Welding method for coated steel plate with thickness difference

Abstract

The invention relates to the technical field of steel plate welding, and provides a welding method for coated steel plates with thickness difference, which comprises the following steps: S1, fixing two coated steel plates on a welding table; s2, enabling the upper surfaces of the two parts to be flush with each other; s3, the laser welding head is moved to the position above the middle of the welding seam gap; and S4, the laser welding equipment is started. The upper surfaces of the two coated steel plates are aligned, the laser welding head is moved to the position above the middle of the welding seam gap, the laser welding head conducts welding in the vertical direction, the two coated steel plates can be evenly heated, and in the blowing process of protective gas, the protective gas can be evenly sprayed to the two coated steel plates. According to the device, molten plating layers of two to-be-welded plates on the same plane can be uniformly blown open towards the two sides of the surface of a steel plate along the center line of a welding seam, so that the amount of the plating layers flowing into a welding seam molten pool is greatly reduced, the plating layers do not need to be stripped, the welding technological process is simplified on the premise that the structural strength of the welding seam is improved, and the production cost is reduced. And the welding processing cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of steel plate welding, and in particular to a welding method for coated steel plates with different thicknesses. Background Art

[0002] With the rapid increase in the number of cars, the accident rate has also increased, and safety performance has become the focus of people's attention. In order to produce safe, energy-saving, weight-saving and cost-effective automobile products to cater to the market, automobile companies require soft and hard partitions on the same finished parts in the application of body structure parts. Therefore, it is necessary to use welding technology to weld steel plates of different materials, thicknesses and strengths.

[0003] Welded parts can be welded not only from materials with the same strength and thickness, but also from a combination of materials with different strengths and thicknesses. When welding steel plates of different thicknesses, the prior art usually uses welded plates and their manufacturing methods disclosed in the invention patent with announcement number CN104023899B, as well as hot stamping parts using welded plates, to align the lower surfaces of the two steel plates, tilt the laser beam, and focus the laser on the thick plate.

[0004] However, most of the steel plates used in vehicles are aluminum-silicon coated stamped steel. When the above method is used to laser weld aluminum-silicon coated hot stamped steels of different strength levels and thicknesses, especially when the thickness difference between the two steel plates is greater than 0.6 mm, there is not only the problem of uneven laser energy distribution, but also during the shielding gas blowing process, the coating that melts first on the thick plate is completely blown into the weld gap that is not in the same plane, making the composition of the material in the weld molten pool unstable, affecting the connection strength between the weld and the two steel plates, and affecting the welding quality of the steel plates. Summary of the invention

[0005] In view of this, the present invention proposes a welding method for coated steel plates with different thicknesses, which can improve the heating uniformity of the two coated steel plates, and during the blowing process, the protective gas can evenly blow the molten coating to both sides of the steel plate surfaces along the center line of the weld for the two plates to be welded on the same plane, thereby reducing the amount of molten coating entering the weld and reducing impurities in the weld, thereby improving the structural strength of the weld.

[0006] The technical solution of the present invention is implemented as follows: The present invention provides a welding method for coated steel plates with different thicknesses, comprising the following steps:

[0007] S1, fixing two coated steel plates of different thicknesses on a welding table so that their welding positions are parallel and spaced apart to form a weld gap;

[0008] S2, adjusting the heights of the two coated steel plates so that their upper surfaces are flush with each other;

[0009] S3, during laser welding, fill the weld with welding wire, move the laser welding head to the top of the middle of the weld gap, and make the laser welding head perpendicular to the two coated steel plates;

[0010] S4, starting the laser welding equipment, allowing the laser welding head to translate along the length direction of the weld gap, and blowing a protective gas into the weld gap to generate a weld in the weld gap.

[0011] On the basis of the above technical solution, preferably, in step S1, the welding table includes a table, two lifting platforms and two electromagnets, wherein:

[0012] There are two mounting holes extending through the table;

[0013] The two electromagnets are respectively fixedly arranged on the output ends of the two lifting platforms, and are respectively slidably arranged in the two mounting holes.

[0014] More preferably, the welding table further comprises a positioning mechanism, which comprises a slide rail, a slide seat, a guide rail, a bidirectional screw rod and two scale frames, wherein:

[0015] The slide rail is fixedly arranged on the table;

[0016] The slide seat is slidably arranged on the slide rail, two slide seats and two slide rails are provided, and the two slide seats correspond to the two slide rails one by one;

[0017] The guide rail is fixedly arranged between the two slide seats;

[0018] The bidirectional screw rod is rotatably arranged between the two slide seats;

[0019] The scale frame is connected to the bidirectional screw rod through threaded engagement and is slidably arranged on the guide rail, and the two scale frames are symmetrically arranged about the center line of the table.

