching from double-layer to single-layer structural profiles. However, regardless of the structure, the welding method remains the same: friction stir welding is used to assemble the profiles and then perform a one-time welding process.

[0003] With the continuous development of overseas markets, more and more overseas products are entering the domestic market. For a dome product designed overseas, its structure is a single-layer profile, and it is required to be manufactured using MIG welding. Regarding MIG welding and friction stir welding, the former has a large heat input, making it difficult to control the amount of welding deformation, which increases the difficulty of production and manufacturing. Moreover, since the profiles of domes and flat domes are extruded using a single mold to reduce costs, it increases the difficulty of converting the flat dome into an arc shape in the later stages.

[0004] For dome products with this structure and requirements, a complete set of manufacturing processes needs to be developed.

[0005] The existing conventional process flow is as follows: 1) welding of flat top plate, 2) assembly of flat top plate welded parts with side beams, 3) welding of flat top plate welded parts with side beams, 4) welding of back curved beams, 5) overall machining, 6) assembly and welding of accessories, 7) adjustment, grinding and flaw detection.

[0006] According to the existing conventional production sequence, the flat top plate is welded first, then the side beams are welded together, and finally the curved beams are welded. This results in the product's outline not being guaranteed, requiring a lot of manpower for adjustment and repair. Furthermore, the overall curvature of the shape is poor, and deformation still occurs in some areas without curved beam support, which is difficult to adjust and repair. This causes the machining to not meet the processing requirements, resulting in poor overall product quality. Summary of the Invention

[0007] The purpose of this invention is to provide a MIG welding method for single-layer thin-walled aluminum profile domes of rail vehicles. By adopting an effective assembly sequence, it is also applicable to MIG welding of single-layer thin-walled aluminum profile flat tops. By setting a reasonable welding sequence, reasonable welding parameters, and reasonable process flow, the invention solves the difficulties encountered in the trial production process, improves production efficiency, and ensures product quality.

[0008] The technical solution of the present invention is as follows:

[0009] A MIG welding method for a single-layer thin-walled aluminum profile dome of a rail vehicle, the method comprising:

[0010] 1) Preparation of flat-top plate assembly: The first flat-top profile and the second flat-top profiles on both sides are placed on the flat-top front support surface of the tooling and assembled and welded.

[0011] 2) Assembly of flat top plate welded parts and side beam profiles: The flat top plate welded parts and side beam profiles are inverted on the dome-shaped support surface of the tooling, and pressure is applied upward and downward along the Z-axis to bend the flat top plate welded parts and side beam profiles from flat plates into arc plates and fit them into the tooling.

[0012] 3) Back bend beam welding: Weld the back bend beams one by one onto the flat top plate assembly and side beam profiles assembled in step 2);

[0013] 4) Welding of flat top plate assembly to side beam profile: The flat top plate assembly, which includes the back curved beam and side beam profile, obtained in step 3), is inverted and fixed on the front support surface of the dome of the tooling, and the weld between the flat top plate assembly and the side beam profile is welded.

[0014] 5) Overall machining;

[0015] 6) Assemble and weld the first and second end plates;

[0016] 7) Adjustment, polishing, and flaw detection.

[0017] Furthermore, the tooling includes a base, a gantry clamping mechanism, a first-position side-flipping mechanism, a second-position side-flipping mechanism, and a flipping device. Two gantry clamping mechanisms are vertically arranged on the base and move back and forth along the length of the base. The first-position side-flipping mechanism and the second-position side-flipping mechanism are respectively arranged on both sides of the base. Each pair of the first-position side-flipping mechanism and the second-position side-flipping mechanism clamps and rotates a flipping device. The flipping device includes a rotating shaft and flat-top front support surface, flat-top back support surface, dome front support surface, and dome back support surface distributed on the rotating shaft.

[0018] Furthermore, the tooling is provided with multiple pairs of one-position side-flipping mechanisms and two-position side-flipping mechanisms; correspondingly, the tooling is provided with multiple flipping devices.

[0019] Furthermore, in step 1): during the profile assembly process, the first flat-top profile and the second flat-top profile at one end are aligned, and the subsequent assembly uses this end face as the reference point in the X direction.

[0020] Fix both ends of the first and second flat-top profiles in the width direction to prevent deformation after welding; place pads on the back of the weld joint of the first and second flat-top profiles.

[0021] Intermittent welding: Welding length is 2300-2400mm and the welding is staggered;

[0022] Use a track-mounted gantry automatic welding machine to replace manual welding.