[0020] More preferably, the positioning mechanism further comprises two metal springs, and the metal springs are respectively fixedly arranged at two ends of the slide seat;

[0021] The slide rail is provided with a plurality of tooth grooves, and the metal spring piece is engaged with one of the tooth grooves.

[0022] On the basis of the above technical solution, preferably, in step S3, the specification of the welding wire is selected according to the width of the weld gap and the structural strength of the two coated steel plates.

[0023] More preferably, the structural strength of the welding wire is greater than or equal to the structural strength of the two coated steel plates.

[0024] On the basis of the above technical solution, preferably, the coated steel plate includes a base steel plate and an aluminum-silicon coating, and the aluminum-silicon coating is coated on the surface of the base steel plate.

[0025] On the basis of the above technical solution, preferably, in step S4, the protective gas includes carbon dioxide and nitrogen.

[0026] More preferably, the lifting platform includes a bottom frame, a top frame, four connecting rods, two sleeves and a bidirectional screw, wherein:

[0027] The top frame is parallel to the bottom frame and is spaced apart;

[0028] One end of two of the connecting rods is rotatably arranged on the bottom frame, and one end of the other two connecting rods is rotatably arranged on the top frame;

[0029] The sleeve is rotatably arranged between the two connecting rods, and the two connecting rods connected to the same sleeve are respectively connected to the bottom frame and the top frame;

[0030] The bidirectional screw is connected between the two sleeves through threaded fitting.

[0031] More preferably, one end of the connecting rod away from the sleeve is in a gear-like structure and meshes with two connecting rods connected to the same top frame or the same bottom frame.

[0032] The welding method for coated steel plates with different thicknesses of the present invention has the following beneficial effects compared with the prior art:

[0033] (1) By aligning the upper surfaces of the two coated steel plates and moving the laser welding head to the top of the middle of the weld gap, the laser welding head is welded in the vertical direction. Not only can the two coated steel plates be heated evenly, but also the protective gas can evenly blow the molten coating to both sides of the steel plate surface along the center line of the weld for the two plates to be welded on the same plane during the blowing process, thereby greatly reducing the amount of coating flowing into the weld pool. There is no need to peel off the coating, thereby simplifying the welding process and reducing the welding processing cost while improving the structural strength of the weld.

[0034] (2) By selecting the specifications of the welding wire based on the width of the weld gap and the structural strength of the two coated steel plates, the structural strength of the weld can be further improved. By blowing a shielding gas during welding, not only can the coating be prevented from flowing into the weld pool, but also the oxidation reaction between the substances in the weld pool and the external environment can be prevented, thereby improving the weld quality.

[0035] (3) By setting up a table, a lifting platform and an electromagnet, the coated steel plate can be easily lifted and lowered. By setting up a positioning mechanism, the two coated steel plates can be easily positioned and fixed, thereby improving the convenience of steel plate welding operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1 The metallographic image of the weld in the welding method for coated steel plates with different thicknesses according to the present invention;

[0038] Figure 2 A metallographic image of a comparative weld in a welding method for coated steel plates with different thicknesses according to the present invention;

[0039] Figure 3 This is a photo of the tensile test result of the workpiece in the embodiment of the welding method for coated steel plates with different thicknesses of the present invention;

[0040] Figure 4 This is a photo of the tensile test result of a comparative example workpiece in the welding method for coated steel plates with different thicknesses of the present invention;

[0041] Figure 5 A bar graph showing the test results of Test Example 3 for a coated steel sheet with thickness differences according to the present invention;

[0042] Figure 6 A cross-sectional view of a coated steel plate in a welding method for coated steel plates with different thicknesses according to the present invention;

[0043] Figure 7 A three-dimensional diagram of a welding station in a welding method for coated steel plates with different thicknesses according to the present invention;

[0044] Figure 8 A cross-sectional view of a lifting platform in a welding method for coated steel plates with different thicknesses according to the present invention;

[0045] Fig. 9 A three-dimensional diagram of a lifting platform in a welding method for coated steel plates with different thicknesses according to the present invention;

[0046] Fig.10 A three-dimensional view of a connecting rod in a welding method for coated steel plates with different thicknesses according to the present invention;

[0047] Fig.11 A three-dimensional diagram of a positioning mechanism in a welding method for coated steel plates with different thicknesses according to the present invention;

[0048] Fig.12 It is a three-dimensional diagram of the metal spring piece in the welding method for coated steel plates with different thicknesses of the present invention;

[0049] Fig.13 It is a stereoscopic diagram of a welding table in the prior art.