[0023] Furthermore, in step 2): the flat top plate assembly and the side beam profile are bent from flat plates into arc plates and the gap between them and the tooling contact surface is ≤0.5mm.

[0024] Further, in step 3): the back curved beams are placed on the flat top plate assembly and side beam profiles assembled in step 2), and welded one by one from the center to both sides until all the back curved beams are welded.

[0025] Furthermore, the weld in step 4) is an intermittent weld: the weld length is 2300-2400mm and the welds are staggered.

[0026] The beneficial effects of this invention are:

[0027] The production process of this invention is as follows: 1) welding of the flat top plate, 2) assembly of the flat top plate welded parts with the side beams, 3) welding of the back curved beams, 4) welding of the flat top plate welded parts with the side beams, 5) overall machining, 6) assembly and welding of accessories, and 7) adjustment, grinding and flaw detection.

[0028] This invention improves the amount of post-weld deformation by adjusting the welding sequence and process, thus ensuring the final contour requirements of the dome product. This invention refines the product manufacturing process, forming a production method.

[0029] Operating according to the method of this invention greatly reduces welding deformation, reduces manual adjustment costs, and improves production efficiency. At the same time, the method of this invention is also applicable to MIG welding of flat tops of single-layer thin-walled aluminum profiles of the same type, and has specific reference value for the production process of other products. Attached Figure Description

[0030] Figure 1 This is a frontal view of the dome.

[0031] Figure 2 This is a schematic diagram of the reverse side of the dome;

[0032] Figure 3 This is a cross-sectional view of the end face of the flat top plate assembly in the width direction, as shown in step 1).

[0033] Figure 4 This is a diagram showing the welding sequence of the flat top plate assembly in step 1).

[0034] Figure 5 This is a schematic diagram of the flat top plate assembly welded in step 1).

[0035] Figure 6 This is a schematic diagram of the assembly of the flat top plate weldment and the side beam in step 2).

[0036] Figure 7 This is a schematic diagram of the welding of the back bending beam in step 3).

[0037] Figure 8 This is a schematic diagram of the welding of the flat top plate assembly and the side beam assembly in step 4).

[0038] Figure 9 This is an overall structural diagram of the welding fixture;

[0039] Figure 10 This is a schematic diagram of the base;

[0040] Figure 11 This is a schematic diagram of the gantry clamping mechanism;

[0041] Figure 12 A schematic diagram of a side-tilting mechanism;

[0042] Figure 13 This is a schematic diagram of a two-position side-flipping mechanism;

[0043] Figure 14 This is a schematic diagram of the flipping device;

[0044] Figure 15 This is an enlarged view of the longitudinal beam of the base;

[0045] Figure 16 Enlarged view of the cylinder and pressure block of the gantry clamping mechanism;

[0046] Figure 17 An enlarged view of a side-flipping mechanism;

[0047] Figure 18 This is an enlarged view of the two-position side-flipping mechanism;

[0048] Figure 19 This is a schematic diagram of the cylinder clamping blocks on surfaces A and C of the flipping device.

[0049] Figure 20 for Figure 19 Enlarged view of the cylinder clamping block;

[0050] The diagram is marked as follows:

[0051] E. First flat plate profile; F. Second flat plate profile; G. Side beam profile; I. Back curved beam; J. First end plate; K. Second end plate.

[0052] 1. Base; 2. Gantry clamping mechanism; 3. First-position side-tilting mechanism; 4. Second-position side-tilting mechanism; 5. Tilting device; 21. Cylinder; 22. Pressure block; 41. Limit bolt; 51. Cylinder clamping block; A. Flat top front support surface; B. Flat top back support surface; C. Dome front support surface; D. Dome back support surface. Detailed Implementation

[0053] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0054] like Figure 1 and Figure 2 As shown, in this embodiment, the dome to be welded is a single-layer thin-walled aluminum profile dome, which includes a first flat top profile E, a second flat top profile F, a side beam profile G, a back curved beam I, a first end plate J, a second end plate K, and other accessories.

[0055] For ease of description, the length direction of the dome is the X-axis, the width direction is the Y-axis, and the height direction is the Z-axis. The dimensions of this dome are (7000mm*2800mm*450mm).