[0050] Among them: 1. Table; 101. Mounting hole; 2. Lifting platform; 21. Base frame; 22. Top frame; 23. Connecting rod; 24. Sleeve; 25. Bidirectional screw; 3. Electromagnet; 4. Positioning mechanism; 41. Slide rail; 42. Slide seat; 43. Guide rail; 44. Bidirectional screw; 45. Scale frame; 46. Metal shrapnel; 401. Tooth groove; 100. Base steel plate; 200. Aluminum silicon coating. DETAILED DESCRIPTION

[0051] The following will be combined with the specific implementation of the present invention to clearly and completely describe the technical solution in the present invention. Obviously, the described implementation is only a part of the implementation of the present invention, not all of the implementation. Based on the implementation of the present invention, all other implementations obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] In order to make vehicles meet more stringent collision requirements and achieve maximum lightweight, coated steel sheets are increasingly used in vehicles. Among them, aluminum silicon pre-coated hot stamped steel is the most widely used, such as Figure 6 As shown, the coated steel plate includes a base steel plate 100 and an aluminum-silicon coating 200, that is, the base steel plate 100 is used as the main body, and the aluminum-silicon coating 200 is coated on the surface of the base steel plate 100 by hot-dip coating, thereby improving the overall performance of the coated steel plate; of course, the coating in the coated steel plate includes but is not limited to the aluminum-silicon coating, and the coating parameters are 30-200g per square meter.

[0053] During the vehicle processing process, it is necessary to use welding technology to weld the coated steel plates in different areas. The welded parts can not only be welded by materials with the same strength and thickness, but also by a combination of materials with different strengths and thicknesses.

[0054] In the prior art, when laser welding is performed on coated steel plates with a small thickness difference and a small tensile strength requirement for welded parts, the process is relatively mature. However, when laser welding is performed on coated steel plates with a thickness difference greater than 0.6 mm or a tensile strength requirement greater than 1500 MPa, metallographic testing has found that the composition of the weld molten pool is extremely unstable and cannot be fully martensitic after hot forming. The metallographic structure shows the presence of ferrite banding structure. During the tensile test, the fracture position of the welded part is at the weld, and the tensile strength and hardness indicators cannot meet the standards. The stability of various indicators is also extremely poor. For this reason, the present invention proposes a welding method that can be adapted to coated steel plates with a large thickness difference or a high tensile strength requirement.

[0055] like Figure 1-Figure 11 As shown, the welding method for coated steel plates with different thicknesses of the present invention includes the following steps: S1, fixing two coated steel plates with different thicknesses on a welding table, and adjusting the fixing positions of the two coated steel plates so that the welding positions of the two coated steel plates are parallel and spaced apart to form a weld gap with uniform width; S2, adjusting the heights of the two coated steel plates so that the upper surfaces of the two coated steel plates are flush with each other, and the upper surfaces of the two coated steel plates are parallel to the horizontal plane; S3, filling welding wire into the weld during laser welding, moving the laser welding head to above the middle position in the width direction of the weld gap, and making the laser welding head perpendicular to the two coated steel plates; S4, starting the laser welding equipment, making the laser welding head translate along the length direction of the weld gap, and blowing protective gas into the weld gap to generate a weld in the weld gap.

[0056] Since the upper surfaces of the two coated steel plates are flush, the laser welding head operates in a vertical state, and the focus of the laser beam emitted by the laser welding head is located in the middle of the weld gap, it can not only improve the consistency of the welding wire entering the weld gap after melting, forming a stable and basically symmetrical weld, but also make the two coated steel plates heated evenly, making the connection between the weld and the two coated steel plates more balanced, thereby ensuring the structural strength of the weld.

[0057] At the same time, during the welding process, the welding wire is evenly filled in the weld gap. During the blowing process, the shielding gas can evenly blow the molten coating to both sides of the steel plate surface along the weld center line for the two plates to be welded on the same plane, thereby greatly reducing the amount of the molten coating flowing into the weld gap. This not only further enhances the welding quality, but also eliminates the need to strip the coating of the two coated steel plates before the welding process, effectively simplifying the welding process of the coated steel plates and reducing the welding cost of the coated steel plates.