[0056] Example 1

[0057] The dome in this embodiment requires the use of the following single-layer thin-walled aluminum profile roof welding fixture, such as... Figure 9 As shown, the single-layer thin-walled aluminum profile roof welding fixture for rail vehicles is a fixture suitable for welding flat and dome roofs. It includes a base 1, a gantry clamping mechanism 2, a first-position side-tilting mechanism 3, a second-position side-tilting mechanism 4, and a tilting device 5. Two gantry clamping mechanisms 2 are vertically arranged at both ends of the base 1. Multiple first-position side-tilting mechanisms 3 are arranged on one side of the base 1, and multiple second-position side-tilting mechanisms 4 are arranged on the other side of the base 1. Each pair of first-position side-tilting mechanisms 3 and second-position side-tilting mechanisms 4 are fixed together and rotated by a tilting device 5.

[0058] Among them, such as Figure 10 and Figure 15 As shown, the base 1 includes two parallel longitudinal beams. The main structure of the longitudinal beams is made of square tubes and plates welded together. The upper and lower surfaces of the square tubes are machined to achieve flatness and parallelism. During installation, the base is fixed to the ground by the lower expansion bolts. Then, with the help of a level and adjusting the height of the bolts, the longitudinal beams on both sides are adjusted to the same horizontal height, which provides horizontal support for the overall fixture. The plate is set on the side of the square tubes and provides a moving track for the gantry pressing mechanism 2.

[0059] like Figure 11 and Figure 16As shown, the gantry clamping mechanism 2 includes two side support columns, a crossbeam, and cylinders 21 and pressure blocks 22 mounted on the crossbeam. The bottom of the two side support columns is mounted on the plate on the side of the base 1 and can move back and forth. The crossbeam is mounted across the two side support columns, and three sets of cylinders 21 are prefabricated on the upper part of the crossbeam. The pressure blocks 22 are connected below the cylinders 21. After the air source is turned on, the cylinders 21 move downward, causing the pressure blocks 22 below the cylinders 21 to clamp the components.

[0060] like Figure 12 and Figure 17 As shown, the side-tilting mechanism 3 includes a manually rotating wheel, a column, and a fixed base. The bottom of the column is fixed to a longitudinal beam of the base, and the top of the column is equipped with a fixed base. The fixed base has a through-hole on its side, into which one end of the rotating shaft of the tilting device 5 is inserted. The rotating wheel drives the rotating shaft of the tilting device 5 to rotate. The rotation drive part in the side-tilting mechanism 3 is a worm gear reducer (NRV090), which is a conventional general-purpose component.

[0061] The lower part of the side-flipping mechanism 3 is bolted to a longitudinal beam of the base 1 (specifically, to the square tube of the longitudinal beam). By manually rotating the rotating wheel, one end of the flipping device 5 is rotated, thereby rotating the entire flipping device 5 360°, thus achieving the effect of switching between the four different surfaces of the flipping device 5: flat top front support surface A, flat top back support surface B, dome front support surface C, and dome back support surface D.

[0062] like Figure 13 and Figure 18 As shown, the two-position side-tilting mechanism 4 includes a column, a fixed base, and a limiting bolt 41. The lower part of the column is bolted to another longitudinal beam of the base 1 (specifically, to the square tube of the other longitudinal beam). A fixed base is fixed on the column, and a through limiting hole is provided on the side of the fixed base for inserting the rotating shaft of the tilting device. A limiting bolt 41 is vertically downwardly installed on the fixed base, extending into the limiting hole. Its function is to fix the other end of the tilting mechanism 5, and when the tilting device 5 is tilted to a fixed angle, the limiting bolt 41 can be used to limit it, preventing the tilting device 5 from rotating and shaking.

[0063] like Figure 14 and Figure 19As shown, the flipping device 5 includes a rotating shaft, a flat-top front support surface A, a flat-top back support surface B, a dome front support surface C, and a dome back support surface D. Four surfaces—flat-top front support surface A, flat-top back support surface B, dome front support surface C, and dome back support surface D—are distributed at 90° intervals along the rotating shaft, respectively supporting the flat-top front, flat-top back, dome front, and dome back surfaces. A cylinder clamping block 51 is installed at the weld joint of the flat-top front support surface A and the dome front support surface C to clamp the profile at the welding position. This fixture has a total of 6 sets of flipping devices 5, which, through their spaced distribution, construct the support surfaces for the product and facilitate welding operations.

[0064] Example 2

[0065] The MIG welding method for the single-layer thin-walled aluminum profile dome of the rail vehicle in this embodiment includes the following steps:

[0066] 1) Flat top plate welding: After grinding and cleaning one first flat top profile E and two second flat top profiles F (only the welding area), place them on the tooling or platform (the tooling described in Example 1) for assembly. The gap should be controlled at 2mm (to avoid the welding quality being compromised if the gap is too small, and the welding shrinkage being too large if the gap is too large, which would increase the amount of deformation). 2mm shims can be used to control the assembly gap and perform tack welding. After all adjustments are made, continue welding in the length direction.

[0067] At this point, the flat top front support surface A of the tooling is used for support.

[0068] Improvement areas:

[0069] i) During the profile assembly process, the first flat-top profile E and the second flat-top profile F at one end are aligned. Subsequent material assembly uses this end face as the X-direction reference point, which facilitates subsequent operations.

[0070] ii) In addition to the conventional process of fixing both ends in the width direction to prevent post-weld deformation and upward warping towards the weld side, to improve the sinking of the weld joint after welding, a 4-5mm pad is applied to the back of the weld joint, so that it arches upward before welding (e.g., Figure 3 (As shown).

[0071] iii) Continuous welding from one end to the other along the X-axis length leads to unrelieved heat concentration, ultimately causing stress concentration at the end and resulting in a bulge, affecting subsequent product use. Therefore, the welding sequence should be adjusted, changing continuous welding to intermittent welding, and the welding length should be changed to between 2300 and 2400 mm with staggered welding (e.g., Figure 4 (As shown).

[0072] (iiiii) Because the weld length is more than two meters after being segmented, manual MIG welding is labor-intensive for long periods of time, and the weld quality cannot be guaranteed. Therefore, we improved the process by using a track-type gantry automatic welding machine to replace manual welding, thereby improving welding efficiency and weld quality.

[0073] Through step 1) above, we obtain the following... Figure 5 The flat-top plate assembly shown.

[0074] 2) Assembly of flat roof plate welded components and side beam profile G: according to Figure 6 As shown, the flat top plate assembly obtained in step 1) and the side beam profile G are inverted on the fixture, and a gantry-type pressure block is used to apply pressure upward and downward along the Z-axis, so that the flat top plate assembly is bent from a flat plate into an arc plate and the gap between the flat top plate assembly and the surface of the fixture is ≤0.5mm.

[0075] Improvement areas:

[0076] i) The process of changing from forward pressing to reverse pressing is affected by the fact that during the forward pressing process, the flat top plate assembly is bent into an arc plate, which can easily cause sharp bends and result in a profile deviation of more than 6mm, which does not meet the final product requirements.

[0077] At this time, the tooling uses the dome-shaped reverse support surface D to support the flat top plate assembly.

[0078] 3) Back Beam I Welding: After the flat top plate assembly from step 2) is assembled with the side beam profile G and tightly adheres to the tooling's contour surface, as shown... Figure 7 As shown, place the back curved beam I in the designated position and weld it one by one from the center to both sides according to the welding process requirements. After all the back curved beams I are welded, release the clamping device.

[0079] Improvement areas:

[0080] i) Change the welding sequence of the back curved beam I, and control the profile of the entire dome after forming by the curvature of the back curved beam I. This solves the forming difficulty and ensures the profile requirement. After the back curved beam I is assembled and welded, the profile is ≤1mm.

[0081] At this time, the tooling uses the dome-shaped reverse support surface D to support the flat top plate assembly.

[0082] 4) Welding of the flat top plate assembly to the side beam profile G: After step 3), turn the product obtained in step 3) over and fix it on the tooling, such as... Figure 8 As shown, the side beam profile G is then fixed to the tooling using a clamp.

[0083] refer to Figure 4 The welding sequence shown is used to intermittently and alternately weld the welds between the flat top plate assembly and the side beam profile G.

[0084] Improvement areas:

[0085] i) The weld seam of the flat top plate assembly and the side beam profile G is placed after the curved beam welding. At this time, the overall profile is not easily deformed due to the support of the curved beam, and the weld seam will not sink due to the support of the curved beam I on the back. After welding, the profile in the width direction can be kept within 2mm. If local deformation occurs, only slight adjustments are needed to meet the processing requirements.

[0086] At this time, the tooling uses the dome front support surface C to support the flat top plate assembly and the side beam profile G.

[0087] 5) Overall machining: Machining the dome obtained in step 4) according to the dimensions required by the drawing. The accuracy of the machining opening size depends on the product profile. The smaller the profile value, the closer the product machining is to the theoretical size. The larger the profile value, the greater the deviation of the product machining size from the theoretical size.

[0088] Improvement areas:

[0089] i) To reduce the amount of welding work after machining, the internal stiffening plates of the side beam cavity have been welded in advance. When machining the original component length, a welding shrinkage allowance of 2mm should be added compared to the theoretical size to prevent the final product length from exceeding the tolerance (-2, +1).