[0058] When welding different types of coated steel plates, different specifications of welding wires are required. Therefore, before welding, the specifications of the welding wire should be selected according to the width of the weld gap and the structural strength of the two coated steel plates. The specification of the welding wire is mainly distinguished by the structural strength. The structural strength of the welding wire should be greater than or equal to the structural strength of the two coated steel plates and the tensile strength required by the welded parts. For example, if the structural strength of the two coated steel plates and the tensile strength required by the welded parts are at the 1500MPa level, a welding wire with a structural strength greater than 1500MPa should be selected.

[0059] In order to prevent the substances in the weld pool from oxidizing with the outside air, a shielding gas is blown into the weld gap during the laser welding head welding. The shielding gas can be a mixture of nitrogen and carbon dioxide. Since the laser welding head is in a vertical state during the welding process and is located in the middle of the weld gap, there is no need to adjust the gas supply direction according to the thickness of the plate, and the gas can be blown evenly to the two coated steel plates, which helps to improve the stability of the welding quality. Of course, blowing shielding gas also helps to prevent the flow of the melted coating into the weld gap.

[0060] Example

[0061] Make the upper surfaces of the two coated steel plates flush with each other, vertically set the laser welding head above the middle position of the weld gap, and make the focus of the laser beam in the middle position of the weld gap, weld the two coated steel plates to form a welded component A.

[0062] Among them, the welding gap between the two coated steel plates is 0.3mm, the length of the two coated steel plates is 360mm, the width is 150mm, the thickness is 1.4mm and 2.5mm respectively, the structural strength of the two coated steel plates is 1500MPa, the structural strength of the welding wire is greater than 1500MPa, and the coating of the two coated steel plates is 150g per square meter.

[0063] Comparative Example

[0064] The lower surfaces of the two coated steel plates are aligned, the laser welding head is tilted and set above the weld gap, and the focus of the laser beam is placed on the thick plate. The two coated steel plates are welded to form a welded component B.

[0065] Among them, the welding gap between the two coated steel plates is 0.3mm, the length of the two coated steel plates is 360mm, the width is 150mm, the thickness is 1.4mm and 2.5mm respectively, the structural strength of the two coated steel plates is 1500MPa, the structural strength of the welding wire is greater than 1500MPa, and the coating of the two coated steel plates is 150g per square meter.

[0066] Test Example 1

[0067] The metallographic samples of welding parts A and B are prepared, and the metallographic images are collected using a metallographic microscope. The metallographic image of welding part A is as follows: Figure 1 As shown, the metallographic image of welded component B is as follows Figure 2 shown.

[0068] Test Example 2

[0069] Three welding parts A and three welding parts B were prepared respectively, and tensile tests were performed on them one by one using a tensile testing machine to observe the fracture positions of the welding parts. The tensile results of welding parts A and B were respectively as follows: Figure 3 and Figure 4 shown.

[0070] Test Example 3

[0071] 15 welded parts A and 15 welded parts B were prepared respectively, and the hardness of the welds was tested using a hardness tester. The bar graph of the test results is shown in the figure below: Figure 5 shown.

[0072] The welded component B in the comparative example is welded by using the technical solution in the prior art, such as Figure 2 As shown in the figure, the melted coating on the two coated steel plates flows into the weld gap, resulting in uneven internal structure of the weld. At the same time, due to the uneven heating of the two coated steel plates, the melted cuts at the welding edges of the two are uneven, resulting in an irregular weld shape. Figure 4 As shown, the tensile fractures of welded component B are all located at the weld, indicating that the welding method used for welded component B will cause the risk of weld cracking.

[0073] The welding component A in the embodiment is welded by adopting the technical solution of the present invention. Figure 1 As shown, the internal structure of the weld is uniform; Figure 3 As shown in Figure 1, the tensile fracture of welded component A is located at the parent material position; Figure 5 As shown, the hardness test results of the welded component A all meet the European standard BS EN 10359: 2023. In summary, the weld formed by the technical solution of the present invention has the advantages of high structural strength and hardness and uniform internal structure, and is more suitable for laser welding of coated steel plates with large plate thickness differences.

[0074] The present invention solves the welding quality problem that occurs during the welding process of two coated steel plates with different thicknesses in principle and practice. This method can greatly improve the product qualification rate in the laser welding production of single and double automobile door rings, and has broader practical significance and economic value.

[0075] The welding table in the prior art is as follows Fig.13As shown, two electromagnets are fixedly installed on the base frame, and the two electromagnets are arranged at intervals to reserve a weld between the two coated steel plates. In order to make this welding table meet the effect of adjusting the height of the two coated steel plates required in the welding method of the present invention, a lifting device, such as a cylinder, a ruler, etc., can be installed under one of the electromagnets to achieve fine adjustment of -3 to 3 mm in the vertical direction of the electromagnet relative to the other electromagnet, so that one of the electromagnets can drive the coated steel plates to move up and down, so that the upper surfaces of the two coated steel plates are flush.

[0076] The above welding table is suitable for most welding conditions. However, when processing different types of workpieces or using different welding methods, it is necessary to improve some parts of the welding table. In order to facilitate the adjustment of the two coated steel plates, the welding table is more suitable for this welding method. Figure 7 As shown, the welding table includes a table 1, two lifting platforms 2, two electromagnets 3 and a positioning mechanism 4. Two mounting holes 101 are formed through the table 1. The two lifting platforms 2 correspond to the positions of the two mounting holes 101 respectively. The two electromagnets 3 are fixedly arranged on the output ends of the two lifting platforms 2 and are slidably arranged in the two mounting holes 101 respectively. The two coated steel plates are placed on the two electromagnets 3 respectively, and the two coated steel plates are fixed by controlling the power supply of the electromagnets 3; the lifting platform 2 can be lifted and moved, thereby driving the two electromagnets 3 and the coated steel plates to be lifted and lowered, so as to adjust the upper surfaces of the two coated steel plates to the same height position.

[0077] As a preferred embodiment, the lifting platform 2 includes a bottom frame 21, a top frame 22, four connecting rods 23, two sleeves 24 and a bidirectional screw 25. Figure 8 and Fig. 9 As shown, the top frame 22 is parallel to the bottom frame 21 and is arranged at intervals, wherein one end of two connecting rods 23 is rotatably set on the bottom frame 21, and one end of the other two connecting rods 23 is rotatably set on the top frame 22, and the sleeve 24 is rotatably set between the two connecting rods 23, and the two connecting rods 23 connected to the same sleeve 24 are respectively connected to the bottom frame 21 and the top frame 22. The bottom frame 21, the top frame 22 and the two sleeves 24 are used to combine the four connecting rods 23 to form an adjustable diamond-shaped structure, and the bidirectional screw 25 is connected between the two sleeves 24 by threaded cooperation. When the bidirectional screw 25 is rotated, the two sleeves 24 can be driven to move toward or away from each other, thereby driving the top frame 22 to rise and fall.

[0078] The electromagnet 3 may also be configured to be cylindrical as shown in the figure, or may be configured to be a cuboid, without any specific limitation. Of course, the top frame 22 may not be provided, but the electromagnet 3 may directly replace the top frame 22 .

[0079] like Fig.10As shown, it is preferred that the end of the connecting rod 23 away from the sleeve 24 is in a gear-like structure, and the two connecting rods 23 connected to the same top frame 22 or the same bottom frame 21 are meshed to improve the lifting stability of the top frame 22; similarly, Fig. 9 As shown, two sets of connecting rods 23, sleeves 24 and bidirectional screws 25 can be arranged between each bottom frame 21 and top frame 22, and the two bidirectional screws 25 can be linked by sprockets and chains.

[0080] The positioning mechanism 4 is used to position the coated steel plate. The positioning mechanism 4 includes a slide rail 41, a slide seat 42, a guide rail 43, a bidirectional screw rod 44, two scale frames 45 and two metal springs 46. The slide rail 41 is fixedly arranged on the table 1, and the slide seat 42 is slidably arranged on the slide rail 41. There are two slide seats 42 and two slide rails 41, and the two slide seats 42 correspond to the two slide rails 41 one by one. The guide rail 43 is fixedly arranged between the two slide seats 42, and the bidirectional screw rod 44 is rotatably arranged between the two slide seats 42. The scale frame 45 is provided with a plurality of metal springs 46. The frame 45 is connected to the bidirectional screw rod 44 by threaded fitting and is slidably set on the guide rail 43. The two scale frames 45 are symmetrically set about the center line of the table 1. The scale frames 45 are provided with scales or pointers. By rotating the bidirectional screw rod 44, the scales or pointers on the two scale frames 45 can be moved to the weld gap between the two coated steel plates. Then, by sliding the slide 42, it is possible to measure whether the welding edges of the two coated steel plates are flush with the welding direction, thereby helping to improve the welding quality of the weld.