[0090] 6) Component Assembly and Welding: After the product processing is completed, prioritize the assembly and welding of end plate J (position 1) and end plate K (position 2). After welding, the side beams on both sides and the front and rear end plates form a whole. Subsequent component installation and welding will have a significant impact on the overall dimensions.

[0091] Improvement areas:

[0092] i) Because the dome-shaped product has an arc-shaped structure in the width direction, the accuracy of the measured dimensions cannot be guaranteed. Therefore, it is important to control the product's outline before processing to ensure the accuracy of the hole dimensions, which will facilitate the subsequent installation of accessories.

[0093] 7) Adjustment, grinding, and flaw detection: After the product welding is completed, the dimensions of the dome components and the appearance of the welds are inspected through self-inspection, mutual inspection, and special inspection. If they meet the requirements, penetrant testing is carried out again to confirm the quality of the welds.

[0094] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the scope of protection of the present invention in any way, and all technical solutions obtained by equivalent substitution or other means fall within the scope of protection of the present invention.

Claims

1. A method of MIG welding a single-skin thin-walled aluminium profiled dome of a railway vehicle, characterised in that, The method includes: 1) Preparation of flat-top plate assembly: The first flat-top profile and the second flat-top profiles on both sides are placed on the flat-top front support surface of the fixture and assembled and welded; the fixture includes a base, a gantry clamping mechanism, a first-position side flipping mechanism, a second-position side flipping mechanism and a flipping device. Two gantry clamping mechanisms are vertically arranged on the base and the gantry clamping mechanisms move back and forth along the length of the base. The first-position side flipping mechanism and the second-position side flipping mechanism are respectively arranged on both sides of the base. Each pair of the first-position side flipping mechanism and the second-position side flipping mechanism clamps and rotates a flipping device. The flipping device includes a rotating shaft and flat-top front support surface, flat-top back support surface, dome front support surface and dome back support surface distributed on the rotating shaft; 2) Assembly of flat top plate welded parts and side beam profiles: The flat top plate welded parts and side beam profiles are inverted on the dome-shaped support surface of the tooling, and pressure is applied upward or downward in the Z-axis to bend the flat top plate welded parts and side beam profiles from flat plates into arc plates and fit them into the tooling. 3) Back bend beam welding: Weld the back bend beams one by one onto the flat top plate assembly and side beam profiles assembled in step 2); 4) Welding of flat top plate assembly to side beam profile: The flat top plate assembly, including the back curved beam and side beam profile, obtained in step 3) is inverted and fixed on the front support surface of the dome of the tooling, and the weld between the flat top plate assembly and the side beam profile is welded. 5) Overall machining; 6) Assemble and weld the first and second end plates; 7) Adjustment, polishing, and flaw detection.

2. The MIG welding method of a single-skin thin-walled aluminum profile dome of a rail vehicle according to claim 1, characterized in that, The fixture is provided with multiple pairs of one-position side-flipping mechanisms and two-position side-flipping mechanisms; correspondingly, the fixture is provided with multiple flipping devices.

3. The MIG welding method for a single-layer thin-walled aluminum profile dome for rail vehicles as described in any one of claims 1-2, characterized in that, Step 1): During the profile assembly process, the first flat-top profile and the second flat-top profile at one end are aligned, and the subsequent assembly uses this end face as the reference point in the X direction. Fix both ends of the first and second flat-top profiles in the width direction to prevent deformation after welding; place pads on the back of the weld joint of the first and second flat-top profiles. Intermittent welding: Welding length is 2300-2400mm and the welding is staggered; Use a track-mounted gantry automatic welding machine to replace manual welding.

4. The MIG welding method for a single-layer thin-walled aluminum profile dome for rail vehicles as described in any one of claims 1-2, characterized in that, Step 2): The flat top plate assembly and the side beam profile are bent from flat plates into arc plates, and the gap between them and the tooling mating surface is ≤0.5mm.

5. The MIG welding method of a monolithic thin-walled aluminum profile dome of a rail vehicle according to any one of claims 1 to 2, characterized in that, Step 3): Place the back curved beams on the flat top plate assembly and side beam profiles assembled in Step 2), and weld them one by one from the center to both sides until all the back curved beams are welded.

6. A method of MIG welding a monolithic thin-walled aluminum profiled dome of a rail vehicle according to any one of claims 1-2, characterized in that, The welding in step 4) is intermittent welding: the welding length is 2300-2400mm and the welding is staggered.

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