[0081] like Fig.12 As shown, a plurality of tooth grooves 401 are provided on the slide rail 41, and metal spring sheets 46 are respectively fixedly arranged at both ends of the slide seat 42 and engaged with one of the tooth grooves 401, thereby preventing the slide seat 42 from sliding arbitrarily. When the slide seat 42 needs to slide, the metal spring sheet 46 is bent to separate it from the tooth groove 401.

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for welding coated steel plates having different thicknesses, characterized in that: The following steps are involved: S1, fixing two coated steel plates of different thicknesses on a welding table so that their welding positions are parallel and spaced apart to form a weld gap; S2, adjusting the heights of the two coated steel plates so that their upper surfaces are flush with each other; S3, during laser welding, fill the weld with welding wire, move the laser welding head to the top of the middle of the weld gap, and make the laser welding head perpendicular to the two coated steel plates; S4, starting the laser welding equipment, allowing the laser welding head to translate along the length direction of the weld gap, and blowing a protective gas into the weld gap to generate a weld in the weld gap.

2. The welding method for coated steel plates with different thicknesses according to claim 1, characterized in that: In step S1, the welding table comprises a table (1), two lifting tables (2) and two electromagnets (3), wherein: The table (1) is provided with two mounting holes (101); The two electromagnets (3) are respectively fixedly arranged on the output ends of the two lifting platforms (2), and are respectively slidably arranged in the two mounting holes (101).

3. The welding method for coated steel plates with different thicknesses according to claim 2, characterized in that: The welding table further comprises a positioning mechanism (4), wherein the positioning mechanism (4) comprises a slide rail (41), a slide seat (42), a guide rail (43), a bidirectional screw rod (44) and two scale frames (45), wherein: The slide rail (41) is fixedly arranged on the table (1); The slide seat (42) is slidably arranged on the slide rail (41), two slide seats (42) and two slide rails (41) are each provided, and the two slide seats (42) and the two slide rails (41) correspond one to one; The guide rail (43) is fixedly arranged between the two slide seats (42); The bidirectional screw rod (44) is rotatably arranged between the two slide seats (42); The scale frame (45) is connected to the bidirectional screw rod (44) by threaded engagement and is slidably arranged on the guide rail (43), and the two scale frames (45) are symmetrically arranged about the center line of the table (1).

4. The welding method for coated steel plates with different thicknesses according to claim 3, characterized in that: The positioning mechanism (4) further comprises two metal spring sheets (46), wherein the metal spring sheets (46) are respectively fixedly arranged at two ends of the slide seat (42); The slide rail (41) is provided with a plurality of tooth grooves (401), and the metal spring sheet (46) is engaged with one of the tooth grooves (401).

5. The welding method for coated steel plates with different thicknesses according to claim 1, characterized in that: In step S3, the specification of the welding wire is selected according to the width of the weld gap and the structural strength of the two coated steel plates.

6. The welding method for coated steel plates with different thicknesses according to claim 5, characterized in that: The structural strength of the welding wire is greater than or equal to the structural strength of the two coated steel plates.

7. The welding method for coated steel plates with different thicknesses according to claim 1, characterized in that: The coated steel plate comprises a base steel plate (100) and an aluminum-silicon coating (200), wherein the aluminum-silicon coating (200) is coated on the surface of the base steel plate (100).

8. The welding method for coated steel plates with different thicknesses according to claim 1, characterized in that: In step S4, the protective gas includes carbon dioxide and nitrogen.

9. The welding method for coated steel plates with different thicknesses according to claim 2, characterized in that: The lifting platform (2) comprises a bottom frame (21), a top frame (22), four connecting rods (23), two sleeves (24) and a bidirectional screw (25), wherein: The top frame (22) and the bottom frame (21) are arranged parallel to and spaced apart from each other; One end of two of the connecting rods (23) is rotatably disposed on the bottom frame (21), and one end of the other two of the connecting rods (23) is rotatably disposed on the top frame (22); The sleeve (24) is rotatably arranged between the two connecting rods (23), and the two connecting rods (23) connected to the same sleeve (24) are respectively connected to the bottom frame (21) and the top frame (22); The bidirectional screw (25) is connected between the two sleeves (24) by threaded engagement.

10. The welding method for coated steel plates with different thicknesses according to claim 9, characterized in that: One end of the connecting rod (23) away from the sleeve (24) is in a gear-like structure, and is meshed with two connecting rods (23) connected to the same top frame (22) or the same bottom frame (21).

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